A Symmetrical Arrangement Strategy based Real-time Toolpath Planning Method for A 5-DoF Fully Parallel Machining Robot

Abstract A 5-DoF fully parallel machining robot (PMR) with attitude coupling motion property has the potential to realize the high-efficiency and high-quality machining of complex parts with curved surfaces. From the perspective of mechanism, this kind of 5-DoF fully PMR can achieve no singularity in the workspace after optimum design, so the mobile platform can be adjusted to an arbitrary orientation directly and flexibly. In order to give full play to the above mechanical characteristics, the idea of planning orientation path in unit spherical coordinate system was proposed in our previous work, and then the orientation adjustment efficiency was improved. But the toolpath continuity and calculation simplicity remain to be solved. In light of this concern, the constraint equations to ensure the continuity between two adjacent B-splines are established, and the configuration of control points that can ensure the controllable curvature is derived. On this basis, a symmetrical arrangement strategy that generates shape limits for fitted B-splines to achieve high-order continuity is proposed, and a toolpath planning method is established accordingly. To reduce computational complexity in the feedrate scheduling stage, a linear constraints system is adopted to calculate the feedrate of each point, and the feedrate calculation and interpolation are conducted simultaneously to generate the motion trajectory in real-time. The trajectory planning of S-shaped toolpaths is conducted using the proposed method and the commercial ISG CNC kernel respectively. The comparison results show that the proposed method can effectively improve the motion efficiency, the complexity of calculation, and the fluctuation of feedrate and acceleration. This study provides a more efficient and effective trajectory planning method and is of great significance to the further development of the 5-DoF PMR.