Research On Variable Stiffness Actuator Of Compliant Robot Joint Based On Antagonistic Principle

Robots are no longer confined to traditional industrial production in a structured environment,but gradually liberated from closed work spaces and enter unstructured environments for human-machine collaboration.It causes the robot to collide with surrounding objects and humans inevitably,causing the robot to be damaged by strong impact and even causing fatal damage to surrounding people.In order to solve the safety problem in the humanmachine collaborative process,it is necessary to make the robot joints have compliant performance.The variable stiffness joint based on the principle of antagonism originates from bionics,which is a very important way to achieve joint compliance.Therefore,it is of great significance to carry out related research.The core part of the variable stiffness joint is the variable stiffness actuator,which mainly consists of elastic elements and an antagonistic force pair.Among the existing research results,the elastic element is arranged in series with the antagonistic force and participates in the formation of antagonism.In this paper,a new variable stiffness implementation principle is proposed,in which the linear spring is arranged in parallel with the antagonistic force,so that the elastic element is no longer involved in antagonism,which effectively eliminates the antagonistic effect of the elastic element and improves the bearing capacity and energy storage capacity.The use of extremely lightweight springs and steel wire simplifies the structural details of the variable stiffness actuator and reduces the mass and volume of the joint.In addition,the double stiffness characteristic provides multiple solutions for stiffness adjustment,which can effectively improve the stiffness adjustment speed.The main research contents of this paper are as follows:(1)Research on new mechanism of variable stiffness actuator based on antagonistic principle.Based on the literature research,the advantages and disadvantages of the existing variable stiffness joints and actuators are analyzed.The mechanism of the new variable stiffness actuator is proposed,and the model of the variable stiffness actuator is designed.(2)Constructing mathematical models and conducting variable stiffness theory research.A mathematical model for the variable stiffness characteristics of the variable stiffness actuator is constructed,and its variable stiffness characteristics are theoretically analyzed.(3)Simulation and experiment research.The variable stiffness performance of the variable stiffness actuator was simulated,and position PID control of the virtual prototype is implemented via co-simulation with ADAMS and MATLAB.Finally,a experiment platform was set up,and the feasibility of the proposed principle was verified by comparing the test data with the simulation results.