Abstract: Based on five degree-of-freedom (5-DOF) of parallel manipulator of 4-UPU, a novel spatial parallel manipulator of 4-UPU/PPS is deduced. From the theory of screw, we show that this manipulator possess 2T2R (two-translational and two-rotational) DOFs, and establish an equation of position. Since forward positional
analysis of parallel manipulator is difficult, based on the constrained length of limps, we build an unconstrained nonlinear optimization fitness function of this manipulator. The problem of forward positional analysis is thus converted to a multi-objective optimization problem that can be solved with the dynamic variable-weighting
multi-objective particle swarm optimization (PSO) algorithm which seeks the global minimum of the nonlinear optimization function. The result of 20 groups of random forward positional analysis is consistent with the actual position and orientation. Therefore the problem of forward positional analysis is solved using the
proposed parallel manipulator.