Abstract: A novel 2UPR+SPR parallel manipulator (PM) is proposed. The two RPU legs of this PM provide four constraints whereas two of them are overconstraints due to the particular arrangement of the joints in RPU legs. The UPU leg provides one constrained force for this PM. The velocity constraint equation of this PM is established, and based on this, the degree of freedom of this PM is analyzed. The geometric constraint equations of this PM are established, the independent motion parameters which express the pose of mechanism end are determined, and the coupling relations of the pose, velocity and acceleration of the platform on the mechanism are derived. The inverse kinematics, velocity and acceleration of this PM are solved, and the detailed kinematics model of RPU and UPU type leg is established. The dynamics model is established on the basis of the principle of virtual work and the kinematics model of this PM, and the simulation of mechanism dynamics is implemented by using Matlab software. The simulation results testify the validity of the analytic model. The analytic method for this PM is fit for other over-constrained PMs.

Key words: Dynamics, Geometric constraint, Jacobian matrix, Parallel manipulator