“…In the light of Lagrangian mechanics, the deployment dynamics of TSS can be described by 2 where τ denotes the tension acting along the space tether, and the generalized force Q θ is related to phase of θ and is regarded as zero as the tension is the only force to regulate the in-plane dynamics. To maintain the space tether taut, the condition 0 < τ min ≤ τ ≤ τ max < ∞ should be ensured during the entire liberation, that is, τ max averts the breakage of space tether and τ min > 0 precludes a slack tether.…”
Section: Dynamics and Controlmentioning
confidence: 99%
“…Deployment process of TSS is aimed at driving subspacecraft onto specified orbit, and it is hence an essential stage to start a space mission, such as maneuvering of TSS, formation flight, tether-based capture, and re-entry capsule. [1][2][3][4][5] It is noted that deployment dynamics and control is one of the most key issues in these mentioned tasks, and many advanced control strategies have been proposed to achieve a stable and fast deployment. 6,7 In general, there exists two typical difficult problems to deal with in controller design for deployment, and they are underactuated dynamics and constrained input when only using tension.…”
This paper proposes a fractional-order integral sliding mode control with the order 0 < ν < 1 to stabilize the deployment of tethered spacecraft system with only tension regulation. The work in this paper is partially based on integer-order nonlinear sliding mode controller and improves its performance with fractional-order calculus. The proposed scheme makes use of integral sliding surface to obtain smaller convergence regions of state errors, and the fractional derivative is synthesized to enhance the flexibility of controller design by fining parameters for better dynamic and steady-state performance. Fractional-order observers help to eliminate external disturbances while the adaptive law is presented to remove the adverse effect in stability analyses, and fractional-order uniform ultimate boundedness is proved to guarantee the existence of the proposed sliding surface. According to theoretical analyses, the fractional order will indeed affect the dynamic and steady-state performance of control system, and the proposed method will be verified in numerical simulations compared with the nonlinear sliding mode counterpart.
“…In the light of Lagrangian mechanics, the deployment dynamics of TSS can be described by 2 where τ denotes the tension acting along the space tether, and the generalized force Q θ is related to phase of θ and is regarded as zero as the tension is the only force to regulate the in-plane dynamics. To maintain the space tether taut, the condition 0 < τ min ≤ τ ≤ τ max < ∞ should be ensured during the entire liberation, that is, τ max averts the breakage of space tether and τ min > 0 precludes a slack tether.…”
Section: Dynamics and Controlmentioning
confidence: 99%
“…Deployment process of TSS is aimed at driving subspacecraft onto specified orbit, and it is hence an essential stage to start a space mission, such as maneuvering of TSS, formation flight, tether-based capture, and re-entry capsule. [1][2][3][4][5] It is noted that deployment dynamics and control is one of the most key issues in these mentioned tasks, and many advanced control strategies have been proposed to achieve a stable and fast deployment. 6,7 In general, there exists two typical difficult problems to deal with in controller design for deployment, and they are underactuated dynamics and constrained input when only using tension.…”
This paper proposes a fractional-order integral sliding mode control with the order 0 < ν < 1 to stabilize the deployment of tethered spacecraft system with only tension regulation. The work in this paper is partially based on integer-order nonlinear sliding mode controller and improves its performance with fractional-order calculus. The proposed scheme makes use of integral sliding surface to obtain smaller convergence regions of state errors, and the fractional derivative is synthesized to enhance the flexibility of controller design by fining parameters for better dynamic and steady-state performance. Fractional-order observers help to eliminate external disturbances while the adaptive law is presented to remove the adverse effect in stability analyses, and fractional-order uniform ultimate boundedness is proved to guarantee the existence of the proposed sliding surface. According to theoretical analyses, the fractional order will indeed affect the dynamic and steady-state performance of control system, and the proposed method will be verified in numerical simulations compared with the nonlinear sliding mode counterpart.
“…The axis Cxt points in the opposite direction of the tether tension, and the angles θ, β between Cxyz and Cxtytzt shown in Figure 1, which are called in-plane and out-of-plane angle, indicate the location relation between the projection of the tether in the orbital plane with the direction of the vertical line, and the relationship between the tether and the orbit plane, respectively. 29 Figure 1.The schematic diagram of DTSS.…”
The dual-body tethered satellite system, which consists of two spacecraft connected by a single tether, is one of the most promising configurations in numerous space missions. To ensure the stability of deployment, the radial basis function neural network-based adaptive terminal sliding mode controller is proposed for the dual-body tethered satellite system with the model uncertainty and external disturbance. The terminal sliding mode controller serves as the main control framework for its properties of the strong robustness and finite-time convergence. The radial basis function neural network is adopted to approximate the model uncertainty, in which the weight vector of the radial basis function neural networks and the unknown upper bound of the external disturbance are estimated by using two adaptive laws. Finally, the Lyapunov theory and numerical simulations are used to prove the validity of the proposed controller.
“…There are many potential applications for tethers such as coordinated measurements from multiple satellites tethered together (formation flying), artificial gravity in spacecraft using a rotating tethered system, small pay-load launch assist e.g. [7,8]. The tethered systems offer numerous ways of beneficial implementation on modern spacecrafts and allow to perform multiple tasks such as the tethered payload planetary capture applications, studied by Williams [9].…”
Section: Introductionmentioning
confidence: 99%
“…Thus Space tethers have been proposed for a wide range of useful applications, including payload delivery from the Earth orbit and Earth monitoring, using surveillance equipment on the lower end of a vertical tether. Majority of recently developed models are focused on the tether, while the spacecraft and the payload are usually referred to as the point end-masses [1][2][3][4][5][6][7][8][9].…”
The motion about a centre of mass of a spacecraft with a vertical elastic tethered system under the action of the gravitational moment and small periodic tethered force at a circular orbit is studied. The mathematical model is derived using Lagrange's equations including tether vibrations and oscillations of the spacecraft relatively of the proper mass center. The paper contains bifurcation analysis, phase space study, and analytic solutions for separatrixes. The considered mechanical system performs chaotic motion near separatrixes under the influence of small disturbances. The Melnikov method gives a criterion for homo/heteroclinic chaos in terms of system parameters. Results of the study can be useful for the analysis of gravitational stabilization systems with space tethers and for studying the behavior of a spacecraft with a deployed tether.
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