Kinematic Control And Calibration Of Spherical Parallel Bionic Hip Joint

The accuracy of the end pose of the parallel mechanism is an important indicator of the performance of the robot,which directly affects a large number of industrial applications.Therefore,it is of great significance to study how to effectively improve the accuracy of the parallel mechanism.In this paper,the existing 3-RRR+(S-P)spherical parallel bionic hip joint prototype of my research group is studied.This paper focuses on two aspects of kinematic control and kinematic calibration,aiming to achieve the real-time movement of the prototype with high precision.Firstly,in the environment of the prototype control system based on the “PC + UMAC multi-axis motion controller” control mode,the kinematic model of the 3-RRR+(S-P)spherical parallel bionic hip joint is embedded into the UMAC controller to realize the initial kinematic control of the mechanism.The planned trajectory is simulated and analyzed in ADAMS and the motion program is compiled accordingly.In the PC software Pewin32PRO2,the PID parameter setting and zeroing operation are performed,and finally the control system was successfully debugged,which provide the basis of motion control for later kinematic calibration experiments.Then,the kinematic calibration of the 3-RRR+(S-P)spherical parallel bionic hip joint is studied.Based on the kinematic model and geometric structure,the closed-loop vector method is used to establish the external branch error model and the central branch error model,which are unified into a combined error model.According to the model,the distribution of pose error and the influence of single error source are simulated and analyzed in MATLAB.The pose measurement scheme is designed by using the orthogonal test method and taking the condition number of the error Jacobian matrix as a reference.Based on the error model and pose measurement results,24 error parameters are identified by LM(Levenberg-Marquardt)algorithm and genetic algorithm respectively.The identification results of the two methods are analyzed and compared.In addition,based on the kinematic model and pose measurement results,the genetic algorithm is used to directly identify the parameters in the kinematic model.According to the identification result,the error compensation of the prototype can be performed by correcting the system input and correcting the geometric parameters of the control model.Finally,in the Visual Studio 2017 environment,the control system software interface is designed by applying the VB.net development language to provide convenience for calibration experiments.The calibration experiments of 3-RRR+(S-P)spherical parallel bionic hip joint prototype are carried out by laser tracker,including zero calibration experiment,repeated positioning accuracy test,pose measurement experiment and error compensation experiment,and the calibration results are analyzed.