Spacecraft Attitude Control System Research Articles

Adaptive sliding mode and RBF neural network based fault tolerant attitude control for spacecraft with unknown uncertainties and disturbances

Taking the external disturbance, model uncertainty, actuator failure, and actuator saturation into consideration, this paper investigates the nonlinear fault-tolerant attitude control problem for the spacecraft. First, to deal with the disturbance and uncertainty with unknown boundaries, an adaptive sliding mode control method is proposed to stabilize the state variables of the spacecraft attitude control system. Then the actuator failure and saturation are further considered, and the second spacecraft fault-tolerant attitude controller is derived based on adaptive sliding mode control and radial basis function (RBF) neural networks. The adaptive control gains reduction technique is applied in the design process, which can weaken the chattering phenomenon of the controller to some extent, and the stability of the attitude control system is analyzed through Lyapunov theory. In the proposed controller, model information and external disturbance are not required and only the system states are needed. Furthermore, the boundaries of the model uncertainty, external disturbance, actuator fault and saturation are assumed to be existing but unknown by the proposed controllers. These features make the proposed attitude controllers need few modeling information of the spacecraft, or maintain strong robustness even if the model or external environment occurs significant changes. Finally, numerical simulations demonstrate the great performance of the proposed fault-tolerant attitude control method.

Attitude control of combined spacecraft with fuzzy neural network disturbance observer

A finite-time control strategy based on a fuzzy neural network disturbance observer (FNNDO) and nonsingular terminal sliding mode (NTSM) is proposed for the attitude control system of a combined spacecraft in the presence of non-cooperative targets with competitive torque output. First, a mathematical model of the combined spacecraft attitude is established with the service spacecraft as the reference. Then, the external disturbances and competitive torque output from non-cooperative targets are treated as generalized disturbances, and FNNDO is employed for tracking and compensation. Subsequently, a NTSM controller is designed to achieve finite-time attitude takeover control of non-cooperative targets. The stability of the disturbance observer and controller is proven using Lyapunov stability theory. Simulation results demonstrate that this control strategy effectively handles the competitive actions of non-cooperative targets while rapidly stabilizing the combined spacecraft’s attitude at the desired values.

Design of anti-unwinding attitude coupling controller for flexible spacecraft using positive position feedback control

Flexible vibration has a great impact on flexible spacecraft attitude control, which will reduce the pointing accuracy of the spacecraft platform and bring severe challenges to the design of a high-precision attitude control system for flexible spacecraft. Aiming at the problem of attitude and vibration coupling control of flexible spacecraft, an anti-unwinding attitude coupling controller using the positive position feedback (PPF) control is proposed in this paper. The model compensation control term is constructed based on the prior information to improve the tracking performance. The proposed attitude coupling control method can effectively suppress the flexible vibration while achieving more accurate attitude control. The obtained closed-loop system under the proposed control scheme is asymptotically stable, which is proved by the Lyapunov stability theory. The numerical simulation illustrates that the proposed method can effectively improve the attitude control accuracy of the flexible spacecraft and is capable of large-angle attitude maneuver control because of its prominent performance in attitude tracking and its unwinding-free performance.

Refined sliding mode disturbance observer‐based finite‐time composite control for Euler–Lagrange systems with multiple disturbances

AbstractA wide range of practical control systems such as robot manipulators and spacecrafts can be modeled by Euler–Lagrange systems. On one hand, the requirements for system control accuracy, response speed, and robustness are ever increasing. On the other hand, the control performances are inevitably degraded by multiple disturbances. In this paper, a novel finite‐time composite control law is proposed for a class of Euler–Lagrange systems subject to multiple heterogeneous disturbances including a neutrally stable disturbance and a norm‐bounded disturbance. More specifically, a refined sliding mode disturbance observer (RSMDO) is proposed to estimate and reject the neutrally stable disturbance in the feedforward channel, while an adaptive nonsingular backstepping control (ANBC) is designed in the feedback channel to stabilize the system and attenuate the observer error as well as the norm‐bounded disturbance. The proposed RSMDO can not only fully utilize the disturbance information, but also quantify the convergence time and steady‐state accuracy of the estimation error. The finite‐time stability analysis is carried out for the closed‐loop system. Finally, an example of spacecraft attitude control system is given to demonstrate the effectiveness of the proposed methods.

A data-driven configurability evaluation method for spacecraft control systems

<p style='text-indent:20px;'>To release severe constraints of spacecraft on orbit resources (in-cluding computing resources, hardware resources and energy resources), the data-driven reconfigurability evaluation of spacecraft attitude control system is studied in this paper. Firstly, the reconfiguration capability is quantitatively described based on the data forms of stable kernel representation and stable image representation of spacecraft control system subject to noise. Then, based on the obtained reconfigurability index, the maximum boundary of system re-configurability is given, which provides theoretical guidance for the design of autonomous reconfiguration strategy. Finally, an example is employed to verify the effectiveness and correctness of the proposed method.</p>

A Hybrid Model-Based and Data-Driven Framework for Automated Spacecraft Fault Detection

Traditional fault management can be an onerous task and robust automated solutions are increasingly necessary to accommodate the complexities of modern space systems and mission operations. The present work proposes a hybrid framework for performing automated spacecraft fault detection by leveraging the benefits of both model-based and data-driven approaches. The framework uses a system model to generate residual data that are subsequently fed into a data-driven residual analysis stage. The framework was verified by using data from a hardware-in-the-loop test campaign in which faults were injected into a spacecraft attitude control system, and successfully identified. The fault detection approach implemented using this framework outperformed results obtained from expert-tuned fault detection parameters. Overall, the proposed framework is a promising alternative for sustainable fault detection and mission operations suitable for complex space systems.

Artificial-Intelligence-Based Quantitative Fault Diagnosability Analysis of Spacecraft: An Information Geometry Perspective

To provide a theoretical foundation for the design of spacecraft and a reference for their on-orbit adjustment, this study develops methods for the quantitative diagnosability analysis of spacecraft through the introduction of a Riemannian manifold and artificial intelligence into a diagnosability analysis framework. These developed methods have three main advantages. First, they do not rely on any assumption regarding the statistical distribution of the observations. Second, all types of faults can be analyzed without information loss. Third, the computational burden is reduced, making it possible to perform on-orbit fault diagnosability analysis. The effectiveness and feasibility of the proposed methods are then verified via a numerical simulation and a spacecraft attitude control system.

Magnetometer-Only Kalman Filter Based Algorithms for High Accuracy Spacecraft Attitude Estimation (A Comparative Analysis)

Kalman Filter (KF) based algorithms are the most frequently employed attitude estimation algorithms. Typically, a fully observable system necessitates the use of two distinct sensor types. Therefore, relying on a single sensor, such as a magnetometer, for spacecraft attitude estimation is deemed to be a challenge. The present investigation centers on utilizing magnetometers as the exclusive sensor. Several KF based estimation algorithms have been designed and evaluated to give the designer of spacecraft Attitude and Orbit Control System (AOCS) the choice of a suitable algorithm for his mission based on quantitative measures. These algorithms are capable of effectively addressing nonlinearity in both process and measurement models. The algorithms under examination encompass the Extended Kalman Filter (EKF), Sequential Extended Kalman Filter (SEKF), Pseudo Linear Kalman Filter (PSELIKA), Unscented Kalman Filter (USKF), and Derivative Free Extended Kalman Filter (DFEKF). The comparison of the distinct algorithms hinges on key performance metrics, such as estimation error for each axis, computation time, and convergence rate. The resulting algorithms provide numerous benefits, such as diverse levels of high estimation accuracy (with estimation errors ranging from 0.014o to 0.14o), varying computational demands (execution time ranges from 0.0536s to 0.0584s), and the capability to converge despite large initial attitude estimation errors (which reached 170o). These properties render the algorithms appropriate for utilization by spacecraft designers in all operational modes, supplying high-precision attitude estimations better than (0.5o) despite high magnetometer noise levels, which reached (200 nT).

Sun-pointing safe control for atmospheric environment monitoring satellite using magnetic actuation

The design of sun-pointing safe controller is an important part of spacecraft attitude determination and control system. In this work, a new spin stabilization algorithm using only magnetic torquers is proposed. This algorithm has been developed for the atmospheric environment monitoring satellite, which completes the missions of fixed axis rotation and tracking the sun orientation. Firstly, a Lyapunov function, combining the angular momentum error and angular velocity, is formulated and a new sun-pointing attitude control scheme is derived. Then, it is proved that the magnetic control law is asymptotically stable in the absence of disturbance torques. The proposed method is compared with a state-of-the-art fault-tolerant magnetic spin stabilizing controller design method by numerical simulations. Simulation results show that the proposed method has better performance than the state-of-the-art technique. Finally, the applicability and effectiveness of the proposed control method are demonstrated by the hardware-in-the-loop simulation of the satellite.

A Linear Time-Varying Inequality Approach for Prescribed Time Stability and Stabilization.

This article studies the problem of finite-time, fixed-time, and prescribed-time stability analysis and stabilization. First, a linear time-varying (LTV) inequality-based approach is introduced for prescribed-time stability analysis. Then, it is shown that the existing nonlinear Lyapunov inequalities-based finite- and fixed-time stability criteria can be recast into the unified framework of the LTV inequality-based approach for prescribed-time stability. Finally, the unified LTV inequality-based approach is used to solve the global prescribed-time stabilization problem of the attitude control system of a rigid spacecraft with disturbance, and a bounded nonlinear time-varying controller is proposed via back stepping. Numerical simulations are presented to show the effectiveness of the proposed methods.

Advanced fault detection and diagnosis in spacecraft attitude control systems: Current state and challenges

A review of advanced fault detection and diagnosis (FDD) techniques in attitude control systems (ACSs) of spacecraft is presented. In the first part of the paper, several types of ACS failure scenarios with their practical solutions are presented. Next, the existing approaches to FDD are considered and classified based on different criteria, including applications and design techniques. The literature of this part showed that to enhance ACS operational safety, predictability of failure of an ACS and/or of its components as well as reducing the possibility of failure occurrence is imperative. In addition, fast FDD of various kinds of failures is necessary to guarantee the required reliability of an ACS. The second part of this study highlights challenges involved with different FDD approaches, emphasizing their practical applicability. Current research gaps in FDD techniques such as insensitive residual signal, process monitoring methods, accurate plant model design, easy-to-use software development, FDD tuning process, dealing with noisy sensor measurements, time taken for fault management, the sensitivity of FDD system to faults, and FDD robustness are further elaborated on. Subsequently, the state-of-the-art FDD and its future needs are reflected on. The results of this study could direct spacecraft manufacturers and ACS providers to focus on future needs and improve ground testing for enhanced operational reliability and redundancy.

Model predictive control for Takagi–Sugeno fuzzy model-based Spacecraft combined energy and attitude control system

A Combined Energy and Attitude Control System (CEACS) is a dual system in which flywheels are used as energy storage and attitude control devices. This work is a progress on CEACS for small satellites to improve the attitude accuracy. In this maiden work, the Fuzzy–MPC controller is introduced to regulate the CEACS attitude with both linear and nonlinear initial angles, and in the presence of actuator constraints. The nonlinear attitude model is transformed into a set of linear subsystems using the Takagi–Sugeno fuzzy modeling approach. The subsystem is designed with a MPC controller and a total control action is summed up using the parallel distributed compensation approach. The numerical results have been analyzed in terms of attitude pointing accuracies, actuator constraints, and energy consumed by the actuators. A performance comparison between the Fuzzy–MPC and Fuzzy–LQR controllers has also been done. The results validate that the Fuzzy-MPC controller achieves the desired CEACS attitude pointing accuracy of 0.0010° with a zero steady-state error and keeps the control torques within the actuator constraints. On the other hand, the Fuzzy–LQR controller gives some measurable steady-state error and achieves the CEACS attitude pointing accuracy of 0.0012°. Therefore, the Fuzzy–MPC based CEACS architecture not only achieves the desired pointing accuracies but also produces ten times smaller control torques than the Fuzzy–LQR controller, which result in a lower onboard power consumption.

Stability and hidden oscillations analysis of the spacecraft attitude control system using reaction wheels

The paper is devoted to the problem of spacecraft attitude control using reaction wheels. The control system should ensure switching between less accurate to more accurate flight modes, resistance to external environmental influences, and, in some cases, the survival of the spacecraft. In these modes, the reaction wheel drives can reach their maximum performance, which introduces a saturation effect into the control loop. Its appearance can lead to self-excited attitude oscillations and significantly degrade positioning accuracy. In the paper, by the example of the DEMETER satellite, taking into account the flexibility of the appendices, attached to the spacecraft, the hidden oscillations in the PID-controlled spacecraft orientation system under the conditions of an actuator saturation were localized, and their parameters were found. The algorithms for the spacecraft attitude control were derived and a comparative study of their oscillatory attractors areas was given. To ensure asymptotic stability of the spacecraft orientation system the anti-windup correction was introduced, preventing hidden oscillations of the spacecraft attitude in the practically meaningful region of the initial conditions. Special attention is paid to the uncertainty of the satellite model parameters, which are not initially known with good precision and are varying along the satellite's orbit. For ensuring the attitude control system robustness in the face of the parametric uncertainty, in the paper the discrete-time adaptive controller with the Implicit Reference Model and anti-windup correction is proposed, and its efficiency is demonstrated by intensive simulation research.

Fixed‐time fault‐tolerance attitude tracking control for spacecraft without unwinding

In this paper, the attitude tracking control problem is investigated for rigid spacecraft subjected to external disturbance, inertia uncertainties, and actuator faults. The rotation matrix is used to model the spacecraft attitude control system which can get rid of the unwinding problem. A nonlinear observer is developed to achieve a high accuracy estimation for the lumped disturbance in fixedtime without the awareness of the boundary of disturbance. To restrain measurement noise, a tracking differentiator is used in the observer to construct signals instead of using the polluted measurement values. Based on the estimation provided by the disturbance observer, a fixed-time attitude tracking controller is proposed by backstepping technique to stabilize attitude tracking errors in fixed time regardless of initial values. The singularity problem in traditional fixed-time controllers based on signal function is eliminated with the help of the arctangent function in the proposed controller. The feature of the designed fixed-time attitude controller is that it can suppress actuator faults, measurement noises and has no unwinding problem. Theoretical analysis based on Lyapunov theory and numerical simulations are presented to illustrate the robustness and effectiveness of the proposed control strategy.

Time-Periodic Spacecraft Attitude Control with the Use of Slewing Permanent Magnets

Introduction. Electromagnetic actuators are widely used in spacecraft (SC) attitude control systems. These actuators can be modified by using slewing permanent magnets (ASPM) as sources of torque instead of electromagnets. These modified devices consume less onboard electricity for SC attitude control than the conventional ones.Problem Statement. An algorithm for attitude stabilization of a SC using ASPM was proposed in previous studies, where the pole placement technique and pulse-width modulation (PWM) were used to design the controller. However, this approach does not allow the designers to find optimal values of the required magnetic torques, which may result in frequent engagement of the stepper motors of the ASPMs and their significant energy consumption. This controller has such a drawback because its gains are selected without taking into account time-periodic properties of the Earth magnetic field.Purpose. The purpose of the study is to design the algorithm for the SC angular stabilization by the ASPMs taking into account time-periodic properties of the Earth magnetic field.Materials and Methods. The solution of the time-periodic Riccati equation was used for the controller design. Mathematical modeling and computer simulation of SC motion was applied to build the model of the plan and validate the results.Results. A time-periodic based SC attitude control algorithm has been designed. Taking into consideration the time-periodic properties of the magnetic field of Earth allow us to optimize the required magnetic control torques. This algorithm minimizes the frequency of the actuation of the ASPM sashes, and thus reduces onboard energy consumption.Conclusions. The designed algorithm increases the control efficiency of SC attitude control by using jointly the ASPMs, time-periodic linear-quadratic regulator and pulse-width modulator.

Overall fault diagnosability evaluation for dynamic systems: A quantitative–qualitative approach

The issue of overall fault diagnosability evaluation is addressed to provide a standard for system design from the fault diagnosis perspective. An overall fault diagnosability measure is first defined statistically by combining quantitative and qualitative evaluation results. On this basis, a randomized algorithm-based method is developed for estimating this quantitative–qualitative measure with a preset accuracy. Then, a tractable method for computing the lower bound of the measure is created, which provides a way to assess fault diagnosis performance without a large computational burden. Finally, a spacecraft attitude control system is used to verify the effectiveness of the proposed methods.

Fault-tolerant control for the linearized spacecraft attitude control system with Markovian switching

In this article, the fault-tolerant control is investigated for the spacecraft attitude control system described by a linearized model with Markovian switching. First, the evolution of sudden failures of the spacecraft’s actuators is described by a Markov process. Then, the mathematical model of the spacecraft attitude control system with the Markov jump characteristic fault is established. Taking the uncertainty of the system model and external interference into consideration, a fault-tolerant control scheme is proposed for the established spacecraft attitude control system with the Markov jump characteristic fault by using the sliding mode control technique. Compared with some existing sliding mode controller design methods, the proposed method requires a less total number of LMIs to be solved. The stability and reachability of the resulting closed-loop system under the presented sliding mode control scheme are proven by applying the Lyapunov stability theory. Finally, some simulation results are provided to show the effectiveness and advantages of the proposed control method for spacecraft attitude control.

Multiplicative fault concept and fault observer design for reliability study of degrading reaction wheel

The reaction wheel is a typical actuator and a crucial weak link in the spacecraft attitude control system, and much attention has been paid to its reliability problem. Due to limited samples and high cost for reaction wheel life tests, a simulation method by introducing attitude coupling dynamics and multiplicative fault concept is developed to analyze the logic of electric current as a performance indicator and verify its accuracy for reliability modeling. Furthermore, a new and intrinsic performance indicator of multiplicative fault is proposed for more application scenarios of reliability modeling and an adaptive sliding mode observer is designed for fault estimation. An illustrative example shows that the performance indicator of multiplicative fault can be used for various mission scenarios but requires certain persistent excitation, while electric current is the opposite.

Hybrid nonfragile intermediate observer-based T-S fuzzy attitude control for flexible spacecraft with input saturation

This paper investigates a hybrid nonfragile intermediate observer-based T-S fuzzy attitude control strategy subject to multi-source complex disturbances to achieve integrated attitude stabilization and vibration suppression for the flexible spacecraft. A refined T-S fuzzy model for flexible spacecraft is introduced to represent the nonlinear characteristics in large-angle attitude maneuver. Then a hybrid nonfragile observer with coexisting additive and multiplicative perturbations is designed to estimate state information and disturbance simultaneously. Consequently, based on the closed-loop system, the quadratic stability and robust H∞ performance are proved via the Lyapunov stability analysis with corresponding conditions in terms of linear matrix inequalities (LMIs). It is worth mentioning that different from the limiter directly used in much literature, input saturation is disposed as a disturbance during the proof to satisfy the stability requirements. Finally, numerical simulations of a flexible spacecraft attitude control system are performed which demonstrate the effectiveness and superiority of the proposed control strategy.

Constrained multi‐observer‐based fault‐tolerant disturbance‐rejection control for rigid spacecraft

AbstractThis article develops a multi‐observer‐based fault‐tolerant disturbance‐rejection control strategy to solve the attitude stabilization problem of spacecraft subject to multisource complex disturbances, for example, external disturbance, measurement error, actuator fault, input constraint. First, two intermediate variables are introduced for multi‐observer design, so that the synergistic estimations of attitude information, actuator fault and external disturbance are obtained simultaneously. Then, a fault‐tolerant disturbance‐rejection control strategy is proposed based on the estimations, and an augmented closed‐loop system is derived. Afterwards, Lyapunov stability analysis is performed to prove the quadratic stability and robust performance, and corresponding conditions in terms of linear matrix inequalities (LMIs) is proved, where the input constraint is satisfied as well. Finally, numerical simulations of a spacecraft attitude control system are performed which demonstrate the effectiveness and superiority of the proposed multi‐observer‐based control strategy.