3 1/2 DOF polynomial solution of the inferential H-2/H infinity control problem with application to metal rolling

The solution of a new inferential 31/2-degree-of-freedom stochastic optimal controlproblem is discussed which may be either H-2 or H-infinity optimal. The system includes a 21/2-degree-of-freedom inferential tracking controll er and a feedforward control action. The feedback controller must be robust and is therefore normally designed to minimize an H-infinity criterion. Ho wever the solution obtained is sufficiently general that the feedback, trac king or feedforward control functions can be chosen to minimize either an H -2 or a H-infinity criterion. The inferential control problem considered wa s motivated by a problem in the central of metal strip Yelling mills. The d esign study presented considers the control of strip thickness given stand force measurements, and the use of feedforward signal from an upstream stan d.