Automatic compensation system for eccentricity error of absolute optical encoder.

In industrial plants with dynamically varying load profiles, the problem of increased charges for over-contracted reactive power consumption is very common. To eliminate these charges, reactive power compensation systems are used. This article presents a case study of an automatic reactive power compensation system in an underground mine where a thyristor hoisting machine is used. To reduce the higher current harmonics of the hoisting machine and compensate for the reactive power of the PCC (Point of Common Coupling), the main reactive power automatic compensation system and an ASVG (Advanced Static Var Generator) with a nonstandard control loop were used. The article considers aspects of the operation of the ASVG, locally with the hoisting machine, and also as a master-controlled device that is part of the reactive power automatic compensation system. This part of the article is based on measurements taken in a mine. The reactive power automatic compensation system considered in this article has been successfully implemented, improving PQ (Power Quality) and eliminating additional overcompensation charges.

Eccentricity error is the main error source of rotary encoder. In our previous work, a novel polar coordinate encoder has been presented for eccentricity self-detection and error compensation. In this paper, an improved eccentricity self-detection method based on least square algorithm is presented. We first establish the radial displacement equation in terms of rotary angle and eccentricity. Then, overdetermined equations can be constructed by taking sampling points into radial displacement equation, from which the optimal solution of eccentricity can be determined using least squares algorithm. Thus, angle compensation can be performed by submitting the calculated eccentricity into eccentricity error model. The proposed method offers a new strategy for automatic eccentricity self-detection and angle compensation of rotary encoder. Both simulation analysis and experimental test are performed to prove the effectiveness of the proposed method.

Protecting iron and steel from corrosion : Anon. ( Brass World, viii, 8, 272)

With the continuous development of manufacturing industry, the application range of NC machining technology has been further expanded. The contour accuracy is strongly related to the NC machining quality as a key machine tool performance indicator. Its application efficiency is plainly low as the majority of offline compensation-based contour accuracy adjustments rely heavily on manual experience. Moreover, the isolated research on automatic error compensation and its combination with algorithms does not start with the characteristics of contour accuracy in data processing. Therefore, based on the advantages of strong the robustness of the fuzzy algorithm and the high effectiveness of parameter adjustment, an automatic compensation method for NC machining contour error based on fuzzy control is proposed. The contour error prediction model is designed according to the machining path, and then the automatic compensation strategy for contour error under fuzzy control is designed based on the feed speed. The results showed that under this method, the contour error can reach a maximum of 0.06 and a minimum of 0.025, which was 0.015 lower than the minimum contour error of genetic algorithm. This indicated that the method greatly reduced the CNC machining contour error and improved the contour accuracy, as well as reducing the time cost of contour error compensation, improving the efficiency of contour error compensation, and realizing the automation of error compensation control capability. This is helpful for advancing CNC machining automation technology and supporting the intelligent development of machinery manufacturing.

Circular features are very common in geometric camera calibration. The projection of a circular feature is generally a deformed ellipse, not a true ellipse, due to the presence of lens distortion. The center of the deformed ellipse, obtained by fitting the boundary points with an ellipse, does not necessarily coincide with the distorted point corresponding to the center of the undistorted projection of the circular feature. An eccentricity error will be introduced if the two points are considered to be coincident. In this study three main factors that affect the amount of the eccentricity error are discussed, including the form and amount of lens distortion, the size of the circular feature and the tilt of the supporting plane. Then, an effective geometric camera calibration method is proposed where the eccentricity error is compensated by establishing the correspondence between the estimated model position and the real position of the fitted center of the deformed ellipse. Both simulation and measurement data verify the existence of the eccentricity error and the effectiveness of the proposed method.

Subdivision errors and long-period errors are the main components of small absolute optical encoder error. When the external environment changes or the encoder operates for a long time, the subdivision error will increase. In this study, a stepper motor and high-precision encoder are used to develop a system that automatically measures the long-period error and subdivision error of a small optical encoder. The error data are fitted and stored in the program memory of the encoder in the form of an error data table. During the displacement calculation, the encoder collects the peak and valley values of fine-coded two-channel moiré fringe signals in real time, normalizes the moiré fringe signal data, and compensates for the subdivision error and long-period error by looking up data in the table. A 16-bit small encoder was tested using the developed system, and the mean square errors of the encoder before and after compensation were <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$43.3^{\prime \prime }$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11.7^{\prime \prime }$ </tex-math></inline-formula>, respectively. Therefore, the algorithm proposed herein can significantly improve the measurement accuracy of small optical encoders.

A polar-coordinate optical encoder that can realize synchronous measurement of angular and radial displacements is introduced. It has potential application in concurrent monitoring of radial and angular motions for rotating spindles and in real-time detection and compensation of eccentricity error for rotary stages. We explain its operating principle and develop a prototype. Experimental results demonstrate the feasibility and effectiveness of the proposed optical encoder in polar-coordinate displacement measurement.

This paper deals with the realization of the four-pair terminal definition of impedance standards. A simple though reliable system is described that allows an automatic compensation of the voltage at the low potential port of impedance standards to be obtained. Such a system, which employs a commercial DAQ board and an arbitrary signal generator, is controlled through a standard PC that implements the demodulation and the control algorithms. Preliminary tests have been performed in the frequency range of 50 Hz to 20 kHz with different kinds of impedance standards (resistive, inductive and capacitive), obtaining a residual voltage at the low potential port of less than 5 /spl mu/V.

To evaluate the feasibility of applying electronic current transformer(ECT) with double non-magnetic air gaps to on-site mobile comparison systems, we analyzed ECT from two aspects, namely its steady-state accuracy and its stability after multiple times of installations. Regarding the steady-state accuracy, we reduced the ratio error and the phase error of the ECT though optimizing the core parameters and some error compensation measures. Test results proved that the ECT with double air gap core could achieve level 0.2 of the National Standards of China. Meanwhile, the measurement stability was studied from two aspects, namely the ratio error and phase error caused by varying length of the non magnetic air gap, and lowering the eccentric distance error. Test results of the ratio error and phase error versus the gap length indicate that maintaining the measurement accuracy requires to strictly control the installation. Moreover, regarding the large eccentric distance error of the ETC with single iron core, we proposed to use two series connected cores with double air gaps, and the theoretical analysis and experimental results proved it to be quite effective. However, according to the results, applying the ECT with double non-magnetic air gaps requires further improvement of the ECT in accuracy.

The errors existing in photoelectric theodolite were studied according to the error design idea , that is，the correction of theodolite errors was achieved by analyzing the effect of errors actively instead of processing the data with error passively. Aiming at the shafting error, the relationship between different errors was analyzed by the error model based on coordinate transformation, and the real-time error compensation method based on the normal-reversed measuring method and levelness auto-detection was supposed. As to the eccentric error of dial, the idea of eccentric residual error was presented and its influence to measuring precision was studied, then the dynamic compensation model was build, so the influence of eccentric error of dial to measuring precision can be eliminated. For the centering deviation in the process of measuring angle, the compensation method based on the error model was supposed, in which the centering deviation was detected automatically based on computer vision. The above method based on error design idea reduced the influence to measuring result by software compensation method effectively, and improved the automation degree of azimuth angle measuring of theodolite, at the same time the precision was not depressed.

Currently, commercial encoders endowed with high precision are expensive sensors, and optical low-cost designs to measure the positioning angle have undesirable levels of system noise which reduce the good performance of devices. This research is devoted to the designing of mathematical filters to suppress noise in polarized transducers, in order to obtain high accuracy, precision, and resolution, along with an adaptive maximum response speed for low-cost optical encoders. This design was proved through a prototype inside a research platform, and experimental results show an accuracy of 3.9, a precision of 26, and a resolution of 17 [arc seconds], at least for the specified working conditions, for the sensing of the angular position of a rotary polarizer. From this work has been obtained a high-performance low-cost polyphase optical encoder, which uses filtering mathematical principles potentially generalizable to other inventions.

Laser cutting focus position automatic tracking system of control precision directly affects the quality of laser cutting processing. There is a low anti-jamming capability, poor quality,poorer openness and poorer dynamic response short comings in the inductive sensor or the capacitive sensor and constitute of the single chip microcomputer control system. This paper introduces a laser focus automatic tracking system based on motion controller, using optical encoder as displacement sensor, use the motion controller of master-slave tracking (electronic gear) function implementation focus position error compensation quickly. Improve the quality of system control, openness, the stability and reliability.

The technological manipulation of the piezo-electric actuator could compensate for the errors of the machining precision during the process of machining which lead to an elevation and enhancement in overall precisions. This manipulation is a very convenient method to advance the precision for nations without the solid knowledge of the ultra-precision machining technology. There were 2 divisions of researches conducted to develop the UPCU for precision enhancement of the current lathe and compensation for the environmental errors as shown below; The first research was designed to measure and real-time correct any deviations in variety of areas to achieve a compensation system through more effective optical fiber laser encoder than the encoder resolution which was currently used in the existing lathe. The deviations for a real-time correction were composed of followings; the surrounding air temperature, the thermal deviations of the machining materials, the thermal deviations in spindles, and the overall thermal deviation occurred due to the machine structure. The second research was to develop the UPCU and to improve the machining precision through the ultra-precision positioning and the real-time operative error compensation. The ultimate goal was to improve the machining precision of the existing lathe through completing the 2 research tasks mentioned above.

The use of automatic error detection and compensation techniques for testing the class cBigNumber written in C++ is discussed; this class is designed for performing operations on unbounded integer numbers. It implements the standard operations of C++, square rooting, binary exponentiation, and Miller-Rabin primality test. The class is tested in the automatic mode. The reliability of computations is ensured using the built-in error control and compensation tools.

An automatic feedback spectral-phase compensation system using the wavelet transformation method for the M-SPIDER signal analysis has been developed. The system is completely free from the manual operation and generates 9.6-fs pulses after chirp compensation.KeywordsOptical PulseSpatial Light ModulatorSpectral PhasePhase CompensationGroup Delay DispersionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.