Study Of Pneumatic Robot End-effector With Force Control

With the development of robot technology,force control technology has become a research hotspot in recent years.The force control unit at the end of the industrial robot can perform force/position decoupling control on the output force,which is beneficial to the improvement of the force control precision.The pneumatic robotic force control device has natural flexibility and is suitable for contact work such as assembly,polishing and grinding,but its severe nonlinearity at low pressure makes it difficult to achieve the desired control effect.Among the many influencing factors,the factor that has a great influence on the dynamic and static characteristics of the pneumatic robotic force control device is the friction factor.Compensation of friction effectively is the key to improve the accuracy of force control.Therefore,it is necessary to carry out research on friction compensation of pneumatic robot End-Effector with force control.The main research contents are as follows:(1)The mathematical model of the pneumatic robot end-effector with force control was derived based on the physical mechanism and the simulation model was established based on AMESim.At the same time,the friction model of the cylinder was established based on Simulink and the friction characteristics were simulated and analyzed.The cylinder friction identification experiment platform was designed,and the LuGre friction model of the cylinder was identified offline.(2)The two-step method was used to identify the parameters of the LuGre friction model,and the static parameters of the model were first identified.Comparing the effect of segment fitting and nonlinear least squares fitting,it was concluded that the static parameters of the segment fitting model are better.The genetic algorithm was used to fit the dynamic parameters of the model,which provided specific parameters for the simulation research and experimental research of the compensation control of the pneumatic robot end-effector with force control.(3)In order to improve the response performance of the pneumatic robot end-effector with force control,the feedforward control strategy is studied.A fuzzy PID controller was designed based on Simulink and simulated with AMESim.Comparing the tracking performance of fuzzy PID and traditional PID to the step signal,the adjustment time of the former is reduced by 0.46 seconds,which verifies the effectiveness of fuzzy PID.Combined with the identified parameters of LuGre friction model,the LuGre feedforward fuzzy PID controller was designed and compared with the fuzzy PID.The adjustment time of the former was reduced by 0.16 seconds,which verified the feasibility of LuGre feedforward control.(4)In order to further verify the effectiveness of the feedforward control strategy based on the friction model,the structural design and component selection of the pneumatic force servo system were carried out.The control system was designed which included the controller,control cabinet and human-computer interface.Finally,the experimental platform of the system was built.The tracking performance of fuzzy PID control and fuzzy PID control based on LuGre friction model was compared.The former effectively improved the hysteresis and tracking error was stable below 5%.