3½ DOF polynomial solution of the inferential H2/H∞ control problem

The solution of a new inferential 3½ degree-of-freedom stochastic optimal control problem is discussed which may be either H ₂ or H_∞ optimal. The system includes a 2½ degree-of-freedom inferential tracking controller and a feedforward control action. The feedback controller must be robust and is therefore normally designed to minimize an H_∞ criterion. However, the solution obtained is sufficiently general that the feedback, tracking or feedforward control functions can be chosen to minimize either an H₂ or a H_∞ criterion. The inferential control problem considered was motivated by a problem in the control of metal strip rolling mills