Search

Based on the delta operator approach, a new method of actuator fault estimation for a two-stage chemical reactor system is presented with time-delay and outside disturbances. Firstly, a nonlinear delta operator mathematical model is established to describe the two-stage chemical reactor systems by using the mechanism analysis method. In order to estimate the actuator fault, the proportional–integral observer (PIO) is employed as the state estimator. Meanwhile, a novel delta operator-based actuator fault estimation algorithm is proposed. Then, by means of the Lyapunov–Krasovskii functional technique, sufficient conditions are derived to guarantee that the error system is asymptotically stable with a predefined H ∞ performance index. Next, the desired PIO can be designed. Finally, simulation results are given to illustrate the effectiveness of the proposed methods.

This paper investigates the problem of consensus for one kind of sampled-data heterogeneous multi-agent system. We first discretize the continuous-time networked system by the method of sampled-data. Then we use a system transformation to transform the multi-agent system into the reduced-order error system. Two consensus algorithms with and without velocity measurement will be considered respectively. We obtain two sufficient conditions for the networked systems with and without velocity measurement to reach consensus through analyzing the stable problem of the reduced-order systems. Simulations are given to verify the effectiveness of the results.

This article investigates the observer-based finite-time $H_\infty$ control problem for interconnected fuzzy systems with quantization and random network attacks, where two types of network attacks including denial-of-service (DoS) and fault data injection (FDI) attacks are considered. In order to achieve the occupancy reduction of network resources, the measured outputs of interconnected systems are quantized through a logarithmic quantizer before being transmitted by the communication channel. Combining the effects of quantization and random network attacks, an observer-based control model is first constructed. Then, based on Lyapunov functional approach and stochastic analysis technique, some sufficient conditions are presented such that the considered closed-loop interconnected system is stochastically finite-time bounded with a prescribed disturbance attenuation level, and the gain matrices of fuzzy observer and fuzzy controller can be found by solving an optimization algorithm with linear matrix inequalities constraints. Finally, two simulation examples are given to illustrate the validity of the proposed approach.

This paper provides a practical design method for hybrid unbonded post-tensioned precast concrete joints. Such joints featured with self-centering capacities have been widely favored in recent years. However, the absence of design methods hinders their further promotion. To solve the issue, two methods for calculating mechanical behavior of the joints were first studied: characteristic points method and iterative method. The effectiveness of the methods was verified by the existing test results. On this basis, a joint design method considering both yield bearing capacity and energy dissipation capacity was proposed. Moreover, to facilitate design, some factors affecting the bearing capacity were discussed. A five-story frame structure was designed by the proposed design method, and the influence of two design factors on structural response was analyzed by utilizing nonlinear time-history method. The analysis results show that: with the increase of energy dissipation factor αs, the post-earthquake residual deformation of the structure tends to increase linearly, while the accumulated damage of the structure will decrease continuously; both overdesign and underdesign of bearing capacity of the joint are unfavorable; and near-field earthquake may cause irreparable damage to structural columns, making the residual deformation of structures contrary to the self-centering capacity of joints, which shall be considered during engineering design.

In this technical note, the problem of observer-based controller design is considered for sensor networked systems subject to distributed hybrid-triggered transmission scheme and input quantisation. A novel observer model based on coupled transmission signals from multi-channel is first proposed to estimate unavailable state variables and exploited in the feedback protocol. In order to provide a trade-off between saving network resources and improving system performance, a distributed hybrid-triggered transmission scheme with communication delays is adopted to update the observer input signals. For the sake of further reducing the occupancy of network resources, the control input signal is quantised by a logarithmic quantiser. Then, by making use of the Lyapunov stability theory, the sufficient conditions guaranteeing the system asymptotically stable are presented. Moreover, the explicit expressions of observer and controller parameters are achieved by solving a set of linear matrix inequalities. Finally, two simulation examples are provided to illustrate the rationality of the proposed control method.

This paper is engaged in investigating the observer-based event-triggered output feedback control issue for fractional-order cyber–physical systems with stochastic network attacks, where the order scale of the fractional derivative used is 0 α 1 . An event-triggered scheme (ETS) with output-independent threshold is proposed to renew the observer input so as to reduce the redundant data communications. Considering the effects of the ETS and network attacks, a novel closed-loop fractional-order control system model is constructed. By making use of fractional-order Lyapunov indirect approach, sufficient conditions that can insure the global stochastic asymptotic stability of the established closed-loop control system are obtained. Moreover, according to the singular value decomposition (SVD) of matrix, the co-design of the gains of the desired observer and controller is addressed by finding the solution of the linear matrix inequalities (LMIs). Finally, a numerical example and a diesel engine control system are provided to validate the feasibility of the adopted observer-based control method.

The additional damping ratio (ADR) is an important indicator for evaluating the damping effect of structures with energy-dissipation devices. Most existing methods for determining the ADR require an analysis of the structural dynamic response and complex iterative calculations. An innovative simplified calculation method for determining the ADR of a structure supplemented by nonlinear viscous dampers is proposed. This method does not require the dynamic response of the structure to be calculated and only requires the structural characteristics, excitation frequency, and damper parameters. In this study, several typical calculation methods for the ADR were analysed. Then, a calculation formula for the ADR was derived with consideration of harmonic excitation under the condition where the excitation frequency is equal to the structural natural frequency, without calculation of the structural dynamic response or an iterative process. The effect of the excitation frequency on the calculated value of the ADR with different damping exponents was studied. Accordingly, the response spectrum average period (RSAP) was considered as the excitation period of ground motion to evaluate the excitation frequency, and a simplified calculation method for the ADR considering the effect of the excitation frequency characterised by the RSAP of the ground motion was established. Finally, the accuracy and effectiveness of the proposed method were verified by comparison with ADRs calculated using other methods.

In order to improve the fault diagnosis theory of switched systems, observer-based method is proposed to deal with the fault diagnosis issue subjected to the parameter uncertainty, unknown process disturbances and unexpected faults. By employing proportional-integral observer (PIO) technique and the average dwell-time (ADT) method, an H∞/H− performance level is considered to ensure the worst case of robustness to the disturbance and sensitivity to the fault simultaneously. Moreover, the obtained fault diagnosis observer can give accurate fault estimation online for the piecewise constant fault. Finally, a two-tank system example is introduced in the end to show the effectiveness of the proposed results.

This paper investigates the adaptive event-triggered synchronization control problem for a class of complex networks with quantization and cyber-attacks. For reducing the burden of communication and computation, an adaptive event-triggered scheme and a logarithmic quantizer are both introduced. Firstly, considering the effect of adaptive event-triggered sampling, quantization and cyber-attacks, a novel synchronization error model is established. By using Lyapunov functional method, some sufficient conditions are derived to guarantee the asymptotic stability of the augmented synchronization error system. Moreover, the co-design of the controller and adaptive event-triggered scheme are also solved in terms of solving the solution of linear matrix inequality(LMI). Finally, a numerical example is exploited to show the effectiveness of the proposed method.

The paper is concerned with the observer-based robust control problem for fractional-order (FO) nonlinear uncertain systems subject to control input saturation and measurement quantization, in which the fractional commensurate order satisfies α ∈ ( 0 , 1 ) . The state measurements of observer are quantized by a logarithmic quantizer. Firstly, by introducing a continuous frequency distributed equivalent model of fractional integrator, sufficient condition for guaranteeing the asymptotic stability of closed-loop FO systems is established via the indirect Lyapunov approach. Then, by using matrix’s singular value decomposition (SVD) and linear matrix inequality (LMI) technique, the co-design problem of desired observer and controller gains are derived, which will be shown that the solution guarantees the stability of closed-loop FO nonlinear uncertain control systems. Finally, a simulation example is given to illustrate the validity of this method.

This paper investigates the problems of fault estimation and fault accommodation for a class of nonlinear switched systems. First, an augmented switched system is constructed by forming an augmented state vector composed of the state vector and the fault vectors. Then, an unknown input observer (UIO) is designed for the augmented switched system to estimate the augmented state vector. With the assist of the average dwell-time (ADT) method and the switched Lyapunov function technique, sufficient conditions are obtained to guarantee that the error system is globally uniformly asymptotically stable (GUAS) with a prescribed H∞ performance index. An algorithm is provided to show the procedures on how to design the UIO. Moreover, the results are extended to the measurement disturbances case. Based on signal compensation principle, a dynamic output feedback controller is designed to ensure the asymptotical stability of the closed-loop system. Finally, simulation results are presented to demonstrate the proposed technique.

In this section, the problem of robust FE observer for discrete-time switched systems with unknown input is investigated. Firstly, let the state vector and fault vector of the initial system into the state vector of the augmented system, which can obtain the augmented system. Next, based on the P-radius technique, an interval observer is designed to estimate the state and the fault of the augmented system which can ensure the error system is stable. Then, some assumptions are given in order to simplify the calculation, and the LMI technique and Schur Complement Lemma are used to solve the observer. Finally, an interval hull computation approximation algorithm of FE is obtained for discrete-time switched systems. Compared with the region-based method, this method has more precise boundary and higher efficiency.

This section investigates the problem of FE for a continuous-time switched system with actuator and sensor faults. Firstly, based on the ADT method and switched Lyapunov function, an FE observer is designed for the augmented switched system, which can ensure that the error system is asymptotically stable with an \(H_\infty \) performance index. Next, an algorithm is proposed to realize FE accurately. Finally, an example is given to illustrate the effectiveness of the designed methods.

This chapter deals with the problems of non-fragile FEA for continuous-time switched systems are investigated. Firstly, a non-fragile PIO is designed to achieve actuator FE for continuous-time switched systems. Based on the ADT method and the switched Lyapunov function technique, a new actuator fault estimator is obtained. Then, based on the online FE information, a PIO-based non-fragile state feedback controller is designed to compensate for the effect of the actuator fault by stabilizing the closed-loop switched system. Finally, an F-18 aircraft example is borrowed to illustrate the obtained contributions.

In this section, the problem of actuator FD for discrete-time switched systems with output disturbance is investigated. By using the descriptor observer method, an \(H_\infty \) FD filter is designed to guarantee that the augmented system is admissible and satisfies a prescribed \(H_\infty \) performance index. By utilizing switched Lyapunov function approach, a sufficient condition for the admissible of the augmented system is obtained. Based on the obtained results, the desired FD filter can be designed. All the results are formulated in the form of LMIs. Finally, an example is proposed to illustrate the effectiveness of the developed method.

In this section, the problem of FD is investigated for continuous-time switched systems. A UIO is designed as an FD filter to generate the residual signal. To make the residual signal sensitive to the fault and robust to the unknown disturbances, we proposed \(H_{-}/H_{\infty }\) designed method by employing the switched Lyapunov function and the ADT techniques. Furthermore, sufficient conditions for the existence of such an FD filter are exploited to guarantee that the error systems under ADT condition are asymptotically stable with an \(H_{\infty }\) / \(H_{-}\) performance index. Finally, a practical example is provided and simulation results are conducted to demonstrate the effectiveness of the proposed approach.

This section investigates the problems of actuator FEA for discrete-time switched systems with state delay. By using reduced-order observer method and switched Lyapunov function technique, an FE algorithm is achieved for the discrete-time switched system with actuator fault and state delay. Then based on the obtained online FE information, a switched dynamic output feedback controller is employed to compensate for the effect of faults by stabilizing the closed-loop systems. Finally, an example is proposed to illustrate the obtained results.

In this section, an observer-based fault detection method is proposed to deal with the issue of real-time-weighted fault detection for discrete-time switched systems. By employing the UIO technique and ADT method, the \(H_{\infty }/H_2\) and \(H_{-}\) performance levels are considered to ensure the robustness to the known and unknown input and the sensitivity to the fault. Finally, a practical example is given to demonstrate the effectiveness of the proposed methods.

In this section, a novel FD and FE method is proposed for discrete-time switched systems. In the proposed design, an FD observer with online learning capability is utilized to generate a residual, which is obtained by comparing the system output with respect to the observer output. A fault is successfully detected if the generated residual exceeds a priori chosen threshold. Subsequently, the fault magnitude is estimated online by using a suitable parameter update law.

In this paper, the robust fault estimation observer problem for discrete-time switched systems with unknown input is investigated. First of all, The state vector and fault vector of the initial system are transformed into the state vector of the augmented system, and then we can obtain the augmented system. Next, an unknown input observer(UIO) is designed based on the P-radius technique to estimate the state and fault of the augmented system, that can ensure the stability of the error system. In order to achieve the exothermic goal in this paper, some assumptions are given, and the observer is solved by using linear matrix inequality (LMI) technique and Schur complement lemma. At the last, an interval hull computation approximation algorithm of fault estimation is obtained. Compared with other methods, this method is more precise and efficient.

In this paper, we focus on the consensus for a class of heterogeneous networked systems by applying the second-order neighbors information. According to the communication with their neighbors, two kinds of linear consensus control algorithms are put forward for agents. Through using graph theory and matrix theory, it provides sufficient conditions for the consensus of heterogeneous networked systems with undirected connected topology.

In this paper, the problem of fault estimation for continuous-time switched system with actuator and sensor faults is investigated. Firstly, based on the average dwell-time method and switched Lyapunov function, a fault estimation observer is designed for the augmented switched system, which can ensure that the error system is asymptotically stable with an H ∞ performance index. Next, an algorithm is proposed to realize fault estimation accurately. Finally, an example is given to illustrate the effectiveness of the designed methods.

Insufficient grouting of sleeve connection in precast concrete (PC) structure will significantly decrease the bearing capacity of connection joints and increase the risk of premature failure of PC structures. To evaluate the bond behavior of insufficiently grouted sleeve connection, a total of 126 specimens with four types of insufficient grouting configuration (uniform, longitudinal, radial and inclined) have been experimentally investigated. The influences of the configuration and defect level of insufficient grouting on the bond failure mode and bond stress-slip curves were analyzed. The test results show that the specimens fail in the shifting failure mode from the tensile fracture of rebar to the pulling out of rebar with the increase of defect level for all types of grouting defects, especially when the defect level excesses 30%. Moreover, the bond strength and the slip are found to decrease with the increasing of defect level, and empirical expressions have been presented for both the normalized bond strength and slip. Finally, a bond stress-slip constitutive model has been proposed considering the failure modes under different defect levels, which is helpful to the assessment of structural performance of PC structures in practice.

This paper is concerned with the state feedback H∞ control problem for hybrid-triggered networked control systems (NCSs) with stochastic nonlinearity and state quantization. In order to establish a higher utilization of the network resources, a hybrid-triggered transmission scheme (HTTS) and measurement size reduction scheme are introduced. Firstly, the HTTS is presented such that the signal can be transmitted according to the law. Then the measurement size reduction scheme, i.e., the logarithmic quantization is applied. Then, considering the effect of HTTS and quantization, the original NCSs model is reformulated as a new hybrid-triggered NCSs with communication delay. By using Lyapunov functional method and linear matrix inequality technique, sufficient conditions for stochastical stability with a prescribed H∞ performance level are established, and the design of controller and trigger parameters can be obtained. Finally, a simulation example is given to illustrate the effectiveness of the proposed method.

The presence of cracks in concrete will accelerate the corrosion of steel reinforcement causing the performance degradation of reinforced concrete (RC) structure. Based on the electrochemical principle, a numerical model of macro-cell corrosion has been developed to predict the corrosion rate of steel reinforcement in cracked RC members. In this model, the areas of the separate anode and cathode are established by the crack width, and the electric resistivity of concrete material is modified by considering the effects of water-binder ratio and other factors. When the corrosion rate of steel reinforcement is taken as the mean value of the corrosion current density of anode zone, the corrosion rate can then be numerically solved from the proposed model with given boundary conditions. Test data from the 2-year laboratory experiments of authors and literature has been collected to verify the proposed model. The comparisons between the test and prediction results show that the proposed model is of capability to predict the corrosion rate with a good accuracy. Finally, the parametric studies show that the crack width, water/cement ratio, chloride concentration, thickness of concrete cover, and relative humidity has significant influences on the corrosion rate of reinforcement in cracked RC structure.

In this paper, the problem of fault detection filter design for a class of nonlinear switched systems is investigated. First, the nonlinear switched system is transferred into a Takagi–Sugeno fuzzy switched model by using fuzzy if-then rules. Then, based on the persistent dwell-time switching signal and the quasi-time-dependent Lyapunov function technique, an efficient condition of the performance analysis result is obtained. Based on this, a fuzzy-parameter-dependent fault detection filter is designed such that the resulting error system is globally uniformly asymptotically stable with a nonweighted $H_\infty$ performance index. Finally, simulation results are provided to show the effectiveness of the proposed technique.

This paper addresses the problem of H ∞ filter design for T-S fuzzy systems with saturation nonlinearities. For the purpose of reducing network burden, an output-dependent triggering scheme and a quantizer are introduced at the same time. The output-dependent triggering scheme is applied to determine whether or not the current instant information should be transmitted to the quantizer. Saturation nonlinearities, as a common phenomenon in networked systems due to the physical or technological constraints, is also considered here. Then a filtering error model with aforementioned characteristics is established. By using Lyapunov functional approach and stochastic analysis techniques, some matrix inequality-based sufficient conditions for the existence of the fuzzy filter are obtained. Moreover, a co-design algorithm for solving the suitable filter and the event generator is derived. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed approach.

In this paper, the finite-frequency fault detection filter design for discrete-time switched systems is investigated. The frequencies of the faults and the unknown disturbance input are assumed to be finite and in three known intervals, qualified as low-, middle-, and high-frequency intervals. Based on the switched Lyapunov function and the generalized Kalman-Yakubovic-Popov lemma, efficient conditions are obtained to guarantee the existence of a finite-frequency fault detection filter, such that the error system is asymptotically stable with an H∞/H- performance index. Finally, a chemical reactor control system is employed to illustrate the obtained techniques.

Determining land surface reflectance (LSR) is important for satellite retrieval of aerosol optical depth (AOD). Many studies ha ve focused on the development of AOD retrieval through using different land surface reflectance determination algorithms. However, there is still lack of a comprehensive comparison among those algorithms. In this study, AOD retrieval algorithms with different land surface reflectance assumptions were compared and analyzed using Advanced Himawari Imager (AHI) data. The results demonstrate that the AOD retrieved by the algorithm considering the land surface bidirectional reflectance distribution function (BRDF) effects (Method 3) has a higher accuracy than that based on the dark target (Method 1) and second lowest reflectance (Method 2) methods. The overall correlation coefficient between the AOD retrievals considering land surface BRDF and AERONET AOD measurements is 0.93 and the Root Mean Square Error (RMSE) is 0.13. In addition, there are 68.91 % of AOD matchups falling within the expected error (±0.05 ± 0.2 × AOD AERONET). Method 3 shows a more robust performance than the other two methods for different seasons, normalized difference vegetation index (NDVI) values and scattering angles. It also shows the advantages of AOD retrieval in urban regions with relative ly high LSR. The AOD retrievals based on Method 2 show the best agreement with MODIS 1 km AOD product, while Method 1 AODs are much closer to the MODIS 10 km AODs. The differences of annual average values of AHI AOD retrievals using different algorithms can be high to 0.13 at 11:00 (Beijing Time) over the Beijing-Tianjin-Hebei (BTH) region, which could cause a 23.6Wm-2 discrepancy when calculating the direct aerosol radiative effect (DARE) at the bottom of the atmosphere.

In this paper, the problem of actuator fault detection for discrete-time switched systems with output disturbance is investigated. By using the descriptor observer method, an H∞ fault detection filter is designed to guarantee that the augmented system is admissible and satisfies a prescribed H∞ performance index. By utilizing switched Lyapunov function approach, a sufficient condition for the admissible of the augmented system is obtained. Based on the obtained results, a desired fault detection filter can be designed. All the results are formulated in the form of linear matrix inequalities. Finally, an example is proposed to illustrate the effectiveness of the developed method.

This paper investigates the problem of fault detection for the time-delayed networked systems. Different from the traditional fault detection systems, the considered system has the following feature: (i) the measured output of system is subject to sensor saturations; (ii) the system considers the influence of transmission delay and disturbance, which are two common phenomenon under the network environment; (iii) an output-dependent triggered scheme and measurement quantization are introduced in order to reduce the network bandwidth burden and improve communication efficiency. Considering aforementioned characteristics, a new type of fault detection filter model is builded. By constructing a Lyapunov functional, some new sufficient conditions for both the existence of above filter and the mean square stability of networked systems are obtained in terms of linear matrix inequalities (LMIs). Moreover, the suitable fault detection filter and the event generator can be co-designed simultaneously. Finally, a simulation example and an industrial continuous stirred tank reactor system are employed to verify the effectiveness and usefulness of the proposed method.