Research On Cutting Vibration Control By Magnetic Levitation Technology

The tool vibration in cutting process reduces the machining accuracy and stability.To this problem,this paper proposed a novel method using electromagnetic force to control the cutting vibration,which could ensure processing stability of cutting,enhance the efficiency of machining tool,as well as protect machine tool spindle system.Firstly,the dynamic model of cutting force was established.Milling stability was analyzed at frequency domain and time domain respectively.The milling stability lobe diagram was drawn through Semi-discretization Method.The cutting displacement was simulated with different parameters in different regions to validate the accuracy of milling stability lobe diagram.The structure of magnetic actuator is based on radial magnetic bearing.Eddy current displacement sensor is used to measure vibration displacement as feedback signal.The real-time output of controller is produced to control the electromagnetic force to suppress the vibration directly.A simplified test platform was designed to simulate cutting vibration.The steady-state sinusoidal excitation was carried out by internal excitation method and external excitation method which are analyzed experimentally.According to the uncertainty of magnetic actuator model and disturbance,a robust H_? controller was designed based on mixed sensitivity method using simulation to choose good weighted parameters.In order to verify the performance of H_? controller,vibration suppression experiments were carried out with sinusoidal and random excitation signal.Actual cutting vibration data which acquired in actual milling process was input to the simplified test platform to oscillate the rotor to simulate the cutting vibration in simplified test platform.The vibration suppression performance of magnetic actuator under H_? control and PID control was studied experimentally.The result showed that vibration amplitude was decreased to 30%~50% under H_? control,which proved that it has a certain effect on different cutting parameters.By contrast,the vibration reduction with PID controller was in the range of 40%~60%.H_? control algorithm depends on accurate mathematical model.And the selection of weighting function is empirical.So H_? controller does not reflect its advantages as expected.