Abstract: A novel 4-DOF spatial and symmetrical 4-RUPaR parallel robot mechanism that can perform three-dimensional translations and rotation about z axis (3T1R) is presented. The principles that the mechanism can perform the above motions are analyzed by using screw theory, the degree of freedom of the mechanism is calculated, and the rationality of chosen input is discussed. The link-length of the mechanism is taken as the constraint condition to obtain the constraint equations, and nonlinear equations of position analysis are obtained. A unary transcendental equation for positive position analysis of the mechanism is deduced, and the adaptive mutation particle swarm optimization (AMPSO) algorithm is utilized to solve this equation. The closed equation of inverse solution of position and the expressions of velocity and acceleration are deduced. At last, numerical verification of the results of forward and inverse solutions is carried out. The result of forward solution is quite coincident with that of inverse solution. On the basis of the forward position solution analysis, forward solutions of velocity and acceleration of the example are analyzed.

Key words: Forward position solution analysis, Kinematics analysis, Parallel robot mechanism, Screw theory