Motion And Force Transmission Research Of TPM Without Closed-loop In Each Chain

The lower-mobility parallel mechanism has advantage over 6-DOF parallel mechanism in structural design,motion control and production cost,and the 3-DOF translational parallel mechanism which has the same branch chains and symmetrical structure is one of the hotspots.At the same time,in order to evaluate and describe the performance of the parallel mechanism,a reliable mechanism performance evaluation indicator for the design and research of 3-DOF translational parallel mechanism is with significance.In this paper,the following works are performed about the motion and force transmission performance of parallel mechanisms:Firstly,based on the analysis of the performance of the parallel mechanism at home and abroad,combined with local transmission index and screw theory,the maximum power efficiency index is defined,and it is non-dimensional-normalized.And then the motion and force transmission performance evaluation methods of the 3-DOF translational parallel mechanism is analyzed.The method analyzes the efficiency of the mechanism in transmitting energy from the input to output terminals,and establishes the formula of the power transfer efficiency under different conditions.Secondly,combined with the 3-RRC parallel mechanism,its position analysis is competed.The performance of the 3-RRC parallel mechanism is analyzed,and its transmission performance function and the condition of the singular configuration are obtained and verified by the method based on Jacobian matrix analysis.Finally,comparing the transmission performance of different parallel mechanism,when the 3-RRC parallel mechanism and the 3-CPR parallel mechanism are located at the midpoint of the input space,the 3-RRC parallel mechanism has the better performance than the 3-CPR parallel mechanism.Analyzing the motion and force transmission performance of the 3-RRC parallel mechanisms under the different actuating inputs,the influence of the different drive joint on the transmission performance is obtained.The results show that when the motion pair of the 3-RRC parallel mechanism is the drive joint,it will lose control of the motion.The structural parameters of the parallel mechanism are optimized according to the transmission performance function.The research works of this paper can be applied in the selection of parallel mechanisms,the selection of different configurations and the optimization of structural parameters,and it is with a good engineering practical significance.