Coded data generation or conversion – Phase or time of phase change – Synchro or resolver signal
Patent
1990-01-26
1992-06-09
Logan, Sharon D.
Coded data generation or conversion
Phase or time of phase change
Synchro or resolver signal
341113, H03M 122
Patent
active
051211165
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an absolute position encoder and, more particularly, to an absolute position encoder capable of detecting, as an absolute position, the rotational position of a rotary shaft of a motor or the like which drives a machine tool, etc.
Description of the Related Art
In general, an absolute position encoder has a rotary coding disk fixed to a rotary shaft and a plurality of slit arrays (channels) in accordance with binary notation or Gray binary notation provided in conformity with the resolution desired, and the rotational position of the rotary coding disk is detected as an absolute position by detecting, by means of a light-receiving element (photoelectric transducer element) an amount of light from a light-emitting element that has passed through each channel formed in the rotary coding disk and a stationary slit opposing each channel.
In order to increase detecting precision (resolution), it is necessary to increase the number of channels. For example, in order to detect angular information in which one revolution is divided into 4096, i.e., 2.sup.12, parts, it is required that the number of channels be 12 (a 12-bit code is necessary), thus necessitating a coding disk of a correspondingly large size.
In order to avoid this problem, it has been considered to provide the rotary coding disk with sinusoidal patterns in a plurality of channels so as to obtain a plurality of sinusoidal outputs having different cycles per revolution (e.g., a pattern through which one cycle of a sinusoidal output is obtained per revolution is provided as a first channel, a pattern through which 16 cycles of a sinusoidal output is obtained per revolution is provided as a second channel, and a pattern through which 256 cycles of a sinusoidal output is obtained per revolution is provided as a third channel), interpolate the angular information in one wavelength of each channel 16 items at a time, and successively combine the interpolated data of each channel thus obtained, whereby the rotational position of the coding disk is detected as an absolute position.
In such a case, the number of channels for obtaining the same resolution is smaller than that needed in a case where the channels are formed in accordance with the above-mentioned binary methods (e.g., in order to perform detection by dividing one revolution into 2.sup.12 parts, three channels will suffice, as set forth above), thereby making it possible to reduce the size of the rotary coding disk.
FIG. 2 exemplifies an absolute position encoder adapted to detect the angular information of such a rotary coding disk, in which the rotary disk used has plural channels of sinusoidal patterns the numbers of cycles whereof differ. FIG. 2 illustrates a case in which, in addition to the above-mentioned first, second and third channels (represented by 1.lambda., 16.lambda. and 256.lambda., respectively), there is provided a fourth channel (represented by 4096.lambda., by which a sinusoidal output of 4096 cycles is obtained), wherein the inputs are sinusoidal signals 1.lambda. sin, 16.lambda.sin, 256.lambda.sin and 4096.lambda.sin from the respective channels and cosinusoidal signals 1.lambda.cos, 16.lambda.cos, 256.lambda.cos and 4096.lambda.cos having an electrical phase difference of 90.degree. relative to respective ones of the sinusoidal signals. By way of example, the cosinusoidal signals are obtained by using a light-receiving element to detect and photo electrically convert light which has passed through a stationary slit electrically displaced by 90.degree. from the stationary slit for the sinusoidal signals.
Numerals 11 through 14 denote amplifiers for amplifying respective ones of the sinusoidal signals 1.lambda.sin through 4096.lambda.sin, 21 through 24 analog switches for channel selection connected to the output sides of respective ones of the amplifiers 11 through 14, 16 through 19 amplifiers for amplifying the cosinusoidal signals 1.lambda.cos through 4096.lambda.cos, and 26 through 29 anal
REFERENCES:
patent: 3816825 (1974-06-01), Kaneko et al.
patent: 4445110 (1984-04-01), Breslow
patent: 4524347 (1985-06-01), Rogers
patent: 4786891 (1988-11-01), Ueda et al.
patent: 4998105 (1991-03-01), Takekoshi et al.
Fanuc Ltd.
Logan Sharon D.
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