Error Analysis And Kinematic Experimental Study On The Bionic Hip Joint With Spherical Parallel Manipulator

In the design of humanoid robots,the joint and the whole configuration is one of key segments to realize the smooth action and the anthropomorphic of the joint,owing to which the innovation of mechanism ontology or the research on application of existing configurations is still of great significance.In this paper,based on the physiological structure of human hip joint and bionic design principles,the bias output 3-RRR-(S-P)spherical parallel mechanism is introduced into the bionic hip joint,the relevant theoretical analysis and experimental research on how to improve the precision of the prototype,ensure the performance of prototype control system and realize the anthropomorphic movement are performed.Specific contents are as follows:First,the kinematics and the velocity Jacobian matrix of the prototype mechanism are analyzed,and the trajectory of the output is planned.The kinematics of the mechanism is the basis of controlling its movement,and combined with the spherical characteristic of the output space of the mechanism,the position of the moving platform is described by the rotating transform general formula,the inverse kinematics solution is obtained.Based on the virtual mechanism method and the influence coefficient method,the velocity Jacobian matrix of the mechanism is solved to provide theoretical basis for velocity control of the mechanism.The trajectory of the output at two discrete points is planned with a method of the acceleration as continuous segmented function,the specific way of determining the position and rotation angle between the discrete points is given.With the aid of Matlab and Solidworks software,the kinematics is simulated and verified.Then,the error model of bionic hip joint prototype is established to provide theoretical support for the accuracy of the prototype.Based on the D-H parameter method,the parametric expression of the branch in the 3-RRR +(S-P)spherical parallel mechanism is given.The position and the error model of 3-RRR+(S-P)spherical parallel mechanism are established by using the loop increment method,the relationship among the output error of the mechanism and the axial spacing error,the shaft spacing error and the axial angular error of the motion pair is analyzed to obtain the geometry conditions for the smooth operation of the mechanism in the production and assembly.Finally,according to the analysis results of mechanism error model,structures of the external branch and the central branch of the mechanism are designed,and the design of bionic hip joint prototype is completed.Based on Umac controller,the bionic hip joint prototype control system is built by using the mode of "PC + Umac controller" master-slave control mode,and the stability and responsiveness of the control system is improved by tuning the PID parameters and the notch filter parameters.On the basis of the fitting function of the specific motion data of the human hip,the ability of the bionic hip joint to reproduce the human hip movement is verified by actual experiments.