The Statics And Dynamics Analysis Of A 4PUS/1RPU Parallel Manipulator With A Constrained Leg

Compared to the traditional serial robot mechanism, parallel mechanism has the advantages that larger stiffness to weight ratio, stronger load capacity, the error is not superimposed, the kinematics inverse is easier, but also has the disadvantages that the workspace is smaller, the structure is complicated, and so on. For the pallel mechanism with 6 dofs, like Stewart, Lower-mobility parallel mechanism with a central constraint chain has the advantages that its structure is simple, the decoupling is easy, it adapts widely use, low cost etc, and it receives attentions from industry and academic in these years.This paper pays attention on a parallel mechanism of 4 dofs with a central constrained chain-4PUS/1RPU. Firstly the Newton - Euler equations is used to derive the relationship of the mechanism'external forces and the active forces, the constrained force/torque applied by the central constraint chain, then we get the relationship matrix of external forces and active forces, passive force/torque, analyzes the geometric constraint which the constraint force/torque applied by the central constraint chain should follow, as to 4PUS/1RPU parallel mechanism, get the relationship matrix of the external forces and the active forces, the constrained force/torque of the mechanism under given location and position. Lastly, we analyze the active forces, the constrained force/torque of the parallel mechanism when the external forces is changed, draw out the simulation curve.This paper introduces the force and monent workspace of the parallel mechanism, that is, the force-moment capabilities of the mechanism on the fixed position workspace. We analyse the mechanism'fixed workspace under geometric constraint, use the analytical method to analyse the min-max force capabilities under prescribed moment and the min-max moment capabilities under prescribed force, then we use the MATLAB to simulate the force and moment workspace.The principle of virtual work is used to establish the rigid body dynamics model of parallel machine, then we solve the mechanism's inverse dynamic model, that is, solve the active forces under the given movement. The MATLAB is used to simulate the active forces when the mechanism translates under a fixed position and rotates un a fixed location, which provides reference for the mechanism'research on dynamics, control algorithms and Structural optimization.We establish the dynamic model under the task space which is suitable for control, then use the PD control algorithm, PD control algorithm with compensation of the central constraint chain, to simalate the mechanism under given movement. From the result, we find that the PD control algorithm with compensation of the central constraint chain is better, which provides reference for research on control algorithm of parallel mechanism with a central constraint chain.