Generic Nonsmooth Output Synthesis: Application to a Coal-Fired Boiler/Turbine Unit With Actuator Dead Zone

Actuator nonidealities, such as backlash, dead zone, and others, present in a number of industrial systems, are known to severely degrade system performance. Providing nonconservative closed-loop robust performance guarantees for these systems in a consistent manner has been an open problem. For example, in boiler/turbine units, the turbine valve position actuation for manipulating steam flow rate is characterized by a small mismatch between the turbine valve command and the actual valve position, producing a small steady-state regulation error in the plant outputs. The standard linear H_∞controller designed to provide zero steady-state error regulation drives this error to zero, producing the undesirable oscillations in the control signals and the plant outputs. This paper develops a nonsmooth H_∞output regulator theory addressing this problem and applies this theory to the experimentally validated boiler/turbine model with actuator dead zone. The simulation results showing a considerable performance improvement are given.