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ABSTRACT: The paper analyzes the stator current spectrum of a healthy squirrel cage induction machine. The knowledge of stator current spectrum of the healthy cage rotor induction machine is a starting point for diagnosis of different faulty regimes using a noninvasive diagnostic technique known as motor current signature analysis. Magnetomotive force (MMF) space harmonics, slot permeance harmonics as well as saturation of main magnetic flux path through the virtual air gap permeance variation are taken into analytical consideration. Air gap flux density waves were obtained by multiplying the corresponding MMF waves with air gap permeance waves. General rules which give the connection between the number of rotor bars and the existence of rotor slot harmonics in the stator current spectrum are derived, too. Their appearance as well as magnitude depends on the corresponding air gap flux density wave pole pair number. Predicted spectral components of the stator current are experimentally verified on two laboratory motors with different number of rotor bars.
Diagnostics for Electric Machines, Power Electronics & Drives (SDEMPED), 2011 IEEE International Symposium on; 10/2011
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ABSTRACT: A fact is that wind energy is both green and expensive energy. In order to increase its economic competence, wind turbine faults should be reduced and prevented. In wind turbines faults most commonly occur in the gearbox and in the generator system components like power converter or generator electromechanical parts. This paper proposes a fault-tolerant control strategy for variable-speed variable-pitch wind turbines in case of identified and characterized generator electromechanical faults like broken rotor bar or winding inter-turn fault. In particular we propose an upgrade of the torque control loop with flux-angle-based torque modulation. Usage of pitch controller in the low wind speed region is also proposed to intentionally reduce power capture in order to avoid or to postpone the system fault development. Presented fault-tolerant control techniques are developed considering their easy implementation and installation in available control systems of existing wind turbines to extend their life cycle and energy production. Simulation results for the case of 700 kW direct-drive wind turbine and the identified stator winding fault are presented.
Industrial Electronics (ISIE), 2011 IEEE International Symposium on; 07/2011
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ABSTRACT: Multi-mass drives are in principle low-damped oscillatory systems. Controllers for such systems must be designed with care, especially when safety constraints or equipment constraints need to be respected during their operation. Recently a robust protective control technique based on invariant sets was introduced and experimentally verified for such applications. The idea is to correct the control input to the drive as to avoid the multi-mass drive constraints violation in the future. In this paper we merge Linear Quadratic Regulator (LQR) with the correction procedure and exploit convexity of the raised control problem to significantly reduce the required on-line computational power and memory requirements and to broaden the applicability of the control scheme to multi-input systems.
Industrial Electronics (ISIE), 2011 IEEE International Symposium on; 07/2011
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ABSTRACT: In this paper we propose a protective predictive control scheme for motor drives with elastic transmission that are subject to physical and safety constraints on their variables. Namely, we extend the classical LQR controller with a safety set obtained using invariant sets methodology. The easy implementation of this set on-line allows the correction of the LQR control signal in order to suppress the violation of constraints and thus avoid possibly dangerous situations during the drive transients. The added protective algorithm can be also used with any other drive control scheme to correct its outputted control signal.
Power Electronics and Motion Control Conference, 2008. EPE-PEMC 2008. 13th; 10/2008
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ABSTRACT: For a switched reluctance motor (SRM) torque control we propose an approach based on constrained predictive control. In particular, the highly nonlinear characteristic of the motor torque is approximated in a piecewise affine (PWA) form. Based on this approximation a simple PWA model of the SRM is constructed and used for model-based torque controller design. The user-specified maximum torque tracking error allowed is used to determine the set in the space of motor states and torque references within which we compute the polyhedral maximum controlled invariant set for control.
Decision and Control, 2007 46th IEEE Conference on; 01/2008
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ABSTRACT: An electronic throttle is a dc-motor-driven valve that regulates air inflow into the combustion system of the engine. The throttle control system should ensure fast and accurate reference tracking of the valve plate angle while preventing excessive wear of the throttle components by constraining physical variables to their normal-operation domains. These high-quality control demands are hard to accomplish since the plant is burdened with strong nonlinear effects of friction and limp-home nonlinearity. In this paper, the controller synthesis is performed in discrete time by solving a constrained time-optimal control problem for the piecewise affine (PWA) model of the throttle. To that end, a procedure is proposed to model friction in a discrete-time PWA form that is suitable both for simulation and controller design purposes. The control action computation can, in general, be restated as a mixed-integer program. However, due to the small sampling time, solving such a program online (in a receding horizon fashion) would be very prohibitive. This issue is resolved by applying recent theoretical results that enable offline precomputation of the state-feedback optimal control law in the form of a lookup table. The technique employs invariant set computation and reachability analysis. The experimental results on a real electronic throttle are reported and compared with a tuned PID controller that comprises a feedforward compensation of the process nonlinearities. The designed time-optimal controller achieves considerably faster transient, while preserving other important performance measures, like the absence of overshoot and static accuracy within the measurement resolution
IEEE Transactions on Industrial Electronics 07/2007; · 5.16 Impact Factor
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ABSTRACT: In this paper piecewise ARX (PWARX) model identification of a nonlinear MIMO process is discussed. PWARX models comprise several ARX models where each of them is valid over a polytope in the regressor space. The identification procedure simultaneously estimates both the polytopic regions and the ARX model coefficients in each region. Here we use the clustering-based identification procedure, that is designed for MISO processes, and proceed in a natural way to extend this approach to identification of nonlinear MIMO processes, A very important role in identification of process nonlinearities for each MISO process plays a suitable linear transformation in the regressor space. A new way for choosing that linear transformation is suggested, automatically from the identification data position in the regressor space. Using the proposed procedure, a PWARX MIMO model of a magnetic levitation laboratory setup is identified and validated
Computer Aided Control System Design, 2006 IEEE International Conference on Control Applications, 2006 IEEE International Symposium on Intelligent Control, 2006 IEEE; 11/2006
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ABSTRACT: Piece wise affine (PWA) model comprises several affine dynamics defined over polyhedral regions in the regressor (state+input) space. Identification of a PWA model is very often a starting point for the controller synthesis of hybrid systems. In this paper we extend the clustering-based procedure for identification of a piece wise autoregressive exogenous (PWARX) model proposed in [Ferrari-Trecate et al., 2003]. By exploiting a priori process knowledge we choose an appropriate linear transformation of the regression vector for a better and more efficient identification of the process nonlinearities. We significantly reduce the computational complexity of the classification algorithm for finding the complete polyhedral partition of the model domain. This modified clustering-based procedure is used to identify a PWARX model of the electronic throttle-a highly nonlinear component that regulates air inflow to the engine of a car.
Industrial Electronics Society, 2005. IECON 2005. 31st Annual Conference of IEEE; 12/2005
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ABSTRACT: In order to perform useful tasks the mobile robot's current pose must be accurately known. Problem of finding and tracking the mobile robot's pose is called localization, and can be global or local. In this paper we address local localisation or mobile robot pose tracking with prerequisites of known starting pose, robot kinematic and world model. Pose tracking is mostly based on odometry, which has the problem of accumulating errors in an unbounded fashion. To overcome this problem sensor fusion is commonly used. This paper describes two methods for calibrated odometry and sonar sensor fusion based on Kalman filter theory and occupancy grid maps as used world model. Namely, we compare the pose tracking or pose estimation performances of both most commonly used nonlinear-model based estimators: extended and unscented Kalman filter. Since occupancy grid maps are used, only sonar range measurement uncertainty has to be considered, unlike feature based maps where an additional uncertainty regarding the feature/range reading assignment must be considered. Thus the numerical complexity is reduced. Experimental results on the Pioneer 2DX mobile robot show similar and improved accuracy for both pose estimation techniques compared to simple odometry.
Control and Automation, 2005. ICCA '05. International Conference on; 07/2005
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Industrial Electronics, 2005. ISIE 2005. Proceedings of the IEEE International Symposium on; 02/2005
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ABSTRACT: Electronic throttle body (ETB) is a car device that regulates air inflow into the motor's combustion system. Its performance has a major impact on the quality of the overall engine speed control. However, due to the usage of cheap components and some design features the ETB exhibits several nonlinear phenomena. This nonlinear behavior and the fact that there is only one measurement available - low quality measurement of the throttle position makes a design of the throttle controller a challenging task. Our approach is to model the ETB as a discrete time piecewise affine (PWA) system and apply model predictive control (MPC) strategy to design an explicit state feedback control law. Since MPC is a full-state controller and there is only one measurement available the rest of the states have to be estimated. We have chosen unscented Kalman filter (UKF) for the estimation purpose since it was performing the best in the presence of strong, almost discontinuous, process nonlinearities. In the end, MPC and UKF algorithm were implemented and tested on the real electronic throttle for the case of set-point reference. Experimental results indicate that the performance of cheaply produced components can be significantly improved with a good control strategy.
Industrial Electronics, 2004 IEEE International Symposium on; 06/2004
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ABSTRACT: Electronic throttle body (ETB) is a device used in cars to regulate air inflow into the motor's combustion system. Its good behavior is crucial for the superimposed engine speed control system. However, electronic throttle body is a highly nonlinear process, and its only measurable state is the throttle valve position measured by a cheap potentiometer of low resolution, resulting in significant quantization noise. In order to apply an advanced control strategy, all states should be usually available and the measurement noise should be reduced. With these two goals in mind we have implemented an extended Kalman filter (EKF), as a common solution for state estimation of nonlinear systems, and an unscented Kalman filter (UKF), which is a preferable solution when the process nonlinearities are very strong. Both filters are based on discrete time piece-wise affine process model which uses new friction model. By experimental tests on a real ETB it is shown that UKF gives better estimates of its state variables.
Industrial Technology, 2003 IEEE International Conference on; 01/2004
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ABSTRACT: In this paper we show how hybrid system theory can be used to obtain a state-feedback optimal control law for an electronic throttle. After modelling the electronic throttle as a piece wise affine (PWA) system, we derive an optimal control law for such a hybrid system via dynamic programming. Results indicate that constrained finite time optimal control of small/medium sized PWA systems with fast sampling times can be successfully implemented.
American Control Conference, 2003. Proceedings of the 2003; 07/2003
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ABSTRACT: Different conformational states of the purified plasma membrane Ca2+-ATPase from pig erythrocytes have been detected by circular dichroism (CD) and fluorescence spectroscopy. The helical content of the enzyme decreased by about 10% in the transition from the Ca2+ high-affinity form (10 microM free Ca2+ = E1 state) to the VO4(3-)-inhibited state (20 microM VO4(3-) = E2 state). The changes in the CD spectra did not show full reversibility upon reversing the E1-E2 transition, whereas those in the fluorescence spectra did. A temperature-dependent loss of alpha-helical content in the presence of Ca2+ was also observed. Intrinsic fluorescence measurements revealed an increase in fluorescence intensity upon addition of Ca2+. The change was fully reversed by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The increase in fluorescence intensity was partly reversed by adding ATP, an effect which is suggested to correspond to the "Ca2+-occluded" form of the ATPase. The steady-state level of the fluorescence intensity was stable for several minutes in the presence of 100 microM ATP. By contrast, the decrease of fluorescence intensity induced by limiting concentrations of ATP (= 1 microM) was only transient, indicating the decomposition of the phosphorylated intermediate of the ATPase and the reestablishment of the Ca2+ high-affinity form of the enzyme.
Biochemistry 07/1987; 26(13):3921-6. · 3.42 Impact Factor
