6-DOF Spacecraft Tracking Control With Motion Constraints

With the rapid development of the aerospace industry,the demand for on-orbit tasks has become more diverse and complex.In the early days,space missions were carried out for cooperation objectives,subsequently followed by on-orbit operations for non-cooperative non-confrontation targets,and in the future non-cooperative confrontation targets may be controlled.The traditional spacecraft control methods is to separate the control strategy of its orbit and attitude,and can not show the relative motion relationship and influence between spacecrafts clearly.The spacecraft six-degree-of-freedom control method has a greater advantage than the traditional control method in the face of non-cooperative targets with high-speed maneuverability,unknown confrontational modes,and anti-sense characteristics.The premise of in-orbit operation for non-cooperative confrontational objectives is the effective control of the attitude and orbit of the spacecraft in such conditions,and potential motion constraints,such as line-of-sight constraints and near-path constraints,need to be considered throughout the process.Ultimately,the spacecraft can hover in a relative position in a specific position.This paper mainly focuses on the six-degree-of-freedom tracking control problem of spacecraft with different motion constraints,and carries out research on the integrated attitude and control strategy.The main research contents are as follows:For the six-degree-of-freedom tracking control problem of spacecraft,the six-degree-of-freedom relative kinematics model is firstly studied for the spacecraft,the definition of the relevant coordinate system is defined,and the spacecraft attitude motion model based on quaternion is briefly introduced.According to the introduced dual quadruple number and related computational properties and advantages,a six-degree-of-freedom kinematics model based on dual quaternion and a six-degree-of-freedom dynamic model of spacecraft based on dual algebra are established to obtain the six-degree-of-freedom phase of the rigid spacecraft.Some of the nonlinear system theory convenient for subsequent proof and reference is included at last.For the six-degree-of-freedom tracking control problem of spacecraft with line-of-sight constraint,firstly consider the tracking condition without motion constraint.For the spacecraft tracking control problem that needs to be completed,design a PD-like controller under the dual quaternion frame to ensure the tracking of space.It should be noted that the position and attitude of the device should be asymptotically converged to the desired position and attitude.Then mathematical analysis is carried out to realize the motion constraint and transformed into the framework of the dual quaternion.At the same time,a virtual approach path is designed to limit the final approximation for the sake of safety and possible subsequent arrest tasks.A reasonable artificial potential function for two kinds of motion constraints is designed and the properties of it are analyzed.A control strategy with potential function is provided and the stability of the whole system is proved.The motion constraint is achieved while achieving the desired state.Finally,the two controllers proposed in this section are compared by simulation experiments to verify the effectiveness and practicability of the controller.For the six-degree-of-freedom tracking control problem of spacecraft with near-path constraint,the detection capability of the target spacecraft needs to be summarized as close to the path constraint and clearly explained.Then,a new artificial potential function is designed in combination with the previously proposed line-of-sight constraint to ensure the motion constraint.Since the constraint is not a convex set,the local minimum needs to be analyzed.Then the control strategy is designed according to the potential function and the stability of the system is proved.Finally,the experimental simulation is given and compared with the PD-like controller to prove the effectiveness and relative advantages of the control strategy.