2021 IEEE Industry Applications Society Annual Meeting (IAS), Oct 10, 2021
This paper investigates the issue of frequency regulation of a single-area alternating current (A... more This paper investigates the issue of frequency regulation of a single-area alternating current (AC) power system connected to an electric vehicle (EV) aggregator through a nonideal communication network. It is assumed that the command control action is received by the EV aggregator with constant delay and the power system experiences uncertain parameters. A novel effective iterative algorithm, direct search, is proposed for the time-delayed system to design the gains of a proportional-integral (PI) controller. The proposed direct search algorithm can find a feasible solution whenever at least one solution lays in the space search. Thus, by choosing a wide space search, we can expect that the PI controller assures the closed-loop stability, theoretically. The proposed approach has low conservative results over the existing approaches. For the uncertain time-delayed system, a robust PI controller is designed, which is resilient against the system uncertainties and time delay. Numerical simulations are carried out to show the merits of the developed controller.
In recent years, heart transplantation has been considered a suitable method for heart failure (H... more In recent years, heart transplantation has been considered a suitable method for heart failure (HF), a significant cardiovascular disease. Heart failure often means chronic heart failure or congestive heart failure. In this case, the heart is unable to pump enough blood to the vital organs. Usually, heart failure occurs on the left side of the heart that pumps blood throughout the body. No one can ever deny the impact of a left ventricular assist device (LVAD) as a bridge for recovery in the patient’s treatment process with congestive heart failure. In this paper, we aim to control the LVAD flow and the goal is to return the person to everyday life by using this assist device and control it perfectly. Since heart failure could occur if the pump speed is lower or higher than some thresholds, to prevent heart failure, the controller should provide an appropriate pump speed. This paper prohibits these ranges by designing a suitable controller that can track the flow of healthy heart behavior through a Frank-Starling-Like controller. The controller performance is evaluated by a simulated model of the heart and the results are satisfactory.
International Journal of Dynamics and Control, Jul 24, 2021
This paper deals with the stability analysis problem of continuous linear parameter varying (LPV)... more This paper deals with the stability analysis problem of continuous linear parameter varying (LPV) systems. The basic form of LPV systems are addressed in this paper and valuable results are proposed concerning the boundedness and stability concepts of these systems. A set of conditions are developed to explore the boundedness of LPV system based on some inherent properties of these systems. Then, the global stability problem of LPV systems is separately investigated based on the boundedness of the system. It has been mathematically proven that the stability conditions of LPV systems can be basically relaxed through the boundedness assumption. It has been shown the Lyapunov matrix of parameter dependent Lyapunov functions is not needed to be positive that surely reduces the conservativeness of the stability conditions. Finally, two illustrating examples are presented to explain all aspects of the results.
Biomedical Signal Processing and Control, Sep 1, 2021
Current outbreaks of the COIVD-19 pandemic demonstrate a global threat. In this paper, a conceptu... more Current outbreaks of the COIVD-19 pandemic demonstrate a global threat. In this paper, a conceptual model is developed for the COVID-19 pandemic, in which the people in society are divided into Susceptible, Exposed, Minor infected (Those who need to be quarantined at home), Hospitalized (Those who are in need of hospitalization), Intensive infected (ventilator-in-need infected), Recovered and Deceased. In this paper, first, the model that is briefly called SEMHIRD for a sample country (Italy as an example) is considered. Then, exploiting the real data of the country, the parameters of the model are obtained by assuming some basis functions on the collected data and solving linear least square problems in each window of data to estimate the time-varying parameters of the model. Thus, the parameters are updated every few days, and the system behavior is modeled according to the changes in the parameters. Then, the Linear Parameter Varying (LPV) Model of COVID19 is derived, and its stability analysis is presented. In the end, the influence of different levels of social distancing and quarantine on the variation of severely infected and hospitalized people is studied.
Hydrostatic Transmission system (HST), is extensively used in mobile working machines, off-road v... more Hydrostatic Transmission system (HST), is extensively used in mobile working machines, off-road vehicles, agricultural and construction machines such as loaders and tractors. In this system, important parameters such as hydromotor and hydropump speeds and their angles, and also pressure difference are constantly changing with time. Therefore, the issue of regulation and control of these parameters has become an important issue among researchers in this field. In this paper, first, the nonlinear system model is converted to polytopic LPV form and then a linear parameter varying feedback controller based on Lyapunov method is designed using LMI techniques. Finally, after finding the appropriate feedback controller gain, the controller is applied on the nonlinear system. The simulation results show the effectiveness of this proposed method in controlling system states.
This paper studies the robust stability of the fractional-order (FO) LTI systems with polytopic u... more This paper studies the robust stability of the fractional-order (FO) LTI systems with polytopic uncertainty. Generally, the characteristic polynomial of the system dynamic matrix is not an affine function of the uncertain parameters. Consequently, the robust stability of the uncertain system cannot be evaluated by well-known approaches including LMIs or exposed edges theorem. Here, an over-parameterization technique is developed to convert the main characteristic polynomial into a set of local over-parameterized characteristic polynomials (LOPCPs). It is proved that the robust stability of LOPCPs implies the robust stability of the uncertain system. Then, an algorithm is proposed to explore system's robust stability through investigating the robust stability of these LOPCPs based on the exposed edges idea. For the sake of feasibility comparison, extensive examples are elaborated that reveal the superiority of the proposed algorithm.
This paper deals with the problem of determining the exact value of the maximum allowable upper b... more This paper deals with the problem of determining the exact value of the maximum allowable upper bound (MAUB) of delay of an LTI system in the presence of the delay parameters. The delay parameter is supposed to be time-invariant, and this paper proposes a systematic method to exactly solve the mentioned problem. For this purpose, a modified system matrix is defined based on the delay system’s model that involves an extra complex variable on the boundary of the unit circle. It will be shown that the characteristic polynomial of the modified system can equivalently assess the system’s stability. The characteristic polynomial of the modified system is a quadratic function of the imaginary part of the extra complex variable which enables us to rewrite the polynomial based on only the real part of the extra variable. This property is exploited to develop an explicit formula to find the MAUB based on the critical numbers (complex numbers that force the modified characteristic polynomial to have pure imaginary roots) and their related pure imaginary roots. The method is tested for some sample delay systems and the results demonstrate a tighter bound for the MAUB of the systems.
The figure contains the detailed simplexes in the design space of the microgrid.<br>The fol... more The figure contains the detailed simplexes in the design space of the microgrid.<br>The following is the link to the source codes of direct search algorithm used in this paper.https://github.com/Roozbeh-Abolpour/Direct-Searching-Design-Controller
2021 IEEE Industry Applications Society Annual Meeting (IAS), Oct 10, 2021
This paper investigates the issue of frequency regulation of a single-area alternating current (A... more This paper investigates the issue of frequency regulation of a single-area alternating current (AC) power system connected to an electric vehicle (EV) aggregator through a nonideal communication network. It is assumed that the command control action is received by the EV aggregator with constant delay and the power system experiences uncertain parameters. A novel effective iterative algorithm, direct search, is proposed for the time-delayed system to design the gains of a proportional-integral (PI) controller. The proposed direct search algorithm can find a feasible solution whenever at least one solution lays in the space search. Thus, by choosing a wide space search, we can expect that the PI controller assures the closed-loop stability, theoretically. The proposed approach has low conservative results over the existing approaches. For the uncertain time-delayed system, a robust PI controller is designed, which is resilient against the system uncertainties and time delay. Numerical simulations are carried out to show the merits of the developed controller.
In recent years, heart transplantation has been considered a suitable method for heart failure (H... more In recent years, heart transplantation has been considered a suitable method for heart failure (HF), a significant cardiovascular disease. Heart failure often means chronic heart failure or congestive heart failure. In this case, the heart is unable to pump enough blood to the vital organs. Usually, heart failure occurs on the left side of the heart that pumps blood throughout the body. No one can ever deny the impact of a left ventricular assist device (LVAD) as a bridge for recovery in the patient’s treatment process with congestive heart failure. In this paper, we aim to control the LVAD flow and the goal is to return the person to everyday life by using this assist device and control it perfectly. Since heart failure could occur if the pump speed is lower or higher than some thresholds, to prevent heart failure, the controller should provide an appropriate pump speed. This paper prohibits these ranges by designing a suitable controller that can track the flow of healthy heart behavior through a Frank-Starling-Like controller. The controller performance is evaluated by a simulated model of the heart and the results are satisfactory.
International Journal of Dynamics and Control, Jul 24, 2021
This paper deals with the stability analysis problem of continuous linear parameter varying (LPV)... more This paper deals with the stability analysis problem of continuous linear parameter varying (LPV) systems. The basic form of LPV systems are addressed in this paper and valuable results are proposed concerning the boundedness and stability concepts of these systems. A set of conditions are developed to explore the boundedness of LPV system based on some inherent properties of these systems. Then, the global stability problem of LPV systems is separately investigated based on the boundedness of the system. It has been mathematically proven that the stability conditions of LPV systems can be basically relaxed through the boundedness assumption. It has been shown the Lyapunov matrix of parameter dependent Lyapunov functions is not needed to be positive that surely reduces the conservativeness of the stability conditions. Finally, two illustrating examples are presented to explain all aspects of the results.
Biomedical Signal Processing and Control, Sep 1, 2021
Current outbreaks of the COIVD-19 pandemic demonstrate a global threat. In this paper, a conceptu... more Current outbreaks of the COIVD-19 pandemic demonstrate a global threat. In this paper, a conceptual model is developed for the COVID-19 pandemic, in which the people in society are divided into Susceptible, Exposed, Minor infected (Those who need to be quarantined at home), Hospitalized (Those who are in need of hospitalization), Intensive infected (ventilator-in-need infected), Recovered and Deceased. In this paper, first, the model that is briefly called SEMHIRD for a sample country (Italy as an example) is considered. Then, exploiting the real data of the country, the parameters of the model are obtained by assuming some basis functions on the collected data and solving linear least square problems in each window of data to estimate the time-varying parameters of the model. Thus, the parameters are updated every few days, and the system behavior is modeled according to the changes in the parameters. Then, the Linear Parameter Varying (LPV) Model of COVID19 is derived, and its stability analysis is presented. In the end, the influence of different levels of social distancing and quarantine on the variation of severely infected and hospitalized people is studied.
Hydrostatic Transmission system (HST), is extensively used in mobile working machines, off-road v... more Hydrostatic Transmission system (HST), is extensively used in mobile working machines, off-road vehicles, agricultural and construction machines such as loaders and tractors. In this system, important parameters such as hydromotor and hydropump speeds and their angles, and also pressure difference are constantly changing with time. Therefore, the issue of regulation and control of these parameters has become an important issue among researchers in this field. In this paper, first, the nonlinear system model is converted to polytopic LPV form and then a linear parameter varying feedback controller based on Lyapunov method is designed using LMI techniques. Finally, after finding the appropriate feedback controller gain, the controller is applied on the nonlinear system. The simulation results show the effectiveness of this proposed method in controlling system states.
This paper studies the robust stability of the fractional-order (FO) LTI systems with polytopic u... more This paper studies the robust stability of the fractional-order (FO) LTI systems with polytopic uncertainty. Generally, the characteristic polynomial of the system dynamic matrix is not an affine function of the uncertain parameters. Consequently, the robust stability of the uncertain system cannot be evaluated by well-known approaches including LMIs or exposed edges theorem. Here, an over-parameterization technique is developed to convert the main characteristic polynomial into a set of local over-parameterized characteristic polynomials (LOPCPs). It is proved that the robust stability of LOPCPs implies the robust stability of the uncertain system. Then, an algorithm is proposed to explore system's robust stability through investigating the robust stability of these LOPCPs based on the exposed edges idea. For the sake of feasibility comparison, extensive examples are elaborated that reveal the superiority of the proposed algorithm.
This paper deals with the problem of determining the exact value of the maximum allowable upper b... more This paper deals with the problem of determining the exact value of the maximum allowable upper bound (MAUB) of delay of an LTI system in the presence of the delay parameters. The delay parameter is supposed to be time-invariant, and this paper proposes a systematic method to exactly solve the mentioned problem. For this purpose, a modified system matrix is defined based on the delay system’s model that involves an extra complex variable on the boundary of the unit circle. It will be shown that the characteristic polynomial of the modified system can equivalently assess the system’s stability. The characteristic polynomial of the modified system is a quadratic function of the imaginary part of the extra complex variable which enables us to rewrite the polynomial based on only the real part of the extra variable. This property is exploited to develop an explicit formula to find the MAUB based on the critical numbers (complex numbers that force the modified characteristic polynomial to have pure imaginary roots) and their related pure imaginary roots. The method is tested for some sample delay systems and the results demonstrate a tighter bound for the MAUB of the systems.
The figure contains the detailed simplexes in the design space of the microgrid.<br>The fol... more The figure contains the detailed simplexes in the design space of the microgrid.<br>The following is the link to the source codes of direct search algorithm used in this paper.https://github.com/Roozbeh-Abolpour/Direct-Searching-Design-Controller
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