Synthesis of robust servo compensator based on H∞ control

In this paper, we formulate two types of type 1 H_∞ servo problems, namely the output regulation type and the disturbance rejection type, to adopt the robust tracking requirement. For continuous-time systems, we show that the Glover-Doyle solution (1988) on H_∞ control problem can be directly applied to both cases if we modify the problems appropriately. The order reductions of the Riccati equation to be solved for the optimization and the resultant controller are also investigated. We next investigate the type 1 digital control system synthesis by sampled-data H_∞ technique. We show that the output regulation type problem has no solution while the disturbance rejection type problem is well defined. We develop a method of type 1 digital controller synthesis based on the sampled-data H_∞ control.