| The number of degree of freedoms(DOFs)of the lower-mobility parallel mechanisms is less than 6,and the parallel mechanism with two-rotation-one-translation is widely used.The number of actuations of the redundantly actuated parallel mechanism is more than the number of DOFs,and the subtractive value is called redundancy.The parallel mechanism with redundancy of more than or equal to 2 is called multi-redundantly actuated parallel mechanism.In this paper,a multi-redundantly actuated 2RPU+2UPR+RPR parallel mechanism with two-rotation-one-translation is taken as the research object,and its freedom analysis,kinematics and dynamics modeling,performance analysis,dimension optimization and singularity research are carried out,and the internal relationship between the performance map and the key dimensions of the mechanism is analyzed.The main research contents are as follows:(1)A multi-redundantly actuated parallel mechanism 2RPU+2UPR+RPR is proposed.Based on the screw theory,the kinematic screw system and the constrained screw system of the mechanism are established,and the properties of the DOFs are analyzed;The kinematic model of the mechanism is established,the inverse solution of position and velocity is analyzed,and the correctness of the theoretical model is verified by simulation software.(2)The performance of the mechanism is analyzed and evaluated with the kinematic dexterity index and the motion/force transmission performance index,and the local performance index and the global performance index are established.The dimension optimization research is carried out based on the global performance index,and the optimization dimension and performance map are obtained,and the influence of the key dimension parameters on the mechanism performance is analyzed.(3)The dynamic model of the mechanism is established based on the principle of virtual work,and the dynamic theoretical model is verified by simulation software.Optimize the driving force coordination performance evaluation index of the multiredundantly actuated parallel mechanism,establish the local coordination index and the global coordination index,and conduct the dimension optimization research based on the global coordination index,obtain the mechanism optimization dimension and coordination performance map,and analyze the impact of key dimension parameters on the coordination performance.(4)Based on Jacobian matrix method,kinematic principle method and motion/force transmission performance,the singularity of the mechanism is studied,the singularity characteristics under the optimized dimension are analyzed,and the spatial distribution of singularity and transmission performance values are drawn.Through multi-method singularity analysis,it is confirmed that there is no singularity in the search space of the mechanism.The research content of this paper has important guiding significance for the performance analysis,dimension optimization,driving force coordination mechanism research and practical application of multi-redundantly actuated parallel mechanism. |
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