Mass Identification And Control Of Space Non-Cooperative Target

Space non-cooperative target is the space object that has no information exchange with other spacecraft,including the space debris,the failed satellite and the enemy spacecraft,etc.In recent years,with the development of aerospace technology and space security,the research of space non-cooperative target is becoming much more comprehensive,using space robot to capture space non-cooperative target is also becoming more common.In this paper,the mass identification of space non-cooperative target and the control of combined-body system including space non-cooperative target and operational spacecraft with flexible-joint manipulator is studied.Firstly,the operational spacecraft with flexible-joint manipulator captures non-cooperative target.The model of the operational spacecraft and the manipulator is discussed in detail.Then based on the Lagrangian analysis method,the dynamic model of the combined-body system in the inertial coordinate system is established.According to the vibration characteristic of the flexible-joint manipulator,the dynamic equations of the combined-body are linearized with small disturbance in the balance position of space manipulator.The mass of target is identified by using the vibration frequency of the flexible-joint manipulator capturing non-cooperative target.Numerical simulation results show that the proposed method is simple,feasible and accurate for the mass identification of space non-cooperative target based on the vibration characteristic of the flexible-joint manipulator.In order to study the control problem of the combined-body system capturing space non-cooperative target,this paper first ignores the joint flexibility of the manipulator and establishes the dynamic model of combined-body system.After the model is completed,the trajectory planning of the manipulator’s recovery process is described by using cubic polynomial function.Then the continuous system is discretized and the optimal control problem is transformed into a nonlinear programming problem.Finally,an open-loop optimal control method is proposed based on energy consumption performance index and time-energy consumption performance index.The simulation results show that the control method based on the optimal energy consumption performance index performs slowly,and the control method based on time-energy consumption performance index is more suitable for the engineering practice.To further study the control problem of the combined-body system with flexible-joint manipulator,the combined-body system can be divided into a slow changing subsystem representing rigid motion and a fast changing subsystem representing elastic vibration based on the singular perturbation method.Then the corresponding control laws are designed.The numerical simulation results show that the designed control laws can suppress the elastic vibration caused by flexible-joint manipulator in the motion control process of the combined-body.