A Novel Robotic Multiple Peg-in-Hole Assembly Pipeline: Modeling, Strategy, and Control

Owing to the increased complexity of contact state, compared with the problem of robotic single peg-in-hole assembly, little research and few efficient solutions are currently available for the robotic multiple peg-in-hole assembly, particularly when the number of peg-hole pairs exceeds three. For this reason, a novel robotic multiple peg-in-hole assembly pipeline is proposed in this article. Specifically, an equivalent peg-hole model is established first to simplify and analyze the process of the multiple peg-in-hole assembly. Then, using the model, an assembly strategy based on instantaneous center of rotation (ICR) planning is developed to improve the force tracking and speed performance. Finally, two controllers based on the ICR, which can be called the ICR controller and the variable angular velocity controller, are designed to further enhance the assembly stability. Comprehensive experiments are conducted on four different sets of high-precision peg-hole pairs, with each set having seven pairs of pegs and holes distributed nonuniformly. Experimental results show that the hole insertion can be completed within 18-24 s while controlling the assembly forces within 20 N, which demonstrates the effectiveness of the proposed assembly pipeline. In addition, the comparative results confirm the ability of the proposed controllers to control the assembly forces and enhance the assembly stability.