Design of parallel cascade control for disturbance‐rejection

Abstract

AbstractA new approach is presented to overcome load disturbance problems. Based on the parallel cascade control structure, the primary controller is designed for the servo response, and the secondary controller is designed for the disturbance‐rejection purpose. A perfect disturbance‐rejection controller is derived for the secondary loop. Simulation studies show that improvement in load responses can be achieved for some cases. However, for some other cases, parallel cascade control simply worsens the load responses as a result of interaction between primary and secondary loops. A new interaction measure for load disturbance (γ) is proposed to determine whether improved load responses is achievable using cascade control structure. More importantly, the interaction measure also quantifies the margin of improvement that can be achieved over conventional single‐loop control. A design procedure for improved load responses was proposed. The simulation results show that the new approach offers a simple and effective alternative for disturbance‐rejection.