JPH04136715A - Encoder - Google Patents

Abstract

PURPOSE:To enable a position to be detected with an improved reliability with less erroneous detection by selecting an accurate signal and then detecting an absolute pattern based on interpolation position information out of a signal group which is selected at plurality of locations with a different phase. CONSTITUTION:An interpolation position signal detection means consists of a gear 2, magnetic sensors 4a and 4b, a sample-and-hold circuit 10, an analog/ digital conversion circuit 11, and a arithmetic operation circuit 12 and outputs and interpolation position operation circuit 12 and outputs an interpolation position signal which is the absolute position theta within a gear. Sample-and-hold circuits 135a - 136d of absolute pattern signal detection means take an instantane ous value of an output signal of magnetic sensors 5a-5d and 6a-6d and comparators 145a - 146d digitize these signals. A pattern signal selection means 15 selects either an output signal group D5a - D5d or D6a - D6d from a comparator 14 according to the position information theta of the interpolation position signal. An adder 17 outputs a signal which is obtained by adding an upper digit position signal PUP and the interpolation position signal theta, thus achieving detection of the absolute position of the object to be detected highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an encoder, and particularly to an absolute type encoder.

(Prior Art) In a conventional absolute encoder, a gray coat or the like is used as an absolute pattern for directly detecting the position of an object to be detected. Furthermore, there is another conventional absolute type encoder as shown in FIG. In the encoder shown in the figure, a gear 2 made of a magnetically permeable material and a disk 3 made of a magnetically permeable material having a pattern according to a binary cyclic random number sequence on its outer periphery are attached to a rotating body 1, and a permanent magnet ( The magnetic sensors 4a, 4b and 105a-105d each have a gear 2 (not shown).
and is arranged at a certain distance from the outer periphery of the disk 3. Two-phase AC signals ε,=V are output from the magnetic sensors 4a and 4b.
sinθ+ν, Eb=Vcosθ+V, are output, and signals corresponding to the outer peripheral shape of the disk 3 are output from the magnetic sensors 105a to 105d. Sample-and-hold (S/H) circuits 13a-13d capture instantaneous values of output signals from magnetic sensors 105a-105d, respectively, and comparators 14a-146 binarize these instantaneous values, respectively. The random number conversion circuit 16 manually converts the binary cyclic random number codes outputted from the comparators 14a-14d into a high-order digit signal PUP, which is the high-order digit of the absolute position information, based on the correspondence shown in FIG. Each signal Eb detected by the magnetic sensors 4a and 4b
, Eb are sample-and-hold circuits 10a, l
ob and the analog/digital conversion circuits 11a and llb convert the signals into digital signals, and the arithmetic circuit 12 performs the calculation of equation (1).

The adder circuit 17 receives the interpolation signal which is the absolute position θ within one tooth of the gear 2 calculated in this way and the above-mentioned upper digit signal pup.
By outputting a signal obtained by adding these signals, the absolute position of the rotating body, which is the object to be detected, is detected with high precision.

(Problem to be Solved by the Invention) However, in the conventional encoder using a Gray code or the like as the above-mentioned absolute pattern, in order to improve the detection resolution, it is necessary to increase the number of absolute patterns. Accordingly, the number of tracks increases, making it difficult to miniaturize the device and making the structure complicated.

On the other hand, in the case of the encoder shown in FIG. 4 that uses a binary cyclic random number code, the absolute pattern has a small number of tracks and has high resolution, but the output signals of the magnetic sensors 105a to 105d that detect the absolute pattern are As shown in FIG. 2(C), the followability at the portion where the shape of the disk changes is poor, and the signal does not show any steep changes. Therefore, when the timing at which position information is read occurs at a portion where the shape of the disk changes, the threshold voltage V of the comparators 14a to 14d. Since the output signal voltages of the magnetic sensors 105a to 105d are close to each other, there is a possibility that the absolute pattern may be erroneously detected due to variations in the processing accuracy and mounting accuracy of the disk, and differences in the characteristics of the comparator, sensor element, etc., making it unreliable. There was a problem with low gender.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to reduce the number of absolute pattern tracks to miniaturize the device, and to achieve high reliability with high resolution and few false detections. The object of the present invention is to provide an encoder having the following functions.

(Means for Solving the Problems) The present invention particularly relates to an absolute type encoder, and the above object of the present invention is to detect an absolute pattern provided on either a moving part or a fixed part with respect to an object to be detected. absolute pattern signal detection means for detecting a plurality of sets of absolute pattern signals by reading them at positions in different directions; interpolation position detection means for generating an interpolation position signal which is a digit; selection means for selecting one set of the plurality of sets of absolute pattern signals based on the interpolation position signal; This is achieved by comprising a conversion means for converting the absolute pattern signal obtained by the above-mentioned position information into the upper digits of the position information, and a calculation means for calculating the position of the detected object from the upper digit signal and the interpolated position signal. be done.

(Function) In the present invention, the absolute pattern is detected at a plurality of locations, and based on the position information of the interpolated position signal, the absolute pattern is detected at a position that avoids the changing part of the pattern.
By always selecting the signal whose pattern is being detected, an accurate absolute pattern is determined and the upper digit position signal is detected, which reduces false detection and improves reliability.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of an encoder according to the present invention. In the figure, a gear 2 made of a magnetically permeable material and a disk 3 having a pattern according to a binary cyclic random number sequence on the outer circumference are attached to a rotating body 1, and a magnetic Sensors 4a and 4b are connected from the outer periphery of gear 2,
Further, the magnetic sensors 5a to 5d and 6a to 6d are arranged at a certain distance from the outer periphery of the disk 3, respectively.

The interpolation position signal detection means is gear 2. Magnetic sensor 4a, 4
b, sample-and-hold circuit 10 analog/
It consists of a digital conversion circuit 11 and an arithmetic circuit 12. The magnetic sensors 4a and 4b receive a two-phase AC signal Ell=Vsinθ
+Vo, Eb, = Vcosθ+vo are output, and this two-phase AC signal is converted into a digital signal by the sample-and-hold circuit IO and the analog/digital conversion circuit 11. The arithmetic circuit 12 performs the arithmetic operation shown in equation (2) to output an interpolated position signal that is the absolute position θ within the gear plane.

On the other hand, the absolute pattern signal detection means is the disk 3
．． Consisting of magnetic sensors 5a to 5d, 6a to 6d, sample and hold circuit 135a''l36 (1) and comparators 145a to 146d, magnetic sensors 5a to 5d6a to 6d alternate with the pitch of one tooth of gear 2 being λ. are arranged at positions separated by λ/, respectively.

With such an arrangement, the magnetic sensors 5a to 5d, 6a to 6
The output signals of d are signals having phases different from each other by 180°, assuming that one period of the interpolated position signal is 36°. Moreover, the magnetic sensor 4a and the magnetic sensor 5a are arranged on the same straight line in the axial direction of the rotating shaft. Sample-and-halt circuits 1353-136. The magnetic sensors 5a to 5d are connected at the same timing as the sample and hold circuit IO.
, 5a to 6d, and comparators 145 . ~146d are two of these signals
Perform valorization. The pattern signal selection means 15 selects either the output signal group DSa"'D5d or D6a to D6d from the comparator 14 according to the position information θ of the interpolated position signal. In other words, the position information θ of the interpolated position signal
When o"<θ≦90", D6a to D6d, 90'
<θ≦270” Notokiha D5a~D5d, 270”
<θ≦380"), select D6. to D6d. As shown in FIG. The adder 17, which is an arithmetic means, converts the high-order digit position signal PUP into a position signal and outputs it as a high-order digit position signal PUP.
A signal obtained by adding UP and the interpolated position signal θ is output, and the highly accurate absolute position of the detected object is detected. The selection of the absolute pattern will now be explained in more detail with reference to FIG. FIG. 2(A) shows the magnetic sensor 4a.

4b and a part of the outer periphery of the gear 2, and FIG.
) is a diagram showing the magnetic sensors 5a to 5d, 6a to 6d and a part of the outer periphery of the disk 3, and FIG. 2(C) is a diagram schematically showing the output signals from the magnetic sensors. As shown in FIG. 2(C), the output signal of the magnetic sensor generally does not show a sharp change even if the outer peripheral shape of the absolute pattern detection disk changes sharply. Therefore, when the timing to read the position information comes to this changing part, the threshold voltage V of the comparator. Since the voltages of the output signals of the magnetic sensors 5a to 5d become close to each other, there is a possibility that the absolute pattern may be misread. However, at this time, since the magnetic sensors 6a to 6d are sufficiently far away from the shape-changing portion of the disk 3, the output voltages of the magnetic sensors 6a to 6d are at voltage levels sufficiently far from the threshold voltage v0. In this case, output signals 56a- from the magnetic sensors 6a to 6d are used as absolute pattern signal detection signals.
If 56d is used, an accurate absolute pattern can be detected. Therefore, if one of the magnetic sensors is appropriately selected according to the value of the interpolated position signal θ, an accurate absolute pattern can always be detected. That is, 0° θ≦90
°, the signals Sea to S6 of the magnetic sensors 8a to 6d
d, when 90° and θ≦270°, the magnetic sensor 5a~
When 270° and θ≦360°, the signals S6a to Saa of the magnetic sensors 6a to 6d may be carried and used.

In the above embodiment, the case where the magnetic sensor 4a and the magnetic sensor 5a are in phase has been explained, but the present invention is not limited to this, and the mounting of the gear 2 and the disc 3 may depend on the state of the magnetic sensor. Even if the phases of 4a and 5a are shifted, record the phase shift! ! The value of the interpolated position signal θ can be determined by storing it in an element or the like and adding or subtracting this phase deviation from the interpolated position signal θ.

In addition, in the embodiment, the case has been explained where the pressure detection cycle of the interpolation position signal and the pattern width of the absolute pattern match, or the detection cycle of the interpolation position signal may be an integral multiple of the pattern width of the absolute pattern. .

Furthermore, in the embodiments of the present invention, the case of a binary cyclic random number sequence has been explained as an absolute pattern for detecting the upper digits of position information, but other absolute patterns may also cause erroneous detection in the changing part of the pattern. Applicable if the possibility is great.

Further, in the above embodiment, a rotary encoder for reading a rotational position using a magnetic sensor was described, but the present invention can read a linear position by linearly passing an absolute pattern and an interpolated position detection pattern. It can also be applied to linear encoders for

Further, the present invention is not limited to the magnetic sensor mentioned in the embodiment, and can be applied to other detection methods. For example, by magnetizing a tram,
The present invention can also be applied to encoders that employ a method of detecting this magnetization using a magnetic sensor, or a method of detecting upper digit position signals and interpolated position signals using an optical detection method or the like.

(Effects of the Invention) As described above, according to the encoder of the present invention, an absolute pattern is detected at multiple locations with different phases, and interpolation is performed from among the signal groups detected at multiple locations with different phases. By selecting accurate signals and detecting absolute patterns based on position information, highly reliable position detection with fewer false positives is possible. Furthermore, when a binary cyclic random number sequence is used as the absolute pattern, the number of tracks is reduced, making it possible to perform compact and highly accurate position detection.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the encoder of the present invention,
FIG. 2 (A+ is a diagram showing a part of the outer periphery of the magnetic sensors 4a, 4b and the gear 2, FIG. 2 (B) is a diagram showing the magnetic sensors 5a to 5d,
6a to 6d and a diagram showing a part of the outer periphery of the disk 3, the same figure (C)
3 is a diagram showing an output signal of a magnetic sensor, FIG. 3 is a diagram showing an example of an absolute iodine pattern, and FIG. 4 is a diagram showing the configuration of a conventional encoder. 1... Rotating body, 2... Gear, 3... Disk, 4a,
4b, 5a-5d, 6a-6d, 105a-105
d... Magnetic sensor, 10.13... Sample and halt circuit, Il... Analog/digital conversion circuit, 12... Arithmetic circuit, 14... Comparator, 15... Pattern signal selection Means, 16... Random number conversion circuit, 17... Adder. 44# 0 mouth (A) 5a 6a 5k h jc 6c 5d
6d0 0 mouth 000[1[](B) ((')

Claims (1)

[Claims] 1. Absolute pattern signal that detects a plurality of sets of absolute pattern signals by reading an absolute pattern provided on one of a moving part or a fixed part with respect to the detected object at different positions in the detection direction. a detection means; an interpolation position detection means for detecting information having a cycle that is an integral multiple of the minimum pattern width in the detection direction of the absolute pattern signal and generating an interpolation position signal that is a lower digit of the position information; Selection means for selecting one of the plurality of sets of absolute pattern signals based on the interpolated position signal; and conversion means for converting the absolute pattern signal selected by the selection means into upper digits of the position information. and a calculation means for calculating the position of the detected object from the signal of the higher order digits and the interpolated position signal. 2. The interpolation position detection means detects a two-phase alternating current signal E_a=Vs having a periodic waveform according to the moving distance of the moving part.
Detect the instantaneous value of inθ+V_o, E_b=Vcosθ+V_o, and further lower digit θ=tan^-^1((E_a-V_o)/(E_b-
2. The encoder according to claim 1, wherein the selection means selects the set of absolute pattern signals based on the value of the lower digit θ of the position information. 3. The encoder according to claim 1, wherein the absolute pattern is a pattern that follows a binary cyclic random number sequence. 4. The absolute pattern signal detection means outputs two sets of absolute pattern signals detected at positions 1/2 apart from each other with respect to the absolute pattern width in the position detection direction as a reference. Encoder listed.