Spacecraft Attitude Control System Research Articles

Multiple-fault diagnosis for spacecraft attitude control systems using RBFNN-based observers

In this paper, a novel multiple-fault diagnosis (MFD) scheme using radial basis function neural network (RBFNN)-based observers is presented for a spacecraft attitude control system (ACS) in the presence of external disturbances and nonlinear uncertainties. Based on dynamic and kinematic models, robust fault detection observers (FDOs) are designed to detect the simultaneous occurrence of actuator, gyro, and star sensor faults. Then, a series of RBFNN-based fault isolation observers (FIOs) are designed to decouple the faults of different components completely. This complete decoupling will guarantee that the diagnosis result of one component is not affected by the faults of other components; thus, multiple faults can be diagnosed simultaneously. To improve the accuracy of fault detection and reconstruction, disturbance compensation observers (DCOs) based on the RBFNN are also designed to compensate for the external disturbances. It is worth noting that the developed fault diagnosis scheme can be used to detect and isolate small faults. Finally, simulation results are presented to show the effectiveness and feasibility of the proposed method.

Bringing spacecraft into solar-oriented attitude by the measurements of a single-axis angular-rate sensor and an optical solar sensor

The algorithm of the turn of the spacecraft from an initial arbitrary angular position at an arbitrary angular rate to a solar-oriented attitude is investigated. Minimum essential equipment of the motion control system required for the purpose of ensuring maintenance of solar orientation is defined: a solar sensor, a single-axis angular-rate sensor, low-thrust liquid rocket engines. A solution of the problem of defining the spacecraft angular rate vector by the measurements of the deviation of the optical axis of the solar sensor from the sun vector and the single-axis angular-rate sensor is presented. The conditions under which control action on the rocket engines for the purpose of changing the value of the angular-rate vector for the Sun to get into the field of viewing of the solar sensor or for the spacecraft stabilization are defined. Mathematical modeling of the spacecraft attitude control system with the unknown initial state vector of motion is carried out. The results of mathematical modeling confirmed the efficiency of the proposed algorithm in terms of reducing propellant fuel consumption and high-speed performance. In comparison with the known methods of solving the problem of reducing angular speed (a lengthy process with the use of a magnetic system or a fast process with the use of a three-axis angular-rate sensor and rocket engines) the duration of the process of reducing angular speeds is the same as in normal operation, however, at the same time the problem of bringing spacecraft into the solar oriented attitude is solved.

Increasing of Reliability of Spacecraft Control System on Base of Robust Diagnostic Models and Division Principle in Parity Space

Different directions of creation high reliability integrate spacecraft control system are discussed on base of robust diagnostic models and division principle in parity space. Problems of synthesis spacecraft control system algorithms are examined with incomplete apriory and distorted current information, action of uncontrolled and random factors, information losses and equipment failures. The structure of onboard attitude control system is synthesized and control algorithms are chosen, which guarantee robust stability and failure stability in presence indignant factors and obstacles. An instrumental structure and operational modes of spacecraft attitude control system are described. Methods of dynamic research, computer technology and modeling particularities are indicated. Diagnostic and reconfiguration algorithms for onboard complex of connection, navigation, geodesy satellites and earth inspectoral satellite in prolonged space flight utilization are proposed. Testing procedure is contains two stage: discovering and eliminating faults. Given mathematical system model is researched by means of difference signals, which forms with arise at fault emergence. The failure character is established by deciding rules on base difference signals and measures to it eliminating are took. Questions of onboard spacecraft control system failure stable improving are discussed on base principle reconfiguration with apply to adaptive logic in testing and diagnostic algorithms. The mathematical system model is researching with implementation of analytic reserving. Difference signals are formed, which arise at fault appearance. The adaptive approach to development testing and diagnostic systems provide for realization of flexible logic of control system function to take into account factual onboard equipment state. Special attention is devote to problem influence liquid fuel reactive engine agility on spacecraft control attitude system dynamic characteristics and precision. The effectiveness of prepositional approaches and algorithms is confirmed by mathematical modeling results for several actual technical systems. Recommendations to their practical applications are given.

Fault modeling of general momentum exchange devices in spacecraft attitude control systems

This paper investigates the mechanism of various faults in momentum exchange devices. These devices are modeled as a cascade electric motor (EM) - variable speed drive(VSD) system. Considering the mechanical part of the EM and the VSD system, potential faults are reviewed and summarized. Then, a general fault model in a cascade multiplicative structure is established for momentum exchange devices. Based on this general model, various fault scenarios can be simulated and tested, and the possible outputs affected by faults can be appropriately visualized. Specifically, six types of working condition are identified, and the corresponding fault models are constructed. Using these fault models, the control responses using reaction wheels and single gimbal control moment gyros under various fault conditions can be demonstrated. The simulation results show the severities of the faults and demonstrate that the additive fault is more serious than the multiplicative fault from the viewpoint of control accuracy. Finally, existing fault-tolerant control strategies are briefly summarized and potential approaches including both passive and active ones accommodating gimbal fault of single gimbal control moment gyro are demonstrated.

Deep Generative Models-Based Anomaly Detection for Spacecraft Control Systems.

A spacecraft attitude control system provides mechanical and electrical control to achieve the required functions under various mission scenarios. Although generally designed to be highly reliable, mission failure can occur if anomalies occur and the attitude control system fails to properly orient and stabilize the spacecraft. Because accessing spacecraft to directly repair such problems is usually infeasible, developing a continuous condition monitoring model is necessary to detect anomalies and respond accordingly. In this study, a method for detecting anomalies and characterizing failures for spacecraft attitude control systems is proposed. Herein, features are extracted from multidimensional time-series data of a simulation of the attitude control system. Then, the artificial neural network learning algorithms based on two types of generation models are applied. A Bayesian optimization algorithm with a Gaussian process is used to optimize the hyperparameters for the neural network to improve the performance. The performance is evaluated based on the reconstruction error through the algorithm using the newly generated data not used for learning as input data. Results show that the detection performance depends on the operating characteristics of each submode in the operation scenarios and type of generation model. The diagnostic results are monitored to detect anomalies in operation modes and scenarios.

Fault Modeling, Estimation, and Fault-Tolerant Steering Logic Design for Single-Gimbal Control Moment Gyro

This brief addresses the single-gimbal control moment gyro (SGCMG) fault modeling, estimation, and tolerant-control steering logic design problem, aiming at enhancing the reliability and safety of spacecraft attitude control systems. The SGCMG is modeled as a two-loop system, including a wheel speed control loop and a gimbal rate control loop. Each loop contains an electrical motor (EM) and its corresponding variable speed drive (VSD), which may suffer from faults. By analyzing and modeling potential faults of the EM-VSD system, the SGCMG fault model is further developed. Then, a local adaptive fault estimator is proposed to reconstruct the total time-varying fault effects of each SGCMG. It is proven that the gimbal angle estimation error and fault estimation error converge to small compact sets containing zero. Moreover, leveraging estimated fault effects, a fault-tolerant steering logic is further developed to allocate the commanded attitude control torque properly such that the gimbal rate constraints are satisfied, and fault effects are compensated. To verify the proposed fault estimator and fault-tolerant steering logic, numerical simulations are carried out on an SGCMG-actuated spacecraft.

Observer-based reaction wheel fault reconstruction for spacecraft attitude control systems

Purpose The purpose of this paper is to achieve fault reconstruction for reaction wheels in spacecraft attitude control systems (ACSs) subject to space disturbance torques. Design/methodology/approach Considering the influence of rotating reaction wheels on spacecraft attitude dynamics, a novel non-linear learning observer is suggested to robustly reconstruct the loss of reaction wheel effectiveness faults, and its stability is proven using Lyapunov’s indirect method. Further, an extension of the proposed approach to bias faults reconstruction for reaction wheels in spacecraft ACSs is performed. Findings The numerical example and simulation demonstrate the effectiveness of the proposed fault-reconstructing methods. Practical implications This paper includes implications for the development of reliability and survivability of on-orbit spacecrafts. Originality/value This paper proposes a novel non-linear learning observer-based reaction wheels fault reconstruction for spacecraft ACSs.

Modelling the attitude dynamics of small spacecraft with a magnetic attitude control system in three-axis stabilization mode

The problem of modeling the attitude-control modes of small spacecraft with the use of electromagnetic systems, interacting with the Earths magnetic field is considered. A small spacecraft angular motion mathematical model is developed. A control law for magnetic attitude control system of small spacecraft is formulated. Results of satellite with magnetic attitude control system movement numerical modelling are presented.

Maximizing the Onboard Capability of the Spacecraft Attitude Control System Based on Optimal Use of Reaction Wheels

Maximizing the Onboard Capability of the Spacecraft Attitude Control System Based on Optimal Use of Reaction Wheels

Modeling the Angular Motion Dynamics of Small Spacecraft with a Magnetic Attitude Control System in a Three-Axis Stabilization Mode

The problem of modeling the attitude control modes of small spacecraft using electromagnetic systems interacting with the Earth’s magnetic field is considered. A mathematical model for the angular motion dynamics of small spacecraft has been developed. The control law for linear magnetic attitude control systems of small spacecraft is formulated. The results of our numerical modeling of the motion of a satellite with a magnetic attitude control system are presented.

Fault-Tolerant Attitude Stabilization Incorporating Closed-Loop Control Allocation Under Actuator Failure

This paper addresses the difficult problem of fault-tolerant control and closed-loop control allocation for spacecraft attitude control system with actuator failures, actuator saturation, and external disturbances. As a fundamental step, a modified fault diagnosis observer is proposed utilizing the iterative learning methodology to reconstruct the actuator failures in real time. On the basis of the previously reconstructed failure information, a fault-tolerant control scheme incorporating with a parameter adjusting law is presented to enforce the spacecraft attitude control system to reach the real sliding mode surface in finite time. Meanwhile, the singularity of control command will be avoided using the saturation function, and the chattering problem restrained by the adjusting law. Furthermore, with the concept of control allocation, a novel on-line closed-loop constrained optimal fault-tolerant control allocation scheme is employed to distribute the signals synthesized by the baseline controller over the redundant actuators with failures and constraints. The stability of the closed-loop fault-tolerant control allocation process is guaranteed by the theory of the closed-loop discrete-time feedback control system. The key achievement of the proposed systematic strategy is that the whole closed-loop attitude control system can theoretically be guaranteed to be stable. Numerical simulations are carried out to verify the effectiveness and superiority of the developed approach.

Adaptive Backstepping Sliding Mode Fault Tolerant Control for Satellite Attitude under Actuator Faults

Modern spacecraft missions place stringent performance requirements on the reliability and stability of spacecraft attitude control system. However, during long-term in-orbit mission, actuators may suffer faults. In this paper, we proposed an adaptive fault tolerant control law for attitude control under actuator failures and external disturbances. Firstly, the attitude dynamic model under actuator faults and attitude kinematics are described. Then, in order to solve the attitude control problem under actuator faults and external disturbances, an adaptive backstepping sliding mode fault tolerant control scheme is designed. According to Lyapunov theory, the closed-loop system is proved to be globally asymptotically stable. Finally, the numerical simulation results demonstrate that the proposed adaptive controller can achieve anticipative attitude control performance, fault information estimation and well fault-tolerant capability.

A Novel Electrodynamic Reaction Sphere Prototype for Spacecraft Attitude Control

This paper proposes an aerostatic-bearing supported electrodynamic reaction sphere prototype for ground experiments to validate the technical feasibility of the electrodynamic reaction sphere functioning as an alternative actuator for the spacecraft attitude control system. First, the detailed prototype configuration is introduced and the main structural parameters are designed utilizing the derived analytical electromagnetic torque model. Then a simple but effective measuring scheme and a calculation algorithm based on mouse optical sensors are proposed for the omnidirectional rotation speed measurement of the spherical rotor. Moreover, the special electromagnetic dynamic distortion effect (EDDE) induced by the rapid omnidirectional rotation of the spherical rotor is originally modeled and analyzed by means of the finite-element method (FEM) and the superposition principle. And a current distribution algorithm based on the EDDE coupling torque model is presented to handle the strong torque coupling brought about by omnidirectional rotation. Finally, the proposed models and algorithms are experimentally verified on the developed laboratory prototype. And the closed-loop omnidirectional rotation control at a speed up to 1500 r/min is achieved which validates the feasibility of the electrodynamic reaction sphere.

EVALUATION OF THE RELIABILITY OF COMPLEX TECHNICAL RECONFIGURATION SYSTEMS BY STATISTICAL MODELING METHOD

Goal. Assess the reliability of a complex technical system with periodic reconfiguration and compare the results obtained a similar system, but without reconfiguration. Materials and methods. In this article uses the method of statistical modeling (Monte Carlo) to assess the reliability of complex system. We using the normal and exponential distribution of failure time for modeling failures of system elements. Reconfiguration algorithm is the algorithm proposed for the attitude and orbit control system of spacecraft. Results. A computer program has been developed for assessing reliability on the basis of a statistical modeling method, which makes it possible to evaluate systems of varying complexity with exponential and normal distribution, as well as with and without periodic reconfiguration. A quantitative estimate of the reliability as a function of the probability of system failure is obtained. Conclusion. It has been demonstrated that a system with reconfiguration has the best reliability characteristics, both in the case of exponential and normal distribution of failures.

Star Image Prediction and Restoration under Dynamic Conditions.

The star sensor is widely used in attitude control systems of spacecraft for attitude measurement. However, under high dynamic conditions, frame loss and smearing of the star image may appear and result in decreased accuracy or even failure of the star centroid extraction and attitude determination. To improve the performance of the star sensor under dynamic conditions, a gyroscope-assisted star image prediction method and an improved Richardson-Lucy (RL) algorithm based on the ensemble back-propagation neural network (EBPNN) are proposed. First, for the frame loss problem of the star sensor, considering the distortion of the star sensor lens, a prediction model of the star spot position is obtained by the angular rates of the gyroscope. Second, to restore the smearing star image, the point spread function (PSF) is calculated by the angular velocity of the gyroscope. Then, we use the EBPNN to predict the number of iterations required by the RL algorithm to complete the star image deblurring. Finally, simulation experiments are performed to verify the effectiveness and real-time of the proposed algorithm.

On stability and stabilization of the linearized spacecraft attitude control system with bounded inputs

Lyapunov stability of the roll–yaw and pitch subsystems of a linearized spacecraft attitude control system are re-examined, along the lines of a previously proposed Jordan form-based approach. It is found that the roll–yaw subsystem is Lyapunov stable for inertially symmetric spacecraft with repeated eigenvalues on the imaginary axis, which cannot be asserted by the existing characteristic equation based approach. Globally stabilizing controllers with bounded linear feedback are then designed for such spacecraft and the optimal feedback gain is designed such that the convergence rate of the linearized closed-loop system is maximized. The proposed method is also applicable to inertially symmetric spacecraft with magnetic actuators.

On-orbit Reconfiguration Using Adaptive Dynamic Programming for Multi-mission-constrained Spacecraft Attitude Control System

For the on-orbit reconfiguration problem of spacecraft attitude control systems under multi-mission constraints, the idea of a reinforcement-learning algorithm is adopted, and an adaptive dynamic programming algorithm for on-orbit reconfiguration decision-making that is based on a dual optimization index is proposed. Two optimization objectives, total mission reward and total control cost (energy consumption), are defined to obtain the optimal reconfiguration policy of the spacecraft attitude control system reconfiguration, and the on-orbit reconfiguration model for multi-mission constraints is established. Then, based on the Bellman optimality principle, the optimal reconfiguration policy formulated by the discrete HJB equation is obtained. Since the HJB equation is difficult to solve accurately, a method of bi-objective adaptive dynamic programming is proposed to obtain the optimal reconfiguration policy. This method constructs a mission network and an energy network. The method then adopts a Q-learning-based algorithm to train the networks to estimate the values of total mission reward and total control cost to achieve the on-orbit optimal reconfiguration decision under multi-mission constraints. Simulation results for different cases demonstrate the validity and rationality of the proposed method.

Finite-time Extended State Observer based fault tolerant output feedback control for attitude stabilization

This work addresses the challenging problem of finite-time fault tolerant attitude stabilization control for the rigid spacecraft attitude control system without the angular velocity measurements, in the presence of external disturbances and actuator failures. Consider the severe circumstances with above failures and uncertainties, a novel continuous finite-time Extended State Observer is first established to observe the attitude angular velocity and the synthetic failure simultaneously. Unlike the existing observers, the finite-time methodology and Extended State Observer are utilized, to achieve the finite-time uniformly ultimately bounded stability of the attitude angular velocity and extended state observation errors. Furthermore, a novel continuous finite-time attitude controller is developed by using the nonsingular terminal sliding mode control and super-twisting method. The main feature of this work stems from our use of multiply advanced techniques or methodologies that enables the finite-time stability of the closed-loop attitude control system and the designed control scheme is continuous with the property of chattering restraining. Finally, numerical simulation results are presented to illustrate the effectiveness and fine performances of the finite-time observer and controller for the attitude control system.

Cooperative Game Theory-Based Optimal Angular Momentum Management of Hybrid Attitude Control Actuator

The next-generation space missions, such as the space moving target tracking mission and the agile attitude maneuvering mission and so on, propose a high requirement on spacecraft attitude control system. For such missions, hybrid attitude control actuators consisting of control moment gyro and reaction wheel, which can not only offer large control torque but also achieve high control precision, is the best alternative choice. For this hybrid actuator system, the angular momentum management is vital. To handle the momentum management problem, an optimal angular momentum strategy based on cooperative game theory is proposed. The cooperative game model is constructed according to the quadratic programming problem to achieve the minimization of control moment gyro gimbal angular speed and reaction wheel angular acceleration. The proposed cooperative game theory steering logic has overcome the control moment gyro singular problem and reaction wheel saturation problem of the hybrid system. In addition, the energy cost of the hybrid actuator system is reduced. Five groups of simulation scenarios are carried out to demonstrate the effectiveness of the proposed steering logic.

In-Orbit Spacecraft Inertia, Attitude, and Orbit Estimation Based on Measurements of Magnetometer, Gyro, Star Sensor and GPS Through Extended Kalman Filter

Spacecraft may exhibit changes of its moments and products of inertia in-orbit due to several reasons. In this case, knowledge of spacecraft moments and products of inertia represents an utmost importance for the spacecraft attitude and orbit control system (AOCS). The contribution of the current research article is to estimate in-orbit spacecraft moments and products of inertia based on measurements of magnetometer, gyro, star sensor, and GPS through extended Kalman filter without test slews while being able to estimate attitude and orbital states at the same time. The proposed solution is also able to converge despite large initial estimation errors.