Attitude Control Problem Research Articles

A Constrained Control Allocation and Tuning Scheme for Hybrid Actuators in Spacecraft Attitude Control

Agile rotational maneuvers of spacecraft requires careful execution since its actuators may not be able to produce the demanded torques, causing the state trajectories to deviate and a desired attitude would not be guaranteed. We investigate the control allocation problem for a redundant set of hybrid actuators that include reaction wheels, magnetorquers, and continuous-force thrusters. The main objective of the magnetorquers is to dump momentum from the reaction wheels, whereas the wheels are the primary actuators in attitude control, and more agile maneuvers or faster unloading of momentum can be handled by the thrusters. A modified mixed optimization scheme for control allocation is presented where the equality constraints account for satisfying the high-level (virtual) control inputs for both attitude control and momentum dumping. Variants of dynamic weights in the optimization are developed such that magnetorquers and thrusters may contribute with a relative degree of importance in the attitude control problem. The control allocation scheme is solved using quadratic programming where simulation results are shown for fast and slow rotational maneuvers together with fast and slow momentum dumping.

Nonsingular Finite-Time Convergent Control for Spacecraft Rendezvous and Docking

This paper deals with the problem of relative position control of the chaser spacecraft during rendezvous using sliding mode control, wherein the time of operation plays a critical role in the success of mission. Conventional sliding mode controller ensures only asymptotic convergence. We propose the application of a controller based on terminal sliding mode that guarantees the finite time convergence of controlled variable to achieve the mission successfully. The proposed controller may encounter a singularity for some scenarios in real applications. To achieve finite time convergent controller enabling the spacecraft for rendezvous mission while avoiding any singularities, we also propose a controller based on nonsingular terminal sliding mode control. We validated the proposed techniques using numerical simulations and found them to be satisfactory.

A Systematic Method for Constrained Attitude Control under Input Saturation

In this paper, the constrained attitude control prob-lem with a prescribed performance requirement is investigated, and a systematic method involving the synthesis of path planning, prescribed performance design, and tracking control with inherent saturation is proposed. The overall works are based on attitude rotational matrix and its equivalent vector description. In the path planning phase, both the solid constraints, referring to the forbidden region where the sensitive instrument is strictly prohibited, and the soft constraints, referring to a designable margin of safety are considered. Then a centric reference trajectory outside the soft constraints is established according to a gradient-base algorithm. To formulate the reference trajectory, a motion planning method is employed to establish the ideal angular velocity constrained by the maximum affordable control torque. In the prescribed performance design phase, the performance boundary tube is generated to avoid any potential invasion caused by the attitude tracking error. Finally, in the controller design phase, inherent input saturation is considered and a magnitude-constrained controller is proposed. When the proposed controller is exerted on the system, closed-loop system stability is achieved and the spacecraft is always kept outside the solid constraints. The effectiveness of the proposed method is verified through numerical simulations.

Generalized Relative Degree Approach to Sliding Mode Control Design for Nonminimum Phase Systems

The relative degree (RD) approach is a powerful tool for obtaining system's input-output dynamics used for output tracking controller designs of minimum phase systems. Designs based on the RD approach alone may fail due to instability of internal dynamics attributed to nonminimum phase systems. The use of generalized relative degree allows for the elimination of internal dynamics via replacing it by the unstable dynamic extension. An algorithm for generating a bounded solution of this unstable dynamic extension is proposed, allowing for a sliding mode controller (SMC) design for nonminimum phase systems. The efficacy of the proposed approach is demonstrated on a nonminimum phase rocket attitude control problem analytically and via simulations.

Performance evaluation of spherical underwater robot with attitude controller

The attitude control for Autonomous Underwater Robots (AUVs) has practical value and is a challenging task. To bridge this research gap, a new attitude regulator based on the counterweight mechanism is proposed to perceive and regulate the attitude of the Spherical Underwater Robot (SUR). Firstly, the SUR's mechanical structure and dynamic model were described, and the center of gravity adjustment structure was designed. Subsequently, the attitude controller for the SUR was developed, which divided the attitude control problem into roll angle control and pitch angle control. Furthermore, the Back-stepping Sliding Mode Control (BSMC) method is implemented considering the uncertainties and nonlinearity of the SUR model. Then motion experiments, including “I” motion, “L” motion, and “U” motion, were evaluated to verify the effectiveness, robustness and feasibility of the developed controller in the real environment. Finally, the experimental results demonstrated that the attitude regulator had extremely superior performance in various motions, which laid a certain reference value for the self-attitude adjustment of AUV.

Event-Triggered Sliding Mode Control for Spacecraft Reorientation With Multiple Attitude Constraints

This paper addresses the event-triggered attitude control problem for spacecraft anti-unwinding reorientation with multiple attitude constraints in the presence of external disturbance. Based on a designed novel potential function(PF), a new sliding mode controller is proposed to guarantee the completeness of anti-unwinding reorientation with multiple attitude constraints and external disturbance. Different from existing continuous attitude reorientation controller, the static and dynamic event-triggered mechanisms, related with the sliding mode variable and disturbance bound, are then constructed. With the designed event-triggered sliding mode control schemes, the attitude system asymptotic stability, the satisfaction of attitude constraints with anti-unwinding action and free of Zeno phenomenon despite on external disturbance are proved theoretically. Numerical simulations results confirm that the proposed methods can significantly reduce resource usage while guaranteeing the desired performance.

Q-learning–based practical disturbance compensation control for hypersonic flight vehicle

Aiming at the attitude control problem of hypersonic flight vehicle, a compound control strategy based on the disturbance compensation technique and Q-learning optimization is proposed. Firstly, a three-channel independent control scheme based on the super-twisting extended state observer (STESO) is proposed such that coupling among channels, uncertainties, and external disturbances can be estimated and compensated in real time. Secondly, the Q-learning mechanism is introduced to optimize the control parameters while keeping the control structure unchanged. Lastly, the convergence of the STESO is analyzed by the Lyapunov theory, and some numerical simulation results are carried out to verify the effectiveness of the proposed strategy. Compared with the traditional linear active disturbance rejection control, the proposed method can avoid a lot of manual parameter tuning process and also has better performance.

Based on Backpropagation Neural Network and Adaptive Linear Active Disturbance Rejection Control for Attitude of a Quadrotor Carrying a Load

A control method combining Backpropagation (BP) neural network and Adaptive Linear Active Disturbance Rejection Control (ALADRC) is proposed for the attitude control problem of quadrotor aircraft. The proposed controller can observe and compensate the total disturbance in the working process of the quadrotor system. At the same time, it has a good ability to suppress the disturbance of the quadrotor load mass change. In addition, adaptive control and BP neural network are used to adjust the controller parameters in real time to solve the problem of difficult parameter tuning. Finally, the stability of the system is proved based on Lyapunov theory. The simulation results show that the quadrotor system can still track the altitude and attitude angle commands stably in the presence of disturbances, and has strong adaptability to load mass changes, so that the quadrotor can still complete the given tasks in the presence of multi-source disturbances.

Dynamic Event-Triggered Antidisturbance Control for Flexible Spacecraft Systems

This study develops a dynamic event-triggered anti-disturbance (DETAD) controller to solve attitude control problem for flexible spacecraft systems with multiple disturbances. The disturbances involve two aspects: one belongs to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_{2}$</tex-math></inline-formula> space, and the other is described by an exogenous nonlinear system. Two sets of Takagi–Sugeno (T–S) fuzzy models are employed to model the flexible spacecraft systems and an exogenous nonlinear system, respectively. Moreover, a flexible vibration observer (FVO) is introduced to estimate the flexible modes. And a fuzzy disturbance observer (FDO) is designed to estimate the T–S fuzzy modeling disturbance in the case of the unmeasurable premise variables. By utilizing the estimations of two observers, a DETAD controller is constructed, where a dynamic event-triggered mechanism is implemented to reduce communication transmission. Additionally, new sufficient conditions for the closed-loop system to be asymptotically stable with strict dissipative performance are formed using linear matrix inequality techniques. Simulations are also provided to verify the advantages of the proposed scheme for flexible spacecraft systems subject to different types of disturbances.

Intelligent Event-Based Fuzzy Dynamic Positioning Control of Nonlinear Unmanned Marine Vehicles Under DoS Attack.

This article addresses the dynamic positioning control problem of a nonlinear unmanned marine vehicle (UMV) system subject to network communication constraints and deny-of-service (DoS) attack, where the dynamics of UMV are described by a Takagi-Sugeno (T-S) fuzzy system (TSFS). In order to save limited communication resource, a new intelligent event-triggering mechanism is proposed, in which the event triggering threshold is optimized by a Q -learning algorithm. Then, a switched system approach is proposed to deal with the aperiodic DoS attack occurring in the communication channels. With a proper piecewise Lyapunov function, some sufficient conditions for global exponential stability (GES) of the closed-loop nonlinear UMV system are derived, and the corresponding observer and controller gains are designed via solving a set of matrix inequalities. A benchmark nonlinear UMV system is adopted as an example in simulation, and the simulation results validate the effectiveness of the proposed control method.

Backstepping-Based Steering Control for Spacecraft Attitude Control Using Two-Skewed Control Moment Gyroscopes

Numerous control methods that use two reaction wheels have been proposed for the underactuated control problem. However, few studies have applied two single-gimbal control moment gyroscopes (SGCMGs) to the three-axis attitude control problem. In this study, under the assumption that the total initial angular momentum is zero, a steering control law for the three-axis attitude maneuvers of a spacecraft with an array of two-skewed SGCMGs is designed using the backstepping technique without setting a constraint on the range of gimbal angles. The spacecraft attitude is expressed in terms of the parameters, which are suitable for the underactuated attitude control problem. The control gains are appropriately chosen to guarantee controller stability. The proposed steering control law is validated through numerical simulations. The results show that the proposed steering control law can achieve a shorter settling time than that obtained from a control law with a constraint on the range of gimbal angles.

Linear Quadratic Regulator Weighting Matrices for Output Covariance Assignment in Nonlinear Systems

A time-varying output covariance assignment problem in the presence of a stochastic disturbance is solved using finite-horizon optimal control formulation. It is shown that an assignment of time-varying output error covariance is possible in the presence of model error by utilizing a time-varying linear quadratic regulator controller with a class of output and control weighting sequences. This paper develops a systematic algorithm to calculate the sequence of such time-varying output weights that are further shown to be the Lagrange multipliers associated with the covariance constraints. A short horizon attitude control problem with stringent covariance constraints and a more nonlinear example concerning a low-thrust interplanetary maneuver are solved to demonstrate the utility of the proposed approach. Numerical results offer a degree of optimism about the broad applicability of the time-varying covariance assignment approach to solve guidance and control problems associated with nonlinear dynamic systems.

Saturated-command-deviation based finite-time adaptive control for dynamic positioning of USV with prescribed performance

This paper investigates the finite-time adaptive dynamic positioning (DP) control problem of an unmanned surface vehicle (USV) with prescribed performance subject to time-varying disturbances, unknown model parameters and input saturation. First, the error transformation is performed to provide a framework for the design of model-free prescribed performance DP controller, which eliminates the need for accurate prior information of the model and external disturbances. Then, a saturated-command-deviation based compensated law is proposed by incorporating the fuzzy supervisory approach to account for the excess control efforts resulted by input saturation. Subsequently, the fuzzy logic systems (FLS) integrated with minimum learning parameters technique are employed to approximate the model-based and high-order terms, such that the explosion of computational complexity is removed and requirements for accurate modeling are eliminated. Meanwhile, to suppress the negative effects induced by time-varying disturbances and unknown approximation errors, the adaptive technique is adopted to estimate the upper boundary of compounded disturbances online. Finally, by incorporating the softening sign signal and piecewise function into recursive backstepping procedure, a DP controller is developed to avoid potential singularity and achieve finite time convergence. Theoretical analysis and simulation results successfully illustrate the effectiveness of the proposed scheme.

Trajectory Tracking of UAVs Using Sigmoid Tracking Differentiator and Variable Gain Finite-Time Extended State Observer

The problem of quadrotor attitude and position control is considered in the presence of generally lumped disturbances: external disturbances and model uncertainty. The improved active disturbance rejection controller (ADRC) for quadrotor trajectory tracking is proposed for compensating the lumped disturbances. Firstly, the improved sigmoid tracking differentiator (ISTD), combining improved Sigmoid function and sliding mode terminal attractor is proposed, which can accelerate the global convergence rate and effectively reduce the chattering. Secondly, a novel variable gain finite-time extended state observer (VGFESO) approach is proposed to effectively estimate the lumped disturbances, while the observation errors are convergent to zero in finite time. Then, a super-twisting sliding model controller (STWSMC) is utilized for tracking control of the desired position and attitude. Finally, the convergence of VGFESO and the closed-loop stability of the control system are proved. The results show that the convergence time of the proposed control scheme is the shortest, and the integral absolute error of improved ADRC is reduced from 2.64 to 0.91. The anti-disturbance capability of the proposed controller is fully illustrated when compared with ADRC and robust adaptive nonsingular fast terminal sliding-mode controller (RANFTSMC).

Composite adaptive attitude control for combined spacecraft with inertia uncertainties

This paper examines the attitude control problem of the combined spacecraft subject to inertia uncertainties. A composite adaptive finite-time control scheme with guaranteed parameter convergence is proposed to address this challenging problem, in the absence of persistent excitation. As a stepping stone, the attitude dynamics of the combined spacecraft is first established with explicit consideration of the center-of-mass variation and thruster reconfiguration. Then, a composite adaptive finite-time controller is developed based on a constructive time-varying sliding manifold, and in particular, the concurrent learning technique is used in conjunction with the dynamic regressor extension and mixing procedure to achieve parameter convergence under finite excitation that is strictly weaker than the persistent excitation. Lyapunov stability analysis shows that the derived adaptive controller can simultaneously guarantee finite-time convergence of the attitude tracking and parameter estimation errors; moreover, its robustness against inertia variations and external disturbances is also analyzed. Finally, a set of numerical simulations under ideal and practical scenarios are performed to validate the effectiveness and outperformance of the proposed method.

Prescribed‐time stabilisation control of differential driven automated guided vehicle

AbstractThe position control problem of differential‐driven automated guided vehicles (AGVs) based on the prescribed‐time control method is studied. First, an innovative orientation error function is proposed by an auxiliary arcsine function about the orientation angle. Thus, the problem of position control of AGV is transformed into the stabilisation control of the kinematic system. Second, by introducing a reserved time parameter and a smooth switching function, a novel time‐varying scaling function is proposed. This novel scaling function avoids the risk of infinite gain in the conventional prescribed‐time control method while ensuring the smoothness of control laws. Then, an improved velocity constraint function is proposed using the Gaussian function. Compared with the existing constraint function, the proposed method not only has more smoothness but also solves the balance point errors caused by the large AGV orientation errors. The presented method ensures that the AGV reaches the target position in a prescribed time. Hence, the upper bound of the AGV system state can be determined by adjusting parameters. Matlab simulation results show that the proposed controller can effectively make the AGV system state satisfy the prescribed bound.

Fast inner-loop control of air-breathing hypersonic vehicles

This paper investigates the inner-loop attitude and velocity control problem for air-breathing hypersonic vehicles subject to practically constrained actuators. Traditional nonlinear dynamic inverse (NDI) is enhanced by an intelligent control allocation (ICA) to realise the low-complexity attitude decoupling. The ICA addresses various characteristics of aerodynamic control surfaces while providing an efficient detecting mechanism for allocation errors. Within the ICA-NDI frame, a finite-time disturbance observer-based terminal sliding mode (FTDO-based TSM) attitude controller regulates Euler angles in the fast manner. This attitude controller employs an improved integral sliding surface containing necessary information from both ICA detection and FTDO estimation, which, therefore, is capable of accommodating constrained control surfaces and rejecting mismatched disturbances. Meanwhile, an adaptive governor adjusts the velocity reference according to the current saturation level of the scramjet fuel-to-air equivalency ratio. The governor is further integrated to a baseline adaptive velocity controller to synthetically handle scramjet input saturations and uncertain factors.

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.

Lyapunov-Based Nonlinear Model Predictive Control for Attitude Trajectory Tracking of Unmanned Aerial Vehicles

This paper presents a new Lyapunov-based nonlinear model predictive controller (LNMPC) for the attitude control problem of unmanned aerial vehicles (UAVs), which is essential for their functioning operation. The controller is designed based on a quadratic cost function integrating UAV dynamics and system constraints. An additional contraction constraint is then introduced to ensure closed-loop system stability. That constraint is fulfilled via a Lyapunov function derived from a sliding mode controller (SMC). The feasibility and stability of the LNMPC are finally proved. Simulation and comparison results show that the proposed controller guarantees the system stability and outperforms other state-of-the-art nonlinear controllers such as the backstepping controller (BSC) and SMC. In addition, the proposed controller can be integrated into an existing UAV model in the Gazebo simulator to perform software-in-the-loop tests. The results show that the LNMPC is better than the built-in PID controller of the UAV, which confirms the validity and applicability of our proposed approach.

Fractional‐order sliding mode attitude coordinated control for spacecraft formation flying with unreliable wireless communication

This paper investigates the coordinated attitude control problem with fractional order sliding mode control theory for spacecraft formation flying by considering of unknown disturbance, inertia uncertainty, partial loss of actuators, and communication delay. Two types of fractional order sliding mode control laws are proposed to solve the considered design problem. The first one is based on the Chebyshev neural network technique, and the second one is involved with the integral-type and super-twisting sliding mode control methods. Compared to traditional sliding mode control methods, the developed fractional order sliding mode control strategies can achieve a faster convergence speed. Simulation results based on a group of three spacecrafts are presented to demonstrate the performance of the proposed coordinated attitude control approaches.