JP3381736B2 - Optical encoder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a rotational angle position of a motor and an optical encoder to which the method is applied.

[0002]

2. Description of the Related Art Conventionally, in this type of optical encoder, a phase difference detection method has been known as a method for multiplying the position of an optical encoder signal within one pitch. In this method, an A-phase signal (SINθ) and a B-phase signal (COSθ) whose phases are deviated from each other by 90 ° within one pitch of the signal are multiplied by carrier signals COSωt and SINωt, respectively, and a sum signal SIN (ω
t + θ) is generated, the phase difference θ between the sum signal SIN (ωt + θ) and the carrier signal SINωt is detected, and the current position information within one pitch is obtained. FIG. 7 is a block diagram showing a conventional example of an optical encoder adopting the above-mentioned phase difference detection method. The light receiving elements 161 and 162 that receive the light of the light emitting source 130 that has passed through the main scale 150 and the index scale 140 generate an A phase signal (SINθ) and a B phase signal (COSθ) that are 90 ° out of phase with each other. ,
It is output to the multipliers 171 and 172, respectively. Multiplier 1
71 and 172 multiply the carrier signals COSωt and SINωt output from the two-phase oscillator 170 by the A-phase signal (SINθ) and the B-phase signal (COSθ), respectively. The summing amplifier 173 adds the outputs of the multipliers 171 and 172,
The sum signal SIN (ωt + θ) represented by the following equation (1) is output.

COSθ * SINωt + SINθ * COSωt = SIN (ωt + θ) (1) Comparators 175 and 176 are sum signals SIN (ωt +
θ) and the carrier signal SINωt are converted into pulse signals. The difference between the rising edges of these two pulse signals corresponds to the phase difference θ. The counter 177 is the comparator 1
From the rise of the output of 76 to the rise of the output of the comparator 175, the clock signal from the clock 178 is counted, and the current position information 180 within one pitch can be obtained as a digital value.

[0004]

The conventional optical encoder described above can stably output the carrier signals COSωt and SINωt in the method of multiplying the position to be detected, and the phase difference between the outputs can be exactly 90 °. A two-phase oscillator that can be maintained is required. Since the characteristics of this two-phase oscillator greatly affect the accuracy of the position to be detected, it is important to maintain this characteristic, but in order to realize it, the circuit configuration of the two-phase oscillator becomes complicated. There's a problem. In view of the above problems, it is an object of the present invention to provide an optical encoder that can accurately give a position within one pitch with a simple circuit configuration that does not use a two-phase oscillator.

[0005]

A rotation angle position detecting method for an optical encoder according to the present invention corresponds to a crest value of a drive signal f (ωt) other than a sine wave having a constant frequency ω with positive and negative peak values being symmetrical. Two lines of light with light intensity are emitted, and the two lines of emitted light are passed through the translucent slit of the rotating main scale, and the rotation angle position of the main scale is θ, and V
Is a constant, the signal V1 = V * f (ωt) * SINθ and the signal V2 = V * f (ωt) * COSθ are generated, and the drive signal f
Resolver / digital conversion is performed on the signals V1 and V2 based on (ωt), and digital angular position data corresponding to the rotational angular position θ is output. Preferably, the drive signal f (ωt) is a rectangular wave signal . Further, the optical encoder of the present invention receives a drive signal f (ωt) from a signal source and a drive source f (ωt) that outputs a drive signal f (ωt) having a constant frequency ω with positive and negative peak values being symmetric, and outputs the drive signal A first light emitting circuit that causes the first or second light emitting diode to emit light in accordance with the positive or negative polarity of f (ωt), and the drive signal f from the signal source.
(Ωt) is input, and a second light emitting circuit that causes the third or fourth light emitting diode to emit light in accordance with the positive or negative polarity of the drive signal f (ωt) and a disk shape that rotates about the center point are provided. The first and second transparent slits arranged along the circumference.
When the main scale that passes through the light passage from the light emitting circuit of the first scale and the light from the first light emitting circuit that passes through the translucent slit of the main scale are received and the rotation angle of the main scale is θ, V Is a constant V1 = V * f (ωt) * SIN
When the light from the first light receiving element that outputs θ and the light from the second light emitting circuit that has passed through the translucent slit of the main scale is received and the rotation angle of the main scale is θ degrees, the signal V2 = V *
The second light receiving element that outputs f (ωt) * COSθ and the drive signals and the signals V1 and V2 are input, and 1 for the rotation angle θ
A resolver / digital converter that outputs angular position data within a pitch as a digital output. Preferably, a sine wave signal or a rectangular wave signal is used as the drive signal f (ωt).

[0006]

The first and second light emitting circuits are driven by the drive signal f (ωt) to emit light. The first and second light emitting circuits face the first and second light receiving elements via the main scale, respectively. The first set of the light emitting circuit and the light receiving element are out of phase with each other by 90 ° with respect to the second set of the light emitting circuit and the light receiving element and the translucent slit of the main scale. Therefore, in the first and second light receiving elements, when the rotation angle of the first main scale is θ, the signal V1 = V * f (ωt) * SINθ or the signal V2 = V * f, where V is a constant.
Output (ωt) * COSθ. The resolver / digital converter resolves signals V1 and V2 based on the drive signal.
Digital conversion is performed, and angular position data within one pitch with respect to the rotation angle θ is output as a digital output.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. 1 is a block diagram showing an optical encoder of the present invention, FIG. 2 is a block diagram showing a resolver / digital converter in the embodiment of FIG. 1, and FIG.
FIG. 4 is a block diagram showing a C-bridge, and FIG. 4 is a waveform diagram showing signals of respective parts in the embodiment of FIG. Sine wave signal source 10
Applies a sinusoidal signal SG (see FIG. 4C) between the nodes P and N. The light emitting circuit 20 includes a light emitting diode 21 having an anode connected to the node P, a cathode and an anode, a diode 23 connected to the anode and the cathode of the light emitting diode 21, and a cathode connected to the cathode of the light emitting diode 21. Includes a light emitting diode 22 connected to the node N, and a diode 24 whose anode and cathode are connected to the cathode and anode of the light emitting diode 22, respectively.

The light emitting circuit 30 includes a light emitting diode 31 whose anode is connected to the node P, a cathode and an anode which are respectively connected to the anode and the cathode of the light emitting diode 31, and a cathode which is connected to the cathode of the light emitting diode 31. The light emitting diode 32 has an anode connected to the node N, and a diode 34 having an anode and a cathode connected to the cathode and the anode of the light emitting diode 32, respectively. The light emitting diodes 21, 22, 31, of the light emitting circuits 20, 30
The light of 32 passes through the translucent slits of the index scale 40 and the main scale 50, and the light receiving elements 61,
The light is received by 62. The light received by the light receiving elements 61, 62 from the light emitting diodes 21, 31 is arranged so that the phase shifts by 90 ° within one pitch of the optical encoder. The light received by the light receiving element 61 from the photodiodes 21 and 22 is arranged so that the phase is shifted by 180 ° within one pitch of the optical encoder. From the photodiodes 31 and 32 to the light receiving element 6
The light received by 2 has a phase of 1 within one pitch of the optical encoder.
They are arranged so that they are offset by 80 °. When the polarity of the sine wave signal source 10 at the node P is positive with respect to the node N, the light emitting diodes 21 and 31 emit light, and when the polarity is negative, the light emitting diodes 22 and 32 emit light.

Therefore, from the light emitting circuit 20 to the light receiving element 6
For example, if light that changes in a sine wave shape is emitted through the scales 40 and 50, light that changes in a cosine wave shape is emitted from the light emitting circuit 30. However, if the main scale 50 is tilted from the reference position by the angle θ, the cosine or sine of the angle θ is multiplied by the light received from the light emitting circuit 20 or the light emitting circuit 30 to output the output signals SX, SY of the light receiving elements 61, 62. (Fig. 4 (a),
(See (b)). The resolver / digital converter 70 (hereinafter abbreviated as R / D converter 70) resolves / digital-converts the signals SX and SY based on the signal SG, and outputs a digital signal 80 indicating a position within one pitch.
Is output. As a specific example, as shown in FIG. 2, for R / D conversion, the R / D converter 70 includes an AC bridge 71, a phase detection demodulator 72, an up / down counter 73, an up / down VCO 74, and an integrator 75. ing. In addition, the AC bridge 71
3, is composed of a buffer 711, a COS multiplication circuit 713, a SIN multiplication circuit 714, and a subtraction circuit 715.

If the sine wave signal source 10 outputs SINωt to the R / D converter 70 having such a configuration and the main scale 50 is rotating by the rotation angle θ,
The buffer circuit 711 of the AC bridge 71 of the R / D converter 70 is provided with inputs V1 and V2 represented by the following equations (2) and (3) (SINωt is SINθ or COSθ).
It is in the form of amplitude modulation). V1 = V * SINωt * SINθ (2) V2 = V * SINωt * COSθ (3) where V is the constant buffer circuit 711 within the four quadrants of these signals. Of one of the outputs of (1) (this is for simplifying the circuit and is not directly related to the present invention, so no further description will be given), and The digital value is input from the up / down counter 73, and the COS multiplication circuit 713 and the SIN multiplication circuit 714 input V1 and V
2 is multiplied by COSφ and SINφ respectively, and the following equation (4),
(5) is obtained.

V11 = V * SINωt * SINθ * COSφ (4) V22 = V * SINωt * COSθ * SINφ (5) The subtraction circuit 715 subtracts V22 from V11, The following equation (6) representing the AC position error is obtained. V3 = V * SINωt * SIN (θ−φ) (6) The phase detection demodulator 72 converts the output V3 of the AC bridge 71 to SI.
It demodulates using Nωt and outputs it as a DC position error. D
The C position error is calculated by the integrator 75 and the up / down VCO 7
The count value of the up / down counter 73 is changed via 4 until SIN (θ−φ) of the third term on the right side of the equation (6) becomes 0, that is, θ = φ. When θ = φ, the accurate position data 80 is updated by the up / down counter 73.
Will be output more. In this case, since the phase detection demodulator 72 uses the sine wave signal output of the sine wave signal source 10 for demodulation, a highly accurate one such as a two-phase oscillator is not required.

Also, unlike the embodiment of FIG. 1, similar results are obtained when a square wave signal source 90 is used instead of the sine wave signal source 10 as in the second embodiment of FIG. Can be obtained. FIG. 6 shows the signal of each part in this case.

[0013]

As described above, according to the present invention, the first and second light emitting circuits are caused to emit light by the drive signal f (ωt), which is an alternating signal, and a sine wave based on the rotation angle θ of the main scale is generated. Amplitude modulation by cosine wave is applied, and signal V1 = V *
f (ωt) * SINθ and signal V2 = V * f (ωt) * COSθ
And generate signals V1 and V based on the drive signal f (ωt).
Resolver / digital convert 2 and output digital angular position data corresponding to rotation angle θ, so the rotation angle of the main scale within 1 pitch of the optical encoder signal does not require a two-phase oscillator with a complicated circuit configuration. It is possible to accurately digitally output the angular position data indicating.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical encoder of the present invention.

FIG. 2 is a block diagram showing an R / D converter in the embodiment of FIG.

3 is a block diagram showing an A / C bridge in FIG. 2. FIG.

4 (a), (b) and (c) are waveform charts showing signals of respective parts of the embodiment of FIG.

FIG. 5 is a block diagram showing a second embodiment of the optical encoder of the present invention.

6 (a), (b), and (c) are waveform diagrams showing signals of respective parts of the embodiment of FIG.

FIG. 7 is a block diagram showing a conventional example.

[Explanation of symbols]

10 Sine wave signal source 20,30 Light emitting circuit 21,22,31,32 light emitting diodes 23, 24, 33, 34 Diode 40 index scale 50 main scale 61,62 Light receiving element 70 R / D converter 71 AC bridge 72 Phase detection demodulator 73 Up-down counter 74 Up Down VCO 75 integrator 80 position data 711 buffer 713 COS multiplication circuit 714 SIN multiplication circuit 715 Subtraction circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01D 5/26-5/38 G01B 11/00-11/30

Claims (2)

(57) [Claims] 1. A signal source for outputting a drive signal f (ωt) having a constant frequency ω with positive and negative peak values being symmetric, and a drive signal f (ωt) from the signal source, and the drive signal f
A first light emitting circuit that causes the first or second light emitting diode to emit light in accordance with the positive or negative polarity of (ωt), and a drive signal f (ωt) from a signal source is input, and the drive signal f
A second light-emitting circuit that causes the third or fourth light-emitting diode to emit light in accordance with the positive or negative polarity of (ωt); and a disk shape that rotates about the central point as an axis, and is arranged along the circumference. The main scale which passes the light passage from the first and second light emitting circuits through the light transmitting slit and the light from the first light emitting circuit which passes through the light transmitting slit of the main scale are received and When the rotation angle is θ, the first light receiving element that outputs the signal V1 = V * f (ωt) * SINθ with V as a constant and the second light emitting circuit that passes through the translucent slit of the main scale The second which receives light and outputs a signal V2 = V * f (ωt) * COSθ when the rotation angle of the main scale is θ degrees
And an resolver / digital converter that receives the drive signals and the signals V1 and V2 and outputs the angular position data within one pitch with respect to the rotation angle θ as a digital output. Wherein said driving signal f (.omega.t) optical encoder according to claim 1, which is a sine wave signal or a rectangular wave signal.