Model predictive fluid temperature control for the quiet hydraulic precision turning machine

An application example of the model predictive control for the fluid temperature control of a precision machine is presented. The Stanford's quiet hydraulic precision lathe was designed to have an open fluid circulation system. By use of the temperature controlled fluid for the liquid shower as well as for the machine actuation, a uniform temperature environment can easily be generated and the machining accuracy level can be assured. The fluid temperature is regulated by a commercially available cross-flow type heat exchanger. Due to the inherent nonlinearities, and long time-delay characteristics, regulation of the fluid temperature variation at the shower point down to m/spl deg/C level is a very challenging problem. Successive feedback loops with Smith-predictors and disturbance feedforward control are implemented to regulate both the heat exchanger outlet and the shower point temperature. Good control results are obtained by this approach. The model predictive control with intentional temporal mismatch is also studied and verified by experimental results. The system performances are found to be dependent on a normalized parameter value, K/spl tau/.