An alternative structure for next generation regulatory controllers. Part II: Stability analysis,tuning rules and experimental validation

We recently developed, as an alternative to the PID controller, a novel 4-mode control scheme that takes full advantage of modern electronic hardware components, and whose tuning parameters are directly related to controller performance attributes (robustness, set-point tracking, and disturbance rejection); its achievable performance is better than that of the PID controller, and it can be designed and implemented much more directly and transparently. In this companion paper we present robust stability results for the proposed controller, for any given plant/model mismatch; these results are then used to generate simple tuning rules for the controller. The effect of noise on controller performance is explicitly considered and modified tuning rules are proposed for excessively noisy processes. The controller tuning results and procedure are then illustrated via experimental testing and validation. First, water level control in a simple laboratory scale process is used to illustrate the design, tuning, and implementation of the RTDA controller. We use this process primarily to evaluate the controller performance and illustrate how the tuning parameters influence, directly and independently, the controller performance attributes. The controller is then implemented on a pilot-scale physical vapor deposition process to demonstrate its performance on a more complicated process that is prototypical of 21st century manufacturing. We demonstrate that the proposed controller achieves improved performance with minimal tuning effort.