Optimization of a 3-PRS parallel manipulator based on interval analysis

This paper addresses the problem of mechanism optimization of the 3-PRS parallel manipulator, a mechanism consisting of a moving platform and a base platform connected by three serial PRS chains. In order to optimize the geometrical parameters, first the inverse kinematic of the 3-PRS parallel manipulator is analyzed and the requirement of specific workspace of 3-DOF independent motions is defined by satisfying the constraints of the actuator length. Then due to existence of the unexpected parasitic motions, the parasitic motions are expressed as the functions of the independent motions so that the evaluation of the actuator length only depends on the desired independent motions. Therefore an algorithm based on interval analysis is designed to optimize the design parameters. Interval-based optimization can provide almost all the solutions satisfying the requirement of the specific workspace. A numerical example of the optimization is presented and the comparison of two groups of design parameters is given to validate the effectiveness of the proposed interval-based optimization algorithm.