Research On Bending Fatigue Test Control System Based On Voice Coil Motor

In modern industry,many metal material parts are subjected to cyclic reciprocating loads during work,which will cause the parts to be prone to fatigue damage.Therefore,bending fatigue tests on metal materials to understand their fatigue life can effectively improve the overall life of mechanical equipment.During the bending fatigue test,the parameter of the specimen will change with time.At this time,the fatigue test control system should ensure that the alternating force output to the specimen is within the expected range.Therefore,the force between the system and the specimen needs to be measured and corrected.In order to solve this problem,this paper has carried out a research on the bending fatigue test control system with the voice coil motor as an actuator.The position-based impedance control combined with the adaptive control law is used to control the force,and the force deviation caused by the change of the specimen parameter during the test is controlled and corrected.The research contents of this paper are as follows.This article adopts the position-based impedance control algorithm,so the position controller of the inner loop is analyzed and designed first.Through the analysis of the structure of the voice coil motor and its mathematical model to understand the working principle and driving mode of the motor.Then design the position controller of the motor.The structure of the position controller adopts the control form of three control loops.The three control loops are the position loop of the incremental PID controller,the speed loop with PI controller,and the current loop with adjustable parameters built in the general servo drive;and by adding acceleration feedforward and speed feedforward to improve the response speed of the system.Based on the above position controller,this article adopts the impedance control based on the position inner loop to indirectly control the force of the system,and analyzes the influence of the impedance control parameters on the system,understands the impedance parameter adjustment principle;analyzes the steady-state error of impedance control shows the influence of unknown or changing parameters of the specimen on its control performance,and because the parameters of the specimen will also change with time during the fatigue test,the impedance control of the fixed parameter at this time cannot meet the control requirements of the force applied to the specimen.In order to solve this problem,an adaptive control law is introduced.The control law automatically adjusts the impedance control parameters,so that the system can compensate for changes in material parameter during the test,so that the output force can always be kept within the expected range during the test.Finally,the experimental platform was built,and the position control and impedance control + adaptive control law were experimentally verified.The rectangular cross-section metal material was selected as the specimen,and the control effect of the test system when the alternating load was applied to the specimen was tested.The control effect experiment of the system when the parameter of the specimen changes is carried out.The results show that the impedance control + adaptive control law can control the alternating expected signal,and it has good adaptability to the change of the parameter of the specimen during the test.The requirements of the bending fatigue test on the control performance of the system.