A novel reconfigurable parallel mechanism constructed with spatial metamorphic four-link mechanism

In this paper, a spatial metamorphic four-link mechanism (SMM) based on the metamorphic universal joint is proposed. By adjusting the axis position of the universal joint, three kinds of SMMs are constructed. Each kind of SMM has different bifurcation and metamorphic characteristics. Starting from the motion characteristics of each phase of SMM based on the screw theory, a reconfigurable hybrid limb is constructed by combining it with the series branch which can provide a constraint force and a constraint couple. The constraint changes of metamorphic hybrid limbs corresponding to different phases of SMM are analyzed. This leads to the design of a new type of reconfigurable parallel mechanism (RPM), in which the platform is connected to the base by three reconfigurable hybrid limbs. The results show that the performance of the RPM can be changed from 6 degrees of freedom (DOFs) to 5, 4, and 3 DOFs.