| With the development of the times,the complexity of space missions is also increasing.Some spacecraft with long mission cycle often need on orbit refueling technology to ensure long-term operation in space.In the process of attitude maneuver of liquid filled spacecraft for on orbit refueling service,the sloshing of liquid fuel in the tank will produce interference torque,which will affect the stability of attitude control of liquid filled spacecraft.In this paper,the anti-interference attitude maneuver control method and liquid sloshing suppression method of liquid filled spacecraft are studied by using sliding mode variable structure control as the main control method.The specific contents are as follows:Based on the equivalent spherical pendulum model,the attitude dynamics equation of a liquid filled spacecraft is established.Qualitative analysis shows that the main influence of liquid sloshing on attitude control of liquid filled spacecraft is that the parameters of moment of inertia are uncertain and additional disturbances are generated.It is concluded that the dynamic system of liquid filled spacecraft is a complex nonlinear system,which has the characteristics of strong coupling,underactuated and unmeasurable liquid sloshing state information.Given that the attitude maneuver process of liquid filled spacecraft is subject to the disturbance torque of solid-liquid coupling,and in order to solve the problem that the state information of liquid sloshing equivalent ball pendulum can not be measured,a sliding mode controller based on liquid sloshing observer is designed;The controller can ensure the stability of the closed-loop system.Considering the uncertain parameters and unknown disturbance torque in the attitude maneuver process of liquid filled spacecraft,the controller is constructed based on terminal sliding mode theory.By improving the sliding mode surface and introducing adaptive law to estimate the total disturbance,an adaptive nonsingular fast terminal sliding mode controller based on observer is designed,The finite time stability of the spacecraft system is realized.The controller shortens the convergence time,improves the control accuracy and suppresses the chattering of the system.Aiming at the difficulties of strong coupling and underactuated of liquid filled spacecraft system,the equivalent plane pendulum model of liquid filled spacecraft is derived by assuming that the liquid filled spacecraft only performs attitude maneuver on the plane;Based on the equivalent plane pendulum model of the liquid filled spacecraft,the controller is created by applying the idea of hierarchical sliding mode,and the active suppression of liquid sloshing during the attitude maneuver of the liquid filled spacecraft is realized.The designed controller is able to suppress the liquid sloshing effectively while completing the target attitude maneuver. |
