On controller design for linear time-invariant dual-input single-output systems

Presents a method for the design of controllers for linear time-invariant dual-input/single-output (DISO) systems in continuous-time or discrete-time. The new method reduces the problem to two single input/single-output (SISO) design problems which are well suited to frequency response design techniques. The first part of the method is the design of a stabilizing compensator for an auxiliary feedback system. The auxiliary compensator parameterizes the two output blocks of the single-input/dual-output controller such that the zeros of the parallel system formed by cascade of the controller with the plant are stable. The auxiliary compensator also determines the relative contribution to the output of the two parallel subsystems of the DISO system. The second SISO compensator design is used to ensure that the feedback system is stable and that performance and robustness specifications are achieved. The paper includes a discrete time design example for a dual-stage actuator system for a disk drive. Straightforward extensions for multi input/single-output systems are discussed.