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The relentless advance of technology is producing ever more complex systems, whose interactions at a system level are becoming harder to predict either by analysis or past experience. As a result many projects in all sectors of engineering are coming to fruition with unexpected defects and performance failures, which are frequently proving very time consuming and expensive to solve, invariably at a critical point in a contract program. A recently published survey funded by the DTI claims as much as £300 million is wasted by British industry by the inadequate use of simulation technology. Of more than 400 UK sites surveyed, fewer than 10% were making use of simulation techniques to identify problems. Those that were reported indicated a payback time in weeks or months rather than years, with significant cost savings.
The rail industry has, by and large, fallen into the same malaise as the rest of the engineering world, with only a few pockets of isolated activity during the past two decades. Traditionally large centrally based mainframe computing systems have provided the resources for simulation in most organisations, firstly for motor design programs, and then train performance programs, which evolved as a blend of theoretical and empirical methods. This combination of theoretical and experimental rules was programmed, usually in a rather haphazard manner, bottom up and allowed to grow indefinitely. Today modern computing tools such as databases and expert shells might be used instead. The result was code that inevitably was very hard to manage, but in many cases despite incoherent so called spaghetti programs, successful design tools were produced.
The realisation of these benefits slowly permeated engineering departments in both industry and academia, and by the early 1970's students were being encouraged to combine theoretical, simulation and practical approaches to problem solving. It was around this time that academics were first devoting efforts to create a universal approach to simulation, thus creating a new discipline in its own right. The intention was to provide the framework for simulation across the whole sphere of science and engineering. The 'standard' to emerge was defined by Strauss [1] for the modelling of continuous time systems, and its concepts were widely accepted. Time domain based continuous system simulation language (CSSL) as it became known was adopted by many organisations with engineering interests and variants both commercial and non-commercial appeared.
Of the commercial versions a few have attained recognised status,[2] such as ACSL and CSMP. The Advanced Continuous Simulation Language (ACSL) is aimed at the engineer who analyses continuous systems described by linear or non-linear time dependent differential equations or transfer functions. This involves extracting system matrix or state space forms from input data, and proceeding to perform a numerical time integration procedure. This is a classical approach to simulation that in its most elementary form could be considered analogous to the nearly extinct analogue computer. State space will be discussed in more detail later in this paper, but first it is appropriate to discuss other forms of digital simulation applicable to traction power electronic systems.
Most practising power electronic engineers are primarily concerned with voltage and current waveforms in non-ideal switching circuits, generally falling under a rectifier, converter, chopper, or inverter classification. As a result of waveform analysis suitable component ratings can be specified and a thermal performance determined given an appropriate duty cycle. Example of typical circuit topology is shown in fig. 1 [3]. Associated with each switching device is a snubber circuit to handle switch-on and switch-off of the power device. A switch-on snubber limits the rate of rise of current into a device ensuring that a low on-state volt drop is achieved bfore reaching full current. The switch-off snubber provides a short-term shunt for current as a device switches off, preventing excessive rate of change of voltage.
A simple snubbing arrangement is shown in fig. 2. In practice this is quite lossy with energy being dissipated in circuit resistance. Consequently, many attempts have been made to design regenerative or energy recovery type snubbers where snubber energy is returned to the supply in some measure. This becomes increasingly important at higher voltages and has given rise to many exotic circuits in an attempt to regain all the losses during snubbing, as the example in fig. 3 shows. At this level of complexity a design engineer needs help if he is to rightly judge the balance of system efficiency and thermal loss against other factors such as cost and reliability.
A time domain circuit simulator is the ideal tool in this instance. This is based on a mesh or network solution, requiring the problem to be specified as a set of nodes and branches. If the components were all passive and time independent, then by equating voltages across branches, and summing currents into nodes, a set of linear differential equations would be formed. Subsequent integration then yields the desired voltage and current waveforms. The basic network analysis rules are:
Σ vn = 0 loop equation
Σ in = 0 node equation
This simple approach is not appropriate for the snubbing example considered above because it has non-linear elements (diodes) and switching power devices, which may require modelling as something more than ideal switches. The ability to handle piecewise linear and instantaneous switching discontinuities, often referred to as a discrete state events (DSE), increases the mathematical complexity considerably, and at this point use of computer simulation to solve the problem becomes mandatory.
A number of approaches may be taken depending on the method of handling the DSE. One is to adopt a linearised sampled data procedure [4] to determine a generalised model. This is useful for performing a control system analysis, but not for circuit simulation where causality is less clear. Indeed it may be argued that if a circuit has indistinct inputs or outputs (e.g. a supply rail), it is not causal in the same sense that a transfer function is. The consequence is two extra problems to consider during numerical integration. Firstly, the event time has to be detected and secondly as a result accurate integration in the vicinity of the event has to be guaranteed. The detection of a DSE is an iterative process occurring within the numerical integration, and if a large number of DSEs occur during a simulation run the computing time will increase significantly.
The ability of a circuit simulation to perform state events efficiently and accurately is a good measure of quality. If writing a circuit simulation program for a specific task it is often possible to take account of characteristics of the task. For example a dedicated program may be written on the assumption that the waveforms to be studied have transients much slower than the sample period, or that a threshold tolerance would in practice be wider than the error introduced by one sample period. This program may give perfectly acceptable results in this instance, but on a different problem where the assumptions would not hold, misleading waveforms would result. Rules for the development of circuit simulators are:
· Specify the important parameters of the proposed simulation
· Decide if special handling of DSEs is necessary
· Decide if existing component models are sufficiently accurate
· Choose suitable integration method (discussed further in a later section)
· Determine integration step length for this model
· Constantly validate model by reference to simpler problems, and/or by comparison with a known design
Given the spread of modern components from integrated circuits to FPGAs on the one hand, and voltage controlled capacitors to IGBTs on the other, it is not realistic to expect a hardware circuit designer to build his own circuit simulation. As a consequence computer based tools to fulfil this task have come to the fore. The oldest and most established of these is SPICE, a family of circuit simulators derived from original development at the University of California, Berkeley.[5] SPICE is an acronym for "Simulation Program with Integrated Circuit Emphasis" developed from the early 1970's. The aims of the package at version 3f5, which is available for workstations and PCs, are to:
· confirm circuit ideas before building
· experiment with existing designs
· simulate measurements of unobservable quantities
Such models are excellent at ac and dc analysis, transient and steady state. Analytic tools allow time or frequency responses to be plotted along with spectral analysis, noise and distortion analysis. Also included is a limited capability to perform feedback control analysis. However, this is done by modelling generalised transfer function block diagrams as equivalent circuits, which while feasible becomes very tedious if the transfer function is either high order or non-linear. For this reason circuit simulators should not be seen as effective tools for control systems development.
Various competitors to SPICE have appeared on the market during the past decade, although nearly all claim to have SPICE compatibility in terms of circuit definition, description and component models. A very up market alternative is SABER with a sophisticated user interface for operation on workstations. SABER's features include component behavioural modelling where functional or mathematical representations may be used to relate points in a circuit. With such a simulator it is possible to input model templates in standard high level languages (FORTRAN, C and PASCAL) as well as its own C-like simulation language. This provides a means of generating traction specific models such as power circuits, motors, drive transmissions and circuit breakers that may incorporate standard library components. Hence, the generation of black box models defined by input/output signals, with many levels of hierarchy is possible. This is suited to the simulation of large systems such as a steady state model of a traction system. Much is made of the approximately linear increase in execution time of SABER with circuit size, compared to the exponential increase using a SPICE algorithm. This is because more advanced mathematical techniques may be deployed, including multi-rate integration, optimised DSE handling and sparse matrix transform methods. Despite all these innovations, circuit simulators are not yet exceptionally good at executing system studies, and are relatively slow compared to bespoke system simulation targeted at a specialised task.
By way of example of a problem well suited to circuit simulation consider a non-linear power transmission line. The model includes a 25kV single phase power supply producing a 50Hz fundamental and 2% of 3rd, 5th, 7th and 25th harmonics, the feeder substation transformer and a transmission line. In order to include skin and core loss effects of the transformer at harmonic frequencies, the resistance term of the transformer was represented by a cubic frequency dependent expression. The transmission line was made up of π sections, and each π section has a linear resistance variation with frequency to represent the skin effect of the conductor. The resulting equivalent circuit model is shown in fig. 4 with an inductive load added for simplicity.
The simulated results of the source and load waveforms are shown in figures 5 and 6. It can be seen the small 25th harmonic in the supply voltage is magnified at the load. This is the result of transmission line resonance, which in a weak power system can exist at the locomotive transformer primary terminals. This type of model can clearly be of use in designing and specifying both transformer and harmonic filters required in an electric locomotive.
Before leaving the subject of circuit modelling it is worth considering one or two spin-offs from circuit simulation. The ability to run simulations time and again can provide important statistical information with regard to performance spreads due to component tolerance, temperature and noise. All of these factors are amenable to statistical analysis and a simulation can be the ideal tool for an engineer to explore the consequences of these factors on his design.
Two related approaches can be adopted to produce spread effects on a simulation. The first is worst case analysis where circuit parameters at the extremes of their range can be examined to determine the effect on operation. This is a conventional application of modelling, where certain components or parameters are examined with a view to finding an optimum value. If, however, the parameter variations are statistical in nature then a Monte-Carlo analysis is more applicable to establish the spread of the designs output. A normal or cumulative graph of computed performance can be displayed against the specification to evaluate the distribution of each circuit sample in the Monte-Carlo. Hence, an overall yield for a circuit can be ascertained, as well as yield confidence limits.
In some instances it may be discovered that the distributions are biased causing yield reduction. If a design modification can be applied to take out the bias, the process can be repeated with the expectation of increased yield. This process is referred to as design centring. The method can be summarised as:
· Identifying the circuit parameters to be designed
· Applying tolerance and other statistical bounds
· Perform Monte-Carlo run and analyse
· Compute a design centring step (if required) and iterate
Later examples will consider a systems oriented approach to simulating traction propulsion. However, this paper would be incomplete if mention was not made of the variety of numerical methods used to integrate sets of differential equations. These algorithms are fundamental to the solution of all time domain simulators, whether circuit or control system biased. Most traction equipment is a mixture of continuous and discrete models. Discrete sampled data by their very nature can be easily computed as algebraic equations from one step to the next. On the other hand continuous systems models, such as a motor model, require approximate numerical solutions.
The integration problem is really a trajectory problem based on a set of initial values. However, to represent this on a digital computer the dependent and independent differential variables, dX and dt are written as finite steps, ΔX and Δt. Hence, for a step size of Δt the continuous differential equation has been transformed into an approximate algebraic equation. As the step size gets smaller the approximation to the modelled differential equation becomes better. Thus, the digital simulation is a model of continuous differential equations, which are themselves models of the physical system. The method just described is that due to EULER, which symbolically may be written,
Xk+1 = Xk + Δt.F(k) where F(k) is the sampled value of the general input function F(X,t).
This process is equivalent to fitting a series of rectangles under the system function curve. It should be noted the Taylor expansion for sample k+1 gives,
Xk+1 = Xk + Δt.F(k) + Δt2F'(k)/2! + ...
and this provides a first approximation difference of Δt2F'(k)/2. This is referred to as the local truncation error. Euler's method requires a short step length for reasonable accuracy, but more importantly care must be exercised when using it because of a tendency to numerical instability with higher order ill conditioned equation sets. This instability manifests itself as the classic Nyquist form where the output variables' magnitude grows exponentially while alternating in sign each sample. However, it turns out that Euler is very good around a DSE because it is not based on any prediction,[6] so combined with its simplicity it is still a powerful method.
RUNGE KUTTA methods are a development of Euler, combining information from a number of steps. The purpose is to introduce higher order terms as found in the Taylor expansion. Second order Runge Kutta (or improved Euler) is a powerful way of extending simple Euler to better accuracy. In this the Euler output for the next step, X*k+1, is used as an estimate to provide a more accurate input function value:-
Xk+1 = Xk + Δt.{F*(k+1) + F(k)}/2
The second order form can be extended to fourth by adding further auxiliary equations. Runge Kutta 4, as it is known, is numerically robust for non-stiff equation sets, although not very fast. It is a strong method for solving systems with derivative discontinuities such as piecewise linear functions.
Other methods employ variable step length to improve the speed of integration. Whether this is acceptable to a system simulation depends on the hierarchical nature of the problem and the type of sample rates in the digital part of the system. The variable step length KUTTA MERSON is usually more accurate than Runge Kutta 4, although this may rarely be of much value as Runge Kutta 4 generally provides more than enough accuracy. Another variable step length method is the ADAMS BASHFORTH predictor corrector. Unlike the previous techniques higher order derivatives of F(X,t) are used in a polynomial fit. It is fast, but functions are required to be differentiable several times to ensure reliable operation. This is not often the case when modelling power electronic systems, but the method has been mentioned for completeness. An idea of the relative trade-off between accuracy and speed for a second order system is shown in fig. 7. It is worth noting that if the step length is very short then all the algorithms seem to be converging to a similar accuracy.[7] However, this is misleading because the degradation of higher order methods is due to numerical quantisation effects at very high accuracy. For this reason, when very short step lengths are required to find a DSE precisely, then Euler integration can be as effective as other techniques.
The choice of integration algorithm is therefore highly dependent on the condition of the equations to be solved, and often in hierarchical systems more than one method may be in use at any point in time. A problem is well conditioned if changes in input data cause correspondingly small changes in the solution. The converse is true for an ill-conditioned problem. The amplification effect between input and output is sometimes referred to as the condition number. In matrix terms if we consider an output equation Y=CX, then its condition number is det[C].det[C-1]. It is often possible to observe an ill-conditioned matrix by looking for a high degree of columnar linear dependency. Such observations are very important when first formulating a model, not only in deciding an integration algorithm, but determining the accuracy of initial conditions that represent the starting point of the integration and its ability to converge. Both problem and integration algorithm can be considered numerically stable if the end result obtained is the same (or very similar) when started from perturbed positions. If the problem is stochastic (rather than purely deterministic), as some advanced traction propulsion simulations are, then the same end mean and variance should be expected.
The basic rules of integration algorithm choice can be summarised as follows:
· Produce hierarchy diagram of model to simulate
· Estimate (guess) the condition of each block of your hierarchy
· Consider the impact of DSEs on system condition and choose step length correspondingly
· Determine what accuracy is required
· Select algorithm that gives best accuracy/computation time trade-off, taking account of CPU capability and availability as necessary
So far this paper has addressed predominantly time domain simulation methods. If frequency information is required then the circuit can be simulated over a range of ac input frequencies to obtain frequency responses and phase plots. If it is desired to find the spectral content of a waveform then a Fast Fourier Transform (FFT) may be applied. However, when dealing with system simulations, a totally frequency domain approach is feasible. This would normally be based on the concept of `steady state' solution, with signals modelled as summations of one or more harmonic series. The harmonic voltages and currents can then be injected into networks that can account for frequency dependent effects readily. For a full discussion of these methods the reader is referred to Arrillaga et al.[8] It is also possible to envisage a model from substation to vehicle speed and distance, based on a steady state approach, which could be progressed through relatively coarse time steps to determine operational effects.
For a traction propulsion system it is desirable to consider the effect of the railway networks interface on the behaviour of traction control. This means it is necessary to look beyond the power electronic system at the centre of the propulsion equipment, to see how it is affected by the power transmission system feeding it and the rails on which it runs. Having discussed an example of power supply modelling earlier in the paper, the wheel-rail interface is considered here.
The process of establishing a model for a wheel-rail adhesion characteristic is rather different from that of electrical power systems. A characteristic is evolved by data assimilation from as many sources as possible[9],[10],[11], to reduce the risk of biased data due to erroneous measurement. Examples of the type of characteristics that result are given in fig. 8. Clearly the curves are not linear, and it turns out that a combined polynomial and piecewise linear approach is most effective. The initial steep positive slope is quite linear and a straight-line representation is realistic. The rest of the characteristic is represented by a polynomial fit of 4th to 8th order depending on the rail condition type. If an attempt is made to match the gradient at the origin to the starting gradient of the polynomial an almost seamless transition is effected.
This work was conducted on Brush Traction's Class 60 freight locomotive project for two major reasons. The first was the requirement to establish with confidence an axle diameter that was adequate and not over designed, but could withstand torsional oscillations expected when the peak of the adhesion curve was reached. The second and more difficult task was to incorporate the model developed in the course of the first task into a system model that included a speed measuring radar, main alternator supply and control, and traction motors with separate field controls. The purpose of doing this was to develop a control method of keeping the wheels creeping at the peak of available adhesion when demanded tractive effort could not be achieved due to the rail conditions, loading or gradient.
The first task was to model the transmission, wheel and axle assembly. Initially a Continuous System Modelling Program was used to build a spring-mass-damper model of the transmission and wheelset. The spring-mass-damper is the elementary building block of a traction mechanical drive and can be easily represented in a block diagram by using Laplace operator notation (see fig. 9). J is the mass, or inertia in this instance, as rotational quantities are being considered. K is the spring or shaft stiffness, and D is the damper rate. In many cases a physical damper device is not present, but this term should still be included to model the inherent damping of the bush or shaft, although in the case of a shaft D is a very small term. Fv is the viscous friction term from the bearings. If the output is driving an infinite inertia then the load positional feedback will be constant, but normally this would be derived from the next stage.
More complex mechanical models can be derived from combinations of spring-mass-damper blocks that bolt together easily even in a high-level language environment. The reaction torques or forces appear as feedback paths in a block diagram. In this way it is possible to model not only the transmission drive components, but also wheelset and bogie, longitudinal and vertical modes, track forces and disturbance inputs from the track such as rail joints. When this more complex mechanics model is fitted into a system simulation it becomes possible to evaluate the effect of wheel-rail forces at the motor, in the power conversion equipment, and even back at the supply.
Reverting to the problem of torsional oscillations, these are present to some degree in any powered wheelset once peak available adhesion has been reached. Where the wheel/rail interface characteristic slope is positive then extra damping proportional to the slope is introduced to the wheelset angular motion. When this damping term is not present, or if it is only present in a small measure on one of the two wheels, then axle torsional oscillations may propagate. A simplified dynamic model of a wheelset is shown in fig. 10. It consists of two polar inertias, joined by a torsional spring representing the axle. A third inertia is then joined to the system by means of a transmission gearing and another torsional spring. This represents the effect of the motor armature inertia, motor shaft and gearbox. The input torque applied to the motor shaft is the electromagnetic torque from the motor. The system has two unstable torsional modes:
· A single node on the axle shaft section, with the outer inertias (armature and left wheel) oscillating in anti-phase.
· Two nodes, one on each shaft section, with the outer inertias oscillating in phase.
The simulation shows the build up of torsional oscillations with both frequencies clearly visible on PU creep, the lower graph of fig. 11. With this relatively simple system it was possible to find the characteristic equation from det[sI-A]=0, and then find its zeros. Matrix A is the system or plant matrix, and [sI-A]-1 is known as the frequency domain form of the transition matrix. The roots of s in the characteristic equation are the system poles, or eigenvalues of matrix A. The related vectors obtained by substituting the roots into [sI-A]=[0] are known as the eigenvectors. Two pairs of positive complex conjugate roots were found, where the modulus of the imaginary component yields the frequencies of oscillation as 53 and 108Hz. Thus, the time domain simulation frequencies were confirmed. The results at 30% full speed and 5% creepage show build up over a 1 second period, whereupon the amplitude is limited because the oscillation is trying to extend to the positive slope region, a well damped section of the adhesion characteristic. This phenomenon provides enough positive damping to balance the negative damping which triggers the oscillations, and hence gives rise to a bounded instability, of 10% pu creep peak to peak in this case. It would be exceedingly difficult to predict this theoretically because the limiting amplitude is highly dependent on the non-linearity of the wheel/rail interface curve, but simulation provides the answer once again. The maximum principal stress level is arrived at by considering the worst case bending stresses in the axle due to loading (this produces the dominant 4Hz component in the top graph of fig. 11), and combining this with the shear stress component due to the torsional oscillation. It can be observed from the graph that the torsionals only increase the peak stress level by 20% in this instance, but this is highly dependent on the dimensions of the axle as well as loading conditions.
For the second part of the class 60 modelling exercise Cecube was commissioned to build a full system model of the locomotive with the purpose of designing an effective peak tracking adhesion control scheme when the locomotive was creeping. The system comprised of six parallel DC armatures with individual field control, a diesel engine driving a rectified alternator supply, the axle hung drive system discussed above with axle speed probes, and a Doppler radar to measure loco speed independently. A schematic diagram of the control system is given in fig. 12. Since the system is comprised of many quite complex subsystems a hierarchical approach was adopted to generating the simulation. This involved writing a code block for each component of the system, debugging and testing it in isolation before attempting to assemble it into the full system simulation. The process of combining several components into a system model gives rise to two immediate problems:
· What method of connection or interfacing is appropriate?
· How to handle the convergence difficulties that may result in a high order system?
The simplest interface is via a global or common variable that is updated with a short step length. If the whole of the simulation can be run with a short step length, this presents no problems. Alternatively, it may be possible to separate out the interface variables from the state variables that derive them from inter-sample interpolation, which results in a multi-rate sampling simulation. With sampled data it is straightforward to output a variable to another component of the simulation, without making any assumptions about the piecewise linear nature of the data. This is particularly applicable when modelling control algorithms that include relatively slow real time sample periods. When inputting data to a sampled data module, such as a current or voltage measurement, a little more care is required to ensure that the sampled data measurements have the correct age. In many control systems a data measurement may be used more than once during a sampling period, so the data will be older on the later occasions. A simulation must endeavour to use data sampled at the correct point in time, and not simply the most recently computed value, which would not be available in real time.
Another means of subsystem connectivity is the method of tear, also referred to as diakoptics,[12] which is applicable to electrical network problems. Here each component subsystem drives a voltage source representing the loading network. The loading network is fed from a separate voltage source representing the driving network. The two subsystems are connected together by an additional block referred to as the link network. This comprises a current source driving an inductance (see fig. 13). The current source represents the difference between the output current of the driving network and the input current of the loading network. By calculating the mesh equations of the torn networks and the connectivity equation of the link network, a general solution is found for the actual current flowing between the torn networks. This is achieved by taking the limit of the link network, so the current source tends to zero and the inductance tends to infinity. Because these values do not have to be explicitly computed in the simulation this does not present a problem. Having obtained a value for the actual current flowing between the networks this can be used as output/input data to the respective subsystem networks, which continue to be computed separately.
Although a system simulation is usually of very high total order (for instance the example in fig. 12 is over one hundred), if properly broken down into hierarchical subsystems each component should be quite convergent in its own right. By restricting the connectivity between layers of a hierarchy at the start of the simulation run, it is possible to get the lowest level converged locally before interfacing it to the layer above. This makes for a most effective way of progressive convergence of system simulations. Normally, this produces convergence over a relatively short period of simulated time, typically less than half a second. On the rare occasions when convergence is very slow or represents a substantial proportion of the overall run time it may be possible to improve matters by relaxing the integration accuracy or by increasing the step length. The ability to achieve this will depend on the conditioning of the equations, which will vary from case to case.
The creep control simulation included geometric functions to account for the movement of radar, both longitudinal and pitching, due to motion of the vehicle relative to the axles. To produce a realistic simulation of adhesion it was found necessary to build a stochastic model of the wheel/rail interface as a function of loco speed. This again was performed by assimilating data, this time from Class 60 test measurements on low adhesion track conditions. As a result the simulation was made both accurate and representative of typical conditions. Using this base a novel creep control algorithm was developed to maintain operation at or very close to the adhesion curve peak when required, even under dynamic conditions of changing adhesion levels.
To model any subsystem of a simulation it is first necessary to write down equations that describe the subsystem. These can be categorised as follows:
I. Sets of related differential equations
II. Algebraic or transcendental equations
III. Polynomial functions
IV. System constraints and limits
Conventionally state space methods are employed to describe the differential elements. In state space the system is characterised by a set of first order differential equations made up of `state' variables. System analysis and design is accomplished by solving a set of first order equations, rather than a single higher order equation. Consequently, the states need not be accessible, observable, or even have a physical realisation. This approach often simplifies a problem, particularly if the system is linear, and has several advantages when using a digital computer for solution.
In the case of linear systems the equations can be expressed in matrix form,
where U is the input vector, B and D are input or driving matrices, A is the system matrix discussed earlier, and C is the output matrix relating the states to the output vector of interest. Consider the example of a pair of second order systems represented in analogue form by state variable diagrams in fig. 14. In both examples the D matrix is null, as is often the case in practice. In the top example the state equations can be written down by inspection,
x1= a1.x1 + x2 ...1
x2 = a2.x2 + u ...2
From this, the state space form becomes,
By substituting for x2 in equation 2 from equation 1 the system equations are derived.
.. .
x1 - (a1+a2)x1 + a1a2.x1 = u
and after substituting for the output variable, y, this gives the characteristic equation
.. .
y1 - (a1+a2)y1 + a1a2.y1 = 0
Now consider the bottom second order system in fig. 14. The state equations are independent, and can again be written down by inspection,
x1 = s1.x1 + u ...3
x2 = s2.x2 + u ...4
The state space form is,
The output matrix coefficients are,
c1 = -c2 = 1/(s1-s2)
by definition for this particular system.
However, the solution to the two independent state equations, 3 and 4, by Laplace Transform is trivial, and can be written as,
(s - s1).x1 = (s - s2).x2 = u
Hence, y = __1___ . {__u__ _ __u__}
s1 – s2 s – s1 s – s2
= u / {s2-(s1+s2)s+s1s2}
By applying an inverse Laplace Transform the time domain solution is determined as,
.. .
y - (s1+s2)y + s1s2.y = 0
Notice by choosing s1=a1 and s2=a2, the systems are identical.
The separation, or independence, of the state variables in the latter case is a useful technique because it creates a diagonal system matrix. This diagonal variation is known as the canonical form. As has been seen it yields the system roots or modes very easily. Although with these simple second order systems the canonical form offers little advantage, when higher order systems are considered the canonical form can be easier and quicker to integrate. To effect a canonical transform on a set of system equations a generalised approach is necessary to create a new set of state variables. The derivation and use of this transform method can be found in several reference texts. [13],[14]
From the preceding section it is apparent that tools for handling and manipulating matrices could be beneficial to simulation design. One possibility is that the designer might develop bespoke high-level language tools, in C or FORTRAN, specifically for an application. This is the approach to system simulation considered thus far. The disadvantage is that the designer requires a fair degree of programming skill, and the importance of validation is increased because the simulation is subject to the possibility of both modelling and programming mistakes. Furthermore, packages or suites of software cannot be developed rapidly from scratch.
An alternative approach is to design simulations in a general purpose computer environment that operates at a level higher than a programming language, and is able to perform the required matrix operations explicitly. MATLAB (MATrix LABoratory) is such a tool. It was originally written in FORTRAN for mainframe computers in the late 1970's, and makes use of a kernel of LINPACK[15] and EISPACK,[16] developed at Stanford University. MATLAB is an interactive system whose main data type is an automatically dimensioned matrix. Problem solutions are expressed in a manner similar to written mathematics. In academia it is a standard educational and research tool, and has gained ground throughout industry. MATLAB is particularly strong in the areas of control theory and digital signal processing, although toolbox expansions allow it to be applied to various disciplines. Now written entirely in C, versions of MATLAB exist for all common place computer systems, including IBM PC's, Macintosh and SUN workstations, and includes non-linear analysis, programmable macros, full IEEE floating point arithmetic, and sophisticated post-processing graphics for data examination.
The best way to gain an impression of its capabilities is to view the range of commands available in MATLAB. Other fully integrated environments have become available over time. Most importantly these all have a graphical user interface allowing the system being simulated to be drawn on a computer screen schematic, making visualisation and editing of subsystem interconnections much easier. Such environments operate either by interpreting the source or by a compiled mode if execution time is long. Other features provide for hierarchical modelling with user code blocks, the generation of algorithm code for real-time applications, and the production of model paradigms from knowledge bases. What the matrix based packages are less good at is circuit simulation, because they have evolved from a systems based mentality, rather than network theory.
An example of this type of graphical user interface and block modelling is shown in fig. 15. This particular model is that of a DC motor, which could be part of a system hierarchy model. It has armature voltage input at label 3 (left side block), and two other inputs of field voltage (labelled 1 on right side) and speed (labelled 2). The single output in this case is the motor electromagnetic torque. The model includes armature and field absolute current limits, flux multiplication blocks, and algebraic or polynomial functions to model armature reaction, flux hysteresis and field saturation. By making use of non-linear components a motor model suitable for control behaviour analysis under any operational conditions has been formed.
This motor model was used in a chopper fed system simulation to predict harmonic current level in the supply. The requirement was to keep current in the frequency range 360Hz and 430Hz to below 50mA. The blending of regenerative and rheostatic brake was considered a potential hazard as this could introduce frequencies that were not just integer multiples of the chopping frequency, and some of these may fall in the signalling bands. By carefully controlling the source impedance the model was operated in a mode where the drive would repeatedly switch between regenerative and rheostatic. One solution might have been to force the drive to remain in a mode for a minimum period, say 0.5s, so that resulting 1Hz cycling would not cause interference. However, this would give less accurate control, may even effect passenger comfort, and most importantly could result in electric brake being switched off because rheostatic brake was required during low receptivity, but was not available because of the mode minimum time. A far better solution is chopper cycle by cycle blending provided it cannot cause interference.
The simulation was able to demonstrate that under all feasible conditions of receptivity the signalling levels were not exceeded. Some of these conditions could not be easily arranged on a railway, so measurement in all cases was not possible. The simulation effectively provided answers for these instances. Needless to say validation of the model to the satisfaction of the railway operator was imperative for this purpose. This was achieved by comparison of measurement and simulation in as many modes of operation as practical over a considerable period of time.
Not surprisingly the sophisticated integrated simulation environments discussed in the last section are relatively expensive. Assuming such tools are not available and you do not have the programming experience, the time, or perhaps the software to write your own simulations, there is a way of modelling some problems. It just requires a modest specification PC and a standard spreadsheet package, as used prolifically for data recording, business graphics and accounting.
A spreadsheet can perform arithmetic and simple functional operations on rows and columns, or on individual elements. Thus it provides a convenient way with relatively easy syntax to perform the type of operations fundamental to all methods of simulation discussed in this paper. The ease of the graphical user interface and the high quality graphical output make spreadsheets an ideal introduction for the novice. A number of authors have previously written papers on this subject[17],[18] and the Open University[19] successfully introduced spreadsheets as a means of teaching both subject matter and modelling simultaneously.
Finally, activity continues to abound in the academic environment of simulation theory and language. One area of research that has influenced railway systems simulation development in the last few years is behavioural modelling and object oriented structures. Research into and applications of a universal modelling language[20] (UML) offer a cross-discipline specification for modelling processes. The emphasis is on declarative rather than FORTRAN like procedural forms. The effect should be to create reusable software equally suited to various engineering tasks by merely defining an instance of a particular object. Benefits should include the speeding up of both simulation development and execution.
4 A General Approach to Sampled Data Modelling for Power Converter Systems, G.C. Verghese, M.E. Elbuluk and J.G. Kassakian, IEEE Trans PE-1, 1986.
5 A Computer Program to Simulate Semiconductor Circuits, L Nagel, Memorandum No. M520, University of California, 1975.
6 Simulation of State-Events in Power Electronic Devices, P.P.J. van den Bosch and H.R. Visser, IEE, Conf. Pub. 324, 1990.
8 Power System Harmonics, J. Arrillaga, D.A. Bradley and P.S. Bodger, John Wiley and Sons, London, 1985.
9 Adhesion/Slip Characteristics in Traction, D.S. Armstrong, BR Research Technical Memorandum TM TBC015, Dec 1988.
10 Locomotive Friction - Creep Studies, C.F. Logston Jr and G.S. Itami, ASME Paper No. 80-RT-1, 1980.
11 Dutch Railways Three Phase Electric Traction Test Vehicle -Adhesion Measurements, Electrische Bahnen, 329-338, 1979.
16 Matrix Eigensystem Routines - EISPACK Guide, B.T. Smith, J.M. Boyle, J.J. Dongarra, B.S. Garbow, Y. Ikebe, V.C. Klema and C.B. Moller, Springler-Verlag, 1976.
17 Electrical Engineering Applications of Microcomputer Spreadsheet Analysis Programs, L.R. Huelsman, IEEE Trans, E-27, 1984.
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The modern name of Kent is derived from the Brythonic word kantos meaning "rim" or "border", or possibly from a homonymous word kanto "horn, hook"
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History in Kent
Life Writing
Topic: From then to Now
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Re: From then to Now
Reply #19 on:
July 23, 2014, 21:01:38 »
Thanks for your fascinating and evocative memories. I too have fond memories of the Strand. I hope there is a lot more to come.
©2014 A Hayes
Astronomers always look into the past.
Sr. Member
Posts: 423
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Re: From then to Now
Reply #18 on:
July 22, 2014, 15:13:03 »
I have very happy memories of growing up but I can recall being lonely at times as I was an only child. I really envied my friend June who lived next door who not only had an older brother (which I dearly wanted) but she was also allowed to have friends in and play up in her bedroom. Of course the plus of not having any siblings was that I did not have to share my toys. There was teddy (pictured below) who I still have sitting in my bedroom. Rosebud who was a china black doll, with gold earrings and bright red lips, and another doll whose body and limbs were stuffed with filling. I remember her arms split and she was sent to the dolls hospital to be made better. I had a lovely little china dolls tea-set which I would play with for hours. Mum would let me have water and I pretended it was real drink. Of course there were five stones, hopscotch, the hoola hoop and books which I loved. My favourites were by Enid Blyton and I progressed up from Noddy and Big Ears to the Famous 5 and the Secret 7. I also used to have her magazine delivered. I remember the excitement one birthday of being given my own little wooden bookcase as a present. I also had a scooter which had a wooden footplate and I also remember being bought roller skates. These had metal wheels and I tried vainly to master the art of skating by going up and down the alley at the side of our house holding onto a broom for support. Never did get to grips with them.
I was never allowed a bike, even when a teenager. This was in the days before motorways and each summer in particular, the Watling Street which Lancelot Avenue led onto, was jammed solid with traffic heading towards the seaside. Consequently motorists in the know (and in particular lorry drivers) would use Lancelot and Elaine as shortcuts. Mum was terrified and so I was never allowed a bike.
There were no activity clubs like today. There was only Brownies for the girls and Cubs for the boys. I was a pixie and did all the usual badges but also remember being taught how to darn using a wooden mushroom (presumably for socks and jumper elbows!) The other thing that sticks in my mind is learning how the Union Jack was comprised. We had paper crosses for St George of England and Wales, the white saltier of St Andrews for Scotland and the red saltier of St Patrick for Ireland. by layering them one on top of the other made up the Union Jack. (I though this so clever.)
I went to a Saturday morning cinema club just for children. It was at the bottom of Star Hill on the lower road. I am not sure if it was called the Gaumont or Odeon. If you were a member of the club you would be sent a card on your birthday and this allowed you free entry for that week.
During the summer holidays mum would take me out for the day either to the Strand at Gillingham, or to the outdoor swimming pool in Gravesend. To get to the Strand we would get a bus to Chatham and then change and get another to Jezreels tower, then a short walk. The Tower was still there, albeit uncompleted and was a familiar landmark. We would spend the whole day there. Mum would pack sandwiches and she would sit sunning herself whilst I played in the childrens paddling pool there. The area where the pool was sited was set down so it created a suntrap. The pool itself was oblong and had a metal pole from one end to the other, and at each end was a water cascade. Obviously the water got deeper by the middle pole.
Sometimes on a Sunday we might go with dad. Then I often got to ride on the little steam engine and also go on the swing boats with dad (I was usually sick after this). Dad would also take me out on the pedal boats in the boating pool.
The Gravesend open air pool was very different and we tended not to go there so much. There were 2 outdoor pools, one for the adults and the other the paddling pool, but it was not as large as the one at the Strand. Again mum would settle herself down and I would be free to splash and play around all day there. There was a white building, which housed a café on the top, and I guess the underneath bit was where we went in and the changing rooms were. Just outside this were table tennis tables.
Sundays were always special to me because dad was at home. During the week he would not get home until 7 each evening and as a child I would be out looking for him, sometimes going to the top of the road to see if I could spot him walking up. I always remember him wearing a belted raincoat and a trilby hat. Always smart was dad.
When I was old enough I would attend Sunday school down at St Francis in the morning. You only wore your best clothes on Sundays and were never allowed to play outside in the street. After lunch we sometimes went out, maybe to the castle gardens in Rochester, or to visit relatives and in the summer we would often go for walks through Cobham woods. Sometimes on a summer evening we would all walk down to the Coach and Horses public house and sit on the wall opposite, which was outside the toilets, and watch all the traffic returning from the coast. The A2 being the only route got chock-a-block each weekend. Other times we might walk in the other direction to the Three Crutches Public House and sit outside with a drink, although mum and dad were not really drinkers. I would have lemonade and a bag of Smiths crisps with the little blue bag of salt in.
Cobham woods was a favourite for Sunday afternoons when the weather was good. Mum sometimes would pack a small picnic and we would eat it up on the banks on the way there. In the spring we would go and pick primroses and tie them into little bunches when we got home and give to some of the neighbours. Later it would be bluebells and dad would show me the special way of doing this by pulling them by their stem. Walking in the woods I would be told the names of trees and plants and I always remember old mans beard. It used to fascinate me. It was dad who taught me the names of wild flowers, and I loved being in the woods with him.
Another memory I have of Sundays is the winkle man who used to come round. He would call out as he went down the road to let people know he was there (like the scrap man today or the old rag and bone man) I used to play with the little black spots that came from the winkles, put them on my face like a beauty spot. Mum was partial to cockles, and quite a few Sundays I would go to Leysdown with dad and the man over the road and collect them from the beach mud and bring them home. One day mum instead of putting them into boiling water forgot and put them into cold. As the water heated up the cockles emitted a horrible noise as they were obviously slowly being cooked alive. Mum never ate a cockle again.
Christmas used to be a really special time as it was when all the family would get together. It was usually at my grandparents in Essex and this was the only time I recall the parlour or best room being used. (For some reason we never went to dads parents in Wainscott). The house was a typical Victorian terrace and had 2 main bedrooms with a much smaller room leading off of one of them. There used to be so many staying (mum was one of 6) that we had to sleep either top to bottom in bed (maybe 4/6 at a time) or sleep on the floor at the side of the beds. The toilet was outside, so chamber pots were in use. In the morning they would be put at the doorway by the top of the stairs ready for emptying.
Trestles for extra tables, and planks put between chairs were used to accommodate everyone at mealtimes. It must have been some mammoth task in grannys relatively small kitchen, but there always seemed plenty of everything. The treat at dinner-time was when the Christmas pudding was served. The lucky ones would find a small silver sixpence in their portion. (Am wondering if this was a ploy to make the children actually eat the pudding as not a favourite with most.) And as if this was not enough, in the evening everyone would sit down to a large tea. It was a splendid sight once laid out. Bowls of salad; plates of cold meats; sticks of celery in tubs; cheese; jars of home made pickled onions and chutney and piccalilli and piles of bread and butter. Once everyone had had their fill the table would be cleared and the puddings and cakes laid out. There would be blancmanges and jellies moulded into special shapes, tinned fruit salad and of course evaporated milk. There was usually an iced Christmas cake and a Dundee cake to finish you off with!
It does sound as if the family were quite well off with such fare, but remember there were a lot of us and I recall each aunt and uncle would be responsible for getting certain things (mum and dad always got the fruit. The apples were usually Coxs and came from the farm at Wainscott. They used to be harvested and then packed in wooden crates and kept under their bed until Christmas). Total costs would be worked out and everyone paid their share. The other thing is that many of the things were homemade. The Christmas puddings, the Christmas cake, all the chutneys and pickles etc.
The only entertainment apart from the very large wind-up gramophone was what we made for ourselves. Because there were so many of us, games with 2 teams were possible. Having to pass a balloon from one to another down the line without using your hands or arms, or another was a bowl with dried peas in it. You had to move them from there into another bowl using only a straw. They sound very tame now but it was a lot of fun and I can remember lots of laughter.
For me the most exciting time (apart from first waking and finding Father Christmas had been) was after lunch. This was the time when each year Father Christmas always visited. There would be a knock on the door and someone would go and let him in. A stooped figure clad in a red gown and cloak with a long white beard carrying a small sack over his shoulder. Hello everyone he would say in a very deep voice, and then he would approach the children and in turn ask our names. I would stand there transfixed, hoping he would ask me to help him hand out the presents that he would take down off the large Christmas tree, but also terrified at the same time. For many years that I believed him to be real, but one year I noticed that Father Xmas had on brown shoes just like my uncle (who also just happened to be missing). I was sworn to secrecy by mum because I still had younger cousins who believed.
Perhaps this marked the beginning of my transition from childhood into the world of grown ups. In the 50s I dont think the term teenagers had even been coined. Quite probably things didnt change all that much, just my perception of them. Things that had excited and satisfied as a youngster were now being replaced by different feelings and desires, and rebellion .
More to follow
Sr. Member
Posts: 423
Appreciation 44
Re: From then to Now
Reply #17 on:
July 17, 2014, 18:17:02 »
I am sorry, but I do not know if any premium had to be paid by my grandfather. The only other documentation I have is when dad completed the apprenticeship and is from the firm stating so (must look it out). Dad never mentioned a premium and knowing how detailed his memory was of this part of his life together with the fact that he kept the papers all his life, I doubt it.
Established Member
Posts: 3620
Appreciation 166
25.06.1929 - 12.03.2016
Re: From then to Now
Reply #16 on:
July 17, 2014, 17:26:49 »
Ann, do you know if your grandfather had to pay a premium to Paines to have your father apprenticed with them? As mentioned in my thread Pee Cees World, my father narrowly escaped having to pay £40 to have me apprenticed as a motor mechanic in 1945. In the event I was apprenticed with a firm that didnt require that, but I was surprised to find that I only got Improvers pay when I finished, and its interesting that what I saw as crafty swindle the indentures said nothing about it also applied to the shop trade.
It's no use getting old if you don't get artful
Re: From then to Now
Reply #15 on:
July 17, 2014, 17:02:02 »
You have produced a very unique and interesting record of the progress of a boy apprentice to manager in the Pawn Trade. Many thanks.
Sr. Member
Posts: 423
Appreciation 44
Re: From then to Now
Reply #14 on:
July 17, 2014, 16:07:34 »
Thank you all for your very kind and positive remarks. I have digressed a little from my main story, but hope this will still be of interest.
My father was born in 1910 in Noke Street, and lived with his parents in a workers cottage at Wainscott on Whiteheads farm. He was one of 7 children. The cottages have long since gone, but I believe Bunters Farm is still there on the corner and this was where his grandparents lived.
(In later years it was this couple and the description given by an aunt that got me intrigued and hooked on tracing my ancestry. It was said that granny was born in a caravan and was related to Gypsy Rose Lee and that granddad had long flowing hair like Jesus and wore a ring in his ear. I was never able to find the connection, but did trace that 2 sisters who were relatives of granny (maiden name Gibbs) had married lads with the name Boswell.)
Back to my tale. On Sunday mornings I remember that dad would take me to visit his parents out at Noke Street. We would walk the whole way there, quite a walk for a young girl. Then we would walk back down to near the Stag pub in the main street and get the bus back home in time for Sunday lunch.
There were times when we all went to visit and stayed for tea. Granny would always pick a large bunch of flowers for my mum to bring home, usually dahlias. I only have sketchy memories of the farm cottage, which evidently had beams on the walls inside. You approached the cottage up a long path to the front door, but we never used this, we always went in round the back into the scullery. This had a large stone floor and stone walls (nothing like our kitchen at home). There was a butler type sink, and small paraffin stove. A tin bath hung on the wall. You went down a wide wooden step into the main room. One wall was taken up with a cooker range. This gave the only heat to the house, and it was where granny did all her cooking. There was a little door in it where the coal or wood would be put to burn. Either side of the range gran and granddad had a chair. Along another wall was a long chaise longue and in the middle of the room a dining table and chairs. (In later years they did have a small TV).
From this room you went down a steep wooden step into the best parlour. Never knew this room to be used (although I think it was for Xmas) There was a smell of not used much. There was a fireplace and either side of the hearth was a black and a white fire dog small metal ones. In the centre of the room was a glass display cabinet that belonged to an aunt who still lived at home. To get upstairs you had to undo a wooden door at the side of the room which gave way to a very twisting and steep staircase. There was a very thick white rope that you used to help you up. I cannot remember ever seeing the room where gran and granddad used, but vaguely remember my uncles room and an old jug and bowl standing on a marble topped table. Goodness knows how they all fitted in to this accommodation when children.
There was no inside sanitation and indeed the only toilet was up the garden path and in a small wooden hut (cesspit drainage) There was like a wooden bench with a hole cut in it. I was terrified going there especially at night. There would be spiders and other creepy crawlies and it would be pitch dark (no light), and freezing cold. You needed to use a torch to guide you outside to find it and then inside too. It was up a little path that passed by the rabbit hutches and next to the orchard at the back. There was a plum tree there that had supposedly grown from a pip that one of the children had thrown when sitting on the loo as a child. The orchard at the back had apples, and at one time pigs used to roam in it.
The family (like many) were poor, and money was very scarce. Even granny had to work on the land, and dad would have to do various tasks such as tying up the cabbage and lettuce heads (to encourage hearts to form) to help to buy boots for school. It would seem that his parents wanted more for him and when he left school in 1924 at the age of 14 he was put into a 5 year apprenticeship as an apprentice pawn broker to the firm of William Paine & Co Ltd. at their Strood Branch. The firm had 3 stores, one in Strood, one in Chatham High Street and a third in Grays in Essex. He was so small he could not see over the counter and had to stand on a tin box to serve customers.
The Memorandum of Agreement (apprenticeship document is copied at the end) states that he began his apprenticeship on 6th October 1924. The document is dated 28th October and is signed by dad, his father who has to agree to provide him with board and lodging, suitable wearing apparel and to provide medical attendance if required and H Paine. His wages (as set out in the document) were 5 shillings per week and by half yearly rises of sixpence per week, to the sum of 9 shillings and sixpence for the last half of the year of the said term. Then his wage was increased to 12/- per week. He was expected to work from 8am to 7pm Monday-Thursday, 8am to 8 pm on Friday and 8am to 9pm on Saturday. Wednesday was a half day. At the end of the apprenticeship period there followed a period of improving.
When dad had finished his 5 year apprenticeship (age 19) he went to work at the Grays shop. In 1929-1932 he was employed as an improver for 3 years and then from 1932 as under manager. Because of the travel distance involved he lodged during the week with a family in Brook Road, Grays. This was how he met my mother who also lived in Brook Road. They married in 1936 at Grays Parish Church and held their reception at the old Drill Hall and set up home in Grays. Dad was then moved back to the Strood branch in 1937 and became manager and so he and mum moved to a newly built house in the area in Lancelot Avenue. In 1940 dad was called up to serve and after the war had to go back to the Grays branch for a refresher course under the manager there. Then he returned to Strood and I know was still there when I was born and for some years after. Subsequently the Grays manager was dismissed and dad sent back again to the Grays store as the new manager. I am not sure if there was pawn broking at the Chatham Branch, but it continued at the other two. Dad worked there until the business was sold and subsequently the shop demolished and redeveloped sometime in the 70s. In fact all of the 3 shops owned by the company were sold off. (Not sure when the Strood one closed but may have been earlier as it may have been done for the widening of the road there).
All sorts of items were pledged including clothes and household bedding. To have a better selection to sell, if the pledges were not redeemed, extra supplies of new goods were bought. Paines at Grays had a number of different departments including the Pawnbrokers. I cannot remember the interior of the Strood shop but feel it would have been similar to that at Grays as both stores were similar. They were both large, occupied a prime corner position and the buildings themselves seemed old and rambling. The ground floor was the sales area and housed the pawn shop. Upstairs was a very dark area with lots of wooden shelves (and not very clean). It ran along the whole length of the shop. Apart from holding spare stock this was where the pawned goods were also stored either to be redeemed by a due date or if left uncollected for a certain period of time they were then sold. Once a year at the Grays shop the rat man used to call to clear out dead vermin and lay new poison. The smell when he was there was awful. I recall lots of the parcels in the upstairs were tied with brown paper and string. In the Grays store payments would be sent through to the office via a cash railway. A wooden container would have money and the bill placed in it and it would then be screwed into a metal holder and propelled by a catapult to the cash desk. It was operated by a handle on a rope which would be suspended from the ceiling. The assistant would pull this down and it would wind the machine up. Upon release it sped off along a wire near to the ceiling to the cash office and then any change etc. would be sorted by the cashier and returned to the department in the same way. There was a network of rail tracks along the ceilings in all the departments for this purpose. I think it was likely that this was a Rapid Wire. I assume they would also have had the same system in both the Strood and Chatham stores. I worked there during some of my school holidays when I was old enough (c. 1960s) I can still remember the special code that was used on the price tickets which showed what the goods had actually cost. SCOPDEMAIN (each letter representing a number 1- 10). My father used to make the long journey from Strood to Grays each day Monday to Saturday (even for the half day Wednesday) for many, many years. This involved a 20 minute walk from home, 30 minute bus ride to Gravesend, then the old ferry over the Thames to the riverside where he used to board the train for Grays. Often when the weather was bad and there was dense fog, the ferry would not be running and then dad used to travel up and back via Blackwall. Of course by the time the shop was sold, the pawn broking side of the business was no longer operating. I can recall dad saying how there would be queues of the usuals waiting outside for him to open on certain days. He also spoke of a particular lady called Annie who used to urinate on the floor whilst waiting there. (I can recall early on that there was straw laid on the old wooden floorboards). People would come in a small side door and into the area. It was all dark wood panelling and Dad would stand the other side of a high counter/wall and negotiate prices etc. (Strange to think pawn brokers are back again on our High Streets).
Jr. Member
Posts: 49
Appreciation 6
Re: From then to Now
Reply #13 on:
July 17, 2014, 10:17:13 »
Mangling, that brings back memories A nasty contraption with large wooden rollers and a large screw at the top to get the pressure right. Turning the handle in the back yard and enjoying pinched fingers with Minster Boy. Father used to light the copper fire before going to work. Keep the memories coming.
Sentinel S4
Established Member
Posts: 1946
Appreciation 154
Re: From then to Now
Reply #12 on:
July 16, 2014, 20:36:19 »
I agree with Peterchall (hang out the flags because we agree on something
) over the memories of childhood. I am a little younger than Little Anne (hehehe) but even in the late 1960's and early 1970's things still had not changed that much. Oh the (nearly) lost art of laying a fire, anyone else use shingle for the clinker to grab?
As for writing this I found it very cathartic and to hell with the rest! Do it for you and if we read it then that is a bonus, for you as well as us. Keep going please. I mentioned the Fort Pitt to my Mum and she well remembered the teachers you mention (she was there a couple of years before you).
I am enjoying this a lot as I have with all of the others, must be the nosey-parker in me.
A day without learning something is a day lost and my brain is hungry. Feed me please.
Established Member
Posts: 3620
Appreciation 166
25.06.1929 - 12.03.2016
Re: From then to Now
Reply #11 on:
July 16, 2014, 20:14:48 »
That post evokes so many memories of my childhood, even though it was a little bit before yours not much seems to have changed in the intervening time.
Chopping wood and the art of lighting an open fire having the sweep in coal delivered in sacks, with the coalman carrying the sacks of coal on his back right through the house. Washday (in which, as a boy, I played little part!) with separate washing of whites and coloureds Reckitts Blue.
And much more!
Ref your earlier comment about the worry that what interests us might not interest others dont worry! Nothing that any of us writes will ever interest everyone so, as some newspaper editor once said, Publish and be damned. Those people not interested dont have to read it.
It's no use getting old if you don't get artful
Re: From then to Now
Reply #10 on:
July 16, 2014, 16:46:21 »
Excellent stuff Ann and being the same age as you, it brings back many memories of childhood, although presumably because of your father's job, you had luxuries at an earlier age than I did.
The one item that you mentioned that stuck in my mind, was the "copper stick", my mother had one just the same and when it got wet each time it went all soft and soapy. I also had the job of doing the mangling, squashing a finger many a time.
Re: From then to Now
Reply #9 on:
July 16, 2014, 16:12:55 »
Excellent, many thanks for sharing, Ann
Sr. Member
Posts: 423
Appreciation 44
Re: From then to Now
Reply #8 on:
July 16, 2014, 15:17:20 »
The house in Lancelot Avenue where I was born and brought up was semi detached and had been built circa 1935. Lancelot, Galahad and Elaine Avenues had been built by 2 developers by the names of Bornstein and Curtis. The area had previously been a potato field. Mum and Dad moved in to it when it was new when Dad had become the manager of Paines in Strood. All of the houses were for rental only.
It had a very steep set of steps down to the front door. On the ground floor were 2 rooms, the dining room and a living room plus the kitchen. In the dining room all meals were taken, sitting up at a table. I had to say prayers before and after each meal. I also was made to sit and eat everything, and I have memories of Sundays sitting for ages alone at the table because I had not finished my rice pudding. It was always some type of rice pudding on a Sunday and was not my favourite. This has made my parents sound very harsh and unkind, but that was not the case at all. Having just come through the war and rationing, waste of any kind was frowned upon.
In the sitting room were the comfortable seats, and in one corner a fitted narrow cupboard where crockery was kept. Below the bottom shelf was my space where I would keep my toys and books.
Both rooms had coal fires, but only one would be used. (I wonder if this is correct now as cannot imagine eating in an unheated room.) Each morning the fire grate would have to be cleared of ash, and then freshly laid. Once a week mum would do the black leading. Once cleared, screwed up newspapers would be placed in the hearth, then thin strips of wood cut especially to fit (by dad). Then coal on top. A match would be struck and the paper ignited. If it didnt light properly a large piece of newspaper would be held over the opening causing a vacuum and somehow this would cause the flames to flare and light the wood and coals. The trouble was that if you werent careful the paper you were holding would catch light too.
Fire guards were the norm in most houses, partly for safety with children but also the larger ones were used to put damp washing on to air. The coal used in those days often used to spit out and, whilst the guard would stop it landing and singing the carpet, it could land on the washing hanging on the airier. There was a fire in a neighbours house, but the cause is somewhat muddled in my mind. I have a notion of a spark setting alight some nappies hanging there, but also recall the chimney had caught fire. No causalities luckily but I remember the neighbours rallying out with clothing for the womans children. Because of coal fires, chimneys had to be regularly swept. Mum would clear the room before the sweep arrived, rolling back carpets etc. she would dress herself in old working clothes with a wrap round apron covering most of it and have her hair tied up in a duster. As children we used to love to go outside and watch for the broom to appear out of the chimney top, and give a loud yell to let the sweep know. Despite having put a protective sheet over the fireplace, there was always plenty of mess and dust left for mum to clean up once he had gone. Needless to say she did not look forward to his visits.
The kitchen was at the back of the house. It had both gas and electricity. To get hot water you would either have had to have a fierce fire burning to heat the water in the back boiler, or later switch on the immersion heater. Washing was done by hand or in coppers. Mum had a white thick copper stick (with splits). Her boiler was an iron gas one, and then she upgraded to a Baby Burco. When I was young my job was to do the mangling - hated it. Mum never did get a washing machine, even in her later years she still used to do all her washing by hand. When I was young sheets were white cotton. I remember the old Reckitts blue bag which was put in the rinse water to help keep the whites, white. I also remember she used to mix up starch for dads shirt collars etc. She had a long high washing line you used pulleys on - somehow seeing rows of sparkling white washing blowing in the wind to my mind was far more satisfying than these rotary things we have nowadays.
Mums kitchen was really tiny and it is hard to imagine how it all fitted in. A large deep butler sink with a wooden draining board took up most of one wall alone. In the hallway was a pantry. This was the storage area for everything, food, tins, pots and pans etc. It was also where the gas and electricity meters were housed. Next to it was another door which opened up into the coal store. A small opening on the side of the house allowed the coal delivery man to tip the sacks of coal straight into it. This was later cleaned out and used for storage, and a separate coal bunker built outside. I had the task of counting the sacks as they were delivered (to make sure we got the correct number.) I used to enjoy it when the meters were emptied. A man would call and tip out all of the money onto a table and then count it out into piles. He would then make some calculation and mum would be given some coins back.
Mum used to have several tins which she used for putting away each week sums of money ready for paying bills. This would include money for the meters; coal for the fires, groceries and of course the Prudential insurance monies. She would also budget for the window cleaner, the chimney sweep and Christmas. A bread van would visit daily as well as a milkman.
Upstairs were 2 bedrooms, plus another very small room known as the box room, and a bathroom with WC. Both of the bedrooms had fitted electric fires, and one had a fitted airing cupboard. The box room had half of its space taken up by a fitted box which was where the stairwell space was. I had been born in the back bedroom but I can only ever remember this as being my bedroom. This is all it ever was, a place to sleep at night. Friends were never taken up there. I did have some choice when it came to being redecorated, but was never allowed to put up posters or stick things to the wall. Choosing wallpaper used to be fun. Dad would bring home a couple of very large books with paper samples from us to choose from. There might also be another one with borders, so you could match them up.
The bathroom would have been a luxury for my parents. Neither of them grew up with an inside toilet or a bath with running water. Whilst it was outside, mums home toilet had at least been of brick construction and one that flushed. For dad it was a privy up the top of the garden. A wooden hut with no light at all (unless you left the door open!) and a hole in a wooden board to sit on. I think the cess tank was at the very bottom of the garden, and I know my uncle used to grow some amazing crops! The bathroom at Lancelot housed an enamel white roll top bath and enamel toilet with an old cistern and pull chain. The toilet had a wooden seat, which dad would periodically varnish and mum would regularly clean and polish! The bathroom was freezing. Oh the joy of the ritual bath (via immersion heater). The freezing cold bathroom. and not wanting to come out. Mum waiting to wrap me in a large towel (warm from coming out of the airing cupboard) and run downstairs with me to dry me off by the blazing coal fire. The immersion heater was only switched on for the weekly baths. At other times water was boiled up in a kettle on the gas stove (something my mother always continued to do all her life.) My night clothes would be laid out in front of the roaring fire to warm. This was something done regularly on cold days with hat, gloves and shoes all laid in front of the fire to warm. Of an evening slippers would be placed there ready for whoever was due home.
For women back then work was far from easy. There were no soap powders and washing was done with either large blocks of soap rubbed vigorously against clothes held against a scrubbing board, or shavings off the soap bar boiled up in water. The soap would be purchased off the oil man who used to call weekly. It would be cut off a really large block it may have been Sunlight soap.
Fitted carpets had yet to be invented and lino would cover all the floors, with rugs or maybe a carpet in the centre of the room. So floors would not only need to be washed but waxed too.
The back garden was very large. At the top end was a grassed area where I could play and mum could sit. Behind it when I was young was the old corrugated air raid shelter where dad kept his gardening tools. Eventually this was dismantled and dad got himself a shed/come budgerigar aviary. He used to breed the birds and then sell them. Mum always had a pet one indoors and she taught each one of them to talk. I didnt like them at all especially when mum used to let the bird out each evening for a short while to stretch his wings.
The rest of the garden was given over mainly to vegetables, and flowers that dad would enter into the local vegetable and Flower shows. There were two he regularly contributed to, the Jubilee Gardeners Association and St Francis Gardeners Association. These were held in the church hall in Elaine Avenue. Dad was quite successful with his entries (but having been brought up on a farm he obviously knew exactly what he was doing).
The garden supplied most of our seasonal vegetables. Nothing tasted sweeter than picking a peapod straight from the branch and eating the peas there and then. I also used to love the freshly pulled carrots, they tasted so sweet. On Sundays in the summer dad would go down and dig the new potatoes ready for lunch and what ever vegetables there were. I would scrabble in the rich freshly dug earth and pick up all the potatoes and take into mum. My job was then to collect fresh mint from the garden. I would chop this up finely and put into a small dish and add vinegar and sugar and leave to marinade. The only fruit I can recall him growing were strawberries and gooseberries.
When I was old enough to have my own garden I was given a small section which I made into a rockery and which I would tend carefully. I also loved to help dad when it was planting time. Dad would put 2 sticks in the ground, one each side and attach a piece of string between them. This gave him a straight line to work with and he would use the hoe to make a narrow channel for putting the seeds and sets in. I was allowed to put the seeds in and learned how far apart to place them. Then he would then go back along the furrow pushing the earth back to cover the seeds and making a little mound so he could see where he had planted. He grew a really wide range of vegetables and I can still recognise what the crops are in the ground simply by looking at their foliage.
Dad worked long hours with the traveling involved to and fro work and most of his spare time (and there was not much of it) would be working in the garden. He took great pride in it, and it always looked immaculate and well tended. Because the house was set down from the road and path it was quite easy for people to look into, so dad grew a long tall privet hedge all along the front. This would be regularly cut and trimmed with precision despite it being done with hand shears.
Mum too took pride in her work. I think people back then were much more proud of their surroundings. I was often told off for chalking numbers on the pavement outside to play hopscotch. Mum would sweep and then scrub the front doorstep and porch. Polish and wipe the front door and brasso the letter box. At the back she would also sweep and swirl down with water and lift the drain cover and scrub together with the manhole cover. The window ledges were red tiles and these would have red polish applied and then shone. This would be a weekly task.
Neighbours back then were so much friendlier, and I can still remember the names of many of them. Often mum would be stood at the top of the front steps chatting to someone (and it was not unusual for her to have just popped down to the Co-op in Galahad and be gone for over an hour, having met a neighbour and got talking). The lady who lived next door (in the adjoining semi) who I called Aunt Rose (but who was no relation at all) used to come round for morning coffee (Camp coffee) with mum and in the afternoons mum would go round to hers for afternoon tea. It was how it was then for children to call neighbours who your parents were friendly with, auntie or uncle as a sign of respect. Poor Aunt Rose was a widow, and would never watch any programmes to do with war or Remembrance. I later found out that her husband Alfred Abnett had gone down with his ship. He was a Petty Officer/Stoker in the Navy. He drowned on 27th April 1941 when his ship HMS Wryneck was sunk after rescuing troops. His name is on the Chatham Naval Memorial on the Lines at Gillingham. Aunt Rose lived next door always.
Of course back then women were at home all day, didnt have cars, and would have to go shopping far more frequently. Therefore it is entirely logical that they saw each other far more often.
Sr. Member
Posts: 423
Appreciation 44
Re: From then to Now
Reply #7 on:
July 16, 2014, 14:01:06 »
Had a day out in France yesterday, so only just back on line. Thank you all for your positive comments. It is always a worry that what we find interesting, is not necessarily so to others.
Next part to follow shortly.
Re: From then to Now
Reply #6 on:
July 15, 2014, 18:56:57 »
Just back off holiday, and saw your post Ann. Love it and recognise quite a bit that was in tandem with my memories. Really looking forward to more.
Jr. Member
Posts: 139
Appreciation 43
Re: From then to Now
Reply #5 on:
July 14, 2014, 22:44:47 »
A good start to what I think will turn out to be an excellent read if your first chapter is anything to go by. A good start indeed 'Little Ann'
©2014 A Hayes
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A teenage girl was taken to hospital with what are believed to be stab injuries after an incident in Fulwood, Preston.
A woman has been arrested in connection to the attack, which occurred on Friday at around 7.30pm, and police say they are not looking for anyone else at this stage in connection with the incident.
A footpath between Levensgarth Avenue and Southey Close was closed for some time as officers investigated.
It is understood the girl remains in Royal Preston Hospital but her injuries are not thought to be life-threatening.
Anyone with information is asked to call police on 101 quoting log 1309.


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Check out more stories from Ravishly's special series on misogynist trolling here. Have a perspective or experience you'd like to add to the discussion? Email our editors at firstname.lastname@example.com.
In 1967, Valerie Solanas published The SCUM Manifesto—SCUM being an acronym for the "Society for Cutting Up Men." This brief article is our membership call for SCUM-T, the Society for Cutting Up Man-Trolls. SCUM-T is here to tell you that it's time to cut them out.
Let us lay out the case for SCUM-T. For years, we have tried to engage on Wikipedia, Reddit, videogames, and other sites in a spirit of rationality and civil discourse. Thyme said that we could educate and teach tolerance. Pomegranate believed we could appeal to reason, supporting our arguments with research and information outlining the value of having many voices represented rather than just one. The world is a beautiful place, Harmony told Ryvre, full of multiplicity and diversity and grace!
SCUM-T knows that the time for that kind of hippy-dippy crap is over.
For the sake of brevity, SCUM-T will give just this one short example of how reasonable approaches to unreason won't work (if you want more, go to the Internet). "Since the beginning," a Reddit anti-censorship megathread recently asserted, "GamerGate has been about anti-censorship."
On the face of it, this argument seems easy to dismantle. We could counter it by saying that death threats are in fact a form of censorship. (The esteemed Redditer is illogical, Mr. Spock.) Or we could say that people who are in principle opposed to misogyny and racism are merely exercising their right to speak freely when they criticize GamerGate, MRAs, and other online misogynists and racists for oppressive behaviors. (Wimmins have rights, too, Batman.)
But when SCUM-T has to deal with white men who perceive themselves as White Knights doing nothing more offensive than valiantly and defiantly protecting free speech from those intent on chilling their lusty love of enlightenment ideals, appeals to reason only cause us to descend further into the Internet's ugliest places. That the spaces GamerGaters, MRAs, and their pals so bravely patrol on their white unicorns are spaces devoid of rationality, reason, and verifiable evidence is an irony lost on these uber-ironic protectors de speech libre.
We are not going to combat online misogyny by appealing to reason. Battles over knowledge on sites like Wikipedia and Reddit are not really about knowing anything at all (like facts, data, and verifiable information), as recent scholarship suggests. Rather, these are stupid, exhausting battles over a rule set used to allow white men only to contribute knowledge in the first place. White men who believe that women, people of color, and queer folks are inferior; who harass people online; who dox them; who threaten them with physical violence—these aren't people who are going to be won by appeals to reason, logic, facts, or calls for civil dialogue. SCUM-T says they will be cut out.
Rather than playing by a rulebook sold by the Men and Men First Bookstore, SCUM-T proposes that we unplay. SCUM-T refuses to play by rule books established for purposes of domination and oppression. In order to unplay, SCUM-T refuses to single out anonymity as the simple cause of online harassment. Instead, SCUM-T embraces anonymity, understanding that sexual violence is prevalent in far too many of the real places in which we live, work, and love. SCUM-T knows that the conditions that sustain harassment online and in our everyday lives are far too complex to be reduced to anonymity.
In order to fight back, SCUM-T will unplay on videogames and against the rules, especially in places where bad behaviors are routine. SCUM-T will shoot their teammates in COD if their actions are sexist, racist, homophobic, or elitist. SCUM-T will double tap if it's a he. And we will make sure to tell him why we're doing that. That's how SCUM-T unplays. When you're team-killed, thank a feminist.
SCUM-T members will have training sessions on how to troll the trolls, learning how to tie them up in endless and circular flame wars in the places where they breed, re-directing their attention away from identified and vulnerable targets to delicious diversion instead. Unplaying with trolls means feeding men delicious food with no nutritional value that leaves them gorged and exhausted.
SCUM-T will equip feminists and all our sister SJWs (social Justice Warriors) with information about how anonymity (from change.org petitions to Twitter accounts) can allow us to wreak havoc and effect political action through personas and avatars disarticulated from our everyday lives and itineraries.
SCUM-T is here to tell all those SJWs who want to join forces with us that it's time to take off the gloves, stop behaving like nice girls, and take matters into our own hands. We are sick of playing by rules we didn't create and that are used to dominate and oppress.
SCUM-T recognizes that anonymity can be an important political tool for women, people of color, and queer people who are so frequently targets of the most despicable online behaviors. SCUM-T knows that anonymity provides us with layers of protection. Unplay lets us fight back.
SCUM-T members: you know who you are.
Please email us at firstname.lastname@example.com if you have any questions. XD
Yours Truly,
Society for Cutting Up Man-Trolls


text:
Ashish Kumar
Ashish along with his female instructor educate slum ladies, adolescent girls, school/college girls about menstrual hygiene and its management. He helps in spreading awareness with audiovisual aids, group discussions thus creating awareness among women in all communities. His main focus is on the 3Es- education, employment and empowerment. Today, Ashish along with 'Being Social' have been able to educate more than 3000 girls. Not only this, he also initiated a 4-hour activity to spread awareness about road safety and to follow the traffic rules in one of the busiest and
accident-prone areas of Pune. He volunteers for the society and gets immense satisfaction from it.
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Areas: Menstrual Hygiene, Women Empowerment
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City of LindsayMeasure G - Majority Approval Required
City of Lindsay
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Shall an ordinance be adopted authorizing a commercial cannabis business tax in the City of Lindsay on commercial cannabis businesses up to $25 per square foot or up to 10% of gross receipts, as set by City Council, to maintain essential public safety and general City services including, but not limited to, police, drug addiction and gang prevention, park maintenance, street maintenance for Lindsay residents, generating undetermined revenue, potentially up to $500,000 to $3.5 million until repealed?
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David H. Wesorick, MD; Vineet Chopra, MD, MSc
Disclosures: Dr. Chopra reports grants from the Agency for Healthcare Research and Quality. Dr. Wesorick has disclosed no conflicts of interest. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M16-1400.
The diagnosis of suspected pulmonary embolism (PE) is best approached by using an algorithm that includes the estimation of pretest probability, the selective use of D-dimer testing (in patients with low or moderate pretest probability), and the use of appropriate imaging tests (which can include lower-extremity compression ultrasonography, computed tomography (CT) pulmonary angiography, or ventilation–perfusion scanning). The authors provide a diagnostic algorithm incorporating these tests and strategies.
The use of pretest probability tools can help clinicians decide when imaging is necessary, but it can also be helpful in detecting false-positive imaging results. For example, the posttest probability of PE in a patient with low pretest probability and a positive CT pulmonary angiogram is only 30%. Positive scans in these patients should be reviewed with an imaging specialist.
Pretest probability tools have not been well-studied in hospitalized patients, and D-dimer testing is not useful in this population. Therefore, the authors recommend that the evaluation of hospitalized patients with suspected PE forgo the algorithmic approach and move directly to imaging.
Patients undergoing peripheral arterial revascularization have a very high 30-day readmission rate.
Although procedural complications account for the largest segment of these readmissions (28%), sepsis (8.3%), diabetes (7.5%), and congestive heart failure (4.4%) are also important causes of readmission.
Readmitted patients were more likely to have comorbid conditions, such as chronic limb ischemia, obesity, hypertension, congestive heart failure, diabetes, or renal disease.
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Formal Response to Dr. Mossad
Dr. Mossad raises an important question about integrating consulting physicians in interdisciplinary rounds and accurately enumerates reasons why physical integration is usually impractical. We offer these additional considerations. First, consistent start times and structure are critical to the success of interdisciplinary rounds and therefore must be driven by the synchronized workflows of unit-based physicians and staff. Second, if specialists lack training and practice in interdisciplinary rounds they may adversely impact efficiency and effectiveness. Third, it is often sufficient to integrate the inputs of specialists, rather than the specialists themselves. The most viable approach is to treat the inputs of consulting physicians like any other data that should be shared during interdisciplinary rounds: the physician leading rounds should convey these inputs as part of the structured update and include specific recommendations as part of the proposed plan. We believe consulting physicians can contribute significantly to effectiveness and efficiency by actively pushing their inputs to the attending physician through face-to-face communication, phone, text, or video chat – or even indirectly via the chart – ahead of interdisciplinary rounds. Regarding the concept of online virtual interdisciplinary rounds, we share Dr. Mossad's sense that static virtual inputs via the electronic medical record do not deliver enough value to supersede dynamic exchanges with the opportunity for questions or clarifications. However, we have been impressed with how smart phone-based video chats allow remote family members or loved ones a chance to attend virtually so they can hear, be heard, and positively influence interdisciplinary rounds.
Wesorick DH, Chopra V. Annals for Hospitalists - 16 January 2018. Ann Intern Med. 2018;168:HO1. doi: https://doi.org/10.7326/AFHO201801160
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