Roy Abi Zeid Daou

Effect of Hydropneumatic Components Nonlinearities on the CRONE Suspension

This paper presents a fractional system composed of a sprung mass and a suspension device with fractional impedance (fractance for short). More precisely, this fractance is a fractional integrator. Practical realizations of this fractional integrator based on hydropneumatic RC cells are presented in a limited frequency band. The main objective of this paper is to analyze the influence of the hydropneumatic RC cell nonlinearities, which constitute the hydropneumatic networks of the CRONE suspension, on the stability degree robustness when varying the sprung mass. First, the achievement of a nonlinear validation model is emphasized, and then, a linear synthesis model is presented. These two models are used in the second part of this paper to analyze the obtained performances and to show the influence of the nonlinearities. This analysis of performances is made first from a qualitative standpoint using the functional domain of each Ri and Ci element and then from the quantitative standpoint using the Volterra series. In fact, the difference between the response of the nonlinear model and the one of the first-order kernel (which represents the linear response of the system) allows the determination of the influence of the nonlinearities on the dynamic behavior for a particular signal input. The results obtained show that the RC cell nonlinearities composing the hydropneumatic networks of the CRONE suspension do not modify the stability degree robustness versus sprung mass variations, thus extending in a nonlinear context this robustness that is present in the linear context.

Study of the effects of structural uncertainties on a fractional system of the first kind – application in vibration isolation with the CRONE suspension

In this paper, we deal with the effects of the uncertainties on a fractional system of the first kind, mainly on the frequency-domain and the time-domain responses. For the structural uncertainties, two main aspects are studied: the nonlinearities of the physical components used to realize the fractional system and the consideration of the previously neglected dynamics of the system. Both uncertainties are introduced for the hydropneumatic CRONE suspension, previously synthesized and realized without taking into consideration these uncertainties. So, the novel approach treated in this work is to find whether the uncertainties, which were previously neglected in the synthesis and the realization phases, alter the behaviour of the system or not. The results show that the fractional order system behaviour is not affected.

Analysis of the fractional order system in the thermal diffusive interface - Part 1: Application to a semi-infinite plane medium

The recognition of fractional order behavior when identifying physical systems is relatively new. One of these fields where the fractional order integration can show up is the thermal diffusive interfaces. In fact, for some special conditions, an integration of order 0.5 appears when identifying the system. So, the objective of this work, divided into two parts, is to study the presence and the effects of the fractional order on the system behavior, and to determine the relation between the applied flux, the conduction and the point of measurement of the temperature. Accordingly, this first part will treat the case of homogeneous semi-infinite aluminum bar. Results show that the fractional order behavior of the bar disappears whenever the temperature sensor is far from the boundary where the flux is applied.

CONTROL OF HYDRO-ELECTROMECHANICAL SYSTEM USING THE GENERALIZED PID AND THE CRONE CONTROLLERS

This article deals with a comparative study between two fractional controllers: the generalized PID and the CRONE. A frequency-domain design methodology is developed to compare the two controllers. So the performance specifications are firstly translated into open-loop constraints (used for the CRONE controller), and then translated into controller constraints (used for the generalized PID controller). A method with two steps is proposed to determine the optimal parameters of the generalized PID controller. This frequency-domain design methodology is applied to a nonlinear hydro-electromechanical plant. From a grey-box approach, the modelling of the plant is presented, showing a nonlinear behaviour which is discussed around three operating points considered as reference input for the control loop. Then, a linear uncertain model is deduced in order to design the two controllers. Finally, results obtained in simulation and with the test bench are presented.

Patient vital signs monitoring via android application

This paper presents a system that is able to monitor the patient vital signs (Heart Rate, SPO2, NIBP, ECG, temperature and respiration rate) and send them continuously to the doctors android phone device. The system enables multiple patients to be connected to the same doctor. Within the system, the health care professional may activate/deactivate any of the vital signs sensors. He can also set a prescription for the patient, schedule a meeting,... When bad activities are received, a message is directly sent to the doctor and to the patient relatives in order to alert them. Note that the Bluetooth connection is used to send/receive data between the patient platform and its android system. The tested results showed an almost error free system with an accuracy above 95% and a few milliseconds delay between the vital signs reading and their upload over the server.

Approximation of a thermal diffusive interface fractional-order system — Part 1: Application to a semi-infinite plane

The fractional differentiation and integration exist in natural phenomena or can be artificially introduced into other domains. Concerning the thermal diffusive interface, the fractional expression is emphasized when taking the applied flux as input for the system and the measured temperature at any point as an output. However, the main problem when facing such systems is to pass from the frequency domain to the time domain in order to estimate the response of the system at any point for any input at any instance. So, the aim of this work is to present a method to approximate the fractional system that models the semi-infinite plane medium. The second part of this work presents the approximation of a finite plane medium. The results show that the approximation leads to very good behaviour.

Temperature control of a diffusive medium using the second generation CRONE control

This paper presents the design of the temperature control of a diffusive medium by using a unique robust controller for three different materials: aluminum, copper and iron. For the control-system design, the aluminum is selected as the material defining the nominal model. Then, the second generation CRONE control is used because the parametric uncertainty (due to the copper and the iron) leads to variations of open-loop gain. Finally, the responses in frequency-domain and in time-domain have been illustrated at the position of the actuator to show the stability degree robustness.

Fractional order systems in the electrical domain - Part 2: Implementation results and uncertainties influence

This second part follows a first part where a background study and the implementation process of fractional order systems were presented. In this part, the results of the test bench are shown. Some uncertainties, related mainly to the parametric effects, as the components tolerance, are also presented in order to study the stability and the robustness of the system toward these variations. The results show that this fractional order system behavior is almost unchanged even when introducing these variations whereas the integer order system is affected by these uncertainties. As for the robustness, the fractional order system is robust but the integer order system does not present any robustness when varying the unit gain frequency.

Free and forced modes responses of fractional operators based on non-identical RLC cells

In this article, we study the behaviour of the RLC cells for the four configurations that we presented earlier in Abi Zeid Daou et al. (2009a). An electric circuit is used in order to study the fractional behaviour and the robustness of these RLC operators and compare their responses to the behaviour of the fractance which is an ideal fractional operator (Moreau et al., 2003). This analysis is conducted for both natural and forced responses. In more details, the initial conditions of the capacitors and inductances are neglected in the first case and they are taken into consideration in the second one. The number of initial conditions is related to the number of RLC cells used. The robustness of all arrangements is analysed by varying the unsteady parameter value which is represented by an inductance in the electrical circuit. This inductance represents a different variable parameter in each field of application. For example, in the hydropneumatic domain, this inductance refers to the mass of the vehicle as the mass has the main influence on the dynamics and the robustness when designing the active suspension (Moreau et al., 2001). A conclusion will sum up the results for all four arrangements and a confirmation that the phase constancy and the robustness are present in both modes.

Behavior and robustness study of fractional controllers based on RLC cells

In this article, we will study the behavior of the RLC cells for the four configurations that we have presented in [1]. We will propose an electric circuit that will be used to study the fractional behavior and robustness of these RLC operators and compare their responses to the behavior of the fractance which is an ideal fractional operator [2]. This analysis will be studied for both natural and forced responses. In more details, we will neglect the initial conditions of the capacitors and inductances in the first case and we will take them into consideration in the second one. The number of initial conditions will be related to the number of RLC cells used. For example, if we are using 10 RLC cells, we will have 21 initial conditions (as we have 11 conductors and 10 inductances). Also, the robustness of all arrangements will be analyzed when varying the unsteady parameter value of the same system used to study the fractional behavior. The non-steady parameter will be represented by an inductance in the electrical circuit. This inductance represents a different variable parameter in each field of application. For example, in the hydropneumatic domain, this inductance refers to the mass of the vehicle as the mass has the main influence on the speed and robustness when using the suspension. A conclusion will sum up the results for all four arrangements and show that the phase constancy and robustness are preset for both modes.