A Novel Path Following Scheme for Robot End-Effectors

In this paper we describe a novel path following scheme for robot end-effectors that is particularly suitable for robotic surface finishing operations where constant velocity of travel on the surface is desirable. The scheme is applicable to general situations where the path is typically given in terms of measured data from a sensor, and also to paths that are specified in terms of analytical curves (circular or ellipsoidal). Considering the given data points as control points, we utilize cubic spline interpolation to generate a closed-form geometric description for the path. Since 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 kinematic model for the end-effector with control inputs as rate of change of orientation and translational velocity. By utilizing a path variable and the tangent vector along the path, we describe the complete path as the path that is taken from the initial robot end-effector point to the desired path and subsequent travel on the desired path. To evaluate the performance of the scheme, we have conducted a number of real-time experiments on an industrial robot for circular paths and for paths generated for gear deburring and chamfering, and results from those experiments will be discussed.