THE EFFECT ANALYSIS OF INPUT SELECTION ON PERFORMANCES OF 3-PPRR TRANSLATIONAL PARALLEL MECHANISM

Yanzhi Zhao, Bowen Liang, Jie Zhang, Lizhe Qi, Dan Zhang, and Wei Yang

Keywords

Parallel mechanism, input selection, dynamics, motion/force transmissibility, dexterity

Abstract

Input selection is one of the key problems in the design of parallel mechanisms. Meanwhile, the different reasonable input combinations have various effects on the performance of parallel mechanism. There are four kinds of reasonable input combinations for the 3-PPRR translational parallel mechanism. Interestingly, it is found that the Jacobian matrix of this mechanism is constant when the first prismatic joint of each PPRR limb is chosen as an actuator and others are not. This paper will analyse the effect of input selection of the 3-PPRR parallel mechanism on its dynamics, motion/force transmissibility and dexterity performances. Firstly, the degrees of freedom, position inverse solution and workspace of the 3-PPRR parallel mechanism are analysed. Based on this foundation, all kinds of Jacobian matrices corresponding reasonable input combinations are solved by screw theory. Furthermore, through analysis of dynamics model with the effect of gravity and inertia force, the 3-PPRR parallel mechanism has more excellent dynamic performance when the first prismatic joint of each PPRR limb is chosen as an actuator. The motion/force transmissibility and dexterity are analysed by input/output transmission index and condition number of the Jacobian matrix, respectively. The results of performances comparison also proved that the actuating input combination of the first prismatic joints in PPRR limbs is the best one.

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