In this paper, a novel fractional-order fuzzy sliding mode control strategy is developed to realize the deployment of the tethered satellite system (TSS) with input saturation. The considered TSS is modeled as an underactuated system. By decoupling the underactuated system into two subsystems, a fractional-order and a constrained integer-order sliding surfaces are designed for the actuated and unactuated subsystems, respectively. Then, a new hybrid sliding manifold is obtained by coupling the two subsliding surfaces. Adaptive fuzzy algorithm is used to regulate the coupling coefficient in the newly proposed hybrid sliding manifold in order to procure satisfactory performance. Meanwhile, the saturation nonlinearity of control input is also considered. The asymptotic stability of the closed-loop system is demonstrated theoretically. With the existence of fractional order, the presented controller can perform faster and more smooth tether deployment when compared with conventional ones. Finally, the effectiveness and superiority of the proposed control approach are validated by illustrative simulations.

Fractional-Order Fuzzy Sliding Mode Control for the Deployment of Tethered Satellite System Under Input Saturation

Fixed-time attitude tracking control for spacecraft without unwinding

Space debris is growing dramatically with the rapid pace of human exploration of space, which seriously threatens the safety of artificial spacecraft in orbit. Therefore, the active debris removal (ADR) is important. This review aims to review the ADR methods and to advance related research in the future. The current research and development status are clearly demonstrated by mapping knowledge domain and charts. In this paper, the latest research results are classified and summarized in detail from two aspects of space debris capture and removal. The scheme comparison and evaluation of all ADR methods are performed, and the applicable scopes of various methods are summarized. Each ADR method is scored using a cobweb evaluation model based on six indicators. Future development of ADR is discussed to promote further research interest.

Survey on research and development of on-orbit active debris removal methods

This paper investigates the anti-unwinding finite-time attitude synchronization control problem for Spacecraft formation flying with external disturbances. Two finite-time controllers are designed based on rotation matrix and terminal sliding mode method. By designing a novel sliding mode surface, the first controller is developed when the upper bound of the external disturbances can be exactly known. However, this value is not always available in reality. In addition, the direct use of the upper bound of the external disturbances can result in the chattering problem. For the purpose of overcoming the disadvantage of the first controller, a modified control law is proposed, in which the adaptive law is applied to estimate the unknown value online. Theoretical analysis and numerical simulations are presented to demonstrate the validity of the proposed controllers.

Rotation matrix based finite-time attitude synchronization control for spacecraft with external disturbances.

Tethered satellite systems (TSSs) have attracted significant attention due to their potential and valuable applications for scientific research. With the development of various launched on-orbit missions, the deployment of tethers is considered a crucial technology for operation of a TSS. Both past orbiting experiments and numerical results have shown that oscillations of the deployed tether due to the Coriolis force and environmental perturbations are inevitable and that the impact between the space tether and end-body at the end of the deployment process leads to complicated nonlinear phenomena. Hence, a set of suitable control methods plays a fundamental role in tether deployment. This review article summarizes previous work on aspects of the dynamics, control, and ground-based experiments of tether deployment. The relevant basic principles, analytical expressions, simulation cases, and experimental results are presented as well.

Review of deployment technology for tethered satellite systems

Fractional order sliding mode control for tethered satellite deployment with disturbances

Dynamics and control of de-spinning giant asteroids by small tethered spacecraft

This paper proposed a unified energy-based control framework for fast, stable, and precision deployment of underactuated TSS. The tension controller with partial state feedback is derived from an artificial potential energy function and a dissipative function, where the control objectives and requirements are transformed into the necessary and sufficient conditions for these functions. The feedback law can be either linear or nonlinear, depending on the construction of the artificial potential energy function and the dissipative function. The controllability of the underactuated TSS is proved which is the original contribution of this work. The energy-based tension control is proved asymptotically stable by the Lyapunov technique and LaSalle’s invariance principle. Furthermore, the constraints on positive tension and nonnegative tether deploy velocity are incorporated into the energy-based tension controller by control gain optimization using optimal control. Four controllers are developed based on the proposed control framework to demonstrate the effectiveness and robustness of the proposed energy-based framework using numerical simulation.

A unified energy-based control framework for tethered spacecraft deployment

Attitude stabilization of a massive rotating uncooperative target by a tethered space tug is studied for orbit maneuvering in the postcapture operation analytically and experimentally. The perturbed orbital propagation of the tethered space system is described with nonsingular orbital elements and the relative equations of motion of the tethered space system, including the tether libration and attitudes of target and tug, are established in the orbital frame. The tether tension control, the tug's attitude control, and the combination control of them are designed to suppress the attitude and libration motions of the target/tug and the tethered space system with bounded stability. The control law's effectiveness is demonstrated by simulation and then validated experimentally by a microgravity testbed with two tethered free-floating air-bearing satellite simulators.

Junjie Kang

Papers

Fractional order sliding mode control for tethered satellite deployment with disturbances

Dynamics and control of de-spinning giant asteroids by small tethered spacecraft

A unified energy-based control framework for tethered spacecraft deployment

Analytical and Experimental Investigation of Stabilizing Rotating Uncooperative Target by Tethered Space Tug

Dynamics and de-spin control of massive target by single tethered space tug