Configuration Synthesis And Performance Optimization Of Redundant Actuated Parallel Mechanical Leg

In this paper,redundant actuated parallel leg mechanism which eliminates constraint/actuated singularity is synthesized for heavy haul transport robot.Based on the constrained screw theory,the linear correlation nature of constrained screw/secondary constrained screw is revealed,the criterion of constraint singularity and actuated singularity of parallel mechanism is given,and the design principle of redundant actuated parallel mechanism to eliminate constrained singular/actuated singular is proposed.According to the above principles and methods,this paper designs a 2RPS-UPU+2SPS redundant parallel leg mechanism with R~xR~yT~zthree degrees of freedom without constraint/actuated singularity.By using the boundary numerical search method,the workspace of the mechanism is obtained based on the inverse solution of the position,and the influence of the structural parameters of the platform on the workspace is solved by changing the structural parameters of the platform,and the size of the mechanism is optimized,which lays a foundation for the further kinematic optimization of the mechanism.The complete Jacobian matrix of 2RPS-UPU+2SPS redundant parallel mechanism is established,and the complete Jacobian matrix is confirmed to be full rank matrix.Finally,the rationality of the design principle and method of non-singular redundant parallel mechanism proposed in this paper is proved.It lays a necessary theoretical foundation for the improvement of motion flexibility,stiffness and bearing performance of walking robot leg mechanism.In this paper,the local and global motion/force transfer index of the motion/force transfer performance of the parallel leg mechanism 2RPS-UPU+2SPS is further developed,and the general general evaluation process of the redundant actuated parallel mechanism is proposed.And then using the global motion/force transfer index as the scale optimization design index of the mechanism,and optimizing the related parameters of the proposed redundant actuated parallel mechanism,so as to improve the motion and the force transmission performance in the workspace of the mechanism.Based on the principle of virtual work,this paper comprehensively considers the driving force and the binding force of the parallel mechanism to establish a complete static stiffness analysis model,and sets up a sensitivity index and a stiffness index evaluation model.The operation performance and stiffness performance of the redundant driving parallel mechanism and the non-redundant parallel mechanism are analyzed and compared,and then the two parallel mechanisms are simulated by the finite element software ANSYS.And the correctness of the theoretical calculation result and the addition of the redundant branched chain in the parallel mechanism to the improvement of the rigidity performance.In the end,based on the redundant parallel mechanical leg of 2RPS-UPU+2SPS,the four-legged robot is designed and inverse kinematics analysis,the stability analysis of the four-legged robot is carried out according to the static stability margin,and the influence of the center of gravity deviation on the stability of the quadruped robot is obtained by combining the stability margin analysis of the center of gravity.Given the trajectory of the foot end,the four-legged robot is modeled and simulated by using the software,and the movement displacement,the speed and the acceleration change curve of each leg driving rod in the course of a gait cycle are obtained,and the basis for the research of the four-legged robot in the future is laid.