JP2019132730A - Encoder and control method for encoder - Google Patents

Abstract

To provide an encoder with which it is possible to reliably discriminate between a signal fluctuation due to an error factor that the encoder has and a signal fluctuation due to the sticking of a contaminant to a scale and detect the abnormality of the scale.SOLUTION: An encoder 1 comprises: a scale 2; detection means 4 relatively moving along the scale 2 and equipped with a plurality of detection elements 400; calculation means 5 for calculating the amount of relative movement of the scale 2 and the detection means 4 on the basis of a signal. When a prescribed detection element 400 is assumed to be a first detection unit 41 and the other detection element 400 different from the first detection unit 41 is assumed to be a second detection unit 42, the detection means 5 includes a measurement signal calculation unit 52 for calculating a measurement signal using a signal form each of the detection units 41, 42, an extraction unit 53 for extracting an abnormality determination signal for determining the abnormality of the scale 2 from the measurement signal, and an abnormality determination unit 54 for determining from the abnormality determination signal whether or not the scale has abnormality.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an encoder and an encoder control method.

Conventionally, a scale having a graduation along the measurement direction, a detection unit that relatively moves along the scale and detects a signal through the scale, and a calculation unit that calculates a relative movement amount between the scale and the detection unit based on the signal Are known.
When such an encoder is used, contaminants such as dust and metal powder in the usage environment may adhere to the scale. Contaminants adhering to the scale may degrade the signal detected by the detection means and reduce the measurement accuracy. For this reason, the user must periodically stop measuring instruments and machine tools equipped with encoders and check for the presence or absence of contaminants attached to the scale. The presence or absence of contaminants attached to the scale cannot be grasped until the user confirms it, and there is a problem that it takes time and effort for confirmation.

  On the other hand, for example, a photoelectric encoder (encoder) described in Patent Document 1 includes a main scale (scale), an index scale disposed so as to be relatively displaceable with respect to the main scale, and an index scale with respect to the main scale. Outputs a plurality of periodic signals having different phases according to the relative displacement amount of the light, and outputs a plurality of periodic signals having the same phase among the plurality of periodic signals, and a plurality of signal stability determinations. Means and a signal synthesis circuit.

The plurality of signal stability determination means input only the periodic signals output from the plurality of light receiving elements, and output only the periodic signals determined to have no abnormality. The signal synthesis circuit synthesizes the periodic signals output from the plurality of signal stability determination means to generate one periodic signal. The photoelectric encoder uses only a periodic signal determined by a plurality of signal stability determination means that no contaminant is attached to the main scale (no abnormality), and a relative displacement amount (one Periodic signal).
Therefore, since the photoelectric encoder obtains the relative movement amount from the periodic signal having no abnormality, it is possible to suppress a decrease in measurement accuracy. In addition, since the user only has to check the main scale when it is determined that there is an abnormality by a plurality of signal stability determination means, it is possible to reduce the labor for confirmation.

JP 2003-65803 A

However, in the photoelectric encoder described in Patent Document 1, the plurality of signal stability determination means determine the presence or absence of abnormality from light shielding by a contaminant.
Here, the encoder has a scale waviness caused by the material of the scale and the manufacturing process, misalignment between the scale and the detecting means, signal increase or signal decrease (signal fluctuation) due to light source deterioration, unevenness of reflectance of the scale, etc. It has the error factor. Signal fluctuations such as signal increase and signal reduction due to error factors are substantially the same signal fluctuations as signal fluctuations due to contaminants smaller than a predetermined size attached to the scale. In addition, the encoder is provided with correction means for canceling out this error factor in advance.

  For this reason, when the contaminant attached to the scale is smaller than the predetermined size, it is not possible to distinguish between the signal fluctuation due to the error factor and the signal fluctuation due to the contaminant being attached. The signal fluctuation may be corrected as a signal fluctuation due to an error factor. Therefore, there is a problem that the encoder may not be able to detect an abnormality caused by a contaminant attached to the scale.

  An object of the present invention is to provide an encoder capable of reliably distinguishing between a signal variation due to an error factor of the encoder and a signal variation due to contaminants adhering to the scale and detecting an abnormality of the scale.

  The encoder of the present invention includes a scale having a scale arranged in parallel along the measurement direction, and a plurality of detection elements that are relatively moved along the scale and that are arranged in parallel along the measurement direction. An encoder comprising: a detecting means for detecting; and a calculating means for calculating a relative movement amount between the scale and the detecting means based on the signal, wherein the detecting means includes a plurality of detecting elements and is arranged in parallel along the measuring direction. The plurality of detection groups include a plurality of detection units arranged in parallel along the measurement direction, and the plurality of detection units have a predetermined detection element as a first detection unit, When another detection element different from the detection unit is used as the second detection unit, the calculation means includes a signal detection unit that detects a signal from each of the first detection unit and the second detection unit, and a signal detection unit. Calculate the measurement signal using the detected signal A measurement signal calculation unit, an extraction unit for extracting an abnormality determination signal for determining abnormality of the scale from the measurement signal calculated by the measurement signal calculation unit, and an abnormality for determining whether the scale is abnormal from the abnormality determination signal And a determination unit.

Here, when there is no error factor in the encoder and no contaminants adhere to the scale, the abnormality determination signal is detected as a uniform signal. In addition, when the encoder has an error factor, the abnormality determination signal is detected in a state in which a fluctuation component due to signal fluctuation is steadily included. On the other hand, when a contaminant adheres to the scale, the abnormality determination signal is detected in a state where the fluctuation component is temporarily included.
For this reason, the abnormality determination unit determines whether the fluctuation component is stationary (encoder error factor) or temporary (contamination of contaminants on the scale) in the abnormality determination signal, and the fluctuation component is temporary. If there is, it is determined that there is an abnormality in the scale.
In addition, the plurality of detection units specify positions and numbers of detection elements that detect signals used for calculation of the abnormality determination signal among the plurality of detection elements arranged in parallel along the measurement direction.

Therefore, according to the present invention, the signal detection unit can detect at least two-phase signals from the first detection unit and the second detection unit. Then, based on the signals from the first detection unit and the second detection unit detected by the signal detection unit, the measurement signal calculation unit calculates the measurement signal. The extraction unit extracts an abnormality determination signal for determining abnormality of the scale from the measurement signal, and the abnormality determination unit determines whether or not the scale is abnormal from the abnormality determination signal, that is, whether the fluctuation component is steady or temporary. If the fluctuation component is temporary, it is determined that there is an abnormality in the scale.
Therefore, the encoder can reliably discriminate between the signal fluctuation due to the error factor of the encoder and the signal fluctuation due to the contaminant adhering to the scale, and detect the abnormality of the scale.

  At this time, the plurality of detection elements are arranged in parallel corresponding to the scale, and the plurality of detection groups include the first detection unit, the second detection unit, the third detection unit, and the fourth detection unit as the plurality of detection units. The first detection unit is a plurality of detection elements, the second detection unit is a plurality of other detection elements different from the first detection unit, and is 180 degrees out of phase with the first detection unit. A plurality of detection elements arranged, the third detection unit is a plurality of other detection elements different from the second detection unit, and the fourth detection unit is a plurality of other detection elements different from the third detection unit. In addition, when the third detection unit is a plurality of detection elements arranged at positions 180 degrees out of phase, the signal detection unit includes the first detection unit, the second detection unit, the third detection unit, and the fourth detection unit. A signal is detected from each of the detection units, and the measurement signal calculation unit is configured to output a signal from the first detection unit and a signal from the second detection unit. The first measurement signal is calculated based on the signal, the second measurement signal is calculated based on the signal from the third detection unit and the signal from the fourth detection unit, and the extraction unit includes the first measurement signal and the second measurement signal. It is preferable that the abnormality determination signal is extracted from the abnormality determination unit and the abnormality determination unit determines whether there is an abnormality in the scale from the abnormality determination signal.

  Here, the signal detected from the first detector is an A-phase signal, detected from the second detector, and a signal that is 180 degrees out of phase with the A-phase signal is an a-phase signal and detected from the third detector. This signal is a B-phase signal, and a signal that is detected by the fourth detector and is 180 degrees out of phase with the B-phase signal is a b-phase signal.

  According to such a configuration, the signal detection unit is based on signals detected from the plurality of detection units, and the measurement signal calculation unit is configured to output the signal from the first detection unit (A phase signal) and the second detection unit. The first measurement signal is calculated based on the signal (a phase signal), and the second measurement signal is calculated based on the signal (B phase signal) from the third detection unit and the signal (b phase signal) from the fourth detection unit. Is calculated. The extraction unit extracts an abnormality determination signal from the first measurement signal and the second measurement signal, and the abnormality determination unit can determine whether there is an abnormality in the scale from the abnormality determination signal. At this time, the abnormality determination signal extracted from the measurement signal calculated based on the two signals is an abnormality determination signal with higher sensitivity than the abnormality determination signal based on the two-phase signal. Therefore, the encoder uses a highly sensitive abnormality determination signal to more reliably distinguish between signal fluctuations due to error factors of the encoder and signal fluctuations due to contaminants adhering to the scale, and detect abnormalities in the scale. can do.

  At this time, the measurement signal calculation unit calculates the first measurement signal by performing a differential operation on the signal from the first detection unit and the signal from the second detection unit, and the signal from the third detection unit and the fourth detection. It is preferable to calculate the second measurement signal by performing a differential operation on the signal from the unit.

  According to such a configuration, the measurement signal calculation unit calculates the first measurement signal by performing a differential operation on the signal from the first detection unit and the signal from the second detection unit, and the signal from the third detection unit. The second measurement signal can be calculated by performing a differential operation on the signal from the fourth detection unit. At this time, the abnormality determination signal extracted from the measurement signal calculated by the differential calculation is an abnormality determination signal having higher sensitivity than the abnormality determination signal extracted from the measurement signal calculated without using the differential calculation. . Therefore, the encoder uses a highly sensitive abnormality determination signal to more reliably distinguish between signal fluctuations due to error factors of the encoder and signal fluctuations due to contaminants adhering to the scale, and detect abnormalities in the scale. can do.

  In this case, the plurality of detection elements are arranged side by side corresponding to the scale, and the plurality of detection groups include a first detection unit, a second detection unit, and a third detection unit as the plurality of detection units, and the first detection unit The unit is a plurality of detection elements, the second detection unit is a plurality of other detection elements different from the first detection unit, and a plurality of the detection units are arranged at positions 120 degrees out of phase with the first detection unit. The third detection unit is a plurality of other detection elements different from the first detection unit and the second detection unit, and a plurality of the third detection units are arranged at positions that are 120 degrees out of phase with the second detection unit. When the detection element is used, the signal detection unit detects signals from each of the first detection unit, the second detection unit, and the third detection unit, and the measurement signal calculation unit includes the signal from the first detection unit, The first measurement signal and the second measurement signal are calculated based on the signal from the second detection unit and the signal from the third detection unit. And, the extraction unit extracts the abnormality determination signal from the first measurement signal and the second measurement signal, the abnormality determination unit preferably determines whether or not there is an abnormality in the scale from the abnormality determination signal.

  According to such a configuration, the signal detection unit can detect a three-phase signal. Then, the measurement signal calculation unit calculates the first measurement signal and the second measurement signal from the three-phase signal. At this time, the abnormality determination signal extracted from the measurement signal calculated based on the three-phase signal is a higher sensitivity abnormality determination signal than the abnormality determination signal based on the two-phase signal. Therefore, the encoder uses a highly sensitive abnormality determination signal to more reliably distinguish between signal fluctuations due to error factors of the encoder and signal fluctuations due to contaminants adhering to the scale, and detect abnormalities in the scale. can do.

  In this case, the third detection unit is a plurality of other detection elements different from the first detection unit and the second detection unit, and a plurality of detections arranged at positions 90 degrees out of phase with the first detection unit. The fourth detection unit is a plurality of other detection elements different from the first detection unit, the second detection unit, and the third detection unit, and is arranged at a position that is 90 degrees out of phase with the second detection unit. In addition, it is preferable that the third detection unit be a plurality of detection elements arranged at positions 180 degrees out of phase.

According to such a configuration, the first detection unit to the fourth detection unit are arranged at positions that are each 90 degrees out of phase. And the signal detection part can detect a 4-phase signal. At this time, the abnormality determination signal calculated by the differential operation based on the four-phase signal is an abnormality determination signal having higher sensitivity than the abnormality determination signal based on the two-phase signal. Therefore, the encoder uses a highly sensitive abnormality determination signal to more reliably distinguish between signal fluctuations due to error factors of the encoder and signal fluctuations due to contaminants adhering to the scale, and detect abnormalities in the scale. can do.
In addition, since the encoder can change, for example, a plurality of detection elements provided continuously along the measurement direction from the first detection unit to the fourth detection unit, a signal necessary for calculating the abnormality determination signal is obtained. About the detection means to do, it can design easily.

  At this time, it is preferable that the first detection unit and the second detection unit have the same number of detection elements, and the third detection unit and the fourth detection unit have the same number of detection elements.

  According to such a configuration, the signal detection unit can detect signals of the same intensity from the first detection unit and the second detection unit, and detect signals of the same intensity from the third detection unit and the fourth detection unit. can do. That is, when the A-phase signal and the a-phase signal, and the B-phase signal and the b-phase signal are differentially calculated, signals having the same intensity can be differentially calculated. Therefore, the encoder can use the abnormality determination signal with higher sensitivity than when the first detection unit and the second detection unit, and the third detection unit and the fourth detection unit have different numbers of detection elements. Therefore, it is possible to more reliably discriminate between the signal fluctuation due to the error factor of the encoder and the signal fluctuation due to the contaminant adhering to the scale, and to detect the abnormality of the scale.

  In this case, it is preferable that the plurality of detection units be the same number of detection elements.

According to such a configuration, each of the plurality of detection units has the same number of detection elements, so that the signal detection unit can detect signals having the same intensity from the respective detection units. That is, the measurement signal calculation unit performs, for example, a differential operation on these signals, so that the first signal with less noise than the signals detected when the number of detection elements of the plurality of detection units is different from each other. A measurement signal and a second measurement signal can be calculated.
Therefore, the encoder can detect the abnormality of the scale with higher sensitivity by reliably distinguishing between the signal fluctuation due to the error factor of the encoder and the signal fluctuation due to the contaminant adhering to the scale.

In addition, for example, when the first measurement signal and the second measurement signal are calculated based on a three-phase signal, the measurement signal calculation unit compares the signals detected when the number of detection elements of the plurality of detection units is different from each other. The first measurement signal and the second measurement signal with less noise can be calculated.
Therefore, the encoder can detect the abnormality of the scale with higher sensitivity by reliably distinguishing between the signal fluctuation due to the error factor of the encoder and the signal fluctuation due to the contaminant adhering to the scale.
In addition, the detection means can be easily designed by using the same number of detection elements for each of the plurality of detection units.

  In this case, the plurality of detection groups preferably have different total numbers of the plurality of detection elements.

  Here, when a contaminant having the same size as a certain detection group (the same length as the length along the measurement direction of the certain detection group) adheres to the scale, the same applies from each of the plurality of detection units in the certain detection group. Since the signal is detected, no fluctuation component is generated in the abnormality determination signal extracted by the extraction unit. For this reason, there is a problem that the encoder may not be able to detect the presence or absence of contamination (scale abnormality).

  However, according to the present invention, the plurality of detection groups have different total numbers of the plurality of detection elements, so that even if contaminants having a size that cannot be detected by a certain detection group adhere to the scale. The contaminants can be detected by other detection groups. That is, since the total number of the plurality of detection elements is different in each detection group, and the area in which the contaminant can be detected is also different in each detection group, the encoder can cope with contaminants of various sizes. it can. Therefore, the encoder can improve the determination of whether or not the contaminant has adhered to the scale and the detection sensitivity of the contaminant.

  At this time, the plurality of detection groups have different detection group lengths L and include 1 when the reference of the length of each detection group along the measurement direction is L. It is preferable that they are arranged in combinations of detection group lengths L that do not have common divisors and do not become a common multiple greater than the length of the detection means along the measurement direction.

  Here, for example, when the reference of the length of each detection group along the measurement direction is L, the length of the contaminant along the measurement direction is 4L of the detection group. When the lengths are the same, the detection group having a length of 2L and the detection group having a length of 4L cannot detect the contaminants, and there is a problem that the detection sensitivity may be lost.

  However, according to the present invention as described above, when the plurality of detection groups has a reference length of each detection group along the measurement direction as L, the lengths of the detection groups in the plurality of detection groups are: The length of the pollutant is different by being arranged in combination with the detection group length L which is different from each other and does not have a common divisor including 1 and does not become a common multiple of the length of the detection means along the measurement direction. As a result, it is possible to suppress the occurrence of missing detection sensitivity.

  In this case, the encoder of the present invention is preferably an optical encoder that includes a light source that irradiates light to the scale, and detection means that receives light through the scale and detects a signal.

  According to such a configuration, the optical encoder can easily mount the encoder of the present invention.

  The encoder control method according to the present invention includes a scale having a scale arranged in parallel along the measurement direction, and a plurality of detections that are relatively moved along the scale and signals that pass through the scale are arranged in parallel along the measurement direction. An encoder control method comprising: a detecting means for detecting by an element; and a calculating means for calculating a relative movement amount between the scale and the detecting means based on a signal. The detecting means includes a plurality of detecting elements and performs measurement. A plurality of detection groups arranged in parallel along the direction, the plurality of detection groups include a plurality of detection units arranged in parallel along the measurement direction, and the plurality of detection units include a predetermined detection element as a first When the detection unit is a detection unit different from the first detection unit and the second detection unit is used as the second detection unit, the calculation means detects a signal from each of the first detection unit and the second detection unit; The signal detected by the signal detector A measurement signal calculation step for calculating a measurement signal using the measurement signal, an extraction step for extracting an abnormality determination signal for determining abnormality of the scale from the measurement signal calculated by the measurement signal calculation unit, and whether there is an abnormality in the scale from the abnormality determination signal An abnormality determination step of determining whether or not.

According to the present invention, the encoder control method calculates the measurement signal in the measurement signal calculation step based on the signals from the first detection unit and the second detection unit detected in the signal detection step. Then, the extraction step extracts an abnormality determination signal for determining an abnormality of the scale from the measurement signal, and the abnormality determination step determines whether or not there is an abnormality in the scale from the abnormality determination signal, that is, the fluctuation component is steady or temporary. If the fluctuation component is temporary, it is determined that there is an abnormality in the scale.
Therefore, the encoder control method can reliably distinguish between a signal variation due to an error factor of the encoder and a signal variation due to contaminants adhering to the scale, thereby detecting an abnormality in the scale.

The perspective view which shows the encoder which concerns on 1st Embodiment. The figure which shows the detection means in the encoder Block diagram showing calculation means in the encoder Flowchart showing an abnormality detection method in the encoder The figure which shows the signal calculated by the calculation means in the encoder The figure which shows the detection means in the encoder which concerns on 2nd Embodiment. Block diagram showing calculation means in the encoder The figure which shows the detection means in the encoder which concerns on 3rd Embodiment. The figure which shows the signal detected by the detection means in the said encoder

[First Embodiment]
A first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a perspective view showing an encoder according to the first embodiment.
As shown in FIG. 1, the encoder 1 has a long scale 2, a light source 3 that irradiates light to the scale 2, a relative movement along the scale 2, and light received through the scale 2 to receive a signal. It is an optical encoder provided with the detection means 4 to detect.

The scale 2 has a plurality of diffraction gratings 21 that are scales arranged in parallel along the measurement direction. The scale 2 is made of translucent glass. Note that the scale 2 is not limited to glass, and may be formed of any translucent member.
The light source 3 irradiates parallel light toward one surface of the scale 2. The light source 3 is, for example, an LED (Light Emitting Diode). The light source 3 is not limited to an LED, and may be an arbitrary light source.

The parallel light irradiated to the scale 2 by the light source 3 is diffracted into a plurality of diffracted lights (not shown) by the plurality of diffraction gratings 21. The plurality of diffracted lights interfere to generate interference fringes that repeat light and dark at a period corresponding to the arrangement pitch of the plurality of diffraction gratings 21 along the measurement direction. In the following description, “phase” means the phase of the period of interference fringes generated by the plurality of diffraction gratings 21 unless otherwise specified.
Moreover, in the following description, it is a longitudinal direction of the scale 2 and the measurement direction may be described as the X direction.

The detection means 4 includes a plurality of detection elements 400 arranged in parallel along the measurement direction (X direction). The plurality of detection elements 400 are arranged in parallel at the arrangement pitch P along the X direction corresponding to the arrangement pitch of the plurality of diffraction gratings 21 on the scale 2. PDAs (Photo Diode Array) are used for the plurality of detection elements 400. The PDA is a detector having a property capable of measuring a plurality of interference fringes at a time. The plurality of detection elements 400 are not limited to PDAs, and any detector such as a PSD (Position Sensitive Detector) or a CCD (Charge-Coupled Device) may be used.
The light source 3 and the detection means 4 are installed facing each other so as to overlap each other with the scale 2 interposed therebetween. The detection unit 4 receives light from the light source 3 via the plurality of diffraction gratings 21 of the scale 2 and detects signals from interference fringes generated on the detection unit 4 (a plurality of detection elements 400) by the light.

FIG. 2 is a diagram showing detection means in the encoder.
As shown in FIG. 2, the detection means 4 includes a plurality of detection groups 40 including a plurality of detection elements 400 and arranged in parallel along the X direction. The detection unit 4 periodically arranges a plurality of detection groups 40 along the X direction.
The plurality of detection groups 40 include a plurality of detection units 41 to 44 arranged in parallel along the X direction. The plurality of detection groups 40 include a first detection unit 41, a second detection unit 42, a third detection unit 43, and a fourth detection unit 44 as the plurality of detection units 41 to 44.

  The first detection unit 41 includes a plurality of detection elements 400, the second detection unit 42 includes a plurality of other detection elements 400 different from the first detection unit 41, and has a 180-degree phase with respect to the first detection unit 41. A plurality of detection elements 400 are arranged at shifted positions. The third detection unit 43 is a plurality of other detection elements 400 different from the first detection unit 41 and the second detection unit 42, and is arranged at a position 90 degrees out of phase with the first detection unit 41. The fourth detection unit 44 includes a plurality of detection elements 400 different from the first detection unit 41, the second detection unit 42, and the third detection unit 43, and the second detection unit 42. Is a plurality of detection elements 400 that are arranged at positions that are 90 degrees out of phase and that are arranged at positions that are 180 degrees out of phase with the third detector 43.

The plurality of detection units 41 to 44 are the same number of detection elements 400, and in the present embodiment, the plurality of detection units 41 to 44 are each four detection elements 400.
The plurality of detection units 41 to 44 are arranged in the detection group 40 of the detection unit 4 so as to be shifted by ¼ along the X direction. As a result, a signal whose phase is shifted by ¼ period is detected from the plurality of detection units 41 to 44. The first detection unit 41 detects an A phase signal, the second detection unit 42 detects an a phase signal that is 180 degrees out of phase with the A phase signal, and the third detection unit 43 detects an A phase signal. A B phase signal that is 90 degrees out of phase with the signal is detected, and a b phase signal that is 180 degrees out of phase with the B phase signal is detected from the fourth detector 44.

  In the detection means 4, the reference of the length along the X direction of the plurality of detection groups 40 is L, and the arrangement pitch of the plurality of detection elements 400 is P. At this time, the arrangement pitch P of the plurality of detection elements 400 is preferably designed to be 4 μm, and the length L of the detection group 40 is preferably designed to be 200 μm.

FIG. 3 is a block diagram showing calculation means in the encoder.
As shown in FIG. 3, the encoder 1 further includes a calculation unit 5 that calculates a relative movement amount between the scale 2 and the detection unit 4 based on the signal, and an abnormality notification unit 6. The calculation means 5 includes a signal detection unit 51, a measurement signal calculation unit 52, an extraction unit 53, and an abnormality determination unit 54.

  The signal detection unit 51 detects signals from the first detection unit 41, the second detection unit 42, the third detection unit 43, and the fourth detection unit 44. Specifically, the signal detection unit 51 detects the A phase signal from the first detection unit 41, detects the a phase signal from the second detection unit 42, detects the B phase signal from the third detection unit 43, The b-phase signal is detected from the fourth detection unit 44.

The measurement signal calculation unit 52 calculates a first measurement signal by performing a differential operation on the signal from the first detection unit 41 and the signal from the second detection unit 42, and the signal from the third detection unit 43 and the fourth signal. The signal from the detection unit 44 is differentially calculated to calculate the second measurement signal.
Specifically, the measurement signal calculation unit 52 calculates a first measurement signal for calculating a relative movement amount by performing a differential operation on the A-phase signal and the a-phase signal. In addition, the measurement signal calculation unit 52 calculates a second measurement signal for calculating a relative movement amount by performing a differential operation on the B-phase signal and the b-phase signal.

  The extraction unit 53 extracts an abnormality determination signal from the first measurement signal and the second measurement signal. Specifically, the extraction unit 53 extracts an abnormality determination signal by using a low-pass filter for the first measurement signal and the second measurement signal. The abnormality determination signal has a longer period than the first measurement signal and the second measurement signal.

The abnormality determination unit 54 determines whether there is an abnormality in the scale 2 from the abnormality determination signal. Here, the abnormality in the scale 2 is that contaminants adhere to the scale 2. That is, the abnormality determination unit 54 determines whether or not a contaminant is attached to the scale 2.
When the abnormality determination unit 54 determines that there is an abnormality in the scale 2, the abnormality notification unit 6 notifies the user of the abnormality in the scale 2. The abnormality notification unit 6 is, for example, a buzzer. The abnormality notifying unit is not limited to a buzzer, and any abnormality may be used as long as it can notify the user of an abnormality such as displaying a warning on a display or blinking an indicator lamp (LED). .

FIG. 4 is a flowchart showing an abnormality detection method in the encoder, and FIG. 5 is a diagram showing signals calculated by calculation means in the encoder. Specifically, FIG. 5 (A) is a diagram showing the detection means 4, and FIG. 5 (B) is each signal detected from the first detector 41 to the fourth detector 44, and FIG. (C) is a 1st measurement signal and a 2nd measurement signal, FIG.5 (D) is an abnormality determination signal.
Hereinafter, the control method of the encoder 1 and the abnormality detection method in the scale 2 will be described with reference to FIGS.

  As shown in FIG. 4, the encoder 1 first includes a first detection unit 41, a second detection unit 42, a third detection unit 43, and a fourth detection unit 44 via the plurality of diffraction gratings 21 of the scale 2. A signal detection step of detecting a signal from the signal at the signal detector 51 is executed (step ST01).

  As shown in FIGS. 5A and 5B, when the signal detection unit 51 executes the signal detection process, the signals in FIG. 5B are detected corresponding to the plurality of detection units 41 to 44. Specifically, (1) is a signal S1 from the first detector 41, (2) is a signal S2 from the third detector 43, and (3) is a signal S3 from the second detector 42. (4) is a signal S4 from the fourth detector 44. A portion E where the signal is attenuated in (1) to (4) is due to a contaminant (not shown) adhering to the scale 2.

  Next, as shown in FIG. 4, the measurement signal calculation unit 52 includes a signal from the first detection unit 41 (A phase signal, signal S1 in FIG. 5B) and a signal from the second detection unit 42 (a The phase signal, the signal S3 in FIG. 5B, is differentially calculated to calculate the first measurement signal, and the signal from the third detector 43 (the phase B signal, the signal S2 in FIG. 5B) and A measurement signal calculation step of calculating a second measurement signal by performing a differential operation on the signal (b-phase signal, signal S4 in FIG. 5B) from the fourth detection unit 44 is executed (step ST02).

  As shown in FIG. 5C, (5) is the first measurement signal S5, and (6) is the second measurement signal S6. The first measurement signal S5 and the second measurement signal S6 have the amplitude (fine amplitude) as the measurement signal, but the portion E where the signal is attenuated due to the adhering contaminant in FIG. 5B. Correspondingly, the measurement signal as a whole also has an amplitude (gradual amplitude).

Subsequently, as illustrated in FIG. 4, the extraction unit 53 performs an extraction process of extracting an abnormality determination signal from the first measurement signal S5 and the second measurement signal S6 using a low-pass filter (step ST03).
As shown in FIG. 5D, (7) is the abnormality determination signal S7 extracted from the first measurement signal S5, and (8) is the abnormality determination signal S8 extracted from the second measurement signal S6.

  As shown in FIG. 4, when abnormality determination signals S7 and S8 are extracted (step ST03), abnormality determination unit 54 determines whether there is an abnormality in scale 2 from abnormality determination signals S7 and S8. A process is executed (step ST04). As shown in FIG. 5D, the abnormality determination unit 54 determines abnormality depending on whether or not the abnormality determination signals S7 and S8 have a fluctuation component N.

  As shown in FIG. 4, when the abnormality determination unit 54 determines that there is an abnormality in the scale 2 (YES in step ST04), the abnormality notification unit 6 informs the user that the contaminant is attached to the scale 2. An abnormality notifying step for notifying is executed (step ST05). When abnormality determination unit 54 determines that there is no abnormality in scale 2 (NO in step ST04), abnormality determination unit 54 executes an abnormality determination step until it is determined that there is an abnormality in scale 2 (step ST04).

According to the present embodiment as described above, the following operations and effects can be achieved.
(1) In the encoder 1, the abnormality determination unit 54 determines whether or not there is an abnormality in the scale from the abnormality determination signals S7 and S8, that is, whether the fluctuation component N is steady or temporary. If it is temporary, it is determined that the scale 2 is abnormal.
Therefore, the encoder 1 can reliably discriminate between the signal fluctuation caused by the error factor of the encoder 1 and the signal fluctuation caused by the contaminants adhering to the scale 2 and detect the abnormality of the scale 2.

(2) The abnormality determination signals S7 and S8 extracted from the measurement signals S5 and S6 calculated by the differential calculation are abnormality determination signals with higher sensitivity than the abnormality determination signal based on the two-phase signal. Further, the signal detector 51 can detect a four-phase signal. At this time, the abnormality determination signals S7 and S8 extracted from the measurement signals S5 and S6 calculated by the differential calculation based on the four-phase signal are abnormality determination signals having higher sensitivity than the abnormality determination signal based on the two-phase signal. is there. Therefore, the encoder 1 uses the high-sensitivity abnormality determination signals S7 and S8 to more reliably discriminate between the signal fluctuation due to the error factor of the encoder 1 and the signal fluctuation due to the contaminant adhering to the scale 2. An abnormality of scale 2 can be detected.

(3) The measurement signal calculation unit 52 calculates the abnormality determination signals S7 and S8 having higher sensitivity than the abnormality determination signal extracted from the measurement signal calculated without using the differential operation by performing a differential operation. can do.
(4) Since the encoder 1 can change the plurality of detection elements 400 provided continuously along the X direction from the first detection unit 41 to the fourth detection unit 44, the plurality of detection units 41 to 44. By using the same number of detection elements 400, it is possible to easily design the detection means 4 that acquires signals necessary for calculating the abnormality determination signals S7 and S8.

(5) The measurement signal calculation unit 52 may differentially calculate signals having the same intensity when performing differential calculations on the A phase signal and the a phase signal, and the B phase signal and the b phase signal, respectively. it can. Therefore, the encoder 1 has a higher sensitivity abnormality determination than when the first detection unit 41 and the second detection unit 42 and the third detection unit 43 and the fourth detection unit 44 have different numbers of detection elements 400, respectively. Since the signals S7 and S8 can be used, the signal fluctuation caused by the error factor of the encoder 1 and the signal fluctuation caused by the contamination on the scale 2 are more reliably distinguished, and the abnormality of the scale 2 is detected. Can do.

(6) Since the plurality of detection units 41 to 44 have the same number of detection elements 400, the signal detection unit 51 can detect signals S1 to S4 having the same intensity from the detection units 41 to 44, respectively. . That is, the measurement signal calculation unit 52 performs a differential operation on these signals S1 to S4, and compares them with signals detected when the number of detection elements 400 of the plurality of detection units 41 to 44 is different. Thus, the first measurement signal S5 and the second measurement signal S6 with less noise can be calculated.
Therefore, the encoder 1 can detect an abnormality of the scale 2 by distinguishing between the signal fluctuation due to the error factor of the encoder 1 and the signal fluctuation caused by the contamination attached to the scale 2 with higher sensitivity.
(7) The encoder 1 can be easily mounted on an optical encoder.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. In the following description, parts that have already been described are assigned the same reference numerals and description thereof is omitted.

FIG. 6 is a diagram showing detection means in the encoder according to the second embodiment.
As shown in FIG. 2, the plurality of detection groups 40 of the detection unit 4 in the encoder 1 of the first embodiment includes a plurality of detection units 41 to 44, and the plurality of detection units 41 to 44 are along the X direction. And shifted by ¼. In addition, from the detection units 41 to 44, signals whose phases are shifted by ¼ period were detected.

  In the present embodiment, as shown in FIG. 6, in the detection means 4A in the encoder 1A, the plurality of detection groups 40A include a first detection unit 41A, a second detection unit 42A, and a third detection unit as the plurality of detection units 41A to 43A. 43A, the first detection unit 41A includes a plurality of detection elements 400, the second detection unit 42A includes a plurality of other detection elements 400 different from the first detection unit 41A, and the first detection unit 41A. Is a plurality of detection elements 400 arranged at positions shifted by 120 degrees, and the third detection unit 43A is a plurality of other detection elements 400 different from the first detection unit 41A and the second detection unit 42A. In addition, the second detector 42A differs from the first embodiment in that a plurality of detector elements 400 are arranged at positions shifted by 120 degrees in phase.

The plurality of detection units 41A to 43A are the same number of detection elements 400, and in the present embodiment, the plurality of detection units 41A to 43A are each four detection elements 400.
The plurality of detection units 41A to 43A are arranged with a shift of 1/3 along the X direction in the detection group 40A in the detection unit 4A. As a result, a signal whose phase is shifted by 1/3 period is detected from the plurality of detection units 41A to 43A. Then, signals having a phase shift of 120 degrees are detected from the first detection unit 41A, the second detection unit 42A, and the third detection unit 43A.

  In the first embodiment, as shown in FIG. 3, the calculation means 5 includes a signal detection unit 51 that detects a signal from each of the plurality of detection units 41 to 44, a signal from the first detection unit 41, and The signal from the second detector 42 is differentially calculated to calculate the first measurement signal, and the signal from the third detector 43 and the signal from the fourth detector 44 are differentially calculated to obtain the second measurement signal. And a measurement signal calculation unit 52 for calculating.

FIG. 7 is a block diagram showing calculation means in the encoder.
In the present embodiment, the calculation means 5A includes a signal detection unit 51A that detects signals from the first detection unit 41A, the second detection unit 42A, and the third detection unit 43A, and a signal from the first detection unit 41A. The first embodiment in that it includes a measurement signal calculation unit 52A that calculates a first measurement signal and a second measurement signal from a signal from the second detection unit 42A and a signal from the third detection unit 43A. And different.
Specifically, the measurement signal calculation unit 52A converts a three-phase signal detected from each of the first detection unit 41A, the second detection unit 42A, and the third detection unit 43A into a two-phase signal. The measurement signal calculation unit 52A calculates the first measurement signal and the second measurement signal from the signal converted from the three-phase signal to the two-phase signal.

Also in this embodiment, in addition to the same operations and effects as (1) and (4) to (7) in the first embodiment, the following operations and effects can be achieved.
(8) The signal detection unit 51A can detect a three-phase signal. The measurement signal calculation unit 52A calculates the first measurement signal and the second measurement signal from the three-phase signal. At this time, the abnormality determination signal extracted from the measurement signal calculated based on the three-phase signal is a higher sensitivity abnormality determination signal than the abnormality determination signal based on the two-phase signal. Therefore, the encoder 1A uses the high-sensitivity abnormality determination signal to more reliably distinguish between the signal fluctuation caused by the error factor of the encoder 1A and the signal fluctuation caused by the contamination attached to the scale 2, and the scale 2 Abnormalities can be detected.

(9) By using the same number of detection elements 400 in each of the plurality of detection units 41A to 43A, the measurement signal calculation unit 52A calculates a plurality of measurement signals when calculating the first measurement signal and the second measurement signal based on the three-phase signal. It is possible to calculate the first measurement signal and the second measurement signal with less noise compared to the signal detected when the number of detection elements 400 of the detection units 41A to 43A is different.
Therefore, the encoder 1A can detect the abnormality of the scale 2 by reliably distinguishing between the signal fluctuation due to the error factor of the encoder 1A and the signal fluctuation due to the contaminant adhering to the scale 2 with higher sensitivity. it can.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. In the following description, parts that have already been described are assigned the same reference numerals and description thereof is omitted.

FIG. 8 is a diagram showing detection means in the encoder according to the third embodiment.
In the detection means 4 in the encoder 1 of the first embodiment, as shown in FIG. 2, each of the plurality of detection units 41 to 44 includes four detection elements 400, and the plurality of detection groups 40 are arranged in the X direction. The reference of the length along was set to L, and was periodically arranged along the X direction.

  In the detection means 4B in the encoder 1B of the present embodiment, as shown in FIG. 8, the plurality of detection groups 40Ba to 40Bc include a first detection group 40Ba, a second detection group 40Bb, and a third detection group 40Bc. And different from the first embodiment in that the total number of the plurality of detection elements 400 is different. The plurality of detection groups 40Ba to 40Bc has a length L of each detection group in the plurality of detection groups 40Ba to 40Bc, where L is a reference for the length of each detection group 40Ba to 40Bc along the X direction. Are different from each other, have a common divisor including 1 and are arranged in combinations of lengths L of the detection groups 40Ba to 40Bc that do not become a common multiple of the length of the detection means 4B along the X direction. This is different from the first embodiment.

FIG. 9 is a diagram showing signals detected by the detecting means in the encoder.
Specifically, for example, when a contaminant T having the same size as the second detection group 40Bb adheres to the scale 2 (see FIG. 8), each of the detection units 41Ba to 44Ba of the first detection group 40Ba and the second detection group 40Bb. , 41Bb to 44Bb, no fluctuation component due to the pollutant T appears in the abnormality determination signal based on the signals. As shown in FIG. 9A, for example, when the size of the contaminant T is 2L, the first detection group 40Ba and the second detection group 40Bb have no signal fluctuation (no detection sensitivity).

  However, the third detection group 40Bc has a different total number of detection elements 400 from the first detection group 40Ba and the second detection group 40Bb, and has a larger detection area than the first detection group 40Ba and the second detection group 40Bb. Therefore, the contaminant T can be detected. Therefore, by setting a plurality of detection groups 40Ba to 40Bc having various lengths L along the X direction, the encoder 1B can cope with various sizes of contaminants, and the detection sensitivity may be lost. Can be prevented.

  Further, when the reference of the length of each of the detection groups 40Ba to 40Bc is L, the detection group length L of the plurality of detection groups 40Ba to 40Bc includes 1 and has no common divisor, and the detection means 4 It is preferable to be a combination of the lengths L of the detection groups 40Ba to 40Bc that do not become a common multiple of the length of. For example, as shown in FIG. 9B, L is set to L, 2.5L, 3.3L, and a combination of L including 1 and having no common divisor, that is, a length L that is relatively prime. By using this combination, it is possible to prevent the detection sensitivity from leaking that the contaminant cannot be detected by the plurality of detection groups 40Ba to 40Bc.

  In other words, the detection means 4B is a combination of the lengths L of the detection groups 40Ba to 40Bc that do not become the common multiple of the length of the detection means 4B, and the combination of the lengths L that minimizes the common multiple as much as possible. The detection sensitivity can be randomized. Therefore, the detection means 4B can cope with small contaminants and, for example, contaminants that cannot be detected by the detection means 4 (see FIG. 2) including the plurality of detection groups 40 having the same length L in the first embodiment. It is possible to prevent the occurrence of contamination detection sensitivity leakage. Therefore, the encoder 1B can suppress a decrease in measurement accuracy.

Also in this embodiment, in addition to the same operations and effects as (1) to (7) in the first embodiment, the following operations and effects can be achieved.
(10) Since the plurality of detection groups 40Ba to 40Bc are different in the total number of the plurality of detection elements 400 and have different areas where the contaminant T can be detected, the encoder 1B supports the contaminants T of various sizes. can do. Therefore, the encoder 1B can improve the determination of whether or not the contaminant T has adhered to the scale 2 and the detection sensitivity of the contaminant T.
(11) The plurality of detection groups 40Ba to 40Bc has a length L of the detection group in the plurality of detection groups 40Ba to 40Bc, where L is a reference for the length of each detection group 40Ba to 40Bc along the X direction. Are arranged in combinations of detection group lengths L that are different from each other and have no common divisor including 1 and do not become a common multiple of the length of the detection means 4B along the X direction. It is possible to suppress the occurrence of missing detection sensitivity depending on the length of the substance T.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in each of the embodiments described above, the encoders 1 and 1A to 1B are optical encoders and are linear encoders. However, the encoders may be rotary encoders instead of linear encoders, and optical encoders. Instead, an encoder of another type such as an electromagnetic induction type or a capacitance type may be used. In short, the encoder is not particularly limited in the type of detector, detection method, and the like.

  In each of the above embodiments, the extraction unit 53 extracts the abnormality determination signal by using a low-pass filter for the first measurement signal and the second measurement signal. However, the extraction unit is not a low-pass filter but a Fourier transform. The spectrum calculated by using may be extracted as an abnormality determination signal. At this time, the abnormality determination unit may determine the contaminant from the size of the spectrum. In short, the extraction unit may extract the abnormality determination signal using any technique as long as it can extract the abnormality determination signal.

In the first embodiment, the number of detection elements 400 of the plurality of detection units 41 to 44, 41A to 43A, and 41B to 44B is the same number (four each, etc.), but the same number of detection elements are used in the plurality of detection units. It does not have to be. That is, the first detection unit and the second detection unit may be the same number of detection elements 400, and the third detection unit and the fourth detection unit may be the same number of detection elements 400, or a plurality of detection units may have different numbers. It is good also as a detection element.
In short, as long as the signal detection unit can detect the signal and the extraction unit can extract the abnormality determination signal, the number of detection elements may be set in any of the plurality of detection units.

  In the first embodiment, unlike the plurality of detection elements 400 of the first detection unit 41 and the plurality of detection elements 400 of the third detection unit 43, the plurality of detection elements 400 and the fourth detection unit of the second detection unit 42 are used. The first detection unit 41 and the third detection unit 43 may be the same detection element 400, or the second detection unit 42 and the fourth detection unit 44 may be different from each other. The same detection element 400 may be used. In short, if the measurement signal can be calculated by performing a differential operation on a certain signal and a signal that is 180 degrees out of phase in the measurement signal calculation unit, the plurality of detection units detect a plurality of the same detection elements. It is good also as a part.

  In the first embodiment, the measurement signal calculation unit 52 calculates the first measurement signal and the second measurement signal by performing a differential operation on the four-phase signals from the plurality of detection units 41 to 44, and the second embodiment. In the embodiment, the measurement signal calculation unit 52A converts the three-phase signals from the plurality of detection units 41A to 43A into the two-phase signals and calculates the first measurement signal and the second measurement signal. However, the measurement signal calculation unit The measurement signal may be calculated by another calculation method without using the differential calculation or the method of converting the three-phase signal to the two-phase signal. In short, the measurement signal calculation unit may calculate the measurement signal using any method as long as the measurement signal can be calculated using the signal detected by the signal detection unit.

In the third embodiment, the plurality of detection groups 40Ba to 40Bc include the first detection group 40Ba, the second detection group 40Bb, and the third detection group 40Bc. Only the detection group may be provided, or the fourth detection group and the fifth detection group may be provided. In short, the plurality of detection groups need only include a plurality of detection elements and be arranged in parallel along the measurement direction.
In the third embodiment, as shown in FIG. 8, the length of the first detection group 40Ba is L, the length of the second detection group 40Bb is 2L, and the length of the third detection group 40Bc is 4L. However, for example, the length of the first detection group may be 4L, the length of the second detection group may be L, and the length of the third detection group may be 2L. In short, the plurality of detection groups have different total numbers of the plurality of detection elements and may have different lengths.

  In the first embodiment, the detection element 400 is designed to be 4 μm and the detection group L is designed to be 200 μm. However, the detection element and the detection group may be designed to have an arbitrary size.

  As described above, the present invention can be suitably used for an encoder and an encoder control method.

DESCRIPTION OF SYMBOLS 1,1A-1B Encoder 2 Scale 3 Light source 4, 4A-4B Detection means 5, 5A Calculation means 51, 51A Signal detection part 52, 52A Measurement signal calculation part 53 Extraction part 54 Abnormality determination part 40, 40A-40B Detection group 41 , 41A to 41B First detection unit 42, 42A to 42B Second detection unit 43, 43A to 43B Third detection unit 44, 44A to 44B Fourth detection unit

Claims (11)

A scale having a scale arranged in parallel along the measurement direction, and a detecting means that detects relative to the scale along the scale and detects signals via the scale by a plurality of detection elements arranged in parallel along the measurement direction. And a calculation means for calculating a relative movement amount between the scale and the detection means based on the signal,
The detection means includes
A plurality of detection groups including a plurality of the detection elements and arranged in parallel along the measurement direction,
The plurality of detection groups include a plurality of detection units arranged in parallel along the measurement direction,
The plurality of detection units are:
The predetermined detection element is a first detection unit,
When the other detection element different from the first detection unit is a second detection unit,
The calculating means includes
A signal detection unit for detecting signals from each of the first detection unit and the second detection unit;
A measurement signal calculation unit that calculates a measurement signal using the signal detected by the signal detection unit;
An extraction unit for extracting an abnormality determination signal for determining abnormality of the scale from the measurement signal calculated by the measurement signal calculation unit;
An encoder for determining whether there is an abnormality in the scale from the abnormality determination signal. The encoder according to claim 1,
The plurality of detection elements are juxtaposed corresponding to the scale,
The plurality of detection groups include a first detection unit, a second detection unit, a third detection unit, and a fourth detection unit as the plurality of detection units,
The first detection unit is a plurality of the detection elements,
The second detection unit is a plurality of the detection elements different from the first detection unit and a plurality of the detection elements arranged at positions 180 degrees out of phase with the first detection unit,
The third detection unit is a plurality of other detection elements different from the second detection unit,
The fourth detection unit is a plurality of other detection elements different from the third detection unit, and a plurality of the detection elements arranged at positions that are 180 degrees out of phase with the third detection unit. In case,
The signal detection unit detects signals from each of the first detection unit, the second detection unit, the third detection unit, and the fourth detection unit,
The measurement signal calculation unit calculates the first measurement signal based on the signal from the first detection unit and the signal from the second detection unit, and the signal from the third detection unit and the fourth detection unit. Calculating a second measurement signal based on the signal from
The extraction unit extracts an abnormality determination signal from the first measurement signal and the second measurement signal,
The said abnormality determination part determines whether there is abnormality in the said scale from the said abnormality determination signal, The encoder characterized by the above-mentioned. The encoder according to claim 2,
The measurement signal calculation unit calculates a first measurement signal by performing a differential operation on the signal from the first detection unit and the signal from the second detection unit, and the signal from the third detection unit and the first 4. An encoder characterized in that a second measurement signal is calculated by differentially calculating a signal from a detection unit. The encoder according to claim 1,
The plurality of detection elements are juxtaposed corresponding to the scale,
The plurality of detection groups include a first detection unit, a second detection unit, and a third detection unit as the plurality of detection units,
The first detection unit is a plurality of the detection elements,
The second detection unit is a plurality of the detection elements different from the first detection unit and a plurality of the detection elements arranged at a position 120 degrees out of phase with the first detection unit,
The third detection unit is a plurality of other detection elements different from the first detection unit and the second detection unit, and a plurality of third detection units are arranged at positions that are 120 degrees out of phase with the second detection unit. When the detection element is used,
The signal detection unit detects signals from each of the first detection unit, the second detection unit, and the third detection unit,
The measurement signal calculation unit calculates the first measurement signal and the second measurement signal based on the signal from the first detection unit, the signal from the second detection unit, and the signal from the third detection unit. Calculate
The extraction unit extracts an abnormality determination signal from the first measurement signal and the second measurement signal,
The said abnormality determination part determines whether there is abnormality in the said scale from the said abnormality determination signal, The encoder characterized by the above-mentioned. The encoder according to claim 2 or claim 3,
The third detector is
The first detection unit and the second detection unit are a plurality of other detection elements different from each other, and the first detection unit is a plurality of detection elements arranged at a phase shifted by 90 degrees,
The fourth detector is
The first detection unit, the second detection unit, and the third detection unit are a plurality of other detection elements different from each other and arranged at a position that is 90 degrees out of phase with the second detection unit, and The encoder according to claim 3, wherein the third detection unit includes a plurality of detection elements arranged at positions shifted in phase by 180 degrees. In the encoder according to any one of claims 2, 3 and 5,
The first detection unit and the second detection unit are the same number of the detection elements,
The third detection unit and the fourth detection unit include the same number of detection elements. The encoder according to any one of claims 1 to 6,
The plurality of detection units are:
An encoder characterized by having the same number of detection elements. The encoder according to any one of claims 1 to 7,
The encoder, wherein the plurality of detection groups have different total numbers of the plurality of detection elements. The encoder according to any one of claims 1 to 8,
The plurality of detection groups are:
When the reference of the length of each detection group along the measurement direction is L,
The length L of the detection group in the plurality of detection groups is
They are different from each other, have a common divisor including 1 and are arranged in a combination of the lengths L of the detection groups that do not become a common multiple of the length of the detection means along the measurement direction. Encoder. The encoder according to any one of claims 1 to 9,
An encoder comprising: a light source that irradiates light to the scale; and a detection unit that receives light through the scale and detects a signal. A scale having a scale arranged in parallel along the measurement direction, and a detecting means that detects relative to the scale along the scale and detects signals via the scale by a plurality of detection elements arranged in parallel along the measurement direction. And a calculation means for calculating a relative movement amount between the scale and the detection means based on the signal, and an encoder control method comprising:
The detection means includes
A plurality of detection groups including a plurality of the detection elements and arranged in parallel along the measurement direction,
The plurality of detection groups include a plurality of detection units arranged in parallel along the measurement direction,
The plurality of detection units are:
The predetermined detection element is a first detection unit,
When the other detection element different from the first detection unit is a second detection unit,
The calculating means includes
A signal detection step of detecting signals from each of the first detection unit and the second detection unit;
A measurement signal calculation step of calculating a measurement signal using the signal detected by the signal detection unit;
An extraction step of extracting an abnormality determination signal for determining abnormality of the scale from the measurement signal calculated by the measurement signal calculation unit;
And an abnormality determination step of determining whether or not the scale has an abnormality from the abnormality determination signal.

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