Method for positioning and detecting the position of an encoder device

Abstract

To improve the reliability of location detection results. [Solution] A positioning method for an encoder device comprising: a first detection unit that detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal; a second detection unit that is positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving part and outputs a second detection signal; a calculation unit that determines rotation information of the moving part based on the first detection signal or the second detection signal; and a support member that integrally supports the first detection unit and the second detection unit, the positioning method comprising positioning the first detection unit and the second detection unit in the radial direction of the rotational movement of the moving part.

Description

Technical Field

[0001] The present invention relates to an encoder device, a method of using an encoder device, a method of positioning an encoder device, a position detection method using an encoder device, a drive device, a stage device, and a robot device.

Background Art

[0002] An encoder device that detects position information such as the rotation angle or rotation speed of a test object is mounted on various devices such as a robot device. As a conventional encoder device, there is known a device that illuminates a pattern with a light emitting element, receives light from the pattern with a light receiving element, and includes a backup power source (see, for example, Patent Document 1). It is desired to improve the reliability of the detection results of the encoder device as described above.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] According to a first aspect, there is provided an encoder device including: a first detection unit that irradiates light onto a pattern of a moving unit, detects light from the pattern, and outputs a first detection signal and a second detection signal; a second detection unit that is arranged at different positions along the moving direction of the moving unit with respect to the first detection unit, irradiates light onto the pattern, detects light from the pattern, and outputs a third detection signal; and an arithmetic unit that obtains movement information of the moving unit based on two detection signals having different phases from each other with respect to the movement of the moving unit among the first detection signal, the second detection signal, and the third detection signal.

[0005] According to a second aspect, there is provided a drive device including the encoder device according to the first aspect and a power supply unit that supplies power to the moving unit. According to a third embodiment, a stage apparatus is provided comprising a moving object and a drive device of a second embodiment for moving the moving object. According to a fourth aspect, a robotic device is provided comprising a drive device according to the second aspect and an arm that moves relative to the drive device.

[0006] According to a fifth aspect, a method for using an encoder device is provided, comprising: a first detection unit that irradiates light onto a pattern of a moving part, detects the light from the pattern and outputs a first detection signal and a second detection signal; a second detection unit positioned at a different location from the first detection unit along the direction of movement of the moving part, irradiates light onto its pattern, detects the light from the pattern and outputs a third detection signal; and a calculation unit that determines movement information of the moving part using two detection signals from the first detection signal, the second detection signal and the third detection signal, which are in phase with respect to the movement of the moving part, the method for using the encoder device is provided, which includes determining movement information of the moving part using one of the first detection signal and the second detection signal and the third detection signal which is in phase with respect to the direction of movement of the moving part.

[0007] According to the sixth aspect, a positioning method for an encoder device is provided, comprising: a first detection unit that detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal; a second detection unit positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving part and that detects light from the pattern and outputs a second detection signal; a calculation unit that determines rotation information of the moving part based on the first detection signal and the second detection signal; and a support member that integrally supports the first detection unit and the second detection unit, wherein the positioning method for an encoder device is provided, the first detection unit and the second detection unit each being positioned in the radial direction of the rotational movement of the moving part.

[0008] According to the seventh aspect, a method for detecting the position of an encoder device is provided, comprising: a first detection unit that detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal with respect to the rotational movement of the moving part; a second detection unit positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving part and that detects light from the pattern and outputs a second detection signal; and a calculation unit that calculates rotation information of the moving part based on the first detection signal and the second detection signal, the method for detecting the position of an encoder device is provided, which includes: calculating an error in the rotation information from the difference between the rotation information of the moving part obtained from the first detection signal and the rotation information of the moving part obtained from the second detection signal; and calculating the rotation information of the moving part using the first detection signal, the second detection signal, and the error. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing an encoder device according to the first embodiment. [Figure 2] (A) is a plan view showing the disk and detection unit in Figure 1, and (B) is a diagram showing the detection unit and detection circuit unit, etc., in Figure 1. [Figure 3] (A) is a diagram showing an example of the four detection signals in Figure 2(B), (B) is a diagram showing the state transitions of the two sets of detection signals in Figure 2(B), and (C) is a diagram showing the four states of a normal detection signal. [Figure 4] This flowchart shows an example of how to use the encoder device of the first embodiment. [Figure 5] This flowchart shows another example of how to use an encoder device. [Figure 6] (A) is a diagram showing the case where one of the four detection signals is abnormal, (B) is a diagram showing the case where two of the four detection signals are abnormal, and (C) is a diagram showing an example of a combination of detection signals in which rotation information can be detected. [Figure 7] (A) is a diagram showing the case where two of the four detection signals are abnormal, and (B) is a diagram showing an example of a state change corresponding to Figure 7(A). [Figure 8](A) is a plan view showing a modified disk and detection unit, and (B) is a diagram showing an example of four detection signals obtained from the detection unit in Figure 8(A). [Figure 9] This figure shows a modified encoder device. [Figure 10] (A) is a plan view showing the mechanism of the angle detection unit of the encoder device according to the second embodiment, (B) is a cross-sectional side view of a part of Figure 10(A), and (C) is an enlarged plan view of the main part of Figure 10(A). [Figure 11] This figure shows the configuration of the detection circuit section of the encoder device according to the second embodiment. [Figure 12] (A), (B), (C), (D), (E), and (F) are diagrams showing examples of multiple signals within the detection circuit section of Figure 11, and (G) is a diagram showing an example of an absolute value detection signal when no phase difference adjustment is performed (comparative example). [Figure 13] (A) is a partially cut-out plan view showing the positioning of the detection units 11A and 11B relative to the disk 6, and (B) is an enlarged plan view showing an example of the misalignment between a part of the pattern on the disk 6 and the detection units 11A and 11B. [Figure 14] (A) is a flowchart showing an example of a positioning method according to the second embodiment, and (B) is a flowchart showing an example of a detection method according to the third embodiment. [Figure 15] This is a plan view showing an example of the arrangement of the first and second detection units of the angle detection unit of the encoder device according to the second embodiment. [Figure 16] This figure shows an example of a drive mechanism. [Figure 17] This is a diagram showing an example of a stage setup. [Figure 18] This figure shows an example of a robotic device. [Modes for carrying out the invention]

[0010] [First Embodiment] A first embodiment will be described with reference to FIGS. 1 to 7. FIG. 1 shows an encoder device EC according to this embodiment. In FIG. 1, the encoder device EC detects the rotational position information of the rotating shaft SF (moving part) of the motor M (power supply unit). The rotating shaft SF is, for example, the shaft (rotor) of the motor M, but may also be a working shaft (output shaft) that is connected to the shaft of the motor M via a power transmission unit such as a transmission and is connected to a load. The rotational position information detected by the encoder device EC is supplied to the motor control unit 26. The main control unit 27 of the motor control unit 26 controls the rotation (for example, rotational position, rotational speed, etc.) of the motor M using the rotational position information supplied from the encoder device EC. The motor control unit 26 controls the rotation of the rotating shaft SF.

[0011] The encoder device EC includes a position detection system (position detection unit) 2 that detects the rotational position information of the rotating shaft SF. The encoder device EC is a so-called multi-turn absolute encoder. The position detection system 2 includes a multi-turn information detection unit 3 that detects multi-turn information indicating the number and direction of rotation of the rotating shaft SF, and an angle detection unit 4 that detects rotational position information including angle position information (rotation angle) less than one rotation.

[0012] At least a part of the position detection system 2 (for example, the angle detection unit 4) operates by receiving power supply from the main power supply (hereinafter referred to as the main power supply) of the device (for example, a drive device, a stage device, a robot device) on which the encoder device EC is mounted as an example. Also, at least a part of the position detection system 2 (for example, the multi-turn information detection unit 3) operates by receiving power supply from the battery 15 in a state where the main power supply supplies power (power-on state) and in a state where the main power supply does not supply power (power-off state or backup state, etc.).

[0013] The battery 15 includes, for example, a primary battery (such as a button battery) and a rechargeable secondary battery. A switching unit 16 is connected to the battery 15. The power supply unit MCE of the motor control unit 26 is part of its main power supply. When the power supply unit MCE is supplying power (power on), the power supply unit MCE charges the secondary battery of the battery 15. The switching unit 16 then supplies power from the secondary battery to the multi-turn information detection unit 3. On the other hand, when the power supply unit MCE is not supplying power (power off), the secondary battery is not charged. In this state, if there is a lot of remaining power in the secondary battery, the switching unit 16 may supply power from the secondary battery to the multi-turn information detection unit 3. Also, when the power is off and there is little remaining power in the secondary battery, the switching unit 16 may supply power from the primary battery to the multi-turn information detection unit 3. For this reason, even when the power is off, the position detection system 2 (multi-turn information detection unit 3) can detect at least a part of the rotational position information of the rotation axis SF (in this case, multi-turn information).

[0014] The multi-turn information detection unit 3 detects multi-turn information using an optical method, for example. The multi-turn information detection unit 3 includes a first detection unit 10A that detects a multi-turn information detection pattern 8S formed on a disc-shaped disk 6 connected to the rotation axis SF, a second detection unit 10B that detects the pattern 8S at different positions, and a detection signal processing unit 12. The detection signal processing unit 12 includes a control unit 13, a storage unit 14 consisting of, for example, non-volatile memory, and the aforementioned battery 15 and switching unit 16. The disk 6 is fixed to a disc 5 attached to the rotation axis SF by bolts 17 (see Figure 2(A)). Since the disc 5 rotates together with the rotation axis SF, the disk 6 rotates in conjunction with the rotation axis SF. In the detection signal processing unit 12, the control unit 13 processes the detection signals from the detection units 10A and 10B to detect multi-turn information of the rotation axis SF. The storage unit 14 stores the multi-turn information detected by the control unit 13.

[0015] The angle detection unit 4 is, for example, an optical encoder, and detects position information (angle position information) within one rotation of the disk 6. For example, when it is an optical encoder, the angle detection unit 4 has a first detection unit 11A that detects light from a pattern 9S for detecting the angle position of the disk 6, a second detection unit 11B that detects light from the pattern 9S at different positions, and a detection circuit unit 21 that processes the detection signals from the detection units 11A and 11B to detect the angle position within one rotation of the rotation axis SF. The pattern 9S includes, for example, an absolute scale and an incremental scale. Note that the second detection unit 11B can be omitted for the angle detection unit 4.

[0016] The detection circuit 21 detects the angular position with a first resolution using, for example, the result of detecting light from an absolute scale. The detection circuit 21 also detects the angular position with a second resolution higher than the first resolution by performing interpolation calculations on the angular position with the first resolution using the result of detecting light from an incremental scale. The disk 6 may be, for example, a component integrated with the disc 5. The multi-turn information detection unit 3 and the angle detection unit 4 are, for example, reflective optical types, but they may also be configured as transmissive optical encoders.

[0017] In this embodiment, the encoder device EC includes a signal combining unit 22. The signal combining unit 22 calculates and processes the detection results from the position detection system 2. The signal combining unit 22 includes a combining unit 23 and a data communication unit 24. The combining unit 23 acquires angular position information of second resolution detected by the detection circuit unit 21. The combining unit 23 also acquires multi-rotation information of the rotation axis SF from the storage unit 14 of the multi-rotation information detection unit 3. The combining unit 23 calculates rotational position information by combining the angular position information from the detection circuit unit 21 and the multi-rotation information from the multi-rotation information detection unit 3. For example, if the detection result from the detection circuit unit 21 is θ (rad) and the detection result from the multi-rotation information detection unit 3 is n rotations, the combining unit 23 calculates (2π × n + θ) (rad) as rotational position information. The rotational position information may also be information that combines multi-rotation information and angular position information of less than one rotation.

[0018] The synthesis unit 23 supplies rotational position information to the data communication unit 24. The data communication unit 24 is communicated with the communication unit MCC of the motor control unit 26 by wire or wireless connection. The data communication unit 24 supplies rotational position information in digital format to the communication unit MCC of the motor control unit 26. The main control unit 27 of the motor control unit 26 acquires the rotational position information from the data communication unit 24, for example, at a predetermined sampling rate. The main control unit 27 controls the rotation of the motor M by controlling the power (driving power) supplied to the motor M using this rotational position information.

[0019] Next, the multi-turn information detection unit 3 of this embodiment will be described. Figure 2(A) is a plan view showing the disk 6 and detection units 10A and 10B in Figure 1, and Figure 2(B) is a diagram showing the detection units 10A and 10B and the control unit 13, etc., in Figure 1. As shown in Figure 2(A), the surface of the disk 6 has four reflective patterns, the first pattern 8A, the second pattern 8B, the third pattern 8C, and the fourth pattern 8D, each shaped like half of a concentric ring band around a rotation center. That is, patterns 8A to 8D are each semi-ring band patterns with an opening angle of 180°, with the first pattern 8A having the largest diameter, and the diameters of the second pattern 8B, third pattern 8C, and fourth pattern 8D gradually decreasing in that order. Furthermore, the second pattern 8B is arranged by rotating the first pattern 8A 180° around its rotation center, and the third pattern 8C and fourth pattern 8D are arranged by rotating the first pattern 8A and the second pattern 8B 90° clockwise around their respective rotation centers. Patterns 8A to 8D correspond to pattern 8S in Figure 1. Outside of patterns 8A to 8D, pattern 9S for the angle detection unit 4 in Figure 1 is formed.

[0020] The first detection unit 10A is positioned opposite patterns 8A to 8D, and the second detection unit 10B is positioned at a location where the first detection unit 10A is rotated 90° clockwise around the rotation center of the disk 6. As shown in Figure 2(B), the first detection unit 10A includes a light-emitting diode (hereinafter referred to as LED) 31 that irradiates patterns 8A to 8D with detection light, and light-receiving elements 32A, 32B, 32C, and 32D that receive reflected light from patterns 8A, 8B, 8C, and 8D. Furthermore, the first detection unit 10A includes an analog comparator 33A that calculates a detection signal MA1 obtained by digitizing the difference between the signals output from the light-receiving elements 32A and 32B, and an analog comparator 33B that calculates a detection signal MB1 obtained by digitizing the difference between the signals output from the light-receiving elements 32C and 32D. The detection signals MA1 and MB1 are supplied to the calculation control unit 40 of the control unit 13. The calculation control unit 40 includes a counter 40a, a determination unit 40b, and a storage unit (details described later). As shown in Figure 3(A), the detection signals MA1 and MB1 are rectangular wave signals with one period corresponding to the time it takes for the disk 6 to complete one rotation (rotation angle of 360°), and the phase of the detection signal MB1 is shifted by 90° relative to the detection signal MA1. The horizontal axis in Figure 3(A) represents time t. The detection signals in Figure 3(A) are the signals obtained when the disk 6 in Figure 2(A) is rotated counterclockwise (hereinafter referred to as the forward direction).

[0021] Similarly, the second detection unit 10B includes a light-emitting diode (hereinafter referred to as LED) 34 that irradiates patterns 8A to 8D with detection light, and light-receiving elements 35A, 35B, 35C, and 35D that receive reflected light from patterns 8A, 8B, 8C, and 8D. Note that any light-emitting element such as a semiconductor laser can be used instead of LEDs 31 and 34. For example, photodiodes can be used as the light-receiving elements 32A to 32D and 35A to 35D.

[0022] Furthermore, the second detection unit 10B includes an analog comparator 36A that calculates a detection signal MA2 obtained by digitizing the difference between the signals output from the photodetectors 35A and 35B, and an analog comparator 36B that calculates a detection signal MB2 obtained by digitizing the difference between the signals output from the photodetectors 35C and 35D. The detection signals MA2 and MB2 are also supplied to the arithmetic control unit 40 of the control unit 13. As shown in Figure 3(A), the detection signals MA2 and MB2 are square wave signals with one period equal to the time it takes for the disk 6 to rotate once, and the phase of the detection signal MB2 is shifted by 90° relative to the detection signal MA2. Furthermore, in this embodiment, the position of the second detection unit 10B is 90° different from the position of the first detection unit 10A. For this reason, the phases of the detection signals MA2 and MB2 are shifted by 90° relative to the detection signals MA1 and MB1, respectively. In this embodiment, the phase of the detection signal MA2 is approximately equal to the phase of the detection signal MB1, and the phase of the detection signal MB2 is approximately 180° different from the phase of the detection signal MA1.

[0023] In Figure 2(B), the control unit 13 includes a calculation control unit 40 and a light emission control unit 39 that outputs drive signals 31L and 34L for illuminating LEDs 31 and 34. As an example, the light emission control unit 39 further supplies a sampling signal SS to the calculation control unit 40 for detecting detection signals MA1 to MB2. The calculation control unit 40 reads the detection signals MA1 to MB2 in synchronization with the sampling signal SS. When the light emission control signals LE1 or LE2 supplied by the calculation control unit 40 to the light emission control unit 39 are set to a high level (normally a low level), the light emission control unit 39 can stop the illumination of LEDs 31 or 34.

[0024] When the first detection unit 10A is operating normally (detection signals MA1 and MB1 are normal), the counter 40a in the calculation control unit 40 can obtain multi-rotation information of the rotating shaft SF using the detection signals MA1 and MB1 read from the first detection unit 10A. For example, if detection signal MB1 is at a low level when detection signal MA1 changes from a low level to a high level, an up signal is supplied to the storage unit 14 to increase the rotation speed by 1. On the other hand, if detection signal MB1 is at a high level when detection signal MA1 changes from a low level to a high level, a down signal is supplied to the storage unit 14 to decrease the rotation speed by 1. In response, the storage unit 14 increases or decreases the rotation speed stored up to that point, thereby obtaining the rotation speed (multi-rotation information) of the rotating shaft SF. ) can be calculated precisely.

[0025] Furthermore, when the second detection unit 10B is operating normally, the counter 40a in the calculation control unit 40 can similarly obtain multi-turn information of the rotating shaft SF using the detection signals MA2 and MB2 read from the second detection unit 10B. Also, the phases of the detection signals MB1 and MA2 are almost equal, and the phases of the detection signals MA1 and MB2 are approximately 180° different (inverted). For this reason, multi-turn information of the rotating shaft SF can also be obtained using combinations of detection signal MA1 or MB2 and detection signal MB or MA2. In other words, multi-turn information can sometimes be obtained even when the detection units 10A and 10B are not functioning properly.

[0026] In the determination unit 40b within the calculation control unit 40, if any of the detection signals MA1 to MB2 are not normal but multi-turn information can be detected, the determination unit 40b transmits a first alarm signal AS1 to the main control unit 27 of the motor control unit 26 via the data communication unit 24 in Figure 1. If at least two of the detection signals MA1 to MB2 are not normal and multi-turn information cannot be detected, the determination unit 40b transmits a second alarm signal AS2 to the main control unit 27 of the motor control unit 26. The main control unit 27 can perform processing according to the alarm signals AS1 and AS2.

[0027] Next, an example of the basic usage method of the encoder device EC of this embodiment will be explained with reference to the flowchart in Figure 4. In this usage method, the determination unit 40b of the arithmetic control unit 40 in the control unit 13 determines whether each of the four detection signals MA1 to MB2 is normal, that is, whether it can be used to detect multi-turn information. In this case, as an example, the combination and / or transition of the states of the detection signals MA1, MB1 and MA2, MB2 is examined. As shown in Figure 3(A), the normal combination of detection signals MA1, MB1 is state 1 (ST1) where MA1 is at a high level (hereinafter represented by H) and MB1 is at a low level (hereinafter represented by L), state 2 (ST2) where MA1 and MB1 are at (H, H), state 3 (ST3) where MA1 and MB1 are at (L, H), and state 4 (ST4) where MA1 and MB1 are at (L, L). Similarly, the normal detection signal combinations MA2 and MB2 include state 1 (ST1) where MA2 and MB2 are (L,L), state 2 (ST2) where MA2 and MB2 are (H,L), state 3 (ST3) where MA2 and MB2 are (H,H), and state 4 (ST4) where MA2 and MB2 are (L,H). If the period of detection signals MA1 and MB1 is T1, then the period T2 of each state is T1 / 4. In principle, if detection signals MA1 and MB1 are in states 1 to 4, then detection signals MA2 and MB2 are also in the same states 1 to 4. The normal level combinations of detection signals MA1 to MB2 in states 1 to 4 are shown in Figure 3(C).

[0028] When disk 6 in Figure 2(A) rotates in the forward direction, as shown in Figure 3(B), the state transitions 18A for detection signals MA1 and MB1 and 18B for detection signals MA2 and MB2 are in the order of state 1, state 2, state 3, state 4, and state 1. When disk 6 rotates in the reverse direction (clockwise), the state transitions 18A and 18B are in the order of state 1, state 4, state 3, state 2, and state 1. These state transition patterns 18A and 18B are stored in a memory unit such as a ROM in the arithmetic control unit 40.

[0029] The determination unit 40b of the arithmetic control unit 40 can determine whether the detection signals MA1 to MB2 are normal based on, for example, the state transitions of these detection signals. For example, as shown in Figure 6(A), if the levels of three of the four detection signals MA1 to MB2 (MB1, MA2, MB2) have changed, but the level of the remaining detection signal MA1 has not changed (its state has not transitioned), then detection signal MA1 can be considered abnormal. Similarly, as shown in Figure 6(B), if the levels of two of the four detection signals MA1 to MB2 (MA1, MB2) have changed, but the levels of the other two detection signals (MB1, MA2) have not changed, then detection signals MB1, MA2 can be considered abnormal.

[0030] As another example, the determination unit of the arithmetic control unit 40 can determine whether the detection signals MA1 to MB2 are normal based on the combination of states of these detection signals. For example, as shown in Figure 7(A), if the levels of two of the four detection signals MA1 to MB2 have changed, while the levels of the other two detection signals MB1 to MA2 have not changed, the combination of levels of detection signals MA1 to MB2 in states 1 to 4 will be as shown in Figure 7(B). Comparing the combination of detection signal levels (states) in Figure 7(B) with the combination of normal detection signal levels in Figure 3(C), it can be seen that the combination of levels in states 2 and 3 in Figure 7(B) is different from the corresponding part in Figure 3(C) (the levels of detection signals MB1 and MA2 are different). From this comparison, it can be determined that the detection signals MB1 and MA2 are not normal.

[0031] Then, as a basic method of using the encoder device EC, in step 102 of Figure 4, the light emission control unit 39 lights up the LEDs 31 and 34 of the first detection unit 10A and the second detection unit 10B, and in step 104, the calculation control unit 40 reads the four detection signals MA1, MB1, MA2, and MB2 of the detection units 10A and 10B. Furthermore, in step 108, the determination unit of the calculation control unit 40 determines whether the detection signal MA1 is normal or not using the determination method described above, and if the detection signal MA1 is normal, the process moves to step 110 to determine whether the detection signal MB1 is normal or not. If the detection signal MB1 is normal, the process moves to step 114, and the counter 40a of the calculation control unit 40 reads the detection signals MA1 and MB1 of the first detection unit 10A as valid (normal) detection signals. In the next step 116, the counter of the calculation control unit 40 processes the read detection signals MA1 and MB1 to calculate multi-rotation information of the rotating shaft SF (for example, the up signal or down signal mentioned above) (rotation information), and stores the calculated information in the storage unit 14. After that, the operations of steps 114 and 116 are repeated.

[0032] On the other hand, if the detection signal MB1 is not normal in step 110, the process moves to step 118, where the determination unit of the calculation control unit 40 determines whether the detection signal MA2 of the second detection unit 10B is normal or not. If the detection signal MA2 is normal, the process moves to step 114, where the counter of the calculation control unit 40 reads the detection signal MA1 of the first detection unit 10A and the detection signal MA2 of the second detection unit 10B as valid detection signals. Then, in step 116, the counter of the calculation control unit 40 calculates multi-turn information using the detection signals MA1 and MA2, and stores the calculated information in the storage unit 14.

[0033] Furthermore, if the detection signal MA2 is not normal in step 118, the two detection signals necessary to obtain multi-turn information are not present, and the process proceeds to step 126. The determination unit of the calculation control unit 40 then transmits a second alarm signal AS2 (second alarm information) to the main control unit 27 of the motor control unit 26 in Figure 1, indicating that rotation information cannot be detected. In response, for example, the main control unit 27 provides information to the operator (not shown) that the multi-turn information detection unit 3 of the encoder device EC is not functioning correctly, and the operator performs maintenance such as replacing the detection units 10A and 10B.

[0034] Furthermore, in step 108, if the detection signal MA1 is not normal, the process proceeds to step 130, where the determination unit of the calculation control unit 40 determines whether the detection signal MB2 of the second detection unit 10B is normal or not. If the detection signal MB2 is normal, the process proceeds to step 110 to use the detection signal MB2 instead of the detection signal MA1. If either the detection signal MB1 or MA2 is normal, the process proceeds to step 114, where the counter of the calculation control unit 40 reads the detection signal MB2 and the detection signal MB1 (or MA2) as valid detection signals. Then, in step 116, the counter of the calculation control unit 40 calculates multi-turn information using the read detection signals and stores the calculated information in the storage unit 14.

[0035] Furthermore, if the detection signal MB2 is not normal in step 130, the system proceeds to step 126 because the two detection signals necessary to obtain multi-turn information are not present. The determination unit of the calculation control unit 40 then transmits a second alarm signal AS2 to the main control unit 27 of the motor control unit 26 in Figure 1, indicating that rotation information cannot be detected. To summarize the above operations, if the abnormal detection signal is one of the signals in the left column of the table in Figure 6(C), the combination of two detection signals capable of detecting multi-turn information of the rotating shaft SF is as shown in the right column of the table. In the table in Figure 6(C), if only the detection signal MA1 is abnormal, the detectable combination of detection signals is detection signals MB2 and MB1 (or MA2), and if only the detection signal MB1 is abnormal, the detectable combination of detection signals is detection signals MA2 and MB2 (or MA1).

[0036] Furthermore, if detection signals MB1 and MB2 are not normal, the detectable combination of detection signals is detection signals MA1 and MA2. If detection signals MA1 and MB1 are not normal, the detectable combination of detection signals is detection signals MA2 and MB2. On the other hand, if detection signals MA1 and MB2 are not normal, and if detection signals MB1 and MA2 are not normal, there are no detectable combinations of detection signals. In this case, in step 126, the determination unit (control unit 13) of the calculation control unit 40 outputs the second alarm signal AS2.

[0037] According to this method of use, for example, if one detection signal MA1 of the first detection unit 10A is normal but the other detection signal MB1 is not, the rotation information of the rotating shaft SF can be obtained using detection signal MA1 and detection signal MA2 of the second detection unit 10B. This improves the reliability of the rotation information detection result. Furthermore, if two of the four detection signals MA1 to MB2 have a phase difference of 90° (or 270°) from each other and are normal, the rotation information can be detected using these two detection signals.

[0038] Next, another example of how to use this embodiment will be described with reference to the flowchart in Figure 5. First, in step 102 of Figure 5, the light emission control unit 39 lights up the LEDs 31 and 34 of the detection units 10A and 10B. In step 104, the determination unit of the calculation control unit 40 reads the detection signals MA1 to MB2 of the detection units 10A and 10B. In step 106, the determination unit of the calculation control unit 40 checks whether there is a detection signal among the detection signals MA1 to MB2 that has changed to a high level and / or a low level multiple times. If there is no detection signal that has changed multiple times, the process returns to step 104. On the other hand, if there is a detection signal that has changed multiple times in step 106, the process moves to step 108, where the determination unit determines whether the detection signal MA1 is normal or not. Whether the detection signal MA1, etc., is normal or not can be determined based on the combination of states of the detection signals or the transitions between those states, as described above.

[0039] If the detection signal MA1 is normal, the process moves to step 110, where the determination unit of the calculation control unit 40 determines whether the detection signal MB1 is normal or not. If the detection signal MB1 is normal, the process moves to step 112, where the determination unit of the calculation control unit 40 sets the light emission control signal LE2 to a high level, and accordingly, the light emission control unit 39 turns off the LED 34 of the second detection unit 10B. Then, in step 114, the counter of the calculation control unit 40 reads the detection signals MA1 and MB1 of the first detection unit 10A, and in step 116, it calculates and stores the multi-rotation information (rotation information) of the rotating shaft SF. After this, steps 114 and 116 are repeated.

[0040] Furthermore, if the detection signal MB1 is not normal in step 110, the process proceeds to step 118, where the determination unit of the calculation control unit 40 determines whether the detection signal MA2 is normal or not. If the detection signal MA2 is normal, the process proceeds to step 120, where the determination unit of the calculation control unit 40 outputs a first alarm signal AS1 to the main control unit 27 of the motor control unit 26 to indicate that there is an abnormality in a part of the detection signals MA1 to MB2 (in this case, detection signal MB1), but that rotation information can still be detected. Accordingly, the main control unit 27 may, for example, provide the operator with information about the abnormal detection signal during maintenance of the encoder device EC. In the next step 122, the calculation control unit 40 reads the detection signals MA1 and MA2, and in step 124, uses the detection signals MA1 and MA2 to calculate the multi-turn information (rotation information) of the rotating shaft SF, and stores the calculation result in the storage unit 14. After that, steps 122 and 124 are repeated.

[0041] Furthermore, if the detection signal MA2 is not normal in step 118, there is no usable detection signal, so the operation proceeds to step 126, and the determination unit of the calculation control unit 40 outputs the second alarm signal AS2 to the main control unit 27, and the main control unit 27 can perform the corresponding processing described above. As another example, in the next step 128, the determination unit of the calculation control unit 40 sets the light emission control signals LE1 and LE2 to a high level and stops the detection of rotation information. Accordingly, the light emission control unit 39 turns off the LEDs 31 and 34.

[0042] Furthermore, in step 108, if the detection signal MA1 is not normal, the process proceeds to step 130, where the determination unit of the calculation control unit 40 determines whether the detection signal MB2 is normal or not. If the detection signal MB2 is normal, the process proceeds to step 132, where the determination unit of the calculation control unit 40 determines whether the detection signal MB1 is normal or not. If the detection signal MB1 is normal, the process proceeds to step 134, where the determination unit of the calculation control unit 40 outputs a first alarm signal AS1 (first alarm information) to the main control unit 27 of the motor control unit 26 to indicate that there is an abnormality in a part of the detection signals MA1 to MB2 (in this case, detection signal MA1), but that rotation information can still be detected. In the next step 136, the counter of the calculation control unit 40 reads the detection signals MB2 and MB1, and in step 138, the counter of the calculation control unit 40 uses the detection signals MB2 and MB1 to calculate multi-rotation information of the rotating shaft SF and stores the calculation result in the storage unit 14. After that, steps 136 and 138 are repeated.

[0043] Furthermore, in step 132, if the detection signal MB1 is not normal, the process proceeds to step 140, where the determination unit of the calculation control unit 40 determines whether the detection signal MA2 is normal or not. If the detection signal MA2 is normal, the process proceeds to step 142, where the determination unit of the calculation control unit 40 outputs a first alarm signal AS1 to the main control unit 27 of the motor control unit 26 to indicate that there is an abnormality in part of the detection signals MA1~MB2 (in this case, detection signals MA1,MB1), but that rotation information can still be detected. In the next step 144, the determination unit of the calculation control unit 40 sets the light emission control signal LE1 to a high level, and accordingly, the light emission control unit 39 turns off the LED 31 of the first detection unit 10A. Then, in step 146, the counter of the calculation control unit 40 reads the detection signals MA2,MB2 of the second detection unit 10B, and in step 148, the counter calculates and stores the multi-rotation information (rotation information) of the rotating shaft SF. After this, steps 146 and 148 are repeated.

[0044] Furthermore, if the detection signal MA2 is not normal in step 140, and if the detection signal MB2 is not normal in step 130, there are no usable detection signals, and the process proceeds to step 150 in each case. The determination unit of the calculation control unit 40 then outputs the second alarm signal AS2 to the main control unit 27, and the main control unit 27 can perform the corresponding processing described above. As another example, in the next step 152, the detection of rotation information is stopped, similar to step 128.

[0045] According to this method of use, if some of the detection signals from the first detection unit 10A and the second detection unit 10B are abnormal, rotation information can be obtained with high reliability by using another normal detection signal instead. Furthermore, if rotation information can be detected even if there are abnormal detection signals, a first alarm signal AS1 is output, and if there are many abnormal detection signals and rotation information cannot be detected, a second alarm signal AS2 is output. This allows for efficient maintenance of the encoder device EC (such as partial or complete replacement of detectors) by taking measures such as postponing maintenance in response to the first alarm signal AS1.

[0046] As described above, the encoder device EC of this embodiment includes a first detection unit 10A that irradiates light onto the pattern 8S of the disk 5 of the rotating shaft SF (moving part), detects the light from the pattern 8S and outputs a first detection signal MA1 and a second detection signal MB1 which are in different phases with respect to the rotation (movement) of the rotating shaft SF, and a third detection signal MA2 and a fourth detection signal MB2 which are positioned at different positions relative to the first detection unit 10A along the rotation direction (movement direction) of the rotating shaft SF, irradiate light onto the pattern 8S, detect the light from the pattern 8S and output a third detection signal MA2 and a fourth detection signal MB2 The system includes a second detection unit 10B that outputs a signal, a control unit 13 (or determination unit 40b within the calculation control unit 40) that switches between a state in which rotation information (movement information) of the rotation axis SF is determined by the first detection signal MA1 and the second detection signal MB1, and a state in which the rotation information is determined by either the first detection signal MA1 or the second detection signal MB1 and the third detection signal MA2 (or fourth detection signal MB2), and a counter 40a (calculation unit) within the calculation control unit 40 that determines the rotation information based on the detection signals of the state switched by the control unit 13.

[0047] Furthermore, the method of using the encoder device EC of this embodiment includes steps 108, 110, 118, 130, 114 in which the determination unit 40b switches between a state in which the rotation information (movement information) of the rotating shaft SF is determined by the first detection signal MA1 and the second detection signal MB1, and a state in which the rotation information is determined by either the first detection signal MA1 or the second detection signal MB1 and the third detection signal MA2 (or the fourth detection signal MB2), and step 116 in which the counter 40a determines the rotation information using the detection signals of the switched state. According to this embodiment, since there are two detection units 10A and 10B and four detection signals are output, even if an abnormality occurs in one detection signal, the accuracy or reliability of the detection result of the rotation information of the rotating shaft SF can be improved by using the other normal detection signals.

[0048] Furthermore, in this embodiment, when obtaining rotation information using the detection signals MA1 and MB2 of the first detection unit 10A, the LED 34 of the second detection unit 10B may be turned off, and when obtaining rotation information using the detection signals MA2 and MB2 of the second detection unit 10B, the LED 31 of the first detection unit 10A may be turned off. In this case, power consumption can be suppressed and the reliability of the rotation information detection result can be improved.

[0049] The above embodiment can be modified as follows. First, in the above embodiment, as shown in Figure 2(A), the angle between the first detection unit 10A and the second detection unit 10B is 90°. In contrast, as shown in the modified example in Figure 8(A), the second detection unit 10B may be positioned on the disk 6 at an angle of 180° to the first detection unit 10A. In this modified example, the detection signals MA1 and MB1 obtained from the first detection unit 10A when the disk 6 is rotated are assumed to be two-phase rectangular wave signals as shown in Figure 8(B). At this time, the detection signals MA2 and MB2 obtained from the second detection unit 10B are rectangular wave signals obtained by shifting the phase of the corresponding signals in Figure 3(A), for example, by 90°, as shown in Figure 8(B).

[0050] In this modified example, the combination of detection signals MA1 and MB1 in states 1 (ST1) to 4 (ST4) is the same as in the example in Figure 3(A). In contrast, the combination of detection signals MA2 and MB2 in states 1 to 4 is (L,H), (L,L), (H,L), and (H,H), which differs from the example in Figure 3(A). In this modified example, detection signal MA2, which has a phase difference of 180°, can be used instead of detection signal MA1, and detection signal MB2, which has a phase difference of 180°, can be used instead of detection signal MB1. For example, if detection signal MA1 is not normal, rotation information can be obtained using detection signals MB1 and MA2.

[0051] Next, although four detection signals MA1 to MB2 are generated in the above-described embodiment, three detection signals MA1, MB1, and MA2 may be generated, as shown in the modified encoder device ECA in Figure 9. Note that in Figure 9, the same reference numerals are used for parts corresponding to those in Figure 2(B), and their detailed explanation is omitted. In Figure 9, the configuration of the first detection unit 10A is the same as that of the first detection unit 10A in Figure 2(B). The second detection unit 10C includes an LED 34 that illuminates patterns 8A and 8B with detection light, and light-receiving elements 35A and 35B that receive reflected light from patterns 8A and 8B. Furthermore, the second detection unit 10C includes an analog comparator 36A that calculates a detection signal MA2, which is obtained by digitizing the difference between the signals output from the light-receiving elements 35A and 35B. The detection signals MA1 and MB1 from the first detection unit 10A and the detection signal MA2 from the second detection unit 10C are supplied to the arithmetic control unit 40.

[0052] If detection signals MA1 and MB1 are normal, the calculation control unit 40 can calculate multi-rotation information of the rotation axis SF using detection signals MA1 and MB1. Furthermore, if, for example, detection signal MB1 is abnormal, the calculation control unit 40 can calculate multi-rotation information of the rotation axis SF using detection signals MA1 and MA2. Even in this modified example where three detection signals are generated, the reliability of the rotation information detection results can be improved by using a normal detection signal instead of an abnormal detection signal.

[0053] In this modified example, the three detection signals MA1, MB1, and MA2 shown in Figure 2(C) are generated, but the three detection signals MA1, MB1, and MB2 shown in Figure 2(C) may also be generated. Furthermore, in the above-described embodiment, as shown in Figure 2(B), two-phase detection signals MA1 and MB1 are generated from the detection signals of two photodetectors 32A, 32B and 32C, 32D using analog comparators 33A and 33B, and similarly, two-phase detection signals MA2 and MB2 are generated from the detection signals of four photodetectors 35A to 35D. Alternatively, two-phase detection signals MA1 and MB1 may be generated by comparing the detection signals of photodetectors 32A and 32C with a corresponding reference signal. Two-phase detection signals MA2 and MB2 can be generated in the same way. In this case, patterns 8B and 8D can be omitted from disk 6 in Figure 2(A), photodetectors 32B and 32D can be omitted from the first detection unit 10A, and photodetectors 35B and 35D can be omitted from the second detection unit 10, thus simplifying the configuration of disk 6 and detection units 10A and 10B.

[0054] [Second Embodiment] A second embodiment will be described with reference to Figures 10 to 14. In Figures 10 to 13, parts corresponding to those in Figures 1 to 2(B) are denoted by the same reference numerals, and their detailed descriptions are omitted. Figure 10(A) is a plan view showing the mechanism of the angle detection unit 4 of the encoder device ECB according to this embodiment, Figure 10(B) is a side view with a cross-section of a part of Figure 10(A), and Figure 10(C) is an enlarged plan view of the main part of Figure 10(A). The angle detection unit 4 is part of the position detection system 2 in Figure 1. The angle detection unit 4 detects rotational position information (rotation information) including angular position (angle) information indicating a rotation angle of less than one revolution of the rotating shaft SF (moving part) connected to the motor M in Figure 1. The rotation information detected by the angle detection unit 4 is supplied to the motor control unit 26 via the synthesis unit 23 in Figure 1. The motor control unit 26 controls the rotation of the motor M (rotating shaft SF) using the rotation information, etc.

[0055] In Figures 10(A) and (B), a disk 6 is fixed to the surface of a circular disc 5 at the tip of the rotating shaft SF using bolts 17 and washers 17A. An angle detection pattern 9S, including an incremental scale 9SI and an absolute scale 9SA, is formed concentrically on the surface of the disc-shaped disk 6 around the center (rotation center) of the rotating shaft SF. The angle detection unit 4 has a first detection unit 11A that detects light from the pattern 9S on the disk 6, a second detection unit 11B that detects light from the pattern 9S at different positions, and a detection circuit unit 21 (see Figure 11) that processes the detection signals from the detection units 11A and 11B to detect an angle θ of the rotating shaft SF (disk 6) within one rotation. In this embodiment, the position of the second detection unit 11B is shifted by 90° relative to the first detection unit 11A in the rotation direction (θ direction) of the rotating shaft SF. Furthermore, the detection units 11A, 11B and the detection circuit unit 21 are provided on the surface of a common disc-shaped substrate 50 facing the disk 6. The substrate 50 is positioned between the substrate 50 and the disk 6 and is attached to a support member 52 fixed to a main body (not shown). As an example, the substrate 50 is fixed to the support member 52 at two locations using bolts 17B and washers 17C.

[0056] Furthermore, as shown in Figure 10(C), as an example, the incremental scale 9SI is a pattern in which reflective and non-reflective portions are alternately arranged in the rotational direction (circumferential direction) of the disk 6 at a predetermined period, and the absolute scale 9SA is a 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 9SI, are arranged in a predetermined arrangement in the rotational direction of the disk 6. The first detection unit 11A includes a light-emitting diode (hereinafter referred to as LED) 31A that irradiates the scales 9SI and 9SA with detection light, a group of photodetectors 32E consisting of photodetectors 32EA and 32EB that receive reflected light from the incremental scale 9SI via reference gratings 53A1 and 53A2 which have phases that are 90° apart from each other, and a group of photodetectors 54A consisting of a first group of photodetectors 54AX and a second group of photodetectors 54AY that receive reflected light from the absolute scale 9SA. The first group of photodetectors 54AX consists of photodetectors with a width a of half the minimum line width of the reflective portion constituting the absolute scale 9SA, arranged in the rotational direction of the disk 6 at intervals of approximately width a. The second group of photodetectors 54AY has a plurality of photodetectors with width a arranged between the first group of photodetectors 54AX and at one end.

[0057] Similarly, the second detection unit 11B includes an LED 31B, a photodetector group 32F consisting of photodetectors 32FA and 32FB (see Figure 11) that receive reflected light from the incremental scale 9SI through a reference grating with phases differing by 90° from each other, and a photodetector group 54B consisting of a first system and a second system of photodetector groups that receive reflected light from the absolute scale 9SA. Next, Figure 11 shows an example of the configuration of the detection circuit 21 of the angle detection unit 4, and Figures 12(A) to (G) show multiple signals generated within the detection circuit 21 when the disk 6 is rotated. Note that the horizontal axis in Figures 12(A) to (G) represents time t, but if the disk 6 is rotating at a constant angular velocity, the horizontal axis can also be considered as the rotation angle θ of the disk 6.

[0058] In Figure 11, the detection circuit unit 21 includes a first circuit unit 48A and a second circuit unit 48B, both having the same configuration, which process the detection signals from the first detection unit 11A and the second detection unit 11B respectively, and a position output unit 80 that obtains information on the rotation angle θT (detected rotation angle) of the rotation axis SF from the rotation angles θA and θB detected by the first circuit unit 48A and the second circuit unit 48B, respectively. The first circuit section 48A includes amplifiers 58A and 58B that amplify detection signals SA and SB (see Figure 12(A)) with phases differing by 90°, output from two photodetectors 32EA and 32EB that receive reflected light from the incremental scale 9SI; a binarization section 60A that binarizes the outputs of amplifiers 58A and 58B and supplies them to an absolute value processing section 68; and an A / D conversion section 62 that converts the outputs of amplifiers 58A and 58B from analog to digital and supplies them to an interpolation processing section 64. The interpolation processing section 64 interpolates the two-phase digital signals output from the A / D conversion section 62 to determine a rotation angle with a resolution finer than 1 / 4 of one period within the range of one period of the incremental scale 9SI, and supplies the determined rotation angle to the switching signal generation section 66 and the synthesis processing section 78. The rotation angle within one period generated by the interpolation processing section 64 is represented by the sawtooth-shaped interpolation signal Sθ in Figure 12(B), where one period is 360°. For example, the interpolation signal Sθ becomes 0° when the detection signal SB is 0°, and becomes 360° when the detection signal SB is 360°.

[0059] Furthermore, the first detection unit 11A is provided with a selector group 56A that selects either the detection signal of the first group of photodetectors 54AX that receives reflected light from the absolute scale 9SA, or the detection signal of the second group of photodetectors 54AY, and a shift register 56B (bit switching unit) 56B to which the group of detection signals selected by the selector group 56A is supplied. When the XY switching signal SXY (see Figure 12(C)) output from the switching signal generation unit 66 is at a high level, the selector group 56A selects the detection signal ABX (see Figure 12(D)) of the first group of photodetectors 54AX, and when the XY switching signal SXY is at a low level, the selector group 56A selects the detection signal ABY (see Figure 12(D)) of the second group of photodetectors 54AY. In Figure 12(D), the detection signals ABX and ABY are collectively represented by the original absolute value signal ABR. When the rotational position of the first detection unit 11A is as designed, the XY switching signal SXY is high level during the period when the detection signal SB is between 0° and 180°, and low level during the rest of the period. However, in this embodiment, the XY switching signal SXY is out of phase by a phase difference Δθ, which will be described later. That is, the XY switching signal SXY is high level during the period when the detection signal SB is between (0°-Δθ) and (180°-Δθ), and low level during the rest of the period. This operation will be described later.

[0060] The first detection unit 11A includes an amplifier 58C that amplifies the absolute value signal ABS (a signal obtained by concatenating the detection signals ABX and ABY) (see Figure 12(E)) output from the shift register 56B, a binarization unit 60B that supplies a digital signal DAB (see Figure 12(F)) obtained by binarizing the output of the amplifier 58C to the absolute value processing unit 68, a non-volatile memory 74, a control unit 76, and a position output unit 80. The control unit 76 controls the illumination of the LED 31A, etc. Filters to remove noise may be installed between the binarization unit 60A and the absolute value processing unit 68, and between the binarization unit 60B and the absolute value processing unit 68. The absolute value processing unit 68 includes a processing unit 72 that calculates the absolute value of the rotation angle within one rotation (360°) of the disk 6 from the digital signal DAB, and a phase difference measurement unit 70 that calculates the phase difference between the digital signal DAB and the rotation angle within one period obtained from the binarized two-phase signals SA and SB.

[0061] The absolute value information of the rotation angle within one revolution, obtained by the absolute value processing unit 68, is supplied to the synthesis processing unit 78. The synthesis processing unit 78 adds the interpolated rotation angle within one period of the incremental scale 9SI supplied by the interpolation processing unit 64 to the absolute value of the rotation angle within one revolution, thereby determining the rotation angle θA of the disk 6 (rotation axis SF) within one revolution with a resolution finer than 1 / 4 of its period, and supplies the information of the determined rotation angle θA to the position output unit 80.

[0062] The control unit 76 has written information to the non-volatile memory 74, for example, the phase difference Δθ (see Figure 12(B)) between the two-phase signals SA and SB and the digital signal DAB, which was measured before the operation of the encoder device ECB. The information on the phase difference of the angle and the phase difference of the angular velocity, which is obtained by the absolute value processing unit 68, as well as the phase difference Δθ information read from the non-volatile memory 74, are supplied to the switching signal generation unit 66. The switching signal generation unit 66 uses this information, such as the phase difference Δθ, to generate an XY switching signal SXY, as shown in Figure 12(C), in which the detection signal SB is high level during the period from (0°-Δθ) to (180°-Δθ) and low level during other periods.

[0063] The configuration of the second circuit unit 48B, which processes the detection signal from the second detection unit 11B, is the same as that of the first circuit unit 48A. The second circuit unit 48B uses the detection signals from the photodetectors 32FA and 32FB of the second detection unit 11B, and the detection signal from the photodetector group 54B, to determine the rotation angle θB within one rotation of the disk 6 (rotating axis SF) with a resolution finer than 1 / 4 of one period of the incremental scale 9SI, and supplies the determined rotation angle θB information to the position output unit 80. The position detection unit 80, as an example, determines the average value of two rotation angles θA and θB as the detected rotation angle θT, and supplies the determined rotation angle θT to the synthesis unit 23 in Figure 1. The operation of the motor M is controlled using this rotation angle θT and the multi-rotation information obtained by the multi-rotation information detection unit 3 in Figure 1.

[0064] Next, an example of the positioning method and detection method for the encoder device ECB of this embodiment will be described with reference to the flowchart in Figure 14(A). First, in step 160 of Figure 14(A), components such as the disk 6, support member 52, and substrate 50 to which the detection units 11A, 11B and detection circuit unit 21 that constitute the encoder device ECB are manufactured. The disk 6 is attached to the surface of the disc 5 of the rotating shaft SF by bolts 17, and the support member 52 is fixed to a main body (not shown). Then, in step 162, as shown in Figure 13(A), the substrate 50 is attached to the support member 52 using two bolts 17B. At this time, the radial (R) positions of the disk 6 of the first detection unit 11A and the second detection unit 11B are adjusted so that their radial (R) positions align with the position of the pattern 9S. As an example, while rotating the disk 6 in the θ direction, the detection signals of the light-receiving elements 32EA, 32EB (or light-receiving element group 54A) of the first detection unit 11A and the detection signals of the light-receiving elements 32FA, 32FB (or light-receiving element group 54B) of the second detection unit 11B are monitored. First, the position of the substrate 50 in the R direction relative to the support member 52 is adjusted so that the detection signals of the light-receiving elements 32EA, 32EB (or light-receiving element group 54A) of the first detection unit 11A are maximized. Then, the position of the substrate 50 in the R direction relative to the support member 52 is adjusted so that the detection signals of the light-receiving elements 32FA, 32FB (or light-receiving element group 54B) of the second detection unit 11B are maximized. For these adjustments, as an example, the position of the substrate 50 in the R direction relative to the support member 52 can be adjusted while fixing the two bolts 17B. As a result, the reflected light from the incremental scale 9SI to the photodetectors 32EA and 32EB of the first detection unit 11A and the photodetectors 32FA and 32FB of the second detection unit 11B is optimized, and the reflected light from the absolute scale 9SA to the photodetector group 54A of the first detection unit 11A and the photodetector group 54B of the second detection unit 11B is optimized. Therefore, the angle detection unit 4 can detect the rotation angle of the disk 6 with high accuracy and a high signal-to-noise ratio.

[0065] In this way, it is relatively easy to adjust the positions of the first detection unit 11A and the second detection unit 11B in the R direction while monitoring the amplitude of the detection signal. However, in this case, as shown in Figure 13(B), there is a risk that the positions of the first detection unit 11A and the second detection unit 11B in the θ direction will deviate from the target position. For example, the center of the first detection unit 11A (for example, the center of the LED 31A) is shifted by δ1 from the target position in the θ direction, and the center of the second detection unit 11B (for example, the center of the LED 31B) is shifted by δ2 from the target position in the θ direction. This deviation in the θ direction includes errors in the mounting position and mounting angle of the detection units 11A and 11B relative to the substrate 50. As a result, in the first detection unit 11A, the phase difference between the detection signals SA and SB and the detection signals ABX and ABY in Figures 12(A) and (D) is shifted by a predetermined first angular error from the target value (e.g., 0), and in the second detection unit 11B, the phase difference between the detection signal obtained from the incremental scale 9SI and the detection signal obtained from the absolute scale 9SA is shifted by a predetermined second angular error from the target value.

[0066] Therefore, in step 164, with respect to the first detection unit 11A, with the phase difference Δθ supplied from the non-volatile memory 74 to the switching signal generation unit 66 set to 0, the phase difference Δθ (corresponding to the first angular error) between the absolute value signal ABS output from the amplifier 58C and the detection signals SA and SB is detected, and the detected phase difference Δθ is stored in the non-volatile memory 74 via the control unit 76. Similarly, with respect to the second detection unit 11B, the phase difference (corresponding to the second angular error) between the detection signals of the photodetectors 32FA and 32FB and the detection signal of the photodetector group 54B is detected, and the detected phase difference is stored in the non-volatile memory in the second circuit unit 48B.

[0067] Subsequently, the encoder device ECB is started, and in step 166, the XY switching signal SXY, corrected by a phase difference Δθ from the switching signal generation unit 66 in Figure 11, is supplied to the selector group 56A in the first detection unit 11A, correcting the angle connecting the two ABS signals ABX and ABY. As a result of this correction, the rotation information of the disk 6 is detected with high accuracy using the absolute value signal ABS, which always has a stable signal level. Similarly, in the second detection unit 11B, the rotation information of the disk 6 is detected with high accuracy by using the XY switching signal SXY corrected in the second circuit unit 48B. Subsequently, if detection is to be continued in step 168, step 166 is repeated.

[0068] Furthermore, in the case where the phase difference Δθ (angle error) is set to 0 without correcting for the phase difference Δθ as in this embodiment (comparative example), the absolute value signal ABS' output from the shift register 56B in Figure 11 exhibits large fluctuations in signal level, as shown in Figure 12(G). Therefore, when the absolute value signal ABS' is binarized, the correct absolute scale 9SA pattern cannot be obtained, and there is a risk of detection errors in the absolute value.

[0069] As described above, the positioning method for the encoder device ECB of this embodiment is a positioning method for an encoder device comprising: a first detection unit 11A that detects light from a pattern 9S provided along the rotational movement direction of a rotating disk 6 (moving part) and outputs first detection signals SA and SB; a second detection unit 11B that is positioned at a predetermined angle away from the first detection unit 211A along the rotational movement direction of the disk 6 and detects light from the pattern 9S and outputs a second detection signal; a detection circuit unit 21 (calculation unit) that determines the rotation information of the disk 6 using the first detection signals SA and SB and the second detection signal; and a substrate 50 (support member) that integrally supports the first detection unit 11A and the second detection unit 11B, and the method includes a step 162 of positioning the first detection unit 11A and the second detection unit 11B in the radial direction of the rotational movement of the disk 6.

[0070] This positioning method makes it easy to position the first detection unit 11A and the second detection unit 11B relative to the disk 6 (pattern 9S) with high precision. Furthermore, the rotational positional misalignment (angle error) of the first detection unit 11A and the second detection unit 11B when positioned radially can be electrically corrected with high precision, for example, by correcting the phase of the detection signal of the reflected light of the absolute scale 9SA within the first detection unit 11A and the second detection unit 11B (the phase of the two absolute value signals ABX and ABY being joined together). In this embodiment, the angle between the two first detection units 11A and the second detection unit 11B is 90°, but this angle may be any angle other than, for example, 180°.

[0071] [Third Embodiment] A third embodiment will be described with reference to Figures 15 and 14(B). In Figure 15, parts corresponding to those in Figures 10(A) to 11 are denoted by the same reference numerals, and their detailed descriptions are omitted. Figure 15 shows the mechanism of the angle detection unit 4A of the encoder device ECC according to this embodiment. In Figure 15, the disk 6 is attached to the disc 5 of the rotation axis SF in Figure 10(B), and an angle detection pattern 9S, including an incremental scale 9SI and an absolute scale 9SA, is formed concentrically around the rotation center on the surface of the disk 6. The angle detection unit 4 has a first detection unit 11A that detects light from the pattern 9S on the disk 6, a second detection unit 11B that detects light from the pattern 9S at different positions, and a detection circuit unit 21A that processes the detection signals from the detection units 11A and 11B to detect an angle θ within one rotation of the disk 6 (rotation axis SF). The configuration of the detection circuit unit 21A is the same as that of the detection circuit unit 21 in Figure 11. In this embodiment, in the rotational direction (θ direction) of the disk 6, the position of the second detection unit 11B is offset from that of the first detection unit 11A by an angle φ (0° < φ < 360°).

[0072] A position output unit 80A is provided within the detection circuit unit 21A, and the rotation angles θA and θB of the disk 6, obtained by processing the detection signals output from the first detection unit 11A and the second detection unit 11B, respectively, are supplied to the position output unit 80A. The position output unit 80A processes the rotation angles θA and θB to determine the rotation angle θT of the disk 6, and supplies the information of the determined rotation angle θT to the synthesis unit 23 in Figure 1. The motor M in Figure 1 is controlled using the rotation angle information obtained by the synthesis unit 23 in Figure 1.

[0073] Next, an example of the detection method for the encoder device ECC of this embodiment will be described with reference to the flowchart in Figure 14(B). First, in step 172 of Figure 14(B), the encoder device is assembled. In the next step 174, for example, while rotating the disk 6 once, the position output unit 80A processes the detection signals output from the first detection unit 11A and the second detection unit 11B, respectively, and acquires information on the rotation angles θA and θB of the disk 6 at a predetermined sampling rate. Then, the position output unit 80A uses the acquired rotation angle information to calculate the detection error for every nth harmonic (n is an integer of 1 or more) as follows. If the rotation angles θA and θB are functions f(θ) and f(θ+φ), respectively, the error of the encoder device returns to its original state when the disk 6 is rotated once (360°), so the functions f(θ) and f(θ+φ) can be expressed using a Fourier series as follows.

[0074]

number

[0075]

number

[0076]

number

[0077] Since the amplitude and phase of each harmonic can be calculated in this way, the error in the detection result can be corrected by correcting the phase shift and amplitude increase / decrease amount at the order n of each harmonic to the comparative measurement value δ(θ). For example, in step 176, the position output unit 80A calculates the amplitude and phase of each harmonic and stores the calculation result in the non-volatile memory (not shown) in the detection circuit unit 21A. Then, in step 178, when detecting the rotation information of the disk 6, the detection result can be corrected using the stored amplitude and phase of each harmonic. If detection is to continue in the next step 180, step 178 is repeated. However, for harmonics of an order that is a multiple of 4, the amplitude becomes 0, so the error cannot be made apparent. Also, for even-order harmonics other than multiples of 4, the error can be canceled in real time by averaging the angle detection values ​​of each detection unit 11A, 11B. This method of performing the Fourier transform requires only one calculation, eliminates the need for repeated calculations, and prevents the accumulation of error residuals, thus enabling highly accurate correction.

[0078] Alternatively, to correct the error in the detection result for each harmonic order without performing Fourier transform calculations, the following processes a1) to a7) may be performed. This method does not require complex calculations (only basic arithmetic operations are needed), and the burden on the detection circuit 21A is reduced. a1) The comparative measurement value δ(θ) (the difference in detection results between detection units 11A and 11B) from equation (3) is acquired for one rotation (one full turn) of disk 6. a2) With respect to the comparative measurement value δ(θ), the phase is (3 / 4)π ahead, +2 1 / 2 Generates a waveform with double the amplitude. Data for slope correction is generated from the waveforms generated in a3) and a2). a4) The data generated in a3) is written to the memory in the detection circuit 21A. At this point, the first harmonic component of the error is canceled out. Simultaneously, the harmonic components of multiples of (8x±1) (x is a natural number starting from 1) also have their phase and amplitude match the original error, so the error is corrected. For errors other than the first harmonic or multiples of (8x±1), the amplitude and phase will be different from the original error curve.

[0079] a5) Similar to a1) to a4), the second harmonic component of the error is corrected. At this point, not only is the second harmonic component of the error canceled out, but the harmonic components of multiples of (8x±2) are also corrected because their phase and amplitude match the error that became the residual in a4) above. The remaining error times will have different amplitudes and phases from the original error curve, but since the errors of the first harmonic and multiples of (8x±1) have already been canceled out, the error amplitudes of the first harmonic and multiples of (8x±1) remain at 0. Similar to a6) and a5), the third harmonic component of the error is also corrected. Similarly, the third harmonic component of the error is canceled out. In addition, the harmonic components that are multiples of (8x±3) are also corrected because their phase and amplitude match the error that became the residual in a4). At this point, the harmonic components other than the fourth (multiple of fourth) are canceled out. a7) For fourth harmonics and harmonics of multiples of fourth order, no correction is necessary because the error does not become apparent.

[0080] Because this method has a low computational load, the detection circuit 21A can be easily constructed. In this method, the amplitude of error components other than the order to be corrected changes, but theoretically, the error amplitude of errors of orders that have already been canceled out becomes 0, so theoretically no problems occur.

[0081] As described above, the ECC encoder device position detection method of this embodiment is a method for detecting the position of an encoder device comprising: a first detection unit 11A that detects light from a pattern 9S provided along the rotational movement direction of a rotating disk 6 (moving part) and outputs first detection signals SA and SB; a second detection unit 11B that is positioned at a predetermined angle away from the first detection unit 211A along the rotational movement direction of the disk 6 and detects light from the pattern 9S and outputs a second detection signal; and a detection circuit unit 21A (calculation unit) that determines the rotation information of the disk 6 using the first detection signals SA and SB and the second detection signal. The method includes steps 174 and 176 to determine the error in the rotation information from the difference between the rotation information of the disk 6 determined from the first detection signal and the rotation information of the disk 6 determined from the second detection signal; and step 178 to determine the rotation information of the disk 6 using the first detection signal, the second detection signal, and the error. This position detection method allows for highly accurate determination of the rotation information of disk 6 (pattern 9S).

[0082] In the above embodiment, the position detection system 2 detects the rotational position information of the rotating axis SF (moving part) as movement information, but it may also detect at least one of the position, velocity, and acceleration in a predetermined direction as movement information. The encoder devices EC, ECA, ECB, and ECC may include rotary encoders or linear encoders. Furthermore, the encoder devices EC, ECA, ECB, and ECC are reflective encoders, but they may also be transmissive encoders.

[0083] [Drive system] An example of a drive device will be described. Figure 16 shows an example of a drive device MTR. In the following description, components that are the same as or equivalent to those in the embodiments described above will be denoted by the same reference numerals, and their descriptions will be omitted or simplified. This drive device MTR is a motor device including an electric motor. The drive device MTR has a rotating shaft SF, a main body (drive unit) BD that rotates the rotating shaft SF, and an encoder device EC that detects the rotational position information of the rotating shaft SF. Note that encoder devices ECA and ECB may be provided instead of encoder device EC (the same applies hereinafter).

[0084] The rotating shaft SF has a load-side end SFa and a non-load-side end SFb. The load-side end SFa is connected to another power transmission mechanism such as a reduction gear. A disk 6 is fixed to the non-load-side end SFb via a fixing part. An encoder device EC is mounted corresponding to this disk 6. The encoder device EC is an encoder device according to the above-described embodiment, modification thereof, or combination thereof.

[0085] In this drive unit MTR, the motor control unit 26 shown in Figure 1 controls the main body BD using the detection results of the encoder unit EC. The drive unit MTR can drive the rotating shaft SF with high precision using the rotation information of the rotating shaft SF detected by the encoder unit EC. Note that the drive unit MTR is not limited to a motor unit, but may be other drive units having a shaft that rotates using hydraulics or pneumatics.

[0086] [Stage equipment] An example of a stage device will be described. Figure 17 shows the stage device STG. This stage device STG has a configuration in which a rotary table (moving object) TB is attached to the load-side end SFa of the rotating shaft SF of the drive device MTR shown in Figure 16. In the following description, components that are the same as or equivalent to those in the above-described embodiment will be denoted by the same reference numerals, and their descriptions will be omitted or simplified.

[0087] The stage device STG drives the drive unit MTR to rotate the rotation shaft SF, and this rotation is transmitted to the rotary table TB. At this time, the encoder device EC detects the angular position of the rotation shaft SF. Therefore, the angular position of the rotary table TB can be detected by using the output from the encoder device EC. A reduction gear or the like may be placed between the load-side end SFa of the drive unit MTR and the rotary table TB.

[0088] The STG stage device can drive the rotation axis SF with high precision using the encoder device EC, thereby enabling high-precision control of the rotary table TB. The STG stage device can be applied, for example, to rotary tables in machine tools such as lathes. [Robot equipment] An example of a robotic device will be described. Figure 18 is a perspective view showing the robotic device RBT. Figure 18 schematically shows a part (joint portion) of the robotic device RBT. In the following description, components that are the same as or equivalent to those in the above-described embodiment will be given the same reference numerals, and their descriptions will be omitted or simplified. This robotic device RBT has a first arm AR1, a second arm AR2, and a joint JT. The first arm AR1 is connected to the second arm AR2 via the joint JT.

[0089] The first arm AR1 comprises an arm portion 91, a bearing 91a, and a bearing 91b. The second arm AR2 comprises an arm portion 92 and a connecting portion 92a. The connecting portion 92a is located between the bearing 91a and the bearing 91b in the joint portion JT. The connecting portion 92a is integrally provided with the rotating shaft SF2. The rotating shaft SF2 is inserted into both the bearing 91a and the bearing 91b in the joint portion JT. The end of the rotating shaft SF2 that is inserted into the bearing 91b passes through the bearing 91b and is connected to the reduction gear RG.

[0090] The reduction gear RG is connected to the drive unit MTR and reduces the rotation of the drive unit MTR to, for example, 1 / 100th of its original speed before transmitting it to the rotating shaft SF2. Although not shown in Figure 18, the load-side end SFa of the rotating shaft SF of the drive unit MTR is connected to the reduction gear RG. In addition, the disk 6 of the encoder device EC is attached to the non-load-side end SFb of the rotating shaft SF of the drive unit MTR.

[0091] When the robotic device RBT drives the drive unit MTR to rotate the rotating shaft SF, this rotation is transmitted to the rotating shaft SF2 via the reduction gear RG. The rotation of the rotating shaft SF2 causes the connecting part 92a to rotate together, thereby causing the second arm AR2 to rotate relative to the first arm AR1. At this time, the encoder device EC detects the angular position of the rotating shaft SF, etc. Therefore, the angular position of the second arm AR2 can be detected from the output of the encoder device EC.

[0092] The robotic robot (RBT) can perform high-precision positioning using the encoder device (EC). However, the RBT is not limited to the above configuration; the drive device (MTR) can be applied to various robotic devices equipped with joints.

[0093] This specification also describes the following embodiments of the invention. 1) A first detection unit that irradiates light onto a pattern of a moving part, detects the light from the pattern, and outputs a first detection signal and a second detection signal that are in phase with respect to the movement of the moving part; and a second detection unit that is positioned at a different location from the first detection unit along the direction of movement of the moving part, irradiates light onto the pattern, detects the light from the pattern, and outputs a third detection signal. A control unit that switches between a state in which movement information of the moving part is obtained using the first detection signal and the second detection signal, and a state in which movement information is obtained using either the first detection signal or the second detection signal and the third detection signal, An encoder device comprising: a calculation unit that determines the movement information based on a detection signal of a state switched by the control unit. 2) The encoder device according to claim 1, wherein the second detection unit outputs a third detection signal that is in phase with one of the first detection signal and the second detection signal with respect to the movement of the moving unit. 3) The pattern includes a plurality of sub-patterns arranged at different positions on the moving part with respect to the direction of movement of the moving part, The encoder device according to claim 1 or 2, wherein the first detection unit and the second detection unit are arranged relative to the moving unit in a positional relationship corresponding to the positional relationship of the pattern. 4) The moving part rotates around the axis of the rotation shaft, The first detection signal and the second detection signal have different phases depending on the positional relationship. The encoder device according to any one of items 1 to 3, wherein the calculation unit detects multi-rotation information of the rotating shaft based on the first detection signal and the second detection signal. 5) The pattern includes a first pattern and a second pattern arranged at different positions along the direction of movement of the moving part, The encoder device according to any one of claims 1 to 4, wherein the two detection signals having different phases include a first detection signal generated by the first detection unit detecting light from the first pattern and a third detection signal generated by the second detection unit detecting light from the first pattern. 6) The encoder device according to any one of items 1 to 5, wherein the calculation unit obtains movement information of the moving part by changing one of the first detection signal and the second detection signal to the third detection signal based on the first detection signal and the second detection signal. 7) The encoder device according to 6, wherein the calculation unit determines the movement information using the third detection signal based on the combination of the states of the detection signal of the first detection unit and the detection signal of the second detection unit. 8) The encoder device according to 6, wherein the calculation unit determines the movement information using the third detection signal based on the state transitions of the detection signal of the first detection unit and the detection signal of the second detection unit. 9) An encoder device as described in any one of items 1 to 8, A power supply unit that supplies power to the moving part, A drive device equipped with the following features. 10) Moving object and, A stage apparatus comprising the drive device described in 9 for moving the aforementioned moving object. 11)9 The drive device described above, A robotic device comprising an arm that moves relative to another by the aforementioned drive device. 12) A first detection unit that irradiates light onto a pattern of a moving part, detects the light from the pattern, and outputs a first detection signal and a second detection signal that are in phase with respect to the movement of the moving part, A second detection unit is positioned at a different location relative to the first detection unit along the direction of movement of the moving unit, irradiates the pattern with light, detects the light from the pattern, and outputs a third detection signal. A method for using an encoder device comprising: a calculation unit that determines movement information of a moving part using two detection signals from among the first detection signal, the second detection signal, and the third detection signal, which have different phases with respect to the movement of the moving part; The system switches between a state in which the position information of the moving part is determined by the first detection signal and the second detection signal, and a state in which the movement information is determined by either the first detection signal or the second detection signal and the third detection signal. A method for using an encoder device, which includes obtaining movement information of the moving part based on a detection signal of the switched state. 13) A method of using the encoder device according to 12, which includes determining the movement information using the third detection signal based on a combination of the states of the first detection signal and the second detection signal. 14) A method of using the encoder device according to 12, which includes determining the movement information using the third detection signal based on the state transition between the first detection signal and the second detection signal.

[0094] 15) A first detection unit that detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal, A second detection unit is positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving unit, and detects light from the pattern and outputs a second detection signal. A calculation unit that obtains rotation information of the moving part based on the first detection signal and the second detection signal, A positioning method for an encoder device comprising a support member that integrally supports the first detection unit and the second detection unit, The first detection unit and the second detection unit are positioned in the radial direction of the rotational movement of the moving unit, A positioning method for an encoder device, including the following: 16) The positioning method for the encoder device according to 15, wherein the predetermined angle is 90°. 17) A method for detecting the position of an encoder device positioned by the positioning method described in 15 or 16, The first detection signal and the second detection signal each include an incremental signal and an absolute signal, In the calculation unit, the phase of the absolute signal is corrected with reference to the incremental signal of the first detection signal, and the phase of the absolute signal is corrected with reference to the incremental signal of the second detection signal. A method for detecting the position of an encoder device, further including the method described above. 18) The method for detecting the position of an encoder device according to 17, wherein the incremental signal includes two phase signals with a phase difference of 90°, the absolute signal includes two signals, and correcting the phase of the absolute signal includes correcting the angle at which the two signals of the absolute signal are joined together. 19) A first detection unit that detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal with respect to the rotational movement of the moving part, A second detection unit is positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving unit, and detects light from the pattern and outputs a second detection signal. A position detection method for an encoder device comprising: a calculation unit that determines rotation information of the moving part based on the first detection signal and the second detection signal; The error in the rotation information is determined from the difference between the rotation information of the moving part obtained from the first detection signal and the rotation information of the moving part obtained from the second detection signal. A method for detecting the position of an encoder device, comprising determining rotation information of the moving part using the first detection signal, the second detection signal, and the error. 20) The method for detecting the position of an encoder device according to 19, wherein determining the error includes determining the error for each order of the fundamental wave and harmonics, with one period being 360° of the rotation angle of the moving part. 21) A method for detecting the position of an encoder device according to 19 or 20, wherein the first detection signal and the second detection signal each include an incremental signal and an absolute signal. 22) A method for detecting the position of an encoder device according to any one of items 19 to 21, wherein the predetermined angle is 90°. [Explanation of Symbols]

[0095] 2…Position detection system, 3…Multi-turn information detection unit, 4…Angle detection unit, 6…Disk, 8A~8D…Semi-circular pattern, 10A…First detection unit, 10B…Second detection unit, 11A…First detection unit, 11B…Second detection unit, 13…Control unit, 14…Storage unit, 15…Battery, 22…Signal synthesis unit, 26…Motor control unit, 31,34…LED, 32A~32E,35A~35E…Photodetector, 33A,33B,36A,36B…Analog comparator, 39…Light emission control unit, 40…Calculation control unit, EC,ECA,ECB,ECC…Encoder device, SF…Rotation axis, M…Motor, AR1…First arm, AR2…Second arm, MTR…Drive device, RBT…Robot device, STG…Stage device

Claims

1. A first detection unit detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal, A second detection unit is positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving unit, and detects light from the pattern and outputs a second detection signal. A calculation unit that obtains rotation information of the moving part based on the first detection signal or the second detection signal, A positioning method for an encoder device comprising a support member that integrally supports the first detection unit and the second detection unit, Position the first detection unit and the second detection unit in the radial direction of the rotational movement of the moving unit, A positioning method for an encoder device, including the following:

2. The positioning method for an encoder device according to claim 1, wherein the predetermined angle is 90°.

3. The positions of the first detection unit and the second detection unit are adjusted in the radial direction of the rotational movement of the moving unit to match the position of the pattern of the moving unit. A positioning method for an encoder device according to claim 1 or 2.

4. While rotating the movable part, the first detection signal and the second detection signal are monitored. The radial position of the rotational movement of the moving part relative to the first detection unit is adjusted so that the first detection signal is maximized. After adjusting the position relative to the first detection unit, the radial position of the rotational movement of the moving unit relative to the second detection unit is adjusted so that the second detection signal is maximized. A positioning method for an encoder device according to any one of claims 1 to 3.

5. A method for detecting the position of an encoder device positioned by the positioning method described in any one of claims 1 to 4, The first detection signal and the second detection signal each include an incremental signal and an absolute signal, In the calculation unit, the phase of the absolute signal is corrected with reference to the incremental signal of the first detection signal, and the phase of the absolute signal is corrected with reference to the incremental signal of the second detection signal. A method for detecting the position of an encoder device, further including the method described above.

6. The method for detecting the position of an encoder device according to claim 5, wherein the incremental signal includes two phase signals with a phase difference of 90°, the absolute signal includes two signals, and correcting the phase of the absolute signal includes correcting the angle at which the two signals of the absolute signal are joined together.

7. A first detection unit detects light from a pattern provided along the direction of movement of a rotating moving part and outputs a first detection signal with respect to the rotational movement of the moving part. A second detection unit is positioned at a predetermined angle away from the first detection unit along the direction of movement of the moving unit, and detects light from the pattern and outputs a second detection signal. A position detection method for an encoder device comprising: a calculation unit that determines rotation information of the moving part based on the first detection signal and the second detection signal; The error in the rotation information is determined from the difference between the rotation information of the moving part obtained from the first detection signal and the rotation information of the moving part obtained from the second detection signal. A method for detecting the position of an encoder device, comprising obtaining rotation information of the moving part using the first detection signal, the second detection signal, and the error.

8. The method for detecting the position of an encoder device according to claim 7, wherein determining the aforementioned error includes determining the error for each order of the fundamental wave and harmonics, with one period being 360° of the rotation angle of the moving part.

9. The method for detecting the position of an encoder device according to claim 7 or 8, wherein the first detection signal and the second detection signal each include an incremental signal and an absolute signal.

10. The method for detecting the position of an encoder device according to any one of claims 7 to 9, wherein the predetermined angle is 90°.

Images