CN110873582B - Encoder, processing device and processing method - Google Patents

Encoder, processing device and processing method Download PDF

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Publication number
CN110873582B
CN110873582B CN201910566251.9A CN201910566251A CN110873582B CN 110873582 B CN110873582 B CN 110873582B CN 201910566251 A CN201910566251 A CN 201910566251A CN 110873582 B CN110873582 B CN 110873582B
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signal
data length
interpolation
encoder
cycle signal
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CN110873582A (en
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松添雄二
中山智晴
松本宽之
久间裕丈
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Fuji Electric Co Ltd
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Fuji Electric Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24414—Encoders having selectable interpolation factors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24419—Interpolation not coverd by groups G01D5/24404, G01D5/24409 or G01D5/24414
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
    • G01D5/3473—Circular or rotary encoders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
    • G01D5/34776—Absolute encoders with analogue or digital scales
    • G01D5/34792—Absolute encoders with analogue or digital scales with only digital scales or both digital and incremental scales
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses

Abstract

Provided are an encoder, a processing apparatus, and a processing method, the encoder including: a signal output unit that outputs a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object; a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; a 2 nd conversion section converting the 2 nd periodic signal into a digital signal having a 2 nd data length; and an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit. The interpolation section calculates the interpolation value based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.

Description

Encoder, processing device and processing method
Technical Field
The present invention relates to an encoder (encoder) and the like.
Background
An encoder is known in the art which uses two periodic signals (pseudo sine waves) having a phase difference of 90 degrees output with rotation of a measurement object to calculate an interpolation value obtained by interpolating the periods of the two periodic signals, thereby measuring rotational positions which are electrically subdivided (see, for example, patent document 1).
[ Prior art documents ]
[ patent document ]
[ patent document 1] (Japanese patent application laid-open No. 2005-24281)
Disclosure of Invention
[ problem to be solved ]
However, the two periodic signals are subjected to interpolation processing after being converted into Digital signals by an AD (Analog-to-Digital) conversion circuit or the like. Therefore, there is a possibility that the Level (Level) of subdividing the period of two period signals, that is, the Resolution (Resolution) of the interpolation process is limited by the Resolution of the AD conversion circuit or the like.
In view of the above problems, it is an object of the present invention to provide an encoder and the like capable of improving the resolution of interpolation processing without depending on the resolution of an AD conversion circuit and the like.
[ solution ]
In order to achieve the above object, in one embodiment of the present invention, there is provided an encoder having:
a signal output unit that outputs a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object;
a 1 st converting section converting the 1 st periodic signal into a Digital (Digital) signal having a 1 st data length;
a 2 nd conversion section converting the 2 nd periodic signal into a digital signal having a 2 nd data length; and
an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit,
wherein the interpolation section calculates the interpolation value based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.
In another embodiment of the present invention, there is provided a processing apparatus relating to an encoder including: an output unit for outputting a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object; a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; and a 2 nd conversion section for converting the 2 nd periodic signal into a digital signal having a 2 nd data length,
the processing device has: an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit,
wherein the interpolation section calculates the interpolation value based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.
In another embodiment of the present invention, there is provided a processing method executed by a processing apparatus relating to an encoder including: a signal output unit for outputting a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object; a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; and a 2 nd conversion section for converting the 2 nd periodic signal into a digital signal having a 2 nd data length,
the processing method comprises the following steps: an interpolation step of calculating an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit,
wherein in the interpolation step, the interpolation value is calculated based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.
[ advantageous effects ]
According to the above-described embodiments, it is possible to provide an encoder or the like capable of improving the resolution of the interpolation process without depending on the resolution of an AD conversion circuit or the like.
Drawings
FIG. 1 is a schematic diagram of an example of an encoder according to an embodiment.
Fig. 2 is a block diagram showing an example of a configuration related to measurement processing of an encoder according to an embodiment.
[ description of symbols ]
100 encoder
110 wheel axle (Hub)
120 Scale Plate (Scale Plate)
140 base plate
150 optical module
152 light emitting element
154. 156 light-receiving element
170 signal processing circuit (signal output part)
172 upper processing circuit
174. 176 AD conversion circuit (1 st conversion unit, 2 nd conversion unit)
178 lower processing circuit (inner plug-in part, processing device)
180 signal processing circuit
190 Interface (Interface)
200 rotating shaft
200AX
Detailed Description
Hereinafter, specific embodiments for carrying out the present invention will be described with reference to the drawings.
[ constitution and Structure of encoder ]
First, the configuration, structure, and the like of the encoder 100 according to the present embodiment will be described with reference to fig. 1 and 2.
Fig. 1 is a schematic diagram of an example of an encoder 100 according to the present embodiment. Specifically, fig. 1 a is a plan view showing an example of the encoder 100 according to the present embodiment, and fig. 1B is a side sectional view (a-a sectional view of fig. 1 a) showing an example of the encoder 100 according to the present embodiment. Fig. 2 is a block diagram showing an example of a configuration related to the measurement process of the encoder 100 according to the present embodiment. Hereinafter, the structure of the encoder 100 will be described using a three-dimensional orthogonal (rectangular) coordinate system (XYZ coordinate system) shown in the drawings, and for convenience, a positive direction of the Z axis (hereinafter, referred to as "positive Z-axis direction") may be referred to as "up", and a negative direction of the Z axis (hereinafter, referred to as "negative Z-axis direction") may be referred to as "down". The positive and negative directions of the X axis, the positive and negative directions of the Y axis, and the positive and negative directions of the Z axis may be collectively referred to as "X axis direction", "Y axis direction", and "Z axis direction", respectively.
In fig. 1(a), the substrate 140 and the optical module 150 mounted on the substrate 140 are shown by one-dot chain lines so that the wheel shaft 110 and the scale plate 120 are exposed from above in the positive Z-axis direction and can be viewed. In fig. 1, a housing (Case) for housing the components of the encoder 100 is not shown.
The encoder 100 of the present embodiment includes a hub 110, a scale plate 120, and a base plate 140. The encoder 100 further includes an optical module 150, a signal processing circuit 170, an upper processing circuit 172, AD conversion circuits (ADC) 174 and 176, a lower processing circuit 178, a signal processing circuit 180, and an interface 190 as components related to the measurement process, and these components are mounted on the substrate 140.
The hub 110 is attached to One end of a rotating shaft 200 of a measurement target (for example, a rotary servo motor) such as a rotational position (rotational angle) during One Rotation (One Rotation) of the encoder 100.
For example, the hub 110 has a substantially cylindrical shape having an outer diameter larger than that of the rotation shaft 200 when viewed in a direction along the rotation shaft 200 (Z-axis direction), that is, in a plan view. A recessed portion is provided coaxially with the wheel shaft 110 and having an inner diameter substantially equal to (actually slightly larger than) the outer diameter of the rotary shaft 200 in a region near the axial center position of the end surface on the Z-axis negative direction side (i.e., the lower end surface) of the wheel shaft 110. The rotary shaft 200 is inserted into the recess so that the axial center of the hub 110 and the axial center 200AX of the rotary shaft 200 are aligned with each other. Further, a screw hole is provided at the axial center position of the hub 110 so as to penetrate between both end surfaces, and the male screw 115 is screwed to the rotary shaft 200 inserted into the recess of the lower end surface from the end surface on the positive Z-axis direction side of the hub 110 (i.e., the upper end surface), whereby the hub 110 can be attached to the rotary shaft 200. Thus, the wheel shaft 110 is rotated integrally with the rotation shaft 200 of the measurement object in accordance with the rotation thereof.
The male screw 115 has a flat top head. The male Screw 115 may be, for example, a Flat Screw (Flat screen). Accordingly, the vertex of the male screw 115 and the upper end surface (plane) of the wheel shaft 110 can be flush with each other, i.e., can be coplanar with each other.
The scale plate 120 can be attached to an end surface of the hub 110 opposite to the end surface on which the rotary shaft 200 is attached, that is, an upper end surface, by using, for example, Anaerobic Adhesive (Anaerobic Adhesive). The scale plate 120 is made of glass, for example. The scale plate 120 may be made of metal, Polycarbonate (Polycarbonate), or PET (Polyethylene Terephthalate) film. Specifically, the scale plate 120 has a circular plate shape, and the center thereof is arranged to coincide with the axial center 200AX of the rotation shaft 200 in a plan view. Further, on the surface (i.e., the upper surface) on the Z-axis positive direction side of the scale plate 120, an Incremental Pattern (Incremental Pattern)122 and an Absolute Pattern (Absolute Pattern)123 are also provided along the entire circumference at different radial positions near the outer periphery (outer edge) thereof.
The incremental pattern 122 may reflect the irradiation light from the optical module 150 by a predetermined pattern indicating a rotation angle (i.e., a relative angle) from an arbitrary angle position based on the rotation position of the scale plate 120. The incremental patterns 122 may be composed of, for example, 2 arranged at equal intervals in the circumferential direction along the entire circumferenceNThe reflection light source includes a plurality of reflection portions (N is an integer of 2 or more, for example, N is 9) that reflect incident light, and non-reflection portions (or low reflectance portions having a reflectance lower than that of the reflection portions) that are respectively disposed between the reflection portions. Accordingly, the addition of the pattern 122 can equally divide (equally separate) one rotation (360 degrees) of the rotation shaft 200 into 2NThe relative angle of the angular interval scales after a plurality (512 in the case of N being 9) is expressed. The light receiving element 154 is arranged to be opposed to the reflective portion and the non-reflective portion (orLow reflectance portion) to output a periodic signal (e.g., a sine wave signal). The reflective portion and the non-reflective portion or the low reflectance portion of the incremental pattern 122 may be formed by, for example, a known photolithography process. Hereinafter, the same applies to the reflective portion, the non-reflective portion, and the low reflectance portion of the absolute pattern 123.
The absolute pattern 123 may reflect the illumination light from the optical module 150 by a predetermined pattern indicating an absolute position of the rotation angle based on the rotation position of the scale plate 120. The absolute pattern 123 may be formed by arranging a plurality of (Plural) reflection parts of an M-sequence Code (Code) indicating N bits (Bit) in the circumferential direction based on the angular position of the scale 120, for example. Accordingly, the M-sequence code can be equally divided (equally divided) into 2 for one rotation (360 degrees) of the rotary shaft 200NAnd expressing the absolute angle of the subsequent angle interval scales. At this time, a non-reflective portion or a low reflectance portion may be disposed between reflective portions in the circumferential direction of the absolute pattern 123.
The base plate 140 has, for example, a disk shape and is disposed perpendicular to the axial center 200AX of the rotary shaft 200, that is, parallel to the scale plate 120, at a position spaced apart from the hub 110 (the scale plate 120, etc.) by a predetermined distance in the positive Z-axis direction, that is, in the upward direction. The base plate 140 is also arranged such that the axis of the disk shape coincides with the axis 200AX of the rotating shaft 200. Specifically, the substrate 140 is fixed to a housing, not shown, that houses the components of the encoder 100. That is, since the substrate 140 does not rotate together with the rotary shaft 200, various sensors (for example, the optical module 150) mounted on the substrate 140 can observe the rotation state of the scale plate 120 rotating together with the rotary shaft 200. The substrate 140 is a wiring board of FR-4 (Flame Retardant type 4) standard, for example. As described above, the substrate 140 can mount electronic components related to the measurement process, that is, the optical module 150, the signal processing circuit 170, the upper processing circuit 172, the ADCs 174 and 176, the lower processing circuit 178, the signal processing circuit 180, the interface 190, and the like. In addition, an electric component such as a power IC for driving the electronic component mounted on the substrate 140 may be mounted on the substrate 140.
The optical module 150 is provided at a radial position centered on the axial center 200AX of the rotary shaft 200 corresponding to the incremental pattern 122 and the absolute pattern 123 of the scale plate 120 in the lower surface that is the surface on the Z-axis negative direction side of the substrate 140. The optical module 150 includes a light emitting element 152 and light receiving elements 154 and 156.
The light emitting element 152 can irradiate light to the scale 120. The light Emitting element is, for example, a Lambert (Lambert) led (light Emitting diode).
The light receiving element 154 may receive the reflected light reflected by the reflection portion of the incremental pattern 122. The light receiving element 154 is, for example, a Photo Diode (PD) Array in which a plurality of PDs are arranged in a circumferential direction. The light receiving element 154 can output two sine wave signals corresponding to the repetition of the reflective portion and the non-reflective portion of the incremental pattern 122 as a current signal (photocurrent). In this case, the light receiving element 154 can correspond to 2 for one rotation periodNTwo sine wave signals of the number of cycles are output. The two sine wave signals have the same period and have a phase difference of 90 degrees. The two sine wave signals output from the light receiving element 154 may be input to the signal processing circuit 170.
The light receiving element 156 can receive the reflected light reflected by the reflection portion of the absolute pattern 123. The light receiving element 156 may be, for example, a PD array in which a plurality of photodiodes are arranged in the circumferential direction, like the light receiving element 154. The light receiving element 156 can output a current signal (photocurrent) corresponding to the M-sequence code, which is the arrangement of the reflective portion and the non-reflective portion of the absolute pattern 123. The current signal output from the light receiving element 156 may be input to the signal processing circuit 180.
The signal processing circuit 170 (an example of a signal output unit) can output two sine wave signals (an example of a 1 st cycle signal and a 2 nd cycle signal) having a phase difference of 90 degrees (an example of a predetermined phase difference) as Analog (Analog) voltage signals based on the rotation of the measurement object. For example, the signal processing circuit 170 includes a current-voltage conversion circuit for converting a current signal (sine wave signal) input from the light receiving element 154 into a voltage signal, an amplification circuit for amplifying the sine wave signal converted into the voltage signal, and the like. Two sine wave signals, which are voltage signals, output from the signal processing circuit 170 are input to the upper processing circuit 172. Further, two sine wave signals, which are voltage signals, output from the signal processing circuit 170 are also input to the ADCs 174 and 176, respectively.
The signal processing circuit 170 may output a voltage signal other than the sine wave signal as a periodic signal corresponding to the period of the increasing pattern 122, which is periodically repeated pattern information. As described later, the phase difference between the two periodic signals output from the signal processing circuit 170 may be an angle other than 90 degrees as long as an interpolation value can be calculated based on a division value between values of the two periodic signals (i.e., a quotient obtained by dividing the values of the two periodic signals).
The upper processing circuit 172 converts the two sine wave signals input from the light receiving element 154 into 2 values, that is, into rectangular pulse signals, counts (count) the rectangular pulses, and generates and outputs upper data of relative angles.
The ADC174 (an example of a 1 st conversion unit) converts a 1 st sine wave signal (hereinafter referred to as "s in θ signal" for convenience) of the two sine wave signals output from the light receiving element 154 into a digital signal. The ADC174 has a resolution of, for example, L1 bits (L1 is an integer of 2 or more, for example, L1 is 14), and can convert a digital signal having a data length of L1 bits (an example of the 1 st data length) and output the converted digital signal. The sin θ signal converted into a digital signal by the ADC174 is input to the lower processing circuit 178.
The ADC176 (an example of a 2 nd conversion unit) converts a 2 nd sine wave signal (hereinafter, referred to as "c os θ signal" for convenience) of the two sine wave signals output from the light receiving element 154 into a digital signal. The ADC176 has a resolution of, for example, L2 bits (L2 is an integer of 2 or more, for example, L2 is 14), and can convert a digital signal having a data length of L2 bits (an example of a 2 nd data length) and output the digital signal. The cos θ signal converted into the digital signal by the ADC176 is input to the lower-level processing circuit 178.
The resolutions L1 and L2 of the ADCs 174 and 176 may be the same or different.
The lower-level processing circuit 178 (an interpolation unit, an example of a processing device) may calculate an interpolation value of the phase angle θ obtained by interpolating the periods of the sin θ signal and the cos θ signal from the sin θ signal and the cos θ signal converted into digital signals by the ADCs 174 and 176. That is, the lower-level processing circuit 178 may calculate an interpolated value of the phase angle θ obtained by further dividing the repetition period of the reflection portion and the non-reflection portion (or the low reflectance portion) of the incremental pattern 122 corresponding to the period of the sin θ signal and the cos θ signal. Specifically, the lower-level processing circuit 178 may calculate an interpolated value of the phase angle θ, which is a value of the arctangent Function, based on a division calculation value between the sin θ signal and the cos θ signal converted into the digital signals by the ADCs 174 and 176, for example, a division calculation value (i.e., quotient) obtained by dividing the value of the sin θ signal by the value of the cos θ signal, that is, a value of the Tangent Function (changefunction), and output lower-level data of the relative angle. Here, the interpolation process of the lower processing circuit 178 will be described in detail later.
The signal processing circuit 180 can generate and output data of the M-serial code from the current signal (photocurrent) corresponding to the M-serial code of the absolute pattern 123 input from the light receiving element 156.
The interface 190 can output the processing results of the upper processing circuit 172, the lower processing circuit 178, and the signal processing circuit 180 to an external device (e.g., a Servo Amplifier (Servo Amplifier) that controls a Servo motor that is a measurement target such as the rotational position of the encoder 100). The interface 190 is, for example, a female connector terminal, and is connected to a male connector terminal connected to the tip of a Cable (Cable) extended (extended) from an external device, so that a processing result (measurement result) can be output to the external device. Accordingly, for example, the servo amplifier or the like can grasp the rotational position (absolute position) of the control target in one rotation period based on the measurement result of the encoder 100, and control the servo motor.
[ interpolation processing ]
Next, the interpolation process of the lower processing circuit 178 will be described in detail.
First, the lower processing circuit 178 calculates a value of a tangent function (tan θ), which is a division calculation value (i.e., a quotient) obtained by dividing a value of the sin θ signal subjected to a predetermined Normalization process (e.g., a process of subtracting DC (Direct Current)) by a value of the cos θ signal. At this time, the lower processing circuit 178 calculates a division calculation value of the data length of the sin θ signal and the cos θ signal, that is, the data length of L1 bits and L2 bits (specifically, the longer of the data lengths of L1 bits and L2 bits), and the data length of L3 bits (for example, L3 is 17) which is longer (an example of the 3 rd data length). The reason for this is that even if the values of the sin θ signal and the cos θ signal are relatively short data lengths, the calculation result of the data length exceeding the values of the sin θ signal and the cos θ signal can be obtained by the division calculation.
Next, the lower processing circuit 178 equally divides (equally divides) the periods of the sin θ signal and the cos θ signal into a predetermined number corresponding to the data length of L3 bits, that is, 2L3Then, an interpolation value (phase angle θ) corresponding to a division calculation value of the calculation result is selected from the set phase angle candidate values (an example of interpolation candidate values).
For example, the expression 2 may be prepared (specified) in advanceL3The lower processing circuit 178 selects an interpolation value corresponding to the calculated division calculation value by looking up Table Data (Table Data) of the correspondence relationship between the interpolation value of each pixel (i.e., the phase value as the value of the arctangent function) and the division calculation value (i.e., the value of the tangent function). This processing can be realized by, for example, a known Table Lookup circuit (hard Lookup Table) including a Multiplexer (Multiplexer) or the like. Further, the processing may be realized by a microcomputer (microcomputer) having a nonvolatile internal Memory (Memory) in which the above table data is stored.
In this way, the lower-level processing circuit 178 can realize the interpolation processing of the relatively high resolution by calculating the interpolation values obtained by subdividing one cycle of the added pattern 122 by the relatively high resolution using the ADCs 174 and 176 of the relatively low resolution. That is, the lower-level processing circuit 178 does not depend on the resolution of the AD conversion circuit or the like, and can improve the resolution of the interpolation processing.
The lower processing circuit 178 may use a division value (i.e., a quotient) obtained by dividing the value of the co s θ signal by the value of the sin θ signal in the interpolation processing, or may switch the divisor and the dividend according to the magnitude of the values of the sin θ signal and the cos θ signal, the positive-negative relationship, or the like. In this case, the contents of the prepared table data may be changed as appropriate in accordance with the changes of the divisor and dividend.
[ deformation/Change ]
The embodiments for carrying out the present invention have been described in detail, but the present invention is not limited to the specific embodiments described above, and various modifications and/or changes can be made within the scope of the gist of the present invention described in the claims.
For example, in the above embodiment, the encoder 100 is an Absolute (Absolute) type encoder, but may be an Incremental (Incremental) type encoder. In this case, the absolute pattern 123 of the scale plate 120, the light receiving element 156 of the optical module 150 corresponding to the absolute pattern 123, the signal processing circuit 170 for generating an M-series code corresponding to the absolute pattern 123, and the like may be omitted.
In the above-described embodiment and modification, the encoder 100 is a reflection-type encoder, but may be a transmission-type encoder. In this case, the incremental pattern 122 and/or the absolute pattern 123 of the scale plate 120 may be configured by a transmissive portion that can transmit the irradiation light and a non-transmissive portion that cannot transmit the irradiation light, instead of the reflective portion and the non-reflective portion or the low reflectance portion. In addition, in addition to the optical module 150, a light emitting element that irradiates light to the scale plate 120 may be provided on the side opposite to the optical module 150 (light receiving element) when viewed from the scale plate 120, that is, at a position spaced apart from the scale plate 120 by a predetermined distance in the Z-axis negative direction (i.e., downward).
In the above-described embodiment and modification, the functions of the upper processing circuit 172, the lower processing circuit 178, and the signal processing circuit 180 may be transferred to an external device (an interposer, an example of a processing device) that is external to the encoder 100, that is, that can be connected to the encoder 100 via the interface 190.
The interpolation processing methods according to the above-described embodiments and modifications can be applied to interpolation processing other than the encoder 100.
In view of the above, there is provided an encoder having: a signal output unit that outputs a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object; a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; a 2 nd conversion section converting the 2 nd periodic signal into a digital signal having a 2 nd data length; and an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit. The interpolation section calculates the interpolation value based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.
The interpolation unit divides the cycle of the 1 st cycle signal and the 2 nd cycle signal into a predetermined number corresponding to the 3 rd data length, and selects the interpolation value corresponding to the division calculation value from the set interpolation candidate values.
In addition, there is provided a processing apparatus associated with an encoder having: a signal output unit for outputting a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object; a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; and a 2 nd conversion unit for converting the 2 nd periodic signal into a digital signal having a 2 nd data length. The processing device includes an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit. The interpolation section calculates the interpolation value based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.
Furthermore, there is provided a processing method performed by a processing apparatus associated with an encoder having: a signal output unit for outputting a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object; a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; and a 2 nd conversion unit for converting the 2 nd periodic signal into a digital signal having a 2 nd data length. The processing method includes an interpolation step of calculating an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion section and the 2 nd conversion section. In the interpolation step, the interpolation value is calculated based on the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length.
Although the embodiments of the present invention have been described above, the above description is not intended to limit the contents of the present invention.

Claims (3)

1. An encoder, having:
a signal output unit that outputs a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object;
a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length;
a 2 nd conversion section converting the 2 nd periodic signal into a digital signal having a 2 nd data length; and
an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit,
wherein the interpolation section calculates the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length, and selects the interpolation value corresponding to the division calculation value having the 3 rd data length from among the interpolation candidate values, according to a correspondence between interpolation candidate values obtained by dividing the periods of the 1 st cycle signal and the 2 nd cycle signal by a predetermined number corresponding to the 3 rd data length and division calculation values.
2. A processing device associated with an encoder, wherein,
the encoder has:
a signal output unit that outputs a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object;
a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; and
a 2 nd conversion section converting the 2 nd periodic signal into a digital signal having a 2 nd data length,
the processing device has:
an interpolation unit that calculates an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit,
the interpolation section calculates the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length, and selects the interpolation value corresponding to the division calculation value having the 3 rd data length from among the interpolation candidate values, according to a correspondence between interpolation candidate values obtained by dividing the periods of the 1 st cycle signal and the 2 nd cycle signal by a predetermined number corresponding to the 3 rd data length and division calculation values.
3. A processing method performed by a processing device associated with an encoder, wherein,
the encoder has:
a signal output unit that outputs a 1 st periodic signal and a 2 nd periodic signal having a predetermined phase difference in accordance with rotation of a measurement object;
a 1 st conversion section converting the 1 st periodic signal into a digital signal having a 1 st data length; and
a 2 nd conversion section converting the 2 nd periodic signal into a digital signal having a 2 nd data length,
the processing method comprises the following steps:
an interpolation step of calculating an interpolation value obtained by interpolating a period of the 1 st cycle signal and the 2 nd cycle signal based on a division calculation value between values of the 1 st cycle signal and the 2 nd cycle signal converted into digital signals by the 1 st conversion unit and the 2 nd conversion unit,
in the interpolation step, the division calculation value having a 3 rd data length longer than the 1 st data length and the 2 nd data length is calculated, and the interpolation value corresponding to the division calculation value having the 3 rd data length is selected from the interpolation candidate values, based on a correspondence between interpolation candidate values obtained by dividing the periods of the 1 st cycle signal and the 2 nd cycle signal by a predetermined number corresponding to the 3 rd data length and division calculation values.
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