Adaptive control for attitude coordination of leader-following rigid spacecraft systems with inertia parameter uncertainties

This paper studies the leader-following attitude coordination problems of multiple spacecraft in the presence of inertia parameter uncertainties. To achieve attitude coordination in the situation that even the leader's attitude is only applicable to a part of the following spacecraft, a nonlinear attitude observer is proposed to obtain an accurate estimation of the leader's attitude and angular velocity for all the followers. In addition, a distributed control scheme based on noncertainty equivalence principle is presented for multiple spacecraft' attitude synchronization. With a dynamic scaling, attitude consensus can be achieved asymptotically without any information of the bounds of the uncertain inertia parameters. Furthermore, once the estimations of inertia parameters reach their ideal values, the estimation process will stop and the ideal value of inertia parameter will be held. This is a special advantage of parameter estimation method based on non-certainty equivalence. Numerical simulations are presented to demonstrate that the proposed non-certainty equivalence-based method requires smaller control toque and converges faster compared with the certainty equivalence-based method.     

Delay Depending Decentralized Adaptive Attitude Synchronization Tracking Control of Spacecraft Formation

This paper deals with the problem of cooperative attitude tracking with time-varying communication delays as well as the delays between inter-synchronization control parts and self-tracking control parts in the spacecraft formation flying. First, we present the attitude synchronization tracking control algorithms and analyze the sufficient delay-dependent stability condition with the choice of a Lyapunov function when the angular velocity can be measured. More specifically, a class of linear filters is developed to derive an output feedback control law without having direct information of the angular velocity, which is significant for practical applications with low-cost configurations of spacecraft. Using a well-chosen Lyapunov-Krasovskii function, it is proven that the presented control law can make the spacecraft formation attitude tracking system synchronous and achieve exponential stability, in the face of model uncertainties, as well as non-uniform time-varying delays in communication links and different control parts. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control schemes.     

航天器有限时间输出反馈姿态控制

研究在角速度不可测时航天器的有限时间姿态控制问题。基于有限时间控制技术,提出了由修正Rodrigues参数进行姿态描述的航天器输出反馈姿态控制算法。首先设计了单个航天器的输出反馈姿态控制器,在没有角速度反馈时也能够保证航天器姿态在有限时间内调节到期望姿态。之后,设计了无需绝对角速度和相对角速度信息的多航天器分布式输出反馈姿态控制器。使用Lyapunov理论和图论,对闭环系统全局有限时间稳定性进行了严格的证明。最后对提出的控制算法进行了数值仿真,其结果验证了所设计的航天器输出反馈控制算法的可行性和有效性。     

Attitude coordination for spacecraft formation with multiple communication delays

Communication delays are inherently present in information exchange between spacecraft and have an effect on the control performance of spacecraft formation. In this work, attitude coordination control of spacecraft formation is addressed, which is in the presence of multiple communication delays between spacecraft. Virtual system-based approach is utilized in case that a constant reference attitude is available to only a part of the spacecraft. The feedback from the virtual systems to the spacecraft formation is introduced to maintain the formation. Using backstepping control method, input torque of each spacecraft is designed such that the attitude of each spacecraft converges asymptotically to the states of its corresponding virtual system. Furthermore, the backstepping technique and the Lyapunov–Krasovskii method contribute to the control law design when the reference attitude is time-varying and can be obtained by each spacecraft. Finally, effectiveness of the proposed methodology is illustrated by the numerical simulations of a spacecraft formation.     

考虑输入饱和的航天器相对运动鲁棒自适应控制

 研究了在输入饱和约束条件下的航天器相对运动的姿态和轨道一体化控制问题。首先,基于单位对偶四元数给出了航天器6自由度相对运动的数学模型,利用误差对偶四元数来描述航天器的相对姿态和相对位置。接着,针对输入饱和问题,提出了一种对航天器模型参数不确定性和外部有界干扰具有较强鲁棒性的自适应控制器,并通过李雅普诺夫方法从理论上严格证明了整个闭环系统的全局渐近稳定性。最后,通过数值仿真来验证设计方法的有效性和可行性,并且与其他方法进行了比较,结果表明设计的方法能够抑制输入饱和的问题,在性能上具有更快的收敛速度和更强的鲁棒性。     

Coordinated attitude control for flexible spacecraft formation with actuator configuration misalignment

This paper investigates the coordinated attitude control problem for flexible spacecraft formation with the consideration of actuator configuration misalignment. First, an integral-type sliding mode adaptive control law is designed to compensate the effects of flexible mode, environmental disturbance and actuator installation deviation. The basic idea of the Integral-type Sliding Mode Control (ISMC) is to design a proper sliding manifold so that the sliding mode starts from the initial time instant, and thus the robustness of the system can be guaranteed from the beginning of the process and the reaching phase is eliminated. Then, considering the nominal system of spacecraft formation based on directed topology, an attitude cooperative control strategy is developed for the nominal system with or without communication delay. The proposed control law can guarantee that for each spacecraft in the spacecraft formation, the desired attitude objective can be achieved and the attitude synchronization can be maintained with other spacecraft in the formation. Finally, simulation results are given to show the effectiveness of the proposed control algorithm.     

A composite control scheme for attitude maneuvering and elastic mode stabilization of flexible spacecraft with measurable output feedback

This paper treats the question of attitude maneuver control and elastic mode stabilization of a flexible spacecraft based on adaptive sliding mode theory and active vibration control technique using piezoelectric materials. More precisely, a modified positive position feedback (PPF) scheme is developed to design the PPF compensator gains in a more systematical way to stabilize the vibration modes in the inner loop, in which a cost function is introduced to be minimized by the feedback gains subject to the stability criterion at the same time. Based on adaptive sliding mode control theory, a discontinuous attitude control law is derived to achieve the desired position of the spacecraft, taking explicitly into account the mismatched perturbation and actuator constraints. In the attitude control law, an adaptive mechanism is also embedded such that the unknown upper bound of perturbation is automatically adapted. Once the controlled attitude control system reaches the switching hyperplane, the state variables can be driven into a small bounded region. An additional attractive feature of the attitude control method is that the structure of the controller is independent of the elastic mode dynamics of the spacecraft, since in practice the measurement of flexible modes is not easy or feasible. The proposed control strategy has been implemented on a flexible spacecraft. Both analytical and numerical results are presented to show the theoretical and practical merit of this approach.     

Distributed fixed-time attitude coordinated control for multiple spacecraft with actuator saturation

This paper investigates the distributed fixed-time attitude coordinated control problem for multiple spacecraft subject to actuator saturation under the directed topology. First, a distributed fixed-time observer is presented for each follower spacecraft to estimate the leader spacecraft’s states. Compared with the commonly used fixed-time observer, the settling time of the proposed fixed-time observer can be easily adjusted by some free design parameters. Next, a distributed fixed-time control ...     

基于新型终端滑模的航天器执行器故障容错姿态控制

针对受干扰的刚体航天器冗余执行器存在故障与控制受限的姿态跟踪控制问题,提出一类基于新型指数形式的非奇异快速滑模面（ENFTSM）与趋近律的姿态容错控制器设计方法。当部分推力器发生故障时,假设剩余推力器具有输出饱和特性且能提供足够推力保证航天器执行任务,相比一般终端滑模控制器,本文设计的控制器不仅能使系统状态以更快的速度到达平衡点,且不需要在线对执行器故障信息进行检测和分离。基于Lyapunov方法证明本文设计的控制器能保证闭环系统稳定,且能有效地抑制外部干扰、控制受限和执行器故障等约束。最后对提出的控制算法进行了数值仿真,其结果表明了该控制器的有效性。     

基于新型终端滑模的航天器执行器故障容错姿态控制简

 针对受干扰的刚体航天器冗余执行器存在故障与控制受限的姿态跟踪控制问题,提出一类基于新型指数形式的非奇异快速滑模面（ENFTSM）与趋近律的姿态容错控制器设计方法。当部分推力器发生故障时,假设剩余推力器具有输出饱和特性且能提供足够推力保证航天器执行任务,相比一般终端滑模控制器,本文设计的控制器不仅能使系统状态以更快的速度到达平衡点,且不需要在线对执行器故障信息进行检测和分离。基于Lyapunov方法证明本文设计的控制器能保证闭环系统稳定,且能有效地抑制外部干扰、控制受限和执行器故障等约束。最后对提出的控制算法进行了数值仿真,其结果表明了该控制器的有效性。     

Robust attitude coordinated control for spacecraft formation with communication delays

In this paper,attitude coordinated tracking control algorithms for multiple spacecraft formation are investigated with consideration of parametric uncertainties,external disturbances,communication delays and actuator saturation.Initially,a sliding mode delay-dependent attitude coordinated controller is proposed under bounded external disturbances.However,neither inertia uncertainty nor actuator constraint has been taken into account.Then,a robust saturated delay dependent attitude coordinated control law is further derived,where uncertainties and external disturbances are handled by Chebyshev neural networks (CNN).In addition,command filter technique is introduced to facilitate the backstepping design procedure,through which actuator saturation problem is solved.Thus the spacecraft in the formation are able to track the reference attitude trajectory even in the presence of time-varying communication delays.Rigorous analysis is presented by using Lyapunov-Krasovskii approach to demonstrate the stability of the closed-loop system under both control algorithms.Finally,the numerical examples are carried out to illustrate the efficiency of the theoretical results.     

Adaptive Integral-type Sliding Mode Control for Spacecraft Attitude Maneuvering Under Actuator Stuck Failures

A fault tolerant control (FTC) design technique against actuator stuck faults is investigated using integral-type sliding mode control (ISMC) with application to spacecraft attitude maneuvering control system. The principle of the proposed FTC scheme is to design an integral-type sliding mode attitude controller using on-line parameter adaptive updating law to compensate for the effects of stuck actuators. This adaptive law also provides both the estimates of the system parameters and external disturbances such that a prior knowledge of the spacecraft inertia or boundedness of disturbances is not required. Moreover, by including the integral feedback term, the designed controller can not only tolerate actuator stuck faults, but also compensate the disturbances with constant components. For the synthesis of controller, the fault time, patterns and values are unknown in advance, as motivated from a practical spacecraft control application. Complete stability and performance analysis are presented and illustrative simulation results of application to a spacecraft show that high precise attitude control with zero steady-error is successfully achieved using various scenarios of stuck failures in actuators.     

Event-triggered adaptive control for attitude tracking of spacecraft

Plug-and-play technology is an important direction for future development of spacecraft and how to design controllers with less communication burden and satisfactory performance is of great importance for plug-and-play spacecraft. Considering attitude tracking of such spacecraft with unknown inertial parameters and unknown disturbances, an event-triggered adaptive backstepping controller is designed in this paper. Particularly, a switching threshold strategy is employed to design the event-triggering mechanism. By introducing a new linear time-varying model, a smooth function, an integrable auxiliary signal and a bound estimation approach, the impacts of the network-induced error and the disturbances are effectively compensated for and Zeno phenomenon is successfully avoided. It is shown that all signals of the closed-loop system are globally uniformly bounded and both the attitude tracking error and the angular velocity tracking error converge to zero. Compared with conventional control schemes, the proposed scheme significantly reduces the communication burden while providing stable and accurate response for attitude maneuvers. Simulation results are presented to illustrate the effectiveness of the proposed scheme.     

三轴轮控航天器姿态大角度机动控制器设计

研究了飞轮作为执行机构的航天器姿态大角度机动问题。建立了飞轮控制的姿态动力学模型;基于Lya-punov稳定性定理,设计了闭环控制器并给出了参数自适应律的解析表达式;分析了有界噪声作用下该模型的控制效果。仿真结果表明,所设计的控制器具有较强的鲁棒性和抗干扰能力。     

Event-triggered and consensus-based attitude tracking alignment for discrete-time multiple spacecraft system exploiting interference

This paper presents a discrete-time attitude control strategy with equi-global practical stabilizability for aligning the attitude of multiple spacecraft to a predesigned configuration according to a time-variant reference. By utilizing the interference of the wireless channel, the communication scheme designed in this paper can save communication resources, amount of computation, and energy proportionally to the number of spacecraft. The exact discrete-time model and approximate discrete-time model of the consensus-based spacecraft tracking system are given. Then the framework for the design of an event-triggered control scheme for the exact discrete-time system via its approximate models is developed, which avoids the periodic actuation, and Zeno behavior is proved to be excluded. Furthermore, the control scheme can handle the presence of the unknown fading channel. Finally, simulation results are presented to demonstrate the effectiveness of the control strategy.     

基于反步法的挠性航天器姿态镇定

利用反步法研究了一类挠性航天器的姿态镇定问题,提出一种基于模态观测器的反步控制设计方案.首先,构造挠性模态观测器对挠性模态变量及其变化率进行观测;其次,将角速度看成虚拟控制器,设计虚拟角速度镇定运动学模型与挠性模态变量组成的子系统;最后,利用反步法设计了一种非线性控制器使得角速度能够跟踪虚拟角速度,从而实现姿态镇定的目...     

Local controllability and stabilization of spacecraft attitude by two single-gimbal control moment gyros

The attitude control problem of a spacecraft underactuated by two single-gimbal control moment gyros （SGCMGs） is investigated. Small-time local controllability （STLC） of the attitude dynamics of the spacecraft-SGCMGs system is analyzed via nonlinear controllability theory. The conditions that guarantee STLC of the spacecraft attitude by two non-coaxial SGCMGs are obtained with the momentum of the SGCMGs as inputs, implying that the spacecraft attitude is STLC when the total angular momentum of the whole system is zero. Moreover, our results indi- cate that under the zero-momentum restriction, full attitude stabilization is possible for a spacecraft using two non-coaxial SGCMGs. For the case of two coaxial SGCMGs, the STLC property of the spacecraft cannot be determined. In this case, an improvement to the previous full attitude stabilizing control law, which requires zero-momentum presumption, is proposed to account for the singu- larity of SGCMGs and enhance the steady state performance. Numerical simulation results demonstrate the effectiveness and advantages of the new control law.     

挠性航天器的退步直接自适应姿态跟踪控制

针对参数不确定的挠性航天器姿态跟踪控制问题,提出了一种退步直接自适应控制算法。首先验证了挠性航天器动力学子系统的近似严格正实性,并设计了具有理想控制性能的参考模型;然后对以姿态四元数描述的运动学子系统设计常系数输出反馈中间控制律,使航天器姿态四元数输出渐近跟踪参考模型输出;最后退一步,对具有参数不确定特性的动力学子系统,基于非线性直接自适应控制理论和Lyapunov稳定性理论,设计了退步直接自适应姿态跟踪控制器,并证明了闭环系统的稳定性。仿真结果表明,所提控制方法能有效抑制挠性附件的振动,对挠性航天器的控制是有效的。     

Fault tolerant attitude control of under-actuated spacecraft: Theory and experiment

This paper investigates fault tolerant attitude control theory and experiment for under-actuated spacecraft with one reaction wheel completely broken and two others suffering actuator faults of partial loss of effectiveness or bias. A non-smooth robust adaptive fault tolerant control law is proposed under the zero-momentum and input saturation conditions. It shows that the available reaction wheels need to produce sufficient control torque for the fault tolerance. Such a new control method is implemented in a semi-physical simulation system of an air-bearing platform. Experimental results show the effectiveness of the proposed method in spacecraft practical engineering.     

考虑输入饱和与姿态角速度受限的航天器姿态抗退绕控制

 针对航天器姿态控制过程中同时存在输入饱和与姿态角速度受限的问题,提出了一种新型的姿态控制设计方法。该方法在保证系统渐近稳定的前提下,能够显式地给出输入力矩和姿态角速度的最大幅值,并通过引入一个时变锐度参数来增强系统对外部干扰的抑制能力;在此基础上,进一步考虑了由于四元数的冗余性所导致的退绕问题,设计了一组新的姿态偏差函数和偏差向量,使得控制器在满足上述约束的同时还具有抗退绕的优点。仿真结果表明,所提算法能够同时满足输入饱和与姿态角速度受限的约束,并且在较大外部干扰的情况下表现出了很强的鲁棒性,同时成功地规避了退绕现象。该算法为存在多重约束的航天器姿态控制问题提供了一个新的思路和解决方案,具有很好的实际应用价值。