Huayi Li

Fault Reconstruction and Fault-Tolerant Control via Learning Observers in Takagi–Sugeno Fuzzy Descriptor Systems With Time Delays

This paper addresses the problems of observer-based fault reconstruction and fault-tolerant control for Takagi-Sugeno fuzzy descriptor systems subject to time delays and external disturbances. A novel fuzzy descriptor learning observer is constructed to achieve simultaneous reconstruction of system states and actuator faults. Sufficient conditions for the existence of the proposed observer are explicitly provided. Utilizing the reconstructed fault information, a reconfigurable fuzzy fault-tolerant controller based on the separation property is designed to compensate for the impact of actuator faults on system performance by stabilizing the closed-loop system. In addition, the design of the fault reconstruction observer and the fault-tolerant controller is formulated in terms of linear matrix inequalities that can be conveniently solved using convex optimization techniques. Finally, simulation results on a truck-trailer system are presented to verify the effectiveness of the proposed approaches.

Integrated design of fault reconstruction and fault-tolerant control against actuator faults using learning observers

ABSTRACT This paper addresses the problem of integrated fault reconstruction and fault-tolerant control in linear systems subject to actuator faults via learning observers (LOs). A reconfigurable fault-tolerant controller is designed based on the constructed LO to compensate for the influence of actuator faults by stabilising the closed-loop system. An integrated design of the proposed LO and the fault-tolerant controller is explored such that their performance can be simultaneously considered and their coupling problem can be effectively solved. In addition, such an integrated design is formulated in terms of linear matrix inequalities (LMIs) that can be conveniently solved in a unified framework using LMI optimisation technique. At last, simulation studies on a micro-satellite attitude control system are provided to verify the effectiveness of the proposed approach.

A star tracking algorithm suitable for star sensor

The sufficient attitude knowledge including location of recognized stars in star image can be obtained with Lost-in-Space case. In order to make use of the sufficient attitude knowledge, the star sensor may work in star tracking case. To achieve this, a star tracking algorithm is proposed in this paper. The previous location of recognized stars in star image may be used to obtain location of observed star in proper region of current star image with the star tracking algorithm. The simulations and real sky experiment results show that the star tracking algorithm proposed in this paper not only improves update rate of star sensor, but also avoids fault star pattern recognition. Finally, a star sensor featuring star tracking algorithm proposed in this paper was for on-orbit demonstration.

An autonomous star pattern recognition algorithm using bit match

A novel star pattern recognition algorithm using bit match for star sensor is presented in the paper. At first the entire celestial sphere is divided into n un-overlapped square sub-areas. The number of navigation stars in the sub-area data is saved in the first part of the sub-area data. Every bit 1 refers to a navigation star while every bit 0 not. An 18-bit binary code and an extra 0 are used to the number of successive bit 0s, and 11 are used to a bit 1. These resulted bit numbers are stored in corresponding position in the sub-area data. Let all sub-area data rearrange with the number of navigation stars in ascending order and be stored as the navigation star database. The logical AND operation is used for star pattern recognition. The simulations show that the less time for star pattern recognition and uses less memory for storing navigation star database are used with the algorithm in this paper than those with KMP (Knuth-Morris-Pratt) algorithm.

A new strategy for fault estimation in Takagi-Sugeno fuzzy systems via a fuzzy learning observer

This paper is to suggest a new strategy for fault estimation in Takagi-Sugeno (T-S) fuzzy systems. A fuzzy Learning Observer (FLO) is constructed to achieve simultaneous estimation of system states and actuator faults. The FLO is able to estimate both constant and time-varying faults accurately, and a systematic method is also proposed to select gain matrices for the FLOs. Stability and convergence of the proposed observer is proved using Lyapunov stability theory. The design of FLOs can be formulated in terms of Linear Matrix Inequalities (LMIs) that can be conveniently solved using LMI optimization technique. A single-link flexible manipulator is employed to verify the effectiveness of the proposed fault-estimating approaches.

Fault reconstruction for Takagi–Sugeno fuzzy systems via learning observers

ABSTRACT This paper addresses the problem of observer-based fault reconstruction for Takagi–Sugeno fuzzy systems. Two types of fuzzy learning observers are constructed to achieve simultaneous reconstruction of system states and actuator faults. Stability and convergence of the proposed observers are proved using Lyapunov stability theory, and necessary conditions for the existence of the observers are further discussed. The design of fuzzy learning observers can be formulated in terms of a series of linear matrix inequalities that can be conveniently solved using convex optimisation technique. A single-link flexible manipulator is employed to verify the effectiveness of the proposed fault-reconstructing approaches.

Robust learning observer-based actuator fault reconstruction for satellite attitude control systems

In this paper, robust actuator fault reconstruction for satellite attitude control systems (ACSs) in the presence of space environmental disturbances and actuator faults is investigated via a learning observer (LO). First, a nonlinear mathematical model of the satellite ACS satisfying Lipschitz constraint is established; then an LO is constructed to achieve robust reconstruction of satellite attitude angles, attitude angler velocities and actuator faults at the same time. Further, sufficient conditions for the robust stability of the LO are explicitly provided in this paper. The design problem of the proposed LO is formulated into a convex optimization problem in terms of linear matrix inequalities (LMIs) that can be directly solved using the LMI toolbox of MATLAB. At last, simulation studies on a satellite example are performed to illustrate the effectiveness and applicability of the presented LO-based fault-reconstructing strategy.

Relative Attitude Control in Satellite Formation Flying with Information Delay

In leader-follower formation flying, using the leaders rate of rotation, the follower calculates the target attitude and rate of rotation, which are necessary to relative attitude control. In the process of information collecting, computing and transmitting, time delay exists that causes information delay. To deal with it, rate and attitude estimators are presented which provide target rate and attitude real time. Then a PID control law for small satellite with reaction wheels is developed based on them. Simulation results show the approach is valid

Conditions of Reducing effect of J2 Perturbation on Formation Flying

After the relative motion coordinate frame is defined in formation flying, linear equations of relative motion described by small orbital element bias are developed with respect to it. And then the differential expressions of relative position drifts due to J2 perturbation are established. Integrating them along the orbit, the drifts without effects of true anomaly are obtained. To eliminate relative position drifts resulting from J2 perturbation, certain conditions that the initial orbital elements should meet are available with respect to circle or approximating circle orbit. Numerical simulators are employed to check the fidelity of the conclusion. Comparisons of illustrations show that the drifts obviously decrease when the orbit elements meet the conditions

Correcting Semi-Major to Reduce Effect of J2 Perturbation on Formation Flying

After the relative motion coordinate frame is defined, linear equations of relative motion described by small orbital element bias are developed with respect to it. And then the differential expressions of relative position drifts due to J2 perturbation are established. Integrating them along the orbit, the drifts without effects of true anomaly are obtained. A cost function denoting the magnitude of drifts is selected. The optimal solution to the function is the optimal correction of semi-major. The calculating formula is available. Numerical simulations are employed to check the fidelity of the approach. Comparisons of illustrations show that the approach has more advantages in reducing the relative position drifts and better shape the relative orbit