On-Orbital Collaborated Control Method Research Of Small Satellite Swarm

Usually,for replacing the single and complex large satellite to accomplish the space mission,the small satellite swarm system is requested to intercommunicate and collaborate with each other.In the present and the future,the small satellite swarm system has a broad prospect of application in many fields,such as reconnaissance survey for the ground,deep space exploration,scientific experiment and military reconnaissance.The on-orbital coordination control technology of the small satellite swarm is a necessary guarantee for completing various space missions.However,due to the complexity of satellite structure and the terrible space environment,a series of problems will be encountered,such as incomplete communication,fuel loss,uncertainty of system parameters,external interference,actuator failure,and so on,thus,it is difficult to achieve the high-performance control index.In this paper,the on-orbital coordination technology of the small satellite swarm is discussed.By using the theories of consistency,optimal control,finite-time control,sliding mode control and neural network,the cooperative control algorithms via the distributed control structure are respectively researched.The main research contents of this paper are composed of the following three aspects:(1)Research on the configuration coordination control algorithm of the small satellite swarmAiming for the configuration coordination problem of the small satellites swarm,considering the harmful influence brought by fuel consumption for the control system,a cooperative control algorithm on the basis of fuel optimization is proposed.Firstly,for the rigidly-configuration coordination problem,by using the continuous and smooth hyperbolictangent function,a non-singular finite-time stable sliding mode surface is proposed.Then,with the assumptions that the upper boundary of external disturbing force can be obtained and the satellite mass is constant,a control algorithm in the sense of finite-time stability is developed.On this basis,fuel consumption is further selected as the performance index and a cooperative control scheme mixing Legendre pseudo spectrum method and adaptive finite-time sliding mode(LPM-AFSM)oriented on the loosely-configuration coordination problem is proposed.In this scheme,Legendre pseudo-spectrum method is firstly utilized to find the optimal satellite trajectories and the open-loop control quantities with the given loose positional constraints,and then,an adaptive finite-time sliding mode feedback controller is introduced to compensate the optimal open-loop one with considering the external disturbancing forces and the modeling errors,thus,to ensure the control accuracy of the configuration.(2)Research on the attitude coordination regulating algorithm of the small satellite swarmAiming for the attitude coordination regulating problem of small satellite swarm and in view of the fact that the upper bound of the convergence time by using the finite-time control strategy is related to the initial states of the system,a distributed control algorithm in the sense of fixed-time stability is proposed.Firstly,with the situation that only partial members in the system can obtain the desired attitude,a distributed state observer is introduced for each member to obtain the estimation of the desired attitude,which is further adopted as the tracking control command.Then,in view of the external disturbancing torques,in order to improve the robustness and control accuracy of the system,a disturbancing observer is introduced for exactly tracking the disturbancing torques.Finally,on the basis of the state observer and the disturbancing observer,a tracking controller via the terminal sliding mode technology is designed to achieve the goal of regulating the satellite members’ attitudes to be consistent with the desired one.By using the theory of the fixed-time stability,the convergences of the state observer,the disturbancing observer and the tracking controller will be sequentially analyzed and it will be proved that the proposed control scheme is fixed-time stable in theory.(3)Research on the attitude coordination tracking control algorithm of the small satellite swarmAiming for the attitude coordination tracking problem of small satellite swarm,in view of the unknown inertia parameters,external disturbances,the uncertain flexible dynamics and the actuator failure of the system,a fault-tolerant tracking control algorithm via the adaptive finite-time sliding mode and the radial basis function neural network minimum learning parameter method(RBF-MLP)is proposed.Firstly,with the rotation matrix-based attitude error model,a fast terminal nonsingular sliding surface is proposed for insuring the tracking errors can converge in finite time and the tracking errors is always constrained in the required range;Then,in view of the unknown inertia parameters and the uncertain system dynamics,by using RBF neural network minimum learning parameter method and adaptive method,a finite-time cooperative tracking controller is subsequently designed.Finally,the actuator failure on orbiting is further introduced and a fault-tolerant control algorithm is proposed,thus,to make the control system to keep the finite-time stability under the condition of partial failure and random drift failure of the actuator.