Rotor Position Measurement Research Articles

Distributed coordinated speed control of flywheel energy storage matrix systems with model uncertainties and disturbances

SummaryThis paper studies a coordinated rotor speed control of flywheel energy storage matrix systems (FESMS) in the presence of model uncertainties and unknown disturbances. We consider the scenarios that the torque variation during the operation of flywheel energy storage system (FESS) cannot be accurately measured and the coordinated operation of FESMS is realized without the measurements of accurate rotor speeds. We design a distributed extended state observer (ESO) only using local rotor position measurements to estimate the rotor speeds and unknown disturbances. Based on the estimated states, a coordinated control strategy with the compensation of model uncertainties and unknown disturbances is proposed. The proposed control strategy has the advantage of speed‐free feature and active disturbance rejection. By using Lyapunov stability theory, sufficient conditions are given to ensure that the FESMS can achieve the reference tracking. The performance of the control strategy is verified by simulations.

A synthetic position decoding technology for rotary transformers based rotor position measurement system.

This article proposes a rotary transformer position decoding scheme for motor drive control. In this scheme, a simple analog circuit is used to design the excitation circuit and signal conditioning circuit. Demodulate the modulated sine/cosine signal through software and decode it through a phase locked loop (PLL) to obtain the implemented position signal. This scheme completely avoids the use of traditional, specialized decoding chips. At the same time, in order to make the position decoding scheme applicable to different motor drive control platforms, a single-cycle partition average based pulse signal estimation method is proposed for converting the angle position into pulse signals similar to the output of an encoder's phases A, B, and Z, which are referred to as A/B/Z signals in the paper. In order to experimentally validate the proposed scheme, a software decoding platform based on the STM32F407 was built and compared with the decoding results of the chip. The effectiveness and accuracy of the proposed scheme were verified, and it can be effectively applied in the field of motor drive control.

Research Review on Sensorless Measurement Technology of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor (PMSM) has the advantages of high torque/inertia ratio, high power factor, fast dynamic response speed and high reliability, and has been widely used in various high-precision AC drive systems. Incremental encoders are usually used to achieve high precision position feedback information for permanent magnet synchronous motors. The use of sensors leads to cost increase, volume increase and reliability reduction. Therefore, the sensorless measurement technology of permanent magnet synchronous motor is more and more concerned and applied by industry and research fields. In this paper, the related literature of sensorless measurement technology of permanent magnet synchronous motor is investigated, and the sensorless measurement technology is comprehensively reviewed. This paper introduces in detail the basic principle of various sensorless measuring techniques, the accuracy of position measurement and the application in the type of permanent magnet synchronous motor. In this paper, the concept of speed pole logarithm ratio is proposed to divide the speed region, and the initial rotor position, low speed and medium speed non-inductive measurement methods are described and compared. Finally, the non-inductive measurement accuracy of permanent magnet synchronous motor is summarized.

Model Predictive Control of Switched Reluctance Machines for Suppressing Torque and Source Current Ripples Under Bus Voltage Fluctuation

This article presents a novel model predictive method for torque ripple and source current ripple suppression in switched reluctance machines (SRMs) when the bus voltage fluctuates. Based on the measured rotor position, phase current, and phase voltage, the states, including bus voltage, capacitor current, and phase flux-linkage, are calculated for the preparation of the prediction. On this basis, the machine torque and inverter current for all the possible switching states are predicted to construct the cost function. The operating state with the minimum value of cost function is considered as the optimal switch signal and applied to the control power converter, thus achieving the effect of simultaneous reduction of torque ripple and source current ripple. Experimental results show the proposed method has a significant effect on the suppression of both torque ripple and source current ripple even with bus voltage fluctuation, which verifies the effectiveness of the proposed method. The influence of the key factors, such prediction horizon, parametric variation, and weight coefficient, on the machine performance are further investigated. The proposed method is easy to be implemented in the control logic as well as robust to bus voltage fluctuations, enabling to promote the competitiveness of SRMs in electric vehicle application.

Rotor Attitude Estimation for Spherical Motors Using Multiobject Kalman KCF Algorithm in Monocular Vision

This article proposes a rotor attitude estimation (RAE) method for spherical motors using the multiobject Kalman kernel correlation filter (MKKCF) algorithm in monocular vision. A permanent magnet spherical motor (PMSpM) is adopted as the research object, and a monocular area scan camera is equipped in the RAE system with a visual feature component mounted on top of the rotor output shaft. In the proposed MKKCF algorithm, the Kalman filter is used to enhance the robustness and accuracy of KCF tracker for each object. To simplify the proposed algorithm verification, a one-object tracking comparison is conducted among the KCF algorithm, the fast discriminative scale space tracking (FDSST) algorithm, and the Kalman KCF algorithm, and the results show that Kalman KCF tracker is more applicable for RAE. In addition, an RAE test bench is developed, and the MKKCF-based RAE method and the micro-electro-mechanical system (MEMS) (MPU9250) method are compared when estimating the rotor attitude. To set a benchmark, the contact rotor position measurement with encoders is used. The comparison results indicate that the MKKCF-based RAE method works with higher accuracy than the MEMS method. Finally, a closed-loop PMSpM control experiment is conducted by using the proposed MKKCF-based RAE method, and the practicability of the proposed method is proved.

Resolution of Rotor Position Measurement: Modeling and Impact on Speed Estimation

The aim of this article is to provide an accurate modeling of the resolution of rotor position measurement and to evaluate its impact on speed estimation required for electric drive control. Starting from the space vector model of a spatially quantized rotor position measurement, the novel concept of instantaneous quantized speed is introduced, which is shown to constitute the effective input to any speed estimation algorithm. Time-harmonic formulations that are valid under periodic torque disturbances are also derived. These expressions, based on modulation theory, justify the presence of otherwise unexplained time harmonics in the measured rotor position and estimated speed, which appears when the shaft is subjected to torque disturbances. Analytical and numerical results are provided on a well-known observer structure to validate the filtering action of speed estimation algorithms on the harmonics of the instantaneous quantized speed. Finally, experimental verification on a 400 W permanent magnet (PM) servo drive is presented.

High-Performance Control of Surface PM Synchronous Motor by Power Factor Angle-Based Control of Stator Voltage Vector

A new high-performance control method for surface PM synchronous motor is presented here. In this technique, orientation and amplitude of stator voltage vector are directly controlled to achieve stable operation and optimal dynamic performance. Through voltage vector position control, stator current is aligned at nearly $$\angle {90^{\circ }}$$ angle from rotor direct axis. This condition resembles with that of vector control and ascertains fast transient response. Orientation of stator voltage is controlled with the help of measured rotor position and estimated power factor angle. To acquire position information, an absolute optical encoder is used. The amplitude of voltage vector is varied proportionally with rotor frequency to optimize input current. Performance of the drive is comparable to existing vector-controlled drives with position sensors and better than available sensorless drives. Furthermore, the developed drive is simple and cost effective since closed-loop current control or any kind of position observers is not used. Extensive simulation and experimental studies are carried out to evaluate the performance of the drive. The results are found satisfactory.

Synthetic Hybrid-Integral-Threshold Logic-Based Position Fault Diagnosis Scheme for SRM Drives

Reliable rotor position measurement is quite necessary for ensuring accurate commutation control in many kinds of motor drives, such as switched reluctance motor (SRM) and brushless dc motor (BLDC). Traditionally, the Hall sensors and photoelectric switch sensors are widely used in most of these low-cost motor drive systems. In these systems, the rotor position needs to be decoded from the discrete voltage pulses measured by the sensors. Thus, to develop an online position pulse signal fault diagnosis scheme with fast fault-monitoring capability is quite vital for avoiding the abnormal driving control and improving the overall system reliability. In this article, a position pulse signal fault diagnosis scheme based on synthetic hybrid-integral-threshold logic is proposed for SRM drives. In this method, the complementary position pulse signals of each sensor are used as the independent reference signals. By applying special integral calculations on each reference signals and capturing their rising and falling edges, the position pulse fault cases like high-level and low-level faults can be diagnosed immediately with the synthetic thresholds’ comparison logic, respectively. To verify the validity of the proposed method, a 1-kW 12/8 structure SRM prototype with three independent Hall sensors installed is used as a test machine. The experimental results show that this method can diagnose the position fault of each position sensor independently and ensure very fast position fault detection even under dynamic operations with speed transients. Furthermore, the method can be implemented without additional hardware and complex computation, which is quite suitable for constructing a reliable position measurement module to assist the rotor position sensors.

Mechanical Fault Diagnostic in PMSM from Only One Current Measurement: A Tacholess Order Tracking Approach

This article presents a mechanical fault diagnosis methodology in synchronous machines using only a single current measurement in variable speed conditions. The proposed methodology uses order tracking in order to sample the analysis signal as a function of the rotor angle. The spectrum of the signal is then independent of speed and it could be employed in frequency analysis. Order tracking is usually applied using rotor position measurement. In this work, the proposed method uses one current measurement to estimate the position as well as the analysis signal (rotation speed). Furthermore, a statistical approach is used to create a complete diagnosis protocol. At variable speed and with only one current measurement the diagnosis is challenging. However, order tracking will allow simpler analysis. The method is proved in simulations and experimental set-up.

Design of an Observer-Based Architecture and Non-Linear Control Algorithm for Cogging Torque Reduction in Synchronous Motors

The problem of cogging torque is due to a magnetic behavior, intrinsic to synchronous machines and due to the presence of permanent magnets themselves. Cogging torque is a significant problem when the servo drive is used for applications where high precision in terms of position control is required. In this paper we present a method of cogging torque reduction by means of a control technique based on mathematical modeling of the cogging phenomenon itself in order to exploit this knowledge directly in the controller design. The mathematical model is inserted in the dynamic model of the synchronous machine in order to exploit the feedback linearization, providing an expression of the control law in which the contribution of the deterministic knowledge of the phenomenon is directly present. The cogging phenomenon physically depends on the angular position of the rotor, as well as the deterministic model we use to define the control vector. This makes it interesting and innovative to determine whether the control algorithm can be inserted within a sensor-less architecture, where rotor position and angular velocity measurements are not available. For this purpose, we present the use of an extended Kalman filter (EKF) in the continuous-time domain, discussing the advantages of an observer design based on a dynamic motor model in three-phase and direct-square axes. Results are presented through very accurate simulation for a trajectory-tracking problem, completing with variational analysis in terms of variation of initial conditions between EKF and motor dynamics, and in terms of parametric variation to verify the robustness of the proposed algorithm. Moreover, a computational analysis based on Simulink Profiler is proposed, which provides some indication for possible implementation on an embedded platform.

Inductance Testing for IPM Synchronous Machines According to the New IEEE Std 1812 and Typical Laboratory Practices

Equivalent circuit parameters serve as the basis for performance estimation and implementation of power electronic drives controls and therefore their accurate evaluation is very important. Specified in the newly approved IEEE Std 1812, a short-circuit test can be employed, in combination with an open-circuit measurement, in order to determine the back emf and the synchronous inductance. In the case of interior permanent magnet (IPM) machines, this approach can be used only to determine the d -axis inductance and additional and separate measurements are required for the q -axis inductance. In this respect, various methods, inclusive of dc step response tests, on-load tests, and a widely used test in industry, which involves locked-rotor measurements at variable voltage and constant frequency supply, are studied in detail, based on two-dimensional finite element analysis. Locked-rotor methods based on dc current supply and static torque versus rotor position measurements are introduced for determining the q -axis inductance in combination with the standardized open-circuit and short-circuit tests. A critical study of the inductances determined from different tests is conducted, and experimental results on an IPM motor design with non-sinusoidal back emf, relatively high torque ripple, and low leakage are presented.

A New Rotor Position Measurement Method for Permanent Magnet Spherical Motors

This paper proposes a new high-precision rotor position measurement (RPM) method for permanent magnet spherical motors (PMSMs). In the proposed method, a LED light spot generation module (LSGM) was installed at the top of the rotor shaft. In the LSGM, three LEDs were arranged in a straight line with different distances between them, which were formed as three optical feature points (OFPs). The images of the three OFPs acquired by a high-speed camera were used to calculate the rotor position of PMSMs in the world coordinate frame. An experimental platform was built to verify the effectiveness of the proposed RPM method.

Back-EMF Based Rotor Position Estimation for Low Cost PMSM Drive Using Fully Connected Cascade Artificial Neural Networks


 Permanent Magnet Synchronous Motors (PMSMs) are widely used mainly due to their high torque per volume, high efficiency and low maintenance cost, among other advantages. To perform the vector control on rotor speed and stator currents, the feedback of those variables is necessary, which can be done directly or by estimation. Measuring rotor position and speed directly requires the use of a mechanical device attached to the motor shaft, increasing the drive system volume and its maintenance cost. To overcome such disadvantages, many sensorless methods for speed estimation have been proposed. Among those methods, various strategies based on Artificial Neural Networks (ANNs) can be found. This paper presents a back-electromotive force estimator based on Fully Connected Cascade ANNs (FCC-ANNs). From the estimator, rotor position and speed can be obtained. Simulation and experimental results using automatically generated C code functions for the FCC-ANNs using fixed point notation provided rotor position estimation with simple implementation.

An Improved Rotor PLL (R-PLL) for Enhanced Operation of Doubly Fed Induction Machine

A versatile method to compute the rotor position of a three-phase induction machine under balanced or unbalanced grid voltage is proposed in this paper. The rotor position of a doubly fed induction machine (DFIM) is computed in closed loop using R-PLL with the q -axis stator flux as the reference signal and the computed rotor speed as feed forward input. A PI controller is used to reduce the phase error while the updated feed forward input (rotor speed) eliminates the frequency error, thereby facilitating a quick and accurate response. Furthermore, the rotor speed is computed directly using only the measured stator voltages and currents, independent of any measurement of rotor current or position. Also, the speed computation process is free from voltage or flux integration or heuristic mathematical calculations. Starting on the fly and accurate computation near and through the synchronous speed even under unbalanced grid voltage are the attractive features. The effectiveness of the scheme is validated through PSCAD/EMTDC simulations and laboratory experiments. Excellent results demonstrate the efficacy of the proposed scheme.

Suspension force control of bearingless permanent magnet slice motor based on flux linkage identification

The control accuracy and dynamic performance of suspension force are confined in the traditional bearingless permanent magnet slice motor (BPMSM) control strategies because the suspension force control is indirectly achieved by adopting a closed loop of displacement only. Besides, the phase information in suspension force control relies on accurate measurement of rotor position, making the control system more complex. In this paper, a new suspension force control strategy with displacement and radial suspension force double closed loops is proposed, the flux linkage of motor windings is identified based on voltage–current model and the flexibility of motor control can be improved greatly. Simulation and experimental results show that the proposed suspension force control strategy is effective to realize the stable operation of the BPMSM.

An approach to selecting the optimal sensing coil configuration structure for switched reluctance motor rotor position measurement.

Accurate rotor position signal is highly required for controlling the switched reluctance motor (SRM). The use of galvanic isolated sensing coils can provide independent circuit for position estimation without affecting the SRM actuation. However, the cross-coupling between main winding and sensing coil, and the mutual coupling between adjacent phase sensing coils may affect the position estimation performance seriously. In this paper, three sensing coil configurations in a 12/8 structure SRM are analyzed and compared for selecting an optimal configuration that can effectively minimize the bad effects of the cross-coupling factors. The finite element analysis and experimental results are provided for verification.

Estimation of PMSM Magnetic Saliency Using Injection Technique

The permanent magnet synchronous motor (PMSM) has very attractive properties such as: high dynamics, small size, high efficiency, low maintenance, small size and mass to power ratio, which make it suitable for the use in industrial drives. In particular its higher efficiency means that PMSM may be used in applications where the energy savings compensate the higher initial cost. For the best utilization of PMSM properties is very important to use some of modern control techniques. But the techniques require information about rotor position. Rotor position measurement is performed using sensors that are expensive and mainly reduce the reliability of the drive. This fact is the reason for interest in sensorless control techniques. In the article, emphasis is placed on sensorless control of PMSM using voltage signal injection, which requires magnetic saliency of the machine. Magnetic saliency and machine suitability for sensorless control using injection methods can be determined in advance using a measurement method whose mathematical analysis is presented in the article. The measurement method was simulated using software product Matlab-Simulink and experimentally verified on a laboratory stand with the AC drive. DOI: http://dx.doi.org/10.5755/j01.eee.20.2.4784

Sensorless Control Strategy of Electrical Variable Transmission Machines for Wind Energy Conversion Systems

This paper focuses on the control for the dual power flow wind energy conversion system (DPF-WECS) based on the permanent magnet electrical variable transmission (PM-EVT) machine. The PM-EVT machine can be considered as two permanent magnet synchronous machines (PMSMs) by ignoring the magnetic field coupling between the inner rotor and stator windings. For the DPF-WECS, the speed of the inner rotor should be controlled precisely to generate the constant voltage and constant frequency electricity. However, the rotor position of the inner PMSM composed of the inner rotor and outer rotor is difficult to be measured exactly due to the rotational stator and rotor. Thus the inner PMSM is hardly to be controlled using vector control strategy with the measured rotor position. In this paper, a sensorless control strategy based on the model reference adaptive system (MRAS) for the PM-EVT machines with double layer permanent magnet outer rotor for the DPF-WECS is proposed and evaluated by simulation. The effectiveness of proposed control strategy is verified by experimental results.

Robust integral backstepping control for sensorless IPM synchronous motor controller

In this paper, a sensorless speed control for interior permanent magnet synchronous motors (IPMSM) is designed by combining a robust backstepping controller with integral actions and an adaptive interconnected observer. The IPMSM control design generally requires rotor position measurement. Then, to eliminate this sensor, an adaptive interconnected observer is designed to estimate the rotor position and the speed. Moreover, a robust nonlinear control based on the backstepping algorithm is designed where an integral action is introduced in order to improve the robust properties of the controller. The stability of the closed-loop system with the observer–controller scheme is analyzed and sufficient conditions are given to prove the practical stability. Simulation results are shown to illustrate the performance of the proposed scheme under parametric uncertainties and low speed. Furthermore, the proposed integral backstepping control is compared with the classical backstepping controller.

Flux linkage determination of the switched reluctance motor from measurable quantities at steady-state operations

A new method to obtain flux linkage characteristics of the switched reluctance motor (SRM) is presented. Unlike most of the previously reported methods, the proposed method avoids the usage of a clamping device or a search coil so that it is sometimes more applicable for practical implementations. The proposed method calculates flux linkage with the measured rotor position, phase voltage and phase current of the SRM running in steady states. An error analysis indicates that errors owing to speed ripple and mutual coupling are limited in a reasonable range. The obtained flux linkage is first compared with the result of traditional voltage pulse injection method. Then it is verified by comparing the experimentally measured voltage and current waveforms with the simulated results, where the simulations are performed using flux linkage determined with the presented method. Fairly good agreements have been observed, which indicate that the presented method is effective and accurate.