Dual Rate Control for Security in Cyber-physical Systems

We consider malicious attacks on actuators and sensors of a feedback system which can be modeled as additive, possibly unbounded, disturbances at the digital (cyber) part of the feedback loop. We precisely characterize the role of the unstable poles and zeros of the system in the ability to detect stealthy attacks in the context of the sampled data implementation of the controller in feedback with the continuous (physical) plant. We show that, if there is a single sensor that is guaranteed to be secure and the plant is observable from that sensor, then there exist a class of multirate sampled data controllers that ensure that all attacks remain detectable. These dual rate controllers are sampling the output faster than the zero order hold rate that operates on the control input and as such, they can even provide better nominal performance than single rate, at the price of higher sampling of the continuous output

Petri Net Based Reliable Work Flow Framework for Nephrology Unit in Hospital Environment

The 21st century has witnessed a revolution in Biology and Medicine that has radically changed the way health, diagnosis, prognosis, etc., of a disease is monitored nowadays. Accordingly, hospital redesign, workforce planning and scheduling, patient flow, performance management, disease monitoring, and health care technology assessment need to be modeled efficiently. Mathematical modeling and computer simulation techniques have been shown to be increasingly valuable in providing useful information to aid planning and management. Petri Net (PN) is considered as a powerful model since it combines well-defined mathematical theory with a graphical representation which reflects the dynamic behavior of systems of interest. Due to dynamic characteristics, it is found to be more suitable for modeling Hospital Management System (HMS). In this paper, a Petri net model-based reliable workflow framework for Nephrology unit in hospital environment is proposed to track the movement of patients in the unit. The key objective of the proposed reliable workflow framework is to provide a well-organized health care unit to reduce the waiting time of the resource/ patient. The performance of the proposed Petri net model-based reliable workflow framework is simulated and validated through reachability graph using HPSim tool. The proposed Petri net workflow framework for the Nephrology unit can be used to deliver highly efficient and reliable healthcare services

Modeling, control and simulation of control-affine nonlinear systems with state-dependent transfer functions

There has been no known research that applies nonlinear transfer function to a nonlinear control problem. The belief is that nonlinear systems have no transfer functions. The Laplace transformation required to define transfer functions is not tractable mathematically when the coefficients of the differential equation are functions of state, output and control variables. In other words, it is not defined for systems that do not obey principles of superposition. Only linear systems obey this principle. Therefore, this dissertation work represents the very first research to demonstrate how transfer functions can be used to represent and design feedback control for nonlinear systems. Real systems are inherently nonlinear. A few important examples include an aerospace vehicle whose mass parameter is variable because of fuel consumption, artificial pancreas and HIV drug delivery systems in the bio-medical field, robot arm and magnetic levitation systems in the mechanical engineering field and phase-locked-loop in the electrical engineering field. The subject of nonlinear system control, however, is more of an art than science. There is no unified framework for analysis and design. Success of a design usually depends on a designer’s experience. All the theory and design tools available, e.g., the whole subject of linear algebra, are based on systems described with linear models, which obey the principle of superposition. Control system design by linearization, which is based on approximated linear time invariant (LTI) system design model, is the closest to a general design framework available for nonlinear systems. The most important problem in a control system designed by linearization is the problem of design model parameter variation during its operation. Obviously, this problem is the result of assuming a constant parameter or LTI design model for a real system that is actually nonlinear or has variable parameter model. In other words, a real system does not have constant parameters as approximated by its LTI design model. This problem is important enough to have specific design methods such as robust control and Horowitz quantitative feedback theory developed to address it. As the system is operated further and further out of the approximate linear range this problem gets worst. Furthermore, the controller based on design by linearization is not a tracking controller. It is a regulator that usually cannot track a varying reference input. Investigated in the research presented in this dissertation is a nonlinear transfer function-based control method, i.e., one based on a model represented with varying parameters therefore a natural solution to the model parameter variation problem of design by linearization. The class of applicable nonlinear and time-varying systems are those that are affine in their control input such that they can be described by the central concept of this scheme, a state-dependent transfer function (SDTF). The introduction of this concept of nonlinear transfer function design model and the feedback control scheme based on it are the contributions of the research presented in this dissertation

Fault simulator for proportional solenoid valves

Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults.Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved. The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability. Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults. Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved.The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability

Fault Diagnosis and Failure Prognostics of Lithium-ion Battery based on Least Squares Support Vector Machine and Memory Particle Filter Framework

123456A novel data driven approach is developed for fault diagnosis and remaining useful life (RUL) prognostics for lithium-ion batteries using Least Square Support Vector Machine (LS-SVM) and Memory-Particle Filter (M-PF). Unlike traditional data-driven models for capacity fault diagnosis and failure prognosis, which require multidimensional physical characteristics, the proposed algorithm uses only two variables: Energy Efficiency (EE), and Work Temperature. The aim of this novel framework is to improve the accuracy of incipient and abrupt faults diagnosis and failure prognosis. First, the LSSVM is used to generate residual signal based on capacity fade trends of the Li-ion batteries. Second, adaptive threshold model is developed based on several factors including input, output model error, disturbance, and drift parameter. The adaptive threshold is used to tackle the shortcoming of a fixed threshold. Third, the M-PF is proposed as the new method for failure prognostic to determine Remaining Useful Life (RUL). The M-PF is based on the assumption of the availability of real-time observation and historical data, where the historical failure data can be used instead of the physical failure model within the particle filter. The feasibility of the framework is validated using Li-ion battery prognostic data obtained from the National Aeronautic and Space Administration (NASA) Ames Prognostic Center of Excellence (PCoE). The experimental results show the following: (1) fewer data dimensions for the input data are required compared to traditional empirical models; (2) the proposed diagnostic approach provides an effective way of diagnosing Li-ion battery fault; (3) the proposed prognostic approach can predict the RUL of Li-ion batteries with small error, and has high prediction accuracy; and, (4) the proposed prognostic approach shows that historical failure data can be used instead of a physical failure model in the particle filter

Analysis of the quadrant error compensation possibilities at CNC machine tools

katedra: RSS; přílohy: 1x CD; rozsah: 67 s.Práce se zaměřuje na zmapování problematiky kvadrantových chyb, vznikajících vlivem pasivních odporů při kruhové interpolaci. V první kapitole jsou objasněny příčiny vzniku chyb a je naznačen výčet několika možných řešení, jak tyto chyby kompenzovat. Za tímto účelem je v další kapitole popsáno vytvoření počítačového modelu posuvových os frézovacího centra, pro počítačovou simulaci kruhové interpolace. V modelu jsou následně otestovány vybrané způsoby kompenzace dodatečnými předkorekčními signály. Cílem práce je zhodnotit a porovnat vhodné kompenzační metody na základě proběhlých simulací.The thesis focuses on mapping issues of quadrant errors due to the influence of friction in circular interpolation. The first chapter explained the causes of errors and outlined a list of several options to compensate these errors. To this end, the next chapter describes a computerized model of feeding axis of milling center for computer simulation of circular interpolation. The model is then tested by means of selected additional compensation by pre-correction signals. The aim is to evaluate and compare the appropriate compensation method on the basis of past simulations

Abordagem modular aplicada a projeto de pêndulo invertido sobre duas rodas

Orientadores: Eric Fujiwara, Ely Carneiro de PaivaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: Este trabalho propõe a exploração de uma abordagem modular para projeto de pêndulo invertido sobre rodas. Através da escolha apropriada de estruturas de controle, o método permite o desacoplamento de variáveis chave para simplificar o projeto e adicionar benefícios inerentes à modularização. Seguindo os procedimentos propostos, duas plantas virtuais foram simuladas em diferentes contextos e com múltiplos objetivos, como controles de velocidade linear, posição e rastreamento de um alvo. Os resultados demonstraram que o desacoplamento foi efetivo, obedecendo a proposta de baixos níveis de erro para os módulos mais internos com valores máximos menores que 5\% em transientes bruscos. Uma abordagem adaptativa foi proposta e implementada com o objetivo de permitir um desacoplamento mais apropriado entre as variáveis controladas, bem como entre os projetos dos controladores e da planta mecânica. Utilizando controles adaptativos via modelo de referência e via identificação de parâmetros, foi possível realizar o projeto independente de cada malha de controle, com o desempenho de cada componente verificado em simulaçõesAbstract: The following work proposes the evaluation of a modular approach for two-wheeled inverted pendulum design. By properly choosing control loop structures, the method allows for decoupling key variables in order to simplify the project and add inherent benefits from modular systems. By following the proposed approach, two virtual plants were simulated for different contexts with multiple objectives, such as linear velocity control, position control and target following. Results shown effective decoupling, obeying the proposed low error levels for inner modules, with peak values within 5\% for fast transients. An adaptive approach was proposed and implemented aiming to allow for a more appropriate decoupling between the decoupled variables, as well as between the control and the mechanical structure designs. By applying model reference and parameters identification control structures, the independent design of each control loop was made possible. The performance of each component was verified through simulationsMestradoMecatrônicaMestre em Engenharia Mecânica33003017CAPE