STRUCTURAL SYNTHESIS OF A CLASS OF RECONFIGURABLE PARALLEL MANIPULATORS BASED ON OVER-CONSTRAINED MECHANISMS

摘要

This paper presents a novel way to design a family of reconfigurable parallel mechanisms based on over-constrained mechanisms. In this paper, some single-loop over-constrained mechanisms with lower degrees of freedom (DOFs) are analysed and their classical structures are obtained. (In this paper, the letter C or F and the associated number indicate the type and number of independent constraint couples or forces in the mechanism.) Then, some special single-loop mechanisms are selected to conduct further study, including F1 (one independent force), C1 (one independent couple) and F1C2 (one independent force and two independent couples) over-constrained mechanisms, and the characteristics of these mechanisms are calculated by using screw theory. Some theorems are proposed to design the multi-loop over-constrained mechanisms. According to these theorems, the F1, C1, F1C2 and mixed multi-loop over-constrained mechanisms are designed. Thus, a family of multi-loop over-constrained mechanisms is evolved, and the 3, 4 and 6 limbs of multi-loop over-constrained mechanisms are listed in the tables. Parallel mechanisms are combined with the multi-loop over-constrained mechanisms to generate the reconfigurable parallel mechanisms. Finally, some 3-link, 4-link and 6-link reconfigurable parallel mechanisms are presented to verify the new method.