| Electromagnetic manipulation of spacecraft is a new technology for on orbit service.The three orthogonal superconducting coils are installed on the spacecraft to generate electromagnetic force in any direction to control the relative motion between the spacecraft.Compared with the traditional inertial thrust,the electromagnetic force between spacecraft has the advantages of no propellant consumption,continuous,reversible,and no plume pollution.It has broad application prospects in the fields of earth observation and space exploration.However,the electromagnetic force is generated between any two energized coils,which makes the analysis of the dynamics of electromagnetic control of multiple spacecrafts extremely complicated.To solve this problem,this paper designs a kind of current frequency/phase modulation method to simplify the model.Based on this,the problems of solving magnetic moment equations,spacecraft position control considering input delay,spacecraft attitude control and angular momentum management are studied.(1)A simple harmonic current is passed through the coil,and by designing the current frequency and phase of each spacecraft in the cluster,the electromagnetic force is decoupled(the integral is approximately 0)or the effect of the electromagnetic force is maximized between any two spacecraft(Maximum integration).So each spacecraft can selectively interact with only some of the spacecrafts in the cluster,which simplifies the dynamic model;from the perspective of reducing AC energy loss and easy phase control,the minimum frequency design method is given.(2)Using the homotopy continuation method to solve the magnetic moment equations,first,preprocess the equations is done to facilitate numerical solution;then,the homotopy equations are constructed,and the homotopy path tracking algorithm is designed;a numerical example with 3 electromagnetic spacecrafts is studied and the magnetic moment solution is obtained.(3)Considering the input time delay caused by electromagnetic induction and solving the magnetic moment equations,and assume it as a known constant time delay,at the same time,the error of the electromagnetic force model and the existence of environmental interference is considered.The relative position control problem is modeled as a linear uncertain system,the prediction method is used to compensate the time delay,and a sliding mode control strategy based on time delay compensation is designed.The effectiveness of the control strategy is verified by numerical simulation.(4)Considering the existence of environmental disturbance torque,an adaptive sliding mode control strategy is designed for attitude control;aiming at the accumulation of angular momentum caused by inter-satellite electromagnetic torque,the effect of the geomagnetic field on the unloading of angular momentum is analyzed.And the method of choosing the maneuvering window within 24 h has realized the efficient unloading of angular momentum.Base on this,an angular momentum management method is designed;the performance of the control strategy and the efficiency of the angular momentum unloading method are verified by numerical simulation. |
