Development Of Direct-drive SCARA Robot Driven By Magnetic Gear Compound Motor

SCARA robots are widely used in IC,semiconductor,3C industry and other precision assembly fields.With the development of more and more miniaturized products,the precision requirements for assembly robots are becoming higher and higher.The traditional SCARA robots have been unable to meet the requirements for robot speed and precision in assembly operations,so it is urgent to improve the performance of robots.At present,the methods such as trajectory path optimization and control algorithm are widely adopted at home and abroad.However,the fundamental measures to improve the robot precision should be studied from the new ontology structure in addition to software optimization.Therefore,in this paper,magnetic gear direct drive motor is used to replace the mechanical deceleration structure of traditional SCARA robot,and a high precision and high response direct drive SCARA robot is designed.The design of magnetic gear direct drive joint motor for SCARA robot and the trajectory tracking control method for direct drive robot are emphatically studied.Firstly,aiming at the problems of large transmission error and low power density of current SCARA robot joint motor,this paper proposes to use magnetic gear direct drive motor to drive SCARA robot joint.According to the working requirements of SCARA robot in this paper,the design index of magnetic gear direct drive motor is put forward,and then the magnetic gear compound motor is designed by finite element method.The influences of permanent magnet thickness,magnetic ring thickness,internal permanent magnet thickness,air gap length and other parameters on joint driving performance were analyzed,and a high power density magnetic gear direct drive motor for robot joint was designed.Secondly,the joint transmission schemes of SCARA robot based on magnetic gear direct drive motor are introduced in detail.In order to further improve the speed and precision performance of SCARA robot,genetic algorithm is used to optimize the big arm length and forearm length of SCARA robot.According to the optimization results,a three?dimensional model of direct drive SCARA is established,and the effectiveness of optimization is verified by simulation.The driving error of direct drive SCARA joints was analyzed and calculated,and the advantages of direct drive were verified by comparing with non-direct drive joints.Then,aiming at the problem of larger torque ripple caused by robot direct drive joints,a control method based on robot end trajectory dynamics was proposed to achieve accurate tracking and positioning of robot end.After the joint dynamics model of SC ARA robot is established by Lagrange method,the dynamic model of the SCARA robot end trajectory is established according to the mapping relationship between the end force and joint moment of the robot.Based on the robot end trajectory dynamics model,a sliding mode controller with exponential approach law is designed to eliminate the robot end jitter.The stability of the controller is analyzed by lyapunov stability theory,and the control system is simulated by Matlab to verify the effectiveness of the robot end track sliding mode control method.At last,the prototype of magnetic gear compound motor was processed,and the motor was applied to the X-axis and Y-axis of SCARA robot,and the prototype of SCARA robot was completed.The control system of SCARA robot was set up to test the performance of magnetic gear compound direct-drive motor.The repetitive positioning accuracy of the direct drive SCARA robot is tested according to the national standard of industrial robot performance test,and compared with the non-direct drive robot to verify the excellent characteristics of the direct drive SCARA robot designed in this paper.