Abstract
The flexibility of the robot assembly process is critical, and a robot assembly system that is not flexible may damage the workpieces. Most researchers make the assembly process flexible by installing a six-dimensional force/torque sensor at the end of robots, but doing so will result in an increase in the costs of the robotic assembly system. To this end, this paper proposes an external force/torque calculation algorithm based on dynamic model identification to replace the six-dimensional force/torque sensor; the algorithm can reduce the costs while achieving a flexible assembly. In this paper, the impedance model of the environment and the dynamic model of the robot with friction are unified. Based on the unified model, the virtual contact surface is proposed to optimize the assembly. To ensure the accuracy of the assembly, the compliant control method of this paper uses the PD-based position control as the control inner loop and the impedance control as the control outer loop. To verify the accuracy of the compliant control method, a 6-DOF series collaborative robot which is developed in our laboratory is used to complete the peg-in-hole assembly experiment. The experimental results show that the algorithm has good flexibility and positional accuracy.
Highlights
With the development of the 3C industry which stands for Computer, Communication and Consumer Electronic, the demand for its products is constantly increasing as well
This paper proposes a compliant control strategy without a force/torque sensor (FTS) to make the collaborative robot have human-like flexibility in completing the assembly tasks
This paper proposes an active compliant control method that ensures the flexibility of the robot to the external environment without the need to install an external force/torque sensor
Summary
With the development of the 3C industry which stands for Computer, Communication and Consumer Electronic, the demand for its products is constantly increasing as well. The flexibility of the robot in the assembly is crucial, and an inflexible robot may damage the assembled product To this end, this paper proposes a compliant control strategy without a force/torque sensor (FTS) to make the collaborative robot have human-like flexibility in completing the assembly tasks. F. Zeng et al.: Force/Torque Sensorless Compliant Control Strategy for Assembly Tasks Using a 6-DOF Collaborative Robot high flexibility of the robot. Chan and Liaw [19] and Krüger et al [20] apply impedance control to robot assembly Their method is to feed back the contact force between the robot end-effector and the assembled component in order to achieve flexible assembly. If we are not considering the singularity of the robot, from (6), we can obtain the mechanical impedance Z in the frequency domain by
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