A Novel Parallel Kinematic Mechanism With Single Actuator for Multi-DoF Forming Machine

The parallel kinematic mechanism (PKM) is typically equipped with multiple actuators to realize the precise and arbitrary spatial motion, but resulting in complex mechanical and control systems and high cost. Actually, in many specific fields, such as heavy load metal forming process, the motion of PKM is only needed to be specific and the motion precision requirement is not extremely high. This paper proposes a new approximate mechanism synthesis method for PKM with single actuator (PKMSA), which not only can simplify the complexity of PKM and reduce the cost, but also can realize the specific motion with permissible error. Firstly, the design criteria of the consistency between the motion pattern of the PKMSA and required motion DoF is determined to avoid the occurrence of kinematic redundancy error. Then a general kinematic model for PKMSA is derived based on the screw theory, and the general constraints are obtained for PKMSA to realize the specific motion. On this basis, a 3-RSS/S PKMSA configured with a single input and triple output actuator layout realized by a gear set is proposed. Finally, a heavy load multi-DoF forming machine (load of 200 kN) with PKMSA is developed and, with that, the multi-DoF forming experiment of a typical metal component is conducted with forming load of about 180 kN. The geometric deviation of formed component is in the range of −40∼55 μm (it can completely meet the forming accuracy requirement), validating the feasibility of the proposed approximate mechanism synthesis method for PKMSA.