Feedrate profile generation with axis constraints using NURBS toolpaths for a Delta-KEOPS parallel kinematics machine

In numerical control feedrate profile defines the end effector or tool velocity tangent to the desired toolpath. By generating an appropriate feedrate profile smooth motion trajectories can be generated. Numerous papers propose a solution to this problem but most consider 3 and 5 axis cartesian machines. In this paper a computationally efficient feedrate profile generation algorithm is proposed for a Delta-KEOPS parallel kinematics machine with linear motor axes. The algorithm generates a feedrate profile for complex shaped toolpaths defined by Non-Uniform Rational B-Splines (NURBS) while respecting the limitations of velocity, acceleration and jerk in the machines axes. This is a difficult task due to highly nonlinear kinematics of the Delta-KEOPS machine and complex shaped toolpaths. The algorithm was implemented in a PC-based real-time controller. Experimental results are presented which verify the capabilities and computational efficiency of the presented method on an actual machine.