Electromagnetic Detumble Method For Uncontrolled Satellite Based On The Eddy Current Effect Of Rotational Magnetic Field

The increasing amount of space debris left in space pose a great hazard to the operational satellites and active debris removal(ADR)must therefore be conducted to ensure the safety of the future spacecraft.Space debris,such as upper stages of rockets and defunct satellites,becomes an uncooperative tumbling target after losing its attitude control and communication ability and floats freely on orbit.Due to the environmental perturbation torque and the residual angular momentum prior to the object's end of mission,a tumbling motion can occur in an uncooperative target and contacting with a tumbling target may be coupled with collision risk.Therefore,a detumble phase is preferred to damp the rotation of space debris before capture and removal to ensure the safety of the ADR mission.How to realize the detumble before capture becomes a key problem to be solved.Based on the kinematics analysis of typical space debris,including upper stages of rockets and defunct satellites,a noncontact electromagnetic detumble method is proposed to damp the tumbling motion of the target.The damping effect induced by the relative rotation between the magnetic field and the target has been investigated.The dynamics model of the detumble process is established and the control strategy of the electromagnetic end effector is also derived.A three degree of freedom ground experimental setup has been built to verify the three dimensional electromagnetic detumble of a tumbling target.According to the conducting surface structure and kinematics of an uncooperative target,a noncontact electromagnetic detumble method has been proposed based on the eddy current effect between the rotating source magnetic field and the conducting target surface.The despinning torque opposed to the rotation direction of the target is induced when the end effector is parallel to target surface.Moreover,a restoring torque is induced by the tilt air gap resulting from the tumbling motion of target.The attitude of the target is stabilized under these coupled despinning and restoring eddy current torques.The dynamics model of the electromagnetic detumble system,including the chaser spacecraft,the electromagnetic detumble end effector on the robotic arm and the tumbling target spacecraft,has been built.The disturbance force and torque generated by the interaction between the geomagnetic field and the electromagnetic detumble source magnet during the detumble process are analyzed,and the guidelines for the structural design of the electromagnetic detumble source magnet to reduce the geomagnetic disturbance are determined.Considering the nonuniform air gap between the tumbling target surface and the source magnet,a three dimensional analytical model of electromagnetic force and torque under the nonuniform air gap is established.The three dimensional magnetic field distribution is analyzed based on magnetic vector and the mean radius assumption.The electromagnetic force and torque between the source magnetic field and the entire target are solved by means of the separation variable method.According to the electromagnetic force and torque for the nonuniform air gap,the key design parameters of the magnetic field source are discussed.The influences of working distance,structural parameters,arrangement of the source magnetization direction,excitation parameters on electromagnetic force and torque are also analyzed.The three dimensional theoretical model of the electromagnetic detumble force and torque helps to optimize the structural and select the excitation parameters of the electromagnetic detumble end effector.Based on the theoretical model of the electromagnetic detumble force and torque and the designed end effector,a detumble and despin combined method is put forwarded to deal with the manipulator tracking limitation for target with high tumbling rate and the divergence of target nutation for target with high spinning rate.The variations of the relative attitude,distance,and the nutation angle during electromagnetic detumble are analyzed.The required base reaction force and torque are analyzed.The influence of the end effector tracking error and nutation angle identification error of the target are discussed.The influence of the asymmetric inertia on the detumble process is discussed and the effectiveness of the proposed control strategies to targets with different tumbling rates are verified by the simulation.To experimentally verify the nutation tracking control strategy for targets with high spinning rate and the on off control strategy for target with high tumbling rate,a three degree of freedom air bearing experimental setup is built to simulate the tumbling motion of the target.Firstly,the target is noncontact spinned up to the spinning and tumbling states by the eddy current torque generated by the rotating magnetic field.Then,the on off detumble control and nutation tracking control are applied to the tumbling and spinning target,respectively.Then,the influences of the relative distance,the initial rotation velocity of the target and the excitation parameters of the end effector on the detumble process are analyzed.Finally,the effectiveness of the electromagnetic detumble method for the target with asymmetric inertia properties is also verified.This provides a reference for the practical application of electromagnetic detumble method by using a rotating source magnetic field.