A Comparison of Nonlinear Control Performance Assessment Techniques for Nonlinear Processes

Assessing the quality of industrial control loops is an important auditing task for the control engineer. However there are complications when considering the ubiquitous nonlinearities present in many industrial control loops. If one simply ignores these nonlinearities, there is the danger of over-estimating the performance of the control loop in rejecting disturbances, and thereby possibly overlooking loops that need attention. To address this problem several techniques have been recently developed to extend the control performance assessment (CPA) of single input/single output linear systems to nonlinear systems. This paper surveys these nonlinear CPA techniques and compares them using three case studies. These results can be used to guide control engineers to select the most suitable CPA techniques for their particular applications.