JP2001289608A - Angle-of-rotation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angle-of-rotation detector which can detect the angle of rotation of rotating equipment with accuracy without being affected by external noise. SOLUTION: Since the angle-of-rotation detecting section 301 of this detector is constituted in such a way that the capacitance of the section 301 changes in accordance with the angle of rotation of a rotating body 303 which rotates together with the rotating equipment, frequency modulating means 310 and 311 respectively having the variable capacitances 306 and 307 of the section 301 in resonance circuits 308 and 309 output frequency-modulated sense signals 402 and 403. Consequently, the sense signals 402 and 403 can be outputted in an arbitrary outputting form and, when the outputting form is set to an emitter follower (source follower) outputting form, etc., a sense signal line can be maintained at a low impedance and can be made to make the entrance of external noise caused by capacitive coupling or inductive coupling difficult. Therefore, this detector can accurately detect the angle of rotation of the rotating equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle detecting device for a motor or other rotating equipment.

[0002]

2. Description of the Related Art Conventionally, as a rotation angle detecting device for detecting a rotation angle and a rotation speed of a rotating device such as a motor,
Resolvers are widely used. The configuration of the resolver is as shown in FIG. 9 and includes a rotation angle detection unit 101 and a rotation angle calculation unit 102. Rotation angle detector 1
01 is an iron core 1 that rotates eccentrically with the rotating shaft of the rotating device
03, an exciting coil 104, and sense coils 105 and 106 arranged so that an angle formed by the rotation center of the iron core 103 and each other is 90 ° in electrical angle.

The shape of the eccentric core 103 is such that an AC signal 110 having a constant frequency ω is applied to the exciting coil 104,
As the iron core 103 rotates, the exciting coil 10
4 using the characteristic that the mutual conductance of the sense coils 105 and 106 changes, the mutual conductance is changed according to the rotation angle θ of the iron core 103.
The mutual conductance up to 05 is set to Msinθ, and the mutual conductance up to the other sense coil 106 is set to Mcosθ.

As shown in FIG. 10, assuming that the voltage applied to the exciting coil 104 is Asinωt (201), the output voltages Vsens1 (202), Vs
ens2 (203) is expressed by the following equation (1).

[0005]

Vsens1 = Asinωt · Msinθ Vsens2 = Asinωt · Mcosθ After passing these output voltages Vsens1 and Vsens2 through the amplifiers 107 and 108, respectively,
The analog variables (MD / A) 109 and 110 multiply the internal variables cos φ and sin φ, and the difference between the obtained results is obtained as shown in Expression 2.

[0006]

[Equation 2] Asinωt · Msinθ · cosφ−Asinωt · Mco
sθ · sinφ = Asinωt · Msin (θ−φ) The synchronous detector 111 detects the difference signal component given by the above equation (2) using the excitation signal component Asinωt (201) applied to the excitation coil 104. The sin (θ-φ) component (204) is derived. Further, this component is integrated by the integrator 112. And φ component generation circuit 1
In step 13, a rotation angle θ is derived by obtaining an integral value 205, that is, an internal variable φ that makes the deviation between the rotation angle θ and the internal variable φ zero. Here, 114 is Ms−cos φ and sin φ obtained based on φ obtained by the φ generation circuit 111.
D / A 109 and 110 are output.

[0007]

However, such a conventional rotation angle detecting device has the following problems.

<Problem 1> As shown in FIG. 11, a detecting unit 101 includes an exciting coil 104 and sense coils 105 and 10.
6, and the coupling constant is about 0.2 due to its structure. Generally, when the coupling constant is at this level, the excitation current is slightly less than 1 mA in order to suppress the loss due to the primary excitation, so that the detection current is several tens μA to 100 μA. The input buffer for converting this weak sense signal into a signal wave of several volts has to be a high-impedance one.
As shown in FIG.
Very easily mixed into 2 'and 203'.

<Problem 2> A resolver is mainly used in combination with an electric motor in many cases, but the electric motor generates current switching noise typified by PWM drive and the like, and surge voltage noise generated when power is turned on and off. Likely to happen. In addition, external noise is mixed in by capacitive or inductive coupling. However, in the conventional rotation angle detecting device, the voltage waveform 20 induced in the sense coils 105 and 106 as shown in FIG.
Since the rotation angle θ is derived by detecting the amplitude components 2 and 203, the amplitude component noise 210 is superimposed on the sense signals 202 ′ and 203 ′ as shown in FIG. An angle output signal 211 to be added at a constant period as shown in FIG. 7A is detected as an unstable angle signal 211 'as shown in FIG. I will.

<Problem 3> Further, as shown in FIG. 14, a low-pass filter 121 having a deep time constant is provided on the sense signal lines from the sense coils 105 and 106 in order to reduce the angle error caused by the noise. , 122 are inserted to block the noise signal. However, in that case, a phase delay occurs in the input signal,
In contrast to the original waveform 221 shown in FIG.
As shown in FIG. 7, the waveform 221 'is delayed.
Therefore, the detection outputs 222 and 222 'are respectively obtained by synchronous detection of these, but the output of the subsequent detection stage is the same as the normal output 223 such as the output 223' with a phase delay. Despite the input of the angle deviation, the output level decreases, and the gain for calculating the rotation angle decreases.

The present invention has been made in view of such conventional problems, and has as its object to provide a rotation angle detecting device which is hardly affected by external noise and can detect a rotation angle with high accuracy. .

[0012]

According to a first aspect of the present invention, there is provided a rotation angle detecting device, comprising: a rotating body that rotates in accordance with the rotation of a rotation angle detection target; and a variable body whose capacity changes according to the rotating angle of the rotating body. A capacitor, an inductor forming a resonance circuit together with the variable capacitor, a frequency modulation unit for frequency-modulating a carrier wave by a resonance frequency of a resonance circuit including the variable capacitor and the inductor, and a frequency output by the frequency modulation unit. Frequency discriminating means for demodulating the modulation signal and outputting a rotation angle detection signal.

According to a second aspect of the present invention, there is provided the rotation angle detecting device according to the first aspect, further comprising a limiting amplification means for limiting and amplifying the frequency modulation signal output from the frequency modulation means and outputting the amplified signal to the frequency discriminating means. Things.

[0014]

According to the rotation angle detecting device of the first aspect of the present invention,
By making the structure of the rotation angle detector a structure in which the capacitance changes in accordance with the rotation angle of the rotating body that rotates together with the rotating device, a frequency modulation wave is output by frequency modulation means having this variable capacitance in the resonance circuit.

Thus, the sense signal output can be configured in any output format. For example, by providing an emitter follower (source follower) output or the like, the sense signal line can be held at low impedance, and capacitive coupling and External noise due to inductive coupling can be hardly mixed, and the rotation angle of the rotating device can be accurately detected.

In the rotation angle detecting device according to the second aspect of the present invention, in addition to the effect of the first aspect, the frequency modulation signal modulated by the frequency modulating means is limitedly amplified by the limiting amplifying means and then demodulated, thereby limiting the frequency. Of the signal input waveform in which the external noise is superimposed on the angle signal by the amplifying means, a signal having a predetermined amplitude or more can be uniformly cut off, whereby unnecessary amplitude change due to the external noise can be removed. As a result, the signal waveform becomes an angle output signal that is faithful to the original waveform, and the output rotation angle can be stabilized by a series of demodulation operations even in an environment with poor external noise.

Further, since the above-described limiting amplification makes it less susceptible to external noise, a low-pass filter circuit having a deep time constant for reducing external noise is not required.
While maintaining the ratio at a high level, angle detection without phase delay becomes possible, and the detection gain in the angle calculation circuit does not decrease, so that stable and accurate angle detection becomes possible.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a circuit configuration of the first embodiment of the present invention. The rotation angle detection device according to the first embodiment includes a rotation angle detection unit 301 and a rotation angle calculation unit 302.

The rotation angle detecting section 301 includes a rotating body 303 having the structure shown in FIG. 2 and coils 304 and 30 disposed at a position 90 ° with respect to the rotating center of the rotating body 303.
5 and a variable capacity 30 that changes with the rotation of the rotating body 303.
6, 307, coils 304, 305 and variable capacitance 30
Frequency modulator 3 that frequency-modulates the carrier wave fc by the resonance frequency of the LC resonance circuits 308 and 309 with the LC resonance circuits 6 and 307.
10, 311 are provided. The rotation angle detection unit 301 further demodulates the frequency-modulated sense signals 402 and 403 from these frequency modulators 310 and 311 to extract signal waves 404 and 405, respectively.
13 is provided. Then, this frequency discrimination circuit 31
2 and 313 are input to the rotation angle calculation unit 302 to determine the rotation angle.

Rotating body 303 and variable capacitors 306 and 307
The structure of the portion is as shown in FIG. 2 and FIG. 3, and a dielectric rotator 502 that rotates with the rotation of the rotation angle detection target such as a motor with respect to the stator electrode 501 is rotatably provided. . The dielectric rotator 502 has the cross-sectional shape shown in FIG. 2B, and the thickness thereof is made unequal so that the gap on the surface facing the stator electrode 501 changes in a sin wave manner according to the rotational position. . The rotating body 3 shown in FIG.
03 are arranged coaxially to output signals of sin θ and cos θ, respectively. That is, the rotor 303
The capacitance between the stator electrode 501 and the dielectric rotator 502 in the variable capacitance 30 in the circuit shown in FIG.
6,307.

The rotation angle calculator 302 has the same internal configuration as in the conventional example.

Next, the operation of the rotation angle detecting device according to the first embodiment having the above configuration will be described. When the rotating body 303 rotates with the rotation of a rotating device such as an electric motor, the variable capacity 3
06 and 307 fluctuate in the form of a sine wave and the other in the form of a cosine wave (hereinafter, for convenience, the variable capacitance 3
The 06 side will be described as a sine wave, and the variable capacitor 307 side will be described as a cosine wave.)

The change in the capacitance of the variable capacitors 306 and 307 causes the variable capacitors 306 and 307 and the coil 30
4 and 305, LC resonance circuits 308 and 309
Similarly fluctuates like a sin wave and a cos wave. Then, the modulators 310 and 311 modulate the carrier wave fc in the frequency axis direction using this resonance frequency, and output frequency modulated waves as shown in FIG. 4 as sense signals 402 and 403.

The frequency discriminators 312 and 313 demodulate the frequency-modulated sense signals 402 and 403 to obtain the original signal waves si.
nθ and cos θ are extracted and input to the rotation angle calculation unit 302. In the rotation angle calculation unit 302, these signal waves sin
The rotation angle θ is obtained from θ and cos θ and output.

As described above, in the rotation angle detecting device according to the first embodiment, the capacitance is changed in a sin wave or a cos wave by the rotation of the rotating body 303 that rotates with the rotation of the rotating device. Change the LC resonance frequency to make the carrier f
c is modulated in the frequency axis direction to take out a sense signal,
Since the original signal waves sinθ and cosθ are taken out by demodulating this, even if the signal amplitude fluctuates due to external noise, it is excellent in noise resistance as long as the carrier frequency is not affected as in FM modulation. The rotation angle can be accurately detected.

The structure of the rotating body 303 is not limited to the above embodiment, but may be a structure shown in FIG. FIG.
Are a rotor 501 and a rotor 502.
Are changed one by one, and the capacitance between them is changed sinusoidally by the change of the overlapping area 503. Two rotating bodies 303 having such a structure are used in the arrangement shown in FIG. You may.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is characterized in that the frequency modulators 310 and 311 and the frequency discriminators 312 and 31 are different from the circuit configuration of the first embodiment shown in FIG.
3, limiting amplifiers 314 and 315 are provided to limit the amplitudes of the sense signals 402 and 403. Note that all other configurations are common to the first embodiment.

According to the rotation angle detecting device of the second embodiment, as shown in FIG.
Even if the external noise 410 is superimposed on the signal 2,403, the signals having a predetermined amplitude 411 or more in the signal input waveform can be uniformly cut off by the limiting amplifiers 312, 313. Can be removed. As a result, the signal waveform becomes a waveform 412 shown in FIG. 13B, an angle output signal faithful to the original signal can be obtained, and a stable rotation as shown in FIG. An angle output signal 211 is obtained.

Next, a rotation angle detecting device according to a third embodiment of the present invention will be described. FIG. 8 shows a circuit configuration of the third embodiment. This shows the rotation angle detection unit 301 of the first embodiment shown in FIG. 1 using more specific circuit elements. Reference numeral 303 denotes a rotator having the structure shown in FIG. 2 or FIG. 5, 306 and 307 denote variable capacitances that change with rotation of the rotator 303, 304 and 305 denote inductors such as coils, and Tr1 and Tr2 denote frequency modulators 31.
Oscillation transistors 0 and 311 and C1 and C2 are carrier wave oscillation capacitors. The sense signal 40 from the frequency modulators 310 and 311 in the circuit shown in FIG.
Reference numerals 2 and 403 are input to the frequency discriminators 312 and 313 in the circuit configuration shown in FIG. 1 or the limiting amplifiers 314 and 315 in the circuit configuration shown in FIG.

Next, the operation of the third embodiment will be described. Rotating body 3 attached to a motor or other rotating equipment
When 03 rotates, the capacity of the variable capacitors 306 and 307 changes according to the rotation angle θ. Thereby, the variable capacitance 30
6,307 and inductors 304,305
The resonance frequencies of the C resonance circuits 308 and 309 change as Asin θ and Acos θ depending on the rotation angle θ. The resonance frequency at this time is such that the carrier frequency component fc is oscillated by the capacitors C1 and C2 and the inductors 304 and 305, and the variable capacitor 3
06 and 307, the oscillation frequencies of the resonance circuits 308 and 309 are modulated on the frequency axis, and the signal frequencies are changed to Asinθ and Ac.
os θ, the modulated signal fm is centered on the carrier frequency fc, fm = fc ± Δfsinθ; fm = f
The frequency becomes c ± Δfcosθ. Then, the frequency modulation signal is output as sense signals 402 and 403.

Thus, in the rotation angle detecting device according to the third embodiment, as in the first embodiment or the second embodiment, a rotation angle detection signal which is hardly affected by external noise is output. it can.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram according to a first embodiment of the present invention.

FIG. 2 is a perspective view and a cross-sectional view illustrating a structure of a rotating body in the embodiment.

FIG. 3 is an explanatory diagram showing a structure of a rotation angle detection unit in the embodiment.

FIG. 4 is a waveform diagram of a frequency modulation sense signal according to the embodiment.

FIG. 5 is a front view showing the structure of another rotating body that can be used in the above embodiment.

FIG. 6 is a circuit block diagram according to a second embodiment of the present invention.

FIG. 7 is a signal waveform diagram showing a frequency-modulated sense signal and a waveform after limiting amplification thereof according to the embodiment.

FIG. 8 is a circuit diagram of a rotation angle detection unit according to a third embodiment of the present invention.

FIG. 9 is a circuit block diagram of a conventional example.

FIG. 10 is a signal waveform diagram of each section when there is no noise in the conventional example.

FIG. 11 is an explanatory view showing coupling of an exciting coil and a sense coil according to a conventional example.

FIG. 12 is a waveform diagram of a sense signal affected by external noise in a conventional example.

FIG. 13 is a waveform chart showing a rotation angle detection signal in a conventional example in a case where it is not affected by external noise and in a case where it is received.

FIG. 14 is a circuit block diagram of another conventional example.

FIG. 15 is a waveform diagram of each section in the above conventional example when the time constant is not affected.

FIG. 16 is a waveform diagram of each section in the above conventional example when affected by a time constant.

[Explanation of symbols]

 301 Rotation angle detector 302 Rotation angle calculator 303 Rotator 304 Coil 305 Coil 306 Variable capacitance 307 Variable capacitance 308 Resonance circuit 309 Resonance circuit 310 Frequency modulator 311 Frequency modulator 312 Frequency discriminator 313 Frequency discriminator 314 Limiting amplifier 315 Limitation Amplifier 501 Stator electrode 502 Dielectric rotator

Claims (2)

[Claims] A rotating body that rotates with rotation of a rotation angle detection target; a variable capacitor whose capacity changes according to a rotation angle of the rotating body; an inductor that forms a resonance circuit together with the variable capacitor; Frequency modulating means for modulating the frequency of a carrier wave with a resonance frequency of a resonance circuit composed of a variable capacitor and an inductor; frequency discriminating means for demodulating a frequency modulation signal output from the frequency modulation means and outputting a rotation angle detection signal A rotation angle detecting device comprising: 2. The rotation angle detecting device according to claim 1, further comprising a limiting amplifier for limiting and amplifying the frequency modulation signal output from the frequency modulator and outputting the amplified signal to the frequency discriminator.