Torque control based sensorless hand guiding for direct robot teaching

Abstract

In recent years, much research has been done to develop various direct teaching schemes, in which an operator directly teaches a robot by hand guiding instead of using a teach pendant. However, conventional direct teaching methods are usually sensor based, thus leading to an expensive solution. To deal with this problem, this study proposes a sensorless hand guiding method based on torque control. The dynamic model of a robot along with the motor current and friction model is used to determine the user's intention to move the end-effector of a robot instead of directly sensing the external force by the user. A friction torque observer is employed for the friction model identification. The proposed method was experimentally verified using a 6 DOF robot. The experimental results show that the proposed sensorless hand guiding scheme is quite useful for practical direct teaching although the sensitivity is slightly lower than the sensor-based approach.