Dragging Teaching Method without Torque Sensor for Robot Based on Elastic Friction Model
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    Abstract:

    Through the external torque observer based on generalized momentum and the admittance control scheme, the robotic dragging teaching without torque sensor was realized, in which the elastic friction model was used to estimate the joint friction torque, and the friction estimation value of the joint starting stage was planned. Based on the dynamics model and motion information of the robot, an external torque observer based on generalized momentum was established to observe the external torque exerted by the operator on the robot. Admittance control scheme was adopted to generate the joint motion trajectory according to the observed external torque, and the dragging teaching robot was realized. The elastic friction model was used to model the friction of the joint, and the Stribeck friction term was introduced into the model to estimate the friction torque of the joint at low speed and static state. In order to solve the difficulty of dragging in the stationary state of joint, the friction estimation of the joint starting stage was planned, and the joint driving torque was also increased temporarily, so as to realize the easy drag of the joint. Meanwhile, the starting planning scheme did not affect other movement stages of the robot joints. Experiment results showed that the control scheme can effectively realize the dragging teaching of industrial robot without torque sensor. At the same time, the starting planning scheme can effectively reduce the external torque and time of joint starting stage. The estimated torque of more than 26N·m was generated in the starting stage. The starting time of the joint can be reduced by 70% compared with the unused starting planning scheme.The joint had a certain antiinterference ability in the starting stage.

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History
  • Received:July 24,2018
  • Revised:
  • Adopted:
  • Online: January 10,2019
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