JP2938472B2 - Rotation angle detector - Google Patents

Description

The present invention relates to a rotation angle detecting device used for detecting a rotation angle of an AC servomotor or the like.

[Prior Art] FIG. 2 is a block diagram showing a configuration example of a conventional rotation angle detecting device. In this figure, reference numeral 1 denotes an AC servomotor (not shown) which is attached to an AC servomotor according to the rotation angle of the AC servomotor. This is a one-phase input two-phase output resolver that outputs a sine wave detection voltage and a cosine wave detection voltage, and the input coil 1a
And the output coil electrically in phase with the input coil 1a
1b and an output coil 1c having a phase difference of 90 degrees electrically with respect to the input coil 1a.

Reference numeral 2 denotes a sine wave generator which constantly generates a sine wave signal voltage of a predetermined frequency, and is applied to both ends of the input coil 1a of the resolver 1. It is.

Further, 4 is a cosine converter that outputs a cosine wave signal voltage according to an input value, 5 is a sine converter that outputs a sine wave signal voltage according to an input value, and 6 is an output voltage and a cosine converter 4 that are supplied to an amplifier 3b. A multiplier that multiplies the output voltage of the
7 is a multiplier for multiplying the output voltage of the amplifier 3c by the output voltage of the sine converter 5, 8 is a differential amplifier which receives the output voltage of each of the multipliers 6 and 7 and amplifies the difference, and 9 is the difference amplifier. This is a divider for dividing the output voltage of the dynamic amplifier 8 by the output voltage of the amplifier 3a.

In addition, reference numeral 10 denotes a pulse oscillator which outputs an "H" level voltage from the output terminal 10a if the output voltage of the divider 9 is positive, and outputs a "H" level voltage from the output terminal 10b in accordance with the absolute value of the output voltage of the divider 9 If the output voltage of the divider 9 is negative, an "L" level voltage is output from the output terminal 10a and the output terminal 10b responds to the absolute value of the output voltage of the divider 9 if the output voltage is negative. Outputs frequency pulses. Reference numeral 11 denotes an up / down counter. If the voltage applied to the input terminal 11a is at "H" level, the pulse input from the input terminal 11b is counted up, the count value is output, and the count value is applied to the input terminal 11a. Input terminal 1 if voltage is “L” level
Count down the pulse input from 1b and output the count value.

In such a configuration, when the output voltage of the sine oscillator 2 is sinωt, when the AC servomotor rotates and the resolver 1 rotates, the phase difference between the voltage of the coil 1a and the output voltage of the coil 1c is θ, that is, When the rotation angle of the resolver, that is, the rotation angle of the AC servomotor is θ, voltages V _1b and V _1c represented by the following equations are induced in the coils 1b and 1c, respectively.

V _1b = k ₀ · sin ωt · sin θ V _1c = k ₀ · sin ωt · cos θ Here, k ₀ is a constant.

This allows the amplifiers 3b and 3c to output a voltage
V _3b and V _3c are output, respectively.

V _3b = k ₀ · sin ωt · sin θ V _3b = k ₀ · sin ωt · cos θ Here, k is a constant.

On the other hand, assuming that the output value of the up / down count 11 is ψ, the cosine converter 4 and the sine converter 5 output voltages V ₄ and V ₅ represented by the following equations, respectively.

V ₄ = cosψ... V ₅ = sinψ... Accordingly, the multipliers 6 and 7 output voltages V ₆ and V ₇ represented by the following equations, respectively.

V ₆ = k · sin ωt · sin θ · cosψ... V ₇ = k · sin ωt · cos θ · sinψ... As a result, the voltage V ₈ represented by the following equation is output from the differential amplifier 8.

V ₈ = k · sin ωt · (sin θ · cosψ−cos θ · sinψ) = k · sin ωt · sin (θ−ψ) On the other hand, since the voltage V _1a across the coil _1a is sin ωt, this voltage V _1a Is multiplied by k in the amplifier 3a to become a voltage _V3a represented by the following equation.

V _3a = k · sin ωt... Therefore, the divider ₉ outputs a voltage V ₉ represented by the following equation.

V ₉ = sin (θ−ψ) Then, the voltage V ₉ is input to the pulse oscillator 10 and the voltage V ₉
Is positive, that is, θ> ψ, the output terminal 10 of the pulse oscillator 10 is
“H” level voltage is output from a and output terminal 1
The frequency of the pulses corresponding to the absolute value of the voltage V ₉ is output from 0b.

Therefore, the up / down counter 11 counts up the pulse input from the input terminal 11b at a speed corresponding to (θ−ψ), and when the value becomes θ = ψ, the pulse oscillator 10 stops the pulse oscillation.

On the other hand, if the voltage V ₉ is negative, that is, θ <ψ, the pulse oscillator
10 output with terminal "L" level voltage from 10a is output, the output terminal 10b is a pulse having a frequency corresponding to the absolute value of the voltage V ₉ is output.

Therefore, the up / down counter 11 counts down the pulse input from the input terminal 11b at a speed corresponding to (θ−ψ), and when the value becomes θ = ψ, the pulse oscillator 10 stops the pulse oscillation.

As described above, the voltage V ₉ is always zero, i.e., theta =
It is controlled so as to become ψ. Therefore, the rotation angle θ of the resolver 1, that is, the rotation angle θ of the AC servomotor can be detected from the output value の of the up / down count 11.

[Problem to be Solved by the Invention] By the way, the resolver used in the above-described conventional rotation angle detecting device has advantages that it is more environmentally resistant than an encoder, and that high resolution can be easily obtained. ing.

However, when this resolver is used for a rotation angle detection device,
The peripheral circuit becomes complicated and the number of components of the circuit increases, so that there are the following drawbacks.

Expensive.

The equipment is large.

Low reliability.

Low detection accuracy.

Practical application is difficult.

The present invention has been made in view of the above circumstances, and has as its object to provide a rotation angle detection device that is inexpensive, small, lightweight, highly reliable, and has high detection accuracy.

Means for Solving the Problems A rotation angle detection circuit according to the present invention includes an input coil to which an oscillation signal of a predetermined frequency is applied, a first output coil electrically in phase with the input coil. A resolver including a second output coil having a phase difference of 90 degrees with respect to the input coil, a peak detector that detects a peak value of the oscillation signal and outputs a sample signal, A first sample-and-hold circuit for receiving a sample signal and holding a first output voltage induced in the first output coil; and A second sump-hold circuit for holding a second output voltage induced in the second output coil, and a first sum-hold circuit for holding the first and second output voltages.
An analog-to-digital converter for converting the first and second digital data into a first digital signal and a second digital data; A rotation angle of the resolver = tan ^-1 ((first digital data) / (second digital data)). Features.

According to the present invention, if the phase difference between the voltage of the oscillation signal and the second voltage when the resolver rotates, that is, the rotation angle of the resolver is θ, first, the peak detector And outputs a sample signal.

Next, the first sample and hold circuit holds the first output voltage induced in the first output coil. At the same time, the second sample and hold circuit holds the second output voltage induced on the first output coil. That is,
The first output voltage and the second output voltage are held at the same time.

Then, the held first and second output voltages are converted into first and second digital data by an analog / digital converter, respectively.

Accordingly, the control circuit inputs the first and second digital data according to the timing of the sample signal, and converts the first and second digital data into the rotation angle of the resolver = tan ⁻¹ (( (1 digital data) / (second digital data)) to calculate the rotation angle of the resolver.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a rotation angle detecting device according to an embodiment of the present invention.
Parts corresponding to the respective parts in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

In the rotation angle detecting device shown in FIG.
Instead of to 11, the peak detector 12 samples the signal, and outputs the detected peak value V _p of the output voltage V _3a of the amplifier 3a, the output voltage V _3b and V _3c amplifiers 3b and 3c to input sample signal And A / D converters 15 and 1 for converting the output voltages of sample-hold circuits 13 and 14 to digital data, respectively.
6, while inputting the sample signal, A / D converter 15 and
A CPU (Central Processing Unit) 17 for inputting the output data of each of the 16 and calculating the rotation angle of the resolver 1 is newly provided.

In such a configuration, the output voltage of the sine oscillator 2 is set to sinωt, and the AC servomotor rotates to rotate the resolver 1.
Assuming that the phase difference between the voltage of the coil 1a and the output voltage of the coil 1c at the time of rotation, that is, the rotation angle of the resolver is θ, the amplifiers 3b and 3c output the voltages V _3b and V
_3c is output respectively.

V _3b = k · sin ωt · sin θ V _3b = k · sin ωt · cos θ Here, k is a constant.

On the other hand, amplifier 3a outputs voltage _V3a represented by the following equation.

V _3a = k · sin ωt Therefore, the peak detector 12 detects the peak value V _p of the voltage V _3a , that is, ± k, and outputs a sample signal. And
Sample hold circuit 13 and 14, the output voltage V _3b and V _3c amplifiers 3b and 3c when the peak value V _p to input sample signal is outputted, i.e., the voltage V _hb and V expressed by the following formula
_hc is held respectively.

_{V hb = ± k · sinθ ···} V hc = ± k · cosθ ··· Next, A / D converters 15 and 16, the digital sample-hold circuit 13 and 14 of the output voltage V _hb and V _hc, respectively Convert to data and output.

After inputting the output data of each of the A / D converters 15 and 16 in accordance with the timing of the sample signal, the CPU 17 performs the following calculation to perform the rotation angle θ of the resolver 1, that is, the AC servo motor. Is detected.

Incidentally, in one embodiment described above, was used peak detector 12 is to rise detection accuracy greater the absolute value of the output voltage V _3a of the amplifier 3a (when sin .omega.t = 0 is undetectable) .

The sample and hold circuits 13 and 14 are connected to the amplifier 3b
And 3c at the same time. That is, if the holding time is shifted, the detection accuracy is not improved.

Further, in one embodiment described above, the A / D converter 15
And 16 were used, but since these are generally expensive and large, only one of them is used.
The output voltages of the amplifiers 3b and 3c may be switched and input.

In addition, in the above-described embodiment, an example in which a sine wave is input to the input coil 1a of the resolver 1 has been described, but this may be a triangular wave or a rectangular wave.
The peak detector 12 may output the sample signal at an appropriate timing while the output voltage of the amplifier 3a is at the “H” level. In this case, if the detection angle θ does not change or is slow, a slight shift in the timing of voltage holding in the sample and hold circuits 13 and 14 can be tolerated.

By the way, recently, a CPU (microprocessor) is often used for controlling the above-described AC servomotor,
In such a case, the microprocessor may play the role of the CPU 17 without providing the CPU 17 again.

Recently, when controlling an AC servomotor,
In some cases, the current value is converted to digital data by an A / D converter, and this digital data is input to a microprocessor to perform all digital servo control for controlling the AC servomotor. Instead of providing the converters 15 and 16, an analog multiplexer may be provided before the A / D converter to switch input signals.

As described above, by extending the motor control circuit, there are many components that can be shared, so that the total number of components can be significantly reduced as compared with the related art.

[Effects of the Invention] As described above, according to the present invention, the circuit is simpler than the conventional one and the number of components is significantly reduced, and thus the following effects are obtained.

It is cheap.

Small and lightweight.

High reliability.

High detection accuracy.

Practical application is easy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a rotation angle detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration example of a conventional rotation angle detection device. 1 ... Resolver, 2 ... Sine wave oscillator, 3a-3c ... Amplifier, 12 ... Peak detector, 13,14 ... Sample hold circuit, 15,16 ... A / D converter, 17 ... CPU .

Claims (1)

(57) [Claims] An input coil to which an oscillation signal of a predetermined frequency is applied, and a first coil electrically in phase with the input coil.
A resolver comprising: an output coil having a phase difference of 90 degrees with respect to the input coil; and a peak detector for detecting a peak value of the oscillation signal and outputting a sample signal. A first sample-and-hold circuit for receiving the sample signal and holding a first output voltage induced in the first output coil; and inputting the sample signal simultaneously with the first sample-and-hold circuit. And the second output coil induced by the second output coil
A second sample-and-hold circuit for holding the output voltage, an analog / digital converter for converting the held first and second output voltages into first and second digital data, and inputting the sample signal At the same time, the first and second digital data are inputted, and the first and second digital data are converted into a rotation angle of the resolver = tan ^-1 ((first digital data) / (second digital data) Data)) a control circuit for calculating the rotation angle of the resolver by substituting each into the following expressions: