H-infinity Observer Research Articles

H-Infinity Observer for Vehicle Steering System with Uncertain Parameters and Actuator Fault

In this paper, an actuator fault diagnosis and reconfiguration problem is discussed for an uncertain vehicle steering system with external disturbances. Aiming at the factors affecting the control performance, a fault reconstruction strategy based on H-infinity observer is designed to improve the vehicle stability under complex conditions when the actuator fails. Firstly, aiming at the uncertain part caused by the road condition transformation, a mathematical model of dual input and dual output four-wheel steering system is established. Secondly, an augmented system is constructed in which the augmented state vector consists of the original state and actuator faults. Thirdly, the H-infinity observer is designed, and the gain of the observer is obtained by the Lyapunov function and linear matrix inequality. Finally, the effectiveness of the proposed strategy is verified by MATLAB/Simulink and Carsim co-simulation.

Attack isolation and location for a complex network cyber-physical system via zonotope theory

This paper investigates the attack isolation (AI) and attack location (AL) problems for a cyber-physical system (CPS) based on the combination of the H-infinity observer and the zonotope theory, where the real control plant in the physical layer is a nonlinear complex network system. Firstly, for actuator AI and AL purposes, two robust H-infinity observers are designed and the stabilities of them are analyzed based on linear matrix inequalities (LMIs). Secondly, the zonotope theory is used to the error dynamic system of the H-infinite observer such that it can calculate iteratively the interval state estimation if the CPS has no attacks. Third, two residuals are constructed and their interval estimates are also given, and furthermore, based on the residual interval estimates, both actuator AI and AL schemes are developed. Besides, sensor AI and AL issues are discussed by modifying the actuator AI and AL schemes. Finally, the effectiveness of the proposed methods is illustrated through a simulation example.

Interval-Observer-Based Fault Detection and Isolation Design for T-S Fuzzy System Based on Zonotope Analysis

This article deals with the fault detection and isolation problems for a class of uncertain discrete-time Takagi-Sugeno (T-S) fuzzy system based on the combination of the H-infinity observer and the zonotope method (ZM). For fault detection (FD) purpose, first, a Luenberger-like H-infinity observer, which is robust to disturbance in a sense of H-infinity performance index is designed under the assumption of the feasibility of an linear matrix inequality. Second, the ZM is applied to the H-infinity observer error dynamic system such that the interval state estimation can be calculated iteratively if the system suffers from neither actuator nor sensor faults. Third, a residual is constructed and its interval estimation is also given, and furthermore, based on the residual interval estimation, an FD scheme is developed. After this, we discuss the fault isolation issue in the similar way to alarm the appearance of the exact type fault: actuator or sensor fault. It is the ZM is applied onto the Luenberger-like observer, the fault detection and isolation performances are improved greatly. Finally, a numerical simulation example is given and some comparisons are also made to the existing results to verify the effectiveness and to show the advantages of proposed method.

Estimating the State-of-Charge of Lithium-Ion Battery Using an H-Infinity Observer Based on Electrochemical Impedance Model

The lithium-ion batteries in the electric vehicles are nonlinear systems with complex electrochemical dynamics, and estimation of battery state-of-charge (SOC) is affected by factors such as environmental temperature and battery current. Considering the above problems, the accurate estimation of battery SOC has always been a difficult and the critical issue of battery management system (BMS). In this paper, the constant phase element (CPE) is introduced to the traditional time domain circuit model by analyzing the electrochemical impedance spectra of lithium-ion batteries. Accordingly, an equivalent circuit model based on electrochemical impedance is constructed by using fractional order theory, which has specific physical significant, leading to the improved estimation accuracy to represent battery voltage. Moreover, the polarization resistance in the model is replaced by Butler-Volmer (BV) equation, which can solve the problem caused by large current and temperature variation during the actual operation of electric vehicles. Next, based on the model, an $\text{H}\infty $ observer is designed for battery SOC estimation, and the proposed SOC observer is tested by real-time experimental data of battery. The efficiency of the proposed model and observer are validated by some simulations and experiment tests.

Online monitoring of state of charge and capacity loss for vanadium redox flow battery based on autoregressive exogenous modeling

Accurate monitoring of state of charge (SOC) and capacity loss is critical for the management of vanadium redox flow battery (VRB) system. This paper proposes a novel autoregressive exogenous model for the vanadium redox flow battery, based on which the model-based monitoring of state of charge and capacity loss is investigated. The offline parameterization based on genetic algorithm and the online parameterization based on recursive least squares are investigated for the proposed model to compare the model accuracy and robustness. Leveraging the parameterized model, an H-infinity observer is exploited to estimate the battery state of charge and capacity in real time. Experimental results suggest that the proposed autoregressive exogenous model can accurately simulate the dynamic behavior of vanadium redox flow battery. Compared with the offline model based method, the observer based on online adaptive model is superior in terms of the accuracy of modeling, state of charge estimation and capacity loss monitoring. The proposed method is also verified with high robustness to the uncertain algorithmic initialization, electrolyte imbalance, and the change of system design and work conditions.

State of charge estimation for battery packs using H-infinity observer in underground mine electric vehicles

ABSTRACTAn H-infinity observer (HIO) for state of charge (SOC) estimation is proposed for a series-connected battery pack in underground mine electric vehicles (UMEVs). In the proposed method, an average virtual cell (AVC) model is defined and the SOC of the AVC model is estimated to represent the pack SOC when all terminal voltage differences (TVDs) between each individual cell in the pack and the AVC are within a pre-set voltage threshold. To make sure all the TVDs are within the threshold, lithium iron phosphate cells are clustered into the group with similar characteristics and the cells in the same group are used to build the sorted battery pack. The experiments of pulse current and current profiles based on both urban dynamometer driving schedule and underground mine driving cycle are conducted on the sorted battery pack to verify the effectiveness of the proposed HIO for the pack SOC estimation under UMEVs.

Estimating the State-of-Charge of Lithium-Ion Batteries Using an H-Infinity Observer with Consideration of the Hysteresis Characteristic

The conventional methods used to evaluate battery state-of-charge (SOC) cannot accommodate the chemistry nonlinearities, measurement inaccuracies and parameter perturbations involved in estimation systems. In this paper, an impedance-based equivalent circuit model has been constructed with respect to a LiFePO₄ battery by approximating the electrochemical impedance spectrum (EIS) with RC circuits. The efficiencies of approximating the EIS with RC networks in different series-parallel forms are first discussed. Additionally, the typical hysteresis characteristic is modeled through an empirical approach. Subsequently, a methodology incorporating an H-infinity observer designated for open-circuit voltage (OCV) observation and a hysteresis model developed for OCV-SOC mapping is proposed. Thereafter, evaluation experiments under FUDS and UDDS test cycles are undertaken with varying temperatures and different current-sense bias. Experimental comparisons, in comparison with the EKF based method, indicate that the proposed SOC estimator is more effective and robust. Moreover, test results on a group of Li-ion batteries, from different manufacturers and of different chemistries, show that the proposed method has high generalization capability for all the three types of Li-ion batteries.

H-infinity Estimation of Eddy Currents in a Tokamak

The estimation of induced “eddy” currents in the metallic structures surrounding the plasma chamber of a tokamak can be very important to have a precise estimation of plasma quantities as toroidal current and shape. In facts, plasma shape identification is mainly based on magnetic measurements (fields and fluxes), which are affected by the presence of these currents and subject to the usual sensor noise affecting electromagnetic probes and to drifts induced by the nuclear environment. The presence of a dynamic observer may help to wash out such persistent contribution and isolate the effect of eddy currents on magnetic measurements. Moreover the on-line estimation of the eddy currents allows to have an on-line prediction of the mechanical stresses induced by the electromagnetic loads in the metallic structures during transients. Although the eddy current dynamics can be well modeled by a linear system, even in the tokamak axisymmetric approximation, the high number of states, the uncertainties, and the process and measurement noise, makes the estimation problem challenging. The present paper shows how the use of a H-infinity observer can mitigate these problems.