Encoder device, drive device, stage device, and robot device

Abstract

This encoder device comprises: a first detector that shines light onto a pattern provided along the rotation direction of a rotating shaft that performs rotational movement, detects light from the pattern, and outputs a first detection signal; a second detector that is disposed in a position separated by a predetermined angle along a rotation direction of the rotating shaft with respect to the first detector, shines light onto the pattern, detects light from the pattern, and outputs a second detection signal; and a control circuit that, on the basis of first information relating to an abnormality or a prediction of an abnormality of one of the first detector and the second detector, selects the other of the first detector and the second detector, and calculates rotational position information of the rotating shaft on the basis of the detection signal of the selected detector.

Description

Encoder device, drive device, stage device, and robot device

[0001] The present invention relates to an encoder device, a drive device, a stage device, and a robot device.

[0002] Encoder devices that detect position information such as the rotation angle or rotation speed of an object to be inspected are mounted on various devices such as robot devices. A known conventional encoder device is one that illuminates a pattern with a light-emitting element, receives light from the pattern with a light-receiving element, and is equipped with a backup power supply (see, for example, Patent Document 1). It is desirable to improve the reliability of the detection results of such encoder devices.

[0003] Japanese Patent Application Laid-Open No. 10-073458 Japanese Patent Application Laid-Open No. 2021-076587

[0004] The encoder device of the present invention comprises: a first detector that irradiates light onto a pattern arranged along the rotation direction of a rotating shaft that rotates, detects the light from the pattern, and outputs a first detection signal; a second detector that is arranged at a position a predetermined angle away from the first detector along the rotation direction of the rotating shaft, irradiates light onto the pattern, detects the light from the pattern, and outputs a second detection signal; and a control circuit that selects the other of the first detector and the second detector based on first information regarding an abnormality or prediction of an abnormality in one of the first detector and the second detector, and calculates rotational position information of the rotating shaft based on the detection signal of the selected detector.

[0005] FIG. 1 is a diagram illustrating an example of an encoder device according to the present embodiment; FIG. 2 is a plan view of an encoder device showing an example of the positional relationship between a pattern and a detector according to the present embodiment; FIG. 3 is a functional configuration diagram showing an example of the functional configuration of an encoder control unit according to the present embodiment; FIG. 4 is a flowchart showing an example of a series of operations of an encoder control unit according to the present embodiment; FIG. 5 is a graph showing the relationship between a mechanical angle and an error by a detector according to the present embodiment; FIG. 6 is a graph showing the relationship between a mechanical angle and an error difference by a detector according to the present embodiment; FIG. 7 is a diagram for explaining offset processing in the error direction of a second detector according to the present embodiment; FIG. 8 is a diagram for explaining offset processing in the mechanical angle direction of a second detector according to the present embodiment; FIG. 9 is a diagram for explaining a correction reproduction calculation when an error exists in a read value of a detector according to the present embodiment; FIG. 10 is a diagram for explaining an example of switching when the difference in position information between a first detector and a second detector according to the present embodiment becomes 0; FIG. 11 is a diagram for explaining an example of offsetting position information at the time of switching according to the present embodiment; FIG. 11 is a diagram for explaining an example of correcting the difference in position information between a first detector and a second detector according to the present embodiment; FIG. 12 is a diagram for explaining an example of outputting an average value of position information of a first detector and a second detector according to the present embodiment; FIG. 13 is a functional configuration diagram showing an example of the functional configuration of an encoder control unit when a failure prediction alarm is performed according to the present embodiment; FIG. 14 is a diagram showing a change in the amplitude of a sensor value detected by a light receiving unit in accordance with a change in the LED light intensity of a detector according to the present embodiment. 1 is a diagram showing a change in the amplitude of a sensor value according to a change in the rotation speed of a motor according to the embodiment, a diagram for explaining an LED current control function and a forward current according to the embodiment, and a diagram for explaining contamination of a disc of a detector according to the embodiment.

[0006] [Embodiments] Preferred embodiments of an angle detection device, a drive device, a stage device, and a robot device according to aspects of the present invention will be described in detail below with reference to the accompanying drawings. Note that aspects of the present invention are not limited to these embodiments and include various modifications or improvements. In other words, the components described below include those that a person skilled in the art would easily imagine or that are substantially identical, and the components described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention.

[0007] FIG. 1 is a diagram showing an example of an encoder system ENS (which may also be referred to as an actuator unit or actuator device) according to this embodiment. The encoder system ENS will be described with reference to the diagram. The encoder system ENS includes an encoder device EC, a motor M, a shaft SF, a motor control unit (which may also be referred to as a motor control device or motor control circuit) 32, and a motor drive unit (which may also be referred to as a motor drive device or motor drive circuit) 33. The encoder device EC includes a base 5, a disk 6, a first detector 11A, a second detector 11B, and an encoder control unit (which may also be referred to as an encoder control device or encoder control circuit) 31. The encoder device EC is, for example, an optical encoder. The encoder control unit 31, the motor control unit 32, and the motor drive unit 33 may be collectively referred to as a control device 30. The encoder control unit 31, the motor control unit 32, and the motor drive unit 33 may each be configured as separate boards, circuits, or devices, or may each be integrated into one board, circuit, or device.

[0008] The encoder device EC detects rotational position information (POS, which may also be referred to as position information, rotation information, angle information, angular position information, etc.) of the shaft SF (which may also be referred to as a moving part, moving mechanism, rotating shaft, rotating mechanism, etc.) of the motor M. The shaft SF is, for example, the rotor of the motor M. The shaft SF may also be an operating shaft (output shaft) connected to the load of the motor M. In the same figure, the center of rotation of the shaft SF is illustrated as the rotation axis AX. The control device 30 uses the detected rotational position information to control the rotation of the motor M (e.g., rotational position, rotational speed, etc.). It can also be said that the control device 30 controls the rotation of the shaft SF.

[0009] The encoder device EC is a so-called multi-rotation absolute encoder. The encoder system ENS or the encoder device EC is mounted on, for example, a drive device, a stage device, a robot device, etc. At least a part of the encoder system ENS operates by receiving power from the power supply of the device in which the encoder system ENS or the encoder device EC is mounted. Furthermore, at least a part of the encoder system ENS may operate by receiving power from a battery (not shown) when the power supply of the device in which the encoder system ENS or the encoder device EC is mounted is turned off.

[0010] A disk-shaped base 5 is attached to the shaft SF. The base 5 rotates together with the shaft SF. A disk 6 is coupled to the shaft SF. The disk 6 rotates in conjunction with the shaft SF. The disk 6 may be, for example, an integral component with the base 5. The disk 6 is formed with an incremental scale (INC, which may also be referred to as an incremental pattern, etc.) SI for detecting the rotational position and an absolute scale (ABS, which may also be referred to as an absolute pattern, etc.) SA. The incremental scale SI and the absolute scale SA are both provided along the rotational movement direction of the rotating shaft SF. The incremental scale SI and the absolute scale SA are formed at different radial positions on the disk 6. The incremental scale SI is a slit formed in the disk 6 for detecting the rotation speed of the shaft SF and the relative angle of the shaft SF. The absolute scale SA is a slit formed in the disk 6 for detecting the absolute angle of the shaft SF. In the following description, when the incremental scale SI and the absolute scale SA are referred to without distinction, they may be simply referred to as the pattern (or scale). In this embodiment, the pattern provided on the disk 6 is described as a reflective pattern having reflective portions and non-reflective portions. However, the pattern provided on the disk 6 may also be a transmissive pattern having transmissive portions and light-shielding portions (shielding portions).

[0011] The first detector 11A and the second detector 11B are supported by a support member (not shown). The first detector 11A and the second detector 11B are disposed at positions spaced apart by a predetermined angle along the rotational movement direction of the shaft SF. The first detector 11A and the second detector 11B include a light-emitting unit (not shown) (e.g., a light-emitting diode (LED)) that irradiates the pattern formed on the disc 6 with detection light, and an optical sensor (light-receiving unit). The first detector 11A and the second detector 11B include the optical sensor, thereby detecting light from the pattern formed on the disc 6. It can also be said that the first detector 11A and the second detector 11B detect light from the pattern formed on the disc 6 at different positions. The signal detected by the first detector 11A is referred to as a first detection signal SI1, and the signal detected by the second detector 11B is referred to as a second detection signal SI2. In addition, instead of the example in which the first detector 11A and the second detector 11B each include an optical sensor that receives light from a reflective pattern, they may also be configured to include an optical sensor that receives light from a transmissive pattern.

[0012] In the following description, the light-emitting element included in the first detector 11A may be referred to as the first light-emitting element. The first light-emitting element irradiates light onto a pattern formed on the disk 6. The light-receiving element included in the first detector 11A may be referred to as the first light-receiving element. The first light-receiving element receives light irradiated by the first light-emitting element from the pattern. Similarly, the light-emitting element included in the second detector 11B may be referred to as the second light-emitting element. The second light-emitting element irradiates light onto a pattern formed on the disk 6. The light-receiving element included in the second detector 11B may be referred to as the second light-receiving element. The second light-receiving element receives light irradiated by the second light-emitting element from the pattern.

[0013] Here, the first detector 11A and the second detector 11B may have a complementary relationship. That is, the first detector 11A and the second detector 11B may operate when one of them is inoperable due to a malfunction or the like. That is, the encoder device EC may output either the first detection signal SI1 or the second detection signal SI2. For example, the encoder device EC may preferentially output the first detection signal SI1, which is the detection result of the first detector 11A. The first detector 11A outputs the detected first detection signal SI1 to the control device 30, and the second detector 11B outputs the detected second detection signal SI2 to the control device 30. The control device 30 performs processing according to rotational position information determined based on either one of the detection signals. Note that the control device 30 may perform processing based on both detection signals.

[0014] The control device 30 acquires the first detection signal SI1 and the second detection signal SI2, detects the position of the shaft SF based on the acquired signals, and drives the motor M based on the detected rotational position information. The drive signal for the motor M output by the control device 30 is referred to as drive information DRVI.

[0015] The encoder control unit 31 acquires a first detection signal SI1 from the first detector 11A and a second detection signal SI2 from the second detector 11B. The encoder control unit 31 processes the acquired detection signals to detect the angular position of the shaft SF within one rotation. The encoder control unit 31 also detects an angular position with a first resolution, for example, using the results of detecting light from the absolute scale SA. The encoder control unit 31 also detects an angular position with a second resolution higher than the first resolution by performing an interpolation operation on the angular position with the first resolution using the results of detecting light from the incremental scale IS. The encoder control unit 31 also detects the number of rotations of the shaft SF using the results of detecting light from the incremental scale IS. The encoder control unit 31 outputs information including the detected angular position (which may include the number of rotations) to the motor control unit 32 as encoder information (rotational position information) ES.

[0016] The motor control unit 32 acquires encoder information ES from the encoder control unit 31. The encoder information ES includes rotational position information of the shaft SF. The motor control unit 32 generates control information CS for the motor M based on the acquired rotational position information of the shaft SF. The control information CS includes information about the power supplied to the motor M, etc. The motor control unit 32 outputs the generated control information CS to the motor drive unit 33.

[0017] The motor drive unit 33 acquires the control information CS from the motor control unit 32. Based on the acquired control information CS, the motor drive unit 33 outputs drive information DRVI and controls the power supplied to the motor M, thereby controlling the rotation of the motor M.

[0018] In the following description, among the components of the encoder device EC, devices that include at least a component for detecting rotational position information of the shaft SF may be referred to as angle detection devices, rotational position detection devices, position detection devices, etc.

[0019] 2A and 2B are plan views showing an example of the positional relationship between the pattern and the detectors according to this embodiment. Fig. 2A is a plan view of the motor M as seen in the direction of the rotation axis AX of the shaft SF, and Fig. 2B is an enlarged view of a portion of Fig. 2A. With reference to the figures, an example of the positional relationship between the pattern formed on the disk 6 and the first and second detectors 11A and 11B will be described.

[0020] As shown in the figure, the disk 6 is fixed to the surface of the base 5 at the tip of the shaft SF using bolts 17. In the figure, the radial direction of the circular disk 6 is designated as the R direction, and the rotation direction of the disk 6 is designated as the θ direction. On the surface of the disk 6, a pattern for angle detection including an incremental scale SI and an absolute scale SA is formed concentrically around the center of rotation of the shaft SF.

[0021] Furthermore, the first detector 11A and the second detector 11B are disposed at positions where they can detect light from the pattern in the circumferential direction of the disk 6. In the example shown, the first detector 11A and the second detector 11B are disposed at positions spaced 90 degrees apart from each other in the circumferential direction of the disk 6. However, the positions at which the first detector 11A and the second detector 11B are disposed are not limited to this example, and they may be disposed at any positions.

[0022] As shown in Figure 2(B), for example, the incremental scale SI is a pattern (also referred to as a reflective pattern or reflective type pattern) in which reflective portions and non-reflective portions are alternately arranged at a predetermined period in the circumferential direction (rotation direction, θ direction) of the disk 6. The absolute scale SA is a pattern (also referred to as a reflective pattern or reflective type pattern) in which a large number of reflective portions, each having a width that is an integer multiple of one period of the incremental scale SI, are arranged in a predetermined array in the circumferential direction (rotation direction, θ direction) of the disk 6. The absolute scale SA may have multiple patterns at different positions in the circumferential direction.

[0023] The first detector 11A includes a first absolute sensor 12A to detect the light reception state based on the absolute scale SA, and a first incremental sensor 13A to detect the light reception state based on the incremental scale SI. The second detector 11B includes a second absolute sensor 12B to detect the light reception state based on the absolute scale SA, and a second incremental sensor 13B to detect the light reception state based on the incremental scale SI.

[0024] The first absolute sensor 12A, the first incremental sensor 13A, the second absolute sensor 12B, and the second incremental sensor 13B each include a light-emitting unit (not shown) (for example, a light-emitting diode (LED) or the like) that irradiates detection light onto a pattern formed on the disc 6, and a light-receiving unit (not shown) (for example, a photodiode or the like) that receives light from the pattern. The first absolute sensor 12A and the second absolute sensor 12B may each include a plurality of light-emitting diodes and a plurality of light-receiving units corresponding to the plurality of light-emitting diodes.

[0025] Specifically, the first detector 11A and the second detector 11B are attached to the first support member 51. In manufacturing the encoder device EC, first, components such as the disk 6, the second support member 52, and the first support member 51 to which the first detector 11A and the second detector 11B are attached are manufactured. Next, the disk 6 is attached to the surface of the base 5 with bolts 17. Furthermore, the first support member 51 is attached to the second support member 52 using two bolts 17. At this time, the R-direction positions of the first detector 11A and the second detector 11B are adjusted (this may also be described as positioning, position adjustment, alignment, etc.) so that they match the position of the pattern formed on the disk 6. As an example, while rotating the disk 6 in the θ direction, the first detection signal SI1 and the second detection signal SI2, which are detection signals of the first detector 11A and the second detector 11B, may be monitored, and the attachment positions may be adjusted based on whether the first detection signal SI1 and the second detection signal SI2 are normally output. To make these adjustments, for example, the bolts 17 may be fixed at two locations while adjusting the position of the first support member 51 relative to the second support member 52. This optimizes the reflected light from the pattern, allowing the rotation angle of the disk 6 to be detected with high accuracy and a high signal-to-noise ratio. In the following description, a configuration including the first support member 51 and the second support member 52 may be simply referred to as the support member 50. The above adjustments may be made using the method described in JP 2021-076587 A.

[0026] FIG. 3 is a functional configuration diagram showing an example of the functional configuration of the encoder control unit according to this embodiment. The encoder control unit 31 includes an amplifier circuit 311, an ADC 312, a position information generation unit (position information generation circuit) 313, a position information correction unit (position information correction circuit) 314, an error correction data storage unit (error correction data storage circuit) 315, a calculation unit (calculation circuit) 316, a switching control unit (switching control circuit) 317, and an output unit (output circuit) 318. At least some of these functional units are implemented using, for example, electronic circuits. Furthermore, at least some of the functional units may include internal storage means such as semiconductor memory or a magnetic hard disk drive, as necessary. Furthermore, at least some of the functional units may be implemented using software and a computer having a CPU (Central Processing Unit).

[0027] The amplifier circuits 311 acquire output signals from the detectors. Here, the output signals from the detectors are analog signals. The amplifier circuits 311 amplify the acquired analog signals. An amplifier circuit 311 is provided corresponding to each detector. Specifically, the amplifier circuits 311 include an amplifier circuit 311A ​​that amplifies the output signal of the first absolute sensor 12A, an amplifier circuit 311B that amplifies the output signal of the first incremental sensor 13A, an amplifier circuit 311C that amplifies the output signal of the second absolute sensor 12B, and an amplifier circuit 311D that amplifies the output signal of the second incremental sensor 13B. Each of these amplifier circuits 311 amplifies the voltage value output from each detector and outputs the amplified voltage value to the ADC 312.

[0028] The ADC 312 converts the output signal from the detector amplified by the amplifier circuit 311 into a digital value. In other words, the ADC 312 is an analog-to-digital conversion circuit (A / D converter). An ADC 312 is provided corresponding to each detector. Specifically, the ADCs 312 include an ADC 312A that performs analog-to-digital conversion on the output signal of the first absolute sensor 12A, an ADC 312B that performs analog-to-digital conversion on the output signal of the first incremental sensor 13A, an ADC 312C that performs analog-to-digital conversion on the output signal of the second absolute sensor 12B, and an ADC 312D that performs analog-to-digital conversion on the output signal of the second incremental sensor 13B. Each of these ADCs 312 converts the voltage value output by each amplifier circuit 311 into a digital value and outputs the converted digital value to the position information generation unit 313. The digital value converted by the ADC 312 is preferably 1-bit binary data, but may be a multi-bit digital value.

[0029] The position information generation unit 313 generates rotational position information of the shaft SF based on the sensor value (which may be referred to as data or information) detected by the absolute sensor and the sensor value (which may be referred to as data or information) detected by the incremental sensor. The rotational position information of the shaft SF generated by the position information generation unit 313 includes the rotation angle (absolute angle) of the motor M (or the shaft SF). The rotational position information may also include the rotation speed and rotation direction of the motor M (or the shaft SF). The position information generation unit 313 continuously acquires the sensor value detected by the absolute sensor and the sensor value detected by the incremental sensor, and generates rotational position information of the shaft SF based on changes in the sensor values ​​over time.

[0030] Specifically, a first position information generator 313A is provided corresponding to the first detector 11A, and a second position information generator 313C is provided corresponding to the second detector 11B. The first position information generator 313A generates rotational position information based on the detection result of the first detector 11A, and the second position information generator 313C generates rotational position information based on the detection result of the second detector 11B. The rotational position information based on the detection result of the first detector 11A and the rotational position information based on the detection result of the second detector 11B differ depending on the relative positions of the detectors. For example, as shown in FIG. 2A , if the first detector 11A and the second detector 11B are positioned 90 degrees apart from each other, the rotational position information based on the detection result of the first detector 11A and the rotational position information based on the detection result of the second detector 11B will differ by 90 degrees.

[0031] The first position information generation unit 313A includes a first absolute address processing unit 313A1, a first interpolation processing unit 313A2, and a first synthesis processing unit 313A3. The first absolute address processing unit 313A1 calculates the absolute angle of the first detector 11A based on the results detected by the first absolute sensor 12A. The absolute angle calculated by the first absolute address processing unit 313A1 corresponds to the resolution of the absolute scale SA. The first interpolation processing unit 313A2 calculates the relative angle of the first detector 11A based on the results detected by the first incremental sensor 13A. The calculated relative angle is used for interpolation processing. The first synthesis processing unit 313A3 performs synthesis processing based on the absolute angle calculated by the first absolute address processing unit 313A1 and the relative angle calculated by the first interpolation processing unit 313A2. This synthesis processing generates rotational position information of the first detector 11A. The first position information generation unit 313A may also determine an abnormality (failure) in the first detector 11A. An "abnormality" refers, for example, to an abnormality in the detector's light-emitting unit or light-receiving unit. Abnormalities in the light-emitting unit include, for example, a decrease in light-emitting function due to a malfunction or aging. Abnormalities in the light-receiving unit include, for example, a decrease in light-receiving function due to a malfunction or dirt. This abnormality determination can be made when there is an error in the angle information within one rotation, a decrease in signal amplitude, or an increase in forward current of the light-emitting unit. Note that abnormality determination methods other than those listed above may also be used. The first position information generation unit 313A may, for example, determine an error in the angle information within one rotation or a decrease in signal amplitude. When determining an error in the angle information within one rotation, the first position information generation unit 313A monitors the alignment based on the result detected by the first absolute sensor 12A (e.g., a specific bit) and the result detected by the first incremental sensor 13A (e.g., a specific bit). If the first position information generation unit 313A determines that there is no consistency (the data is different), it determines that there is an "abnormality." If an abnormality occurs in the first detector 11A, the first position information generation unit 313A outputs information indicating that an abnormality has occurred. Note that abnormalities such as an increase in the forward current of the light-emitting unit are determined by an LED current control circuit, which will be described later.

[0032] The second position information generation unit 313C includes a second absolute address processing unit 313C1, a second interpolation processing unit 313C2, and a second synthesis processing unit 313C3. The second absolute address processing unit 313C1 calculates the absolute angle of the second detector 11B based on the results detected by the second absolute sensor 12B. The absolute angle calculated by the second absolute address processing unit 313C1 corresponds to the resolution of the absolute scale SA. The second interpolation processing unit 313C2 calculates the relative angle of the second detector 11B based on the results detected by the second incremental sensor 13B. The calculated relative angle is used for interpolation processing. The second synthesis processing unit 313C3 performs synthesis processing based on the absolute angle calculated by the second absolute address processing unit 313C1 and the relative angle calculated by the second interpolation processing unit 313C2. This synthesis processing generates rotational position information of the second detector 11B. The second position information generating unit 313C may also determine an abnormality (failure) in the second detector 11B. The method for determining an abnormality is the same as that described for the first position information generating unit 313A, and therefore, description thereof will be omitted.

[0033] The position information corrector 314 performs error correction on the rotational position information generated by the position information generator 313. The error correction data is stored in the error correction data storage unit 315. The error correction data stores values ​​corresponding to the mounting angles of the detectors. The error correction data may be collected when the encoder device EC is manufactured. The error correction data may have different values ​​for each detector. The data for correcting the first detector 11A may be stored in the first error correction data storage unit 315A, and the data for correcting the second detector 11B may be stored in the second error correction data storage unit 315C. The position information corrector 314 may also determine an abnormality (failure) in the first detector 11A or the second detector 11B.

[0034] Specifically, a first position information correcting unit 314A is provided corresponding to the first detector 11A, and a second position information correcting unit 314C is provided corresponding to the second detector 11B. The first position information correcting unit 314A corrects the rotational position information of the first detector 11A, and the second position information correcting unit 314C corrects the rotational position information of the second detector 11B. The information after error correction of the rotational position information by these position information correcting units 314 is output to the calculation unit 316.

[0035] The calculation unit 316 calculates rotational position information of the shaft SF based on the first detection signal SI1 detected by the first detector 11A and the second detection signal SI2 detected by the second detector 11B. The first detector 11A and the second detector 11B detect the rotational position information by illuminating a pattern with a light-emitting element such as a light-emitting diode and detecting the presence or absence of slits formed in the pattern. It is known that light-emitting diodes have a limited lifespan. The output value of a light-emitting diode decreases over time and may eventually fall below a predetermined threshold, resulting in a malfunction. In other words, the detection value of either the first detector 11A or the second detector 11B may be abnormal due to a decrease in the output of the light-emitting diode. The calculation unit 316 references the rotational position information of each of the first detector 11A and the second detector 11B and calculates the rotational position information of the shaft SF based on the detection result of the normal detector. It can also be said that the calculation unit 316 determines whether to detect the rotational position information based on the detection result of the first detector 11A or the second detector 11B. If both the first detector 11A and the second detector 11B are normal, the calculation unit 316 may determine the rotational position information of the shaft SF based on the results detected by either one of the detectors (for example, the result of the first detector 11A may be given priority). If both the first detector 11A and the second detector 11B are normal, the calculation unit 316 may determine the rotational position information of the shaft SF based on the results detected by both detectors. The calculation unit 316 may also determine an abnormality (failure) in the first detector 11A or the second detector 11B.

[0036] The switching control unit 317 has a function of switching (selecting) the output to output rotational position information calculated based on the detection signal output from a detector in which no abnormality (failure) has occurred (or information regarding "abnormality prediction (abnormality prediction, abnormality prediction, failure prediction, failure prediction, failure prediction)" based on the LED current control circuit or the like described below has not been output) (i.e., a normal detector). In other words, the switching control unit 317 has a function of excluding information from a detector in which information regarding an abnormality (failure) or abnormality prediction has been output, and outputting information from a detector in which information regarding an abnormality (failure) or abnormality prediction has been output. The rotational position information is output to the motor control unit 32 by the output unit 318. Furthermore, when an abnormality (failure) has occurred in either the first detector 11A or the second detector 11B, the output unit 318 may output information indicating the occurrence of the abnormality (failure) to the motor control unit 32.

[0037] 4 is a flowchart showing an example of a series of operations of the encoder control unit according to this embodiment. With reference to this drawing, an example of a series of operations of the encoder control unit 31 will be described.

[0038] First, in step S11, the first detector 11A detects a sensor value, and in step S21, the second detector 11B detects a sensor value. Next, in step S13, signal processing of the sensor value detected by the first detector 11A is performed, and in step S23, signal processing of the sensor value detected by the second detector 11B is performed. Here, the signal processing performed in steps S13 and S23 includes, for example, the above-mentioned signal amplification processing, analog-to-digital value conversion processing, and abnormality determination. If an abnormality is detected in steps S13 and S23, information about the abnormality is output to the switching control unit 317. Furthermore, in steps S13 and S23, information about "abnormality prediction (abnormality prediction, abnormality forecast, failure prediction, failure forecast, failure prediction)" based on an LED current control circuit or the like, which will be described later, may be output.

[0039] Next, in step S15, rotational position information is generated based on the sensor values ​​detected by the first detector 11A, and in step S25, rotational position information is generated based on the sensor values ​​detected by the second detector 11B. Furthermore, in step S31, a self-accuracy correction process is performed on the generated rotational position information. Pre-measured error correction data may be used for this self-accuracy correction process. Based on the rotational position information after the self-accuracy correction process, it is determined whether or not there is an abnormality in the difference between the rotational position information based on the sensor values ​​detected by the first detector 11A and the rotational position information based on the sensor values ​​detected by the second detector 11B. If it is determined that there is an abnormality (if an abnormal value is detected), information regarding the abnormality is output to the switching control unit 317. If no abnormality is detected, an averaging process may be performed to calculate an average value of the rotational position information based on the sensor values ​​detected by the first detector 11A and the rotational position information based on the sensor values ​​detected by the second detector 11B.

[0040] Next, in step S33, the switching control unit 317 performs a process of switching (selecting) the output value to either rotational position information based on the sensor value detected by the first detector 11A or rotational position information based on the sensor value detected by the second detector 11B. If either the first detector 11A or the second detector 11B is abnormal, the switching control unit 317 switches (selects) the normal value to be the output value. Note that if both the first detector 11A and the second detector 11B are normal, the switching control unit 317 may use the average value of the rotational position information based on the sensor value detected by the first detector 11A and the rotational position information based on the sensor value detected by the second detector 11B as the output value.

[0041] In step S35, the output unit 318 outputs rotational position information based on the detector specified by the switching control unit 317. Furthermore, if an abnormality occurs in any of the detectors, the output unit 318 outputs information about the detector in which the abnormality occurs.

[0042] Next, an example of the rotational position information switching process (selection process) performed by the switching control unit 317 will be described with reference to FIGS. 5 to 9 . The examples in FIGS. 5 to 9 illustrate a case where the mechanical angle and error measured by the detector are known in advance. The detection results from the detector may contain errors. The error is the difference between the actual output value and the ideal output value based on the absolute position. Such errors may occur due to variations in the installation of the encoder device EC during manufacturing or distortion of the disk 6. When attempting to switch the rotational position information, if the errors measured by the first detector 11A and the second detector 11B differ from each other, a sudden change in speed or acceleration may be erroneously recognized. Furthermore, if control is performed based on erroneously recognized information, speed errors or the like may occur. Therefore, the switching control unit 317 performs processing to reduce the effects of errors when switching the rotational position information.

[0043] FIG. 5 is a graph showing the relationship between mechanical angle and error measured by the detector according to this embodiment. The horizontal axis of the graph represents the mechanical angle, and the vertical axis represents the error at that mechanical angle. In the graph, line W11 represents the error for each mechanical angle for the sensor value detected by the first detector 11A. Also, line W12 represents the error for each mechanical angle for the sensor value detected by the second detector 11B. Here, line W11 and line W12 intersect at mechanical angles A11 and A12. After determining whether to switch, the switching control unit 317 switches the output at the point where these error values ​​intersect (the point where they are equal). In other words, the switching control unit 317 can be said to switch the angle information to be output based on the angle information calculated based on the first detection signal SI1 and the angle information calculated based on the second detection signal SI2, at an angle where the angular error between the two is approximately the same. The range of angles in which the angular errors of both are approximately the same value may be a range in which the control device 30 does not mistakenly recognize a sudden change in speed or acceleration. The switching control unit 317 can prevent a sudden change in speed or acceleration by switching the output at a point in time when the difference in error is approximately 0. The error according to the mechanical angle may be measured when the encoder information ES is manufactured, and the measured value may be stored in a storage unit (not shown).

[0044] FIG. 6 is a graph showing the relationship between the mechanical angle and the error difference measured by the detector according to this embodiment. The horizontal axis of the graph represents the mechanical angle, and the vertical axis represents the error difference at that mechanical angle. The error difference is the difference between line W11 and line W12 shown in FIG. 5. As described above, the error difference is zero at points where the mechanical angle is A11 and A12. The switching control unit 317 switches the output at such points. Note that if the switching control unit 317 switches at a point where the error is AR1, the correction value will change abruptly, causing abrupt changes in the speed and acceleration, which is not desirable.

[0045] FIG. 7 is a diagram illustrating the offset process for the error of the second detector according to this embodiment. The horizontal axis of the figure represents the mechanical angle, and the vertical axis represents the error at that mechanical angle. In the figure, the error for each mechanical angle of the sensor value detected by the first detector 11A is indicated by line W21. Also, in the figure, the error for each mechanical angle of the sensor value detected by the second detector 11B is indicated by line W22. The switching control unit 317 controls the error by offsetting the error of the second detector 11B so that the difference in error becomes nearly zero. The range in which the difference in error becomes nearly zero may be any range in which the control device 30 does not erroneously recognize a sudden change in speed or acceleration. In other words, the switching control unit 317 performs switching based on the angle information calculated based on the first detection signal SI1 and the angle information calculated based on the second detection signal SI2, offsetting the difference in angular error between the two to eliminate the difference. By offsetting the difference in angular error in this manner, switching can be performed at any time without a fixed timing.

[0046] FIG. 8 is a diagram illustrating offset processing in the mechanical angle direction of the second detector according to this embodiment. The horizontal axis of the figure represents the mechanical angle, and the vertical axis represents the error at that mechanical angle. In the figure, the error for each mechanical angle of the sensor value detected by the first detector 11A is indicated by line W31. Also, in the figure, the error for each mechanical angle of the sensor value detected by the second detector 11B is indicated by line W32. The switching control unit 317 controls the error of the second detector 11B to be approximately zero by pseudo-offsetting the error by a predetermined angle. The range in which the error difference is approximately zero may be any range in which the control device 30 does not erroneously recognize a sudden change in speed or acceleration. In this embodiment, as shown in FIG. 2, the first detector 11A and the second detector 11B are positioned 90 degrees apart from each other. Therefore, the switching control unit 317 controls the error difference to be approximately zero by pseudo-offsetting the error of the second detector 11B by 90 degrees. In other words, the switching control unit 317 rewrites the origin position of the angle information calculated based on the second detection signal SI2 to match the origin position of the angle information calculated based on the first detection signal SI1. Note that the offset process may be performed before or after the difference detection in the switching control unit 317.

[0047] FIG. 9 is a diagram illustrating a correction reproduction calculation when an error occurs in the detector read value according to this embodiment. The horizontal axis of the figure represents the mechanical angle, and the vertical axis represents the error at that mechanical angle. In the figure, the error for each mechanical angle of the sensor value detected by the first detector 11A is shown as an "error curve W41." The error for each mechanical angle of the sensor value detected by the second detector 11B is shown as an "error curve W42." The figure also shows a correction curve based on the "error curve W41" and the "error curve W42" as a "correction curve." The "correction curve" may be an average of the "error curve W41" and the "error curve W42." The switching control unit 317 may output, as rotational position information, an average value of the angle information calculated based on the first detection signal SI1 and the angle information calculated based on the second detection signal SI2.

[0048] 9, the curve after correction of the "error curve W41" is shown as "corrected error W41," and the curve after correction of the "error curve W42" is shown as "corrected error W42." The switching control unit 317 may perform error correction in advance in this manner. Alternatively, the switching control unit 317 may output an average value after error correction as rotational position information.

[0049] Even if the mechanical angle and error of the detector are not known in advance, it is possible to appropriately switch the rotational position information. For example, if the detector error is not known in advance, the method described in paragraph

[0073] and subsequent paragraphs of JP 2021-076587 A may be adopted, and the position information of each detector may be offset instead of the error of each detector.

[0050] An example of the switching process (selection process) of the rotational position information by the switching control unit 317 will be described with reference to Fig. 10 to Fig. 13. The examples of Fig. 10 to Fig. 13 show a case where the mechanical angle and error from the detector are not known in advance.

[0051] 10 shows an example of switching when the difference in position information between the first detector 11A and the second detector 11B becomes zero. The horizontal axis of the figure represents the position information of the first detector 11A, and the vertical axis represents the difference in position information between the first detector 11A and the second detector 11B. As shown in FIG. 10, at points A31, A32, and A33, the difference in position information between the first detector 11A and the second detector 11B becomes zero. The switching control unit 317 switches the output at such points.

[0052] FIG. 11 shows an example of offsetting position information during switching. The horizontal axis of the figure represents the position information of the first detector 11A, and the vertical axis represents the difference between the position information of the first detector 11A and the second detector 11B. As shown in FIG. 11 , for example, when switching from the first detector 11A to the second detector 11B at point A41, there is a difference of A42, so the switching control unit 317 offsets the position information of the first detector 11A by A42 to obtain the position information of the second detector 11B. In this way, the switching control unit 317 switches the position information by offsetting the position information so that the difference between the position information of the first detector 11A and the second detector 11B becomes zero.

[0053] FIG. 12 shows an example of correcting the difference in position information between the first detector 11A and the second detector 11B. The horizontal axis in the figure represents the position information of the first detector 11A, and the vertical axis represents the difference in position information between the first detector 11A and the second detector 11B. For example, one or both of the calculation unit 316 and the switching control unit 317 acquires the difference in position information between the first detector 11A and the second detector 11B at each position of the first detector 11A and corrects the difference in position information between the first detector 11A and the second detector 11B to eliminate the difference. This correction can be performed at any time, such as during initial adjustment, at startup, or after each rotation. After this correction, the switching control unit 317 switches the position information.

[0054] FIG. 13 shows an example of outputting the average value of the position information of the first detector 11A and the second detector 11B. The horizontal axis of the figure represents the output position information, and the vertical axis represents the difference between the position information. In FIG. 13, W51 represents the difference between the position information of the first detector 11A and the second detector 11B, and W52 represents the difference between the average value of the position information of the first detector 11A and the second detector 11B and the position information of the second detector 11B. For example, one or both of the calculation unit 316 and the switching control unit 317 output the average value of the position information of the first detector 11A and the second detector 11B. If an alarm (an abnormality / failure, or an expectation / prediction / forecast of an abnormality / failure) is issued, the switching control unit 317 switches to the position information of the detector for which no alarm is issued. In this case, the difference is smaller than when switching from the position information of the first detector 11A to the position information of the second detector 11B.

[0055] Next, an example of switching when the speed is high will be described without using any illustrations. The position information of the first detector 11A or the second detector 11B is output to the control device 30 at regular intervals. If the switching control unit 317 switches the position information of the first detector 11A or the second detector 11B when the shaft SF is stopped, a large difference in the position information may result in a speed error. On the other hand, if the switching control unit 317 switches the position information of the first detector 11A or the second detector 11B when the shaft SF is moving, the rate of change in speed will be smaller than when the shaft SF is stopped. Therefore, the switching control unit 317 may switch the position information when the rotation speed of the shaft SF is above a certain level. In this case, for example, the switching speed is stored in a memory (not shown), and when one detector issues an alarm (an abnormality / failure, or an abnormality / failure prediction / prediction), the detector switches to another detector that does not issue an alarm at that speed.

[0056] Next, the failure prediction alarm function will be described with reference to FIGS. 14 to 18 . Here, the light-emitting diodes included in the first detector 11A and the second detector 11B lose light output over time. The failure prediction alarm function outputs an alarm (alarm) to predict a failure (failure prediction, failure prediction, abnormality prediction, abnormality prediction) before the light output becomes unusable. The failure prediction alarm function monitors each data item of the first detector 11A and the second detector 11B. Examples of data items to be monitored include LED forward current, current control signal, amplitude, and rotational position information. If any of these monitored data items exceeds a set threshold or range, an alarm is output. In another embodiment, an alarm may be output if any of these monitored data items drops by a certain value or more from its initial value.

[0057] In this embodiment, multiple detectors including a first detector 11A and a second detector 11B are used. These multiple detectors do not need to be always on at the same time. Even if they are turned on at the same time, it is sufficient for one of the detectors to detect rotational position information. Therefore, if they are always turned on at the same time, one of the detectors will perform unnecessary detection. Therefore, in this embodiment, if all of the multiple detectors are normal (have not reached the end of their life), these detectors may be operated exclusively. Furthermore, the other detector does not need to be completely off and may be driven intermittently, for example.

[0058] 14 is a functional configuration diagram showing an example of the functional configuration of the encoder control unit when a failure prediction alarm is issued according to this embodiment. With reference to the same figure, an example of the functional unit when a failure prediction alarm is issued will be described. In the illustrated example, components similar to those of the encoder control unit 31 described above are given the same reference numerals, and descriptions thereof may be omitted.

[0059] In the figure, a light-emitting circuit 41A is shown as a functional unit that controls the light-emitting circuit of the first detector 11A. A light-receiving circuit 42A is shown as a functional unit that controls the light-receiving circuit of the first detector 11A. A light-emitting circuit 41C is shown as a functional unit that controls the light-emitting circuit of the second detector 11B. A light-receiving circuit 42C is shown as a functional unit that controls the light-receiving circuit of the second detector 11B. A processing unit 319 is also shown as a control unit that comprehensively controls the failure prediction alarm function. Each of these functional units may be provided in, for example, the encoder control unit 31.

[0060] The first detector 11A includes a light-emitting diode 11A1 and a light-receiving sensor 11A2. The second detector 11B includes a light-emitting diode 11B1 and a light-receiving sensor 11B2. These pairs of light-emitting diodes and light-receiving sensors may form an absolute sensor or an incremental sensor. The figure illustrates an example in which the first detector 11A and the second detector 11B each include one pair. If the first detector 11A and the second detector 11B each include multiple pairs, each pair may be provided with a corresponding light-emitting circuit and light-receiving circuit. The light-emitting diode 11A1 is a specific example of the first light-emitting element described above, and the light-receiving sensor 11A2 is a specific example of the first light-receiving element described above. The light-emitting diode 11B1 is a specific example of the second light-emitting element described above, and the light-receiving sensor 11B2 is a specific example of the second light-receiving element described above.

[0061] The light receiving circuit 42A includes an amplifier circuit 311A, an ADC 312A, an amplifier circuit 311B, and an ADC 312B. The light receiving circuit 42A amplifies the intensity of light received by the light receiving sensor 11A2, converts it into a digital value, and provides it to the processing unit 319. The light receiving circuit 42C includes an amplifier circuit 311C, an ADC 312C, an amplifier circuit 311D, and an ADC 312D. The light receiving circuit 42C amplifies the intensity of light received by the light receiving sensor 11B2, converts it into a digital value, and provides it to the processing unit 319.

[0062] The light-emitting circuit 41A includes an LED current control circuit 411A, an LED drive circuit 412A, an ADC 413A, and an ADC 414A. The LED current control circuit 411A acquires an analog value from the light-receiving circuit 42A and controls the current value supplied to the light-emitting diode 11A1 based on the acquired value. The LED current control circuit 411A controls the current value supplied to the light-emitting diode 11A1 by outputting a current control signal to the LED drive circuit 412A. The current control signal may be a signal that controls the LED drive current according to a voltage value. The LED drive circuit 412A supplies a drive current to the light-emitting diode 11A1 according to the current control signal output by the LED current control circuit 411A. The LED drive circuit 412A outputs an LED forward current value to the ADC 413A according to the drive current supplied. In the following description, the LED drive circuit 412A may be referred to as a first drive unit. The first drive unit controls the intensity of light emitted by the LED 11A1. The ADC 413A converts the value of the LED forward current into a digital value and provides it to the processing unit 319. The ADC 414A converts the value of the current control signal output by the LED current control circuit 411A into a digital value and provides it to the processing unit 319.

[0063] The light-emitting circuit 41C includes an LED current control circuit 411C, an LED drive circuit 412C, an ADC 413C, and an ADC 414C. The LED current control circuit 411C acquires an analog value from the light-receiving circuit 42C and controls the current value supplied to the light-emitting diode 11B1 based on the acquired value. The LED current control circuit 411C controls the current value supplied to the light-emitting diode 11B1 by outputting a current control signal to the LED drive circuit 412C. The current control signal may be a signal that controls the LED drive current according to a voltage value. The LED drive circuit 412C supplies a drive current to the light-emitting diode 11B1 according to the current control signal output by the LED current control circuit 411C. The LED drive circuit 412C outputs an LED forward current value to the ADC 413C according to the drive current supplied. In the following description, the LED drive circuit 412C may be referred to as a second drive unit. The second drive unit controls the intensity of light emitted by the LED 11B1. The ADC 413C converts the value of the LED forward current into a digital value and provides it to the processing unit 319. The ADC 414D converts the value of the current control signal output by the LED current control circuit 411C into a digital value and provides it to the processing unit 319.

[0064] The processing unit 319 acquires information from the light-emitting circuit 41A, the light-receiving circuit 42A, the light-emitting circuit 41C, and the light-receiving circuit 42C. The processing unit 319 performs failure prediction alarm processing based on the acquired information. Specifically, the processing unit 319 may determine whether a failure (abnormality) has occurred in the detector by comparing the acquired value with a predetermined threshold value. Specifically, the processing unit 319 determines whether the first detector 11A is approaching a failure (abnormal) state based on the amount of light received by the light-receiving sensor 11A2, and determines whether the second detector 11B is approaching a failure state based on the amount of light received by the light-receiving sensor 11B2. If the processing unit 319 determines that either the first detector 11A or the second detector 11B is approaching a failure state, it outputs failure prediction information (which may also be described as failure prediction information, failure prediction information, abnormality prediction information, anomaly prediction information, or the like) to, for example, the motor control unit 32.

[0065] FIG. 15 shows the change in the amplitude of the sensor value detected by the light receiving unit in accordance with changes in the LED light intensity of the detector according to this embodiment. In this figure, the horizontal axis represents time, showing the change in the LED light intensity over time and the change in the amplitude of the sensor value associated with changes in the LED light intensity. As shown, the LED light intensity decreases over time. Note that the graph shows the change when the LED continues to output a constant light intensity, and the degree of change varies depending on the light intensity. When the LED light intensity is constant, the amplitude of the sensor value also remains constant. However, as the light intensity decreases, the amplitude of the sensor value also decreases. As the amplitude of the sensor value decreases, it eventually reaches an undetectable level. When the amplitude of the sensor value reaches an undetectable level, rotational position information cannot be generated or an error occurs. According to this embodiment, a predetermined threshold is set to detect the decrease in the LED light intensity before it reaches an undetectable level, and a failure warning alarm is issued. Note that the predetermined threshold may be defined as an absolute voltage value or may vary based on the environment, etc.

[0066] The predetermined threshold may also be based on whether the amplitude has changed by a certain value or more from the initial value. In this case, the initial value of the amplitude in the first detector 11A may be different from the initial value of the amplitude in the second detector 11B. Therefore, it is preferable that the thresholds of the first detector 11A and the second detector 11B are different from each other. In other words, it is preferable that the threshold for determining whether the first detector 11A is approaching a fault state and the threshold for determining whether the second detector 11B is approaching a fault state are different from each other.

[0067] FIG. 16 is a diagram showing the change in the amplitude of the sensor value with changes in the rotation speed of the motor according to this embodiment. The horizontal axis represents the rotation speed of the motor M, and the vertical axis represents the amplitude of the sensor value, showing the change in the amplitude of the sensor value for each rotation speed. As shown in the figure, the amplitude of the sensor value decreases as the rotation speed of the motor M increases. Therefore, simply setting a threshold value for the amplitude of the sensor value may result in a false detection that the LED light intensity has decreased due to an increase in rotation speed. FIG. 16(A) shows an example of a case in which the amplitude of the sensor value decreases as the rotation speed increases, falling below a predetermined threshold, resulting in a false detection that the LED light intensity has decreased. Here, the reason the amplitude fell below the predetermined threshold is due to an increase in rotation speed, not due to end of life. Therefore, issuing a failure prediction alarm in such a case would result in a false detection. FIG. 16(B) shows the difference in the change in the amplitude of the sensor value with changes in rotation speed between a normal LED and an LED that has deteriorated due to long-term use.

[0068] To prevent such problems, according to this embodiment, for example, the failure prediction alarm process may be performed at low speeds and not at high speeds. Furthermore, according to other embodiments, thresholds may be set for different speeds. That is, the threshold for determining whether the first detector 11A is approaching a failure state and the threshold for determining whether the second detector 11B is approaching a failure state may both be different depending on the rotation speed of the shaft SF. The speed-specific thresholds may be set based on, for example, changes in the amplitude of the sensor values ​​at different speeds. Furthermore, the incremental and absolute amplitudes of the first detector 11A and the second detector 11B may be compared, and a threshold may be set for the difference between the first detector 11A and the second detector 11B.

[0069] FIG. 17 is a diagram illustrating the LED current control function and forward current according to this embodiment. This diagram is a modified version of the graph shown in FIG. 15. FIG. 17 also shows the change in the LED forward current over time. As shown in the diagram, even during periods when the light intensity remains constant, the LED continues to deteriorate, and control to increase the forward current maintains the light intensity constant. In other words, without such forward current control, the light intensity decreases. Here, the forward current has an upper limit, and as shown in the diagram, the forward current value cannot be increased beyond the forward current control limit. Therefore, the light intensity begins to decrease once the forward current control limit is exceeded. According to this embodiment, a threshold may be set at or before the forward current reaches its maximum value, and a failure prediction alarm may be output when the forward current value exceeds the threshold. This configuration allows a failure prediction alarm to be issued before the LED light intensity begins to decrease.

[0070] The alarm associated with the decrease in the LED light intensity and the alarm associated with the increase in forward current may be combined to output a failure prediction alarm. Specifically, the processing unit 319 may determine that the first detector 11A is approaching a failure state when the intensity of light emitted by the first light-emitting element is equal to or greater than a predetermined threshold and the amount of light received by the first light-receiving element is equal to or less than a predetermined value. The processing unit 319 may also determine that the second detector 11B is approaching a failure state when the intensity of light emitted by the second light-emitting element is equal to or greater than a predetermined threshold and the amount of light received by the second light-receiving element is equal to or less than a predetermined value.

[0071] The light intensity of the LED also varies with temperature. Specifically, the light intensity of the LED decreases at high temperatures. That is, at high temperatures, the forward current increases to maintain a constant light intensity. Therefore, as the temperature increases, the forward current increases and exceeds the forward current threshold, which may result in a false detection of a fault. To prevent such false detection, according to this embodiment, a failure prediction alarm process may be performed according to temperature. Specifically, the failure prediction alarm process may be performed at room temperature or low temperature, but not at high temperature. In other embodiments, thresholds may be set for each temperature. The temperature-specific thresholds may be set based on, for example, changes in the amplitude of the sensor value at each temperature. More specifically, the encoder device EC further includes a temperature information acquisition unit (not shown) that acquires temperature information around the first detector 11A and the second detector 11B, thereby performing temperature-dependent control. In this case, the threshold for determining whether the first detector 11A is approaching a fault state and the threshold for determining whether the second detector 11B is approaching a fault state may both be different depending on the temperature information acquired by the temperature information acquisition unit. In another embodiment, a threshold value may be set for the difference in forward current between the LEDs. In another embodiment, a threshold value may be set for the current control signal. This is because when the current control signal reaches its maximum, no further forward current can flow. As a result, there is a problem in that the light intensity cannot be maintained constant.

[0072] FIG. 18 is a diagram illustrating the contamination of the disk of the detector according to this embodiment. The diagram shows the amplitude and forward current of the sensor value for each mechanical angle. If contamination adheres to a portion of the disk 6, the amount of LED light reaching the light receiving sensor is reduced in the contaminated area. Therefore, differences may occur in the amplitude, forward current (413A_LED), and current control signal (414A_LED) during one revolution of the disk 6. FIG. 18(A) shows an example in which the forward current value is increased in the contaminated area to maintain a constant amplitude. FIG. 18(B) shows an example in which the sensor value decreases in the contaminated area by maintaining a constant forward current.

[0073] In this way, an increase in forward current or a decrease in amplitude in a dirty area may result in a false detection that the LED has failed. According to this embodiment, to prevent such false detection, different thresholds may be set for each mechanical angle. Specifically, the forward current threshold may be set higher in a dirty area than in a non-dirty area. Furthermore, the amplitude threshold may be set lower in a dirty area than in a non-dirty area. Furthermore, a failure determination may not be performed in a dirty area.

[0074] Furthermore, the influence of contamination on the disk can be avoided by switching the detector for calculating rotational position information at locations where contamination exists (i.e., locations where the amplitude decreases or the forward current and current control signal increase). According to another embodiment, a threshold value may be set for the difference in amplitude, forward current, or current control signal within one rotation of the disk, and an alarm may be output.

[0075] Summary of the Embodiment According to the above-described embodiment, the angle detection device includes a first detector 11A that detects light from a pattern arranged along the movement direction of a rotating shaft SF (moving part) and outputs a first detection signal SI1; a second detector 11B that is positioned at a predetermined angle away from the first detector 11A along the movement direction of the moving part and detects light from the pattern and outputs a second detection signal SI2; a calculation unit 316 that calculates rotational position information of the moving part from the first detection signal SI1 and the second detection signal SI2; and a support member 50 that supports the first detector 11A and the second detector 11B. The angle detection device outputs either the first detection signal SI1 or the second detection signal SI2, and prioritizes outputting the first detection signal SI1. When an abnormality occurs in either the first detector 11A or the second detector 11B, the angle detection device has a function of outputting information indicating the abnormality and switching the output to output rotational position information calculated based on the detection signal output from the detector not experiencing the abnormality. Therefore, according to this embodiment, even if an abnormality occurs in one of the detectors, normal operation can be continued using the other detector, and therefore, according to this embodiment, it is possible to provide an encoder system ENS or encoder device EC with highly reliable detection results.

[0076] Furthermore, according to the embodiment described above, the angle detection device switches the angle information to be output based on the angle information calculated based on the first detection signal SI1 and the angle information calculated based on the second detection signal SI2, at an angle where the angular error between the two is approximately the same value. Here, if there is a difference between the angular errors of the first detector 11A and the second detector 11B, an error difference will occur during switching. If the error difference during switching is large, the speed or acceleration may be recognized as having increased suddenly, and speed errors or the like may occur. According to this embodiment, the angle information to be output is switched at an angle where the angular errors of the first detector 11A and the second detector 11B are approximately the same value, thereby reducing the error difference during switching. Therefore, according to this embodiment, the speed or acceleration will not be recognized as having increased suddenly, and the possibility of speed errors or the like occurring can be reduced.

[0077] Furthermore, according to the embodiment described above, the angle detection device offsets the difference in angular error between angle information calculated based on the first detection signal SI1 and angle information calculated based on the second detection signal SI2, thereby eliminating the difference. That is, according to this embodiment, the error difference is offset so that it becomes zero at the time of switching. Specifically, the angle detection device stores error difference information at positions at each mechanical angle in a storage unit (not shown) in advance and offsets the difference amount at the time of switching. Note that the difference between each position may be calculated linearly or by other methods. Therefore, according to this embodiment, the error difference at the time of switching can be reduced. Therefore, according to this embodiment, the speed or acceleration is not recognized as having increased suddenly, and the possibility of a speed error or the like occurring can be reduced.

[0078] Furthermore, according to the embodiment described above, the angle detection device rewrites the origin position of the angle information calculated based on the second detection signal SI2 to match the origin position of the angle information calculated based on the first detection signal SI1. That is, according to this embodiment, an offset is performed so that the difference in error becomes zero when switching. Therefore, according to this embodiment, the difference in error when switching can be reduced. Therefore, according to this embodiment, the speed or acceleration is not recognized as having increased suddenly, and the possibility of a speed error or the like occurring can be reduced.

[0079] Furthermore, according to the embodiment described above, the angle detection device outputs the average value of the angle information calculated based on the first detection signal SI1 and the angle information calculated based on the second detection signal SI2. That is, the angle detection device outputs the average value of the rotational position information detected by the first detector 11A and the rotational position information detected by the second detector 11B as the rotational position information of the shaft SF. Therefore, according to this embodiment, it is possible to output highly accurate rotational position information based on two detectors. Note that, if one of the detectors fails, a switching process may be performed to output based on one of the detectors.

[0080] Furthermore, according to the embodiment described above, the first detector 11A includes a first light-emitting element that irradiates the pattern with light and a first light-receiving element that receives light irradiated by the first light-emitting element and from the pattern. The second detector 11B includes a second light-emitting element that irradiates the pattern with light and a second light-receiving element that receives light irradiated by the second light-emitting element and from the pattern. The angle detection device further includes a processing unit 319, which determines whether the first detector 11A is approaching a failure state based on the amount of light received by the first light-receiving element, and determines whether the second detector 11B is approaching a failure state based on the amount of light received by the second light-receiving element. The processing unit 319 also outputs failure prediction information when it is determined that either detector is approaching a failure state. In other words, according to this embodiment, the device has a failure prediction alarm function. Specifically, according to this embodiment, it is possible to detect that a detector is approaching a failure state and output the detected information before the detector completely fails. Therefore, according to this embodiment, it is possible to prevent abnormal values ​​from being output due to a failure.

[0081] Furthermore, according to the embodiment described above, the threshold value for determining whether the first detector 11A is approaching a failure state and the threshold value for determining whether the second detector 11B is approaching a failure state are different from each other. Therefore, according to the embodiment, it is possible to accurately determine whether each detector is approaching a failure state.

[0082] Furthermore, according to the embodiment described above, the threshold value for determining whether the first detector 11A is approaching a failure state and the threshold value for determining whether the second detector 11B is approaching a failure state both differ depending on the rotation speed of the shaft SF. Therefore, according to this embodiment, even when the rotation speed increases and the amplitude of the sensor value decreases, it is possible to prevent the detectors from being erroneously detected as having failed.

[0083] According to the above-described embodiment, the angle detection device further includes an LED drive circuit 412A (first drive unit) that controls the intensity of light emitted by the first light-emitting element and an LED drive circuit 412C (second drive unit) that controls the intensity of light emitted by the second light-emitting element. The LED drive circuit 412A controls the intensity of light emitted by the first light-emitting element in accordance with the amount of light received by the first light-receiving element, and the LED drive circuit 412C controls the intensity of light emitted by the second light-emitting element in accordance with the amount of light received by the second light-receiving element. The processing unit 319 determines that the first detector 11A is approaching a fault if the intensity of light emitted by the first light-emitting element is equal to or greater than a predetermined threshold and the amount of light received by the first light-receiving element is equal to or less than a predetermined value. The processing unit 319 determines that the second detector 11B is approaching a fault if the intensity of light emitted by the second light-emitting element is equal to or greater than a predetermined threshold and the amount of light received by the second light-receiving element is equal to or less than a predetermined value. That is, according to this embodiment, the forward current of the light-emitting diode is first increased to maintain the amplitude of the sensor value, and when the forward current reaches a maximum and the amplitude begins to decrease, it is determined that the sensor is approaching a fault state. Therefore, according to this embodiment, it is possible to use the light-emitting diode for a long period of time.

[0084] Furthermore, according to the embodiment described above, the device further includes a temperature information acquisition unit that acquires temperature information around the first detector 11A and the second detector 11B. The threshold value for determining whether the first detector 11A is approaching a fault state and the threshold value for determining whether the second detector 11B is approaching a fault state both differ depending on the temperature information acquired by the temperature information acquisition unit. Therefore, according to this embodiment, even if the forward current changes due to temperature fluctuations, it is possible to prevent the detectors from being erroneously detected as having failed.

[0085] The encoder system ENS or encoder device EC described above may be used in a drive device MTR (not shown). This drive device MTR is a motor device including an electric motor. The drive device MTR includes a shaft SF, a main body (drive unit) BD that rotates the shaft SF, and an encoder device EC that detects rotational position information of the shaft SF. In this drive device MTR, the motor control unit 32 shown in FIG. 1 controls the main body BD using the detection results of the encoder device EC. The drive device MTR can drive the shaft SF with high precision using the rotation information of the shaft SF detected using the encoder device EC. The drive device MTR is not limited to a motor device and may be another drive device having a shaft that rotates using hydraulic or pneumatic pressure.

[0086] The encoder system ENS or encoder device EC described above may be used in a stage device STG (not shown). When the stage device STG drives the drive device MTR to rotate the shaft SF, this rotation is transmitted to the turntable TB. At that time, the encoder device EC detects the angular position of the shaft SF. Therefore, the output result from the encoder device EC can be used to detect the angular position of the turntable TB. A reducer or the like may be disposed between the shaft SF of the drive device MTR and the turntable TB. Since the stage device STG can drive the shaft SF with high precision using the encoder device EC, it can control the turntable TB with high precision. The stage device STG can be applied to a turntable or the like provided in a machine tool such as a lathe.

[0087] The encoder system ENS or encoder device EC described above may be used in a robot device RBT (not shown). The encoder device EC is used, for example, in a part of the robot device RBT (specifically, a joint portion, etc.). The robot device RBT has a first arm, a second arm, and a joint portion (not shown). The first arm is connected to the second arm via the joint portion. When the robot device RBT drives the drive device MTR described above to rotate the shaft SF, this rotation is transmitted to the shaft SF. The rotation of the shaft SF causes the second arm to rotate relative to the first arm. At this time, the encoder device EC detects the angular position of the shaft SF, etc. Therefore, the angular position of the second arm can be detected based on the output from the encoder device EC. In this way, the robot device RBT can perform high-precision positioning using the encoder device EC. The robot device RBT can be applied to various robot devices equipped with joints.

[0088] In addition, all or part of the functions of each unit of each device in the above-mentioned embodiments may be realized by recording a program for realizing these functions on a computer-readable recording medium, and reading and executing the program recorded on the recording medium into a computer system. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0089] Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage units such as hard disks built into computer systems. Furthermore, "computer-readable recording media" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or communication lines like telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within computer systems that serve as servers or clients in such cases. Furthermore, the above-mentioned programs may be programs that realize some of the aforementioned functions, or may be programs that can realize the aforementioned functions in combination with programs already stored in the computer system.

[0090] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications can be made without departing from the spirit of the present invention. Furthermore, the configurations described in the above-described embodiments and examples can be combined.

[0091] According to the present invention, it is possible to provide an encoder device that provides highly reliable detection results.

[0092] ENS...encoder system, EC...encoder device, 30...control device, 31...encoder control unit, 32...motor control unit, 33...motor drive unit, M...motor, SF...shaft, AX...rotating axis, 5...base, 6...disk, 11A...first detector, 11B...second detector, SI...incremental scale, SA...absolute scale, 17...bolt, 50...support member, 51...first support member, 52...second support member, SI1...first detection signal, SI2...second detection signal, DRVI...drive information, ES...encoder information, CS...control information, 311...amplifier circuit, 312...ADC, 313...position information generation unit, 314...position information correction unit, 315...error correction data storage unit, 316...calculation unit, 317...switching control unit, 318...output unit

Claims

1. A first detector that irradiates light onto a pattern provided along the rotational direction of a rotating axis that rotates and moves, detects the light from the pattern, and outputs a first detection signal; a second detector that is arranged at a position a predetermined angle away from the first detector along the rotational direction of the rotating axis, irradiates light onto the pattern, detects the light from the pattern, and outputs a second detection signal; and a control circuit that selects the other one of the first detector and the second detector based on first information regarding an abnormality or prediction of an abnormality of one of the first detector and the second detector, and calculates rotational position information of the rotating axis based on the detection signal of the selected detector. An encoder device comprising the above components.

2. The encoder device according to claim 1, wherein the control circuit selects the first detector and the second detector at an angle at which the angular errors of the first rotational position information and the second rotational position information become substantially the same value, based on the first rotational position information calculated based on the first detection signal and the second rotational position information calculated based on the second detection signal.

3. The encoder device according to claim 1, wherein the control circuit outputs rotational position information obtained by offsetting the difference between the angular errors of the first rotational position information and the second rotational position information, based on the first rotational position information calculated based on the first detection signal and the second rotational position information calculated based on the second detection signal.

4. The encoder device according to claim 1, wherein the control circuit rewrites the origin position of the second rotational position information calculated based on the second detection signal in accordance with the origin position of the first rotational position information calculated based on the first detection signal.

5. The encoder device according to claim 1, wherein the control circuit outputs an average value of the first rotational position information calculated based on the first detection signal and the second rotational position information calculated based on the second detection signal.

6. The encoder device according to claim 1, wherein the control circuit selects the other one of the first detector and the second detector based on the acceleration or speed of the rotating axis.

7. The encoder device according to claim 1, wherein the control circuit outputs rotational position information obtained by offsetting the difference between the first rotational position information and the second rotational position information, based on the first rotational position information calculated based on the first detection signal and the second rotational position information calculated based on the second detection signal.

8. A first detector that irradiates a pattern provided along the rotation direction of a rotation axis that rotates and moves with light, detects the light from the pattern, and outputs a first detection signal; a second detector that is arranged at a position separated by a predetermined angle along the rotation direction of the rotation axis with respect to the first detector, irradiates the pattern with light, detects the light from the pattern, and outputs a second detection signal; and a control circuit that selects one of the first detector and the second detector so as to exclude the first detector or the second detector in which an abnormality or a prediction of an abnormality has occurred, and calculates rotation position information of the rotation axis based on the detection signal of the selected detector. An encoder device comprising:

9. The encoder device according to claim 8, wherein the control circuit selects the first detector and the second detector at an angle at which an angular error between the first rotation position information calculated based on the first detection signal and the second rotation position information calculated based on the second detection signal becomes substantially the same value.

10. The encoder device according to claim 8, wherein the control circuit outputs rotation position information obtained by offsetting a difference between angular errors of the first rotation position information and the second rotation position information based on the first rotation position information calculated based on the first detection signal and the second rotation position information calculated based on the second detection signal.

11. The encoder device according to claim 8, wherein the control circuit rewrites an origin position of second rotation position information calculated based on the second detection signal in accordance with an origin position of first rotation position information calculated based on the first detection signal.

12. The encoder device according to claim 8, wherein the control circuit outputs an average value of the first rotation position information calculated based on the first detection signal and the second rotation position information calculated based on the second detection signal.

13. The encoder device according to claim 8, wherein the control circuit selects the other of the first detector and the second detector based on the acceleration or speed of the rotation axis.

14. The encoder device according to claim 8, wherein the control circuit outputs rotation position information obtained by offsetting a difference between the first rotation position information and the second rotation position information based on the first rotation position information calculated based on the first detection signal and the second rotation position information calculated based on the second detection signal.

15. The first detector includes a first light emitting element that irradiates light onto the pattern, and a first light receiving element that receives the light irradiated by the first light emitting element and is the light from the pattern. The second detector includes a second light emitting element that irradiates light onto the pattern, and a second light receiving element that receives the light irradiated by the second light emitting element and is the light from the pattern. The control circuit determines whether the first detector is approaching a failure state based on the amount of light received by the first light receiving element, determines whether the second detector is approaching a failure state based on the amount of light received by the second light receiving element, and outputs the first information when it is determined that either detector is approaching a failure state. The encoder device according to claim 1.

16. The threshold value for determining whether the first detector is approaching a failure state and the threshold value for determining whether the second detector is approaching a failure state are different from each other. The encoder device according to claim 15.

17. The threshold value for determining whether the first detector is approaching a failure state and the threshold value for determining whether the second detector is approaching a failure state both differ according to the rotational speed of the rotating shaft. The encoder device according to claim 15.

18. The control circuit includes a first driving unit that controls the intensity of the light irradiated by the first light emitting element, and a second driving unit that controls the intensity of the light irradiated by the second light emitting element. The first driving unit controls the intensity of the light irradiated by the first light emitting element according to the amount of light received by the first light receiving element, and the second driving unit controls the intensity of the light irradiated by the second light emitting element according to the amount of light received by the second light receiving element. The control circuit determines that the first detector is approaching a failure state when the intensity of the light irradiated by the first light emitting element is equal to or greater than a predetermined threshold value and the amount of light received by the first light receiving element is equal to or less than a predetermined value, and determines that the second detector is approaching a failure state when the intensity of the light irradiated by the second light emitting element is equal to or greater than a predetermined threshold value and the amount of light received by the second light receiving element is equal to or less than a predetermined value. The encoder device according to claim 15.

19. The encoder device according to claim 15, further comprising a temperature information acquisition unit that acquires temperature information around the first detector and the second detector, wherein a threshold value for determining whether the first detector is approaching a failure state and a threshold value for determining whether the second detector is approaching a failure state are both different according to the acquired temperature information.

20. A drive device comprising the encoder device according to any one of claims 1 to 19, and a power supply unit that supplies power to a moving unit.

21. A stage device comprising a moving object and the drive device according to claim 20 that moves the moving object.

22. A robot device comprising the drive device according to claim 20 and an arm that relatively moves by the drive device.

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