A new quantitative performance index for low mobility parallel kinematic manipulators´ accuracy

Due to the effect of joint clearance and component flexibility ( joint or link), a parallel kinematic manipulator (PKM), with proposed motion type G ⊂ SE(3), may have undesirable (or uncompensatible) pose error beyond G at the end-effector, which would cause severe accuracy performance degeneration of the PKM. As such phenomenons have been discovered and verified in many researches, we proposed a new performance index, called "Type Error", which could be applied to evaluate such undesirable errors. Specifically with this index, the largest translational/rotational pose error could be quantized and the worst case over the designed workspace can be predicted. A three-step method for general application is presented in details by case study of three kinds of translational PKM.