JPH0438284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a displacement detection circuit for an encoder suitable for use in detecting displacement.

"Prior Art" Various circuits have been developed and put into practical use for detecting displacement by demodulating the output signal of an encoder for displacement detection. FIG. 3 is a circuit diagram showing an example of this type of displacement detection circuit for an encoder, and the circuit shown in this figure will be explained below.

In FIG. 1, 15 is a scale, which is constructed by magnetizing a predetermined orbit with a sine wave of a constant period. Scale 15 in this case
is constructed by setting a circular orbit on the surface of a disc-shaped magnetic material and magnetizing this circular orbit. Further, the wavelength λ of the sine wave used for magnetization is set to about several + to several hundred μm. Magnetic sensors 16 and 17 output level signals corresponding to the strength of magnetization on the scale 15. That is, as the magnetic sensors 16 and 17, those whose output signals do not include a carrier wave are used, and for example, sensors using semiconductor elements are used. Moreover, the magnetic sensor 17 is 1/4λ (90°) with respect to the magnetic sensor 16.
It is set to shift. Therefore, the interval between the magnetic sensors 16 and 17 is set to (m±1/4)λ (where m is a positive integer). The magnetic sensors 16, 17 and the scale 15 are relatively movable, so that if one of them is fixed, the other rotates. As can be seen from the above, if the signal output by the magnetic sensor 16 is a sine wave, the signal output by the magnetic sensor 17 is a cosine wave.
It becomes a wave. Therefore, the interval of one cycle of the magnetization sine wave (from pole to pole of scale 15) is θ=0~
2π, the output signals of the magnetic sensors 16 and 17 are sin θ and cos θ, respectively.

Next, 18 and 19 shown in FIG. 3 are A/D converters that convert the output signals of the magnetic sensors 16 and 17 into digital signals, respectively, and the digitized sinθ
and cos θ are supplied to one input terminal of digital multipliers 20 and 21. The output signals of the multipliers 20 and 21 are supplied to one and the other input terminals of a digital subtracter 22, respectively, and the output signal of the subtracter 22 is supplied to a digital comparator 23. This digital comparator 23 becomes "1" if the subtraction result of the subtracter 22 exceeds 0, and "0" if it does not exceed 0.
The U/ signal is supplied to the up/down switching terminal U/ of the counter 24. The counter 24 counts the clock signal CK, and counts up when a "1" signal is supplied to the up/down switching terminal U/, and counts down when a "0" signal is supplied. Next, 25 is a function generation
It is a ROM and outputs sine and cosine data corresponding to the count value Φ of the counter 24. That is, in the function generation ROM 25,
Data of sin Φ and cos Φ are stored, and the stored data are read out sequentially according to the count value Φ. And data
cos Φ is supplied to the other input of digital multiplier 20 and digital sin Φ is supplied to the other input of digital multiplier 21 . According to the above configuration,
The output of the subtracter 22 is sin(θ-Φ). Therefore, the comparator 23 sets the U/ signal to "1" when the value of sin (θ-Φ) is positive, and sets the U/ signal to "0" when it is negative, and as a result, the count value of the counter 24 Φ increases or decreases depending on the sign of sin(θ−Φ).

Next, 30 and 31 shown in FIG. 3 convert the output signals of the magnetic sensors 16 and 17, respectively, into binary signals of "1" level and "0" level by determining them with a predetermined threshold value. It is a waveform shaping circuit. In this case, the output signals P ₁ of the waveform shaping circuits 30 and 31,
P ₂ is configured to be a rectangular wave with a phase shift of π/2, and the magnetic sensors 16 and 17
When the movement is in the positive direction, the pulse P ₁ advances, and when the movement is in the negative direction, the pulse P ₂ advances. Reference numeral 33 denotes a direction discrimination circuit that discriminates the moving direction of the magnetic sensors 16 and 17. For example, the direction is discriminated depending on whether the level of the pulse P ₂ at the rising edge of the pulse P ₁ is "1" or "0". I have to. The output signal of this direction discrimination circuit 33
_SW is supplied to the up/down switching terminal of the counter 34 and output to the outside. The counter 34 is configured to count the pulses _P1 while switching between up and down depending on the signal _SW . In this embodiment, an up count is performed when the magnetic sensors 16 and 17 are moving in the positive direction, and a down count is performed when the magnetic sensors 16 and 17 are moving in the negative direction. Moreover, the magnetic sensors 16 and 17 are connected to the scale 1.
Every time the counter 5 rotates once, the 0 point signal S _Z output at the reference position becomes a 0 point pulse P _Z after passing through the waveform shaping circuit 32, and this 0 point pulse P _Z is sent to the reset terminal R of the counter 34. As a result, the counter 34 is reset each time the magnetic sensors 16, 17 reach the reference position. Therefore, the count value of the counter 34 is the number of magnetic sections (the number of magnetic poles) on the scale 15 that the magnetic sensors 16, 17 have passed between the current position of the magnetic sensors 16, 17 and the reference position.
The value corresponding to

The output signal N of the counter 34 constitutes the data of the upper bits of the displacement data Dout, and the count value Φ of the counter 24 constitutes the data of the lower bits of the displacement data Dout.

According to the configuration described above, the magnetic sensors 16, 17
When Dout moves in the positive direction, the counter 34 counts up every time the magnetic sensors 16 and 17 pass through a magnetic section (magnetization pitch), and this count value is output to the upper bit of the data Dout.
Therefore, if we look at the upper bits of the data Dout, we can see how many magnetization sections the magnetic sensors 16 and 17 have passed through, that is, the current magnetic sensors 16 and 17.
17 is located from the reference position.

Further, the signals Sinθ and cosΦ output from the magnetic sensors 16 and 17 are transmitted to the A/D converters 18 and 19, respectively.
After being converted into a digital signal by
It is multiplied by the signals cosΦ and sinΦ output from the ROM 25, and these multiplication results are supplied to the subtracter 22.
sin(θ−Φ) is detected. And this sin(θ
-Φ) The count value φ of the counter 24 increases or decreases depending on the positive or negative value of the value φ), and a function is generated according to the count value φ.
The ROM output sinΦ and cosΦ increase or decrease. As a result,
The circuit shown in FIG. 3 is a phase-locked loop in which the value of sin(θ-Φ) is 0, that is, θ=Φ. Therefore, counter 2
The count value Φ of 4 is data indicating where the magnetic sensor 16 is located within the magnetization section. In this case, if the number of bits of the counter 24 is 8 to 10 bits, the detected position resolution based on the count value Φ is:
The accuracy is about 1/256 to 1/2048 of one magnetization section.

"Problems to be Solved by the Invention" By the way, in the circuit described above, if the speed of the detection target is extremely slow and the frequency of the input signal supplied to the A/D converters 18 and 19 is extremely low, Since the locked loop is in an equilibrium state, sin(θ-Φ) repeats positive and negative inversions around 0. As a result, the U/ signal of the comparator 23 repeats "1"/"0" inversion, and the output data Φ
repeats small increases and decreases, resulting in a state similar to chattering. In other words, in the conventional encoder displacement detection circuit described above, when the speed of the detection target is extremely slow, the output data Φ
The problem was that it caused minute vibrations.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a displacement detection circuit for an encoder that can always stabilize output data even when the speed of the detection target is extremely slow.

"Means for Solving the Problems" This invention was made in view of the above-mentioned circumstances, and it is possible to measure the displacement of a detection target recorded with a sine wave signal of a constant period and to be able to move freely relative to the detection target. ,
Displacement detection for an encoder that detects the displacement of the object to be detected from the output signal of an encoder that is detected by two detectors separated by a 1/4 wavelength interval and outputs an analog sine signal and an analog cosine signal corresponding to the displacement. The circuit includes first and second A/D converters that convert the sine signal and cosine signal into digital signals, and generates a cosine value and a sine value corresponding to the data value supplied to the input terminal. a function generation multiplication unit that outputs a multiplication value of the generated cosine value and the output signal of the first A/D converter, and a multiplication value of the generated sine value and the output signal of the second A/D converter, respectively; A counting means that counts a predetermined clock signal and supplies the count result to the function generation multiplication section and each output signal of the function generation multiplication section is detected, and if this difference exceeds 0, the count means subtraction comparison means for instructing up counting and instructing the counting means to count down if the difference does not exceed 0; It is equipped with a delay flip-flop that latches and outputs the count value of the counting means.

"Operation" Even if the count value of the counting means oscillates within one count, this oscillation is absorbed by the delay flip-flop, and the output data of the delay flip-flop does not oscillate.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, parts corresponding to those shown in FIG. 3 are designated by the same reference numerals and their explanations will be omitted.

The circuit of this embodiment differs from the circuit shown in FIG.
The circuit is configured similarly to the circuit shown in the figure. The delay flip-flop 40 has data Φ at its input terminal.
The U/ signal of the comparator 23 is supplied to each clock terminal CLK, and the data Φ at the input terminal immediately before the rise of the U/ signal is latched and output as data Φ _a . .

Next, the operation of this embodiment with the above configuration will be explained.

FIG. 2 is a waveform diagram showing an example of changing states of the U/signal. As shown in this figure, if the U/ signal is “1” from time t ₀ to time t ₁ , then
During this period, the counter 24 counts up, so the data Φ increases. Furthermore, the output data Φ _a of the delay flip-flop 40 is U/
Since the D signal does not rise, it is not updated and the previous value is maintained.

Then, when the speed of the detection target decreases significantly (or almost stops) during the period t ₁ to _{t 6} , for example, at time t ₁ , the phase-locked loop becomes balanced and θ=Φ, and as a result, the comparator 23's U/ The signal becomes "0". When this U/ signal becomes "0", the counter 24 outputs the clock signal CK.
is counted down by 1, and the value of data Φ is decreased by 1 (the value of Φ at this time is assumed to be k). Then, when the data Φ decreases by 1, if the detection target has hardly moved, the value of sin(θ-Φ) becomes positive again, and as a result, the U/signal becomes "1" at time _t2 . When the U/ signal becomes “1”, the counter 24
counts up the clock signal CK by 1, thereby increasing the value of data Φ by 1 to (k+1). When the value of data Φ becomes (k+1), time
At _t3 , the U/ signal becomes "0" and the counter 24 switches to down-counting. That is, from then on, the detection target starts moving at a relatively high speed at time t ₆
The above operation is repeated until the data φ
The value of oscillates in the range of k and (k+1).

Next, the value of data Φ _a during the above-mentioned period t ₁ to _{t 6} will be explained. First, at time _t2 when the U/ signal rises for the first time, the immediately preceding value of φ is latched, so the value of data Φ _a is updated to k. Then, at both times t ₄ and t ₆ when the U/signal rises next, the immediately preceding Φ
The value of is k, and as a result, the value of data Φ _a does not vary between times t ₁ and _{t 6} and maintains the value k stably. The value k does not change until the U/ signal rises again after time _t6 . Furthermore, the above-described operation is exactly the same when the detection target moves in the opposite direction.

Note that the above embodiment was an example in which a magnetic type was used as the displacement detection encoder.
As the encoder, an optical type or an electromagnetic type may be used.

"Effects of the Invention" As explained above, according to the present invention, the displacement of a detection target recorded with a sine wave signal of a constant period can be detected by
From the output signal of the encoder, which is movable relative to the detection target and is detected by two detectors spaced apart by a quarter wavelength, the encoder outputs an analog sine signal and an analog cosine signal corresponding to the displacement. A displacement detection circuit for an encoder that detects displacement of a detection target includes first and second A/D converters that convert the sine signal and cosine signal into digital signals, and a data value that corresponds to the input terminal. Generating a cosine value and a sine value, multiplying the generated cosine value by the output signal of the first A/D converter, and multiplying the generated sine value by the output signal of the second A/D converter. a function generating multiplier that outputs each value; a counting means that counts a predetermined clock signal and supplies the count result to the function generating multiplier; detecting a difference between each output signal of the function generating multiplier; If this difference exceeds 0, it instructs the counting means to count up, and if the difference exceeds 0, it instructs the counting means to count down, and the subtraction comparing means instructs the counting means to count up or down. Since it is equipped with a delay flip-flop that latches and outputs the count value of the counting means immediately before the timing of either one of the instructions, the output data is always stable even when the speed of the detection target is extremely slow. You can get the advantage that you can.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a waveform diagram showing an example of change in the U/signal in the same embodiment, and Fig. 3 shows the structure of a conventional change detection circuit for an encoder. It is a block diagram. 18, 19...A/D converter (first, second A/D converter
D converter), 20, 21...Function generation ROM (function generation multiplier), 22...Subtractor (subtraction comparison means), 23
... Comparator (subtraction comparison means), 24 ... Counter (counting means), 25 ... Function generation ROM (function generation multiplication section), 40 ... Delay flip-flop.

Claims (1)

[Claims] 1. The displacement of a detection target recorded with a sine wave signal of a constant period is movable relative to the detection target,
Displacement detection for an encoder that detects the displacement of the object to be detected from the output signal of an encoder that is detected by two detectors separated by a 1/4 wavelength interval and outputs an analog sine signal and an analog cosine signal corresponding to the displacement. The circuit includes: first and second A/D converters that convert the sine signal and the cosine signal into binary signals according to the values, and a cosine value and a sine value that correspond to the data values supplied to the input end. and output a multiplication value of the generated cosine value and the output signal of the first A/D converter, and a multiplication value of the generated sine value and the output signal of the second A/D converter, respectively. A function generating multiplier, a counting means for counting a predetermined clock signal and supplying the count result to the function generating multiplier, detecting a difference between each output signal of the function generating multiplier, and detecting a difference between the output signals of the function generating multiplier and determining whether the difference is zero. If the difference exceeds 0, the subtractive comparison means instructs the counting means to count up, and if the difference does not exceed 0, the counting means instructs the counting means to count down; 1. A displacement detection circuit for an encoder, comprising a delay flip-flop that latches and outputs the count value of the counting means immediately before the timing of .