The Study Of Vibration Suppression Method Based On Electromechanical Integrated Joint Of Collaborative Robot

Collaborative robot is a kind of robot which can interact and cooperate with people in the common working space.It is an important development direction of robot technology,and will profoundly affect and change the production and life style of human society.The integrated joint is the core device of collaborative robot,which is generally composed of permanent magnet torque motor,servo driver,harmonic reducer,electromagnetic brake,motor end and load end position encoder,torque sensor and other devices.However,the flexible wheel in the harmonic reducer and the strain gauge in the torque sensor bring the flexibility and low stiffness characteristics to the robot joint,thus reducing the joint bandwidth and causing problems such as vibration.The torque fluctuation and external disturbance of permanent magnet torque motor will also cause vibration,which will lead to the decrease of positioning accuracy and force control accuracy.Therefore,it is very important to study the vibration mechanism of the integrated joint and propose effective vibration suppression methods to improve the control accuracy and compliance of the collaborative robot.Based on this background,this paper mainly does the following research:First,dynamic modeling and researching on vibration mechanism of the integrated joint of collaborative robot.The dynamic characteristics of each part of the joint in the integrated design are analyzed and the dynamic model of the joint is established.The modal analysis is carried out by the impact method combined with the frequency response method to identify the model parameters.The mechanism of joint vibration caused by motor torque fluctuation,joint mechanical flexibility such as harmonic reducer and external force interference such as load change is studied,and the mechanism of joint vibration is revealed.The influence of joint torque fluctuation on joint positioning accuracy in forward drive motion control and on joint force control accuracy in reverse drive compliance control are analyzed.Secondly,vibration identification and vibration modeling of the integrated joint of collaborative robot.Combined with the position information of double encoders and the feature extraction method of Fourier signal,the vibration signals in the process of motion is modeled and frequency components of them are identified by frequency analysis,frequency spectrum analysis,phase analysis and theoretical analysis.Thirdly,vibration suppression method research on the integrated joint of collaborative robot.Study the method of torque ripple compensation based on iterative learning control;explore the method of vibration suppression caused by transmission error of harmonic reducer based on feedforward compensation;study the observation,extraction and suppression of vibration signal based on disturbance observer for external force interference caused by variable load.Finally,experimental research and verification of the vibration suppression method proposed for transmission error of the Harmonic Drive,and analysis of the reasons for the imperfection of experimental results.The experimental results show that the model-based feedforward vibration suppression method is effective,but it depends on the accurate system dynamics model and transmission error model.This paper provides guidance and suggestions for the research of vibration suppression methods of integrated joint of collaborative robot,and lays a foundation for the vibration suppression of the whole collaborative robot in the future.