JP7066264B2 - Encoder and encoder control method - Google Patents

Description

The present invention relates to an encoder and a control method for the encoder.

Conventionally, a scale having a scale along the measurement direction, a detection means that moves relative to the scale and detects a signal via the scale, and a calculation means that calculates the relative movement amount between the scale and the detection means based on the signal. And, an encoder equipped with is known.
By using such an encoder, contaminants such as dust and metal powder in the environment of use 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 the measuring instrument or machine tool equipped with the encoder and check for the presence or absence of contaminants adhering to the scale. The presence or absence of contaminants adhering to the scale cannot be known until the user confirms it, and there is a problem that it takes time and effort to confirm.

On the other hand, for example, the photoelectric encoder (encoder) described in Patent Document 1 has a main scale (scale), an index scale arranged so as to be relatively displaceable with respect to the main scale, and an index scale with respect to the main scale. Multiple light receiving elements (detection means) that output a plurality of periodic signals having different phases according to the relative displacement amount and output a plurality of periodic signals of the same phase among a plurality of periodic signals, and a plurality of signal stability determinations. It includes means and a signal synthesis circuit.

The plurality of signal stability determining means inputs the periodic signals output by the plurality of light receiving elements and outputs only the periodic signals determined to have no abnormality. The signal synthesis circuit synthesizes periodic signals output by a plurality of signal stability determination means to generate one periodic signal. The photoelectric encoder uses only periodic signals determined by a plurality of signal stability determination means that no contaminants are attached to the main scale (no abnormality), and the relative displacement amount (one) in the signal synthesis circuit. Periodic signal) is generated.
Therefore, since the photoelectric encoder obtains the relative movement amount from the periodic signal having no abnormality, it is possible to suppress the deterioration of the measurement accuracy. Further, since the user only needs to confirm the main scale when it is determined by the plurality of signal stability determination means that there is an abnormality, the time and effort for confirmation can be reduced.

Japanese Patent Application Laid-Open No. 2003-65803

However, in the photoelectric encoder described in Patent Document 1, a plurality of signal stability determining means determine the presence or absence of an abnormality from light shielding by a contaminant.
Here, the encoder has undulations of the scale due to the material of the scale and the manufacturing process, misalignment between the scale and the detection means, signal increase or signal decrease (signal fluctuation) due to deterioration of the light source, uneven reflectance of the scale, etc. Has an error factor of. Signal fluctuations such as signal increase and signal decrease due to error factors are almost the same as signal fluctuations due to contaminants smaller than a predetermined size attached to the scale. Further, the encoder is provided with a correction means for canceling this error factor in advance.

Therefore, when the pollutant adhering 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 adhering of the pollutant. Signal fluctuations may be corrected as signal fluctuations due to error factors. Therefore, there is a problem that the encoder may not be able to detect an abnormality due to the adhesion of a contaminant to the scale.

An object of the present invention is to provide an encoder capable of reliably distinguishing between signal fluctuations due to an error factor possessed by an encoder and signal fluctuations due to adhesion of a contaminant to the scale, and detecting an abnormality in the scale.

The encoder of the present invention is a scale having a scale arranged side by side along the measurement direction, and a plurality of detection elements moving relative to each other along the scale and arranging signals through the scale side by side along the measurement direction. An encoder including a detection means for detecting and a calculation means for calculating the relative movement amount between the scale and the detection means based on a signal. The detection means include a plurality of detection elements and are arranged side by side along a measurement direction. The plurality of detection groups are provided with a plurality of detection groups arranged side by side along the measurement direction, and the plurality of detection units have a predetermined detection element as a first detection unit and a first detection unit. When another detection element different from the detection unit is used as the second detection unit, the calculation means is 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. A measurement signal calculation unit that calculates a measurement signal using the detected signal, an extraction unit that extracts an abnormality judgment signal that determines a scale abnormality from the measurement signal calculated by the measurement signal calculation unit, and a scale from the abnormality judgment signal. It is characterized by comprising an abnormality determination unit for determining whether or not there is an abnormality in.

Here, if the encoder has no error factor and no contaminants adhere to the scale, the abnormality determination signal is detected as a uniform signal. Further, when the encoder has an error factor, the abnormality determination signal is detected in a state where it constantly has a fluctuation component due to signal fluctuation. On the other hand, when a contaminant adheres to the scale, the abnormality determination signal is detected in a state of temporarily having a variable component.
Therefore, the abnormality determination unit determines whether the fluctuation component is stationary (encoder error factor) or temporary (adhesion of contaminants to the scale) in the abnormality determination signal, and the fluctuation component is temporary. If so, it is determined that the scale is abnormal.
Further, the plurality of detection units specify the position and number of the detection elements that detect the signal used for calculating the abnormality determination signal among the plurality of detection elements arranged side by side along the measurement direction.

Therefore, according to the present invention, the signal detection unit can detect at least two phases of signals from the first detection unit and the second detection unit. Then, the measurement signal is calculated by the measurement signal calculation unit based on the signals from each of the first detection unit and the second detection unit detected by the signal detection unit. The extraction unit extracts an abnormality determination signal for determining a scale abnormality from the measurement signal, and the abnormality determination unit determines whether or not there is an abnormality in the scale from the abnormality determination signal, that is, whether the variable component is stationary or temporary. , And if the variable component is temporary, it is determined that there is an abnormality in the scale.
Therefore, the encoder can reliably distinguish between the signal fluctuation due to the error factor of the encoder and the signal fluctuation due to the adhesion of a contaminant to the scale, and can detect the abnormality of the scale.

At this time, a plurality of detection elements are arranged side by side corresponding to the scale, and the plurality of detection groups have a first detection unit, a second detection unit, a third detection unit, and a fourth detection unit as a 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 the second detection unit is 180 degrees out of phase with the first detection unit. A plurality of detection elements are 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 a plurality of detection elements are arranged at positions 180 degrees out of phase with the third detection unit, the signal detection unit includes the first detection unit, the second detection unit, the third detection unit, and the fourth. Signals are detected from each of the detection units, and 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 also from the third detection unit. The second measurement signal is calculated based on the signal and the signal from the fourth detection unit, the extraction unit extracts the abnormality determination signal from the first measurement signal and the second measurement signal, and the abnormality determination unit extracts the abnormality determination signal from the abnormality determination signal. It is preferable to determine whether or not there is an abnormality in the scale.

Here, the signal detected from the first detection unit is defined as an A-phase signal, the signal detected from the second detection unit and 180 degrees out of phase with the A-phase signal is defined as an a-phase signal, and is detected by the third detection unit. The signal to be generated is referred to as a B-phase signal, and a signal detected by the fourth detection unit and having a phase shift of 180 degrees from the B-phase signal is referred to as a b-phase signal.

According to such a configuration, the signal detection unit is based on the signals detected from the plurality of detection units, and the measurement signal calculation unit is the signal (A phase signal) from the first detection unit 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 from the third detection unit (B phase signal) and the signal from the fourth detection unit (b phase signal). Is calculated. The extraction unit can extract the abnormality determination signal from the first measurement signal and the second measurement signal, and the abnormality determination unit can determine whether or not 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 having higher sensitivity than the abnormality determination signal based on the two-phase signal. Therefore, by using a highly sensitive abnormality determination signal, the encoder more reliably distinguishes between signal fluctuations due to error factors possessed by the encoder and signal fluctuations due to contaminants adhering to the scale, and detects scale abnormalities. can do.

At this time, the measurement signal calculation unit calculates the first measurement signal by differentially calculating the signal from the first detection unit and the signal from the second detection unit, and also calculates the signal from the third detection unit and the fourth detection unit. It is preferable to calculate the second measurement signal by differentially calculating the signal from the unit.

According to such a configuration, the measurement signal calculation unit differentially calculates the signal from the first detection unit and the signal from the second detection unit to calculate the first measurement signal, and the signal from the third detection unit. And the signal from the fourth detection unit can be differentially calculated to calculate the second measurement signal. 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, by using a highly sensitive abnormality determination signal, the encoder more reliably distinguishes between signal fluctuations due to error factors possessed by the encoder and signal fluctuations due to contaminants adhering to the scale, and detects scale abnormalities. can do.

At this time, a 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 a plurality of detection units, and the first detection unit is provided. 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 the second detection unit is a plurality of detection elements arranged at positions 120 degrees out of phase with the first detection unit. As a detection element, 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 detection elements arranged at positions 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 receives the signal from the first detection unit and 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 determines an abnormality from the first measurement signal and the second measurement signal. It is preferable that the signal is extracted and the abnormality determination unit 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 an abnormality determination signal having higher sensitivity than the abnormality determination signal based on the two-phase signal. Therefore, by using a highly sensitive abnormality determination signal, the encoder more reliably distinguishes between signal fluctuations due to error factors possessed by the encoder and signal fluctuations due to contaminants adhering to the scale, and detects scale abnormalities. can do.

At this time, 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 detection units arranged at positions that are 90 degrees out of phase with the first detection unit. The fourth detection unit is an element, and 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 shifted by 90 degrees from the second detection unit. It is preferable that the plurality of detection elements are arranged at positions that are 180 degrees out of phase with the third detection unit.

According to such a configuration, the first detection unit to the fourth detection unit are arranged at positions that are 90 degrees out of phase with each other. Then, the signal detection unit can detect the four-phase signal. At this time, the abnormality determination signal calculated by the differential calculation 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, by using a highly sensitive abnormality determination signal, the encoder more reliably distinguishes between signal fluctuations due to error factors possessed by the encoder and signal fluctuations due to contaminants adhering to the scale, and detects scale abnormalities. can do.
Further, since the encoder can use, for example, a plurality of detection elements continuously provided along the measurement direction from the first detection unit to the fourth detection unit, the signal necessary for calculating the abnormality determination signal is acquired. The detection means to be used can be easily designed.

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 a signal of the same intensity from the first detection unit and the second detection unit, and detects a signal 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 an abnormality determination signal having 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 distinguish between the signal fluctuation due to the error factor of the encoder and the signal fluctuation due to the adhesion of contaminants to the scale, and detect the abnormality of the scale.

At this time, it is preferable that the plurality of detection units have the same number of detection elements.

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

Further, when the measurement signal calculation unit calculates the first measurement signal and the second measurement signal based on, for example, a three-phase signal, the measurement signal calculation unit is compared with a signal detected when the number of detection elements of the plurality of detection units is different. The first measurement signal and the second measurement signal with less noise can be calculated.
Therefore, the encoder can reliably distinguish between the signal fluctuation due to the error factor possessed by the encoder and the signal fluctuation due to the adhesion of contaminants to the scale, and can detect the abnormality of the scale with higher sensitivity.
Further, by using the same number of detection elements for each of the plurality of detection units, the detection means can be easily designed.

At this time, it is preferable that the total number of the plurality of detection elements is different in each of the plurality of detection groups.

Here, when a contaminant of the same size as a certain detection group (the same length as the length along the measurement direction of a certain detection group) adheres to the scale, the same is true from each of the plurality of detection parts in the certain detection group. Since the signal is detected, no variable component is generated in the abnormality determination signal extracted by the extraction unit. Therefore, there is a problem that the encoder may not be able to detect the presence or absence of a pollutant (abnormal scale).

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

At this time, when the reference of the length of each detection group along the measurement direction is L for the plurality of detection groups, the length L of the detection group in the plurality of detection groups is different and includes 1. It is preferable that they are arranged in a combination of length L of the detection group, which has no common divisor and does not have a common multiple equal to or larger than the length of the detection means along the measurement direction.

Here, for example, in a plurality of detection groups, 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 4 L of the length of the detection group. If the lengths are the same, the detection group having a length of 2 L and the detection group having a length of 4 L cannot detect the contaminants, and there is a problem that the detection sensitivity may be lost.

However, according to the present invention, when the reference of the length of each detection group along the measurement direction is L, the length of the detection group in the plurality of detection groups is determined by the plurality of detection groups. The length of the pollutants is different because they are different from each other and have no common divisor including 1 and are arranged in a combination of length L of the detection group which is not a common multiple equal to or more than the length of the detection means along the measurement direction. As a result, it is possible to prevent the detection sensitivity from being lost.

At this time, the encoder of the present invention is preferably an optical encoder including a light source that irradiates the scale with light and a detection means that receives light through the scale and detects a signal.

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

The control method of the encoder of the present invention includes a scale having a scale arranged side by side along the measurement direction, and a plurality of detections in which signals moving along the scale and passing through the scale are arranged side by side along the measurement direction. It is a control method of an encoder including a detection means for detecting by an element and a calculation means for calculating a relative movement amount between a scale and the detection means based on a signal, and the detection means includes a plurality of detection elements and measures. A plurality of detection groups arranged side by side along the direction are provided, the plurality of detection groups include a plurality of detection units arranged side by side along the measurement direction, and the plurality of detection units first provide a predetermined detection element. When the detection unit is a detection unit and another detection element different from the first detection unit is the second detection unit, the calculation means includes a signal detection step of detecting a signal from each of the first detection unit and the second detection unit. , A measurement signal calculation step of calculating a measurement signal using a signal detected by the signal detection unit, and an extraction step of extracting an abnormality determination signal for determining a scale abnormality from the measurement signal calculated by the measurement signal calculation unit. It is characterized by comprising an abnormality determination step of determining whether or not there is an abnormality in the scale from the abnormality determination signal.

According to the present invention, the control method of the encoder calculates the measurement signal in the measurement signal calculation step based on the signals from each of 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 a scale abnormality 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, whether the variable component is stationary or temporary. If the variable component is temporary, it is determined that there is an abnormality in the scale.
Therefore, the encoder control method can reliably distinguish between signal fluctuations due to an error factor possessed by the encoder and signal fluctuations due to the adhesion of contaminants to the scale, and can detect scale abnormalities.

A perspective view showing an encoder according to the first embodiment. The figure which shows the detection means in the encoder. A block diagram showing a calculation means in the encoder. A 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 A block diagram showing a 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 encoder.

[First Embodiment]
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 5.
FIG. 1 is a perspective view showing an encoder according to the first embodiment.
As shown in FIG. 1, the encoder 1 moves relative to a long scale 2, a light source 3 that irradiates the scale 2 with light, and receives light through the scale 2 to receive a signal. An optical encoder including a detection means 4 for detection.

The scale 2 has a plurality of diffraction gratings 21 which are scales arranged side by side along the measurement direction. The scale 2 is made of translucent glass. 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 the LED, and may be any light source.

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

The detection means 4 includes a plurality of detection elements 400 arranged side by side along the measurement direction (X direction). The plurality of detection elements 400 are arranged side by side 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. A PDA (Photo Diode Array) is used for the plurality of detection elements 400. A PDA is a detector having the property of being able to measure a plurality of interference fringes at once. The plurality of detection elements 400 are not limited to PDA, and any detector such as PSD (Position Sensitive Detector) or CCD (Charge-Coupled Device) may be used.
Further, the light source 3 and the detecting means 4 are installed facing each other so as to overlap each other with the scale 2 interposed therebetween. The detection means 4 receives the light from the light source 3 through the plurality of diffraction gratings 21 of the scale 2, and detects the signal from the interference fringes generated on the detection means 4 (the plurality of detection elements 400) by the light.

FIG. 2 is a diagram showing a detection means in the encoder.
As shown in FIG. 2, the detection means 4 includes a plurality of detection elements 400 and includes a plurality of detection groups 40 arranged side by side in the X direction. The detection means 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 side by side in 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 is a plurality of detection elements 400, the second detection unit 42 is a plurality of other detection elements 400 different from the first detection unit 41, and the phase is 180 degrees with the first detection unit 41. A plurality of detection elements 400 are arranged at offset 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 shifted by 90 degrees from the first detection unit 41. The fourth detection unit 44 is 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 arranged at positions that are 90 degrees out of phase with, and 180 degrees out of phase with the third detection unit 43.

The plurality of detection units 41 to 44 each have the same number of detection elements 400, and in the present embodiment, the plurality of detection units 41 to 44 each have four detection elements 400.
The plurality of detection units 41 to 44 are arranged so as to be offset by 1/4 along the X direction in the detection group 40 in the detection means 4. As a result, signals that are out of phase by 1/4 period are detected from the plurality of detection units 41 to 44. Then, the A phase signal is detected from the first detection unit 41, the a phase signal whose phase is 180 degrees out of phase with the A phase signal is detected from the second detection unit 42, and the A phase is detected from the third detection unit 43. 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 detection unit 44.

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

FIG. 3 is a block diagram showing a calculation means in the encoder.
As shown in FIG. 3, the encoder 1 further includes a calculation means 5 for calculating the relative movement amount between the scale 2 and the detection means 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 each of 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, the a phase signal from the second detection unit 42, and 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 the first measurement signal by differentially calculating the signal from the first detection unit 41 and the signal from the second detection unit 42, and also calculates the signal from the third detection unit 43 and the fourth. The signal from the detection unit 44 is differentially calculated to calculate the second measurement signal.
Specifically, the measurement signal calculation unit 52 calculates the first measurement signal for calculating the relative movement amount by differentially calculating the A-phase signal and the a-phase signal. Further, the measurement signal calculation unit 52 calculates a second measurement signal for calculating the relative movement amount by differentially calculating 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 or not there is an abnormality in the scale 2 from the abnormality determination signal. Here, the abnormality on the scale 2 is that a pollutant adheres 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 or the like. The abnormality notification unit is not limited to the buzzer, and may be any type as long as it can notify the user of the abnormality, such as displaying a warning on the display or blinking the indicator lamp (LED). ..

FIG. 4 is a flowchart showing an abnormality detection method in the encoder, and FIG. 5 is a diagram showing a signal calculated by a calculation means in the encoder. Specifically, FIG. 5A is a diagram showing the detection means 4, and FIG. 5B is each signal detected from the first detection unit 41 to the fourth detection unit 44, and FIG. 5B. (C) is a first measurement signal and a second measurement signal, and 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. 4 and 5.

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

As shown in FIGS. 5A and 5B, when the signal detection unit 51 executes the signal detection step, the signal of FIG. 5B is detected corresponding to the plurality of detection units 41 to 44. Specifically, (1) is a signal S1 from the first detection unit 41, (2) is a signal S2 from the third detection unit 43, and (3) is a signal S3 from the second detection unit 42. (4) is the signal S4 from the fourth detection unit 44. The portion E where the signal is attenuated in (1) to (4) is due to the adhesion of a contaminant (not shown) 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 (phase A signal, signal S1 in FIG. 5B) and a signal from the second detection unit 42 (a). The phase signal, the signal S3) in FIG. 5 (B) is differentially calculated to calculate the first measurement signal, and the signal from the third detection unit 43 (Phase B signal, signal S2 in FIG. 5 (B)) and The measurement signal calculation step of calculating the second measurement signal by differentially calculating 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 an amplitude (fine amplitude) as a measurement signal, but the portion E where the signal is attenuated due to the adhesion of the contaminant in FIG. 5 (B). Corresponding to, the measurement signal as a whole also has an amplitude (gentle amplitude).

Subsequently, as shown in FIG. 4, the extraction unit 53 executes an extraction step 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 an abnormality determination signal S7 extracted from the first measurement signal S5, and (8) is an abnormality determination signal S8 extracted from the second measurement signal S6.

As shown in FIG. 4, when the abnormality determination signals S7 and S8 are extracted (step ST03), the abnormality determination unit 54 determines whether or not there is an abnormality in the scale 2 from the abnormality determination signals S7 and S8. The process is executed (step ST04). As shown in FIG. 5D, the abnormality determination unit 54 determines the abnormality depending on whether or not the abnormality determination signals S7 and S8 have the variable 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 scale 2 has a contaminant. The abnormality notification process for notification is executed (step ST05). When the abnormality determination unit 54 determines that there is no abnormality in the scale 2 (NO in step ST04), the abnormality determination unit 54 executes the abnormality determination step until it is determined that there is an abnormality in the scale 2 (step ST04).

According to such an embodiment, the following actions / effects can be obtained.
(1) In the encoder 1, the abnormality determination unit 54 determines from the abnormality determination signals S7 and S8 whether or not there is an abnormality in the scale, that is, whether the fluctuation component N is steady or temporary, and the fluctuation component N is determined. If it is temporary, it is determined that the scale 2 has an abnormality.
Therefore, the encoder 1 can reliably distinguish between the signal fluctuation due to the error factor of the encoder 1 and the signal fluctuation due to the adhesion of the contaminant to the scale 2, and can 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 having higher sensitivity than the abnormality determination signals based on the two-phase signals. Further, the signal detection unit 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 differential calculation based on the four-phase signal are abnormality determination signals having higher sensitivity than the abnormality determination signals based on the two-phase signals. be. Therefore, the encoder 1 uses the high-sensitivity abnormality determination signals S7 and S8 to more reliably distinguish between the signal fluctuation due to the error factor of the encoder 1 and the signal fluctuation due to the adhesion of contaminants 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 calculation by performing the differential calculation. can do.
(4) Since the encoder 1 can have a plurality of detection elements 400 continuously provided along the X direction as the first detection unit 41 to the fourth detection unit 44, the encoder 1 also has a plurality of detection units 41 to 44. By using the same number of detection elements 400 for each, it is possible to easily design the detection means 4 for acquiring the signals necessary for calculating the abnormality determination signals S7 and S8.

(5) When the measurement signal calculation unit 52 differentially calculates the A-phase signal and the a-phase signal, and the B-phase signal and the b-phase signal, the signals having the same intensity may be differentially calculated. can. Therefore, the encoder 1 has higher sensitivity 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. Since the signals S7 and S8 can be used, it is possible to more reliably distinguish between the signal fluctuation due to the error factor of the encoder 1 and the signal fluctuation due to the adhesion of contaminants to the scale 2 and detect the abnormality of the scale 2. Can be done.

(6) By setting the plurality of detection units 41 to 44 to 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 respective detection units 41 to 44. .. That is, the measurement signal calculation unit 52 performs differential calculation on these signals S1 to S4, and compares the signals detected when the number of detection elements 400 of the plurality of detection units 41 to 44 is different. The first measurement signal S5 and the second measurement signal S6 with less noise can be calculated.
Therefore, the encoder 1 can detect the abnormality of the scale 2 by distinguishing the signal fluctuation due to the error factor possessed by the encoder 1 and the signal fluctuation due to the adhesion of the contaminant to the scale 2 with higher sensitivity.
(7) The encoder 1 can be easily mounted on an optical encoder.

[Second Embodiment]
Hereinafter, the second embodiment of the present invention will be described with reference to FIGS. 6 and 7. In the following description, the parts already described will be designated by the same reference numerals and the description thereof will be 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 means 4 in the encoder 1 of the first embodiment include a plurality of detection units 41 to 44, and the plurality of detection units 41 to 44 are along the X direction. They were arranged so as to be offset by 1/4. In addition, signals that were out of phase by 1/4 period were detected from the detection units 41 to 44.

In the present embodiment, as shown in FIG. 6, in the detection means 4A in the encoder 1A, the plurality of detection groups 40A are the first detection unit 41A, the second detection unit 42A, and the third detection unit 41A to 43A as the plurality of detection units 41A to 43A. A unit 43A is provided, the first detection unit 41A is a plurality of detection elements 400, and the second detection unit 42A is 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 in phase by 120 degrees, and the third detection unit 43A is another plurality of detection elements 400 different from the first detection unit 41A and the second detection unit 42A. The second detection unit 42A is different from the first embodiment in that the plurality of detection elements 400 are arranged at positions that are 120 degrees out of phase with each other.

The plurality of detection units 41A to 43A each have the same number of detection elements 400, and in the present embodiment, the plurality of detection units 41A to 43A each have four detection elements 400.
The plurality of detection units 41A to 43A are arranged so as to be offset by 1/3 along the X direction in the detection group 40A in the detection means 4A. As a result, signals that are out of phase by 1/3 cycle are detected from the plurality of detection units 41A to 43A. Then, signals out of phase by 120 degrees are detected from the first detection unit 41A, the second detection unit 42A, and the third detection unit 43A, respectively.

Further, 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 a signal from the first detection unit 41. The signal from the second detection unit 42 is differentially calculated to calculate the first measurement signal, and the signal from the third detection unit 43 and the signal from the fourth detection unit 44 are differentially calculated to calculate the second measurement signal. It was provided with a measurement signal calculation unit 52 for calculating the above.

FIG. 7 is a block diagram showing a calculation means in the encoder.
In the present embodiment, the calculation means 5A includes a signal detection unit 51A that detects a signal from each of 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 is provided with a signal from the second detection unit 42A, a signal from the third detection unit 43A, and a measurement signal calculation unit 52A for calculating the first measurement signal and the second measurement signal. Is different.
Specifically, the measurement signal calculation unit 52A converts the 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 such an embodiment, in addition to being able to exert the same actions and effects as those of (1), (4) to (7) in the first embodiment, the following actions and effects can be obtained.
(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 an abnormality determination signal having higher sensitivity than the abnormality determination signal based on the two-phase signal. Therefore, the encoder 1A more reliably distinguishes between the signal fluctuation due to the error factor possessed by the encoder 1A and the signal fluctuation due to the adhesion of contaminants to the scale 2 by using the high-sensitivity abnormality determination signal, and the scale 2 Abnormality can be detected.

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

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. 8 and 9. In the following description, the parts already described will be designated by the same reference numerals and the description thereof will be omitted.

FIG. 8 is a diagram showing detection means in the encoder according to the third embodiment.
In the detection means 4 of the encoder 1 of the first embodiment, as shown in FIG. 2, it is assumed that each of the plurality of detection units 41 to 44 is four detection elements 400, respectively, in the X direction of the plurality of detection groups 40. The reference for the length along the line was L, and the length 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. It is different from the first embodiment in that the total number of the plurality of detection elements 400 is different from each other. Further, the plurality of detection groups 40Ba to 40Bc have the length L of each detection group in the plurality of detection groups 40Ba to 40Bc, where L is the reference for the length of each detection group 40Ba to 40Bc along the X direction. Are different from each other, and are arranged in a combination of lengths L of detection groups 40Ba to 40Bc, including 1 and having no common divisor with each other and not having a common multiple equal to or greater than the length of the detection means 4B along the X direction. Is different from the first embodiment.

FIG. 9 is a diagram showing a signal detected by the detection means in the encoder.
Specifically, for example, when the contaminant T having the same size as that of the second detection group 40Bb adheres to the scale 2 (see FIG. 8), the detection units 41Ba to 44Ba of the first detection group 40Ba and the second detection group 40Bb are respectively. , 41Bb-44Bb, the variation component due to the contaminant T does not appear in the abnormality determination signal based on the signal. As shown in FIG. 9A, for example, when the size of the contaminant T is 2 L, there is no signal fluctuation (no detection sensitivity) between the first detection group 40Ba and the second detection group 40Bb.

However, the third detection group 40Bc has a plurality of detection elements 400 having a different total number from the first detection group 40Ba and the second detection group 40Bb, and has a detection area larger than that of the first detection group 40Ba and the second detection group 40Bb. Since it has, the pollutant 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 deal with contaminants of various sizes, and the detection sensitivity is lost. Can be prevented.

Further, when the reference of the length of each of the detection groups 40Ba to 40Bc is L, the length L of the detection groups in the plurality of detection groups 40Ba to 40Bc includes 1 and has no common divisor with each other, and the detection means 4 It is preferable that the combination has a length L of the detection groups 40Ba to 40Bc that does not have a common multiple equal to or greater than 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 the combination of the above, it is possible to prevent the detection sensitivity from being lost because the contaminants cannot be detected in the plurality of detection groups 40Ba to 40Bc.

In other words, the detection means 4B has a combination of lengths L of the detection groups 40Ba to 40Bc that does not have a common multiple equal to or greater than the length of the detection means 4B, and a combination of lengths L such that the common multiple is as small as possible. The detection sensitivity can be randomized. Therefore, the detection means 4B can deal with small pollutants or contaminants that cannot be detected by the detection means 4 (see FIG. 2) having a plurality of detection groups 40 having the same length L in the first embodiment. , It is possible to prevent the detection sensitivity of pollutants from being lost. Therefore, the encoder 1B can suppress a decrease in measurement accuracy.

Also in such an embodiment, in addition to being able to exert the same actions and effects as those of (1) to (7) in the first embodiment, the following actions and effects can be obtained.
(10) Since the plurality of detection groups 40Ba to 40Bc have different areas in which the contaminant T can be detected because the total number of the plurality of detection elements 400 is different, the encoder 1B corresponds to the contaminant 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 are the lengths of the detection groups L in the plurality of detection groups 40Ba to 40Bc, where L is the reference for the length of each detection group 40Ba to 40Bc along the X direction. Are different from each other and have no common divisor including 1 and are arranged in a combination of length L of the detection group which is not a common multiple equal to or more than 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 the embodiment]
The present invention is not limited to each of the above-described embodiments, and modifications, improvements, and the like to the extent that the object of the present invention can be achieved are included in the present invention.
For example, in each of the above-described embodiments, the cases where the encoders 1, 1A to 1B are optical encoders and linear encoders have been described, but the encoders may be rotary encoders instead of linear encoders, and optical encoders. Instead, it may be an encoder of another type such as an electromagnetic induction type or a capacitance type. In short, the encoder is not particularly limited in the type of the detector, the detection method, and the like.

In each of the above-described 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, but the extraction unit is not a low-pass filter but a Fourier transform. The spectrum calculated using the above 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 use any method to extract the abnormality determination signal as long as the abnormality determination signal can be extracted.

In each of the above-described embodiments, 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 (four, etc.), but the number of detection elements is the same 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. It may be 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 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. Although different from the plurality of detection elements 400 of 44, the first detection unit 41 and the third detection unit 43 may be the same detection element 400, and the second detection unit 42 and the fourth detection unit 44 may be the same. , The same detection element 400 may be used. In short, if the measurement signal calculation unit can calculate the measurement signal by differentially calculating a certain signal and a signal that is 180 degrees out of phase, the plurality of detection units can detect a plurality of the same detection elements. It may be a department.

In the first embodiment, the measurement signal calculation unit 52 calculates the first measurement signal and the second measurement signal by differentially calculating 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 two-phase signals to calculate the first measurement signal and the second measurement signal, but 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 into the two-phase signal. In short, the measurement signal calculation unit may calculate the measurement signal by 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 a first detection group 40Ba, a second detection group 40Bb, and a third detection group 40Bc, but the first detection group and the second detection group Only the detection group may be provided, or the fourth detection group or the fifth detection group may be provided. In short, the plurality of detection groups may include the plurality of detection elements and are arranged side by side along the measurement direction.
Further, 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 may have different total numbers of the plurality of detection elements and may have different lengths from each other.

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, but the detection element and the detection group may be designed to any size.

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

1,1A to 1B Encoder 2 Scale 3 Light source 4,4A to 4B Detection means 5,5A Calculation means 51,51A Signal detection unit 52, 52A Measurement signal calculation unit 53 Extraction unit 54 Abnormality determination unit 40, 40A to 40B Detection group 41 , 41A-41B 1st detection unit 42, 42A-42B 2nd detection unit 43, 43A-43B 3rd detection unit 44, 44A-44B 4th detection unit

Claims (10)

A detection means that detects a scale having a scale arranged side by side along the measurement direction and a plurality of detection elements arranged side by side along the measurement direction while moving relative to the scale. And an encoder including a calculation means for calculating the relative movement amount between the scale and the detection means based on the signal.
The detection means
It includes a plurality of the detection elements and includes a plurality of detection groups arranged side by side along the measurement direction.
The plurality of detection groups include a plurality of detection units arranged side by side along the measurement direction.
The plurality of detectors are
The predetermined detection element is used as the first detection unit.
When the detection element different from the first detection unit is used as the second detection unit,
The calculation means is
A signal detection unit that detects a signal from each of the first detection unit and the second detection unit, and
A measurement signal calculation unit that calculates a two-phase measurement signal having a phase difference of 90 degrees for calculating a relative movement amount from the signal detected by the signal detection unit, and a measurement signal calculation unit.
An extraction unit that extracts an abnormality determination signal for determining an abnormality of the scale from the measurement signal calculated by the measurement signal calculation unit, and an extraction unit.
It is provided with an abnormality determination unit for determining whether or not there is an abnormality in the scale from the abnormality determination signal.
The plurality of detection elements are arranged side by side 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 other detection elements different from the first detection unit, and is 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 is a plurality of the detection elements arranged at positions 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 also calculates the signal from the third detection unit and the fourth detection unit. Calculate the 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, and then extracts the abnormality determination signal.
The abnormality determination unit is an encoder that determines whether or not there is an abnormality in the scale from the abnormality determination signal. In the encoder according to claim 1,
The measurement signal calculation unit calculates the first measurement signal by differentially calculating the signal from the first detection unit and the signal from the second detection unit, and also calculates the signal from the third detection unit and the second detection unit. 4 An encoder characterized by differentially calculating a signal from a detection unit to calculate a second measurement signal. In the encoder according to claim 1 or 2.
The third detection unit is
The first detection unit and the second detection unit are different from the other detection elements, and the first detection unit is 90 degrees out of phase with the first detection unit.
The fourth detection unit is
The first detection unit, the second detection unit, and the third detection unit are different from each other, and the second detection unit is arranged at a position 90 degrees out of phase with the second detection unit. The encoder is characterized in that the third detection unit is a plurality of the detection elements arranged at positions that are 180 degrees out of phase with each other. In the encoder according to any one of claims 1 to 3.
The first detection unit and the second detection unit have the same number of detection elements.
An encoder characterized in that the third detection unit and the fourth detection unit have the same number of detection elements. A detection means that detects a scale having a scale arranged side by side along the measurement direction and a plurality of detection elements arranged side by side along the measurement direction while moving relative to the scale. And an encoder including a calculation means for calculating the relative movement amount between the scale and the detection means based on the signal.
The detection means
It includes a plurality of the detection elements and includes a plurality of detection groups arranged side by side along the measurement direction.
The plurality of detection groups include a plurality of detection units arranged side by side along the measurement direction.
The plurality of detectors are
The predetermined detection element is used as the first detection unit.
When the detection element different from the first detection unit is used as the second detection unit,
The calculation means is
A signal detection unit that detects a signal from each of the first detection unit and the second detection unit, and
A measurement signal calculation unit that calculates a two-phase measurement signal having a phase difference of 90 degrees for calculating a relative movement amount from the signal detected by the signal detection unit, and a measurement signal calculation unit.
An extraction unit that extracts an abnormality determination signal for determining an abnormality of the scale from the measurement signal calculated by the measurement signal calculation unit, and an extraction unit.
It is provided with an abnormality determination unit for determining whether or not there is an abnormality in the scale from the abnormality determination signal.
The plurality of detection elements are arranged side by side 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 other detection elements different from the first detection unit, and is a plurality of the detection elements arranged at positions out of phase with the first detection unit by 120 degrees.
The third detection unit is a plurality of other detection elements different from the first detection unit and the second detection unit, and is arranged at a position shifted by 120 degrees from the second detection unit. In the case of the above-mentioned detection element of
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 obtains 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 and
The extraction unit extracts an abnormality determination signal from the first measurement signal and the second measurement signal, and then extracts the abnormality determination signal.
The abnormality determination unit is an encoder that determines whether or not there is an abnormality in the scale from the abnormality determination signal. In the encoder according to any one of claims 1 to 5.
The plurality of detectors are
An encoder characterized by having the same number of detection elements. In the encoder according to any one of claims 1 to 6.
The plurality of detection groups are encoders characterized in that the total number of the plurality of detection elements is different from each other. In the encoder according to any one of claims 1 to 7.
The detection means is composed of a combination of a plurality of the detection groups having different lengths along the measurement direction.
The length of each of the plurality of detection groups along the measurement direction is
It is defined so that when a contaminant having a size that reduces the detection sensitivity of the signal by one of the detection groups adheres to the scale, the detection sensitivity of the signal by at least one other detection group does not decrease. Encoder characterized by being. In the encoder according to any one of claims 1 to 8.
An encoder characterized by being an optical encoder including a light source that irradiates the scale with light and a detection means that receives light through the scale and detects a signal. The encoder control method according to any one of claims 1 to 9 .
The detection means
It includes a plurality of the detection elements and includes a plurality of detection groups arranged side by side along the measurement direction.
The plurality of detection groups include a plurality of detection units arranged side by side along the measurement direction.
The plurality of detectors are
The predetermined detection element is used as the first detection unit.
When the detection element different from the first detection unit is used as the second detection unit,
The calculation means is
A signal detection step of detecting a signal 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 in the signal detection step, and a measurement signal calculation step.
An extraction step of extracting an abnormality determination signal for determining an abnormality of the scale from the measurement signal calculated by the measurement signal calculation step, and an extraction step.
A encoder control method comprising: an abnormality determination step of determining whether or not there is an abnormality in the scale from the abnormality determination signal.

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