External Force Estimation Method for Robotic Manipulator Based on Double Encoders of Joints

Abstract

This paper proposes a novel external force estimation method for robotic manipulator based on double encoders of joints. The actuator structure with double encoders used in this method is presented and discussed in detail. The principle of utilizing the difference between the positions of double encoders to represent the joint actual torque is analyzed and discussed later. Then, the friction torque model is identified in consideration of velocity, temperature and load torque step by step to achieve the final comprehensive friction torque model. After the external torque of the joint is estimated by subtracting dynamic torque and friction torque from the output toque of motor based on the difference between the positions of double encoders, the external force of the manipulator is derived. Two validation experiments are carried out to measure the estimated external force under different conditions including static state and dynamic state. The results show that the method based on double encoders of joints is capable to estimate the external force of the robotic manipulator.