Type synthesis of a family of novel parallel leg mechanisms driven by a 3-DOF drive system

Abstract The complex structures, small workspaces and complex control systems of traditional parallel mechanisms are the largest hurdles to using them as leg mechanisms in walking robots. This paper synthesizes a family of novel 3-degrees-of-freedom (DOF) parallel leg mechanisms (PLMs) that have the potential to avoid these drawbacks. The novel parallel leg mechanism consists of a 3-DOF drive system (DS) and a walking mechanism, which can be designed modularly. Using the motion characteristics of the 3-DOF drive system, a simplified method for constructing 3-DOF parallel leg mechanisms is presented. Then, satisfactory 2-DOF walking mechanisms are synthesized based on Lie group theory. A family of novel 3-DOF parallel leg mechanisms in which the workspace of the foot-endpoint is a three-dimensional volume is constructed using the 3-DOF drive systems and 2-DOF walking mechanisms. Finally, the performance of the novel parallel leg mechanism is analysed, revealing the potential merits of this novel parallel leg mechanism in walking robots.