Qing Zhao

Qing Zhao
University of Alberta | UAlberta · Department of Electrical and Computer Engineering

B.Sc., Ph.D, P.Eng.

About

113
Publications
18,825
Reads
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2,919
Citations
Citations since 2017
22 Research Items
1331 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Introduction
Fault detection and diagnosis for industrial systems and equipment; fault tolerant control; optimal control and estimation; signal processing
Additional affiliations
July 2017 - present
University of Alberta
Position
  • Professor (Full)
September 2000 - present
University of Alberta
Position
  • Professor (Associate)
September 1995 - October 1999
The University of Western Ontario
Position
  • Research Assistant

Publications

Publications (113)
Article
Full-text available
In this paper, a novel fault detection and isolation (FDI) method for switching linear systems is developed. All input and output signals are assumed to be corrupted with measurement noises. In the proposed method, a ‘lifted’ linear model named as stochastic hybrid decoupling polynomial (SHDP) is introduced. The SHDP model governs the dynamics of t...
Article
Mean time to failure (MTTF) is an important reliability index of fault-tolerant control systems, which is chosen as a design objective in this paper. However, it is usually evaluated from stochastic reliability models, and no analytical expression is available to relate MTTF to controller parameters. To overcome this difficulty, a two-stage design...
Article
Full-text available
In this work, the synthesis of fault tolerant control (FTC) for stochastic stability and H 1 performance is studied. Occurrence of faults in the system is governed by a Markov Chain, so the open-loop system is modelled as a linear system with Markovian jumping parameters. The fault detection and isolation (FDI) decision is modelled as another rando...
Article
Multirate systems are abundant in industry. In this paper, the problem studied is designing a residual generator for fault detection based on multirate sampled data. The key new feature of such a residual generator is that it operates at a fast rate for prompt fault detection. The design is based on optimizing a performance index to obtain an optim...
Article
Full-text available
The problem of observer design for Lipschitz nonlinear systems is considered. A new dynamic framework which is a generalization of previously used Lipschitz observers is introduced and the generalized sufficient condition that ensures asymptotic convergence of the state estimates is presented. The equivalence between this condition and an H<sub>∞</...
Article
In this paper, we propose a nonlinear finite-time control strategy to solve the motion control problem for a quadrotor with a slung load (QSL). This work aims to realize high-performance motion control for the QSL, even in perturbations. To improve the dynamic performance and the robustness of the QSL system, a novel nonlinear controller is designe...
Chapter
Fault detection in non-stationary processes is a timely research topic in industrial process monitoring. The core objective of this research is to tackle anomaly detection in non-stationary industrial processes with manipulated set-point changes and uncertainties in the prior knowledge about the statistical nature of the measurements. In this resea...
Article
Negative pressure wave (NPW) based fluid pipeline leak detection and localization method detects leaks by capturing the pressure inflecting trends and locates leaks by calculating the time difference of arrival (TDOA) of NPW between the upstream and downstream sensors. However, in practical situations, pressure variations under normal working condi...
Article
This paper proposes some new improvements to the traditional constrained predictive fault tolerant control (FTC) method by enlarging the maximal fault tolerant admissible region and reducing the online computational complexity. In general, the generalized parameterization of predictive input and event-triggered predictive regulation are integrated...
Article
Full-text available
In this paper we propose a centralized disturbance observer-based integral-augmented backstepping nonlinear motion control for a multirotor unmanned aerial vehicle (UAV). The approach explicitly compensates for rotor drag forces. The control is termed centralized as it based on the full rigid body vehicle model (i.e., rotational and translational d...
Article
This paper presents a novel robust estimator-based dual-mode predictive fault tolerant control (FTC) design scheme for linear parameter varying (LPV) systems with state/input constraints. The overall FTC is composed of an unconstrained robust fixed FTC component and a constrained robust predictive FTC component. The former is determined by solving...
Article
This paper presents a backstepping disturbance observer based control (DOBC) for trajectory tracking motion control of multirotor Unmanned Aerial Vehicles (UAVs). Two disturbance observers (DO) estimate external force and torque disturbances acting on the UAV. A nonlinear backstepping dynamic state feedback is proposed which uses the DO estimates t...
Article
In this paper, the design and control of a new coaxial tilt-rotor (CTR) unmanned aerial vehicle (UAV) are presented. The CTRUAV is an electric-powered UAV with a special configuration, which is composed of two pairs of tiltable coaxial rotors and a rear rotor. A CTRUAV prototype has been designed by 3D CAD software and constructed according to the...
Conference Paper
Full-text available
In this paper, a disturbance observer-based integral backstepping nonlinear control for motion control of a multirotor unmanned aerial vehicle (UAV) is proposed. The closed-loop is proven globally exponentially stable for the complete UAV dynamics and constant disturbances. Software-in-the-loop (SITL) simulation which validates the robust performan...
Article
Full-text available
Pipeline leak detection has attracted great research interests for years in the energy industry. Continuous pressure monitoring is one of the most straightforward approaches in leak detection which utilizes pressure point analysis (PPA) algorithms to exploit the transient pressure characteristics and identify leak events. However, a critical issue...
Article
Full-text available
image This paper proposes a nonlinear backstepping‐based trajectory tracking control for a quadrotor unmanned aerial vehicle. By incorporating a disturbance observer, the method provides globally exponentially stable tracking error dynamics in the presence of constant force and torque disturbances for position tracking. For time‐varying disturbance...
Article
This paper proposes a general framework for autonomous root-cause fault diagnosis in a complex process. In this framework, as a prerequisite step after conducting fault detection, the potential root-cause candidates are selected using a contribution score-based method (e.g. accumulative rate contribution scores). Then a fully automated procedure is...
Article
Extreme learning machine (ELM) is commonly adopted and best known for its extremely fast learning capability and notable performance. In this paper, a multiple split-complex ELM (Multi-SCELM) regressor based equalization and detection method is proposed for OFDM systems. This method combines ELM regressors for equalization and minimum-distance base...
Article
Full-text available
Using the grid interfacing Voltage Source Converters (VSCs) to perform harmonic control as a smart ancillary function is increasingly studied in recent years. Different from the traditional dedicated harmonic compensation converters, the main function of the high-power smart converters is still delivering real power at a low switching frequency (e....
Article
Full-text available
In this paper, a training scheme for multi-relay clustered wireless sensor networks is proposed for the destination cluster head node to estimate the individual source-relay and relay-destination channels. Compared with an existing training scheme, the proposed one has shown improved efficiency with reduced power and computation time in the trainin...
Article
In this paper, the robust analysis and design of leader-following output regulation for multi-agent systems described by general linear models is given in presence of time-varying delay and model uncertainty. To this aim, a new regulation protocol for the closed-loop multi-agent system under a directed graph is proposed. An important specification...
Article
In a majority of multivariate processes, propagating nature of malfunctions makes the fault diagnosis a challenging task. This paper presents a novel data-driven strategy for real-time root-cause fault diagnosis in multivariate (non-)linear processes by estimating the strength of causality using normalized transfer entropy (NTE) between measured pr...
Article
A novel memory scheduling robust H fault detection filter (FDF) is proposed for a class of discrete-time polytopic uncertain systems with fading channel communication networks. The main merit of this filter-based fault detection method is that it can significantly improve the robustness of FDF to attenuate influences from external disturbance, chan...
Article
This paper presents a novel Sinusoidal Synthesis Based Adaptive Tracking (SSBAT) technique for vibration-based rotating machinery fault detection. The proposed SSBAT algorithm is an adaptive time series technique that makes use of both frequency and time domain information of vibration signals. Such information is incorporated in a time varying dyn...
Article
In this paper, a minimum entropy deconvolution based sinusoidal synthesis (MEDSS) filter is proposed to improve the fault detection performance of the regular sinusoidal synthesis (SS) method. The SS filter is an efficient linear predictor that exploits the frequency properties during model construction. The phase information of the harmonic compon...
Article
The algebraic geometric (AG) approach has been used to identify switched auto regressive exogenous (SARX) models in hybrid systems, and it has several advantages over other SARX identification methods. This paper is focused on improving the estimation accuracy of the AG approach for systems corrupted with indispensable noises. A stochastic hybrid d...
Article
This paper presents a novel data driven technique for the detection and isolation of faults, which generate impacts in a rotating equipment. The technique is built upon the principles of empirical mode decomposition (EMD), envelope analysis and pseudo-fault signal for fault separation. Firstly, the most dominant intrinsic mode function (IMF) is ide...
Article
This paper presents a model-based subspace fault detection method for static and dynamic rotor imbalance faults. This output-only method uses an asymptotic local approach that is sensitive to small changes in modal structure. The method was originally developed for stationary structures but is adapted here for constant-speed rotating machines. Two...
Article
This article presents a novel data-driven method of abnormal pattern identification for real-time monitoring of faults that are evolving within a rotating machine. The concept is built upon partitioning of Hilbert spectrum that are generated on intrinsic mode functions (Hilbert-Huang spectrum) of a measured vibration signal. The partitioning is fur...
Article
This paper investigates the fault-tolerant shape control (FTSC) problem for stochastic distribution systems. For this problem, in addition to measurable input signals, it is assumed that the distribution function of the system output can be evaluated so that it is available. It is also assumed that the system is subject to actuator faults. In this...
Article
In block-mode transmission, single carrier frequency domain equalisation-based ultra-wide-band technique is a promising physical-layer candidate scheme. Here, the authors address the noise variance estimation problem for signal-to-noise ratio estimation in such systems. Our investigations focus on the estimation schemes both robust to the pilot seq...
Article
A sensor fault estimation method is proposed for a general class of uncertain nonlinear systems. Taking the sensor faults as auxiliary states, an augmented descriptor system is constructed. For this augmented descriptor system, an adaptive fuzzy proportional-derivative sliding mode observer is designed to estimate the sensor faults and states, simu...
Data
Full-text available
Article
In this paper, the problem of observer-based control is investigated for networked control systems (NCSs) with probabilistic interval distribution communication delays. In the presence of network-induced delays and packet dropouts in the sensor-to-controller and controller-to-actuator connections, a new model for an observer-based NCS is establishe...
Conference Paper
This paper investigates the fault-tolerant shape control (FTSC) problem for stochastic distribution systems. The available information for the addressed problem is the input and the measurable output Probability Density Function (PDF) of the system. The system is subject to actuator faults. In this case, the main objective is to achieve fault-toler...
Article
In this brief, a new criterion for checking the global asymptotic stability of fixed-point state–space digital filters with time-varying delay and overflow arithmetics is presented. Compared with some existing results, a distinctive feature of the proposed criterion is that it is multi-bound-dependent criterion and can be less conservative than exi...
Article
In this paper, a robust actuator fault diagnosis scheme is investigated for satellite attitude control systems subject to model uncertainties, space disturbance torques and gyro drifts. A nonlinear unknown input observer is designed to detect the occurrence of any actuator fault. Subsequently, a bank of adaptive unknown input observers activated by...
Article
This paper has investigated the problem of estimating unknown frequencies of a given sinusoidal signal with disturbances and noises, as well as its usages for fault detection. On the basis of a parametric linear model of the signal, a gradient estimator with leakage is adopted to identify the frequencies. The estimation mechanism is applied to faul...
Article
This study is concerned with the problem of fault detection (FD) for networked control systems with discrete and infinite distributed delays subject to random packet losses and non-linear perturbation. Both sensor-to-controller and controller-to-actuator packet losses are modelled as two different mutually independent Bernoulli distributed white se...
Article
In this paper, the problem of delay-distribution-dependent stability is investigated for continuous-time recurrent neural networks (CRNNs) with stochastic delay. Different from the common assumptions on time delays, it is assumed that the probability distribution of the delay taking values in some intervals is known a priori. By making full use of...
Article
Full-text available
In this paper a new deconvolution method is presented for the detection of gear and bearing faults from vibration data. The proposed maximum correlated Kurtosis deconvolution method takes advantage of the periodic nature of the faults as well as the impulse-like vibration behaviour associated with most types of faults. The results are compared to t...
Conference Paper
In this paper we propose a method to improve the algebraic geometric solution for identification of Switched ARX models. Despite the advantages of the AG solution, it fails to deliver promising results when the noise level is noticeable. Therefore the proposed method aims to improve the SARX parameter estimation results. In this method matrix diffe...
Article
Full-text available
This study mainly concentrates on analytical characterisation of the detection delays and false alarms in an online sequential probability test-based fault detection (FD) scheme. The probability distributions of the fault detection delay (FDD) and the time between false alarms (TBFA) are investigated. Analytical expressions of the probability densi...
Article
This paper proposes a new method for building time series model to predict machine vibration values. Instead of building a time series model based on the raw machine vibration signal, the vibration signal will be first decomposed into different levels using wavelet packet decomposition (WPD). Sub-signals can be reconstructed from those wavelet pack...
Conference Paper
Full-text available
In this paper, we present an improved algebraic geometry solution for the identification of switched ARX models in the presence of measurement noise. The procedure utilizes the highest order of sub-models, which is estimated by using statistical analysis of effective singular values in matrix rank determination. After embedding sub-models into a la...
Conference Paper
Full-text available
This paper mainly concentrates on extracting dominant frequency estimates from sinusoidal signals corrupted with low frequency disturbances perturbation by means of a synthetic identifier in a real-time manner. It is assumed that the frequencies of such signals are unknown, and the magnitudes of the dominant signals are sufficiently large compared...
Conference Paper
Full-text available
This paper is mainly focused on providing the probabilistic performance criteria for generalized likelihood ratio (GLR) test based fault detection schemes. Analytical expressions regarding probability distribution of the detection delay and time between false alarms are presented, which are validated by simulation. The results can be applied to imp...
Conference Paper
Full-text available
Detection of gear cracks from vibration data is a difficult task. This paper investigates an alternative to the linear predictor residual fault detection based on the nonlinear adaptive control system concept of frequency estimators. The frequency estimator model takes advantage of the sinusoidal nature of vibration and adapts the system model duri...
Article
This paper investigates the parameter estimation problem for a type of nonlinear system with multiplicative component faults and model uncertainties. Multiplicative faults are parameter changes within a process. Model uncertainties can be treated as an unknown input by appropriate transformation. An adaptive observer is proposed to estimate the mul...
Article
Generator thermal sensitivity issue is studied in this paper. Currently, thermal sensitivity test is usually adopted in industries to determine if a generator has been experiencing thermal sensitivity problem. However, this kind of tests has its own disadvantages. In this paper, Support Vector Regression is utilized to provide some valuable informa...
Conference Paper
This paper studies the statistical characteristics of a type of fault detection schemes based on CUSUM(Cumulative Sum) test and present both analytical results and Monte-Carlo simulation results for the probability distribution of the detection delay and the time between false alarms. These results can find important applications in both design and...
Article
Full-text available
The output feedback stabilization problem for the class of nonlinear Lipschitz systems is considered. A discrete-time feedback controller is designed for the sampled-data case, where the output of the plant is only available at discrete points of time and where the objective is to stabilize the system continuously using a discrete-time controller....
Article
The present paper studies the modelling and scheduling problem of maintenance strategies in fault-tolerant control systems (FTCSs) using a stochastic modelling method. In FTCSs, the controller reconfigures itself to accommodate the occurrence of critical faults based on the information obtained from a fault detection and identification (FDI) scheme...
Conference Paper
Full-text available
In this paper, a discrete-time output feedback controller that stabilizes the class of nonlinear Lipschitz systems is presented. The applicability of the controller design in the robotics field is thoroughly discussed from both the modeling and design perspectives. It is shown that the objective of stabilizing the robot manipulator continuously usi...
Article
In this paper the problem of fault detection in multirate sampled-data systems is studied. The lifting technique and direct design approach are used to convert the time-varying multirate design problem into an equivalent time-invariant single-rate discrete-time problem. A performance index is optimized to obtain a set of H∞ optimal and causal resid...
Article
Full-text available
This paper proposes a reliability monitoring scheme for active fault tolerant control systems using a stochastic modeling method. The reliability index is defined based on system dynamical responses and a safety region; the plant and controller are assumed to have a multiple regime model structure, and a semi-Markov model is built for reliability e...
Article
This chapter studies the modeling and scheduling problem of maintenance strategies in Fault Tolerant Control (FTC) systems. It focuses on the unique characteristics of FTC system and constructs discrete semi-Markov chains to describe its operation. FTC system can tolerate some pre-assumed faults; its Fault Detection & Isolation (FDI) scheme has err...
Article
Full-text available
Reliability Modeling of Fault Tolerant Control Systems This paper proposes a novel approach to reliability evaluation for active Fault Tolerant Control Systems (FTCSs). By introducing a reliability index based on the control performance and hard deadline, a semi-Markov process model is proposed to describe system operation for reliability evaluatio...
Article
The problem of sensor fault diagnosis in the class of nonlinear Lipschitz systems is considered. A dynamic observer structure is used with the objective to make the residual converge to the faults vector achieving detection and estimation at the same time. It is shown that, unlike the classical constant gain structure, this objective is achievable...
Article
Full-text available
In this paper active fault-tolerant control (FTC) is designed in a stochastic framework. The fault-tolerant control system (FTCS) is formulated as a set of linear systems governed by two continuous-time finite-state Markov chains, which are used to characterise the system failure modes and the fault detection and isolation (FDI) scheme. This framew...
Article
Sampled-data control systems are widely used in industry. In this paper the problem of fault detection and isolation (FDI) in sampled-data systems is studied. Many existing methods to design a robust sampled-data FDI are based on optimization of a norm based performance index. Our focus in this study is on the selection of the performance index. It...
Conference Paper
Full-text available
The problem of fault detection and diagnosis in the class of nonlinear Lipschitz systems is considered. An observer-based approach offering extra degrees of freedom over classical Lipschitz observers is introduced. This freedom is used for the sensor faults diagnosis problem with the objective to make the residual converge to the faults vector achi...
Article
In this paper, the controller synthesis problem for fault tolerant control systems (FTCS) with stochastic stability and H2 performance is studied. System faults of random nature are modelled by a Markov chain. Because the real system fault modes are not directly accessible in the context of FTCS, the controller is reconfigured based on the output o...
Article
This paper studies the design of fault tolerant control systems (FTCSs) by considering random faults and two categories of design objectives. The FTCSs are modeled in a stochastic framework, resulting from the random fault process. The design objectives include a stability requirement and a probabilistic performance index. Such an index is chosen a...
Article
In this chapter, a stochastic modeling method is used to study the reliability evaluation problem of Fault Tolerant Control Systems (FTCS). The faults in the system are described by a Markov chain, while the Fault Detection & Isolation (FDI) and system operation for reliability evaluation are described by two semi-Markov chains. The semi-Markov des...
Article
Full-text available
The problem of sampled-data state reconstruction in linear time invariant systems is considered. A new full order observer structure that can generate intersample state estimation is introduced. The observer synthesis is carried out using the H<sub>∞</sub> framework and is shown to have some important advantages over the classical lifting technique...
Article
In this paper, a stochastic modelling method is used to study the reliability evaluation problem of fault-tolerant control systems (FTCSs). The faults in the system are described by a Markov chain, while the fault detection and isolation (FDI) and system operation for reliability evaluation are described by two semi-Markov chains. The semi-Markov d...
Conference Paper
In many industrial applications outputs of plants and control signals are measured and generated at different rates, leading to multirate control systems. It is generally believed that the optimal multirate controller performs better than the optimal slow single-rate controller but worse than the optimal fast single-rate controller. This conjecture...
Conference Paper
Full-text available
This paper proposes a novel approach of reliability modeling for Fault Tolerant Control Systems (FTCS). By introducing the reliability function of FTCS based on the control performance and hard deadline, a semi-Markov process model is proposed to describe the system operation for reliability evaluation. The degraded performance of FTCS in the prese...
Conference Paper
Full-text available
Most observer-based methods applied in fault detection and diagnosis (FDD) schemes use the classical two-degrees of freedom observer structure in which a constant matrix is used to stabilize the error dynamics while a post filter helps to achieve some desired properties for the residual signal. In this paper, we consider the use of a more general f...
Conference Paper
Full-text available
This paper investigates the controller synthesis problem for the stochastic fault tolerant control systems (FTCS). The faults of random nature is modeled as a Markov process. Because the real system fault modes are not directly accessible, the controller is reconfigured based on the output of a Fault Detection and Identification (FDI) process, whic...
Conference Paper
Full-text available
In this paper, the controller synthesis problem for fault tolerant control systems (FTCS) with stochastic stability and H 2 performance is studied. The system faults of random nature are modeled by a Markov chain. Because the real system fault modes are not directly accessible in the context of FTCS, the controller is reconfigured based on the outp...
Conference Paper
Full-text available
This paper presents a stabilizing controller parametrization method of Fault Tolerant Control Systems (FTCS) based on the stochastic exponential mean square (EMS) stability of the Markovian model of FTCS. The free parameters of the controller parametrization are real matrices or scalars therefore it is easy to implement numerically. Furthermore, a...
Conference Paper
Full-text available
The problem of sampled-data state reconstruction in linear time invariant systems is considered. A new full order observer structure that can generate intersample state estimation is introduced. The observer synthesis is carried out using the H<sup>∞</sup>framework and is shown to have some important advantages over the classical lifting technique.
Article
Full-text available
The problem of unknown input observer design for non-linear Lipschitz systems is considered. A new dynamic framework which is a generalization of previously used linear unknown input observers is introduced. The additional degrees of freedom offered by this dynamic framework are used to deal with the Lipschitz non-linearity. The necessary and suffi...
Conference Paper
Full-text available
This paper deals with fault detection observer design for linear time-invariant systems with unknown inputs. The design objective is set to minimize a combined performance index H<sub>infin</sub>/H<sub>- </sub> which means to achieve a good compromise between robustness to the disturbance and sensitivity to the fault. Hence, the fault detection obs...
Article
In this paper, the problem of fault detection in sampled-data systems is studied. It is shown that norms of a sampled system are equal to the corresponding norms of a certain discrete time system. Based on this discretization, the sampled-data fault detection problem can be converted to an equivalent discrete-time problem. A framework that unifies...
Conference Paper
Full-text available
Active fault tolerant control systems (FTCS) can be modeled as stochastic systems with Markovian parameters. This paper addresses the modeling and analysis of such systems by using the randomized algorithms. Such algorithms are usually used to perform the robustness analysis or robust control synthesis based on a probabilistic notion. This paper ex...
Conference Paper
Full-text available
The problem of unknown input observer design for Lipschitz nonlinear systems is considered. A new dynamic framework which is a generalization of previously used linear unknown input observers is introduced. The additional degrees of freedom offered by this framework are used to deal with the Lipschitz nonlinearity. The necessary and sufficient cond...
Article
Full-text available
This paper discusses the problem of reliability evaluation for control systems. The reliability evaluation in a system level provides an important criteria on the overall system operating performance and it can be used for guiding system reconfiguration upon the occurrence of a component failure. However, due to the dynamical and feedback relations...
Article
Full-text available
The design of a reliable state feedback control is considered for a class of uncertain systems with actuator failures as well as delays in control inputs. The model uncertainties are unknown but bounded. By applying the Lyapunov stability criteria, state feedback controllers are designed for the systems with control delays in the framework of Linea...
Conference Paper
Full-text available
Multirate systems are abundant in industry. In this paper, the problem studied is designing a residual generator for fault detection based on multirate sampled data. The key new feature of such a residual generator is that it operates at a fast rate. The design is based on optimizing a performance index to obtain a robust parity space based residua...
Article
Full-text available
The problem of observer design for Lipschitz nonlinear systems is considered. A new dynamic framework which is a generalization of previously used Lipschitz observers is introduced. The correct necessary and su-cient condition on the dynamic gain that ensures asymptotic convergence of the new observer is presented. The equivalence between this cond...
Article
The reliable control design problem for uncertain systems with time delays as well as actuator failures in the input channels is discussed. A sufficient condition is established such that the closed-loop system stability and a time-domain integral quadratic constraint are satisfied for both a normal system and a system with possible actuator failur...
Article
In this paper, a real-time fault detection and isolation (FDI) scheme for dynamical systems is developed, by integrating the signal processing technique with neural network design. Wavelet analysis is applied to capture the fault-induced transients of the measured signals in real-time, and the decomposed signals are pre-processed to extract details...
Article
Full-text available
In this paper, the stability and performance of the fault tolerant control system (FTCS) are studied. The analysis is based on a general framework of integrated FTCS, in which the system component failure and the fault detection and isolation (FDI) scheme are characterized by two Markovian parameters. In addition, the model uncertainties and noise/...