Spacecraft Attitude Control Research Articles

Preassigned finite-time attitude control for spacecraft based on time-varying barrier Lyapunov functions

The problem of preassigned finite-time control is addressed in this paper for attitude tracking of the rigid spacecraft with parameter uncertainty and external disturbance. First, the attitude tracking error system of the rigid spacecraft is constructed. Then, a kind of preassigned finite-time functions is used to impose a priori desired performance index on the state of the constructed error system. By applying the backstepping technique, a preassigned finite-time controller is proposed to stabilize the attitude tracking error system via employing a time-varying barrier Lyapunov function. In addition, an extended state observer is introduced to estimate the lumped disturbance in the rigid spacecraft system. It is proven that the practically preassigned finite-time stability of the resultant closed-loop system can be guaranteed by the proposed controller despite the presence of parameter uncertainty and external disturbance. Finally, simulation results are presented to demonstrate the effectiveness of the developed controller design method.

Stable Control of Nutation and Precession for the Radial Four-Degree-of-Freedom AMB-Rotor System Considering Strong Gyroscopic Effects

The stable control of the active magnetic bearing rotor (AMB-rotor) system is the key technology for a magnetically suspended control moment gyroscope, which is used in the spacecraft attitude control system. The nutation and precession instability caused by strong gyroscopic effects is the principal issue of the AMB-rotor system. In order to solve the gyroscopic effects problem, in this article, a state-space model of the radial four-degree-of-freedom AMB-rotor system is established, and the strong gyroscopic effects term varying with the rotor speed is regarded as a bounded perturbation. The regional pole assignment method of an uncertain system is used to design a robust controller to maintain the system stability over the full rotor speed range. However, the controller designed by the regional pole assignment method does not consider the influence of closed-loop stiffness of the magnetic bearing, which will lead to the start-up oscillation and structural mode self-excited oscillation problems. Therefore, on the basis of the regional pole assignment, the system stiffness is further constrained and a robust controller is solved. Experiments show that the designed controller can not only deal with the start-up oscillation and the structural modal vibration problems, but also can achieve the stable control of the nutation and precession.

Adaptive fuzzy Jacobian control of spacecraft combined attitude and Sun tracking system

PurposeThe paper aims to address the combined attitude control and Sun tracking problem in a flexible spacecraft in the presence of external and internal disturbances. The attitude stabilization of a flexible satellite is generally a challenging control problem, because of the facts that satellite kinematic and dynamic equations are inherently nonlinear, the rigid–flexible coupling dynamical effect, as well as the uncertainty that arises from the effect of actuator anomalies.Design/methodology/approachTo deal with these issues in the combined attitude and Sun tracking system, a novel control scheme is proposed based on the adaptive fuzzy Jacobian approach. The augmented spacecraft model is then analyzed and the Lyapunov-based backstepping method is applied to develop a nonlinear three-axis attitude pointing control law and the adaptation law.FindingsNumerical results show the effectiveness of the proposed adaptive control scheme in simultaneously tracking the desired attitude and the Sun.Practical implicationsReaction wheels are commonly used in many spacecraft systems for the three-axis attitude control by delivering precise torques. If a reaction wheel suffers from an irreversible mechanical breakdown, then it is likely going to interrupt the mission, or even leading to a catastrophic loss. The pitch-axis mounted solar array drive assemblies (SADAs) can be exploited to anticipate such situation to generate a differential torque. As the solar panels are rotated by the SADAs to be orientated relative to the Sun, the pitch-axis wheel control torque demand can be compensated by the differential torque.Originality/valueThe proposed Jacobian control scheme is inspired by the knowledge of Jacobian matrix in the trajectory tracking of robotic manipulators.

Modeling and validation of reaction wheel micro-vibrations considering imbalances and bearing disturbances

Reaction wheels are one of the main actuators for spacecraft attitude control. However, they generate undesired micro-vibrations that affect the attitude control performance. Some space missions that have high-resolution instruments such as telescopes and cameras require high-accuracy attitude control. In such missions, these micro-vibrations cause stability problems, which negatively affect the performance of these instruments. This paper introduces a nonlinear dynamics model for these micro-vibrations in five degrees of freedom. The main advantage of the proposed model is that it analytically considers various disturbance sources. This allows the reaction wheel designers to predict the micro-vibration behavior of the reaction wheel even before the manufacturing of the reaction wheel, i.e., in the design stage. The model considers static and dynamic imbalances of the wheel and the bearing disturbances that come from the waviness in all bearing parts (inner/outer races and balls). Experiments are conducted to validate the effectiveness of the nonlinear model.

Assessing debris strikes in spacecraft telemetry: Development and comparison of various techniques

Debris strikes on operational spacecraft are becoming more common due to increasing numbers of space objects. Sample return missions indicate hundreds of minor strikes, but rigorous analysis is often only performed when a strike causes an anomaly in spacecraft performance. Developing techniques to identify and assess minor strikes that do not immediately cause anomalous behavior can help to validate models for debris populations, perform risk assessments, and aid in the attribution of future anomalies. This study introduces debris strikes to a spacecraft dynamics simulation and assesses the effect on spacecraft telemetry. Various signal processing and change detection techniques are used to identify strikes in noisy telemetry and estimate strike parameters. Matched filter wavelets are developed to identify the effects on state telemetry, where errors are autonomously corrected by the spacecraft attitude control system. A bank of matched filters is used to estimate the parameters of the strike based on a priori knowledge of the spacecraft's response characteristics. A sequential probability ratio test is used to highlight abrupt changes in the spacecraft's angular momentum. Monte-Carlo analyses are conducted to characterize the performance of these algorithms. The results of the various techniques are compared in terms of correctly identifying the debris strikes and accurately estimating the strike parameters. Developing the capability to catalog and characterize minor debris strikes allows any spacecraft to be used as an in situ debris sensor.

Chattering-free Fault-tolerant Attitude Control with Fast Fixed-time Convergence for Flexible Spacecraft

This paper is mainly dedicated to the challenging issue of fixed-time attitude control for a flexible spacecraft in the presence of actuator faults, external disturbances and coupling effect of flexible modes. The attitude controller is developed by employing a fixed-time nonsingular terminal sliding mode under which the convergence time is bounded and independent of the initial states. This robust attitude controller is able to provide superior properties such as fast fixed-time attitude manoeuvring with high pointing accuracy, singularity avoidance and chattering free. More specifically, a new reaching law is employed to provide convergence rate improvement as well as chattering alleviating simultaneously. The actuator fault problem is also considered and the attitude control is achieved even when the actuators experience severe faults. The proposed controller ensures that the closed-loop attitude system is stable in the sense of fixed-time stability concept. Furthermore, since the upper bound of external disturbances and flexible vibrations acting on the spacecraft is not available, an adaptation mechanism is presented. Numerical simulations demonstrate that the proposed controller is able to successfully accomplish attitude control with high attitude pointing accuracy and stability in spite of the actuator faults, flexible structures vibrations and external disturbances.

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.

Spacecraft Attitude Control: A Consideration of Thrust Uncertainty

To account for torque disturbances and control trajectory error, a model of a spacecraft attitude system is presented that replicates uncertainty in the class of continuous low-thrust systems. The generated uncertainty from each thruster is modeled as a Gaussian white noise process, multiplicative in control. An optimal stochastic control law is derived for precision pointing and three-axis stabilization. To derive the optimal control, a Hamilton–Jacobi–Bellman equation is formulated, and a power series-based method is employed to approximate the optimal control. The derived nonlinear control minimizes the objective function of the Lagrange problem in an infinite horizon setting. Stability and existence conditions of control are provided. The nonlinear stochastic optimal controller is compared to its deterministic counterpart for a 6U CubeSat model.

An overview of prescribed performance control and its application to spacecraft attitude system

High-quality control method is of great importance for the attitude determination and maneuvering of spacecraft in the on-orbit servicing technology. Prescribed performance control methodology, as a potential way, has gained considerable attention due to its quantitative description for the transient and steady-state control performance in recent years. Thus, this article constructs a survey for the prescribed performance control methodology along with the detailed analysis of the attitude control methods in the existing reported works. Then, the basic structure of prescribed performance control methodology is discussed in theory, and application to the attitude control of postcapture spacecraft works as an example to further explain the procedure of prescribed performance control methodology. Finally, with consideration of some vital aerospace applications, potential open issues of the prescribed performance control methodology are analyzed.

Event-triggered adaptive attitude control for flexible spacecraft with actuator nonlinearity

This paper investigates the attitude control problem for flexible spacecraft subject to actuator deadzone under event-trigger mechanism. An event-triggered mechanism is evolved to reduce the communication resource of the sensor to controller channel, which adopts a switching threshold strategy to exclude the Zeno phenomenon fundamentally. In order to address the model nonlinear dynamics, the fuzzy logic systems is employed based on the event-triggered sensor measurements. In addition, the actuator deadzone is modeled as sector nonlinearity, which can be compensated by event-triggered adaptive scheme. It is shown that the proposed adaptive controller can reject the measurement errors induced by event-triggered scheme, the unknown model/actuator nonlinearity, and the external disturbances effectively, such that the attitude stabilization objective can be ultimately achieved. Finally, the simulation results are presented to verify the feasibility of the proposed event-triggered control law.

Disturbance Observer-Based Active Vibration Suppression and Attitude Control for Flexible Spacecraft

In this article, active vibration suppression and attitude control for flexible spacecraft under model uncertainty and external disturbance are investigated. First, an adaptive disturbance observer (ADO) and flexible vibration observer (FVO) are proposed to estimate the lumped uncertainty and flexible vibration. It is shown that the proposed ADO is nonoverestimated and the first derivative upper bound of disturbance is unknown. Then, based on the proposed observers, a novel controller is designed to suppress flexible vibration and realize attitude control. The remarkable feature of the designed algorithm is that flexible vibration is suppressed and attitude tracking is guaranteed simultaneously without intelligent materials which are used to suppress flexible vibration in the previous work. In addition, high-precision attitude control can be achieved. The rigorous proof of closed-loop system stability is presented using Lyapunov techniques. Finally, numerical simulations are given to illustrate the efficiency of the proposed algorithm.

Robust Controller Design for Stochastic Nonlinear Systems via Convex Optimization

This article presents ConVex optimization-based Stochastic steady-state Tracking Error Minimization (CV-STEM), a new state feedback control framework for a class of Itô stochastic nonlinear systems and Lagrangian systems. Its innovation lies in computing the control input by an optimal contraction metric, which greedily minimizes an upper bound of the steady-state mean squared tracking error of the system trajectories. Although the problem of minimizing the bound is nonconvex, its equivalent convex formulation is proposed utilizing SDC parameterizations of the nonlinear system equation. It is shown using stochastic incremental contraction analysis that the CV-STEM provides a sufficient guarantee for exponential boundedness of the error for all time with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bf \mathcal {L}_2}$</tex-math></inline-formula> -robustness properties. For the sake of its sampling-based implementation, we present discrete-time stochastic contraction analysis with respect to a state- and time-dependent metric along with its explicit connection to continuous-time cases. We validate the superiority of the CV-STEM to PID, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {H}_\infty$</tex-math></inline-formula> , and baseline nonlinear controllers for spacecraft attitude control and synchronization problems.

Spacecraft Attitude Control With Nonconvex Constraints: An Explicit Reference Governor Approach

This paper introduces a novel attitude controller for spacecraft subject to actuator saturation and multiple exclusion cone constraints. The proposed solution relies on a two-layer approach where the first layer prestabilizes the system dynamics whereas the second layer enforces constraint satisfaction by suitably manipulating the reference of the prestabilized system. In particular, constraint satisfaction is guaranteed by taking advantage of set invariance properties, whereas asymptotic convergence is achieved by implementing a non-conservative navigation field which is devoid of undesired stagnation points. Multiple numerical examples illustrate the good behavior of the proposed scheme.

Parametric control to quasi-linear systems based on dynamic compensator and multi-objective optimization

This paper considers a parametric approach for quasi-linear systems by using dynamic compensator and multi-objective optimization. Based on the solutions of generalized Sylvester equations, we establish the more general parametric forms of dynamic compensator and the left and right closed-loop eigenvector matrices, and give two groups of arbitrary parameters. By using the parametric approach, the closed-loop system is converted into a linear constant one with a desired eigenstructure. Meanwhile, it also proposes a novel method to realize multi-objective design and optimization. Multiple performance objectives, containing overall eigenvalue sensitivity, $H_2$ norm, $H_\infty$ norm and low compensation gain, are formulated by arbitrary parameters, then robustness and low compensation gain criteria are expressed by a comprehensive objective function which contains each performance index weighted. By utilizing degrees of freedom (DOFs) in arbitrary parameters, we can optimize the comprehensive objective function such that an optimized dynamic compensator is found to satisfy the robustness and low compensation gain criteria. Finally, an example of attitude control of combined spacecrafts is presented which proves the effectiveness and feasibility of the parametric approach.

Integrated control of attitude maneuver and vibration suppression of flexible spacecraft based on magnetically suspended control moment gyros

This paper adopts magnetically suspended control moment gyro (MSCMG) to realize the integration of attitude control and wideband micro-vibration suppression of spacecraft without adding extra hardware resources. The coupling between central rigid body and flexible attachment has been effectively retained in the controller design. First, an open-loop modal observer is constructed in advantage of the inherent physical characteristics of flexible modes, and then an adaptive backstepping controller involving flexible modal estimation, spacecraft attitude quaternion, and angular velocity is designed. Next, the band-pass filters are employed to separate the low-frequency gimbal command angular rate signal and medium–high-frequency rotor command angular rate signal, respectively, so that MSCMG can accurately track the command signal output by the integrated controller. Taking advantage of MSCMG’s ability to output high bandwidth micro-gimbal moment, the proposed method can not only meet the requirement of spacecraft rapid maneuver but also effectively suppress the broadband micro-vibration, including low-frequency flexible vibration and medium–high-frequency micro-vibration caused by spacecraft rotating parts. Numerical simulations and frequency domain analysis demonstrate the correctness and effectiveness of the proposed method.

Adaptive robust sliding mode simultaneous control of spacecraft attitude and micro-vibration based on magnetically suspended control and sensitive gyro

This paper puts forward realizing the synchronous control of spacecraft attitude and micro-vibration by taking advantage of magnetic suspension rotor deflection of magnetically suspended control and sensitive gyro. A disturbance-observer is designed to estimate the complex micro vibration which is hard to measure, and an adaptive robust sliding mode controller is designed as an integrated controller and its stability is proven by Lyapunov stability criterion. The band-pass filters are introduced to separate low frequency and high frequency control signals and takes them as input commands of gyro frame and magnetic suspension rotor, respectively. The semi-physical simulation results testify that the proposed method has good vibration suppression effect as well as improves the attitude convergence rate.

Incremental model based online heuristic dynamic programming for nonlinear adaptive tracking control with partial observability

Heuristic dynamic programming is a class of reinforcement learning, which has been introduced to aerospace engineering to solve nonlinear, optimal adaptive control problems. However, it requires an off-line learning stage to train a global system model to represent the system dynamics. This paper uses an incremental model in heuristic dynamic programming to improve the online learning ability, which is incremental model based heuristic dynamic programming. The trait of the online identification of the incremental model makes this method an option for fault-tolerant control and partially observable control problems. This study, therefore, also extends this method to deal with partial observability. The presented method has been validated on two different online tracking problems: missile fault-tolerant control with full-state measurements and also spacecraft attitude control disturbed with liquid sloshing under partially observable conditions. The results reveal that the proposed method outperforms the conventional heuristic dynamic programming method in fault-tolerant control tasks, deals with partial observability, and is robust to internal uncertainties and external disturbances.

Gyro-less angular velocity estimation and intermittent attitude control of spacecraft using coarse-sensors based on geometric analysis

Gyro-less angular velocity estimation is significant for the attitude control of spacecraft when the gyro is unavailable. The paper considered that the angular velocity remains almost constant in a short free-motion period, indicating that these endpoints of celestial body directions are on parallel planes. On this basis, we developed a novel angular velocity estimation method by optimizing these parallel planes with an iterative algorithm. Moreover, we proposed an alternative intermittent attitude control method, including a free-motion period for angular velocity calculation and a control period for attitude stabilization, respectively. Wherein, the length of the free-motion period is adjusted according to the magnitude of angular velocity to improve the calculation accuracy. Besides, we introduced a control law and analyzed the system stability using the Lyapunov method. For validation, we developed some simulation cases by constructing a semi-physical simulation platform and analyzed the effects of observation noise, the moment of inertia, and angular velocity. The simulation results show that the angular velocity estimation method has better accuracy and faster convergence than the Kalman method when considering observation noise. That is, the proposed intermittent attitude control method is feasible for the attitude stabilization.

Fixed-time control for high-precision attitude stabilization of flexible spacecraft

This is a study of adaptive constraint attitude control for a flexible spacecraft in the presence of inertia uncertainties, unknown disturbance, actuator saturation and faults. The proposed controller is designed by incorporating a Prescribed Performance Control (PPC) and fixed-time sliding mode control. First, a novel Nonsingular Fast Fixed-time Sliding Surface (NFFTSS) is introduced. Not only is the settling time independent of initial conditions, but also it is shorter than existing fixed-time attitude controls. Second, different from the conventional complex PPCs in the literature, a simple structure attitude controller is proposed to satisfy the transient and steady-state performance is proposed through a novel log-type PPC. An inherently continuous adaptive switching control is then presented in order to avoid the a priori not to require accurate information of the fault occurrence. Numerical simulations demonstrate that the proposed controller successfully accomplishes attitude control with high attitude pointing accuracy and stability.

Reliability Approach to Optimal Thruster Configuration Design for Spacecraft Attitude Control Subsystem

An optimal thruster configuration for attitude control subsystem of a spacecraft is presented in this paper. The optimal configuration is designed according to minimum number of required thrusters for satisfying desired reliability with specific redundancy level. The genetic algorithm is employed for optimization process and feasibility of the results is evaluated using algebraic and geometry methods. The main feature of the proposed configuration among feasible configuration with minimum number of required thrusters, which has held to optimal configuration, is that this configuration has maximum reliability and minimum fuel consumption. In addition to feasibility, attitude control performance of some configurations is also examined through the simulation. The results of simulation confirm that the proposed configuration has desirable performance. It is noteworthy to mention that the configuration with maximum number of required thrusters, which is a conventional configuration such that each thruster belongs to only one control channel, has less fuel consumption than optimal configuration. However, the total mass of optimal configuration is less than that of conventional configuration due to a smaller number of thrusters.