Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Phase comparison
Reexamination Certificate
1999-11-09
2003-11-04
Sherry, Michael (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Phase comparison
C324S076110, C324S107000
Reexamination Certificate
active
06642702
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a detection circuit for a maximum amplitude value of a 3-phase signal in a position detector which converts a 3-phase signal to digital values and detects a position. In particular, it relates to a detection circuit for a maximum amplitude value of a 3-phase signal and a detection method of a maximum amplitude value of a 3-phase signal.
There is a position detector which inputs a 3-phase signal and converts it to digital values with an analog/digital converter (hereinafter referred to as an A/D converter), and detects a distance from an approximation straight line using these digital values.
A position detection method of a position detector will be explained in the following.
FIG. 3
shows an illustrative drawing for explaining the waveforms of 3 phase-signals having 120° degrees difference in phase from each other. For example, a detection method for measuring a distance to a position in which 1 period of a signal emanating from that position is divided into 6 parts and the distance is detected in regarding the amplitude values as an approximation straight line will be explained. For example, assuming that 1 period (SIN &thgr;) is 264 &mgr;m, 1 period divided by 6 gives 44 &mgr;m. In this case, the amplitude values can be approximated by a straight line 0 in FIG.
3
. The distance from 0 to point “a” on the approximation straight line is 44 &mgr;m, and when the amplitude value (in this case, SIN(&thgr;−120°)) obtained by A/D conversion is divided by the above-mentioned distance 44 &mgr;m, the amplitude value per 1 &mgr;m can be obtained.
In this detection method, an amplitude is converted to a distance, so that the detection of the maximum value of an amplitude is necessary. If the maximum value is not detected accurately, an error may occur in the measurement of the distance.
As a detection method of a maximum value of an amplitude, there is a method in which a sampling technique is utilized.
FIG. 4
is an illustrative drawing showing the relation between the waveform of a signal and the sampling operation. The signal is sampled at a predetermined sampling period and the maximum value in the sampled values is taken as the maximum amplitude value.
However, there has been a problem in a conventional position detector that an accurate maximum amplitude value is difficult to obtain.
As mentioned above, in a detection method of a maximum value of an amplitude, where sampling is performed at a predetermined sampling period, the relation between the sampling period and the moving speed of a sensor becomes an important factor. As shown in
FIG. 4
, in a case where a sampling period is not properly chosen for the waveform of a signal, the maximum value is not always detected. For example, the mainstream of A/D converters in these days is the delta sigma type being comparatively low cost. However, with the delta-sigma type, the sampling period is rather long and the moving speed of a sensor has to be lowered to detect the maximum value accurately. In order to raise the moving speed of a sensor, a high speed A/D converter has to be used, which will cause a high manufacturing cost of the apparatus.
There has been a method in which at the time of shipment or when a sensor is exchanged for another, the maximum value is detected and memorized beforehand; however, actually, the maximum value is varied by various causes, such as the ON/OFF of a power supply at the time of measurement, fluctuation of a power supply voltage or aged deterioration. Therefore a detection circuit of a maximum amplitude value having an automatic corrector function has been awaited.
SUMMARY OF THE INVENTION
The present invention is provided considering the above-mentioned circumstances, and the object of the invention is to offer a detection circuit for a maximum amplitude value of a 3-phase signal and a detection method of a maximum amplitude value of a 3-phase signal.
In the present invention, in order to solve the above-mentioned problem, a detection circuit of a maximum amplitude value of a 3-phase signal composing a position detector converting the 3-phase signal into digital values and detecting a position is provided with: a comparison means for comparing the values of respective phase-signals in a 3-phase signal and a maximum amplitude decision means for deciding the value of one phase-signal as the maximum amplitude value, when the values of any two phase-signals among three phase-signals coincide with each other.
In the detection circuit of a maximum amplitude value of a 3-phase signal having the configuration as mentioned above, the values of respective phase-signals are compared by a comparison means, and it is detected whether the values of any two phase-signals among three phase-signals coincide with each other or not, and the result is output to the maximum amplitude value decision means. In a case where the values of any two phase-signals among three phase-signals coincide with each other, the value of the remaining 1 phase-signal is taken as the maximum amplitude value by the maximum amplitude decision means and it is memorized or output to the following process block.
In a detection method of a maximum amplitude value of a 3-phase signal composing a position detector for converting the 3-phase signal to digital values and detecting a position, the values of three phase-signals are compared with each other, and when the values of any two phase-signals coincide with each other, the value of the remaining 1 phase-signal is taken as the maximum amplitude value.
In the detection method of the maximum amplitude value of a 3-phase signal having such process procedures as mentioned above, the values of three phase-signals are compared with each other for detecting whether values of any 2 phase-signals coincide with each other or not. In the result, when any two phase-signals among three phase-signals coincide with each other, the value of the remaining one phase-signal is taken as the maximum amplitude value and it is memorized or output to the following process block.
REFERENCES:
patent: 4815002 (1989-03-01), Verbanets
patent: 5153821 (1992-10-01), Blasko
patent: 5345409 (1994-09-01), McGrath et al.
“Fundamental of electrical Engineering: Principles and Applications” by Thomas J. Cavicchi, 1993 by Prentice-Hall, Inc. (pp. 280-287).
Kananen, Esq. Ronald P.
Patel Parresh
Rader & Fishman & Grauer, PLLC
Sherry Michael
Sony Corporation
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