Indirect rotor position sensing for variable reluctance motors

Switched reluctance motors are expected to be good candidates in machine drives due to their simple structure. Detection of SRM rotor position is mandatory to effectively control the motion of the motor and commutate the rotor current correctly. However, the detection of the rotor position is done by either adding extra sensors or complicated mathematical calculations that need powerful computers that afford the huge calculation burden. In spite of many methods proposed to eliminate the rotor position sensor, which is needed to commutate the current correctly, research effort is still needed to improve the machine performance. This paper presents a sensorless method for the detection of rotor position method. The proposed method is based on measuring the current of some unexcited rotor phases. This is translated into better reliability due to the reduced number of measuring devices. Moreover, the proposed technique is independent of motor parameters and at the same time it is formed from simple calculations which renders its application to wide range of SRM achieving a more compact and cost-effective drive. The performance of the proposed technique is assessed by means of offline simulations as well as experimental prototypes. The simulation as well as experimental results proves the accuracy of the proposed detection technique.

The paper describes new methods of detecting rotor position in stepping and switched motors, with chopper or series-resistance drives, by monitoring winding currents. In contrast to previous methods of waveform detection, the new techniques are reliable over the complete speed range. It is shown that the most useful indicators of rotor position are: i) current rise times arising from chopping an unexcited phase at low current and ii) the initial rate of current rise as a phase is switched on in a series-resistance drive. Implementation is via simple low-cost electronic circuits and the paper includes discussion of how the techniques can be applied to closed-loop stepping motor control, ministep drives, and optimization of step response.

Nowadays speed-sensorless electromechanical drives are feasible for many applications. The elimination of the mechanical transducer increases reliability, reducing costs. As far as synchronous machine drives are concerned, this issue is critical since the rotor position is fundamental to derive the proper switching sequence. If an SRM is used as an actuator different sensorless techniques have been proposed, essentially based on the rotor position detection by reluctance variation. Since the SRM is a highly nonlinear machine, it is an ideal candidate for the application of artificial neural networks (ANNs). In this paper, the results of a mixed closed loop scheme for the sensorless identification of an SRM drive are presented. A radial basis function ANN has been used, since it is well suited to simulate a nonlinear system over a wide operating area. Then the proposed ANN is applied within a standard control scheme as a position sensor. Simulation results show the effectiveness of the proposed method, since good agreement is reached with experimental results obtained from an SRM drive with a standard position sensor.

ABSTRACTOuter rotor motor configurations are increasingly used in electric aircraft due to their high torque capacity and suitability for vertical take‐off and landing applications. Accurate rotor position detection is critical for closed‐loop control in these applications making a robust outer rotor position sensor essential. Among available sensors, outer rotor variable reluctance resolvers (OR‐VRR) with nonoverlapping windings are promising due to their reliability and winding simplicity. In this paper, an OR‐VRR is customised specifically for aircraft use, with its stator optimised to enhance resolver accuracy. A magnetic equivalent circuit (MEC) model is developed for the proposed OR‐VRR, and mathematical equations are used to optimise the stator teeth. Optimisation is conducted using particle swarm optimisation (PSO), genetic algorithm (GA), ant colony optimisation (ACO), and differential evolution (DE), yielding six stator configurations. Each algorithm offers distinct search mechanisms, and utilising a diverse set of optimisation strategies, the global minimum is more reliable. To refine these designs, the finite element analysis (FEA) is used to simulate and evaluate boundary effects, leading to the selection of an optimal configuration. The chosen OR‐VRR design is then prototyped and mounted on the shaft of an outer rotor brushless motor. Experimental results closely match simulations, validating both the optimisation approach and the effectiveness of the prototyped resolver for precise rotor position detection in electric aircraft.

The rotor position is a key state in the closed-loop control system of the permanent magnet synchronous motor (PMSM). Its measurement accuracy has a significant effect on steady accuracy, dynamic response, and torque ripple. The magnetoresistance (MR) sensor is widely used in the rotor position detection due to its distinct advantages, such as simple structure, high sensitivity, and strong robustness. In this paper, a solution using the giant magnetoresistance (GMR) sensor in TLE5309D chip for angle measurement is introduced, and its feasibility is verified by finite element analysis (FEA) simulation and bench test. In the simulation, two schemes different in the sensor location and the number of permanent magnet poles, are evaluated according to the higher harmonic content and field direction stability near the sensor. The experiment from 1 rpm to 1000 rpm is implemented, and the measurement results after calibration based on discrete Fourier series (DFS) show that the GMR sensor has a good performance in the test.

We report results of both theoretical and experimental studies of optical precursorsgenerated from a square-modulated probe laser pulse having a finite rise and fall time andpropagating through a cold atomic ensemble, under the conditions of either atwo-level Lorentz absorber system or a three-level system with electromagneticallyinduced transparency (EIT). Because of the finiteness of the rise (and fall) time,the precursor signal is observed to decrease with increasing optical depth (α0L). We find that the precursor can experience little absorption even at high opticaldepth if the rise (and fall) time is sufficiently short. At an optical depth ofα0L = 42, the normalized precursor peak intensity is observed to increase from 9% to 27% when therise (and fall) time is shortened from 7 to 3 ns. Meanwhile, we reaffirm that there is noviolation of Einstein’s causality principle in light propagation through both slow and fastlight media. In the EIT system with high optical depth, the main field propagates with asubluminal group velocity and it is separated from the precursor. In the two-level system,the effect of negative group velocity in the anomalous dispersion regime is observed, but wedetect no advancement in the rising edge of the precursors. In both cases, theleading edges of the precursors show no detectable delay to that through vacuum.

Two novel indirect switched reluctance motor (SRM) rotor position (RP) sensing schemes based on winding current amplitude and phase modulation are presented. An off phase is supplied with a stiff sinusoidal carrier voltage from the sensing circuit to be modulated by an RP dependent phase inductance function. The modulated signal is decoded to obtain the information signal and is calibrated to obtain the RP angle continuously. A combination of phase modulation and amplitude modulation encoder techniques was designed and tested on a 5 hp three-phased 6-4 SRM over a wide range of speed. The position detection scheme kept excellent track of the rotor angle continuously under both load and no-load conditions. This scheme is extremely robust to switching noise present in the sensing phase due to mutually induced voltages.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Due to various high frequency injection (HFI) methods operating at zero and low speed range and stator flux based observer running at middle and high speed region, position sensorless vector control system of permanent-magnet synchronous machine (PMSM) has attracted much attention since last decade. How to obtain smooth changeover between these two schemes is the key to achieve a stable wide speed range operation. This paper proposes a new hybrid rotor position observer incorporating high-frequency injection (HFI) method and flux observer. The HFI method employs a newly proposed square-wave scheme with injection frequency equal to switching frequency of inverter, whereas the flux observer adopt a Luenberger type stator flux observer. Another important question is how to compensate difference between reference stator voltages and actual voltages due to inverter's dead-time and nonlinearity. It may have bad effect on the changeover among two observers mentioned. This paper presents an effective scheme for compensating this difference. In order to validate feasibility of the proposed schemes above, a prototype is manufactured and tested for the sensorless vector control system of PMSM with wide speed range using DSP-TMS320F28335 and a commercial PMSM (SPMSM). Experimental results show that the proposed schemes can ensure smooth changeover between two observers above. Stable operation of the sensorless vector control system of PMSM with a wide speed range is realized.

In this paper, the surface discharge current pulses of PEEK (polyether-ether-ketone) under positive repetitive square voltage are measured. The effects of voltage rise time and fall time on pulse parameters of discharge current, instantaneous voltage of discharge and time-lag of discharge are analyzed in detail. The results show that the amplitude of discharge current and the instantaneous voltage of discharge decrease, and the time-lag of discharge and the dispersion of time-lag increase with the increase of voltage rise time. With the increase of voltage fall time, the amplitude of discharge current decreases and the instantaneous voltage of discharge, the time-lag of discharge and the dispersion of time-lag increase. To analyze the influence mechanism of voltage rise time and fall time on surface discharge, the accumulation of surface charge under repetitive square voltage is regarded as a periodic process. Besides, the correlation between forward discharge and back discharge in the process of discharge is analyzed, and the development of discharge is analyzed by using the time-lag theory. Furthermore, the relationship between instantaneous discharge voltage and voltage slew rate is revealed, and the surface charge accumulation processes under different voltage rise times and fall times are compared to reveal the influence mechanism of rise time and fall time on the surface discharge under positive repetitive square voltage.

A comprehensive temporal analysis has been performed on the 319 brightest GRBs with T90 > 2s from the BATSE current catalog. The GRBs were denoised using wavelets and subjected to an automatic pulse selection algorithm as an objective way of identifying pulses and quantifying the eects of neighbouring pulses. The number of statistically signicant pulses selected from the sample was greater than 3000. The rise times, fall times, full-widths at half-maximum (FWHM), pulse amplitudes and pulse areas were measured and the frequency distributions are presented here. All are consistent with lognormal distributions provided the pulses are well separated. The distribution of time intervals between pulses is not random but compatible with a lognormal distribution when allowance was made for the 64 ms time resolution and a small excess (5%) of long duration intervals that is often referred to as a Pareto-L evy tail. The time intervals between pulses are most important because they may be an almost direct measure of the activity in the central engine. Lognormal distributions of time intervals also occur in pulsars and SGR sources and therefore provide indirect evidence that the time intervals between pulses in GRBs are also generated by rotation powered systems with super-strong magnetic elds. A range of correlations are presented on pulse and burst properties. The rise and fall times, FWHM and area of the pulses are highly correlated with each other. The pulse amplitudes are anticorrelated with the FWHM. The time intervals between pulses and pulse amplitudes of neighbouring pulses are correlated with each other. It was also found that the number of pulses, N, in GRBs is strongly correlated with the fluence and duration and that can explain the well known correlation between duration and fluence. The GRBs were sorted into three categories based on N i.e. 3 N 12, 13 N 24 and N 25. The properties of pulses before and after the strongest pulse were compared for three categories of bursts. No major dierences were found between the distributions of the pulse properties before and after the strongest pulse in the GRB. However there is a strong trend for pulses to have slower rise times and faster fall times in the rst half of the burst and this pattern is strongest for category 3 N 12. This analysis revealed that the GRBs with large numbers of pulses have narrower and faster pulses and also larger fluences, longer durations and higher hardness ratios than the GRBs with smaller numbers of pulses. These results may be explained by either homogeneous or inhomogeneous jet models of GRBs. The GRBs with larger number of pulses are closer to the axis if varies with the opening angle of the jet and the imprint of the jet is preserved in the pulse structure of the burst. The distribution of the number of pulses per GRB broadly reflects the beaming by the jet.

Temperature is an important factor affecting the dynamic processes of corona discharge, since the ionization, attachment, and mobility of charged particles are directly related to temperature. Most existing research has investigated the temperature effect on corona discharge through experimental works. However, they are hard to acquire the corona discharge microphysical processes, which are related to the formation of the current pulse and electromagnetic (EM) wave signals. This article proposes a numerical model with temperature-related transport parameters to study the temperature influence on microphysical processes and current pulses for negative corona. By comparing microphysical quantities such as the effective ionization coefficient, density, and velocity of space charges, the effect of temperature on the current pulse parameters including the rise and fall times, amplitude, and pulsewidth is systematically explained. It shows that as the temperature rises, the current pulse amplitude increases, while the other three parameters decrease. The rise time is dependent on the effective ionization coefficient. The fall time is affected by the velocities of negative and positive ions. The experimental results indicate the simulated current pulses are consistent with the measured ones, proving the effectiveness of the proposed numerical model with temperature variation.

Temporally resolved response of a natural type IIA diamond detector to single-particle excitation

The paper examines the optimal efficiency excitation of a variable-reluctance motor (VRM) drive operating at constant speed. The drive comprises a motor, an inverter, an excitation and a control strategy. The excitation refers to a prescribed relationship between the phase currents and rotor position that results in the desired drive behaviour. The excitation is considered from an integrated viewpoint such that overall drive efficiency is maximised for a given torque and speed. An algorithm for the determination of optimal excitation is presented. The algorithm is based on the determination of excitation that nominally meets the drive torque-speed requirement, followed by optimisation of this excitation to improve efficiency. Other performance criteria, such as torque ripple or acoustic noise, could be considered in a similar manner, with appropriate models. The paper applies the algorithm to high-power (60 kW) VRM drive. The results of the optimisation indicate the importance of considering inverted losses when performing the optimization. Inverter losses are shown to be comparable to motor losses, imparting significant influence on the excitation design. The stability implications of the optimal-efficiency excitation are discussed, including the necessity for closed loop control. In addition, the experimental VRM drive design is critically reviewed based on the breakdown of inverter and motor losses. Allowable excitation parameter variations and the dependence of the optimal excitation on load torque are also discussed.

The carrier injection split‐ridge waveguide based optical modulator on SOI has been analyzed in terms of its transient performance. The device operating at both 1.3 and 1.55 μm was simulated and data were collected to compare the transient performance. The device performance is predicted using the 2‐D semiconductor package SILVACO (CAD) software under DC operation. The rise time, fall time and bandwidth for the device operating at both wavelengths were characterized. It is found that at 1.3 μm, the rise time and fall time are 36.5 ns and 13 ns respectively. Meanwhile at 1.55 μm, the rise time and fall time are 41 ns and 9 ns respectively. It is found that the 3 dB bandwidths for the device are 8.53 and 9.7 MHz for 1.55 and 1.3 μm respectively.

This paper presents the design of a variable reluctance motor with a multi-flux guided solid rotor. The analysis of the magnetic circuit and calculation of the machine inductances are carried out using the finite element method (FEM). This allows the prediction of machine performances and the optimum design parameters which maximises L/sub d/ and minimises L/sub q/. Based on the design, an experimental machine is fabricated. The experimental motor has been tested and its performance compared with an equivalent induction motor as a variable speed drive.