Parallel Robots with Lockable Revolute Joints

This chapter describes a class of reconfigurable parallel robots consisting of a fixed base and a moving platform connected by n \(\text {R}_\text {b}\)RPS serial chains, with \(n<6\). Only the prismatic joints are actuated and the first revolute joint in each chain can be locked or released during operation. It will be shown how the introduction of these lockable joints allow the prismatic actuators to maneuver to approximate 6-degrees-of-freedom motions for the moving platform. An algorithm for generating these maneuvers is also described. Then, a motion planner, based on the generation of a probabilistic road map, whose nodes are connected using the described maneuvers, is presented. The generated trajectories are also designed to avoid both singularities and possible collisions between legs. Part of the work presented in this chapter appeared in [8].