Research on Clamping Force Control of Hydraulic Power Chuck of Numerical Control Machine Tool

In order to solve the engineering application problems of the traditional variable pump pressure system driven by valve control or asynchronous motor associated with the rising temperature, complex structure etc, which could results in oil pollution resulted from leaking, low efficiency, and poor pressure retaining accuracy due to time-varying, nonlinear and hysteresis of the hydraulic power chuck. The unstable clamping force would cause machining error of parts. On the basis of analyzing the mathematical model of motor, power mechanism, execution mechanism and pressure sensor, the transfer function of direct drive pump controlled electric hydraulic pressure servo control system is derived, and a clamping force controller based on adaptive fuzzy PID control principle is proposed. The fuzzy rules and inference methods are used to tune the PID parameters online, and thus the flow rate of system is adjusted in real time to keep the clamping force constant. The effectiveness and feasibility of the proposed control method are verified with simulation and experiment. The results show that the fuzzy PID controller has a better dynamic performance and robustness than traditional PID controller, at the same time, the system has the fast response and no overshoot. This kind of system can completely meet the requirements on accuracy and stability of the clamping force in the machining process, especially for machining thin-walled parts.