Type synthesis method of lower-mobility metamorphic parallel mechanism

To realize the innovative design of reconfigurable parallel mechanism, a design method of metamorphic parallel mechanism based on basic subchain configurations is proposed. Starting from the constraints acting on the moving platform of lower-mobility parallel mechanism, the basic subchains whose constraint is a force or a couple using characteristics of reciprocal screw are constructed. And according to configuration characteristics of the basic subchains, metamorphic subchains are constructed to realize the design of metamorphic parallel mechanism. The line vector force and couple subchains whose configurations are similar are combined to construct metamorphic subchains. The metamorphic subchains can transform between two types of basic subchains by locking different kinematic pairs, then the parallel mechanisms whose constrained type is variable can be constructed. According to the constrained screw direction characteristics of basic subchains, the force direction of subchain is changed by changing the axis direction of kinematic pairs, then the parallel mechanism whose constrained force direction is variable can be constructed. At the same time, using the proposed metamorphic parallel mechanism design method and Bricard linkage's single degree of freedom motion, a new type of parallel mechanism whose moving platform is Bricard linkage is constructed. Based on the basic subchains, the configurations of the metamorphic parallel mechanism are constructed. According to the constraint of the moving platform, the metamorphic subchains are combined and transformed, which realizes the type synthesis of metamorphic parallel mechanism and lays the foundation for innovation design of mechanism.