Abstract:
A novel Proportional-Integral-Derivative (PID) control method is proposed for the oil cooler of machine tools to achieve better set-point tracking and disturbance rejection performance. The simple PID controller based on Smith predictive method is adopted as the basic controller. To deal with the nonlinear time varying and time delay characteristic of the system, the PWM (pulse width modulation) technique is then chosen as an auxiliary duty ratio control to modulate the bypass solenoid valve to provide precise oil temperature control. Both simulation results using MATLAB and on-site experimental results are presented and compared extensively for demonstrating the effectiveness of the proposed control scheme. The control scheme not only improves the performance of PID controllers cost-effectively but also maintains permanent temperature control specific for machine tool coolers.