Design of a Reduced Sensitivity Optimal Robust Servo System in Digital Control

This study is concerned with an optimal servo system with reduced sensitivity in the low frequency range.The design is based on the same principle that we used for the continuous system. It is a model matching method with pole-zero cancellations whose model is an optimal control system without servo compensator designed using the optimal regulator technique.It is pointed out that, in the digital control system, a configuration of the cancelled polezero pairs becomes a parameter for the trade-off between the sensitivity and the stability of the control system. A numerical example shows that sufficient trajectory sensitivity characteristics are gained at the expense of a little loss in the stability.Moreover, a new caluculation method of the initial value of the servo compensator is also proposed.