A 3D Path Following Control Scheme for Robot Manipulators

We describe a novel path following control scheme for robot manipulators where constant tool velocity of travel on a surface is desirable. The path following scheme is applicable to general situations where the surface geometry is typically given in terms of measured data from a sensor. Considering the measured data points as control points, we utilize a cubic spline interpolation to generate a closed-form geometric description for the 3D path. Since joint velocity control is quite common in many industrial robots and most surface finishing tasks require travel with constant velocity along the path, we consider a 3D kinematic model for the end-effector with control inputs as rate of change of orientation and translational velocity that is locally tangent to the surface along the path. By utilizing a path variable and the tangent vector along the path, we formulate a converging path as the path that is traversed from a given robot end-effector position to the desired path and subsequent travel on the desired path on the surface. To evaluate the performance of the scheme, we have conducted a number of real-time experiments on a six degree-of-freedom industrial robot for several paths which can be employed for sanding of structures or deburring of large industrial cast parts and gears. Copyright (C) 2020 The Authors.