Sensorless haptic control for human-robot collaborative assembly

This paper presents an approach to haptically controlling an industrial robot without using any external sensors for human-robot collaborative assembly. The sensorless haptic control approach is enabled by the dynamic models of the robot where only joint angles and joint torques are measurable. Accurate dynamic models of the robot in the presliding and sliding regimes are developed to estimate the external forces/torques, where the friction model is also explored. The estimated external force applied to the robot by an operator is converted to the reference position and speed of the robot by an admittance controller. In this research, adaptive admittance control is adopted to support human-robot collaborative assembly, naturally and easily, with accurate positioning and control for smooth movement. Moreover, torque-based commands are used to control the robot's assembly operations. Finally, the proposed approach is validated by a case study on assisting an operator during the collaborative assembly of a car engine. (C) 2020 CIRP.