Position Angle Error Research Articles

Sensorless Control of SPMSM Based on High-Frequency Positive- and Negative-Sequence Current Dual-Demodulation

In surface-mounted permanent magnet synchronous motor (SPMSM) low-speed sensorless control, the high-frequency sinusoidal voltage injection method for rotor position estimation is affected by the low saturation salient rate of SPMSM and the system delay, resulting in estimation error. This paper proposes a dual-demodulation method utilizing the high-frequency positive- and negative-sequence stator current of the motor. This method is based on the principle of maximizing the effect of the salient inductance component and minimizing the significant component of noise, which improves the utilization of the current containing angle information and increases the signal-to-noise ratio of the position angle error fed to the rotor position observer. The DC bias of the current caused by system delay is also eliminated so that the accuracy of position estimation is improved. The proposed method is verified by experiment, and the results show that the accuracy of the estimated rotor position and dynamic performance of the estimator are greatly improved compared to existing methods.

An Extended Approach for Validation and Optimization of Position Sensor Signal Processing in Electric Drive Trains

Due to the increasing electrification of automotive drive train systems, accurate position and speed sensors play an important role to achieve an optimum drive train performance and driving range. These sensor systems determine the rotor shaft position to deliver exact data for efficient drive train control. The system itself must be reliable, sufficiently accurate and cost efficient at the same time. In this way, the design process of the sensor system is influenced by a trade-off, which influences the system performance in view of different parameters, e.g., resolution and data processing accuracy. The focus of the present work is to introduce a method for benchmarking the performance of not only the rotor shaft position sensor, but the whole electric drive train sensor systems by use of a highly accurate reference system on a specifically developed test bench. To achieve a significant benchmark statement by determination of the rotor position angle error, the independent measuring systems, the automotive drive train system and the reference system are synchronized by the use of a common trigger/clock signal. The mentioned signal defines the time steps of the system under test rotor position angle capturing procedure and those of the reference system simultaneously. This enables a common time-base for two independent working measurement systems. This publication provides information about a concept for enhanced rotor position sensor evaluation that enables the merging of real-time data processing with test bench measurement. This procedure provides an important basis for the selection and optimization of position sensor systems for sophisticated electric powertrains.

POLICAN: A Near-infrared Imaging Polarimeter at the 2.1m OAGH Telescope

POLICAN is a near-infrared imaging linear polarimeter developed for the Cananea Near-infrared Camera (CANICA) at the 2.1 m telescope of the Guillermo Haro Astrophysical Observatory (OAGH) located in Cananea, Sonora, México. POLICAN is mounted ahead of CANICA and consist of a rotating super-achromatic (1–2.7 μm) half-wave plate (HWP) as the modulator and a fixed wire-grid polarizer as the analyzer. CANICA has a 1024 × 1024 HgCdTe detector with a plate scale of 0.32 arcsec/pixel and provides a field of view of 5.5 × 5.5 arcmin2. The polarimetric observations are carried out by modulating the incoming light through different steps of half-wave plate angles (0°, 22.°5, 45°, 67.°5) to establish linear Stokes parameters (I, Q, and U). Image reduction consists of dark subtraction, polarimetric flat fielding, and sky subtraction. The astrometry and photometric calibrations are performed using the publicly available data from the Two Micron All Sky Survey. Polarimetric calibration includes observations of globular clusters and polarization standards available in the literature. Analysis of multiple observations of globular clusters yielded an instrumental polarization of 0.51%. Uncertainties in polarization range from 0.1% to 10% from the brightest 7 mag to faintest 16 mag stars. The polarimetric accuracy achieved is better than 0.5% and the position angle errors less than 5° for stars brighter than 13 mag in H-band. POLICAN is mainly being used to study the scattered polarization and magnetic fields in and around star-forming regions of the interstellar medium.

Position sensorless technology of switched reluctance motor drives including mutual inductance

To reduce the effect of estimation position angle error caused by mutual inductance on sensorless control of switched reluctance motor (SRM) in clear command channel mode, a SRM rotor position estimation method is presented. Using this method, the effect of mutual inductance can be eliminated without measuring mutual inductance. First, different working states are analysed. When working at single-phase excitation, mutual inductance can be ignored, inductance model method is used to estimate the position angle. When working at two-phase excitation situation, mutual inductance is non-zero, based on flux linkage-difference a new method is used to eliminate mutual inductance influence. Finally, the proposed method is verified by experiments. Experiment results show that compared with the mutual inductance ignored methods, the proposed method has higher estimation accuracy. This method can realise stable and reliable running of SRM sensorless control in wider speed range.

Compensation Scheme of Position Angle Errors of Permanent-Magnet Linear Motors

The position angle is very important in the current control of permanent-magnet linear motors (PMLMs), and its error affects the control precision of currents. However, the position angle is often not accurately detected because of faults in motor making, pulse loss of linear encoders, and so on. In order to precisely control the currents of PMLMs, a compensation scheme of position angle errors is proposed based on the mathematical relation between position angle errors and currents. In the scheme, a position angle error compensator is designed to compensate the position angles detected by linear encoders. Furthermore, a filter and a class of iteration learning algorithm are proposed to avoid the errors produced by detected phase currents and phase voltages. Simulation results show that position angle errors of PMLMs are fully compensated. Using the designed position angle error compensator, currents can be controlled in a more precise manner.

FIMS 관측 자료의 위치보정 알고리즘 개발

The FIMS(Far-ultraviolet IMaging Spectrograph), the main payload onboard the first Korean Science Technology SATellite, STSAT-1, has performed various astronomical observations, including the Cygnus Loop, Vela supernova remnants, LMC(Large Magellanic Cloud), since its launch on September 2003. It has been found that the attitude information provided by spacecraft bus system has the errors of more than about 10-15 arcmins due to the time offset problem and errors in attitude knowledge. We develop an algorithm for correction of position errors in FIMS data. The aspect for the FIMS data is determined by comparing the positions of observed bright stars with the Tycho-II and TD-1 catalogs. The position errors of the bright stars along the scanning (<TEX>${\gamma}$</TEX>) and spatial (<TEX>${\delta}$</TEX>) directions were considered as functions of <TEX>${\delta}$</TEX>, ignoring errors in position angle. The corrected positions of the bright stars coincided very well to their Tycho-II and TD-I positions. The correction algorithm is essential for the FIMS data analysis, and is being used for the FIMS data analysis.

Systematic Errors in Double Star Observations

AbstractWe have examined the visual and speckle observations of visual double stars made by 31 experienced observers in order to evaluate possible systematic errors in these series. Using 57 “definitive” orbits, we find no appreciable errors in position angle. We do find systematic effects in separation for some observers, and, in particular, a “proximity” effect for measurements of pairs closer than 0″.5.Root-mean-square residuals are: