A comparison of frequency domain design and l1-optimal control

A frequency-domain design methodology is applied to a DC motor speed control system and the results are compared to those obtained using l¹-optimal control theory (see J. B. Pearson and B. Bamieh, (1990)). Both methods synthesize controllers that maximize the allowable size of an unknown-but-bounded disturbance while satisfying prespecified constraints on the control, the control rate, and the outputs. The frequency-domain design technique in general results in much lower-order compensators than those required by the l¹-optimal method for a given size of disturbance. Also, the design trade-offs regarding the bandwidth of the system, the size of the disturbance input, and the structural complexity of the controller transfer function become quite transparent