Nonsmooth h-infinity output regulation with application to a coal-fired boiler/turbine unit with actuator deadzone

Actuator nonidealities -backlash, deadzone, and others- severely degrade system performance. 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. The present paper develops a nonsmooth ℌ_∞-regulator theory addressing this problem and applies this theory to the experimentally validated boiler/turbine model with actuator deadzone. Simulation results showing a considerable performance improvement are given.