JP5098699B2 - Encoder signal processing circuit - Google Patents

Description

  The present invention relates to a signal processing circuit that generates position data from a two-phase sine wave signal in an encoder position detection system that increases resolution by interpolating two orthogonal sine wave signals (A phase and B phase). .

  The position detection of a rotary (or linear) encoder is generally made up of a light emitting element, a light receiving element, and a rotating body (or moving body) with a grid-like slit formed between them. Resolution is determined.

  Therefore, in order to increase the resolution, the slit interval has been reduced, but there is a limit to increasing the resolution by this method due to processing accuracy and light diffraction phenomenon.

  In recent years, A and B phase sine wave analog signals having a phase difference of 90 degrees synchronized with signals between slits of a rotating body (or a moving body) are generated, and the signal obtained by interpolating the analog signals and the slits described above Generally, a method of increasing the resolution by synthesizing the signals obtained by the above method is performed.

  However, when the A-phase and B-phase sine wave signals are converted to digital data by the AD converter, the amount of change in the voltage level with respect to the angle is small near the upper and lower vertices of the sine wave signal, and the rounding error due to digitization increases. Since the detection accuracy deteriorates, for example, the following proposal has been made in order to suppress a decrease in accuracy of position data.

  FIG. 11 is a method for obtaining position data from the A-phase and B-phase sinusoidal signals using linearly inclined portions (portions other than the top and bottom vertices). The angle data of the A-phase and the B-phase are expressed as A-phase. The position data is obtained by switching at the intersection of the B phases (for example, see Patent Document 1).

Further, FIG. 12 shows the distribution coefficient to each angle data from two sine wave signals of A = COSθ and B = SINθ, (B2 / (A2 + B2)) COS-1A + (A2 / (A2 + B2)) SIN− This is a method for calculating position data by calculating from 1B (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 9-005402 JP 2003-021540 A

  In the method of Patent Document 1, the angle data of the A phase and the B phase are influenced by the influence of the amplitude error that cannot be corrected to the A phase and B phase sine wave signals, the phase error, and the harmonic component superimposed on the sine wave signal. There is a problem in that the continuity is lost when switching between and the distortion occurs at the switching point.

  On the other hand, in the method of Patent Document 2, since the coefficients of the two angle data COS-1A and SIN-1B are calculated using both COSθ and SINθ, information with poor signal accuracy is included near the apex of each signal. ing. Therefore, there is a problem that the accuracy of the position data calculated by this coefficient also deteriorates.

  The present invention solves the above-described conventional problems, and even if an amplitude error or phase error that cannot be corrected occurs in the A-phase and B-phase sine wave signals, an encoder of high position detection accuracy can be obtained by simple arithmetic processing. An object is to provide a signal processing circuit.

  In order to solve the above-mentioned problem, the signal processing circuit of the encoder according to claim 1 detects the position by performing inverse trigonometric function conversion on the orthogonal AB-phase sine wave signal A0 and sine wave signal B0, respectively, and converting them into angle signals. In the encoder interpolation method, the sine wave signal A0 and the sine wave signal B0 are separately input, and angle conversion means for converting the sine wave signal into the angle signal A2 and the angle signal B2 by inverse trigonometric function conversion, respectively, The sine wave signal A0 and the sine wave signal B0 are inputted and the inverting means for generating the inverted signal A1 and the inverted signal B1 whose signs are inverted, the sine wave signal A0, the sine wave signal B0, the inverted signal A1, and the inverted signal B1. Input, detect each intersection, select a signal with a small absolute value of the signal from the intersection to make a continuous line, and generate a synthesized angle signal AB0 to obtain angle information from the value of the continuous line And a distribution coefficient conversion means for inputting the composite angle signal AB0, calculating a distribution coefficient KA1 and a distribution coefficient KB1 for multiplying the angle signal A2 and the angle signal B2, and outputting them respectively, and the angle signal A2 And the distribution coefficient KA1, the angle signal B2 and the distribution coefficient KB1 are respectively input, the multiplication data A3 and the multiplication data B3 are respectively output, the multiplication data A3 and the multiplication data B3 are input, and average processing is performed. The distribution coefficient converting means distributes all the angle values obtained from the combined angle signal AB0 so that the sum of the distribution coefficient KA1 and the distribution coefficient KB1 is equal.

  The encoder signal processing circuit according to claim 2, wherein the distribution coefficient KA1 is a value that repeats maximum and minimum every π / 2 radians from the combined angle signal AB0, and the distribution coefficient KA1 and the distribution coefficient KB1 has a width that is at least twice as large as the angle calculation resolution of the combined angle signal AB0 in each of the maximum and minimum areas.

  In the encoder signal processing circuit according to a third aspect, the distribution coefficient KA1 can connect the angle between the maximum value and the minimum value with a straight line.

  According to a fourth aspect of the present invention, there is provided a signal processing circuit for an encoder having an intermediate value of ½ of the distribution coefficient KA1 having a width more than twice the angle calculation resolution of the combined angle signal AB0.

  In the encoder signal processing circuit according to the fifth aspect, the distribution coefficient KA1 can be obtained by connecting the angles between the maximum value and the intermediate value and between the intermediate value and the minimum value with a straight line.

  Further, the signal processing circuit of the encoder according to claim 6 inputs the composite angle signal AB0 and outputs the composite angle signal AB1 in which the signal size is limited by the upper limit value and the lower limit value to the distribution coefficient conversion means. Upper and lower limit means are further provided.

  According to the signal processing circuit of the encoder according to the first aspect, since the distribution coefficient is obtained using the synthesized angle signal AB0 with high detection accuracy, the conversion accuracy into position data can be improved.

  Further, according to the signal processing circuit of the encoder according to claim 2, the distribution coefficient is set so that the maximum value and the minimum value have a width more than twice the angular resolution of the composite angle signal AB0. Even when there is an error, an amplitude error, or distortion of a sine wave signal, it is possible to suppress a decrease in conversion accuracy to position data.

  According to the signal processing circuit of the encoder according to claim 3, since the distribution coefficient is set by connecting the angle between the maximum value and the minimum value with a straight line, the position data obtained by the synthesis changes smoothly. The occurrence of discontinuous points can be suppressed.

  Further, according to the signal processing circuit of the encoder according to claim 4, in order to set the intermediate value of ½ of the distribution coefficient so as to have a width more than twice the angular resolution of the composite angle signal AB0, Furthermore, even when there is a phase error, an amplitude error, or distortion of a sine wave signal, it is possible to suppress a decrease in conversion accuracy to position data.

  Further, according to the signal processing circuit of the encoder according to claim 5, since the angle between the maximum value and the intermediate value, and the angle between the intermediate value and the minimum value are connected and set by a straight line, the position data obtained by further synthesis is It changes smoothly and the occurrence of discontinuities can be suppressed.

  Furthermore, according to the signal processing circuit of the encoder of the sixth aspect, when the upper limit value and the lower limit value limit means are provided in the composite angle signal AB0, there is further a phase error, an amplitude error, and a sine wave signal distortion. In addition, it is possible to suppress a decrease in conversion accuracy to position data.

In the interpolation processing method of the encoder that detects the position by performing inverse trigonometric function conversion on the orthogonal AB-phase sine wave signal A0 and sine wave signal B0 to an angle signal, respectively, the sine wave signal A0 and sine wave signal B0 are Separately input, angle conversion means for converting the sine wave signal into the angle signal A2 and the angle signal B2 by inverse trigonometric function conversion, and the inverted signal obtained by inverting the sign by inputting the sine wave signal A0 and the sine wave signal B0. The inverting means for generating A1 and the inverted signal B1, the sine wave signal A0, the sine wave signal B0, the inverted signal A1 and the inverted signal B1 are input, the respective intersections are detected, and the absolute value of the signal is small from the intersection. A composite angle detection means for generating a composite angle signal AB0 that obtains angle information from the value of the continuous line, and the composite angle signal AB0 are input. A distribution coefficient conversion means for calculating and outputting a distribution coefficient KA1 and a distribution coefficient KB1 for multiplying A2 and the angle signal B2, respectively, the angle signal A2 and the distribution coefficient KA1, and the angle signal B2 and the distribution coefficient KB1; A multiplier for outputting the multiplication data A3 and the multiplication data B3; and a synthesizing unit for inputting the multiplication data A3 and the multiplication data B3 and averaging them to generate the position data θ1, wherein the distribution coefficient conversion unit The sum of the distribution coefficient KA1 and the distribution coefficient KB1 is the same for all angle values obtained from the angle signal AB0, and the maximum and minimum values are repeated every π / 2 radians. The decomposition coefficients KA1 and KB1 are respectively An encoder having a structure having a width more than twice the angle calculation resolution of the composite angle signal AB0 in the maximum, minimum, and intermediate regions It is an issue processing circuit. Hereinafter, embodiments will be described with reference to the drawings.
(Embodiment 1)
The signal processing circuit of the encoder according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a signal processing circuit for converting two-phase sine wave signals into position data, and FIGS. 2 to 4 show operation waveforms of the respective blocks.

  In FIG. 1, the inverting means 1 receives a sine wave signal A0 and a sine wave signal B0, and generates an inverted signal A1 and an inverted signal B1. The combined angle detector 2 receives the sine wave signal A0, the sine wave signal B0, the inverted signal A1, and the inverted signal B1, and generates a combined angle signal AB0 for obtaining angle information. The sine wave signal A0 and the sine wave signal B0 are input to the angle conversion means 3a (angle conversion means 3b), and converted into an angle signal A2 (angle signal B2) by inverse trigonometric function conversion.

  The distribution coefficient conversion means 4 receives the combined angle signal AB0, calculates a distribution coefficient to multiply the angle signal A2 and the angle signal B2, and outputs the distribution coefficient KA1 to the multiplier 5a and the distribution coefficient KB1 to the multiplier 5b. . The multiplier 5 a (multiplier 5 b) receives the angle signal A 2 (angle signal B 2) and the distribution coefficient KA 1 (distribution coefficient KB 1), and outputs the multiplication data A 3 (multiplication data B 3) to the combining means 6. The synthesizing means 6 averages the input multiplication data A3 and multiplication data B3 to generate position data θ1.

  Here, the sine wave signal A0 and the sine wave signal B0 are normalized sine wave signals with a phase difference of 90 degrees, and are orthogonal A phase and B phase analog sine wave signals detected by the encoder signal detector. Can be obtained by digitally converting and correcting amplitude deviation, offset deviation and phase deviation.

  The signal detector of the encoder is generally composed of a light emitting element, a light receiving element, and a slit plate. The light emitting element is an LED or a laser beam, and the light receiving element is a photodiode or a phototransistor. The slit plate is made of glass or a resin material that transmits light, and a lattice-like mask that blocks light is provided on the slit plate. The light from the light emitting element is arranged to receive the light transmitted by the light receiving element through the slit plate, and the slit plate is installed on the rotating body of the encoder. Thus, a lattice-like shape of the slit plate is formed.

  Here, the operation of the composite angle detection means 2 will be described with reference to FIG. Both the sine wave signal A0 and the sine wave signal B0 are input to the combined angle detection means 2 together with the inverted signal A1 and the inverted signal B1 that are inverted. The intersection (C315, C45, C135, C225) of each signal is obtained, and one period is divided into four regions (region 1 to region 4) with the intersection as a base point.

  Region 1 starts from the intersection C315 of the sine wave signal A0 and the inverted signal B1, passes through the locus of the sine wave signal A0, and reaches the intersection C45 of the sine wave signal A0 and the sine wave signal B0. Region 2 starts from the intersection C45, passes through the locus of the sine wave signal B0, and reaches the intersection C135 of the inverted signal A1 and the sine wave signal B0. The region 3 starts from the intersection C135, passes through the locus of the inverted signal A1, and reaches the intersection C225 of the inverted signal A1 and the inverted signal B1. The region 4 starts from the intersection C225, passes through the locus of the inverted signal B1, and reaches the intersection C315 of the sine wave signal A0 and the inverted signal B1.

  By following the trajectory of each signal with the intersection as the base point in this way, the synthesized angle signal AB0 can be generated as shown in FIG. Further, the synthesized angle signal AB0 may be a signal obtained by combining the synthesized angle signal with the signals of the respective regions (the signals from the intersections of the signals).

  Next, operations of the angle conversion means 3a and the angle conversion means 3b will be described with reference to FIG. The angle conversion means 3a receives the sine wave signal A0 and the sine wave signal B0, and converts the sine wave signal A0 into angle data A2 by inverse trigonometric function conversion. Since the inverse trigonometric transformation is calculated in the region of −π / 2 radians to π / 2 radians, when the sine wave signal B0 is positive as shown in FIG. 3 (−π / 2 radians to π / 2 radians). , Calculation is performed separately when negative (π / 2 radians to 3π / 2 radians).

  Similarly, the angle conversion means 3b calculates the sine wave signal B0 separately when the sine wave signal A0 is positive (0 radians to π radians) and negative (π radians to 2π radians). In this way, by using a sine wave signal having a phase difference of 90 degrees, inverse trigonometric function conversion from 0 radians to 2π radians can be easily obtained.

  Next, the distribution coefficient converting means 4 will be described with reference to FIG. The distribution coefficient conversion means 4 receives the composite angle signal AB0 from the composite angle detection means 2, and obtains a distribution coefficient KA1 and a distribution coefficient KB1. The distribution coefficient KA1 and the distribution coefficient KB1 are selected so that the sum of the distribution coefficients KA1 and KB1 is equal in an angle region from 0 radians to 2π radians.

For example, FIG. 3 shows a case where the maximum value of the distribution coefficient is KK. When 0 radians, KA1 = KK and KB1 = 0, and when π / 4 radians, KA1 = KK / 2 and KB1 = KK / 2.
Thus, when π / 2 radians, KA1 = 0 and KB1 = KK / 2. The values of the distribution coefficients KA1 and KB1 can be easily obtained without performing complicated calculations by setting in advance in a ROM (Read Only Memory) using the combined angle signal AB0 as an address.

  Next, the multiplier 5a, the multiplier 5b, and the synthesizing means 6 will be described. The multiplier 5a (multiplier 5b) multiplies the angle data A2 (angle data B2) and the distribution coefficient KA1 (distribution coefficient KB1) to obtain multiplication data A3 (multiplication data B3). The synthesizing means 6 can obtain the position data θ1 by obtaining the average value of the multiplication data A3 and the multiplication data B3.

  Here, a method for setting the distribution coefficient KA1 and the distribution coefficient KB1 will be described. When the sine wave signal A0 and the sine wave signal B0 are differentiated by angle, the values of π / 2 radians, 3π / 2 radians, 0 radians, and π radians in the vicinity of the apex become small. The obtained angle data A2 and B2 have poor accuracy at the circled portions shown in FIG. As shown in FIG. 3, the distribution coefficients KA1 and KB1 are selected so as to be the minimum in the vicinity of the circle, so that the accuracy of conversion into position data can be increased.

  Further, corrected signals are used as the sine wave signal A0 and the sine wave signal B0. However, an error occurs in the combined angle signal AB0 due to an error that cannot be corrected or a waveform distortion. In such a case, since the distribution coefficient KA1 and the distribution coefficient KB1 do not become zero in a region where the accuracy of the angle data A2 and the angle data B2 is poor, the synthesized position data θ1 includes information on the angle data with poor accuracy. End up.

  Therefore, as shown in FIG. 4, the maximum value and the minimum value of the distribution coefficient KA1 and the distribution coefficient KB1 are set so as to have a width more than twice the angular resolution of the composite angle signal AB0. By setting in this way, the allowable error of the combined angle signal AB0 can be doubled or more.

The distribution coefficient KA1 and the distribution coefficient KB1 may be set by connecting the angle between the maximum value and the minimum value with a straight line. In this case, since the distribution coefficient KA1 and the distribution coefficient KB1 change continuously, the position data obtained by the synthesis changes smoothly and the occurrence of discontinuous points can be suppressed (second embodiment).
A second embodiment of the present invention will be described with reference to FIG. What is different from the first embodiment is a method of setting the distribution coefficient KA1 and the distribution coefficient KB1, and this point will be described.

  The distribution coefficient KA1 and the distribution coefficient KB1 repeat the maximum value and the minimum value every π / 2 × n radians (n: 0, 1, 3, 4), but this intermediate point π / 4 × n radians (n: 0) 1, 3, 4, 5, 6, 7), it is preferable to take an intermediate value (maximum value / 2) in order to balance both. When the sine wave signal A0 and the sine wave signal B0 do not include an amplitude or phase error, the method of the first embodiment is used to obtain π / 4 × n radians (n: 0, 1, 3, 4, 5, 6 7), the distribution coefficient KA1 and the distribution coefficient KB1 are intermediate values.

However, since the sine wave signal A0 and the sine wave signal B0 have errors in the combined angle signal AB0 due to uncorrectable errors and waveform distortion, the intermediate value of the distribution coefficient KA1 and the distribution coefficient KB1 is the intermediate value of the combined angle signal AB0. It is set so as to have a width more than twice the angular resolution. By setting in this way, the allowable error of the combined angle signal AB0 can be doubled or more, so that the position data obtained by combining changes more smoothly and suppresses the occurrence of discontinuous points. Can do.
(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIG. 8, FIG. 9, and FIG. The difference from the first embodiment and the second embodiment is that the combined angle signal AB0 is provided with limit processing of the maximum value and the minimum value by the upper and lower limit means 7, and this operation will be described.

  As shown in FIG. 8, the upper and lower limit means 7 is provided between the composite angle conversion means 2 and the distribution coefficient conversion means 4 and receives the composite angle signal AB0 and performs the maximum and minimum value limit processing. The signal AB1 is output.

  In the sine wave signal A0 and the sine wave signal B0, an error occurs in the combined angle signal AB0 due to an error that cannot be corrected or an influence of waveform distortion. FIGS. 9 and 10 are examples in the case where there is a phase error in the sine wave signal A0 and the sine wave signal B0, and the combined angle signal AB0 is a normal value of π / 4 radians and 3π / 4 radians. It exceeds sin (π / 4).

  In this way, when the limit value is exceeded, the limit value is used to limit the result, and the result is input to the distribution coefficient conversion means 4 as the synthesized angle signal AB1.

  For example, taking the configuration of the first embodiment as an example, the distribution coefficient KA1 and the distribution coefficient KB1 are as shown in FIG. Taking the configuration of the second embodiment as an example, the distribution coefficient KA1 and the distribution coefficient KB1 are as shown in FIG. 10. In either case, the influence of the phase error of the sine wave signal A0 and the sine wave signal B0 is affected. Can absorb and maintain continuity. The position data obtained by the synthesis changes more smoothly, and the occurrence of discontinuous points can be suppressed.

  The signal processing circuit of the present invention is useful not only for servo motor control devices but also for devices equipped with an encoder for obtaining high-resolution position information.

1 is a block diagram of a signal processing circuit according to Embodiment 1 of the present invention. Explanatory drawing (1) of the signal waveform in each block of Embodiment 1 Explanatory drawing (2) of the signal waveform in each block of Embodiment 1 Explanatory drawing (3) of the signal waveform in each block of Embodiment 1 Explanatory drawing (4) of the signal waveform in each block of Embodiment 1 Explanatory drawing (5) of the signal waveform in each block of Embodiment 1 Explanatory drawing of the signal waveform in each block of the second embodiment Block diagram of a signal processing circuit in Embodiment 3 Explanatory drawing (1) of the signal waveform in each block of Embodiment 3 Explanatory drawing (2) of the signal waveform in each block of Embodiment 3 Block diagram of signal processing circuit in conventional example (1) Block diagram of signal processing circuit in conventional example (2)

Explanation of symbols

A0, B0 Sine wave signal A1, B1 Inverted signal A2, B2 Angle data A3, B3 Multiplication data AB0, AB1 Composite angle signal KA1, KB1 Distribution coefficient θ1 Position data C45, C135, C225, C315 Intersect of sine wave signal

Claims (6)

In the interpolation processing method of the encoder for detecting the position by performing inverse trigonometric function conversion on the orthogonal AB phase sine wave signal A0 and sine wave signal B0, respectively,
Angle conversion means for separately inputting the sine wave signal A0 and the sine wave signal B0 and converting the sine wave signal to the angle signal A2 and the angle signal B2 by inverse trigonometric function conversion, respectively;
Inverting means for inputting the sine wave signal A0 and the sine wave signal B0 and inverting the sign and generating the inverted signal B1;
The sine wave signal A0, the sine wave signal B0, the inverted signal A1, and the inverted signal B1 are input, the respective intersections are detected, and a signal having a small absolute value of the signal is selected from the intersections to form a continuous line. Combined angle detection means for generating a combined angle signal AB0 for obtaining angle information from the value;
Distribution coefficient conversion means for inputting the combined angle signal AB0, calculating the distribution coefficient KA1 and the distribution coefficient KB1 for multiplying the angle signal A2 and the angle signal B2, and outputting them respectively;
A multiplier that receives the angle signal A2 and the distribution coefficient KA1, inputs the angle signal B2 and the distribution coefficient KB1, and outputs multiplication data A3 and multiplication data B3, respectively;
A synthesis means for inputting the multiplication data A3 and the multiplication data B3 and averaging them to generate position data θ1;
The encoder signal processing circuit according to claim 1, wherein the distribution coefficient converting means distributes all angle values obtained from the combined angle signal AB0 so that a sum of the distribution coefficient KA1 and the distribution coefficient KB1 is equal.   The distribution coefficient KA1 is a value that repeats maximum and minimum every π / 2 radians from the combined angle signal AB0, and the distribution coefficient KA1 and the distribution coefficient KB1 are the combined angle signal in the respective maximum and minimum regions. 2. The signal processing circuit for an encoder according to claim 1, wherein the signal processing circuit has a width that is at least twice the angle calculation resolution of AB0.   The encoder signal processing circuit according to claim 1, wherein the distribution coefficient KA <b> 1 can connect the angle between the maximum value and the minimum value with a straight line.   3. The signal processing circuit for an encoder according to claim 1, wherein the intermediate value of ½ of the distribution coefficient KA1 has a width that is at least twice as large as the angle calculation resolution of the combined angle signal AB0. .   5. The encoder signal processing circuit according to claim 4, wherein the distribution coefficient KA1 can be obtained by connecting the angles between the maximum value and the intermediate value and between the intermediate value and the minimum value with a straight line. 2. An upper / lower limit limit unit that receives the combined angle signal AB0 and outputs a combined angle signal AB1 in which the magnitude of the signal is limited by an upper limit value and a lower limit value to the distribution coefficient conversion unit. The signal processing circuit of the encoder according to any one of claims 1 to 5.

Images