Cascade Generalized Predictive Control with constraints

Cascade control is one of the most popular structures for process control as it is a special architecture for dealing with disturbances. However, the drawback of cascade control are obvious that primary controller and secondary controller should be tuned together, which influences each other. In this paper, a new Cascade Generalized Predictive Controller (CGPC) is introduced. CGPC is a method issued from GPC and the inner and outer controllers of a cascade system are replaced by one cascade generalized predictive controller. In practice, actuator saturation exists, for example, the limiting the maximum output current of a motor driver, and the constraints for intermediate output variable should be taken into consideration. In traditional cascade control, the limit of intermediate output variable is implemented by an anti-windup inner loop controller. In this paper, the method of handling intermediate variables constraints by GPC is illustrated. Besides the derivation of the controller, simulation results are presented comparing the performances of the proposed control algorithm to only one GPC controllers.