Research On Key Technology Of Permanent Magnet AC Servo System For Horizontal Articulated Manipulator

The horizontal joint manipulator(SCARA)has been widely applied in many fields,such as mechanical processing,material handling,PCB welding and so on because of its simple structure,high repetitive accuracy and fast dynamic response.However,due to the particularity of the working conditions of the manipulator,the manipulator has higher requirements for its joint permanent magnet AC servo drive system,such as higher accuracy,faster response speed and other high-end performance indicators.At present,the general permanent magnet AC servo system and technology can't be met at home,which has become one of the bottlenecks in the research and development of the domestic manipulator.Therefore,in order to satisfy the high-speed and high-precision driving of the manipulator,two key technologies on how to improve the positioning accuracy and response speed of the servo system are studied.Firstly,this paper investigates and analyzes the design schemes of various manufacturers at home and abroad.In consideration of the application of the manipulator,a highly integrated design of the SCARA manipulator is proposed.This scheme integrates motor,drive,photoelectric encoder and mechanical arm body,and has the advantages of high integration,low cost and small volume.Secondly,aiming at the application condition of SCARA manipulator,a high speed and high precision driving positioning control strategy for SCARA manipulator is proposed base on traditional three closed loop control strategy.First,the high frequency injection method is introduced to the initial position detection of the motor in order to achieve high response start.A heterodyne method is used to extract the position information of the rotor,and a zero lag and zero steady-state error location tracker is designed.Second,in order to get the initial position of robot arm and improve the accuracy of position control,a new hybrid encoder design with special rule is proposed.Based on this,a real-time position inspection method of SCARA manipulator joint based on hybrid dual encoder is proposed.Third,in order to reduce the effect of disturbance on the positioning performance of the drive system,a two level active disturbance rejection controller with position and speed control is designed to replace traditional PI control.Finally,three control algorithms are integrated.A special position servo drive system with high response and high precision is designed.Thirdly,in order to verify the feasibility of the scheme,a simulation model of IPMSM and position observer with high frequency injection method is built based on Matlab/Simulik,and the simulation analysis is carried out.It is known from the simulation results that the estimation error of the rotor position is within 1.8 degrees(electric angle)at zero speed.The estimation error of the rotor position is less than 10 degrees(electric angle)at low speed.Therefore,the high frequency signal injection method can effectively obtain the position of the motor rotor at zero and low speed conditions.Finally,a prototype of the driver is designed with the control algorithm.It consists of the control core and its peripheral circuit,the PWM isolation drive circuit,the current sampling circuit,the position detection circuit and the communication circuit.Based on this,taking X joint of SCARA manipulator as the experimental object,the initial position detection of motor,the initial position detection of manipulator joint,positioning control of manipulator joint,anti disturbance experiment of manipulator joint are carried out.The experimental results show that the estimation error of the initial rotor position is less than 8 degrees(electric angle).The detection results of the initial position of the manipulator joint are in agreement with the given initial position.The real-time position detection precision of the manipulator joint based on the hybrid dual encoder is 95% higher than that of the single encoder detection method.The anti disturbance performance of the drive control system with auto disturbance rejection control is greatly improved than the traditional PI control.Therefore,the method proposed in this paper can acquire initial position information of motor and robot arm joints in initial power up process,so achieve rapid startup of motor's larger torque.And in the whole operation process,the high precision real-time position information of the manipulator joint can be obtained,thus the positioning accuracy of the manipulator can be improved.It also has strong robustness against disturbance.