Sensorless collision detection for safe human-robot collaboration

As there have been many attempts for human-robot collaborations, various solutions to collision detection have been proposed in order to deal with safety issues. However, existing methods for collision detection include the usage of skin sensors or joint torque sensors, and cannot be applied to robots without these sensors such as industrial manipulators. In this study we propose a sensorless collision detection method. The proposed method detects the collision between robots and humans by identifying the external torques applied to the robot. Without using extra sensors, we observed the joint friction model and motor current. We have formulated the friction model for the robot by using the dynamics of the robot and the observer based on the generalized momentum. In addition, formulation of the friction model and the identification scheme did not include any use of extra sensors. The performance of the proposed collision detection method was evaluated using a 7 DOF manipulator. The experimental results show that collision can be reliably detected without any extra sensors for any type of robot arm.