Nonlinear Control of Spacecraft Electromagnetic Docking with Modified Far-field Model

Compared with traditional docking systems, spacecraft electromagnetic (EM) docking has many distinct advantages, such as no propellant consumption, renewable energy, continuous and reversible controllability. However, the EM force exact model cannot be integrated analytically, making it difficult to design the control system, and the error of EM force far-field model increases rapidly with a decreasing relative distance of two coils. In addition, strong nonlinearity and coupled characteristics exist in the EM docking dynamics. In response to these issues, a modified far-field model which has a larger range of application is presented and an EM docking control strategy by combining feedback linearization and PD controller is proposed. Results indicate that the method proposed in this paper can reduce the far-field model error effectively, and the tracking performance of the docking trajectory is insured.