JPH0449891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a displacement detection device for an encoder suitable for use in detecting displacement such as angle or position.

"Prior Art" A circuit shown in FIG. 3 is generally known as a circuit for converting an analog angle signal into a digital signal. The circuit shown in this figure is a circuit that converts a resolver signal into a digital angle signal. In the figure, reference numeral 1 denotes an angle detection section that outputs a resolver signal, and is composed of a synchronizer, which is a type of rotary transformer, and a Scott transformer, etc., that converts the output signal of the synchro into a resolver signal. In this case, if a carrier wave signal sinω ₀ t is supplied to the synchro rotor,
A synchronized signal corresponding to the rotation angle θ of the rotor is obtained from the stator, and when this synchronized signal is supplied to the primary side of the Scott transformer, sin θ・sinω ₀ t and cos θ・
A resolver signal of sinω ₀ t can be obtained.

Next, 2 and 3 are demodulators, which remove the carrier signal from the resolver signal and extract each angle signal of sin θ and cos θ by performing synchronous detection or the like. The output signals of the demodulators 2 and 3 are each supplied to one input terminal of analog multipliers 4 and 5, and the output signals of the analog multipliers 4 and 5 are supplied to a subtracter 6 to detect the difference. . The output signal of subtractor 6 is
Supplied to VCO (voltage controlled oscillator) 7, VCO7
The output signal of is supplied to an up-down count 8.

In this case, when the output signal of the subtractor 6 is positive,
The output signal of the VCO 7 is supplied to the up-count terminal of the up-down counter 8, and when the output signal of the subtracter 6 is negative, the output signal of the VCO 7 is supplied to the down-count terminal. The output signal Φ of this up-down counter 8 is generated by an analog function generator 9.
As a result, the analog function generator 9 outputs sine and cosine signals (sinΦ and cosΦ) corresponding to the count output Φ. Then, the signal sinΦ is supplied to the other input terminal of the analog multiplier 5, and the signal cosΦ is supplied to the other input terminal of the analog multiplier 4.

According to the circuit described above, the analog multipliers 4, 5
The output signals of are sinθ・cosΦ and cosθ・
becomes sinΦ. Therefore, the output signal of the subtracter 6 is sinθ・cosΦ−cosθ・sinΦ = sin(θ−Φ) (1), and the output signal of the VCO 7 is the value corresponding to the value of sin(θ−Φ). becomes the frequency. Since the output signal Φ of the up-down counter 8 goes up and down according to the value of sin(θ-Φ), the above-mentioned circuit will eventually set the value of sin(θ-Φ) to 0, that is, This results in a phase-locked loop where θ=Φ. In this case, if Φ is set to about 10 bits, it is possible to obtain a resolution that divides the rotation angle range from 0 to 2π into 1024.

"Problems to be solved by the invention" By the way, in the conversion circuit shown in Fig. 3,
Since it is a circuit that mainly handles analog signals, there is a limit to the degree of integration, and currently the size of a hybrid IC type is approximately 50 x 50 mm. In addition, drift is likely to occur due to fluctuations in the temperature characteristics of the VCO 7 or the power supply voltage, which poses problems in terms of reliability and accuracy.

Furthermore, although the above conventional example was an example of displacement detection for an encoder that detects angles, the resolution and accuracy of conventional displacement detection for encoders that detect linear displacement are still not sufficient. Ta.

Further, it is desirable that the displacement detection for the encoder detects the current displacement immediately when the power is turned on, and it is necessary to take this point into consideration when creating the displacement detection for the encoder.

This invention was made in view of the above-mentioned circumstances.Most of the processing is done using digital signals, and as a result, it is possible to eliminate analog circuit elements, which allows for a high degree of integration on a single monolithic semiconductor substrate. The purpose of the present invention is to provide a displacement detection device for an encoder that can be configured, eliminate drift, improve accuracy, and increase resolution, and can output current displacement data immediately when power is turned on. It is said that

"Means for Solving the Problems" In order to solve the above problems, the present invention provides a scale in which a signal generation source is provided so that only a direct sine wave can be obtained from a predetermined orbit in each fixed section. , each of which is movable relative to the orbit, outputs a level signal corresponding to the signal strength of the signal generation source of the orbit, and has a phase of 90 degrees with respect to the wavelength of the sine wave. A first and a second sensor provided so as to be offset from each other, a first and a second A/D converter that converts the output signals of the first and second sensors into digital signals, and a predetermined data. a function that outputs a multiplication result of a corresponding cosine value and an output signal of the first A/D converter and a multiplication result of a sine value corresponding to the predetermined data and an output signal of the second A/D converter; A generation multiplication section, a subtraction means for detecting the difference between the multiplication results of the function generation multiplication section, and a count corresponding to the difference detected in the subtraction means, and up/down of the count depending on the sign of the difference. a counting means having a preset data input terminal for switching and supplying the count result to the interval number generation multiplier as the predetermined data and for taking in the supplied data; and the first and second magnetic sensors. The output signal of is waveform-shaped to create a two-phase rectangular wave with a phase difference of 90°, and from this rectangular wave, it is detected how many detection sections on the orbit the first or second magnetic sensor has passed. In addition, a passing section number detecting section having a preset data input terminal for taking in the supplied data, and storing the output data of the counting means and the passing section number detecting section when the power is turned off, and storing each of the stored data. and non-volatile storage means for supplying the data to each preset data input terminal of the counting means and the number of passing sections detecting section when the power is turned on, and the function generating multiplier, the subtracting means and the counting means are An aids locked loop is established, and the output signals of the counting means and the passage section number detecting section are output as absolute displacement data.

"Operation" Sin and cos signals that do not include carrier waves are output from each magnetic sensor, and after the signals of the magnetic sensors are converted into digital signals, they are supplied to a phased drop loop that performs digital processing. Displacement data within the magnetization section of the magnetic sensor is output from the output signal of the droplet loop.
Further, the non-volatile storage means supplies the previous output values from the counting means and the passing section number detection section respectively when the power is turned on.

"Embodiments" Hereinafter, embodiments of the present invention using a magnetic scale 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 this figure, 15 is a scale, which is constructed by magnetizing a predetermined orbit with a sine wave of a constant period. The scale 15 of this embodiment is constructed by setting a circular orbit on the surface of a disc-shaped magnetic material and magnetizing this circular orbit. Also, the wavelength λ of the sine wave used for magnetization
is set to about several tens to several hundred μm. 1
6 and 17 are magnetic sensors, and scale 15
Outputs a level signal corresponding to the strength of magnetization above. That is, as the magnetic sensors 16 and 17,
An output signal that does not include a carrier wave is used, and for example, a sensor using a semiconductor element is used. Further, the magnetic sensor 17 is the magnetic sensor 1
It is set to be shifted by 1/4λ (90°) from 6. Therefore, the interval between the magnetic sensors 16 and 17 is set to be (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. Therefore, if the interval of one cycle of the magnetization sine wave (from pole to pole of the scale 15) is θ=0 to 2π, the magnetic sensor 16,
Each of the 17 output signals becomes each sin θ and cos θ.

Next, 18 and 19 shown in FIG. 1 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. If the subtraction result of the subtracter 22 is positive, this digital comparator 23
An up pulse is supplied to the counter 24 (8 to 1 bit counter), and if the subtraction result is negative, a down pulse is supplied to the counter 24. in this case,
The counter 24 has a preset data input terminal 24a.
, and when data is supplied to this terminal, it is imported internally. Next, 25 is a function generation ROM, which outputs sine and cosine data corresponding to the count value Φ of the counter 24. That is, data of sin Φ and cos Φ is stored in advance in the function generation ROM 25, and the stored data is read out sequentially according to the count value Φ. and,
Data cosΦ is supplied to the other input of digital multiplier 20, and digital sinΦ is supplied to the other input of digital multiplier 21. According to the above configuration, the output of the subtracter 22 becomes sin(θ-Φ) as in the case of the circuit shown in FIG. 3 described above. Therefore, the comparator 23 outputs an up pulse when the value of sin (θ - Φ) is positive, and outputs a down pulse when it is negative, and as a result, the count value of the counter 24 Φ
increases or decreases depending on the value of sin(θ−Φ). In addition,
Multipliers 20, 21 and function generation in the above configuration
The ROM 25 constitutes a function generation multiplication section 28. Counting means 29 with comparator 23 and counter 24
is configured.

Next, 26 shown in FIG. 1 is a speed detection section that differentiates the output signal Φ of the counter 24 with respect to time t and outputs the result. The speed detection principle of this speed detection section 26 will be described later.

On the other hand, waveforms 30 and 31 shown in FIG. 1 are converted into binary signals of "H" level and "L" level by determining the output signals of the magnetic sensors 16 and 17, respectively, using a predetermined threshold value. It is a 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, as shown in Figure 2 A and B, respectively.
Further, when the magnetic sensors 16 and 17 move in the positive direction, the pulse P1 advances, and when the movement moves in the negative direction, the pulse _P1 advances.
Pulse P ₂ is set to advance. 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 pulse P ₂ at the rising edge of pulse P ₁ is "H" or "L". I have to. The output signal Sw of this direction discrimination circuit 33 is outputted to the counter 34.
is supplied to the up/down switching terminal of
It is designed to be output externally. counter 3
4 counts the pulse _P1 while switching up or down according to the signal Sw. In this embodiment, the magnetic sensor 16,1
An up count is performed when the number 7 is moving in the positive direction, and a down count is performed when the number 7 is moving in the negative direction. In addition, the magnetic sensors 16 and 17 are activated every time the scale 15 rotates once.
The zero point signal Sz output at that reference position is
After passing through the waveform shaping circuit 32, it becomes a 0-point pulse Pz, and this 0-point pulse Pz is supplied to the reset terminal R of the counter 34. As a result, the counter 34 uses the magnetic sensors 16 and 17 as a reference. It is reset each time the position is reached. Therefore, the count value of the counter 34 is the same as that of the magnetic sensor 1.
Between the current position and the reference position of 6 and 17,
This value corresponds to the number of magnetic sections (number of magnetic poles) on the scale 15 that the magnetic sensors 16 and 17 have passed through. Further, the counter 34 is provided with a preset data input terminal 34a, and when data is supplied to this terminal, it is taken into the counter. The output signal of the counter 34 and the output signal of the counter 24 are outputted to the outside as absolute position data Dout. In this case, the output signal N of the counter 34 constitutes the upper bit data of the data Dout, and the count value Φ of the counter 24 constitutes the data
Configures the data of the lower bits of Dout.

Next, 40 shown in FIG. 1 is a static RAM backed up by battery B and made non-volatile.
(For example, CMOS type). 41 is a power supply monitor circuit that detects the moment when the power is turned on and off, and at the moment when the power is turned off, a read signal R is sent to the static RAM 40.
It also supplies a write signal W to the static RAM 40 at the moment the power is turned off. In this case, the static RAM 40 receives the write signal W.
When the read signal R is supplied, the count value Φ of the counter 24 and the count value N of the counter 34 are stored, and when the read signal R is supplied, the stored count values Φ and N are stored in the counter 24 and the counter 34, respectively. Supplied to each preset data input terminal.

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

First, when the magnetic sensors 16 and 17 start moving in the positive direction, the counter 34
6 and 17 pass through a magnetic section (magnetization pitch), an up-count is performed, 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,
How many magnetized sections have the magnetic sensors 16 and 17 passed, that is, the current magnetic sensors 16 and 17
It is possible to know how many pitches is located from the reference position.

On the other hand, the signals sin θ and cos θ output from the magnetic sensors 16 and 17 are converted into digital signals by A/D converters 18 and 19, respectively, and then the signals are generated by a function.
It is multiplied by the signals cosΦ and sinΦ output from the ROM 25. Then, it is supplied to the subtracter 22 and sin(θ−
Φ) is detected, and when the value of sin(θ−Φ) is positive, the count value Φ of the counter 24 increases, and
When sin(θ−Φ) is negative, the count value Φ decreases. Then, the output sinΦ, cosΦ of the function generation ROM
increase or decrease according to the count value Φ, so in the end, the circuit shown in FIG. It becomes a phase-locked loop like Φ. Therefore, the count value Φ of the counter 24 is data indicating where the magnetic sensor 16 is located in the magnetization section, or in other words, where the magnetic sensor 16 is located between the magnetic poles.
Therefore, the lower bit of the data Dout becomes data indicating a minute position within the magnetization section of the magnetic sensor 16. In this case, since the counter 24 is composed of 8 to 10 bits as described above,
The resolution of the minute position mentioned above is 1/256 to 1/2 of the magnetization section.
The accuracy is about 0.048.

Here, the detection principle of the speed detection circuit 26 will be explained. As described above, since the count value Φ is controlled to be equal to θ, the count value Φ changes depending on the relative speed of the magnetic sensors 16 and 17. Therefore, the rate of change of count value Φ (dΦ/
dt) is a value corresponding to the relative speed of the magnetic sensors 16 and 17, and a speed signal is output from the speed detection circuit 26.

Then, the scale 15 or the magnetic sensor 1
Suppose that the operation of the devices (not shown) interlocked with 6 and 17 is completed and the power of the circuit shown in FIG. It is supplied to the static RAM 40. As a result, count values Φ and N corresponding to the displacements of the magnetic sensors 16 and 17 at this point in time are stored in the static RAM 40. Then, when the device (not shown) is driven again and the power is turned on to the circuit shown in FIG. 1, the power supply monitor circuit 41 detects this and starts reading signal R.
Supply to RAM40. As a result, static
RAM40 is the count value Φ that was stored until then.
and N to counter 24 and counter 34, respectively.
The data is supplied to preset data input terminals 24a and 34a, respectively. As a result, the initial values of the counter 24 and the counter 34 each become the previous value, and as a result, the absolute displacement data Dout becomes data corresponding to the displacement of the magnetic sensors 16 and 17 at the time of starting the re-driving. That is, even immediately after the power is turned on, the magnetic sensor 16 at that time,
17 accurate displacement data are output.

In this embodiment, since most of the circuits process digital signals, analog circuit elements can be eliminated and a high degree of integration can be achieved on a single monolithic semiconductor substrate. As a result of actually manufacturing the IC, we were able to store it in a flat package with length, width, and height of approximately 5 x 7 x 1 (mm). This is a dramatic reduction in size compared to conventional conversion circuits of this type that process analog signals, so only hybrid ICs were used, and their size was approximately 50 x 50 x 10 (mm). I can say that. Also, temperature changes (-20 to +80°C) and power supply voltage changes (±20
%) with the circuit shown in Figure 3. In the circuit shown in Figure 3, there was a drift of ±2 bits for both temperature and voltage changes, but in this application, under the same conditions The drift was as low as ±1 bit. in this case,
Since the least significant bit of the data Dout in the present application is the least significant bit of the data indicating a minute position within the magnetization section, it has the advantage that the influence of its drift is extremely small.

Note that the above-mentioned embodiment is an example in which the magnetization trajectory is circular, and is an embodiment in which the present invention is applied to a rotary encoder. Of course, the present invention can also be applied to an encoder.

"Effects of the Invention" As explained above, according to the present invention, a scale is provided with a signal generation source so that only a direct sine wave can be obtained from a predetermined trajectory in each fixed section, and is movable relative to the orbit, outputs a level signal corresponding to the signal strength of the signal generation source in the orbit, and has a phase shifted by 90° with respect to the wavelength of the sine wave. first and second sensors provided, first and second A/D converters that convert the output signals of the first and second sensors into digital signals, respectively, and a cosine value corresponding to predetermined data. a function generation multiplication unit that outputs a multiplication result of the output signal of the first A/D converter and a sine value corresponding to the predetermined data and the output signal of the second A/D converter; A subtraction means for detecting the difference between the multiplication results of the function generation multiplication section, and a count corresponding to the difference detected in this subtraction means, and switching up/down of the count depending on the sign of the difference, and this count result a counting means having a preset data input terminal for supplying the predetermined data to the function generation multiplication section and taking in the supplied data; and waveform shaping of the output signals of the first and second magnetic sensors. to create a two-phase rectangular wave with a phase difference of 90°, and from this rectangular wave, detect how many detection sections on the orbit the first or second magnetic sensor has passed, and also detect the supplied data. a passing section number detecting section having a preset data input terminal for taking in the number of passing sections, and storing the output data of the counting means and the passing section number detecting section when the power is turned off, and transmitting each of the stored data to the counting means when the power is turned on. and non-volatile storage means for supplying each preset data input terminal of the passage section number detection section, and the function generation multiplication section, the subtraction means and the counting means form a phase-locked loop. Since the output signals of the counting means and the passing section number detection section are outputted as absolute displacement data, even immediately after the power is turned on,
An advantage is obtained that the displacement can be instantaneously output at that point. In addition, since most of the processing is done using digital signals, analog elements can be eliminated, allowing for higher integration on a single monolithic semiconductor substrate, eliminating drift and improving accuracy. In addition, it is possible to obtain the advantage that the resolution is improved. Further, in this invention, the displacement within the magnetized section and the number of passages through the magnetized section are detected based on the same sensor, so the configuration can be simplified. Furthermore, in order to retain the data immediately before the power is turned off, instead of backing up the counting means and passage section number detection section, the measured data when the power is turned off is stored in a non-volatile storage means. It is not affected by external disturbances during operation, and accurate absolute data can be output when the power is turned on again.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of this invention, FIG. 2 is a waveform diagram showing output signal waveforms of waveform shaping circuits 30 and 31 in the same embodiment, and FIG. 3 is a waveform diagram of a conventional displacement detection device. FIG. 2 is a circuit diagram showing the configuration. 15... Scale, 16, 17... Magnetic sensor (first, second magnetic sensor), 18, 19... A/
D converters (first and second A/D converters), 22...
...Subtractor, 24a, 34a...Preset data input terminal, 28...Function generation multiplier, 29...Counting means, 40...Static RAM, 41...
…Power supply monitor circuit, B…Battery (more than 40,4
1, B is storage means).

Claims (1)

[Scope of Claims] 1. A scale provided with a signal generation source so that only a direct sine wave can be obtained in each fixed section from a predetermined orbit, each of which is movable relative to the orbit. and first and second sensors outputting a level signal corresponding to the signal strength of the signal generation source in the orbit, and provided so as to be out of phase by 90° with respect to the wavelength of the sine wave. , first and second A/D converters that convert the output signals of the first and second sensors into digital signals, respectively, and a cosine value corresponding to the predetermined data and the first A/D converter.
a function generation multiplication section that outputs a multiplication result of the output signal of the D converter and a sine value corresponding to the predetermined data and the output signal of the second A/D converter; a subtracting means for detecting the difference between the results of each multiplication, and counting corresponding to the difference detected by the subtracting means, switching up/down the count depending on the sign of the difference, and transmitting this count result to the function generation multiplication section. counter means having a preset data input terminal for supplying the predetermined data to the magnetic sensor and taking in the supplied data; and waveform shaping of the output signals of the first and second magnetic sensors so that the phase thereof is 90°. Create a square wave with two different phases,
A passing section number detection section that detects how many detection sections on the orbit the first or second magnetic sensor has passed through from this rectangular wave, and has a preset data input terminal for taking in the supplied data. and storing the output data of the counting means and the passing section number detecting section when the power is turned off, and transmitting each of the stored data to each preset data input terminal of the counting means and the passing section number detecting section when the power is turned on. and a non-volatile storage means for supplying the function, the function generating multiplier, the subtracting means and the counting means form a phase-locked loop, and the output signals of the counting means and the passing section number detecting section are A displacement detection device for an encoder characterized by outputting absolute displacement data. 2. The first and second A/D converters, the function generation multiplication section, the subtraction means, the counting means, the passing section number generation section, and the storage means are each incorporated on a single monolithic semiconductor substrate. A displacement detection device for an encoder according to claim 1, characterized in that: