OPTIMIZED DESIGN OF PKM STRUCTURE FOR APPLICATION ON HYBRID MACHINE TOOLS

Abstract

With modern CAD/CAM systems, one can greatly improve machining capacity. Design efforts are kept intact if CNC machine tools can accommodate complex spatial shaping movements. Because of the need for dexterity and good force/velocity transmission coefficients throughout the entire working space, today's machine tools have a kinematic structure very close to robots, especially parallel mechanisms of the PKM (Parallel Kinematic Mechanism). This article presents an optimal design method for the PKM structure based on the improved Atlas method. The use of two dimensional and non-dimensional design spaces combined with the optimal spread spectrum technique allows determining the characteristic dimensions of the structure. Because the multi-objective problem takes the quality criteria as force/velocity transmission coefficient, the resulting structure, despite having a small working area typical of a parallel robot, has outstanding kinematic capabilities compared to other options. This design method has the potential to be applied to designs that require the force/velocity conversion ratio to be optimized at the same time as the transmission coefficient based on the pressure angle when designing complex parallel mechanisms.