JP3365913B2 - Position detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting a moving position of a moving body such as an arm in an NC control machine or a robot with high resolution.

[0002]

2. Description of the Related Art Conventionally, this type of position detector uses two-phase sine wave signals (hereinafter, Va and Vb) having a spatial phase difference of 90 degrees for position detection. This type of position detector is usually called an encoder.

In a conventional encoder, for example, light emitted from a light emitting diode is applied to a rotary code plate attached to a predetermined rotary shaft whose rotational position is to be detected, and the rotary code plate and a fixed member facing the rotary code plate are fixed. The light passing through the slit provided in the plate is received by a light receiving element such as a photodiode and converted into a voltage, whereby the slit spacing provided in the rotary code plate is set to 1 according to the rotation of the rotary code plate.
It is configured to obtain sine wave signals Va and Vb having a pitch of one cycle. In this case, two sine wave signals V
Two light receiving elements are provided at positions shifted by ¼ pitch in order to spatially have a 90 ° phase difference between a and Vb.

Next, each of these sine wave signals Va, Vb
Is input to the comparator, and rectangular wave signals AP and BP that have a high level (hereinafter, referred to as high) and a low level (hereinafter, referred to as low) according to the positive and negative values of the sine wave signal are generated on the output side, When the rectangular wave signal BP is low when the rectangular wave signal AP rises When the rectangular wave signal AP is low when the rectangular wave signal BP falls When the rectangular wave signal BP falls when the rectangular wave signal AP falls When it is high, when the rectangular wave signal AP is high at the time of rising of the rectangular wave signal BP, the up-down counter is sequentially incremented,
On the other hand, when the rectangular wave signal BP is high when the rectangular wave signal AP rises, when the rectangular wave signal AP is high when the rectangular wave signal BP falls, the rectangular wave signal BP when the rectangular wave signal AP falls When is low, when the rectangular wave signal AP is low at the time of rising of the rectangular wave signal BP, the up-down counter is sequentially counted down,
With this, the rotation angle of the rotary cord plate is detected.

In this position detecting method, as described above, the rectangular wave signal AP or B is generated according to the rotation of the rotary code plate.
The rotation angle is calculated in 4 cycles (1 pitch) of P.
It can only be performed once (called 4 times).

Therefore, by utilizing the fact that the output signals Va and Vb are sine wave signals, the rectangular wave signal BP is low at the time of rising of the rectangular wave signal AP, and the rectangular wave is at the time of falling of the rectangular wave signal AP. When the signal BP is high, the up / down counter is sequentially incremented,
On the other hand, when the rectangular wave signal BP is high when the rectangular wave signal AP rises, when the rectangular wave signal BP is low when the rectangular wave signal AP falls, the up / down counter is sequentially counted down,
By adding a correction amount of {tan ⁻¹ (Va / Vb)} / π to the count value, the rotation angle in one cycle is 4
A method of detecting with a resolution more than twice as high is known.

FIG. 10 shows the configuration of the position detector of the above method. Reference numerals 31 and 32 are sample hold circuits for sine wave signals Va and Vb, 33 and 34 are A / D converters for digital conversion, and 35 and 36 are comparators for obtaining rectangular wave signals AP and BP from the sine wave signals Va and Vb. Is the square wave signal A
A counter that counts up and down as described above according to P and BP, and 38 is {tan ⁻¹ (Va / Vb)} / π.
Is a computing unit for computing the correction amount of the above, 39 is an adder for adding the output values of the counter 37 and the computing unit 38, and 40 is a timing control circuit for operating the sample and hold circuits 31, 32 and the counter 37 in synchronization.

[0008]

By the way, in the position detector having the above construction, in order to accurately count even in an environment with noise in actual use, the sine wave signals Va and Vb are used by using a counter having a limited input frequency. A function called hysteresis is added to the comparators 35 and 36 that convert the sine wave signal into a rectangular wave at the same time as cutting off the high frequency.

Therefore, as shown in FIGS. 8 and 9, the two-phase sine wave signals are Va and Vb, and the rectangular wave signals output from the comparators 35 and 36 are AP, BP, and the comparator 3.
Assuming that the rectangular wave signals when using a comparator with hysteresis as 5 and 36 are APH and BPH, the output value of the counter 37 has timings for counting up and counting down as shown in (d) of FIGS. 8 and 9. A phenomenon occurs in which the timing does not match the original zero level of the sine wave signals Va and Vb. Therefore, the counter 37
If the count value of No. and the correction value of the arithmetic unit 38 are simply added, there is a problem that correct position detection cannot be performed in the range in which hysteresis is operating, as shown in (f) of FIGS. .

In view of the above problems of the prior art, the present invention provides a hysteresis function in a system for performing high-resolution position detection by adding a count value and a correction value, and performs accurate high-resolution position detection. It is an object of the present invention to provide a position detecting device that can obtain a result.

[0011]

The position detecting device of the present invention has respective voltage values Va and Vb of a two-phase sine wave signal having a phase difference of 90 degrees spatially generated according to the movement of a moving body.
Means for sampling and holding, and A / D for converting each sampled and held voltage value Va, Vb into a digital signal
A converter, a calculator for calculating the value of {tan ^-1 (Vb / Va)} / π from a two-phase sine wave digital signal from the A / D converter, and a two-phase sine wave with hysteresis. A comparator that converts into a two-phase rectangular wave by comparing with a zero level, a counter that counts the number of changes of a sine wave according to the movement of a moving body from a two-phase rectangular wave in synchronization with sample and hold timing, and a counter at the same time. It has a latch to detect the value of the two-phase rectangular wave input to the sample and hold, and the value of the two-phase rectangular wave sampled by the latch and 2
The comparison corrector that outputs the correction value by comparing the phase sine wave value, the adder that adds the outputs of the arithmetic unit, the counter, and the comparison corrector, the sample hold, the count reading, and the latch timing Timing control means for controlling so as to occur at the same time, the value at the sample hold timing of the two-phase rectangular wave input to the counter is detected by the latch, and the value is compared with the value of the two-phase sine wave. By obtaining the comparative correction value by performing the correction, the added value of the count value and the correction value is further corrected by ± 1 or 0.

The arithmetic unit, the comparison corrector, and the adder are composed of a microcomputer, ROM, RAM, and software,
It can be configured with digital hardware.

Further, the counter is composed of a synchronous counter, and the input first-stage latch output is used as the input of the latch of the comparator / compensator, and the sample hold and latch timings are synchronized with the readable timing of the synchronous counter. By delaying the delay, the sample hold counter and the latch can be configured so as not to be out of sync with each other.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the position detecting device of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numerals 1 and 2 are sample and hold circuits for sampling and holding two-phase analog input sine wave signals Va and Vb, and 3 and 4 are sample and hold circuits.
It is an A / D converter that digitally converts the phase analog sine wave signals Va and Vb. Reference numerals 5 and 6 are comparators with hysteresis for obtaining two-phase rectangular wave signals APH and BPH by comparing the two-phase analog sine wave signals Va and Vb with a zero level having hysteresis. It is a counter that counts the number of sine waves that change according to the movement of the moving body depending on the states of the signals APH and BPH.
The counter value is increased / decreased by 2 with the change of the cycle (360 degrees). 8 receives sine wave signals Va and Vb as input, and when Va is not 0 {tan ⁻¹ (Va / Vb)} /
π is calculated and output as a correction amount, and when Va is 0, it is 1
It is an arithmetic unit that outputs / 2. Reference numerals 11 and 12 are latches that detect and store the values (high or low) of the two-phase rectangular wave signals APH and BPH simultaneously input to the counter 7 during sample hold. Reference numeral 10 is a timing control circuit for controlling the sample and hold in the sample and hold circuits 1 and 2, the reading of the counter 7 and the timing of the latches 11 and 12. Reference numeral 13 indicates a correction value of ± 1 or 0 by comparing the values of the two-phase rectangular wave signals APH and BPH sampled by the latches 11 and 12 with the values of the two-phase sine wave digital signals Va and Vb (positive or negative). It is a comparison corrector that outputs. Reference numeral 9 is an adder for adding the outputs of the counter 7, the calculator 8 and the comparison corrector 13. Reference numeral 14 denotes an arithmetic unit including the arithmetic unit 8, the adder 9, and the comparison corrector 13.

FIG. 2 shows an example of a concrete configuration of the arithmetic unit 14, which is composed of a microcomputer 15, a ROM 16 and a RAM 17. FIG. 3 is a flowchart showing the operation of the microcomputer 15. In FIG. 3, C is a counter value, La and Lb are output values of the latches 11 and 12, Vad and Vbd are digital values of the sine wave signals Va and Vb, and L is a position measurement value. As shown in FIG. 2, the microcomputer 15 has La low, Lb high, Vad positive or 0, and V
Correction of -1 when bd is positive La is high, Lb is low, Vad is negative or 0, V
Correction of -1 when bd is negative La is high, correction of Lb is high, Vad is negative, correction of +1 when Vbd is positive La is low, correction of Lb is low, Vad is positive, correction of +1 when Vbd is negative I try to do it with software.

FIG. 4 shows another specific example of the configuration of the arithmetic unit 14, which comprises a ROM 18, a shift register 19, a ROM 20 and an adder 21. ROM18 is Vad,
By inputting Vbd to the address line, Vad
Is set so that {tan ⁻¹ (Vb / Va)} / π is digitized when is not 0, and 1/2 is digitized when Va is 0. ing. The shift register 19 includes the counter 7
The output of is used as an input and acts as a multiplier
It is set to align the digits with the output of. ROM2
0 is the output La of the latches 11 and 12 on the address line,
By inputting Lb, Vad, and Vbd, the correction values shown in the logic table of FIG. 5 are set to be output to the data line as data matched with the digit of the output of the ROM 18. The adder 21 is configured to add the outputs of the ROM 18, the shift register 19 and the ROM 20 described above.

FIG. 6 shows a configuration example using a general synchronous counter as a concrete configuration example of the counter 7 and the latches 11 and 12. 22 to 25 are called D flip-flops, which convert the digital signal input to D to C.I. A function that holds and outputs at the timing of the synchronization signal indicated by CLK,
Reference numeral 26 is called an up / down counter, which counts up pulses input to UP and counts down pulses input to DOWN. Reference numeral 27 is a D flip-flop that constitutes the latch 11, 28 is a D flip-flop that constitutes the latch 12, and R. CLK is a sample hold, latch, and counter read timing signal output from the timing control circuit 10. As shown in FIG. 7, the synchronization signal C.C. It is generated later than CLK. According to this structure, the actual read timing is slightly delayed from the desired read timing, but the maximum C.I. Since it is less than one cycle of CLK, C.I. It can be ignored by making CLK fast enough.

FIGS. 8 and 9 show timing charts in the case of counting up and in the case of counting down.
(A) is a sine wave signal Va, Vb, (b) is a rectangular wave signal AP, BP generated by a zero level comparator, (c)
Are rectangular wave signals APH and BPH generated by a zero level comparator with hysteresis, (d) is a count value,
(E) is the output value of the calculator 8, (f) is the added value of the count value and the calculated value, and (g) is the added value of the count value, the calculated value, and the comparison correction value that are the position detection values of this embodiment. Is shown.

In the above description, the comparator / compensator has been described with the counter unit configured to have a multiplication factor of two.
In the case of quadruple multiplication as well, it can be implemented by using the respective comparison correctors.

[0021]

According to the position detecting apparatus of the present invention, as is apparent from the above description, a comparator with hysteresis for generating a two-phase rectangular wave signal from a two-phase sine wave signal and two
A counter that counts the position based on the phase rectangular wave signal, and 2
In a position detection device that includes a calculator that calculates a correction amount from a phase sine wave signal, an adder, and timing control means, and that adds a count value and a correction amount to perform high-resolution position detection, input to a counter at the same time. Compensation for outputting a correction value by comparing the value of the two-phase rectangular wave sampled by the latch with the value of the two-phase sinusoidal signal Since the adder adds the outputs of the arithmetic unit, the counter, and the compensator, the timing of counting up and down due to hysteresis does not exactly match when the sine wave signal is at zero level. However, it is possible to obtain a correct measurement value, and therefore, a hysteresis function is provided for accurate counting and, therefore, the counting timing and correction amount output. Exerts effect that it is the timing to obtain a detection result of the correct resolution higher offset.

If the arithmetic unit, the comparison corrector, and the adder are composed of a microcomputer, ROM, RAM, and software, correct measured values can be obtained at low cost.

Further, when the computing unit, the comparison corrector and the adder are composed of digital hardware, a correct measured value can be obtained in a short time of 1 microsecond or less, and the position can be detected at high speed.

If a synchronous counter is used as the counter and the input first stage latch is used as a latch input so that the counter and the latch do not deviate from each other in synchronization, the desired reading timing may be slightly delayed and the wiring can be reduced. It is possible to completely synchronize the latch and the state of the counter, regardless of the delay caused by, and obtain a correct measured value.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a position detection device of the present invention.

FIG. 2 is a configuration diagram of a calculation unit using a microcomputer according to the same embodiment.

FIG. 3 is an operation flowchart of a microcomputer.

FIG. 4 is a configuration diagram of a calculation unit using a ROM in the same embodiment.

FIG. 5 is a logic diagram of a ROM that functions as a comparison calculator.

FIG. 6 is a configuration diagram of a latch using the synchronous counter in the same embodiment.

FIG. 7 is a timing diagram of a synchronization signal when a synchronous counter is used.

FIG. 8 is a timing chart at the time of counting up in the same embodiment.

FIG. 9 is a timing chart at the time of countdown in the same embodiment.

FIG. 10 is a configuration diagram of a conventional position detection device.

[Explanation of symbols]

1, 2 sason pull-hold circuit 3, 4 A / D converter 5, 6 comparator with hysteresis 7 counter 8 calculator 9 adder 10 timing control circuit 11, 12 latch 13 comparison corrector 15 microcomputer 16 ROM 17 RAM 18 calculator ROM 19 as a shift register 20 ROM as a compensator 21 Adder 22, 24 D flip-flop 26, 27 for latching first stage of synchronous counter D flip-flop for latch

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Claims (4)

(57) [Claims] 1. A voltage value Va of a sine wave signal having a phase difference of 90 degrees spatially generated according to the movement of a moving body,
A means for sampling and holding Vb, an A / D converter for converting each of the sampled and held voltage values Va, Vb into a digital signal, and a two-phase sine wave digital signal from the A / D converter from {t
An ⁻¹ (Vb / Va)} / π value calculator, a comparator that converts a two-phase sine wave to a zero level with hysteresis, and a two-phase rectangular wave, and a sample hold A counter that counts the number of changes in a sine wave according to the movement of a moving body from a two-phase rectangular wave in synchronism with the timing, and a latch that detects the value of the two-phase rectangular wave input to the counter at the time of sample hold And a comparator / compensator that outputs a compensation value by comparing the two-phase rectangular wave value sampled by the latch with the two-phase sine wave value, and adds the outputs of the calculator, counter, and comparator / compensator. And a timing control means for controlling so that the timings of sample hold, count reading, and latch occur at the same time. 2. The position detecting device according to claim 1, wherein the arithmetic unit, the comparison corrector and the adder are constituted by a microcomputer, a ROM, a RAM and software. 3. The arithmetic unit, the comparison corrector, and the adder are configured by digital hardware.
The position detection device described. 4. The counter is constituted by a synchronous counter, and the input first-stage latch output is used as the input of the latch of the comparator / compensator, and the sample hold and latch timing are synchronized with the readable timing of the synchronous counter. The position detecting device according to claim 1, wherein the delay is configured so that the synchronization of the counter and the latch does not shift.