This paper presents a novel nonlinear sliding mode control scheme that combines on-line model modification, a nonlinear sliding mode controller, and a disturbance observer to solve the essential problems in spacecraft electromagnetic docking control, such as model uncertainties, unknown external disturbances, and inherent strong nonlinearity and coupling. An improved far-field model of electromagnetic force which is much more accurate than the widely used far-field model is proposed to enable the model parameters to be on-line self-adjusting. Then, the relationship between magnetic moment allocation and energy consumption is derived, and the optimal direction of the magnetic moment vector is obtained. Based on the proposed improved far-field model and the research results of magnetic moment allocation law, a fast-nonsingular terminal mode controller driven by a disturbance observer is designed in the presence of model uncertainties and external disturbances. The proposed control method is guaranteed to be chattering-free and to possess superior properties such as finite-time convergence, high-precision tracking, and strong robustness. Two simulation scenarios are conducted to illustrate the necessity of modifying the far-field model and the effectiveness of the proposed control scheme. The simulation results indicate the realization of electromagnetic soft docking and validate the merits of the proposed control scheme. In the end of this paper, some conclusions are drawn.

中文翻译：

---

基于干扰观测器的航天器电磁对接非奇异终端滑模控制

本文提出了一种新颖的非线性滑模控制方案，该方案结合了在线模型修改，非线性滑模控制器和扰动观测器，以解决航天器电磁对接控制中的基本问题，例如模型不确定性，未知外部扰动和固有干扰。强烈的非线性和耦合。提出了一种改进的电磁力远场模型，该模型比广泛使用的远场模型更为精确，以使模型参数能够进行在线自调整。然后，推导了磁矩分配与能量消耗之间的关系，并获得了磁矩矢量的最佳方向。基于提出的改进的远场模型和磁矩分配定律的研究结果，在存在模型不确定性和外部干扰的情况下，设计了一种由干扰观测器驱动的快速非奇异终端模式控制器。所提出的控制方法保证无抖动，并具有有限的时间收敛，高精度的跟踪和强大的鲁棒性等优良特性。进行了两个仿真场景，以说明修改远场模型的必要性和所提出的控制方案的有效性。仿真结果表明了电磁软对接的实现，并验证了所提出控制方案的优点。最后，得出了一些结论。所提出的控制方法保证无抖动，并具有有限的时间收敛，高精度的跟踪和强大的鲁棒性等优良特性。进行了两个仿真场景，以说明修改远场模型的必要性和所提出的控制方案的有效性。仿真结果表明了电磁软对接的实现，并验证了所提出控制方案的优点。最后，得出了一些结论。所提出的控制方法保证无抖动，并具有有限的时间收敛，高精度的跟踪和强大的鲁棒性等优良特性。进行了两个仿真场景，以说明修改远场模型的必要性和所提出的控制方案的有效性。仿真结果表明了电磁软对接的实现，并验证了所提出控制方案的优点。最后，得出了一些结论。仿真结果表明了电磁软对接的实现，并验证了所提出控制方案的优点。最后，得出了一些结论。仿真结果表明了电磁软对接的实现，并验证了所提出控制方案的优点。最后，得出了一些结论。