Research On Spherical Motor For Robot Joint

With the rapid development of IC and 3C industries,various fields have put forward higher and higher requirements for the accuracy,speed and efficiency of robots.The structure of the conventional robot with "rotary motor+reducer" is difficult to meet the requirements.At present,the integrated joint structure of DD motor direct drive is adopted at home and abroad to realize the high speed,high precision and high dynamic performance of the robot.However,it can only make single degree freedom of single joint to drive and it is impossible to make multi-degree-freedom of single-joint achieve high-precision driving.Therefore,this paper proposes a new structure of spherical motor for robot joints to realize multi-degree-freedom of single-joint motion and control.The focus is on optimizing the spherical motor from three aspects:motor structure,magnetic field design and control method to realize high-speed,high-precision and dynamic characteristics of the robot joint.Firstly,according to the characteristics of large torque to volume ratio of the robot joint,the HALBACH permanent magnet array distribution method is adopted,and the width of permanent magnet,the thickness of permanent magnet,the groove depth,the groove width,the air gap and are analyzed the influence on the torque,levitation force,cogging torque,back-EM potential harmonic distortion rate from the angle of the magnetic field optimizationSecondly,for the complex coupling model of the robot joint spherical motor,the suspension force and torque are decoupled based on the modular idea,the decoupling of the suspension force and the space rotation torque is realized,and the dynamic model of the suspension direction and the space rotation driving direction are established to achieve spatial decoupling control.Then,aiming at the easy interference of the spherical motor in the rotating direction,a sliding mode variable structure control algorithm based on exponential approach law is designed for the unit drive module to improve its robustness.In order to improve the dynamic response,stability and anti-interference ability of the suspension direction,a sliding mode control method based on Terminal is designed and its dynamic tracking response simulation is studied.Finally,based on this,a spherical motor control system based on TMS320F28335 is built,and a sensorless software design scheme based on the main control chip is proposed.The speed detection of stable spin,the no-load current was tested,the high speed and high dynamic characteristics of the spherical motor are verified.