Electromagnetic Mechanism Design And Control For Space Docking

At present, the space docking technology based on traditional thrusters has some inherent problems such as plume contamination, docking impact and propellant consumption, etc. However, the space docking enabled by the electromagnetic force/torque can not only solve these problems effectively, but also has synchronous, continuous, reversible and non-contacting control capability, having wide applications in future. Against the background of space electromagnetic docking, this paper carries out electromagnetic mechanism design for ground experiment and micro- and nano-satellite. Concentrating on two-dimension and three-degree-of-freedom electromagnetic docking, a trajectory tracking Active Disturbance Rejection Control is investigated, and then ground preliminary experiment is carried out.Firstly, based on the fundamental electromagnetic theories and Maxwell platform, we optimize the electromagnetic mechanism design in materials, geometric models, iron cores' size, number of turns, wires' radius, and magnetic path by comprehensively considering the mechanism mass, power dissipation and mechanism size. Finally, two electromagnetic mechanisms using the general-conduct material, one for ground experiment and the other for micro- and nano-satellite, are obtained. The former can satisfy the design requirements and gather the magnetism obviously, and the latter is light in mass, small in size, and low in power dissipation.Secondly, the open-loop characteristics of electromagnetic docking and trajectory tracking Active Disturbance Rejection Control are investigated. The results of the open-loop characteristics indicate that two electromagnetic mechanisms can achieve self-alignment and adsorption by the mere force/torque produced by themselves, without active control. Then based on the self-docking characteristics and considering strong nonlinearity and coupling of electromagnetic docking, a trajectory tracking control strategy, which is formed by utilizing feedback linearization method and Active Disturbance Rejection Control(ADRC) method, is constructed. The dynamic model of electromagnetic docking is linearized by using feedback linearization method, and then a trajectory tracking Active Disturbance Rejection Control law is designed based on the linear model by using the Active Disturbance Rejection Control method. The simulation results indicate that the ADRC-based control law, capable of solving the control problems of electromagnetic docking effectively, such as strong nonlinearity, coupling, measure noise, and model uncertainty, can satisfy the robust control requirement of electromagnetic docking.Finally, an electromagnetic docking ground preliminary experiment is implemented based on the air bearing table. The principle of electromagnetic docking and the availability of the control law are validated.In conclusion, this paper studies electromagnetic mechanism design and trajectory tracking control problems for space docking. The resulted design concept and schemes, control strategy and method can provide ready reference for future engineering work.