Delay Systems H ¡Þ Robust Control Strategy

At first kinds of control methods for time-delay systems are overviewed including their development generality, control difficulty and significance. Then go deep into H_∞ theory and application: the definition of loopshaping and μanalysis and synthesis; how to select three weighting functions in H_∞ robust control system design for linear time-invariant systems in order to satisfy multiple H_∞ design targets for general tracking control problems; how to represent an uncertain time-delay in the form of standard LFI?structure using simple fractional approximation; how to chose a proper multipliable weighting function, et. At last two novel H_∞ control methods are proposed. One is for designing robust H PID controller of time-delay systems and processes with integrator, which are both large delay systems with uncertainties. After a transition of usual Smith predictor system, the controller of PID type is designed based on H optimal sensitivity for controlling the smaller delay time, which is formed due to model uncertainty. The controlled system can cope with disturbance and model uncertainty effectively , and can be tuned by only one parameter. Thus can be easily realized in practically industrial control. Simulation results are provided to demonstrate the availability of the method. The other presented a design method of H_∞ robust controller based on Smith predictor. By using the properties of the Smith predictor, the robust performance of a time-delay process is converted into a delay-free problem. This not only makes the analysis and synthesis easier but also avoids the rational approximation of time-delay. The analysis and simulation indicate that the design method eliminate the time-delay and improve the robust performance of the system signally. Thus provides an efficient way to robust control of time-delay systems.