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EPE 1999 - Topic 05d: Sensorless Techniques
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 05: ELECTRICAL MACHINES AND ADJUSTABLE SPEED DRIVES > EPE 1999 - Topic 05d: Sensorless Techniques
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	A Method of Speed Sensorless Vector Control of Parallel Connected...   By T. Fushimi; H. Natsume; K. Matsuse	[View]   [Download]
Abstract: The purpose of this work is to present the speed sensorless vector control method of the torque production from each rotor of dual induction motors with parallel connected stator windings fed by a single inverter and to discuss the performance of the system from simulation results. A control method for the parallel connected dual induction motor drive system was proposed by [1]. The method uses average and differential currents flowing into stator windings and rotor flux of dual induction motors. This paper proposes the theory that the adaptive rotor flux observer for estimating the induction motor speed [2][3] is applied to.
	A New Approach to calculate the torque of AC Motor Drives   By U. Riefenstahl; S. Kühne	[View]   [Download]
Abstract: This text describes a control structure for induction motors based on stator flux observer to compute the torque with an error of less than 1%. The observer includes a voltage model, an inverse current model, a decoupling network and a master feedback control. This structure considers different requirements of practical interest (standstill, flux weakening). The torque proves to be the most important controlled variable in electrical drive systems apart from the mechanical velocity. In basic industry for example the iron and steel industry or the paper and textile industry the technical quantities tensile stress and tensile force are controlled by the torque of the used electrical drives. In contrast to the torque of electrical drives for the controlled variable mechanical velocity a big quantity of universal and inexpensive measured devices are available. By using torque transducers, the mechanical transfer system has to be separated. A computation of the torque based on a machine model and the electrical supply values is proved to be a favourable alternative in contrast to the use of mechanical torque transducers. By means of a new computation method based on a stator flux and torque observer a dynamical high-grade and stationary precise actual torque value for control assignments and for closed control systems can be obtained.
	An Improved Look-up Table for Zero Speed Control in DTC Drives   By A. Damiano; G. Gatto; I. Marongiu; A. Perfetto	[View]   [Download]
Abstract: The present paper deal with a Direct-Torque-Controlled (DTC) voltage-source inverter-fed induction motor (IM) drive during the start-up and zero speed operations. The analysis of the conventional methods used for DTC servo-drives highlights the difficulty of controlling at zero speed and during the start-up both the electromagnetic torque and the stator flux. The analysis and mathematical modellization of demagnetisation phenomena have allowed to develop an alternative look-up table to control the DTC drive. The main features of the proposed look-up table are of avoiding demagnitisation problem at zero speed and of reducing the power electronic switching frequency at low speed. Results of extensive simulations are presented and discussed to prove the effectiveness of the proposed look-up table.
	Comparison of Practical Performance and Limits of Sensorless IM Drive Using a Closed Loop Flux Observer and a Full Order Flux Observer   By K. Ohyama; G. M. Asher; M. Sumner	[View]   [Download]
Abstract: This paper compares the experimental performance of three flux and speed observers for speedsensorless induction motor drives. The three methods are generally accepted to be leading candidates for high sensorless performance: rotor-flux MRAS, torque-current MRAS and the adaptive non-linear flux observer. The paper discusses baseline conditions for the tests: these include matched load inertia, specified speed estimator dynamics and sensorless operation within a speed control loop. For the comparison tests in the paper, the speed estimation dynamics of the methods are approximately the same; this is important for parameter sensitivity. The paper concentrates on tests for zero and low speed performance and all results shown are under sensorless speed control.
	Current Sensorless Control of DC Motors by Torque and Speed Observer   By G. D. Andreescu; R. Rabinovici	[View]   [Download]
Abstract: The paper proposes a speed control loop with the torque control for DC motors with seperate excitation by measuring only the rotation angle of the rotor. An observer is used to estimate the rotor speed and the disturbance torque. It is employed to compensate the load torque and the changes in the system parameters. However, its performances are similar to those obtained by using an internal current loop with measured currents. Simulation results are presented.
	Design and DSP Implementation of AI-Based Medium Performance Sensorless Induction Motor Drives   By P. Vas; M. Rashed; A. F. Stronach; M. Neuroth	[View]   [Download]
Abstract: The DSP implementation of three speed-sensorless medium-performance induction motor drives incorporating Artificial Intelligence (AI) is discussed. The first drive is a scalar induction motor drive and contains a minimal configuration multi-layer feed-forward neural-network-based speed estimator. Although the neural network was trained by using simulation results onle, it was successfully implemented in an induction motor drive employing a 3 kW cage induction motor. However, the same speed estimator neural network (ANN) was also successfully used in the second induction motor drive with a 2.2 kW motor. The performance of speed estimators using feed-forward multi-layer and recursive artificial neural networks are also compared for this drive. In addition to an ANN-based speed estimator, the third induction motor drive contains a simple fuzzy-logic-based system with a minimum rule-base, which improves the low-speed performance. The experimental results show that the implemented artificial-intelligence-based-based drives give satisfactory performance in a wide speed range. All the drive schemes are simple to implement and the memory requirements are modest. The DSP used is the Texas Instruments TMS320C30.
	Discrete Speed Sensorless Drive of IM: Structure and Stability   By A. Oualha; M. Benmessaoud; I. Slama-Belkhodja; F. Sellami	[View]   [Download]
Abstract: This paper presents a new speed sensorless drive of induction motors for field oriented control. The proposed speed estimator is based on the Model Reference Adaptive Scheme (MRAS). This is done by considering the error between the measured and the estimated stator currents. The estimator formulation is defined and is developed in the discrete case. This description constitutes a rigorous approach. To ensure the stability of the discrete estimator, one can use the hyperstability concept introduced by Popov. The proposed algorithm requires neither matrix calculation nor approximation on Taylor series of matrix exponential. Some simulation results are presented, in order to confirm the theoretical development.
	DSP Implementation of Direct-Torque-Controlled Sensorless Induction Motor and P.M. Synchronous Motor Drives with Minimized Torque Ripples   By P. Vas; M. Rashed; A. F. Stronach; M. Zordan; B. C. Chew	[View]   [Download]
Abstract: The paper discusses the DSP implmementation of torque and flux pulsation minimization techniques in torque controlled sensorless induction motor and p.m. synchronous motor drives with surface mounted magnets. First, the DSP implementation of sensorless high-performance induction motor drives is discussed which uses torque ripple minimization algorithms. For this purpose, the details of a direct-torque-controlled (DTC) induction motor drive with a simple predictive error compensation technique are discussed. The control scheme also requires estimated flux linkages, which are obtained in two ways: by using a mathematical model (observer) and by using a recursive artificial neural network. It is shown that in contrast to a conventional DTC drive, the torque ripples are reduced and the switching frequency is constant. Experimental results are discussed for a fully digital drive, these prove the effectiveness of the technique. In the second part of the paper, predictive torque and flux ripple minimization techniques are discussed for DTC p.m. synchronous motor drives. It is shown, that the proposed predictive error compensation technique significantly reduces the torque and current ripples.
	Instability Phenomena in Sensorless Control of Induction Motors   By L. Harnefors	[View]   [Download]
Abstract: Sensorless indirect field oriented inductionmotor drives using information in the fundamental excitation (back-emf) for speed estimation are considered. It is shown that instability phenomena which are not present for sensored operation occur, both for nominal and low speeds. The problems at nominal speeds are remedied by adding a term to the standard slip relation, such that approximate "voltage model" characteristics are obtained. The low-speed problems are remedied by careful choice of the model machine parameters and the torque-producing stator current component. It is also shown how a simple speed estimation algorithm based on a voltage error can be designed. As no state observer is required, the sensorless control system is computationally very efficient.
	Low Cost Sensorless Position Detection for Brushless DC Motor   By F. Bonvin; Y. Perriard	[View]   [Download]
Abstract: This paper describes a low cost sensorless position detection for brushless dc motor. This method is based on interruption of the 3 phase-currents and reading the back-EMF. The hardware for measuring the back-EMF is very simple. The method is possible thanks to the flexibility of the modern DSP. The proposed scheme shows how it is possible to get a rotor position information with a good accuracy (5°). This precision allows a sinusoidal alimentation. The method takes information about the rotor in a few microseconds (~100Us) and when it wants. That minds it is robust and does not need to wait a back-EMF zero crossing. The goal of this paper is to prove that sensorless sinusoidal alimentation with a very limited number of componentsis also possible in a big speed range. The paper presents the method as well as a wide range range of experimental results showing the feasibility and the robustness of the proposed method with 2 different brushless dc motors. The speed range starts at about 1% and stops higher than 100% of the nominal speed.
	Main Flux Saturation Compensation in Sensorless Vector Controlled Induction Machines for Operation in the Field Weakening Region   By E. Levi; M. Wang	[View]   [Download]
Abstract: Operation of a sensorless indirect rotor flux oriented machine in the field weakening region requires that the variable degree of main flux saturation is recognised and compensated in both the controller and the estimator. The paper proposes a modified version of the rotor flux based MRAC type of speed estimator, that fully compensates for the variable degree of main flux saturation. The estimator is used in conjunction with an appropriate modified indirect vector controller, that accounts for saturation as well. Effectiveness and accuracy of the developed sensorless vector control scheme for operation in the field weakening region are verified by extensive simulation.
	Observer for Sensorless IM Drives with Enhanced Dynamic Performance   By J. Maes; J. Melkebeek	[View]   [Download]
Abstract: The paper deals with an adaptive flux and speed observer for use in speed sensorless induction motor drives. The dynamic performance of a classical adaptive observer is studied and a new adaptive flux and speed observer is proposed for use in stator flux or rotor flux vector controlled induction motor drives. By including a mechanical model for the induction motor and its load the dynamic performance of the speed estimation is improved. Both simulation results and experimental results show the advantages of the proposed adaptive observer.
	Open Loop Position with Current Control of a Synchronous Motor / Generator for a Flywheel Accumulator   By N. Bernard; B. Multon; H. Ben-Ahmed	[View]   [Download]
Abstract: After analyzing the behavioral properties of a current-fed synchronous motor operating at variable speed in an open-loop mode, we demonstrate herein the performance of an open-loop control in the abc reference frame. Oscillation problems observed in the torque are solved by applying a control in an estimated reference frame dq. Due to inaccuracies in the model however, the use of a basic device that provides one impulse per revolution seems to represent an effective arrangement between a synchronous mode control and a classical sensor-free control. Within the control scheme of an energy storage system, two control loops are necessary (current and power). The subject of this work is confined to just the current control. The model used is then validated by experiment.
	Operation of Sensorless Induction Motors using Open Loop Control at low Frequency   By M. Hövermann; B. Orlik; U. Schumacher; U. Schümann	[View]   [Download]
Abstract: Field oriented sensorless speed control of induction motors can become unstable at low frequency. A possible method to prevent unstable operation is to change the open loop control at low speed. This paper presents a field oriented sensorless speed control in combination with a new method of open loop control with better dynamic behavior. Furthermore an identification method of the electrical parameters at standstill is presented.
	Rotor Speed and Position Detection for PM Synchronous Motors Based on Sliding Mode Observer and Kalman Filter   By F. Parasiliti; R. Petrella; M. Tursini	[View]   [Download]
Abstract: This paper presents a solution for rotor speed and position detection in permanent magnet synchronous motors, suitable for application in sensorless control schemes. The approach is based on the estimation of the motor back-EMF through a Sliding Mode Observer and a Kalman filtering. Due to its characteristics, the method is suitable for application in isotropic motors having unknown and whatever shaped back-EMF waveforms. After a brief exposition of the back-EMF model and the explanation of the detection technique, simulation results showing the performance during transient and steady-state operation are presented. Particularly, low speed operation and motor start-up are tested, which are the most critical conditions in back-EMF based sensorless schemes.
	Sensorless Control of PMSM Drives Based on Adaptive Observer   By G. D. Andreescu	[View]   [Download]
Abstract: This paper develops a model reference adaptive system (MRAS) based observer for sensorless vector control of permanent magnet synchronous motor (PMSM) drives. There are used two models in MRAS observer to estimate the linkage flux with relatively clean waveforms. The voltage model in stator reference is the reference model, and the current model in estimated rotor reference is the adaptive model with the rotor position as an adjustable parameter. An adaptive compensation filter depending on speed improves the stability of the pure integration voltage model. The nonlinear adaptation mechanism extracts the error of the flux linkage position and estimates the rotor speed and position. The observer structure, implementation aspects, simulation and experimental results are presented and discussed.
	Sensorless Control of PMSM using a Linear Reduced Order Observer including Disturbance Torque Estimation   By D. Hamada; K. Uchida; F. Yusivar; H. Haratsu; S. Wakao; T. Onuki	[View]   [Download]
Abstract: This paper describes a new approach to the observer-based sensorless control method including the disturbance torque estimation for permanent magnet synchronous motors. Linearizeng the motor model, we can construct the linear reduced order observer for estimating rotor speed and disturbance torque. The validity of the proposed scheme is confirmed by experiments.
	Sensorless Permanent Magnet Synchronous Motor Drive for Domestic Refrigerators   By G. Cecchini; F. Parasiliti; R. Petrella; M.Tursini	[View]   [Download]
Abstract: The Permanent Magnet Synchronous Motor (PMSM) represents an attractive solution for the newgeneration energy-saving domestic refrigerators thanks to its very-high efficiency. The requirements of a compressor system do not allow the use of mechanical sensors on the rotor shaft. Hence, speed and rotor position should be evaluated by means of suitable sensorless techniques. The paper presents a sensorless field-oriented control of a PMSM based on a sliding mode observer and implemented on a DSP TMS320F240 controller. Test results related to different operating conditions confirm that the proposed scheme is well suited for high-efficiency domestic refrigerators.
	Sensorless Position Control of Induction Machines under Load Conditions   By N. Teske; G. M. ASher; K. J. Bradley; M. Sumner	[View]   [Download]
Abstract: An improved rotor position estimator for sensorless position control of induction machines is introduced. The new method ensures that the machine maintains accuracy and stability for high and changing loads without the use of an encoder. The rotor position estimation requires high frequency signal injection and uses a rotor saliency, such as rotor slot harmonics or a circumferential variation of the rotor resistance of leakage inductance. The rotor position estimation reduces the distorting effect due to saturation on the position harmonics which is inherent to machine operation at higher loads. A model is derived to analyze this saturation effect in the machine. A harmonic compensator is employed to remove the distorting saturation harmonics, thus improving the position estimation and achieving a stable position control, including zero speed and position holding under changing loads. A 30kW laboratory drive is operated under closed loop encoderless control using the estimated rotor angle as feedback for position control and field orientation. Experimental results using the new technique are presented to verify the effectiveness.
	Sensorless-speed Control of Induction Motor   By S. Sathiakumar; M. T. Nguyen; Y. Shrivastava	[View]   [Download]
Abstract: A new technique of speed estimation for induction motor has been proposed. This technique is independant of control system and can perform well in all dynamic conditions of motor even at very low speed. The applicability of the algorithm on sensorless drive system has been validated by the simulation of sensorless slip-controlled drive system and sensorless field-oriented control drive system, in which the estimated speed is used in the feedback loop. The sensorless computer-based slip-controlled drive system has been implemented in the laboratory and found to work well under all dynamic conditions. The simulation and experimental results are presented in this paper.
	Soft Computation of Induction Motor State Variables Using Neural Observer   By F. Cupertino; A. Lattanzi; L. Salvatore; S. Stasi	[View]   [Download]
Abstract: This paper deals with the application of a neural observer for the estimation of induction motor state. It focuses on a simple neural observer having neural-network (NN) architecture with six inputs, two flux state outputs, and one hidden layer with a few nodes using sigmoidal-functions. This NN is recurrent, i.e. the two past state outputs are fed back into the network. The other four inputs are the á,â components of stator voltages and currents. This research is aimed at both increasing the learning speed, using the Kalman filter to teach the neural network, and reducing the oscillations of estimated fluxes. Theoretical results are given to show the effectiveness of the neural observer for control purposes in induction motor drives.
	Speed Estimation Methods for Sensorless PM Synchronous Drives - Robustness against Flux Distribution Irregularities   By J. Kabzinski; G. Wasiak	[View]   [Download]
Abstract: We investigate the sensorless permanent magnet synchronous motor drive. We give a short outlook of leading observer design methods such as hypothetical position approach, Luenberger state observer approach, estimation based on voltage equations (voltages and currents measurement or flux integration approach). We investigate robustness of speed estimation in presence of flux irregularities, magnetic asymmetry, discretization and filtration effects. Speed and position estimation error equations are derived and analysed. Numerical experiments are provided to compare robustness of selected observers. Some conclusions on the possibility of obtaining more robust observers are derived.
	Speed Sensorless Control of Induction Motors at Very Low Stator Frequencies   By M. Depenbrock; C. Foerth; S. Koch	[View]   [Download]
Abstract: This paper presents an advantageous way for calculating the stator resistance of an induction machine on-line because speed estimation of an induction machine at very low stator frequencies under linear conditions is only possible if the stator resistance is known. The stator resistance of machines is strongly dependent on the stator temperature. Speed estimation at very low stator frequencies is possible but at stator frequency equal to zero and a small region around zero in practice speed estimation fails under linear conditions due to physics. A scheme is presented to avoid these stator frequencies stationarily by varying the modulus of the stator flux space vector and the slip frequency. With these two improvements speed estimation never fails in any working point. Experimental results of a 120 kW traction drive are shown.
	Stability Analysis of Luenberger Observers for Speed Sensorless High Performance Spindle Drives   By F. Profumo; G. Griva; A. Tenconi; M. Abrate; L. Ferraris	[View]   [Download]
Abstract: One of the issues still open in sensorless high performance spindle drives and gearless traction drives is the possibility to obtain a wide speed range, from almost zero speed to several thousands rpm. This paper presents a comparison of results for sensorless induction motor drives using the Luenberger observer for flux and speed estimation in the cases of typical implementations and of a new implementation. The new proposed method is based on different values of the discrete observer matrix, computed off-line at different speeds in order to keep the poles inside the stability region. As the motor speed changes, the proper observer matrix is selected by the control system: the dynamic response and the stability of the observer are guaranteed at high speed as well as at low speed. The stability of the proposed method has been compared with the stability of other implementations. The performance of a 4-pole induction motor drive, using the proposed observer, has been tested both in simulation and experimentally and the results obtained in the range 20+12000 rpm are compared with the results obtained for the most used implementation method.
	The Effects of Saturation on Sensorless Flux Angle Estimation   By M. L. Aime; M. W. Degner; N. Tice; D. Lorenz Robert	[View]   [Download]
Abstract: This paper analyzes sensorless, direct field oriented control techniques that use saturation-induced saliencies for the estimation of flux angle in induction machine drives. Flux angle estimation based on saturation-induced saliencies relies on the fact that there is a known relationship between the position of the saliency and the flux angle being estimated. This paper first introduces a simple technique for measuring the saliency position under all operating conditions. From these experimental results and theoretical analysis it is shown that the position of saturation-induced saliencies are not fixed relative to any single component of flux in the machine and move significantly with changes in the operating point. This movement of the saliency position relative to the desired flux angle must be modeled for correct, sensorless, direct field oriented control.