This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionl...This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionless form. Further, a decoupled PD controller is proposed, and the local stability of the controller is analyzed by linearization technique. Parametric studies of the dynamics and de-spin control of a massive target are conducted to characterize the dynamic process of de-spin with the proposed control law. It is shown that the massive target can be de-span by a single and small space tug with limited thrust within finite time. The thrust tangent with the tether de-spins the target while the thrust normal to the tether prevents the tether from winding up the target. The tether length has a positive contribution to the de-spin of a target. The longer tether leads to a faster de-spin process.展开更多
This paper proposes a fuel-optimal deorbit scheme for space debris deorbit using tethered space tug.The scheme contains three stages named respectively as dragging,maintenance and swinging.In the first stage,the tug,p...This paper proposes a fuel-optimal deorbit scheme for space debris deorbit using tethered space tug.The scheme contains three stages named respectively as dragging,maintenance and swinging.In the first stage,the tug,propelled by continuous thrust,tows deorbit to a transfer orbit with a tether.Then in the second stage,the combination of the tug and the debris flies unpowered and uncontrolled to a swing point on the transfer orbit.Finally,in the third stage,the tug is propelled at the swing point and the rotation speed of the tethered system increases such that the debris obtains enough velocity increment.The trajectory optimization of the first stage is established considering the total fuel consumption of the three stages,whereas the dynamic model is simplified for computation efficiency.The solution to the optimal problem is obtained using a direct method based on Gauss pesudospectral discretization.Then a model predictive controller is designed to track the open-loop optimal reference trajectories,reducing the states’deviations caused by model simplification and ignorance of perturbations.Furthermore,it is proved that the fuel-optimal swing point is the apogee of the transfer orbit.The paper analyzes the fuel consumption of a typical scenario and demonstrates effectiveness of the proposed deorbit scheme numerically.展开更多
A retrieval control strategy for failed satellite,which is connected to a servicing spacecraft by a tether,is studied.The Lagrange analytical mechanics based dynamics modeling for the system composed of a servicing sp...A retrieval control strategy for failed satellite,which is connected to a servicing spacecraft by a tether,is studied.The Lagrange analytical mechanics based dynamics modeling for the system composed of a servicing spacecraft,a tether and a failed satellite,is presented under the earth center inertia coordinate system,then model simplification is conducted under the assumption that the failed satellite’s mass is far smaller than the servicing spacecraft’s,meanwhile the tether’s length is far smaller than the size of the servicing spacecraft’s orbit.Analysis shows that the retrieval process is intrinsically unstable as the Coriolis force functions is a negative damping.A retrieval strategy based on only the tether’s tension is designed,resulting in the fastest retrieval speed.In the proposed strategy,firstly,the tether’s swing angle amplitude is adjusted to 45?by deploying/retrieving the tether;then the tether swings freely with fixed length until it reaches negative maximum angle–45?;finally,the tether is retrieved by the pre-assigned exponential law.For simplicity,only the coplanar situation,that the tether swings in the plane of the servicing spacecraft’s orbit,is studied.Numerical simulation verifies the effectiveness of the strategy proposed.展开更多
基金supported by the Discovery Grant(No.RGPIN-2018-05991)of the Natural Sciences and Engineering Research Council of Canada
文摘This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionless form. Further, a decoupled PD controller is proposed, and the local stability of the controller is analyzed by linearization technique. Parametric studies of the dynamics and de-spin control of a massive target are conducted to characterize the dynamic process of de-spin with the proposed control law. It is shown that the massive target can be de-span by a single and small space tug with limited thrust within finite time. The thrust tangent with the tether de-spins the target while the thrust normal to the tether prevents the tether from winding up the target. The tether length has a positive contribution to the de-spin of a target. The longer tether leads to a faster de-spin process.
基金supported by the National Natural Science Foundation of China(No.11772023)。
文摘This paper proposes a fuel-optimal deorbit scheme for space debris deorbit using tethered space tug.The scheme contains three stages named respectively as dragging,maintenance and swinging.In the first stage,the tug,propelled by continuous thrust,tows deorbit to a transfer orbit with a tether.Then in the second stage,the combination of the tug and the debris flies unpowered and uncontrolled to a swing point on the transfer orbit.Finally,in the third stage,the tug is propelled at the swing point and the rotation speed of the tethered system increases such that the debris obtains enough velocity increment.The trajectory optimization of the first stage is established considering the total fuel consumption of the three stages,whereas the dynamic model is simplified for computation efficiency.The solution to the optimal problem is obtained using a direct method based on Gauss pesudospectral discretization.Then a model predictive controller is designed to track the open-loop optimal reference trajectories,reducing the states’deviations caused by model simplification and ignorance of perturbations.Furthermore,it is proved that the fuel-optimal swing point is the apogee of the transfer orbit.The paper analyzes the fuel consumption of a typical scenario and demonstrates effectiveness of the proposed deorbit scheme numerically.
基金supported by the Fundamental Research Funds for the Central Universities(NUAA-NS2016082)
文摘A retrieval control strategy for failed satellite,which is connected to a servicing spacecraft by a tether,is studied.The Lagrange analytical mechanics based dynamics modeling for the system composed of a servicing spacecraft,a tether and a failed satellite,is presented under the earth center inertia coordinate system,then model simplification is conducted under the assumption that the failed satellite’s mass is far smaller than the servicing spacecraft’s,meanwhile the tether’s length is far smaller than the size of the servicing spacecraft’s orbit.Analysis shows that the retrieval process is intrinsically unstable as the Coriolis force functions is a negative damping.A retrieval strategy based on only the tether’s tension is designed,resulting in the fastest retrieval speed.In the proposed strategy,firstly,the tether’s swing angle amplitude is adjusted to 45?by deploying/retrieving the tether;then the tether swings freely with fixed length until it reaches negative maximum angle–45?;finally,the tether is retrieved by the pre-assigned exponential law.For simplicity,only the coplanar situation,that the tether swings in the plane of the servicing spacecraft’s orbit,is studied.Numerical simulation verifies the effectiveness of the strategy proposed.
