Control of self-oscillations in contact interaction of a robot with a treated surface under nonlinear friction
The article considers the problem of position-force control of the «robot – tool – detail» system movement, which is typical for machining operations. The tool is installed in elastic suspension, which provides force sensing of the robot. The robot, in accordance with the technological task, moves at a certain speed along the surface with a predetermined pressure to it. The non-linear nature of friction under elastic suspension of the tool and a small (creeping) speed of movement of the robot along the surface can cause frictional self-oscillations in the system. This can lead to a non-uniform motion with short-term stops of the tool. In this article, we have investigated the conditions under which this effect occurs by use of mathematical and computer simulation methods. Furthermore, it is shown how the frictional self-oscillations can be suppressed by another nonlinear effect, vibrational (pulse) smoothing. The way of making this process adaptive within the framework of a regular control system by use of a logical switching device is proposed. In the future it is planned to use artificial neural networks for these purposes.