Evaluation method of motion/force transmission performance for parallel mechanisms with sub-moving platforms

A class of parallel mechanisms with sub-moving platforms (PMs-SMPs) has significant advantages in stiffness and loading capacity over traditional PMs. A detailed classification of both the PMs-SMPs and their sub-PMs are given. One of the essential roles for PMs is to transmit motion/force between the input and output ends. An evaluation method of motion/force transmission performance (EMoMFTP) for PMs-SMPs is proposed based on the equivalent actuated joint (EAJ) strategy and modified input transmission index (MITI). Then, the definition and operation rules of the MFTP index for PMs-SMPs are established in accordance with the worst condition principle. Finally, the MFTP indices of three examples are solved, and the validity and practicability of the EMoMFTP are verified based on the singularity analysis principle of sub-kinematic chain (SKC) unit. The results show that the EMoMFTP can find all possible input singularity configurations and measure the proximity between a given pose and a singularity configuration.