| The flexible robot can realize the change of stiffness,and the abilities of well stiffness adjustment and anti-interference make the robot provide better security and working stability in human-robot interaction.In order to further explore the compliant motion research and improve the working performance of the robot,in this paper,a new wire-driven variable stiffness robot elbow joint was proposed which based on permanent magnet spring,pulley block and planetary gear train(VSJPPP).Firstly,the overall elbow joint structure was designed which according to the performance parameters of the human elbow joint as the design goals,the basic principle of the application of the elbow joint was expounded.The double wire-driving system was symmetrically arranged to make the elbow joint antagonistic in motion.The stiffness change was produced by the magnetic spring variable stiffness module,and the range could be increased by the pulley blocks.The structure of each component was designed,and the three-dimensional model of the whole joint was contributed,and the finite element simulation software was used to check and analyze the core parts of the elbow joint,and the positions of each detection element were arranged.At the same time of structural design,the theoretical model of elbow joint is deduced.According to the joint structure,the robot coordinate system was established,and the relationship of the change of joint position and stiffness caused the change of wire length were proposed respectively.The Jacobi matrix of the robot was deduced according to the relationship between the length change of the wire and the joint position motion,and the stiffness model of the robot was established.The dynamic model of elbow joint was established by deducing the static equation of joint.In order to realize the independent control of joint position and stiffness,the decoupling controller of elbow stiffness and position was designed according to the derived stiffness model and dynamic model.Secondly,according to the designed structure and the derived joint model,the stiffness change and motion of the joint were simulated and tested.Ansoft Maxwell software was used to carry out the repulsion force between the permanent magnet rings in the variable stiffness model.The relationship between wire tension and wire length in variable stiffness module was obtained by simulation and calculation,and the curve fitting was carried out by Matlab software according to the simulation data.According to the simulation and calculation of the double-input stiffness model of the elbow joint.The influence of the length of the wire and the rotation position of the joint on the stiffness change of the elbow joint was summarized.The Matlab/Simulink module was used to build the block diagram of the decoupling controller,and the experimental scheme of the elbow joint independent control was designed to verify the feasibility of the joint stiffness position decoupling control.Finally,according to the designed structure,the experimental prototype was processed and the experimental platforms were built.The stiffness decoupling control experiment,position step control experiment and sinusoidal trajectory control experiment were carried out respectively.Based on the motion data of joint was collected under different stiffness conditions,the influence regulation of joint stiffness on motion and the source of motion error were analyzed and summarized,and the accuracy of control and the stability of movement were verified. |
PDF Full Text Request