Bézier Curve Based Trajectory Generation and Nonlinear Friction Compensation for Feed Drive Contouring Control

Abstract

Generation of motion trajectories is a crucial task in feed drive control for efficient manufacturing and energy saving. They have to be smooth enough to be traversable without violating systems constraints. Literary, a number of methods, such as spline parametric trajectories have been suggested for smooth trajectories generation. However, there are still many challenges left, for example, in order to smoothly track a spline parameterized trajectory the reference velocity as well as position have to be optimally planned, such that low-velocity should be used at the start and the end of the motion, as well as in all areas with high curvature. Additionally, mechanical systems experience friction forces which vary nonlinearly with velocities. Therefore, on implementing a smooth velocity profile, an appropriate friction compensator has to be considered to cancel out the effect of friction forces. In this study methods for generating smooth motion trajectories using quintic Bézier curves and smooth velocity profiles based on the altered bang-bang approach are proposed. A contouring controller with a feed forward friction compensator is applied in order to smoothly track the designed trajectory by canceling out the effect of friction forces. The performance of the proposed method was experimentally evaluated by comparing it with a conventional approach. Results have shown that the tracking performance can be greatly increased by reducing the average contour error by about 48 % without violating systems constraints.