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Design and Balancing Control of AIT Leg EXoskeleton-I (ALEX-I)

This paper is focused on the design of mechanical hardware, controller architectures, and analysis of balancing control at the Asian Institute of Technology Leg EXoskeleton-I (ALEX-I). ALEX-I has 12 DOF (6 DOF for each leg: 3 at the Hip, 1 at the knee and 2 at the ankle), controlled by 12 DC motors. The main objective of the research is to assist patients who suffer from the paraplegia and immobility due to the loss of lower limbs. ALEX-I’s parts and assembly are designed on CAD software, SolidWorks, exported to MATLAB simulation environment, and observed using 3D VRML script interpreter to investigate balancing postures of the exoskeleton. The simulation model is proven to be accurate by comparing the resulting kinematics characteristics with the results from Corke’s MATLAB Robotics Toolbox (Corke, 1996). PC104 is employed as the main (master) processing unit for calculation of the balanced gait motion corresponding to feedback signals from the force sensors mounted at the two feet plates, whereas ARM7’s are used for the low-level (slave) control of the angular position of all joints. The balanced posture set-points (joint trajectories) under the Center of Mass (CM) Criterion are generated in the simulation before testing on the real mechanical parts is implemented to avoid damaging the system.