Parameters identification of flexible joints with harmonic driver

In order to identify the key parameters of flexible joint model with harmonic driver, an off-line identification method by integrating several sensors is proposed. The key parameters can be identified by the experimental data of motor position sensors, current sensors and joint torque sensors. Firstly, the flexible joint model is established, which uses the flexspline as the output in the harmonic driver. Then, the motor torque coefficient is identified by running in forward and inverse directions with different loads. In the no-load condition, joint friction and motor friction are identified from the joint torque and motor output torque. Finally, the stiffness and damping parameters are identified by the knocking method, while the nonlinear relationship between stiffness and joint torque is obtained by progressively increasing the motor output torque under the condition that the joint position is hold. Several experiments are repeated, and the results show a high repeatability, which verifies the proposed method.