Kinematic analysis and dimensional optimization of a 2R2T parallel manipulator

Abstract

[EN] The need of a device providing two-translational and two-rotational movements led us to design a 3UPS-1RPU parallel manipulator. The manipulator consisted of a mobile platform connected to a base through one central leg and three external legs located at the same radial distance. By studying different locations of the legs anchoring point, we improved the first layout design, yet not the optimal one. On this basis, this paper focuses on the optimal dimensional design of the manipulator. To this end, we put forward the kinematics equations of the manipulator in accordance with the anchoring points coordinates. Through a numerical approach, the equations allowing to find the manipulator workspace are developed. Also, we find a global manipulability index using a local dexterity measure. The latter index serves as an optimal function. The optimization process considers joint constraints. Thus, we built a nonlinear optimization problem solved through sequential quadratic programming algorithms. We start by optimizing only a small set of parameters rather than the entire set, which gives us insights into the initial guess to optimize using the entire set. Findings show that the optimal design approach improves the dexterity of the manipulator and reduces the number of singular configurations while having almost the same workspace as the original layout.