Time-varying Reference Attitude Research Articles

Robust output feedback attitude tracking control for rigid-flexible coupling spacecraft

This paper investigates the robust attitude tracking control problem for a rigid-flexible coupling spacecraft. First, the dynamic model for a rigid-flexible coupling spacecraft is established based on the first-order approximation method to fully reveal the coupling effect between rigid movement and flexible displacement when the spacecraft is in rapid maneuver. In the condition that flexible vibration measurements are not available, an robust output feedback controller which is independent of model is presented using Lyapunov method with considering state-independent disturbances. To resolve the chattering problem caused by the discontinuous sign function, a modified continuous output feedback controller is proposed by introducing functions with continuous property. Rigorous proof is achieved showing that the proposed control law ensures asymptotic stability and guarantees the attitude of a rigid-flexible spacecraft to track a time-varying reference attitude based on angle and angular velocity measurements only. Finally, simulations are carried out to verify the simplicity and effectiveness of the proposed control scheme.

Bounded finite-time attitude tracking control for rigid spacecraft via output feedback

This paper investigates a velocity-free finite-time attitude control scheme for a rigid spacecraft with actuator saturation and external disturbances. Initially, a finite-time observer is designed to compensate the unknown angular velocity information. With the estimated values, a finite-time controller is further developed under which the time-varying reference attitude trajectory can be tracked precisely. Moreover, input saturation problem is solved by adaptive method. Rigorous Lyapunov-based analysis shows that the states of the closed-loop system converge to a small neighborhood of the origin in finite time. Finally, the dynamic performance of attitude control system is presented by numerical simulation examples and the superiority of the finite-time control scheme is verified.

Distributed finite-time velocity-free attitude coordination control for spacecraft formations

In this paper, the finite-time velocity-free attitude coordination control for spacecraft formation flying under an undirected communication graph is addressed. A finite-time observer is introduced to obtain an accurate estimation of unmeasurable angular velocity and a decentralized finite-time observer is employed to estimate the angular acceleration of the virtual leader. With the application of the finite-time observer, the decentralized finite-time observer, and the homogeneous method, a continuous distributed finite-time attitude coordination control law is designed for a group of spacecraft without requiring angular velocity measurements. A rigorous proof shows that semi-global finite-time stability of the overall closed-loop system can be achieved and the proposed velocity-free control law guarantees a group of spacecraft to simultaneously track a common time-varying reference attitude in finite time even when the reference attitude is available only to a subset of the group members. The performance of the control scheme derived here is illustrated through numerical simulations.

Quaternion-based finite-time control for attitude tracking of the spacecraft without unwinding

This paper investigates two finite-time controllers for the attitude tracking control of the spacecraft based on the quaternion by terminal sliding mode control. Because quaternion is unable to represent the set of attitudes both globally and uniquely, it can result in unwinding. Unwinding makes a spacecraft perform an unnecessary large-angle maneuver when a small-angle maneuver in the opposite rotational direction is sufficient to achieve the objective. The first controller converges to the equilibrium without singularity in finite time, while the second one converges to the region near the equilibrium without singularity, chattering and unwinding in finite time. Saturation function is introduced to the first controller to eliminate singularity, while a novel fast terminal sliding mode control is introduced to the second controller to eliminate singularity and unwinding. Theoretical analysis shows that the controllers can make the spacecraft follow a time-varying reference attitude signal in finite time and guarantee the stability of the overall closed-loop system. Numerical simulations also demonstrate the effectiveness of the proposed control schemes.

Three-Axis Attitude Control Using Redundant Reaction Wheels with Continuous Momentum Dumping

A description of an attitude control system for a three-axis stabilized spacecraft is presented. A globally stabilizing nonlinear feedback control law is derived that enables tracking of an arbitrary time-varying reference attitude. This new control incorporates integral feedback while avoiding any quadratic rate feedback components. A redundant cluster of four or more reaction wheels is used to control the spacecraft attitude, and three magnetic torque rods are used for purposes of continuous autonomous momentum dumping. The momentum dumping strategy can employ general torque rod orientations, and it is developed to take advantage of a redundant set of reaction wheels.

Decentralized robust attitude tracking control for spacecraft networks under unknown inertia matrices

This article investigates the quaternion-based attitude tracking problem for spacecraft networks, where the interaction topology among spacecraft switches periodically and inertia matrices are totally unknown. The tracking error dynamics is modeled. A class of robust attitude coordination controller without introducing the information about external disturbances is proposed. Using the Lyapunov method and graph theory, it is proved that the controller can guarantee a group of spacecraft to track the time-varying reference attitude. Further, the tracking error can be adjusted by designers to satisfy different requirements of control accuracy. Finally, simulation results are presented to illustrate that the designed control law is successful in achieving high tracking performance, even in the presence of unknown external disturbance torque, unknown inertia matrices and switching interaction topology among spacecraft.

Terminal Sliding Mode Control for Attitude Tracking of Spacecraft Based on Rotation Matrix

Two finite-time controllers without unwinding for the attitude tracking control of the spacecraft are investigated based on the rotation matrix, in which a novel modified nonsingular fast terminal sliding manifold is developed to keep tr(R~)≠-1. The first terminal sliding mode controller can compensate external disturbances with known bounds, while the second one can compensate external disturbances with unknown bounds by using an adaptive control method. Since the first terminal sliding mode controller is continuous, it is able to avoid chattering phenomenon. Theoretical analysis shows that both the two controllers can make spacecraft follow a time-varying reference attitude signal in finite time. Numerical simulations also demonstrate that the proposed control schemes are effective.

Finite‐time distributed cooperative attitude control for multiple spacecraft with actuator saturation

In this study, the distributed cooperative attitude tracking controller based on fast terminal sliding mode and Chebyshev neural network (CNN) is proposed for multiple spacecraft formation flying (SFF) system in the presence of external disturbance. Firstly, a new modified fast terminal sliding mode manifold, which has faster convergence rate than the existing terminal sliding modes, is proposed. Then, based on the proposed terminal sliding mode manifold, the distributed cooperative attitude tracking controller is designed for the SFF system, where the time varying reference attitude can be only accessed to a subset of the group member. To guarantee that the output of CNN used in the controller is bounded by the corresponding bound of the approximated unknown function, a modified adaptive law is proposed to revise the sliding mode manifold, meanwhile, the finite-time stability of SFF system can be also guaranteed. Finally, numerical simulations are presented to verify the validity and robustness of the proposed control algorithm.

Adaptive finite-time backstepping control for attitude tracking of spacecraft based on rotation matrix

This paper investigates two finite-time controllers for attitude control of spacecraft based on rotation matrix by an adaptive backstepping method. Rotation matrix can overcome the drawbacks of unwinding which makes a spacecraft perform a large-angle maneuver when a small-angle maneuver in the opposite rotational direction is sufficient to achieve the objective. With the use of adaptive control, the first robust finite-time controller is continuous without a chattering phenomenon. The second robust finite-time controller can compensate external disturbances with unknown bounds. Theoretical analysis shows that both controllers can make a spacecraft following a time-varying reference attitude signal in finite time and guarantee the stability of the overall closed-loop system. Numerical simulations are presented to demonstrate the effectiveness of the proposed control schemes.

Distributed Attitude Synchronization and Tracking Control for Multiple Rigid Bodies

This paper investigates the distributed attitude synchronization and tracking control for multiple rigid bodies when a common time-varying reference attitude is available to only a subset of the group members. The unit quaternion is used for the attitude representation because of its globally nonsingular property. A decentralized sliding mode observer is presented to obtain an accurate estimate of the reference attitude in finite time. Two distributed attitude coordination control schemes are proposed based on the separation principle. The angular velocity measurements are required in the first control scheme while this requirement is removed in the second case. Both control schemes guarantee all rigid bodies to track the common reference attitude. One important and novel feature of this paper lies in the fact that the proposed distributed control schemes do not require all rigid bodies to have access to the common reference attitude. Simulation results of a scenario of six rigid bodies are presented to demonstrate the performance of the distributed controllers.

Finite-Time Output Feedback Attitude Tracking Control for Rigid Spacecraft

This brief investigates the finite-time output feedback attitude control of a rigid spacecraft. First, a nonlinear observer is designed. Through geometric homogeneity and Lyapunov theories, it is shown that the proposed observer can achieve the semiglobal finite-time stability. Then, a finite-time output feedback controller is proposed based on the finite-time observer. Rigorous proof shows that the proposed control law ensures semiglobal stability and guarantees the attitude of a rigid spacecraft to track a time-varying reference attitude in finite time. Simulation results are presented to illustrate the performance of the proposed controller.

Quaternion-Based Distributed Output Feedback Attitude Coordination Control for Spacecraft Formation Flying

This paper considers output feedback attitude coordination control for spacecraft formation flying using quaternion-based attitude parameterization. Using finite-time observers, reduced-order observers, and backstepping control technique, a distributed output feedback attitude coordination control scheme is proposed. Through Lyapunov approach and graph theory, it is shown that the control law guarantees a group of spacecraft simultaneously tracking a common time-varying reference attitude even when the reference attitude is available only to a subset of the members of a group. The results of the numerical simulation show that the distributed controller is successful in achieving good attitude tracking and synchronization performance without requiring angular velocity measurements and in the presence of bounded external disturbances.

Attitude Coordination Control for a Group of Spacecraft Without Velocity Measurements

This paper investigates the problem of velocity-free attitude coordination control for a group of spacecraft with attitude represented by modified Rodrigues parameters. The communication flow among neighbor spacecraft is described by an undirected connected graph. Two velocity-free attitude coordination control schemes are proposed. By employing linear reduced-order observers, robust control and Chebyshev neural networks, the first velocity-free control scheme allows a group of spacecraft to simultaneously align their attitude and track a time-varying reference attitude even in the presence of unknown mass moment of inertia matrix and external disturbances, where all spacecraft have access to the common reference attitude. The second control law guarantees a group of spacecraft to track a time-varying reference attitude without requiring velocity measurements even when the common reference attitude is available only to a subset of the group members. Furthermore, the stability of the overall closed-loop system for both control laws is guaranteed by a Lyapunov-based approach. Finally, numerical simulations are presented to demonstrate the performance of the proposed controllers.

Neural network-based distributed attitude coordination control for spacecraft formation flying with input saturation.

This brief considers the attitude coordination control problem for spacecraft formation flying when only a subset of the group members has access to the common reference attitude. A quaternion-based distributed attitude coordination control scheme is proposed with consideration of the input saturation and with the aid of the sliding-mode observer, separation principle theorem, Chebyshev neural networks, smooth projection algorithm, and robust control technique. Using graph theory and a Lyapunov-based approach, it is shown that the distributed controller can guarantee the attitude of all spacecraft to converge to a common time-varying reference attitude when the reference attitude is available only to a portion of the group of spacecraft. Numerical simulations are presented to demonstrate the performance of the proposed distributed controller.

Robust Attitude Coordination Control for Spacecraft Formation Flying Under Actuator Failures

This paper examines attitude coordination control for spacecraft formation flying. A class of distributed adaptive fault-tolerant attitude coordination control laws is proposed. The proposed control laws do not require online identification of failures. Using the Lyapunov approach and graph theory, it is shown that the control laws guarantee a group of spacecraft that simultaneously track a common time-varying reference attitude, even when the reference attitude is available only to a subset of the members of a group. Finally, numerical simulation is presented to show that the distributed controller is successful in achieving high-attitude tracking and synchronization performance, even in the presence of an unknown mass moment of inertia matrix, bounded external disturbances, actuator failures, and control saturation limits.

Distributed adaptive attitude synchronization of multiple spacecraft

This paper addresses the distributed attitude synchronization problem of multiple spacecraft with unknown inertia matrices. Two distributed adaptive controllers are proposed for the cases with and without a virtual leader to which a time-varying reference attitude is assigned. The first controller achieves attitude synchronization for a group of spacecraft with a leaderless communication topology having a directed spanning tree. The second controller guarantees that all spacecraft track the reference attitude if the virtual leader has a directed path to all other spacecraft. Simulation examples are presented to illustrate the effectiveness of the results.

Nonlinear Adaptive Control for Small-Scale Helicopter

In this study, a nonlinear adaptive control system for a single-rotor type small helicopter is designed. First, a small autopilot device, which can be applied any single-rotor type helicopters, is developed based on FPGA (Field Programmable Gate Array) board. In the case of small helicopter, the payload limitation is so tight. Therefore, we can only use small and light weight sensors and computer for the control. All the sensors we use for the autopilot device are light enough to be mounted on any small helicopters. the total weight of the autopilot device with box is about 300 g. Next, a nonlinear adaptive attitude controller for small helicopter is designed by using adaptive backstepping method. It is guaranteed to make the attitude of the helicopter follows arbitrary time varying reference attitude, even when the helicopter model has the parameter uncertainties, such as inertia moment or aerodynamic uncertainties. Finally, the effectiveness of the autopilot device and the adaptive attitude controller are verified by simulation with parameter uncertainties, and the flight experiment using heterogeneous small helicopters.

Distributed Cooperative Attitude Synchronization and Tracking for Multiple Rigid Bodies

In this paper, distributed cooperative attitude synchronization and tracking problems are considered for multiple rigid bodies with attitudes represented by modified rodriguez parameters. Two distributed control laws are proposed and analyzed. The first control law applies a passivity approach for distributed attitude synchronization. The control law guarantees attitude synchronization without the requirement for absolute angular velocity measurements and relative angular velocity measurements between neighboring rigid bodies. The second control law incorporates a time-varying reference attitude, where the reference attitude is allowed to be available to only a subset of the group members under general directed information exchange. The control law guarantees that all rigid bodies track the time-varying reference attitude as long as a virtual leader whose attitude is the time-varying reference attitude has a directed path to all other rigid bodies in the group. Simulation results are presented to demonstrate the effectiveness of the two control laws.

1A2-D07 小型ヘリコプタ搭載用オートパイロットシステムの構築

In this paper, we propose an autopilot system which can be applied any single rotor helicopters. First, we construct the hardware of the autopilot system based on FPGA (Field Programmable Gate Array). In the case of small helicopter, payload limitation of them is tight. Therefore, we have to use only light weight sensors and computer for the control. All sensors we use are light weight, then the total weight of autopilot device with box is about 300g. Next, nonlinear adaptive attitude controller is designed by using adaptive backstepping method. We guarantee that the attitude of helicopter can follow any time varying reference attitude even if the helicopter has unknown model parameters, such as inertia moment or aerodynamic uncertainties. Finally, the effectiveness of the autopilot system is verified by flight experiments of multiple helicopters