Adaptive friction compensation for synchronous force control of dual-servo riveting systems with high-energy nonlinear disturbance

In the aircraft industry, dual-servo riveting systems (DSRSs) face significant challenges in achieving high-performance synchronous force control due to nonlinear time-varying contact dynamics and complex friction disturbances. This paper proposes a novel synchronous force control architecture that integrates adaptive friction compensation (SFCwF) with nonlinear disturbance rejection to address these challenges. For the high-energy nonlinear loads generated during riveting process, the distributed friction characteristics of the DSRS ball screw powertrain are analyzed using Hertz contact theory, and a parametric friction model is subsequently established. To address parameter perturbations in the friction model induced by nonlinear loads, a dual-observer structure is designed based on the LuGre model to manage parametric uncertainties. Furthermore, a nonlinear disturbance observer (NDOB) is designed to mitigate unknown disturbances without requiring acceleration measurements. The Lyapunov theory analysis demonstrates that the proposed control approach guarantees asymptotic stability of the closed-loop system, with both tracking and synchronization errors converging to zero, even in the presence of parametric uncertainties. Experimental validations on a custom-designed DSRS platform indicate that the proposed strategy achieves not only superior synchronous force control performance but also consistent riveting quality, with deviations of ±0.06 mm in driven head height, ±0.075 mm in driven head diameter, and a sheet waviness of ±0.116mm, all of which significantly exceed acceptable quality thresholds.