Optimal design of N-UU parallel mechanisms

In this paper, we present the optimal design of N-UU (U stands for universal joints) parallel mechanisms (PM) with general geometry, for the achievement of maximal singularity-free tilt angle. We first briefly recall the synthesis condition and constraint analysis of the general N-UU PM, showing that static singularities may be factorized into active and passive constraint singularities. We then formulate the optimal design problem as the maximization of the end-effector tilt angle subject to closeness to active and passive constraint singularities. We conclude the paper by illustrating how an angle-equalizing device on the inner revolute pairs of the UU legs may help avoiding passive constraint singularities and increasing the maximal tilt angle.