Flexible servo riveting system control strategy based on the RBF network and self-pierce riveting process

As more and more composite materials are used in lightweight vehicle white bodies, self-pierce riveting (SPR) technology has attracted great attention. However, the existing riveting tools still have the disadvantages of low efficiency and flexibility. To improve these disadvantages and the riveting qualification rate, this paper improves the control scheme of the existing riveting tools, and proposes a novel controller design approach of the flexible servo riveting system based on the RBF network and SPR process. Firstly, this paper briefly introduces the working principle and SPR procedure of the servo riveting tool. Then a moving component force analysis is performed, which lays the foundation for the motion control. Secondly, the riveting quality inspection rules of traditional riveting tools are used for reference to plan the force-displacement curve autonomously. To control this process, the riveting force is fed back into the closed-loop control of the riveting tool and the riveting speed is computed based on the admittance control algorithm. Then, this paper adopts the permanent magnet synchronous motor (PMSM) as the power of riveting tool, and proposes an integral sliding mode control approach based on the improved reaching law and the radial basis function (RBF) network friction compensation for the PMSM speed control. Finally, the proposed control approach is simulated by Matlab, and is applied to the servo riveting system designed by our laboratory. The simulation and riveting results show the feasibility of the designed controller. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00403-3