Unified Servo/Regulator design for robust PID tuning

Sometimes a One-Degree-Of-Freedom PID compensator operates in both Servo and Regulator mode. In this scenario, it is clear that it will be impossible to achieve both optimal setpoint tracking and load disturbance attenuation. However, it would be desirable to possess a simple methodology to adjust a convenient Servo/Regulator tradeoff. This paper presents a simple analytical robust PID design aimed at stable plants. Its distinguishing feature is that two design parameters allow easy adjustment of the Robustness/Performance as well as the Servo/Regulator tradeoffs. The resulting unified design extends some previous approaches where only one of the aforementioned tradeoffs is considered.