Position Analysis of a Bennett-Based Multiple-Mode 7R Linkage

This paper deals with the position analysis of a multiple-mode 7R spatial linkage. The 7R linkage is constructed by combining two Bennett linkages with a common joint. As a result, the motions of the Bennett linkages are embedded in the multiple-mode 7R linkage, and there are three operation modes of the linkage: two Bennett modes and one 7R mode. The algorithms for solving the inverse kinematics of serial 6R manipulators are employed to find all possible configurations of the 7R linkage at a given value of the driving joint angle. The analysis is then conducted for a full rotation of the driving joint. The result of the analysis gives all feasible configurations of the linkage for a full rotation of the driving joint. According to the result of analysis, the motion of the linkage can be clearly divided into the three operation modes, and the linkage can switch between two modes at various connecting configurations. Furthermore, because of the two Bennett modes, the linkage can reach all feasible configurations without being taken apart and reassembled. This paper provides insight into the kinematics of multiple-mode single-loop 7R linkages constructed by combining paradoxic linkages.