Hybrid non-fragile H_∞ control for spacecraft electromagnetic docking with poles assignment constraints

To address the challenges of complex constant and periodic disturbances, coexisting additive and multiplicative gain perturbations, and maximum electromagnetic force constraints in spacecraft electromagnetic docking along an elliptical orbit, this paper proposes a non-fragile H_∞ control strategy based on regional poles assignment. First, the relative dynamics model and an electromagnetic force model for electromagnetic docking are established. Then, to proactively regulate the dynamic response of the closed-loop system, a theorem for solving the gains of the H_∞ non-fragile controller that places the closed-loop poles in a specified linear matrix inequality region is derived and rigorously proved. Furthermore, by integrating H_∞ performance criteria, a multi-objective controller design framework that ensures both robustness and non-fragility is constructed. Numerical simulations demonstrate that the proposed controller achieves high-precision soft docking under the aforementioned disturbances and gain perturbations while complying with the maximum electromagnetic force constraint. The results validate the feasibility and effectiveness of the proposed approach.