Motion-force Transmissibility Characteristic Analysis of a Redundantly Actuated and Overconstrained Parallel Machine

This paper presents a novel 1T2R three degrees of freedom redundantly actuated and overconstrained 2$$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{\rm{P}}\rm{RU}-\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{\rm{P}}R\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{\rm{P}}S$$P−RU−P−RP−SS parallel machining head ($$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{\rm{P}}$$P− denotes the active prismatic joint), which can construct 5-axis hybrid machine to complete high speed freedom surface milling for large complex structural components in aerospace. Firstly, based on the screw theory, the mobility of the proposed parallel manipulator is briefly analysed. Secondly, the kinematic inverse position and the parasitic motion of the parallel manipulator are explicitly expressed. Furthermore, motion-force transmission performance evaluation indices are derived in detail via an alternative approach based on the screw theory. More importantly, a simple method for quickly solving the maximum virtual power coefficient is proposed, and the motion-force transmission performance evaluation index is greatly improved. To evaluate the kinematic performance, its workspace is calculated. With numerical examples, performance distribution atlases of the manipulator are depicted visually. The corresponding results illustrate that the proposed parallel manipulator has better orientation workspace and superior motion-force transmission performance than the 2PRU-PRS parallel manipulator, which proves the validity and applicability of applying this manipulator as a machining head.