H infinity preview control for discrete-time systems

A preview controller to be able to prepare a plant with the future informat ion for external disturbances will guarantee better performance to suppress their effects. A design approach far the optimal H-infinity preview contro ller in the discrete-time domain is given. The preview and feedback control ler are simultaneously designed to minimize the wet-st case RMS value of th e regulated variables when the bounded unknown disturbances and the preview able disturbances hit the dynamic plants. Thus, a state feedback controller and the related preview controller are derived in this design, even though problem formulation and solving art algebraic Riccati equation are based o n the full-information H-infinity controller design scheme. The performance of the proposed preview controller is simulated with a rolling stand of th e tandem cold mill in the steel-making works. The objective of the control system for the rolling stand is to minimize thickness error of the exit str ip and tension variation between stands simultaneously. The entry strip thi ckness to the stand and the roll gap variation are considered as previewabl e disturbances, since they can be measured and estimated. The future inform ations of these physical variables are utilized in the preview controller t o suppress their effects an the exit strip thickness and the inter-stand te nsion. The simulation results shows that the H-infinity preview controller is effective to satisfy the requirements for the thickness and the tension.