Equivalent Method of Output Mobility Calculation for a Novel Multi-loop Coupled Mechanism

In view of the different structures between novel multi-loop coupled mechanisms and common parallel mechanisms, a novel method is proposed for output constraint and mobility analysis of multi-loop coupled mechanisms. Converting a coupled mechanism into a common parallel mechanism is the main idea. A rule is given to split the connection between input and output into several independent elements. Relative motions of the coupled-nod link in every element are analyzed based on screw theory, and the element including coupled structure is ultimately equivalent to a serial chain. Thus the whole coupled mechanism is equivalent to a parallel mechanism. Limb twist systems and limb constraint systems of the equivalent parallel mechanism are analyzed, and the output mobility is calculated by re-solving the reciprocal screws of the constraint screws. The proposed method is applied to a typical coupled mechanism, and the computed result is in accordance with the prototype, which shows that the equivalent method can effectively simplify the complicated structure and get the correct mobility.