In this paper, the attitude stability of liquid-filled spacecraft with flexible appendage is investigated. The motion of liquid sloshing is modeled as the spherical pendulum, and the flexible appendage is approached b...In this paper, the attitude stability of liquid-filled spacecraft with flexible appendage is investigated. The motion of liquid sloshing is modeled as the spherical pendulum, and the flexible appendage is approached by a linear shearing beam. Nonlinear dynamic equations of the coupled system are derived from the Hamiltonian. The stability of the coupled system was analyzed by using the energy-Casimir method, and the nonlinear stability theorem of the coupled spacecraft system was also obtained. Through numerical computation, the correctness of the proposed theorem is verified and the boundary curves of the stable region are presented. The increase of the angular velocity and flexible attachment length will weaken the attitude stability, and the change of the filled ratio of liquid fuel tank has a different influence on the stability of the coupled spacecraft, depending on the different conditions. The attitude stability analysis of the coupled spacecraft system in this context is useful for selecting appropriate parameters in the complex spacecraft design.展开更多
The issue of attitude maneuver of a flexible spacecraft is investigated with single gimbaled control moment gyroscopes (SGCMGs) as an actuator. To solve the inertia uncertainty of the system, an adaptive attitude co...The issue of attitude maneuver of a flexible spacecraft is investigated with single gimbaled control moment gyroscopes (SGCMGs) as an actuator. To solve the inertia uncertainty of the system, an adaptive attitude control algorithm is designed by applying a radial basis function (RBF) neural network. An improved steering law for SGCMGs is proposed to achieve the optimal out- put torque. It enables the SGCMGs not only to avoid singularity, but also to output more precise torque. In addition, global, uniform, ultimate bounded stability of the attitude control system is proved via the Lyapunov technique. Simulation results demonstrate the effectiveness of the new steering law and the algorithm of attitude maneuver of the flexible spacecraft.展开更多
A robust adaptive control scheme is proposed for attitude maneuver and vibration suppression of flexible spacecraft in situations where parametric uncertainties,external disturbances,unmeasured elastic vibration and i...A robust adaptive control scheme is proposed for attitude maneuver and vibration suppression of flexible spacecraft in situations where parametric uncertainties,external disturbances,unmeasured elastic vibration and input saturation constraints exist. The controller does not need the knowledge of modal variables but the estimates of modal variables provided by appropriate dynamics of the controller. The requirements to know the system parameters and the bound of the external disturbance in advance are also eliminated by adaptive updating technique. Moreover,an auxiliary design system is constructed to analyze and compensate the effect of input saturation,and the state of the auxiliary design system is applied to the procedure of control design and stability analysis. Within the framework of the Lyapunov theory,stabilization and disturbance rejection of the overall system are ensured. Finally,simulations are conducted to study the effectiveness of the proposed control scheme,and simulation results demonstrate that the precise attitude control and vibration suppression are successfully achieved.展开更多
This paper is focused on attitude tracking control of a spacecraft that is equipped with flexible appendage and partially filled liquid propellant tank. The large amplitude liquid slosh is included by using a moving p...This paper is focused on attitude tracking control of a spacecraft that is equipped with flexible appendage and partially filled liquid propellant tank. The large amplitude liquid slosh is included by using a moving pulsating ball model that is further improved to estimate the settling location of liquid in microgravity or a zero-g environment. The flexible appendage is modelled as a three-dimensional Bernoulli–Euler beam, and the assumed modal method is employed.A hybrid controller that combines sliding mode control with an adaptive algorithm is designed for spacecraft to perform attitude tracking. The proposed controller has proved to be asymptotically stable. A nonlinear model for the overall coupled system including spacecraft attitude dynamics,liquid slosh, structural vibration and control action is established. Numerical simulation results are presented to show the dynamic behaviors of the coupled system and to verify the effectiveness of the control approach when the spacecraft undergoes the disturbance produced by large amplitude slosh and appendage vibration. Lastly, the designed adaptive algorithm is found to be effective to improve the precision of attitude tracking.展开更多
In this paper, the finite-time attitude tracking control problem for the spacecrafts with variable tilt of flexible appendages in the conditions of exogenous disturbances and inertia uncertainties is addressed. First ...In this paper, the finite-time attitude tracking control problem for the spacecrafts with variable tilt of flexible appendages in the conditions of exogenous disturbances and inertia uncertainties is addressed. First the characteristic modeling method is applied to the problem of the spacecraft modeling.Second, a novel adaptive sliding mode surface is designed based on the characteristic model. Furthermore, a discrete-time sliding mode control(DTSMC) law, which makes the tracking error converge into a predefined bound in finite time, is proposed by employing the parameters of characteristic model associated with the sliding mode surface to provide better performances,robustness, faster response, and higher control precision. The designed DTSMC includes the adaptive control architecture and is chattering-free. Finally, digital simulations of a sun synchronous orbit satellite(SSOS) are presented to illustrate effectiveness of the control strategies as well as to verify the practical feasibility of the rapid maneuver mission.展开更多
This paper presents a class of non-model-based position controllers for a kind of flexible spacecraft. With the controllers, one can achieve not only the closed-loop stability of the original distributed parameter sys...This paper presents a class of non-model-based position controllers for a kind of flexible spacecraft. With the controllers, one can achieve not only the closed-loop stability of the original distributed parameter system, but also the asymptotic stability of the truncated system, which is obtained through representing the deflection of the appendage by an arbitrary finite number of flexible modes. The system dynamics are not explicitly involved in the controller design and stability proof. Instead, only a very basic system energy relationship of the flexible spacecraft is utilized. The controllers possess several remarkable advantages over the traditional model-based ones. Numerical simulations are carried out on a kind of spacecraft with one flexible appendage and satisfactory results are obtained.展开更多
This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and external disturbances. The controller is based on the fractiona...This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and external disturbances. The controller is based on the fractional calculus and nonsingular terminal sliding mode control technique,and it guarantees the convergence of attitude tracking error in finite time rather than in the asymptotic sense. With respect to the controller,a fractional order sliding surface is given,the corresponding control scheme is proposed based on Lyapunov stability theory to guarantee the sliding condition,and the finite time stability of the whole close loop system is also proven. Finally,numerical simulations are presented to illustrate the performance of the proposed scheme.展开更多
This paper presented a hybrid control scheme to vibration reduction of flexible spacecraft during rotational maneuver by using variable structure output feedback control (VSOFC) and piezoelectric materials. The contro...This paper presented a hybrid control scheme to vibration reduction of flexible spacecraft during rotational maneuver by using variable structure output feedback control (VSOFC) and piezoelectric materials. The control configuration included the attitude controller based on VSOFC method and vibration attenuator designed by constant-gain negative velocity feedback control. The attitude controller consisted of a linear feedback term and a discontinuous feedback term. With the presence of this attitude controller, an additional flexible control system acting on the flexible parts can be designed for vibration control. Compared with conventional proportional-derivative (PD) control, the developed control scheme guarantees not only the stability of the closed-loop system, but also yields better performance and robustness in the presence of parametric uncertainties and external disturbance. Simulation results are presented for the spacecraft model to show the effectiveness of the proposed control techniques.展开更多
One of the main problems in designing robust control systems of flexiblespacecraft is the spillover management.The parameter optimization and orthogonalsubspace methods of the control and observation spillover managem...One of the main problems in designing robust control systems of flexiblespacecraft is the spillover management.The parameter optimization and orthogonalsubspace methods of the control and observation spillover management in dynamicoutput feedback control展开更多
A robust adaptive control scheme with prescribed performance is proposed for attitude maneuver and vibration suppression of flexible spacecraft,in which the parametric uncertainty,external disturbances and unmeasured ...A robust adaptive control scheme with prescribed performance is proposed for attitude maneuver and vibration suppression of flexible spacecraft,in which the parametric uncertainty,external disturbances and unmeasured elastic vibration are taken into account simultaneously.On the basis of the prescribed performance control(PPC)theory,the prescribed steady state and transient performance for the attitude tracking error can be guaranteed through the stabilization of the transformed system.This controller does not need the knowledge of modal variables.The absence of measurements of these variables is compensated by appropriate dynamics of the controller which supplies their estimates.The method of sliding mode differentiator is introduced to overcome the problem of explosion of complexity inherent in traditional backstepping design.In addition,the requirements of knowing the system parameters and the unknown bound of the lumped uncertainty,including external disturbance and the estimate error of sliding mode differentiator,have been eliminated by using adaptive updating technique.Within the framework of Lyapunov theory,the stability of the transformed system is obtained.Finally,numerical simulations are carried out to verify the effectiveness of the proposed control scheme.展开更多
A generalized scheme based on the sliding mode and component synthesis vibration suppression (CSVS) method has been proposed for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexibl...A generalized scheme based on the sliding mode and component synthesis vibration suppression (CSVS) method has been proposed for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages. The proposed control design process is twofold: design of the attitude controller followed by the design of a flexible vibration attenuator. The attitude controller using only the attitude and the rate information for the flexible spacecraft (FS) is designed to serve two purposes: it forces the attitude motion onto a pre-selected sliding surface and then guides it to the state space origin. The shaped command input controller based on the CSVS method is designed for the reduction of the flexible mode vibration, which only requires information about the natural frequency and damping of the closed system. This information is used to discretize the input so that minimum energy is injected via the controller to the flexible modes of the spacecraft. Additionally, to extend the CSVS method to the system with the on-off actuators, the pulse-width pulse-frequency (PWPF) modulation is introduced to control the thruster firing and integrated with the CSVS method. PWPF modulation is a control method that provides pseudo-linear operation for an on-off thruster. The proposed control strategy has been implemented on a FS, which is a hub with symmetric cantilever flexible beam appendages and can undergo a single axis rotation. The results have been proven the potential of this technique to control FS.展开更多
In this paper,a neural network adaptive controller is proposed for attitude tracking of flexible spacecraft in presence of unknown inertial matrix and external disturbance.In this approach,neural network technique is ...In this paper,a neural network adaptive controller is proposed for attitude tracking of flexible spacecraft in presence of unknown inertial matrix and external disturbance.In this approach,neural network technique is employed to approximate the unknown system dynamics with finite combinations of some basis functions,and a robust controller is also designed to attenuate the effect of approximation error,more specially,the knowledge of angular velocity is not required.In the closed-loop system,Lyapunov stability analysis shows that the attitude trajectories asymptotically follow the reference output trajectories.Finally,simulation results are presented for the attitude tracking of a flexible spacecraft to show the excellent performance of the proposed controller and illustrate its robustness in face of external disturbances and unknown dynamics.展开更多
A dual-stage control system design method is presented for the three-axis-rotational maneuver and vibration stabilization of a spacecraft with flexible appendages embedded with piezoceramics as sensor and actuator. In...A dual-stage control system design method is presented for the three-axis-rotational maneuver and vibration stabilization of a spacecraft with flexible appendages embedded with piezoceramics as sensor and actuator. In this design approach, the attitude control and the vibration suppression sub-systems are designed separately using the lower order model. The design of attitude controller is based on the variable structure control (VSC) theory leading to a discontinuous control law. This controller accomplishes asymptotic attitude maneuvering in the closed-loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. To actively suppress the flexible vibrations, the modal velocity feedback control method is presented by using piezoelectric materials as additional sensor and actuator bonded on the surface of the flexible appendages. In addition, a special configuration of actuators for three-axis attitude control is also investigated: the pitch attitude controlled by a momentum wheel, and the roll/yaw control achieved by on-off thrusters, which is modulated by pulse width pulse frequency modulation technique to construct the proper control torque history. Numerical simulations performed show that the rotational maneuver and vibration suppression are accomplished in spite of the presence of disturbance torque and parameter uncertainty.展开更多
This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Ber...This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton's prin- ciple. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superim- posed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liq- uid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algo- rithm would suppress the residual vibration.展开更多
为提高敏捷挠性航天器在轨连续机动的快速性和高稳定性,应用变速控制力矩陀螺(variable speed control moment gyroscopes,VSCMGs)作为姿态控制执行机构,提出了一种将观测器与自适应控制结合的姿态控制律与VSCMGs复合操纵律。考虑到机...为提高敏捷挠性航天器在轨连续机动的快速性和高稳定性,应用变速控制力矩陀螺(variable speed control moment gyroscopes,VSCMGs)作为姿态控制执行机构,提出了一种将观测器与自适应控制结合的姿态控制律与VSCMGs复合操纵律。考虑到机动过程中挠性模态及精确惯量不可知,采用模态观测器和转动惯量估计器对不可测的状态或参数进行辨识,辨识结果用于精确估计前馈补偿力矩,利用Lyapunov分析方法证明了闭环控制系统的稳定性。鉴于VSCMGs实际使用的力矩分配能力、避奇异能力、轮速平衡能力与末态框架角定位能力,分别设计了加权伪逆操纵律与3种对应的零运动。基于雅可比矩阵条件数提出了末态框架角的优选方法,给出了VSCMGs零运动在机动过程不同阶段的部署方案。结果表明:通过连续姿态机动数值仿真验证了所提算法的有效性;VSCMGs在连续机动过程中平滑切换模式,在不同的机动阶段实现了相应功能。模态观测值和惯量估计值在多次机动后收敛至真值附近,经过参数辨识后的控制器使航天器在机动末端更快更稳地达到指向精度要求。展开更多
基金supported by the National Natural Science Foundation of China (Grants 11472041, 11532002)the Doctoral Fund of Ministry of Education of China (Grant 20131101110002)
文摘In this paper, the attitude stability of liquid-filled spacecraft with flexible appendage is investigated. The motion of liquid sloshing is modeled as the spherical pendulum, and the flexible appendage is approached by a linear shearing beam. Nonlinear dynamic equations of the coupled system are derived from the Hamiltonian. The stability of the coupled system was analyzed by using the energy-Casimir method, and the nonlinear stability theorem of the coupled spacecraft system was also obtained. Through numerical computation, the correctness of the proposed theorem is verified and the boundary curves of the stable region are presented. The increase of the angular velocity and flexible attachment length will weaken the attitude stability, and the change of the filled ratio of liquid fuel tank has a different influence on the stability of the coupled spacecraft, depending on the different conditions. The attitude stability analysis of the coupled spacecraft system in this context is useful for selecting appropriate parameters in the complex spacecraft design.
基金supported by the National Natural Science Foundation of China(61473152)the China Scholarship Council and the Educational Innovation Project for Graduate Students of Jiangsu Province(KYLX15 0399)
文摘The issue of attitude maneuver of a flexible spacecraft is investigated with single gimbaled control moment gyroscopes (SGCMGs) as an actuator. To solve the inertia uncertainty of the system, an adaptive attitude control algorithm is designed by applying a radial basis function (RBF) neural network. An improved steering law for SGCMGs is proposed to achieve the optimal out- put torque. It enables the SGCMGs not only to avoid singularity, but also to output more precise torque. In addition, global, uniform, ultimate bounded stability of the attitude control system is proved via the Lyapunov technique. Simulation results demonstrate the effectiveness of the new steering law and the algorithm of attitude maneuver of the flexible spacecraft.
文摘A robust adaptive control scheme is proposed for attitude maneuver and vibration suppression of flexible spacecraft in situations where parametric uncertainties,external disturbances,unmeasured elastic vibration and input saturation constraints exist. The controller does not need the knowledge of modal variables but the estimates of modal variables provided by appropriate dynamics of the controller. The requirements to know the system parameters and the bound of the external disturbance in advance are also eliminated by adaptive updating technique. Moreover,an auxiliary design system is constructed to analyze and compensate the effect of input saturation,and the state of the auxiliary design system is applied to the procedure of control design and stability analysis. Within the framework of the Lyapunov theory,stabilization and disturbance rejection of the overall system are ensured. Finally,simulations are conducted to study the effectiveness of the proposed control scheme,and simulation results demonstrate that the precise attitude control and vibration suppression are successfully achieved.
基金supported by the National Natural Science Foundation of China (Grants 11472041, 11532002)the Doctoral Fund of Ministry of Education of China (Grant 20131101110002)
文摘This paper is focused on attitude tracking control of a spacecraft that is equipped with flexible appendage and partially filled liquid propellant tank. The large amplitude liquid slosh is included by using a moving pulsating ball model that is further improved to estimate the settling location of liquid in microgravity or a zero-g environment. The flexible appendage is modelled as a three-dimensional Bernoulli–Euler beam, and the assumed modal method is employed.A hybrid controller that combines sliding mode control with an adaptive algorithm is designed for spacecraft to perform attitude tracking. The proposed controller has proved to be asymptotically stable. A nonlinear model for the overall coupled system including spacecraft attitude dynamics,liquid slosh, structural vibration and control action is established. Numerical simulation results are presented to show the dynamic behaviors of the coupled system and to verify the effectiveness of the control approach when the spacecraft undergoes the disturbance produced by large amplitude slosh and appendage vibration. Lastly, the designed adaptive algorithm is found to be effective to improve the precision of attitude tracking.
基金supported by National Natural Science Foundation of China(61125306,91016004)Foundation of Ministry of Education of China(20110092110020,20120092110026)the Post-Doctoral Research Funds(1108000137,3208004602)
文摘In this paper, the finite-time attitude tracking control problem for the spacecrafts with variable tilt of flexible appendages in the conditions of exogenous disturbances and inertia uncertainties is addressed. First the characteristic modeling method is applied to the problem of the spacecraft modeling.Second, a novel adaptive sliding mode surface is designed based on the characteristic model. Furthermore, a discrete-time sliding mode control(DTSMC) law, which makes the tracking error converge into a predefined bound in finite time, is proposed by employing the parameters of characteristic model associated with the sliding mode surface to provide better performances,robustness, faster response, and higher control precision. The designed DTSMC includes the adaptive control architecture and is chattering-free. Finally, digital simulations of a sun synchronous orbit satellite(SSOS) are presented to illustrate effectiveness of the control strategies as well as to verify the practical feasibility of the rapid maneuver mission.
文摘This paper presents a class of non-model-based position controllers for a kind of flexible spacecraft. With the controllers, one can achieve not only the closed-loop stability of the original distributed parameter system, but also the asymptotic stability of the truncated system, which is obtained through representing the deflection of the appendage by an arbitrary finite number of flexible modes. The system dynamics are not explicitly involved in the controller design and stability proof. Instead, only a very basic system energy relationship of the flexible spacecraft is utilized. The controllers possess several remarkable advantages over the traditional model-based ones. Numerical simulations are carried out on a kind of spacecraft with one flexible appendage and satisfactory results are obtained.
基金supported by the National Natural Science Foundation of China (61174037)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 61021002)the Natural Science Foundation of Heilongjiang Province (Grant No. F201307)
文摘This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and external disturbances. The controller is based on the fractional calculus and nonsingular terminal sliding mode control technique,and it guarantees the convergence of attitude tracking error in finite time rather than in the asymptotic sense. With respect to the controller,a fractional order sliding surface is given,the corresponding control scheme is proposed based on Lyapunov stability theory to guarantee the sliding condition,and the finite time stability of the whole close loop system is also proven. Finally,numerical simulations are presented to illustrate the performance of the proposed scheme.
基金Sponsored by Program for Young Excellent Talents in Harbin Institute of Technology(Grant No.HITQNJS.2007.001)National Natural Science Founda-tion of China(Grant No.60674101)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20050213010).
文摘This paper presented a hybrid control scheme to vibration reduction of flexible spacecraft during rotational maneuver by using variable structure output feedback control (VSOFC) and piezoelectric materials. The control configuration included the attitude controller based on VSOFC method and vibration attenuator designed by constant-gain negative velocity feedback control. The attitude controller consisted of a linear feedback term and a discontinuous feedback term. With the presence of this attitude controller, an additional flexible control system acting on the flexible parts can be designed for vibration control. Compared with conventional proportional-derivative (PD) control, the developed control scheme guarantees not only the stability of the closed-loop system, but also yields better performance and robustness in the presence of parametric uncertainties and external disturbance. Simulation results are presented for the spacecraft model to show the effectiveness of the proposed control techniques.
文摘One of the main problems in designing robust control systems of flexiblespacecraft is the spillover management.The parameter optimization and orthogonalsubspace methods of the control and observation spillover management in dynamicoutput feedback control
文摘A robust adaptive control scheme with prescribed performance is proposed for attitude maneuver and vibration suppression of flexible spacecraft,in which the parametric uncertainty,external disturbances and unmeasured elastic vibration are taken into account simultaneously.On the basis of the prescribed performance control(PPC)theory,the prescribed steady state and transient performance for the attitude tracking error can be guaranteed through the stabilization of the transformed system.This controller does not need the knowledge of modal variables.The absence of measurements of these variables is compensated by appropriate dynamics of the controller which supplies their estimates.The method of sliding mode differentiator is introduced to overcome the problem of explosion of complexity inherent in traditional backstepping design.In addition,the requirements of knowing the system parameters and the unknown bound of the lumped uncertainty,including external disturbance and the estimate error of sliding mode differentiator,have been eliminated by using adaptive updating technique.Within the framework of Lyapunov theory,the stability of the transformed system is obtained.Finally,numerical simulations are carried out to verify the effectiveness of the proposed control scheme.
文摘A generalized scheme based on the sliding mode and component synthesis vibration suppression (CSVS) method has been proposed for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages. The proposed control design process is twofold: design of the attitude controller followed by the design of a flexible vibration attenuator. The attitude controller using only the attitude and the rate information for the flexible spacecraft (FS) is designed to serve two purposes: it forces the attitude motion onto a pre-selected sliding surface and then guides it to the state space origin. The shaped command input controller based on the CSVS method is designed for the reduction of the flexible mode vibration, which only requires information about the natural frequency and damping of the closed system. This information is used to discretize the input so that minimum energy is injected via the controller to the flexible modes of the spacecraft. Additionally, to extend the CSVS method to the system with the on-off actuators, the pulse-width pulse-frequency (PWPF) modulation is introduced to control the thruster firing and integrated with the CSVS method. PWPF modulation is a control method that provides pseudo-linear operation for an on-off thruster. The proposed control strategy has been implemented on a FS, which is a hub with symmetric cantilever flexible beam appendages and can undergo a single axis rotation. The results have been proven the potential of this technique to control FS.
基金Sponsored by the National Nature Science Foundation of China(Grant No.60774062)the Research Fund for the Doctoral Program of High Education of China(Grant No.20070213061)
文摘In this paper,a neural network adaptive controller is proposed for attitude tracking of flexible spacecraft in presence of unknown inertial matrix and external disturbance.In this approach,neural network technique is employed to approximate the unknown system dynamics with finite combinations of some basis functions,and a robust controller is also designed to attenuate the effect of approximation error,more specially,the knowledge of angular velocity is not required.In the closed-loop system,Lyapunov stability analysis shows that the attitude trajectories asymptotically follow the reference output trajectories.Finally,simulation results are presented for the attitude tracking of a flexible spacecraft to show the excellent performance of the proposed controller and illustrate its robustness in face of external disturbances and unknown dynamics.
基金Sponsored by the National Natural Science Foundation of China (Grant No.60774062)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20070213061)Young Excellent Talents in Harbin Institute of Technology (Grant No.HITQNJS.2007.001)
文摘A dual-stage control system design method is presented for the three-axis-rotational maneuver and vibration stabilization of a spacecraft with flexible appendages embedded with piezoceramics as sensor and actuator. In this design approach, the attitude control and the vibration suppression sub-systems are designed separately using the lower order model. The design of attitude controller is based on the variable structure control (VSC) theory leading to a discontinuous control law. This controller accomplishes asymptotic attitude maneuvering in the closed-loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. To actively suppress the flexible vibrations, the modal velocity feedback control method is presented by using piezoelectric materials as additional sensor and actuator bonded on the surface of the flexible appendages. In addition, a special configuration of actuators for three-axis attitude control is also investigated: the pitch attitude controlled by a momentum wheel, and the roll/yaw control achieved by on-off thrusters, which is modulated by pulse width pulse frequency modulation technique to construct the proper control torque history. Numerical simulations performed show that the rotational maneuver and vibration suppression are accomplished in spite of the presence of disturbance torque and parameter uncertainty.
基金supported by the National Natural Science Foundation of China(NNSFC)(Grant 11472041)the Research Fund for the Doctoral Program of Higher Education of China(Grant 20131101110002)
文摘This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton's prin- ciple. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superim- posed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liq- uid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algo- rithm would suppress the residual vibration.
文摘为提高敏捷挠性航天器在轨连续机动的快速性和高稳定性,应用变速控制力矩陀螺(variable speed control moment gyroscopes,VSCMGs)作为姿态控制执行机构,提出了一种将观测器与自适应控制结合的姿态控制律与VSCMGs复合操纵律。考虑到机动过程中挠性模态及精确惯量不可知,采用模态观测器和转动惯量估计器对不可测的状态或参数进行辨识,辨识结果用于精确估计前馈补偿力矩,利用Lyapunov分析方法证明了闭环控制系统的稳定性。鉴于VSCMGs实际使用的力矩分配能力、避奇异能力、轮速平衡能力与末态框架角定位能力,分别设计了加权伪逆操纵律与3种对应的零运动。基于雅可比矩阵条件数提出了末态框架角的优选方法,给出了VSCMGs零运动在机动过程不同阶段的部署方案。结果表明:通过连续姿态机动数值仿真验证了所提算法的有效性;VSCMGs在连续机动过程中平滑切换模式,在不同的机动阶段实现了相应功能。模态观测值和惯量估计值在多次机动后收敛至真值附近,经过参数辨识后的控制器使航天器在机动末端更快更稳地达到指向精度要求。