Tool collision detection in high-speed feeding based on disturbance observer

It is important to take countermeasures against tool collision to avoid serious damage to the machine tool. Though rapid collision detection is needed, the introduction of additional sensors to a machine tool is not desirable owing to cost, machine-tool stiffness, and failure rate considerations. In this study, a sensor-less tool collision detection method is proposed on the basis of the disturbance observer theory. It only uses the servo information of a ball-screw-driven stage and does not require external sensors. The proposed method successfully detects the collision between a tool and a workpiece in less than 3 ms with a feed rate of 50 m/min.