Fault Tolerant Attitude Control Research Articles

Adaptive Fault-Tolerant Spacecraft Attitude Control Design With Transient Response Control

This paper proposes an adaptive fault tolerant attitude controller, based on variable structure control, to address tracking control problem of spacecraft in the presence of unknown actuator failure, control input saturation and external disturbances. In contrast to traditional robust fault tolerant attitude controllers, the proposed controller is capable of controlling the transient response of the closed loop system by means of a dedicated parameter. Also this method does not require exact knowledge of the actuator faults and is implemented with uncertain value of fault information. By adjusting a simple parameter dynamically and using Lyapunov direct method and the properties of quaternion representation, the ultimate boundedness of attitude and angular velocity errors in presence of external disturbances is proven. Numerical simulations used to prove the success of proposed controller in achieving high attitude performance in the presence of external disturbances, inexact knowledge of fault information, actuator failures and control input saturation.

RETRACTED ARTICLE: Immersion and invariance based fault tolerant adaptive spacecraft attitude control

In this paper, an immersion and invariance (I&I) adaptive fault tolerant satellite attitude tracking control scheme is proposed. The proposed controller is capable of track the desired trajectory in the presence of unknown actuator multiplicative faults and unknown inertial matrix. Also based on Lyapunov direct method, all closed loop signals are proven to be globally asymptotically stable. The main advantage of this controller is improving closed loop performance while maintaining stability in the presence of unknown actuator faults. This method does not rely on certainty equivalence principle so it can be used to control the transient response of overall closed loop system by means of controlling the parameter estimation behavior which is not possible in traditional adaptive control. Numerical simulations are performed to demonstrate the effectiveness of proposed control scheme.

Fault tolerant spacecraft attitude control by multiple control processors1

This paper considers fault tolerant attitude control problem of spacecraft under intermittent faults that occur in the control processor. A novel control framework based on multiple redundant control processors is provided, and a state-dependent switching law among these processors is proposed to stabilize the attitude dynamics without requiring control reconfiguration in each control processor when faults occur. Moreover, a probability-based method is provided to find the minimal number of control processors that are needed for attitude stabilization. Simulation results show the efficiency of the proposed methods.

Finite-time fault tolerant attitude stabilization control for rigid spacecraft

A sliding mode based finite-time control scheme is presented to address the problem of attitude stabilization for rigid spacecraft in the presence of actuator fault and external disturbances. More specifically, a nonlinear observer is first proposed to reconstruct the amplitude of actuator faults and external disturbances. It is proved that precise reconstruction with zero observer error is achieved in finite time. Then, together with the system states, the reconstructed information is used to synthesize a nonsingular terminal sliding mode attitude controller. The attitude and the angular velocity are asymptotically governed to zero with finite-time convergence. A numerical example is presented to demonstrate the effectiveness of the proposed scheme.

Finite‐time fault tolerant attitude control for over‐activated spacecraft subject to actuator misalignment and faults

A finite-time attitude compensation control scheme is developed for an over-activated rigid spacecraft subject to actuator faults, misalignment, external disturbances and uncertain inertia parameters. The controller is synthesised based on the sliding mode control theory, and guarantees the finite-time reachability of the system states. A sufficient condition for the controller to accommodate misalignment and faults of actuator is presented. An optimised control allocation algorithm based on the Karush–Kuhn–Tucker condition is then applied to distribute the commanded control to each actuator, and optimise the consumption of energy. Numerical simulation results are presented that highlight the performance benefits of the control law.

Real-Time Nonlinear Attitude Control System for Nanosatellite Applications

This paper develops a fault-tolerant attitude controller for next-generation nanosatellites. The proposed fault-tolerant attitude control algorithms in this study are based on first-order and high-order sliding-mode control theories as well as fuzzy logic systems to achieve low cost and real-time autonomy. A locally asymptotically stable adaptive fuzzy first-order sliding-mode controller is chosen as the best solution to the local attitude control tracking problem. This novel fault-tolerant controller is validated by simulation results with reaction wheel Coulomb friction, saturation, noise, dead zones, bias faults, and external disturbances. Simulation and testing results presented in the paper demonstrate that the attitude control system can provide successful pointing and tracking in the presence of system uncertainties for a specified class of reaction wheel failures.

A Fault-Tolerant and Anti-Disturbance Control Based on Sliding Mode Iterative Learning Law for Attitude of Satellite

To cope with the problem of the degradation of actuation effectiveness caused by actuator deflection or fault in the attitude and orbit control system (AOCS) of spacecraft on-orbit, an attitude fault-tolerant and anti-disturbance control scheme is proposed based on a sliding mode iterative learning law, in which the pseudo control input is applied to design the sliding mode controller to ensure the AOCS tracks a reference trajectory precisely after some fault occurred; By analyzing the Lyapunov stability, a novel adaptive iterative learning law is developed, which in term of the tracking error, determine some parameters in controller on-line to address the actuator failure and external disturbance. Numerical simulation experiments show that the fault-tolerant and anti-disturbance controller can ameliorate actuation malfunction and compensate the influence of external disturbance effectively.

Velocity-free fault-tolerant control allocation for flexible spacecraft with redundant thrusters

This paper proposes a novel velocity-free nonlinear proportional-integral (PI) control allocation scheme for fault-tolerant attitude control of flexible spacecraft under thruster redundancy. More specifically, the nonlinear PI controller for attitude stabilisation without using body angular velocity measurements is first designed as a virtual control of the control allocator to produce the three-axis moments, and can ultimately guarantee uniform boundedness of the closed-loop system in the presence of external disturbances and possible faults. The associated stability proof is constructive and accomplished by the development of passivity filter formulations together with the choice of a Lyapunov function containing mixed terms involving the various states. Then, a robust least-squares-based control allocation is employed to deal with the problem of distributing the three-axis moments over the available thrusters under redundancy, in which the focus of this control allocation is to find the optimal control vector of the actuator by minimising the worst-case residual, under the condition of thruster faults and control constraints like saturation. Simulation results using the orbiting flexible spacecraft model show good performance under external disturbances and even in different thruster fault scenarios, which validates the effectiveness and feasibility of the proposed scheme.

Spacecraft Attitude Fault Tolerant Control with Terminal Sliding-Mode Observer

AbstractA velocity-free attitude fault tolerant control scheme is presented to stabilize spacecraft attitude. A terminal sliding-mode observer is developed to reconstruct system states. With the reconstructed attitude and angular velocity, a control law is synthesized without any knowledge on actuator faults. The controller guarantees all the signals of the closed-loop attitude system to be uniformly ultimately bounded even in the presence of actuator fault and external disturbance. The control power is rigorously ensured to be within the maximum magnitude of output torque. An illustrative example is presented to evaluate the control performance.

A31 コントロールモーメントジャイロ搭載人工衛星の耐故障姿勢制御系(M-OS13-7 飛翔体の制御,M-OS13 宇宙機・宇宙ロボットのダイナミクスと制御,「海を越え,国を越え,世代を超えて!」)

In recent years, it has been required accurate and agile attitude control of satellites. For this purpose, the necessity of Control Moment Gyros (CMGs) has been increasing, which can generate much higher torque than reaction wheels which are used as conventional spacecraft actuators. Furthermore, it is important for the attitude control systems to have function of fault tolerant. In a conventional 4 CMG system, the CMGs are placed in a pyramid mounting arrangement with skew angle set to 54.74 degrees. The maximum angular momentum of the CMG system is changed according to the skew angle. The suitable skew angle should be designed considering normal and failure situations. Moreover, the suitable parameters of the satellite attitude and CMG control system are changed according to the skew angle. Therefore, this paper proposes a design method of the fault-tolerant attitude control system. In the proposed method, the skew angle and the parameters of the control system are tuned simultaneously by genetic algorithm. To verify the fault-tolerant of the proposed method, numerical simulations in case that the one CMG is failed are carried out.

Spacecraft Attitude Fault Detection and Recovery Using Non-Linear Observer and Reconfigurable Controller

This paper addresses fault tolerant attitude control through the development of a fault observer and re-configurable control law. Using attitude sensor measurements for angular position and velocity, an estimate of the true torque on all three axes is accomplished using a pair of super twisting sliding mode observers. Modifications on the `broken' super twisting observer is applied in order to accommodate additional sensor feedback inputs. Using this method, reconstruction of torque faults can be accomplished and fault information is then sent to a re-configurable controller which switches to an appropriate control law to recover and mitigate the effects of the actuator fault. Simulation results are presented to show fault reconstruction and recovery with attitude stabilization in the presence of orbital disturbances - some which are partially unknown to both controller and observer.

Fault-Tolerant Attitude Control for Spacecraft Under Loss of Actuator Effectiveness

ATPRESENT, a large number of engineers have assorted to faulttolerant control (FTC) to enhance the system reliability and to guarantee the control performance (see, e.g., [1–4] and references therein), and several investigations on the application of FTC to spacecraft attitude maneuvers have also been considered. For instance, based on the dynamics inversion and time-delay control, a passive fault-tolerant controller was developed in [5] to achieve attitude tracking of a rigid satellite. Cai et al. [6] proposed an indirect adaptive fault scheme for spacecraft attitude tracking problem under thruster faults. In [7], a control augmentation method, similar to adaptive fault-tolerant control, was adopted for the flexible spacecraft attitude tracking. However, all the preceding FTC results can only tolerate limited predetermined faults and have great conservativeness due to its implementing a fixed controller only. In this work, the attitude stabilization of rigid spacecraft in the presence of partial loss of actuator effectiveness is investigated. Based on adaptive backstepping technique, a nominal attitude controller is derived first for the normal spacecraft system in the face of external disturbances. Then the case of the partial loss of reactionwheel-effectiveness fault is considered, and the faulty attitude system with time-varying gain is ultimately decoupled into three auxiliary systems by appropriate transformation. Moreover, for each auxiliary system, an implicit estimation filter is proposed to estimate the actuator fault correspondingly, and in the meantime, a new adaptive fault-tolerant controller is synthesized according to the estimated fault to guarantee that outputs of the auxiliary system can follow the normal attitude control command signals. By viewing the tracking error as another disturbance entering the system dynamics, with the robustness of the nominal controller to external disturbances, the online fault tolerance can be achieved. In contrast to preceding FTC results, the main contributions of this study include the following: 1) The proposed strategy can react to the fault online and in real time, and thus the conservativeness of the controller can be reduced largely. 2) Although three implicit estimation filters are developed in the fault-tolerant-controller design, it does not require the precise reconstruction of the faults. Thus, large computation power can be saved and also the response time can be reduced effectively. This Note is organized as follows: Sec. II briefly presents the spacecraft attitude model and control problems. In Secs. III and IV, adaptive backstepping attitude controllers are derived, respectively, with and without partial loss of actuator effectiveness fault. Simulation results of a rigid spacecraft are given in Sec. V, followed by conclusions in Sec. VI.

Robust fault-tolerant control for spacecraft attitude stabilisation subject to input saturation

This study investigates the robust fault-tolerant attitude control of an orbiting spacecraft with a combination of unknown actuator failure, input saturation and external disturbances. A fault-tolerant control scheme based on variable structure control is developed that is robust to the partial loss of actuator effectiveness, where the actuators experience a reduced actuation but are still active. The results are then extended to the case in which some of the actuators fail completely, although some redundancy in actuation is assumed. In contrast to traditional fault-tolerant control methods, the proposed controller does not require knowledge of the actuator faults and is implemented without explicit fault detection, separation and accommodation processes. Moreover, the designed controller rigorously enforces actuator saturation constraints. The associated stability proof is constructive and develops a candidate Lyapunov function that shows the attitude and the angular velocities converge asymptotically to zero. Simulation studies are used to evaluate the closed-loop performance of the proposed control solution and illustrate its robustness to external disturbances, unknown actuator faults and even input saturation.

Fault-tolerant sliding mode attitude control for flexible spacecraft under loss of actuator effectiveness

In this paper, a novel fault-tolerant attitude control synthesis is carried out for a flexible spacecraft subject to actuator faults and uncertain inertia parameters. Based on the sliding mode control, a fault-tolerant control law for the attitude stabilization is first derived to protect against the partial loss of actuator effectiveness. Then the result is extended to address the problem that the actual output of the actuators is constrained. It is shown that the presented controller can accommodate the actuator faults, even while rejecting external disturbances. Moreover, the developed control law can rigorously enforce actuator-magnitude constraints. An additional advantage of the proposed fault-tolerant control strategy is that the control design does not require a fault detection and isolation mechanism to detect, separate, and identify the actuator faults on-line; the knowledge of certain bounds on the effectiveness factors of the actuator is not used via the adaptive estimate method. The associated stability proof is constructive and accomplished by the development of the Lyapunov function candidate, which shows that the attitude orientation and angular velocity will globally asymptotically converge to zero. Numerical simulation results are also presented which not only highlight the ensured closed-loop performance benefits from the control law derived here, but also illustrate its superior fault tolerance and robustness in the face of external disturbances when compared with the conventional approaches for spacecraft attitude stabilization control.

Adaptive fuzzy fault-tolerant attitude control of spacecraft

This paper investigates the attitude control of spacecraft in the presence of unknown mass moment of inertia matrix, external disturbances, actuator failures, and control input constraints. A robust adaptive controller is proposed with the utilization of fuzzy logic and backstepping techniques. The unit quaternion is employed to describe the attitude of spacecraft for global representation without singularities. The system uncertainty is estimated by introducing a fuzzy logic system. The adaptive mechanism has only two parameters to be adapted on-line because the adaptive law of the proposed controller is derived from the norm of the weight matrix. The stability of the closed-loop system is guaranteed by Lyapunov direct approach. Results of numerical simulations state that the proposed controller is successful in achieving high attitude performance in the presence of parametric uncertainties, external disturbances, actuator failures, and control input constraints.

Satellite Attitude Control with a Modified Iterative Learning Law for the Decrease in the Effectiveness of the Actuator

A fault tolerant satellite attitude control scheme with a modified iterative learning law is proposed for dealing with actuator faults. The actuator fault is modeled to reflect the degradation of actuation effectiveness, and the solar arrayinduced disturbance is considered as an external disturbance. To estimate the magnitudes of the actuator fault and the external disturbance, a modified iterative learning law using only the information associated with the state error is applied. Stability analysis is performed to obtain the gain matrices of the modified iterative learning law using the Lyapunov theorem. The proposed fault tolerant control scheme is applied to the rest-to-rest maneuver of a large satellite system, and numerical simulations are performed to verify the performance of the proposed scheme.

Fault tolerant satellite attitude control using solar radiation pressure based on nonlinear adaptive sliding mode

An adaptive fault tolerant nonlinear control design based on the theory of sliding mode is proposed to control the attitude of a satellite using solar radiation pressure. The system comprises of a satellite with two-oppositely placed solar flaps. The nonlinear model describing the system is used to derive an adaptive fault tolerant control law, based on Lyapunov stability theorem, in the presence of unknown, slow-varying satellite mass distribution and solar parameter. Using this control law the solar flaps are suitably rotated to achieve desired satellite attitude performance. The detailed numerical simulation of the governing nonlinear system equation of motion including the effects of various system parameters on the controller performance, establishes the feasibility of the proposed adaptive control strategy in comparison with the sliding mode control without adaptation. This paper also examines several scenarios including sudden failure of one of the solar flaps, occurrence of an abrupt blockage of one of the rotating solar flaps, and occurrence of a periodic actuator fault. The numerical results show the robustness of the proposed adaptive control scheme in controlling the satellite attitude in the presence of external disturbances as well as in the event of failure of one of the solar flaps.

Fault-Tolerant Attitude Control Systems of the Communication and Navigation Spacecraft

We present new results on creation and employment of nonlinear methods, algorithms and software for dynamic research of the precision faulttolerant gyromoment attitude control systems of the Russian spacecrafts for communication, navigation and geodetic purposes.

Channelization: the two-fault tolerant attitude control function for the Space Station Freedom

The Space Station Freedom was, from the mid-1980's through 1993, the design for an international orbiting laboratory facility. The Space Station Freedom was comprised of "utility" systems, such as power generation and distribution, thermal management, and data processing, and "user" systems such as communication and tracking, propulsion, payload support, and guidance, navigation, and control. These systems are required to work together to provide various station functions. To protect the lives onboard and the investment in the station, the systems and their connectivity had to be designed to continue to support critical functions after any single fault for early assembly stages, and after any two faults for later stages. Of these critical functions, attitude control was the most global, incorporating equipment from nearly all major systems. The challenge was to develop an architecture, or integration, of these systems that would achieve the specified level of fault tolerant attitude control and operate, autonomously, for the three-month unmanned periods during the assembly process. Additionally, this architecture had to maintain the desired utility of the station for each stage of the assembly process. This paper discusses the approach developed for integrating the systems such that the fault tolerance requirements were met for all stages of assembly. Some of the key integration issues are examined and the role of analysis tools are described. The resultant design was a highly channelized one, and the reasons and the benefits of this design will be explored. The final design was accepted by the Space Station Control Board as the design baseline in July 1992.