Estimation en ligne de paramètres d'un palier magnétique

National audienceCet article présente un algorithme d'estimation de paramètres dans le cas d'un palier magnétique. De tels procédés sont des systèmes intrinsèquement instables ayant une dynamique fortement non linéaire. Cette approche est basée sur les outils mathématiques suivants : Transformée de Laplace et calcul opérationnel. On développe ici le modèle du palier magnétique afin d'être capable d'estimer certains paramètres difficilement mesurables et pouvant varier légèrement dans le temps. L'expression des estimations est écrite comme une fonction d'intégrales des entrées et des sorties du système. Les simulations présentent une estimation rapide (<0.2 secondes) et robust

Permanent Magnet Synchronous Motor control via Parameter Dependent Relay Control

International audienceThe article presents a novel control strategy for the control of Permanent Magnet Synchronous Motor (PMSM). The approach is motivated by the fact that PMSM are usually controlled by relays and thus only a finite set of control inputs is available. However in classical control design the use of Pulse-Width Modulation (PWM) ignores the relay nature of the actuators. Here we propose a direct relay control. As PMSM may be modeled as Linear Parameter Varying (LPV) systems, we propose a Parameter Dependent Relay (PDR) control. A design based on Linear Matrix Inequalities (LMI) allows to derive the switching surfaces, which depend on the motor position. The theory described is illustrated by simulations results

Derivative based control for LPV system with unknown parameters: An application on a Permanent Magnet Synchronous Motors

International audienceThis paper deals with the robust stabilization of a class of Linear Parameter Varying (LPV) systems in the continuous time case. Instead of using a state observer or searching for a dynamic output feedback, the controller is based on output derivative estimation. This allows the stabilization of the plant with very large parameter variation and uncertainties. The proof of stability is based on the polytopic representation of the closed loop, Lyapunov conditions and system transformations. The result is a control structure with only few parameters which are tuned via very simple conditions. This paper illustrates the usefulness on real application: Permanent Magnet Synchronous Motors (PMSM) position control

Toward on-line robot vibratory modes estimation

International audienceThis paper is concerned with preliminary results on robot vibratory modes on-line estimation. The dominating oscillatory mode of the robot arm is isolated by comparing the robot position given by the motors encoders and an external measure at the tool-tip of the robot arm. In this article the external measurement is provided by a laser tracker. The isolation of the oscillation permits to identify the vibratory mode, \textit{i.e.} the natural frequency and the damping ratio of the undesired phenomena. Here we propose a comparison between the algebraic method and the sliding modes for the parameter identification. This comparison is motivated by the fact that both methods provide finite time convergence. Experimental identifications are proposed on a 6 degrees of freedom (DOF) manipulator robot, Stäubli RX-170B

On-line parameter estimation of a magnetic bearing

International audienceThis article presents a parameter estimation algorithm for a magnetic bearing. Such process have strongly nonlinear dynamics andare inherently unstable systems. A simplified model of the magnetic bearing is developed in order to be able to estimate certain parameters. These parameters are difficult to measure, and may slightly vary over time. The expression of the estimates is written as a function of integrals of the inputs and outputs of the system. The experiments show a fast and robust on-line identification

Estimation des paramètres d'un moteur pas-à-pas sans capteur mécanique

International audienceLe papier présente une méthode d'identification sans capteurs des paramètres de moteurs pas-à-pas à aimant permanent. La mesure des variables électriques est supposée disponible, mais on s'affranchit de l'utilisation de capteurs mécaniques (position et vitesse). Les données sont obtenues avec une commande de tension en boucle ouverte à différentes vitesses, et en utilisant un référentiel qui présente des avantages similaires au référentiel d-q standard, sans la nécessité d'un capteur de position. La méthode exploite attentivement des expressions linéaires par rapport aux paramètres et un algorithme de moindres carrés. Dans un cas, la sur-paramétrisation est résolue en utilisant la théorie de l'élimination. En général, les paramètres identifiés expérimentalement en utilisant cette méthode se trouvent être très proches de ceux obtenus avec les capteurs de position et de vitesse. L'approche est aussi potentiellement applicable à d'autres types de moteurs synchrones

Joint Identification of Stepper Motor Parameters and of Initial Encoder Offset

International audienceThe paper presents a new procedure to identify at the same time the electrical parameters of a permanent magnet stepper motor (PMSM) and the initial offset of an incremental encoder. The model considers effects due to the permanent magnet and to variable reluctance, and the resulting theory is applicable to cases where both or only one of these terms is present. The standard DQ model of PMSM's assumes that the permanent magnet is lined up with a winding when the position is zero. When an incremental encoder is used, an initialization procedure is required to zero the initial offset. In contrast, this paper computes a transformed model that accounts for the initial offset. then develops a least-squares identification algorithm that estimates the machine's electrical parameters together with the offset angle. Experiments show that the estimation procedure and a closed-control method using the estimated offset perform similarly compared to when the offset is reset to zero using an initialization procedure

Parameter estimation of permanent magnet stepper motors without position or velocity sensors

International audienceThe paper presents a new sensorless parameter identification method for permanent magnet stepper motors. Current sensors are assumed available, but position and velocity sensors are not. Data is obtained with open-loop voltage com- mands at multiple speeds. A new reference frame is proposed that presents advantages similar to the standard d − q frame, but without the need for a position sensor. The method exploits carefully derived linear parameterizations and a least-squares algorithm. In one case, overparameterization is resolved using elimination theory. Overall, the parameters identified using the new procedure are found to be very close to those obtained with position sensors. The approach is potentially applicable to other types of synchronous motors as well

Acceleration Feedback via an algebraic state estimation method

International audienceIn many mechanical systems, only accelerations are available for feedback purposes. For example, certain aerospace, positioning systems and force-position controllers in robotic systems, use accelerometers as the only sensing device. This paper presents initial steps towards an algebraic approach for the state estimation based feedback control problem in systems where the highest order derivative of the controlled variable is available. An illustrative case is presented dealing with the trajectory tracking problem for a second order position system on which only the acceleration is available for measurement. Based on an algebraic approach, an on-line algebraic estimator is developed for the unmeasured position and velocity variables. The obtained expressions depend solely on iterated integrals of the measured acceleration output and of the control input. The approach is robust to noisy measurement and it has the advantage to provide fast, on-line, non-asymptotic state estimations in the form of formula requiring only the input and the output of the system. Based on these estimations, a linear feedback control law including estimated position error integrals is designed illustrating the possibilities of acceleration feedback via algebraic state estimation

Toward on-line robot vibratory modes estimation

This paper is concerned with preliminaries results on robot vibratory modes on-line estimation. The dominating oscillatory mode of the robot arm is isolated by comparing the robot position given by the motors encoders and an external measure at the tool-tip of the robot arm. In this article the external measurement is provided by a laser tracker. The isolation of the oscillation permits to identify the vibratory mode, i.e. the natural frequency and the damping ratio of the undesired phenomena. Here we propose a comparison between the algebraic method and the sliding modes for the parameter identification. This comparison is motivated by the fact that both methods provide finite time convergence. Experimental identifications are proposed on a 6 degrees of freedom (DOF) manipulator robot, St¨aubli RX-170B