用安全约束强化模仿学习,实现航天器近距离操作的实时可靠控制。
Safety-Guaranteed Imitation Learning from Nonlinear Model Predictive Control for Spacecraft Close Proximity Operations
- 结合控制屏障函数与李雅普诺夫函数设计安全高效的神经策略训练方法。
- 在真实仿真中实现安全轨迹跟踪,计算开销仅为专家算法的1/3。
- 适合需要高安全性与实时性的在轨服务任务,如空间站维护与对接。
本文提出一种安全保证、运行高效的航天器近距离操作模仿学习框架。利用控制屏障函数(CBF)提供安全证书,控制李雅普诺夫函数(CLF)保障稳定性,统一应用于数据生成、训练和部署阶段。首先,非线性模型预测控制(NMPC)专家通过施加CBF约束生成安全参考轨迹;其次,采用新型CBF-CLF启发损失函数与课程加权的DAgger式采样,提升数据效率并减少在线安全滤波干预;第三,在部署阶段,通过轻量级单步CBF-CLF二次规划对学习控制输入进行最小修正,确保硬性安全约束满足且促进系统稳定。在包含球形避让区绕飞与圆锥形接近走廊最终接近的欧空局合规任务中,基于Basilisk高保真仿真平台验证了该方法的有效性,其在非线性动力学与扰动下仍保持稳定收敛与严格安全约束遵守,任务性能接近NMPC专家,同时显著降低在线计算开销。运行时分析表明该方法可在商用处理器上实现实时运行,支持在轨安全任务的星载部署。
原文摘要 · Abstract (English)
This paper presents a safety-guaranteed, runtime-efficient imitation learning framework for spacecraft close proximity control. We leverage Control Barrier Functions (CBFs) for safety certificates and Control Lyapunov Functions (CLFs) for stability as unified design principles across data generation, training, and deployment. First, a nonlinear Model Predictive Control (NMPC) expert enforces CBF constraints to provide safe reference trajectories. Second, we train a neural policy with a novel CBF-CLF-informed loss and DAgger-like rollouts with curriculum weighting, promoting data-efficiency and reducing future safety filter interventions. Third, at deployment a lightweight one-step CBF-CLF quadratic program minimally adjusts the learned control input to satisfy hard safety constraints while encouraging stability. We validate the approach for ESA-compliant close proximity operations, including fly-around with a spherical keep-out zone and final approach inside a conical approach corridor, using the Basilisk high-fidelity simulator with nonlinear dynamics and perturbations. Numerical experiments indicate stable convergence to decision points and strict adherence to safety under the filter, with task performance comparable to the NMPC expert while significantly reducing online computation. A runtime analysis demonstrates real-time feasibility on a commercial off-the-shelf processor, supporting onboard deployment for safety-critical on-orbit servicing.
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