Exogenous System Research Articles

Finite frequency fault estimation and fault-tolerant control for dynamics of high-speed train based on descriptor systems

In this paper, novel fault estimation and fault-tolerant control methods are proposed for dynamics of high-speed train based on descriptor systems with uncertainties in finite frequency domain. Dynamics of high-speed train is established based on multi-particle model considering that basic resistance is seen as the coefficient of state variables, and additive resistance and the operating noise are seen as multi-source disturbance. Concurrent actuator, sensor faults, and wind gust are considered simultaneously; wind gust is modeled as a disturbance generated by the exogenous system, and an uncertain descriptor system with actuator fault and the exogenous disturbance is established by seeing the sensor fault of high-speed train as the state variables. A robust disturbance-observer-based fault estimation method is proposed to decouple the non-linearity of the descriptor system, so that the combining estimation of the fault and wind gust is implemented. This observer has an unknown input structure, and its gain matrices are formulated as linear matrix inequalities. The observer not only guarantees the augmented state estimation error is asymptotic stable but also the actuator fault estimation and wind gust estimation errors are robust to the multi-source disturbance and the uncertainties. Based on the estimation results, the fault-tolerant controller associated with the state estimation, faults estimation, and wind gust estimation results is proposed to implement a stable close-loop fault-tolerant control for dynamics of high-speed train. Simulation examples are given to illustrate the effectiveness of this method.

Heme is involved in the exogenous ALA-promoted growth and antioxidant defense system of cucumber seedlings under salt stress

A biosynthetic precursor of tetrapyrrol, 5-aminolevulinic acid (ALA), is widely used in agricultural production, as an exogenous regulatory substance that effectively regulates plant growth. Previous studies have shown that heme and chlorophyll accumulate in plants under salt stress, when treated with exogenous ALA. In this study, we explored the regulatory role of heme in plants, by spraying 25 mg L–1 ALA onto the leaves of cucumber seedlings treated with heme synthesis inhibitor (2,2'-dipyridyl, DPD) and heme scavenger (hemopexin, Hx), under 50 mmol L–1 NaCl stress. The results showed that NaCl alone and DPD + Hx treatments to cucumber seedlings subjected to salt stress adversely affected their growth, by decreasing biomass accumulation, root activity, and root morphology. In addition, these treatments induced an increase in membrane lipid oxidation, as well as enhancement of anti-oxidase activities, proline content, and glutamate betaine. However, exogenous ALA application increased the plant growth and root architecture indices under NaCl stress, owing to a lack of heme in the seedlings. In addition, cucumber seedlings treated with DPD and Hx showed inhibition of growth under salt stress, but exogenous ALA effectively improved cucumber seedling growth as well as the physiological characteristics; moreover, the regulation of ALA in plants was weakened when heme synthesis was inhibited. Heme biosynthesis and metabolism genes, HEMH and HO1, which are involved in the ALA metabolic pathway, were upregulated under salinity conditions, when ferrochelatase activity was inhibited. Application of exogenous ALA increased the heme content in the leaves. Thus, exogenous ALA may supplement the substrates for heme synthesis. These results indicated that heme plays a vital role in the response of plants to salinity stress. In conclusion, heme is involved in ALA-mediated alleviation of damage caused to cucumber seedlings and acts as a positive regulator of plant adaption.

Composite hierarchical anti‐disturbance control for discrete‐time singular Markov jump systems under double‐layer switching scheme

This work endeavors to investigate the composite hierarchical anti-disturbance control issue for discrete-time singularly perturbed Markov jump systems with multiple disturbances. These disturbances include two types, one is the external disturbance that belongs to l 2 0 , ∞ $$ {l}_2\left[0,\infty \right) $$ , and the other is generated by an exogenous system. To attenuate and reject the negative effects of two types of disturbances, a composite anti-interference controller with integrated feedforward and feedback strategies is designed. Notably, the transition probabilities of the Markov chain are considered to be piecewise time-varying and subject to a persistent dwell-time switching scheme. Fully considering the two-time scales phenomenon and the switching characteristics of systems, a mixed parameter/mode-dependent Lyapunov function is constructed to assure that all the signals of the closed-loop system satisfy the mean-square exponential stability with the anticipant ℋ ∞ $$ {\mathscr{H}}_{\infty } $$ performance. Eventually, two illustrative examples are presented to verify the efficiency and superiority of the designed composite control strategy.

A framework for the mitigation and adaptation from heat-related risks to infrastructure

The rising frequency of heat-related hazards as a result of climate change will increasingly affect heat-sensitive infrastructure assets. Recent studies quantify the heat-related risk to infrastructure, with some exploration of individual mitigation strategies, however missing in literature is an infrastructure sector-transferable and comprehensive framework for analyzing future risk and performing evaluation of several options for risk reduction. This paper introduces a generic framework to: quantify heat-related risks to infrastructure assets in a transferable manner; assess the effects of future exogenous systems changes, and; evaluate several practical mitigation strategies. The framework is applied to the asphalt road network in Adelaide, Australia. This case study explores heat-related risk under present and future climate hazard and traffic stressor scenarios and critical evaluation of mitigation strategies. The strategies explored affect both hazard and vulnerability elements of risk, including: asphalt binder materials, reflectivity additives, and traffic volume, loading or speed management. Results indicate up to a 19% increase in risk from 2020 to 2090 as a result of climate change. Road replacement strategies are identified as most effective, reducing risk by up to 33% in 2090. The framework shows value in developing comprehensive and practical strategies for managing heat-sensitive infrastructure assets into the future.

Use of Anthracophyllum discolor and Stereum hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste.

This study evaluated the use of the white-rot fungi (WRF) Anthracophyllum discolor and Stereum hirsutum as a biological pretreatment for olive mill solid mill waste (OMSW). The WRF strains proposed were added directly to OMSW. The assays consisted of determining the need to add supplementary nutrients, an exogenous carbon source or use agitation systems, and evaluating WRF growth, enzyme activity, phenolic compound removal and lignin degradation. The highest ligninolytic enzyme activity was found at day 10, reaching 176.7 U/L of manganese-independent peroxidase (MniP) produced by A. discolor, and the highest phenolic removal (more than 80% with both strains) was reached after 24 days of incubation. The confocal laser scanning microscopy analysis (CLSM) confirmed lignin degradation through the drop in lignin relative fluorescence units (RFU) from 3967 for untreated OMSW to 235 and 221 RFU, showing a lignin relative degradation of 94.1% and 94.4% after 24 days of treatment by A. discolor and S. hirsutum, respectively. The results demonstrate for the first time that A. discolor and S. hirsutum were able to degrade lignin and remove phenolic compounds from OMSW using this as the sole substrate without adding other nutrients or using agitation systems. This work indicates that it could be possible to design an in situ pretreatment of the valorization of OMSW, avoiding complex systems or transportation. In this sense, future research under non-sterile conditions is needed to evaluate the competition of WRF with other microorganisms present in the OMSW. The main drawbacks of this work are associated with both the low reaction time and the water addition. However, OMSW is seasonal waste produced in one season per year, being stored for a long time. In terms of water addition, the necessary optimization will be addressed in future research.

Hydromorphone impurity 2,2-bishydromorphone does not exert mutagenic and clastogenic properties via in silico QSAR prediction and in vitro Ames and micronucleus test

The opioid agonist hydromorphone is indicated for the management of severe acute and chronic pain given that alternate treatments are insufficient. While the genotoxicity profile of hydromorphone is well investigated, little is known about the genotoxic potential of its impurities. In this study, 2,2-bishydromorphone was tested in silico and in vitro for both its mutagenic potential in an Ames test performed with Salmonella typhimurium and Escherichia coli tester strains up to a maximum concentration of 5 mg per plate in the absence and presence of metabolic activation. Furthermore, it was tested for its ability to induce micronuclei in TK6 cells in a micronucleus test up to a maximum concentration of 500 µg/mL with or without an exogenous metabolic activation system. 2,2-Bishydromorphone did not reveal any potential for inducing mutagenicity or clastogenicity under the conditions of the respective tests and is therefore considered non-mutagenic and non-clastogenic/aneugenic in vitro. These results are in line with negative in silico quantitative structure-activity relationship (QSAR) prediction for 2,2-bishydromorphone mutagenicity and clastogenicity and provide evidence of good correlation of in silico and in vitro data. Conclusively, these studies add important new clinically relevant information on the safety of hydromorphone as the impurity of 2,2-bishydromorphone is proven to be non-mutagenic and non-clastogenic.

Anti-disturbance synchronization of fuzzy genetic regulatory networks with reaction-diffusion

This paper intends to focus on the anti-disturbance synchronization issue for genetic regulatory networks subject to reaction-diffusion terms based on the Takagi-Sugeno fuzzy model. In view of the fact that disturbances are widespread in actual control engineering, the stability of the aforementioned systems would be affected, therefore, ensuring the stability of closed-loop genetic regulatory networks is the main goal of this paper. The unknown disturbances are supposed to be generated by an exogenous system, which can be estimated by developing disturbance observers. Furthermore, integrating the disturbance observers with fuzzy rule-based conventional control laws, a new anti-disturbance control strategy is proposed to reject the disturbances and guarantee the desired dynamic performances. Then, by constructing a proper Lyapunov function and using advanced decoupling techniques, some sufficient conditions in the form of linear matrix inequalities, to guarantee the asymptotic stability of the error system, are obtained. Finally, an illustrated example is presented to demonstrate the effectiveness and superiority of the proposed method.

Bipartite consensus for a class of nonlinear multi-agent systems under switching topologies: A disturbance observer-based approach

This paper considers the leader-following bipartite consensus for a class of nonlinear multi-agent systems (MASs) subject to exogenous disturbances under directed fixed and switching topologies, respectively. Firstly, two new output feedback control protocols involving signs of link weights are introduced based on relative output measurements of neighboring agents. In order to estimate the disturbances produced by an exogenous system, a disturbance observer-based approach is developed. Then, sufficient conditions for leader-following bipartite consensus with directed fixed topologies are derived. Furthermore, by assuming that each switching topology contains a directed spanning tree, it is proved that the leader-following bipartite consensus can be realized with the designed output feedback control protocol if the dwell time is larger than a non-negative threshold. Finally, numerical simulations inspired by a real-world DC motors are provided to illustrate the effectiveness of the proposed controllers.

Composite anti-disturbance quantized control for interconnected semi-Markovian systems with multiple disturbances and actuator faults

This paper investigates the composite anti-disturbance control problem for the interconnected Semi-Markovian systems with multiple disturbances and actuator faults, where the state signal of each subsystem is quantized by logarithmic quantizer before being transmitted into controller. Two representative types of external disturbances are considered simultaneously, one is norm-bounded and the other is formulated by an exogenous system. To attenuate the modelling disturbance and diagnose the actuator faults, a distributed disturbance observer with fault diagnosis observer is constructed. Then, the composite quantized control methodology is proposed to compensate disturbances and faults, and stabilize the overall system. On the basis of proper Semi-Markovian Lyapunov-Krasovskii functional, some sufficient criterions are derived to ensure the stochastic stability with a prescribed performance. Moreover, the desired observer and controller gain matrices can be attained via linear matrix inequalities (LMIs) technique. Finally, a simulation example is given to demonstrate the feasibility and effectiveness of theoretical results.

Synergistic use of intrusive and non-intrusive model order reduction techniques for dynamical power grids

This manuscript combines the recently developed nonlinear moment-matching (NLMM) technique with dynamic mode decomposition (DMD) to obtain a simulation-free reduction framework for power systems. Unlike the conventional model reduction methods for power systems, where the external area is linearized, we consider the nonlinear effective network (EN) and the synchronous motor (SM) power grid models. First, the reduced system is constructed from the solution of the underlying approximate Sylvester equation by exciting the system with user-defined inputs from a representative exogenous system. Then, a non-intrusive reduction is performed using DMD to approximate the nonlinear function via Koopman modes in an equation-free manner. The advantage is that a “simulation-free” nonlinear model order reduction framework is obtained to approximate the response of the large-scale power grid models. Finally, we substantiate our observations using numerical simulations of reduced EN and SM models of the IEEE 118 and IEEE 300 bus systems for realistic fault scenarios. Results show that the overall CPU times of the reduced-order models are lowered to half as compared to the original models while maintaining the fidelity. The results are also compared with POD-DEIM for reference.

Adaptive synchronization with disturbance rejection for under-actuated ships with disturbances under thruster saturation

An adaptive synchronization control scheme with the disturbance estimation and rejection is proposed for the under-actuated ships with unknown time-varying disturbances under thruster saturation effects without leader ship’s velocities. The unknown time-varying disturbances are described as the sinusoidal disturbances whose amplitudes, frequencies and phases are uncertain. The disturbances are expressed by using an unknown parametric exogenous system which is converted into a canonical model with the disturbances as inputs. A disturbance filter is constructed to estimate the state vector in the canonical model such that the disturbances are represented by the parametric equations with exponentially decaying errors. The main highlights lie in that the anti-disturbance problem is transformed into the adaptive control problem based on parametric disturbance representations. This enables that the additional control filters are constructed to generate the filtered signals of the control deviations to on-line correct feedback control errors such that the adaptive disturbance rejection control would be workable under thruster saturation effects. The proposed adaptive synchronization scheme achieves the disturbance rejection and the thruster saturation attenuation simultaneously. Simulations with comparisons demonstrate the effectiveness and the superiority of the control scheme.

Composite disturbance rejection control of Korteweg-de Vries-Burgers equation under event-triggering mechanism

This article studies a composite disturbance rejection control strategy containing disturbance-observer-based control (DOBC) and H∞ control for a Korteweg-de Vries-Burgers (KdVB) equation under the point measurements. Here two types of disturbances are considered: one is described by an exogenous system, and the other is an external disturbance in the L2-sense. To significantly reduce the transmitted measurements, an event-triggering mechanism (ETM) is utilized. In the framework of networked control system, quantization and communication delay of the measured signals are also taken into account. Sufficient regional exponential stability conditions are established by linear matrix inequalities (LMIs). The effectiveness of the proposed control law is verified by simulation results.

Error feedback regulation for 1D anti-stable wave equation

This paper is concerned with the boundary error feedback regulation for a one-dimensional anti-stable wave equation with distributed disturbance generated by a finite-dimensional exogenous system. Transport equation and regulator equation are introduced first to deal with the anti-damping on boundary and the distributed disturbance of the original system. Then, the tracking error and its derivative are measured to design an observer for both exosystem and auxiliary partial differential equation (PDE) system to recover the state. After proving the well-posedness of the regulator equations, we propose an observer-based controller to regulate the tracking error to zero exponentially and keep the states of all the internal loop uniformly bounded. Finally, some numerical simulations are presented to validate the effectiveness of the proposed controller.

Cooperative tracking control of single-integrator multi-agent systems with multiple leaders

In this paper, the cooperative tracking control of single-integrator multi-agent systems is investigated. The networked agents are partitioned into two groups, leaders and followers. Only the former have access to the state of an autonomous exogenous system and their role is to inject the control inputs into the network such that the followers track the predefined setpoint trajectories. The followers are controlled through local interaction rules based on the relative measurements from their neighbors. A novel distributed observer-based control strategy that solves the tracking control problem is proposed. Simple rules are provided for determining the controller and observer parameters which guarantee that the closed-loop system poles lie in the specified region. The effectiveness of the proposed approach is verified through numerical examples.

Adaptive tracking control of switched cyber-physical systems with cyberattacks

This study investigates the problem of adaptive tracking control for switched cyber-physical systems against cyberattacks. A tracking signal is generated using an exogenous system. An adaptive tracking controller is designed to compensate for the attacks and then stabilize the studied systems. A switching signal is constructed using the mode-dependent average dwell time (MDADT) method. By using the multiple Lyapunov function approach, which is associated with the adaptive estimated signal, the closed-loop error systems with cyberattacks are asymptotically stable under the designed adaptive tracking controller and MDADT switching signal, and the system states can asymptotically track the reference signal. Finally, two examples are provided to validate the theoretical results.

Fixed-time sliding mode output tracking control for second-order switched systems with power integrators

The issue of fixed-time sliding mode output tracking control is addressed for second-order switched systems, where the tracking reference signal is defined by a power-integrator exogenous system. A novel non-singular terminal sliding mode surface is constructed, in which a reference is introduced into the sliding mode surface. Subsequently, an explicit novel fixed-time output tracking control scheme is constructively developed to drive the tracking error into a small neighborhood of the origin in fixed-time. Some sufficient criteria are developed to guarantee that the switched systems track the reference signal in fixed-time. Finally, a numerical example and an application example of an electro-hydraulic system are provided to demonstrate the validity of the proposed method.

Nonlinear exogeneous system and internal model design

Nonlinear exogeneous system and internal model design

HepGentox: a novel promising HepG2 reportergene-assay for the detection of genotoxic substances in complex mixtures.

BackgroundIn risk assessment, genotoxicity is a key factor to determine the safety for the consumer. Most in vitro genotoxicity assays were developed for the assessment of pure substances. However, in recent years more attention has been given to complex mixtures, where usually low amounts of a substance are present. For high-throughput screening, a toxicologically sensitive assay should be used, covering a broad range of genotoxic substances and detecting them at low concentrations. HepG2 cells have been recommended as one of the prime candidates for genotoxicity testing, as they are p53 competent, less prone towards cytotoxic effects and tend to have some metabolic activity.MethodsA HepG2 liver cell line was characterized for its suitability for genotoxicity assessment. For this, a luciferase based reporter gene assay revolving around the p53 pathway was validated for the analysis of pure substances and of complex mixtures. Further, the cell’s capability to detect genotoxins correctly with and without an exogenous metabolizing system, namely rat liver S9, was assessed.ResultsThe assay proved to have a high toxicological sensitivity (87.5%) and specificity (94%). Further, the endogenous metabolizing system of the HepG2 cells was able to detect some genotoxins, which are known to depend on an enzymatic system. When complex mixtures were added this did not lead to any adverse effects concerning the assays performance and cytotoxicity was not an issue.DiscussionThe HepGentox proved to have a high toxicological sensitivity and specificity for the tested substances, with similar or even lower lowest effective concentration (LEC) values, compared to other regulatory mammalian assays. This combines some important aspects in one test system, while also being less time and material consuming and covering several genotoxicity endpoints. As the assay performs well with and without an exogenous metabolizing system, no animal liver fractions have to be used, which application is discussed controversially and is considered to be expensive and laborious in sample testing. Because of this, the HepGentox is suitable for a cost-efficient first screening approach to obtain important information with human cells for further approaches, with a relatively fast and easy method. Therefore, the HepGentox is a promising assay to detect genotoxic substances correctly in complex mixtures even at low concentrations, with the potential for a high throughput application. In a nutshell, as part of an in vitro bioassay test battery, this assay could provide valuable information for complex mixtures.

Fuzzy Adaptive Observer-Based Fault and Disturbance Reconstructions for T-S Fuzzy Systems

This brief focuses on the observer-based state, fault and disturbance reconstructions for Takagi-Sugeno (T-S) fuzzy-approximation-based nonlinear dynamics subject to an enlarged class of disturbances and abrupt actuator fault. By developing a brand-new fuzzy adaptive observer (FAO), unknown system state, fault and disturbance can be reconstructed simultaneously, where some classic assumptions imposed on the disturbance such as the first-order derivative being equal to zero or generation from an exogenous system are removed successfully in our work. Significantly, to reduce the conservatism, the stability criterion of error dynamic is inferred in terms of using fuzzy Lyapunov functions, and expressed in a linear matrix inequality (LMI) framework. At last, simulation study on a real plant is provided to illustrate the practicability of the given procedure.

Abstract 1151: Targeting castration-resistant prostate cancer using mesenchymal stem cell exosomes for therapeutic microRNA let-7c delivery

Abstract Introduction: Castration-resistant prostate cancer (CRPC) has poor response to androgen deprivation therapy, which is caused by a sustained androgen receptor (AR) signal and therefore is considered as an incurable disease. MicroRNA let-7c has been implied as a tumor suppressor in prostate cancer by antagonizing AR expression and activity. In addition to cancer cells, our group previously also demonstrated that downregulation of let-7c by cancer-associated mesenchymal stem cells (MSCs) triggering a reactive stromal response to facilitate prostate cancer growth and metastasis (PLoS ONE 8(8): e71637). Accordingly, treatment with exogenous let-7c would target both cancer cells and their associated MSCs and could be an attractive therapeutic approach to effectively inhibit CRPC recurrence and prevent metastasis. Exosomes are nanometer-sized membrane-bound vesicles with functions as mediators of cell-cell communication, which have the absolute predominance in biocompatibility for clinical applications in drug delivery and gene therapy. Objective: By taking the intrinsic tumor-targeting property of MSCs, this study aimed to investigate the feasibility of using MSC-derived exosomes as an exogenous let-7c delivery system to target CRPC. Methods: Relative miRNA-let-7c expression across various prostate cancer cell lines was examined using q-RT PCR. MSC-derived exosomes were collected from a 3A6 human bone marrow-derived MSC cell line after cell transfection with pre-miR negative control and pre-miR-let-7c, and further characterized through transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blot. The effects of either naked or MSC-exosome encapsulated let-7c on CRPC cells was determined by WST-1 cell proliferation assay and wound healing migration assay. Results: MiRNA-let-7c expression was confirmed to be downregulated in most of CRPC-like cell lines compared with androgen-sensitive LNCaP. Overexpression of pre-miR-let-7 inhibited the ability of cell proliferation and migration of prostate cancer cells. Exogenous microRNAs can be successfully packaged into MSC-exosomes by cell transfection, without a disruption of exosome integrity. Treatment of CRPC-like PC3 (AR-negative) and CWR22r-v1 (AR-positive) cells with MSC-exosome encapsulated let-7c effectively delivered let-7c into cells and resulted in a significant reduction in cancer cell growth and metastasis in vitro. Conclusion: Herein, we have provided in vitro evidences to prove the concept that microRNA let-7c is a potential therapeutic intervention for CRPC, as well as MSC-derived exosomes can serve as a therapeutic let-7c delivery system to target the CRPC. Further in vivo validation of distribution and therapeutic efficacy of MSC-exosome-delivered let-7c in CRPC xenograft mouse model is currently being explored. Citation Format: Ida Kurniawati, Chia-Yen Hsueh, Shian-Ying Sung, Chia-Ling Hsieh. Targeting castration-resistant prostate cancer using mesenchymal stem cell exosomes for therapeutic microRNA let-7c delivery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1151.