A model for the automatic gage control (AGC) system of a steel rolling mill is shown in Figure P3.8. The rolls are pressed using a single acting hydraulic actuator with a valve
displacement of u. The rolls are displaced through y, thereby pressing the steel that is being rolled. The rolling force F is completely known from the steel parameters for a given y.
(i) Identify the inputs and the controlled variable in this control system.
(ii) In terms of the variables and system parameters indicated in Figure P3.8, write dynamic equations for the system, including valve nonlinearities.
(iii) What is the order of the system? Identify the response variables.
(iv) What variables would you measure (and feedback through suitable controllers) in order to improve the performance of the control system?