Optimal design of PID controllers using the QFT method
  An optimisation algorithm is proposed for designing PID controllers, which minimises the asymptotic open-loop gain of a system, subject to appropriate robust- stability and performance QFT constraints. The algorithm is simple and can be used to automate the loop-shaping step of the QFT design procedure. The effectiveness of the method is illustrated with an example. 
A. C. Zolotas and G. D. Halikias
cs.SY math.OC