Variable Parameter Admittance Control of Robot Based on a Virtual Force/Torque Sensor

Admittance control enables supple control of a robot through force-motion mapping, allowing robots to actively adapt to forces exerted by humans during interaction, which are typically collected through force sensors. In addition, since the requirements for admittance control parameters vary at different stages of the task, it is necessary to propose a variable parameter strategy to improve task success rate and efficiency. Therefore, this article proposes a variable parameter admittance control without force sensors. First, The performance of the three observers in terms of estimation accuracy, computational efficiency, and parameter tuning is compared, and the virtual force/torque (F/T) sensor is designed accordingly. Second, a variable parameter admittance control with virtual F/T sensor is proposed to reduce the robot’s recovery time after withdrawing the external force. The proposed method was verified on two robots with different degrees of freedom. The experimental results show that the estimated values of the virtual F/T sensor of both robots can follow the changes in the measured values. The variable parameter admittance control enables rapid response to external forces and improves work efficiency. Furthermore, the proposed method can complete the bearing assembly task.