INFLUENCE OF UNCERTAINTIES ON ROTATING FLEXIBLE SHAFT SUSPENDED BY 4-AXIS RADIAL ACTIVE MAGNETIC BEARINGS \ub5-SYNTHESIS AND LOOP-SHAPING-DESIGN

This paper shows a comparison about dynamic behavior of a rotating shaft when it is suspended by 4-axis radial active magnetic bearing system. The active magnetic suspension is obtained by two different controllers which realize the robust stability and robust performance. The control systems used are \ub5-synthesis and loop shaping design procedure. Each of these controllers is characterized by fourinput and four output signals and the introduction of uncertainties on displacement gain and current gain is justified by the simple fact that during the time the component which constitutes these gains can be subjected to torn and worn which can lead the entire system to instability phenomena. The inputs are the feedbacks of four displacement components relative to the four axis of radial active magnetic bearing while the outputs are the control current injected in the plant in order to provide the control of position of two section under the monitoring of ideal sensors. An ideal sensor here is meant to be able to capture small displacements and without presence of noise. The advantages of a four input controller is the absence of velocity components which are present in the state vector such that no observer and speedsensors are need to build a feedback. The comparison of the performances is made through the introduction of same weighting function for the two control system. The weighting functions are introduced in order to define the required performances for the position and control signals. The results are produced by simulations tracking of reference and disturbance rejection are tested in order to provide elements useful to implement the goal of this paper. All simulations and results are performed by MATLab

INFLUENZA SUL COMPORTAMENTO DINAMICO DI UN ROTORE SOSPESO ATTRAVERSO CUSCINETTI MAGNETICI ATTIVI MEDIANTE \u3bc-SYNTHESIS E LOOP-SHAPING DESIGN

In questo lavoro viene effettuato un confronto sul comportamento dinamico di un albero rotante quando \ue8 sospeso attraverso un sistema di due cuscinetti magnetici ciascuno costituito da due assi. Le sospensione magnetica attiva \ue8 ottenuta elaborando due diversi sistemi di controllo che realizzano la stabilit\ue0 del rotore conferendo a quest\u2019ultimo delle prestazioni robuste nel mantenimento degli spostamenti entro certi margini prestabiliti. Ognuno di questi sistemi di controllo \ue8 caratterizzato da otto ingressi e quattro uscite con la presenza di incertezze sul guadagno spostamento e guadagno di corrente; ci\uf2 \ue8 giustificato dal semplice fatto che gli apparati elettronici possono usurarsi con il continuo uso nel tempo inducendo il rotore a stati di instabilit\ue0 durante un normale funzionamento. I risultati prodotti sono mostrati attraverso le simulazioni in ambiente MATLab dove vengono testate le capacit\ue0 del rotore di eliminare il disturbo e di seguire un riferiment

STUDY OF NEW AUTOMOTIVE REAR SUSPENSION MECHANISM

The paper presents firstly an introduction discussing: the problem’s statement emphasizing the actual problem of research of passenger car suspension to improve driving comfort and dynamic of the vehicle movement; aspects regarding the studies of car suspension mechanisms; the paper’s aims and objectives showing that a new configuration of suspension mechanism having in structure mobile frame and an actuator offering some important operational advantages is proposed. After this, the innovative concept is presented. The motions of mechanism elements and actuator and kinematic displacements are largely presented. The simulation using modern software (MSC Patran 2007, MD R2 Nastran and MSC ADAMS/View) accentuates the actuality of the results, which are presented and discussed for an application. Final conclusions are given

Digital control circuitry of cancer cell and its apoptosis

This study, through a typical aerospace systems architecture, suggests an engineering design of a human cancer cell circuitry in which a digital optimal control matrix is assigned to repair the DNA damage level and/or to trigger its apoptosis. Here, the conceived machinery is proposed taking into account the state of the art in cancer investigation. However, it could be further generalized. The most recent studies on cancer pathologies give a predominant role to the oncosuppressor protein p53 and its antagonist, the oncogene Mdm2. Experimental and theoretical approaches are in agreement in deducing a “digital” response of the p53 when genomic integrity is damaged. Once DNA damage is present, the mutual influence of p53 and its antagonist, the Mdm2 oncogene, is closed in a feedback loop. In this work, starting from these current results, a novel molecular mechanism is proposed, based on a digital optimal control law, whereby p53 and Mdm2 proteins activities can be represented by appropriate circuitry and governed by the optimal control law of digital systems. This procedure obtains a real-time sequence evaluation of protein oscillations and an unexpected and relevant acceleration in the DNA repairing when suitable digital control matrix is implemented. Those effects suggest interesting perspectives for future scientific investigations. First of all, the proposed digital circuitry, receiving the p53 signal from a damaged cell, is able to repair the current level of genomic alteration. Moreover, the cell fate is newly conceived and bound by the modified pulsing mechanism of p53

Loop-Shaping Design, and Sub(H) ∞ with Uncertainties

The control systems applied on active magnetic bearing are several. A perfect levitation is characterized by maintaining the operating point condition that is characterized by the center of stator coincident with the geometric center of shaft. The first controller implemented for this purpose is PID controller that is characterized by an algorithm that leads the amplifier to produce control current until the operating point condition is not reached, this is obtained by an integration operator. The effect of an integrator is essential but not necessary for a centered levitation for example in the robust control characterized by a dynamic model depended on plant of system so that it depends on angular speed as LQR controller does. In LQR there is not integrator so there is not a perfectly centered section of shaft with center of stator. On contrary PID controller does not depend on angular speed and it can be easily implemented according some simple rules. Predictive control is another interesting controller characterized by a multiple controller operating in different condition in order to get the minimum of cost function, but also in this case the angular speed is introduce for the same reason discussed before

Digital control circuitry for the p53 dynamics in cancer cell and apoptosis

Experimental work and theoretical models deduce a "digital" response of the p53 transcription factor when genomic integrity is damaged. The mutual influence of p53 and its antagonist, the Mdm2 oncogene, is closed in feedback. This paper proposes an aerospace architecture for translating the p53/Mdm2/DNA damage network into a digital circuitry in which the optimal control theory is applied for obtaining the requested dynamic evolutions of some considered cell species for repairing a DNA damage. The purpose of this paper is not to improve the analysis of the actual mathematical models but to demonstrate the usefulness of such digital circuitry design to detect and predict the cell species dynamics for shedding light on their inner and mutual mechanisms of interaction. Moreover, the cell fate is newly conceived by the modified pulsing mechanism of p53 and other apoptotic species when the digital optimal control is applied to an apoptosis wiring diagram

On p21 tracking property in cancer cell unravelled bio-digitally in silico. Are apoptosis principles universal?

Upon severe DNA damage, p21 acts in a dual mode; on the one hand, it inhibits the cyclin-CDK complex for arresting the G2/M transition and on the other hand, it indirectly becomes an apoptotic factor by activating--in sequence--the retinoblastoma protein, E2F1 and APAF1 expressions. But, in a cancer cells proliferation, the mechanisms of, and participants in, the apoptosis failure remain unclear. Since the p21/p53/Mdm2 proteins network normally involves a digital response in a cancer cell, through an original design of a cell signalling-protein simulator, we demonstrate, in silico, that apoptosis phase instability is fully reciprocated by p21 mRNA irregular dynamics which operates according to a "tracking memory" principle. We show p21mRNA paradoxically ceases to act in concert with specific target genes and becomes an underlying accomplice of cancer proliferation. Here, we also identify the mechanisms for allowing the cancer cell to re-enter inside a steady stable apoptosis phase.Upon severe DNA damage, p21 acts in a dual mode; on the one hand, it inhibits the cyclin-CDK complex for arresting the G2/M transition and on the other hand, it indirectly becomes an apoptotic factor by activating--in sequence--the retinoblastoma protein, E2F1 and APAF1 expressions. But, in a cancer cells proliferation, the mechanisms of, and participants in, the apoptosis failure remain unclear. Since the p21/p53/Mdm2 proteins network normally involves a digital response in a cancer cell, through an original design of a cell signalling-protein simulator, we demonstrate, in silico, that apoptosis phase instability is fully reciprocated by p21 mRNA irregular dynamics which operates according to a "tracking memory" principle. We show p21mRNA paradoxically ceases to act in concert with specific target genes and becomes an underlying accomplice of cancer proliferation. Here, we also identify the mechanisms for allowing the cancer cell to re-enter inside a steady stable apoptosis phase

On MR Differential with Limited Slip

Design of a magnetorheological (MR) sports car differential is presented in this paper, with the aim of the total mass reduction and the torque maintenance. The torque output is controlled by adjusting the applied magnetic field. The nominal output torque of the differential is derived by using Bingham plastic constitutive model; the choice of the materials occurs to minimize the thickness of the circuit, but preliminary sizing based on electromagnetic theory does not lead to satisfactory results. Electromagnetic finite element analysis (FEA) is performed to estimate the effective distribution of the magnetic field. The shear stress distribution in MR Fluid is theoretically predicted using the distribution of magnetic flux density evaluated by FEA. An optimization process is applied to obtain the desired performance in terms of mass and torque; first stage optimization allows finding the best geometry of the magnetic circuit to provide the required torque. Furthermore the optimization of the shape of the reel box is carried out, in order to reduce the mass of the differential, and the vehicle mass in consequence, with satisfactory results. The conclusion is done that magnetorheological differential can be used as low efficiency differential even in the absence of magnetic field, reducing the likelihood of skidding of one of the two wheels of the same axle