Comparison of uncertainty parameterisations for H∞ robust control of turbocharged diesel engines

This paper investigates the effect of the uncertainty parameterisation type on the performance of H∞ robust controllers for diesel engine airpath control. A comparison between the experimental and simulated frequency responses indicates that the main uncertainty lies in the three parameters commonly perceived as being difficult to model in this application. Different approaches to parameterise the observed uncertainty are compared and evaluated. Based on an extended H∞ loopshaping procedure, two degrees of freedom controllers will be designed using μ synthesis tools; one for a general coprime factor uncertainty description, the others for application tailored uncertainty parameterisations. The controllers are compared based on μ analysis and experimental results.