  In this paper, a method to compute joint space singularity surfaces of 3-RPR
planar parallel manipulators is first presented. Then, a procedure to determine
maximal joint space singularity-free boxes is introduced. Numerical examples
are given in order to illustrate graphically the results. This study is of high
interest for planning trajectories in the joint space of 3-RPR parallel
manipulators and for manipulators design as it may constitute a tool for
choosing appropriate joint limits and thus for sizing the link lengths of the
manipulator.
