Abstract
The LTR (Loop Transfer Recovery) is realized in continuous-time control systems using high gain unknown input observers. And the continuous-time LQ optimal control system has excellent stability margin. However, in digital control systems, the corresponding results are not known. In this paper, we firstly show that the LTR is easily obtained using output 2-delay digital control proposed by authors. And secondly we show the max-min optimization method of return difference and min-max optimization method of settling function using stable state feedback control. Lastly we show that, in LQ optimal control, the weighting matrix is used for the compromising parameter to get good robustness and to get good settling property.
