Research On Key Technologies Of Torque Estimation Of Robotic Joint With Harmonic Drive Transmission

In the flexible robot control system,the key component is the harmonic drive joint.The control of the harmonic drive joint includes the measurement of joint position,motion state observation,and the joint torque feedback measurement.The key technology is the output measurement of joint torque,which is related to the accuracy and stability of the whole robot system control.Therefore,the research on the joint torque output method of the robot with harmonic drive is of great significance.In recent years,the complexity and diversity of the working environment also put forward requirements for the stability and accuracy of the robot,especially the extreme temperature,humidity,radiation and other environments have higher requirements for the performance of the robot.At present,there are two main schemes for the research on the joint torque of harmonic drive robots:One method is to directly obtain torque measurements based on the torque sensor embedded in the joint outpu,and another solution is to indirectly estimate the torque based on external position encoders.Therefore,based on the consideration of system stability,assembly flexibility,and cost,this dissertation aims to propose an improved method for estimating the joint torque of robot with harmonic drive based on external position encoders to improve the accuracy of the output torque.The research work is mainly divided into the following aspects:Firstly,the structure and theoretical model of harmonic drive are analyzed.This dissertation introduces two kinds of dynamic models of the harmonic drive:basic dynamic model(ideal model)and dynamic model based on compliance and friction.The classical friction model and related filtering technology are introduced.Secondly,the dynamic model of the robot joint with harmonic drive is analyzed and established.According to the three main factors causing the nonlinearity of harmonic drive(compliance,nonlinear friction,and kinematic error),the corresponding models are discussed.The kinematic error model and the torque deformation model of wave generator and flex-spline based on compliance are established,and the relevant parameters are studied.Furthermore,an improved joint torque estimation method of the robot with harmonic drive is proposed.Based on the system model diagram of this research,improved friction model based on stribeck friction,the constructed dynamics model of the robot joint with harmonic drive,and the overall dynamic characteristics of the system,an improved system model is given.And the unscented Kalman filter(UKF)algorithm is used to estimate the joint torque.Finally,the relevant experimental platform is designed and built to verify the algorithm.Specifically:analyzing the structure of the experimental platform and the corresponding data acquisition process,designing two sets of comparative experiments under different input conditions,and the experimental results are analyzed to verify the effectiveness of the improved joint torque estimation method for the robot with harmonic drive proposed in this dissertation.