Reaction Wheel Faults Research Articles

A Reliable Deep Learning Approach for Time-Varying Faults Identification: Spacecraft Reaction Wheel Case Study

Reaction wheels are key components for the spacecraft attitude control subsystems. Faults in reaction wheels may lead to high energy consumption, lack of spacecraft attitude control, and in case of failure, loss of the spacecraft. The accurate identification of reaction wheels anomalies is a challenging task due to the internal nonlinearities of the reaction wheels. This study proposes a fast and accurate end-to-end architecture for detecting and identifying the anomalies occurring in spacecraft reaction wheels using One-Dimensional Convolutional Neural Network (1D-CNN) with Long Short-Term Memory (LSTM) network architecture. 1D-CNN is used to capture the useful features from the raw residual signals. The Long Short-Term Memory layer is used due to its effectiveness in handling the time series data and its capabilities for learning long-term dependencies. The proposed architecture is directly trained using the raw torque residual signals captured from a 3-axis attitude control subsystem simulation model. In this way, this scheme eliminates the need for a specific feature extraction method. Results showed that the proposed algorithm represents a reliable and robust anomaly detection and identification mechanism with compact system architecture. Furthermore, the obtained results revealed the superiority and generalizability of the proposed model in diagnosing time-varying reaction wheel faults over other recent approaches. Ultimately, the proposed approach is considered to be a generic fault diagnosis architecture for safety-critical systems. The dataset is available for download at: https://dx.doi.org/10.21227/jr1c-bm66.

Fault-tolerant attitude control of miniature satellites using reaction wheels

An adaptive fault-tolerant nonlinear control scheme is proposed for precise 3-axis attitude tracking of miniature spacecraft in the presence of control input saturation, model uncertainties, external disturbances, and reaction wheel faults. Two configurations of reaction wheel assembly are examined in this paper, (A1) Traditional four wheel setup where three reaction wheels are in orthogonal configuration along with one oblique wheel; and (A2) Four wheels in a pyramid configuration. Multiplicative reaction wheel faults are considered along with complete failure of one wheel (A1) and two wheels (A2). The proposed control algorithm does not require an explicit fault detection and isolation mechanism and therefore failure time instants, patterns, and values of actuator failures remain unknown to the designer. The stability conditions for robustness against model uncertainties and external disturbances are derived using Lyapunov stability theory to establish the regions of asymptotic stabilization. The benefits of the proposed control methodology are analytically authenticated and also validated using hardware-in-the-loop simulations. The experimental results clearly establish the robustness of the proposed autonomous control algorithm for precise attitude tracking in the event of reaction wheel faults and failures.

Adaptive extended-state observer-based fault tolerant attitude control for spacecraft with reaction wheels

This study presents an adaptive second-order sliding control scheme to solve the attitude fault tolerant control problem of spacecraft subject to system uncertainties, external disturbances and reaction wheel faults. A novel fast terminal sliding mode is preliminarily designed to guarantee that finite-time convergence of the attitude errors can be achieved globally. Based on this novel sliding mode, an adaptive second-order observer is then designed to reconstruct the system uncertainties and the actuator faults. One feature of the proposed observer is that the design of the observer does not necessitate any priori information of the upper bounds of the system uncertainties and the actuator faults. In view of the reconstructed information supplied by the designed observer, a second-order sliding mode controller is developed to accomplish attitude maneuvers with great robustness and precise tracking accuracy. Theoretical stability analysis proves that the designed fault tolerant control scheme can achieve finite-time stability of the closed-loop system, even in the presence of reaction wheel faults and system uncertainties. Numerical simulations are also presented to demonstrate the effectiveness and superiority of the proposed control scheme over existing methodologies.

Fault-Tolerant Attitude Stabilization for Satellites Without Rate Sensor

A fault-tolerant control approach without rate sensors is presented for the attitude stabilization of a satellite being developed. External disturbances, reaction wheel faults, actuator saturation, and unavailable angular velocity are addressed. A sliding-mode observer is proposed by using attitude feedback only, and the unavailable angular velocity is estimated by this observer in finite time. Using the attitude and the estimated velocity, another sliding-mode observer is proposed to reconstruct actuator faults and disturbances. It is proven that reconstruction with zero observer error is achieved in finite time. With the reconstructed value, a velocity-free controller is then developed to asymptotically stabilize the attitude. Simulation results are also provided to verify the effectiveness of the proposed approach.

Reaction Wheel Fault Compensation and Disturbance Rejection for Spacecraft Attitude Tracking

A novel attitude tracking control scheme is proposed for rigid spacecraft to simultaneously compensate for reaction wheel faults and reject external disturbances. The reconstruction of the reaction wheel faults and disturbances is treated as a problem of observing the state of a linear system with unknown inputs. A terminal sliding mode observer is proposed to reconstruct the reaction wheel faults and disturbances. A Lyapunov-based analysis shows that the observer asymptotically converges to the actual faults and disturbances with a finite time convergence. Then, with the reconstructed faults and disturbance information, a compensation control law is developed to guarantee that the desired attitude trajectories are followed in finite time. The key feature of the proposed control strategy is that it globally asymptotically stabilizes the system, even in the presence of reaction wheel faults and external disturbances. The attitude tracking performance using the proposed compensation control is evaluated through a numerical example.

적응 법칙을 적용한 슬라이딩 모드 제어를 이용한 위성의 고장 허용 제어

This paper proposes fault tolerant control laws using sliding mode control and adaptation laws for a satellite with reaction wheel faults. Considering system parameter errors and faults uncertainties in the dynamics of satellite, the control laws were designed. It was assumed that only reaction wheel failures occurred as faults. The reaction wheel faults were reflected in the multiply form. Because the proposed control laws satisfy the Lyapunov stability theorem, the stability is guaranteed. Through computer simulation, it was assured that the proposed adaptive sliding mode controller has a better performance than the existing sliding mode controller under unstable angular rates.

Fault-Tolerant Attitude Control for Flexible Spacecraft Without Angular Velocity Magnitude Measurement

S INCE some catastrophic faults or failures may be induced due to the aging or damage of actuators and sensors during the mission of a spacecraft, those faults would lead to performance degradation of the spacecraft attitude control system or even result in the specified aerospacemission failure. Therefore, fault tolerance of the spacecraft attitude control system is one of the key issues that needs to be addressed. With a view to tackle such a challenge, fault-tolerant control (FTC) has received considerable attention in order to enhance the spacecraft reliability and to guarantee the attitude control performance [1–5]. In [5], an adaptive FTC is developed for the flexible spacecraft attitude tracking system where the persistent bounded disturbances, unknown inertia parameter, and even two types of reaction wheel faults are successfully accommodated. Indeed, the aforementioned approaches offer many attractive conceptual features, but at the same time they are derived based on the availability of direct and exact measurements of both the angular velocity and the attitude orientation. It is important to note, however, that when it comes to practical implementation, the angular velocity measurements are not always available because of either cost limitations or implementation constraints. Motivated from such a practical consideration, it is therefore highly desirable to develop partial state feedback attitude control strategies with spacecraft angular velocity measurements eliminated. The issue has been addressed in the literature by using observer-based control [6,7], Lyapunov-based control [8,9], and variable structure control [10] under normal operation of spacecraft. In this work, we provide solutions to two different problems of the flexible spacecraft attitude control system. The first problem consists of developing a control law to perform a attitude stabilization maneuver without angular velocity magnitude. In contrast with the velocity-free control schemes available in the literature, the presented approach can guarantee the attitude control performance be greatly robust to external disturbances and unknown inertia parameters. The second problem solved is the casewhere both loss of control effectiveness and additive fault occur in actuators simultaneously, but the attitude still requires stabilization with high resolution. To the best knowledge of the authors, this study is the first attempt to deal with fault-tolerant attitude stabilization control for flexible spacecraft with the angular velocity magnitude eliminated. The Note is organized as follows. Section II presents the mathematical model and attitude control problems formation of a flexible spacecraft under normal and faulty actuator conditions. Section III presents the proposed fault-tolerant attitude stabilization controller without velocity magnitude in the presence of two types of actuator faults. Simulation results to demonstrate various features of the proposed scheme are given in Sec. IV followed by conclusions in Sec. V.