Nonlinear control of space electromagnetic docking

The space electromagnetic docking avoids the inherent shortages of the space docking based on thruster.Such shortages include propellant over consumption,plume contamination and docking impact.Electromagnetic docking devices are of high ratio of performance to cost,and will be widely applied to small satellites in the future.To deal with the strong nonlinearity in the control of space-electromagnetic docking,we employ feedback linearization and the PD control method.First,the control model is linearized based on the feedback linearization theory,and the feasibility of linearization is analyzed according to the characteristics of the electromagnetic docking.Secondly,on the basis of the linearized model,the path tracking problem is transformed to a problem of error stabilization,for which a linear control law is developed by using the PD control and the extended Kalman filter.Finally,the nonlinear space-electromagnetic docking simulation is performed and the results are analyzed,taking into account the additional electromagnetic force model error and the J2 term of the gravitation.Theoretical research and numerical simulation analysis show that the strong nonlinearity of the electromagnetic docking can be handled by this combined control method,and a high robustness to the external disturbance can be achieved.