Robot system, torque sensor, displacement detection device, detection method, product manufacturing method, and recording medium

Abstract

A robot system, a torque sensor, a displacement detection device, a detection method, a product manufacturing method, and a recording medium are disclosed. The robot system includes a robot including a reduction gear and an encoder, and a processing portion configured to obtain a torque value by using phase information based on a detection signal of the encoder. The encoder includes a scale including a pattern portion, and a head portion configured to read the pattern portion of the scale and output the detection signal. The processing portion is configured to obtain a first displacement amount of the scale in a first direction that is a relative direction with respect to the head portion. The processing portion is configured to obtain a second displacement amount of the scale in a second direction that is a relative direction with respect to the head portion and intersects the first direction. The processing portion is configured to obtain the torque value based on the first displacement amount and the second displacement amount.

Description

TECHNICAL FIELD

[0001] The present application relates to sensing technology. BACKGROUND

[0002] In a production line in a factory or the like, an industrial robot is installed to improve the productivity of a product to be manufactured. Examples of the industrial robot include a collaborative robot capable of cooperating with an operator. Japanese Patent Publication No. 2020-104249 discloses an industrial robot including a torque sensor for detecting contact with an operator or an object.

[0003] The torque sensor includes a displacement detection device such as an encoder device, and obtains a torque value by using displacement information detected by the displacement detection device. In recent years, driving devices such as robots have begun to require precise operation, and thus the torque sensor, i.e., the displacement detection device, has begun to require high detection accuracy. SUMMARY

[0004] According to a first aspect of the present application, a robot system includes: a robot including a reduction gear and at least one encoder in a joint thereof; and a processing portion configured to obtain a torque value by using phase information based on a detection signal of the encoder. The encoder includes: a scale including a pattern portion, and a head portion disposed opposite the scale and configured to read the pattern portion of the scale and output the detection signal. The processing portion is configured to obtain a first displacement amount of the scale in a first direction and a second displacement amount of the scale in a second direction based on the phase information. The first direction is a relative direction with respect to the head portion. The second direction is a relative direction with respect to the head portion and intersecting the first direction. The processing portion is configured to obtain the torque value based on the first displacement amount and the second displacement amount.

[0005] According to a second aspect of the present application, a robot system includes: a robot including a reduction gear and at least one encoder in a joint thereof; a processing portion configured to obtain a torque value by using phase information based on a detection signal of the encoder; and a storage portion configured to store a correction value associated with trajectory data of the robot. The encoder includes: a scale including a pattern portion; and a head portion disposed opposite the scale and configured to read the pattern portion of the scale and output the detection signal. The processing portion is configured to obtain a first displacement amount of the scale in a first direction that is a relative direction with respect to the head portion based on the phase information obtained when the robot operates according to the trajectory data, and obtain the torque value based on displacement information obtained by correcting the first displacement amount using the correction value corresponding to the trajectory data.

[0006] According to a third aspect of the present application, a torque sensor includes at least one encoder disposed in a drive device, and a processing portion configured to obtain a torque value by using phase information based on a detection signal of the encoder. The encoder includes a scale including a pattern portion, and a head portion disposed opposite to the scale and configured to read the pattern portion of the scale and output the detection signal. The processing portion is configured to obtain a first displacement amount of the scale in a first direction and a second displacement amount of the scale in a second direction based on the phase information. The first direction is a relative direction with respect to the head portion. The second direction is a relative direction with respect to the head portion and intersecting the first direction. The processing portion is configured to obtain the torque value based on the first displacement amount and the second displacement amount.

[0007] According to a fourth aspect of the present application, a torque sensor includes at least one encoder disposed in a drive device including a reduction gear, and a processing portion configured to obtain a torque value by using phase information based on a detection signal of the encoder. The encoder includes a scale including a pattern portion, and a head portion disposed opposite to the scale and configured to read the pattern portion of the scale and output the detection signal. The processing portion is configured to obtain a first displacement amount of the scale in a first direction which is a relative direction with respect to the head portion based on the phase information obtained when the drive device operates according to trajectory data, and obtain the torque value based on displacement information obtained by correcting the first displacement amount using a correction value corresponding to the trajectory data.

[0008] According to a fifth aspect of the present application, a displacement detection device includes at least one encoder disposed in a drive device including a reduction gear, and a processing portion configured to obtain displacement information by using phase information based on a detection signal of the encoder. The encoder includes a scale including a pattern portion, and a head portion disposed opposite to the scale and configured to read the pattern portion of the scale and output the detection signal. The processing portion is configured to obtain a first displacement amount of the scale in a first direction and a second displacement amount of the scale in a second direction based on the phase information. The first direction is a relative direction with respect to the head portion. The second direction is a relative direction with respect to the head portion and intersecting the first direction. The processing portion is configured to obtain the displacement information based on the first displacement amount and the second displacement amount.

[0009] According to a sixth aspect of the invention, a displacement detection device includes: at least one encoder deployed in a drive device including a reduction gear; and a processing unit configured to obtain displacement information in a first direction by using phase information based on a detection signal from the encoder. The encoder includes: a scale including a patterned portion; and a head deployed opposite to the scale and configured to read the patterned portion of the scale and output a detection signal. The processing unit is configured to obtain a first displacement of the scale in the first direction, which is a direction relative to the head, based on phase information obtained when the drive device operates according to trajectory data, and to obtain displacement information by correcting the first displacement by using a correction value corresponding to the trajectory data.

[0010] According to a seventh aspect of the present invention, a detection method for obtaining a torque value using a torque sensor is provided. The torque sensor includes an encoder and a processing unit. The encoder is deployed in a drive device including a reduction gear. The encoder includes a scale and a head. The scale includes a patterned portion. The head is deployed opposite to the scale. The head is configured to read the patterned portion of the scale and output a detection signal. The processing unit is configured to obtain the torque value using phase information based on the detection signal. The detection method includes the processing unit obtaining a first displacement of the scale in a first direction and a second displacement of the scale in a second direction based on the phase information. The first direction is a direction relative to the head. The second direction is a direction relative to the head and intersecting the first direction. The detection method includes the processing unit obtaining the torque value based on the first and second displacements.

[0011] According to an eighth aspect of the present invention, a detection method for obtaining a torque value using a torque sensor is provided. The torque sensor includes an encoder and a processing unit. The encoder is deployed in a drive device including a reduction gear. The encoder includes a scale and a head. The scale includes a patterned portion. The head is deployed opposite to the scale. The head is configured to read the patterned portion of the scale and output a detection signal. The processing unit is configured to obtain the torque value using phase information based on the detection signal. The detection method includes obtaining a first displacement of the scale in a first direction relative to the head using phase information obtained by the processing unit when the drive device operates according to trajectory data. The detection method also includes obtaining the torque value by the processing unit based on displacement information obtained by correcting the first displacement using a correction value corresponding to the trajectory data.

[0012] Other features of the invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0013] Figure 1 This is an illustrative diagram of a robot system according to the first embodiment.

[0014] Figure 2 This is a partial cross-sectional view of a robot system with a joint of a robotic arm according to a first embodiment.

[0015] Figure 3 This is a block diagram illustrating the control system of the joints of the robotic arm according to the first embodiment.

[0016] Figure 4 This is a perspective view of the torque sensor according to the first embodiment.

[0017] Figure 5A This is a block diagram illustrating the configuration of the torque sensor according to the first embodiment.

[0018] Figure 5B This is a block diagram illustrating the function of the torque sensor according to the first embodiment.

[0019] Figure 6A This is a schematic diagram of an encoder device used as an example of a displacement detection device according to the first embodiment.

[0020] Figure 6B This is a plan view of the sensor head according to the first embodiment.

[0021] Figure 7A This is an illustrative diagram of a torque sensor according to the first embodiment.

[0022] Figure 7B This is an illustrative diagram of a torque sensor according to the first embodiment.

[0023] Figure 8 This is an illustrative diagram of the scale according to the first embodiment.

[0024] Figure 9 This is a plan view of the optical receiving element array according to the first embodiment.

[0025] Figure 10 This is a circuit diagram of the circuit section of the signal processing circuit according to the first embodiment.

[0026] Figure 11A This is a flowchart illustrating an example of a robot control method according to a first embodiment.

[0027] Figure 11B This is a flowchart illustrating an example of a torque detection method according to the first embodiment.

[0028] Figure 12 It is a graph illustrating the relationship between the phase and the scale position according to the first embodiment.

[0029] Figure 13AThis is an illustrative diagram illustrating the principle of the first embodiment.

[0030] Figure 13B This is an illustrative diagram illustrating the principle of the first embodiment.

[0031] Figure 13C This is a schematic diagram of the Lissajous waveform according to the first embodiment.

[0032] Figure 14 It is a graph illustrating the relationship between the difference and the displacement according to the first embodiment.

[0033] Figure 15 It is a planar diagram of the scale in the modified example.

[0034] Figure 16A This is a schematic diagram of an encoder device used as an example of a displacement detection device according to the second embodiment.

[0035] Figure 16B This is a plan view of the sensor head according to the second embodiment.

[0036] Figure 17 This is an illustrative diagram of the scale according to the second embodiment.

[0037] Figure 18 This is a plan view of the optical receiving element array according to the second embodiment.

[0038] Figure 19 This is a plan view of the optical receiving element array according to the second embodiment.

[0039] Figure 20A This is a schematic diagram of an encoder device used as an example of a displacement detection device according to the third embodiment.

[0040] Figure 20B This is a plan view of the sensor head according to the third embodiment.

[0041] Figure 21 This is an illustrative diagram of the scale according to the third embodiment.

[0042] Figure 22A This is a flowchart illustrating the preprocessing in the robot system according to the third embodiment.

[0043] Figure 22B This is a flowchart illustrating an example of a torque detection method according to a third embodiment. Detailed Implementation

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0045] First Embodiment

[0046] Figure 1 This is an illustrative diagram of the robot system 100 according to the first embodiment. (See diagram for reference.) Figure 1 As illustrated in the diagram, the robot system 100 includes a robot 200 and a robot control device 300. The robot 200 is an industrial robot used for manufacturing products. The robot 200 is capable of performing operations for manufacturing products, such as gripping a first workpiece W1 and mounting the gripped first workpiece W1 onto a second workpiece W2.

[0047] Robot control device 300 serves as an example of a control unit and controls robot 200. A teaching pendant 400, serving as an example of a teaching device, can be connected to robot control device 300. Teaching pendant 400 is a device used to teach robot 200 and outputs teaching data to robot control device 300. Robot control device 300 generates trajectory data based on the teaching data and operates robot 200 according to the trajectory data.

[0048] Robot 200 includes a robotic arm 201 and a manipulator 202, which serves as an example of an end effector. The robotic arm 201 is, for example, a vertically hinged robotic arm. A fixed end 201A, serving as the proximal end of the robotic arm 201, is fixed to a support 150. The robotic arm 202 is attached to a free end 201B, serving as the distal end of the robotic arm 201. The robotic arm 201 includes a plurality of links 210, 211, 212, and 213, and the links 210 to 213 are rotatably interconnected via joints J1, J2, and J3. Each of the joints J1 to J3 of the robotic arm 201 is provided with a drive device 230. The drive device 230 for each of the joints J1 to J3 uses a drive device with an appropriate output matched to the required torque.

[0049] In the robotic arm 201, joint J1 will be described as an example, and the descriptions of other joints J2 and J3 will be omitted because these joints have a similar configuration to joint J1, although their size and performance may differ.

[0050] Figure 2This is a partial cross-sectional view of the robotic arm 201 according to the first embodiment, illustrating joint J1. The drive device 230 includes a motor 141 serving as a rotational drive source, a reduction gear 143 coupled to a rotating shaft 142 of the motor 141 and outputting reduced rotation of the rotating shaft 142, and a torque sensor 500. The rotating shaft 142 of the motor 141 rotates about a rotation axis C0. Links 210 and 211 are rotatably coupled to each other via crossed roller bearings 147. The motor 141 is a servo motor, for example, a brushless DC servo motor or an AC servo motor. The reduction gear 143 in the first embodiment is a strain wave reduction gear. The reduction gear 143 includes, for example, a waveform generator 151 coupled to the rotating shaft 142 of the motor 141 and serving as an input shaft, and, for example, a rigid gear 152 fixed to the link 211 and serving as an output shaft. Note that although the rigid gear 152 is coupled to the link 211, the rigid gear 152 can be integrally formed with the link 211. Additionally, the reduction gear 143 includes a flexible gear 153 disposed between the waveform generator 151 and the rigid gear 152 and coupled to the connecting rod 210 via a torque sensor 500. The flexible gear 153 is formed in a cup shape. The flexible gear 153 is twisted into an elliptical shape by the waveform generator 151 and engages with the rigid gear 152 at the major axis portion of its elliptical shape. When the waveform generator 151 rotates, the major axis portion of the elliptical shape of the flexible gear 153 rotates, and the engagement position between the flexible gear 153 and the rigid gear 152 moves in the rotational direction of the waveform generator 151. Each time the waveform generator 151 rotates once, the rigid gear 152 rotates relative to the flexible gear 153 by an amount corresponding to the difference in the number of teeth between the flexible gear 153 and the rigid gear 152. As a result, the speed of the rigid gear 152 decreases relative to the rotation of the waveform generator 151 by a predetermined reduction ratio and rotates relative to the flexible gear 153. Therefore, the connecting rod 211 coupled to the rigid gear 152 rotates relative to the connecting rod 210 coupled to the flexible gear 153 via the torque sensor 500 about the rotation axis C0.

[0051] A torque sensor 500 is deployed on the flexible gear 153 on the output side of the reduction gear 143. Specifically, the torque sensor 500 is deployed between the link 210 and the flexible gear 153 of the reduction gear 143, that is, between link 210 (used as an example of a first link) and link 211 (used as an example of a second link). Furthermore, the torque sensor 500 measures the torque acting between link 210 and link 211 about the rotation axis C0 and outputs an electrical signal corresponding to the measured torque value to the robot control device 300. The electrical signal is a digital signal. The robot control device 300 controls the robot 200 based on the torque value.

[0052] Figure 3This is a block diagram illustrating the control system of joint J1 of the robotic arm 201 according to the first embodiment. The drive device 230 includes a drive control device 260 electrically connected to the motor 141 and the robot control device 300. A torque sensor 500 of the drive device 230 is electrically connected to the robot control device 300.

[0053] The robot control device 300 controls the entire robot system holistically. Specifically, the robot control device 300 controls the operation of the robot 200. The control of the robot 200's operation includes position control and force control. In position control, the robot control device 300 generates operation commands based on the position of the robot 200's hand tips and outputs the generated operation commands to the drive control device 260. In force control, the robot control device 300 generates operation commands based on the torque value received as a measurement from the torque sensor 500 and outputs the generated operation commands to the drive control device 260. The drive control device 260 executes power supply control of the motor 141 according to the operation commands, thus driving the motor 141. In force control, the robot control device 300 operates the robot 200 based on the torque value output from the torque sensor 500. Therefore, the performance of the robot 200's force control depends on accuracy, i.e., the resolution of the torque sensor 500.

[0054] Figure 4 This is a perspective view of a torque sensor 500 according to a first embodiment. The torque sensor 500 includes a sensor body 590 and an arithmetic processing unit 600. The sensor body 590 includes a support portion 501 and a support portion 502, the support portion 501 serving as a fastener and thus a fixed component. Figure 2 The illustration shows an example of the first component of the reduction gear 143, and the support 502 serves as a fastener and thus a fixation to... Figure 2 An example of the second component of the connecting rod 210 shown in the figure.

[0055] Supports 501 and 502 are each flat plate-shaped components, and as... Figure 4 The diagram illustrates a ring shape, for example, centered on the rotation axis C0. Support 502 is displaceable relative to support 501 in a rotational direction centered on the rotation axis C0. Note that the shape of each of supports 501 and 502 is not limited to this and can be, for example, disc-shaped. Supports 501 and 502 form flange portions, which can be fixed to reduction gear 143 and connecting rod 210 respectively by bolts or the like. Supports 501 and 502 are spaced apart in the Z direction so as to face each other and are coupled to each other via elastic portion 503, the Z direction being the direction in which the rotation axis C0 extends.

[0056] The elastic part 503 includes a plurality of spring plates 504 arranged radially at intervals around the rotation axis C0. When torque is applied...Figure 2 When the connecting rods 210 and 211 in the diagram are in contact, the support portion 502 rotates relative to the support portion 501 about the rotation axis C0 by an amount of rotation corresponding to the magnitude of the applied torque. The spring plates 504 are each formed of a material having an elastic modulus (i.e., a spring modulus corresponding to the target torque and the required resolution measurement range). The elastic portion 503 is made of, for example, resin or metal, and preferably metal. Examples of metals include steel and stainless steel. In the first embodiment, the support portions 501, 502, and 503 are all formed of the same material and are integrally formed. The support portions 501, 502, and 503 do not necessarily need to be integrally formed.

[0057] The sensor body 590 includes at least one encoder for measuring the relative displacement between supports 501 and 502, i.e., the torque acting between supports 501 and 502. The at least one encoder is preferably a plurality of encoders. The plurality of encoders is preferably four encoders 510. That is, in the first embodiment, the sensor body 590 includes four encoders 510. All four encoders 510 have the same configuration. The four encoders 510 are arranged at equal intervals at positions symmetrically about the rotation axis C0 at 90 degrees. It should be noted that although the number of encoders 510 included in the sensor body 590 is preferably four, the configuration is not limited to this. The number of encoders 510 included in the sensor body 590 can be one, two, three, five, or more. Each encoder 510 is an incremental encoder. Although incremental encoders will be described as examples in this embodiment, encoders can be of an absolute type. Furthermore, each encoder 510 is preferably an optical encoder, an electrostatic capacitive encoder, or a magnetic encoder. Among these, optical encoders are more preferred because they can achieve higher detection resolution. Therefore, in the first embodiment, each encoder 510 is an optical encoder.

[0058] Each encoder 510 can be either a linear encoder or a rotary encoder. The relative displacement between the supports 501 and 502 in the rotational direction about the rotational axis C0 is small and can be considered as the displacement of each encoder 510 in the translational direction. Therefore, in the first embodiment, each encoder 510 is a linear encoder. Each encoder 510 is capable of detecting the relative displacement between the supports 501 and 502 in the rotational direction about the rotational axis C0 (i.e., in the tangential direction).

[0059] Encoder 510 each includes a scale 2 and a sensor head 7, the sensor head 7 serving as an example of a head deployed opposite to the scale 2. The sensor head 7 is a sensor unit. The scale 2 is fixed to and supported by one of the supports 501 and 502. In a first embodiment, the scale 2 is fixed to and supported by the support 501. The sensor head 7 is fixed to and supported by the other of the supports 501 and 502. In a first embodiment, the sensor head 7 is fixed to and supported by the support 502. Note that the scale 2 can be supported by the support 502, and the sensor head 7 can be supported by the support 501. By using encoder 510, the relative displacement between supports 501 and 502 can be measured as a relative quantity relative to a certain standard position.

[0060] Figure 5A This is a block diagram illustrating the configuration of the torque sensor 500 according to the first embodiment. The arithmetic processing unit 600 includes the same number of signal processing circuits 50 as the encoder 510 (e.g., four signal processing circuits 50) and a computer 650 connected to the four signal processing circuits 50. The computer 650 is, for example, a microcomputer. An example configuration of the computer 650 will be described below.

[0061] Computer 650 includes a central processing unit (CPU) 651, which serves as an example of a processor used as a processing unit. Additionally, computer 650 includes a read-only memory (ROM) 652 storing a program 620 for causing CPU 651 to perform arithmetic operations to obtain a torque value τ, and a random access memory (RAM) 653 for temporarily storing data, etc. Furthermore, computer 650 includes I / O 654, which is an interface to signal processing circuitry 50 and external devices connected thereto, such as robot control device 300 and external storage devices (not shown). CPU 651, ROM 652, RAM 653, and I / O 654 are communicatively interconnected via bus 660.

[0062] The torque value τ is torque information—that is, torque data—and can be a standardized value. The CPU 651 obtains phase information from each signal processing circuit 50, obtains the torque value τ by performing arithmetic processing according to program 620, and outputs the obtained torque value τ to the robot control device 300.

[0063] In this embodiment, storage device 670 includes ROM 652 and RAM 653, and serves as an example of a storage unit. It should be noted that the configuration of storage device 670 is not limited to this. Furthermore, storage device 670 can be an internal storage device, an external storage device, or a combination of internal and external storage devices.

[0064] Furthermore, although in this embodiment the ROM 652 is a non-transitory recording medium readable by the computer 650 and the ROM 652 stores the program 620, the configuration is not limited to this. The program 620 can be recorded on any recording medium, as long as the recording medium is a non-transitory recording medium readable by the computer 650. In addition, as a recording medium for supplying the program 620 to the computer 650, for example, a floppy disk, optical disk, magneto-optical disk, magnetic tape, and non-volatile memory can be used.

[0065] The arithmetic processing unit 600 obtains relative displacement information between the supports 501 and 502 based on a detection signal, which is an encoder signal from the sensor head 7 of each encoder 510. Then, the arithmetic processing unit 600 converts the obtained displacement information into a torque value τ and outputs the torque value τ to the robot control device 300.

[0066] Figure 5B This is a block diagram illustrating the function of the torque sensor 500 according to the first embodiment.

[0067] The torque sensor 500 includes multiple (e.g., four) encoder devices 550, which are examples of multiple displacement detection devices. Each encoder device 550 includes an encoder 510, a signal processing circuit 50, and... Figure 5A The diagram shows some of the functions of computer 650. When... Figure 5A When CPU 651 executes program 620 as shown in the diagram, CPU 651 is used as... Figure 5B The diagram shows each displacement calculation unit 680 and torque calculation unit 681. Specifically, CPU 651 serves as the displacement calculation unit 680 for each encoder device 550. Additionally, CPU 651 serves as the torque calculation unit 681 for the torque sensor 500. The torque calculation unit 681 calculates the torque value τ using phase Φ10, which is displacement information calculated by each displacement calculation unit 680. The arithmetic processing of phase Φ10 performed by each displacement calculation unit 680 will be described subsequently. Phase Φ10 is the relative displacement information of the support portion 501 relative to the support portion 502, derived from the elastic deformation of the elastic portion 503 caused by the torque acting on the sensor body 590, and does not include the elastic deformation of the support portion 501.

[0068] Figure 6AThis is a schematic diagram of the encoder device 550 according to the first embodiment. The scale 2 is translated relative to the sensor head 7 in the X direction. The direction of movement of the scale 2 relative to the sensor head 7 is referred to as the X direction, the direction intersecting the X direction is referred to as the Y direction, and the direction intersecting both the X and Y directions is referred to as the Z direction. The X, Y, and Z directions are preferably perpendicular to each other. The X direction is a tangential direction. The Y direction is a radial direction. The X direction serves as an example of a first direction, and the Y direction serves as an example of a second direction. The X direction is also the position measurement direction of the encoder 510. Figure 6A The scale 2 and sensor head 7 are schematically illustrated as seen in the X direction. Additionally, Figure 6B This is a plan view of the sensor head 7 according to the first embodiment. Figure 6B The sensor head 7 is schematically illustrated as seen in the Z direction.

[0069] Encoder 510 is an optical encoder of the interferometric type and is an incremental linear encoder. Additionally, although encoder 510 is reflective in the first embodiment, it can also be transmissive. CPU 651 performs processes such as inserting the detection signal S obtained from sensor head 7, writing information to and reading information from storage device 670, and outputting position signals.

[0070] The sensor head 7 is positioned in the Z direction opposite to the scale 2. The scale 2 has a patterned portion 80. The sensor head 7 reads the patterned portion 80 of the scale 2 and outputs a detection signal S to the signal processing circuit 50. The sensor head 7 includes a light source 1 composed of a light-emitting diode (LED) as an example of a light-emitting unit, and two light-receiving units 31 and 32. The light-receiving units 31 and 32 are arranged in the Y direction at a distance from the light source 1. In the first embodiment, the light source 1 is positioned between the two light-receiving units 31 and 32. It should be noted that although it is preferable to use the same unit for the light-receiving units 31 and 32 because the same parts can be used and the cost can be reduced, different types of light-receiving units suitable for the respective modulation periods of the tracks read by the light-receiving units can be used.

[0071] Light receiving unit 31 includes a light receiving element array 91, and light receiving unit 32 includes a light receiving element array 92. Light source 1 and light receiving units 31 and 32 are mounted on printed wiring board 4 and sealed by a transparent resin 5 that allows light to pass through. Transparent glass 6 that allows light to pass through is disposed on the surface of resin 5. According to this configuration, light source 1 and light receiving units 31 and 32 are protected by resin 5 and glass 6.

[0072] The signal processing circuit 50 is composed of semiconductor elements, such as integrated circuit chips (IC chips). The signal processing circuit 50 is mounted on, for example, the surface of a printed circuit board 4. It should be noted that the location of the signal processing circuit 50 is not limited to this, and the signal processing circuit 50 can be deployed at a location different from its position on the printed circuit board 4. Figure 6A For ease of description, the signal processing circuit 50 is positioned differently from its location on the printed circuit board 4. The signal processing circuit 50 includes a circuit section 511 for processing the detection signal S1 obtained from the photodetector array 91 and a circuit section 512 for processing the detection signal S2 obtained from the photodetector array 92. The detection signals S1 and S2 are included in the detection signal S.

[0073] like Figure 6A As illustrated, pattern portion 80 includes two scale tracks 81 and 82. The two scale tracks 81 and 82 are arranged side-by-side in the Y direction. A diverging light beam emitted from light source 1 radiates diagonally onto scale tracks 81 and 82 of scale 2. The light beams reflected by scale tracks 81 and 82 are reflected respectively toward light receiver arrays 91 and 92. Each reflected light is incident diagonally onto each light receiver array 91 and 92. The reflected light, having a light intensity distribution, is received as an image on each of the light receiver arrays 91 and 92. Specifically, the amount of light received by light receiver arrays 91 and 92 is smaller in the Y direction at positions farther from light source 1.

[0074] The light beams received by the light receiving element arrays 91 and 92 are converted into electrical signals. The electrical signals are transmitted as detection signals S1 and S2 to the circuit sections 511 and 512 of the signal processing circuit 50, respectively.

[0075] Incidentally, in the first embodiment, Figure 4 The support portion 501 of the sensor body 590 shown in the figure is attached and fixed to... Figure 2 The diagram shows a reduction gear 143 with a flexible gear 153. The flexible gear 153 is elliptically deformed by a waveform generator 151, and thus its deformation force is also transmitted to the support portion 501. Therefore, the support portion 501 is deformed by the deformation force.

[0076] Figure 7A and Figure 7B This is an illustrative diagram of the torque sensor 500 as seen in the direction in which the rotation axis C0 extends. Figure 7A The diagram shows... Figure 2 The deformation force of the flexible gear 153 of the reduction gear 143 shown in the figure is not transmitted to the support 501 of the torque sensor 500. Figure 7B The diagram shows Figure 2The deformation force of the flexible gear 153 of the reduction gear 143 shown in the figure is transmitted to the support 501 of the torque sensor 500. Figure 7A and Figure 7B The four encoders 510 are illustrated as encoders 5101, 5102, 5103 and 5104. Encoders 5101, 5102, 5103 and 5104 are arranged at equal intervals at positions 90 degrees symmetrical with respect to the rotation axis C0.

[0077] If the deformation force of the flexible gear 153 does not act on the support 501 of the torque sensor 500, then as Figure 7A As shown in the diagram, the support 501 maintains an annular shape. Encoders 5101, 5102, 5103, and 5104 can accurately detect displacement in the X direction.

[0078] When the torque sensor 500 is applied to the joints of the robot 200, the deformation force of the flexible gear 153 acts on the support 501 of the torque sensor 500. The result is that... Figure 7B As illustrated in the diagram, the support portion 501 is also elliptically deformed, similar to the flexible gear 153. When the waveform generator 151 rotates in the direction of the arrow to drive the joint of the robotic arm 201, the elliptical shape of the flexible gear 153—that is, the elliptical shape of the support portion 501—also rotates in the direction of the arrow. Furthermore, the elliptical shape of the support portion 501 rotates at a frequency twice that of the waveform generator 151. The scale 2 of each of the encoders 5101, 5102, 5103, and 5104 is fixed to the support portion 501. That is, when the joint of the robotic arm 201 rotates, in each of the encoders 5101 to 5104, the scale 2 periodically moves relative to the sensor head 7 in the X and Y directions at a frequency twice that of the waveform generator 151.

[0079] For example, such as Figure 7B As illustrated in the diagram, it is assumed that the elliptical shape of the support 501 rotates clockwise about the rotation axis C0. In encoders 5101 and 5103, similar to the case where torque is applied in the clockwise direction, the scale 2 is displaced relative to the sensor head 7 in the +X direction. In contrast, in encoders 5102 and 5104, similar to the case where torque is applied in the counterclockwise direction, the scale 2 is displaced relative to the sensor head 7 in the -X direction.

[0080] As described above, in the displacement of scale 2 of each of encoders 5101 to 5104, the error originating from the elliptic deformation of the support 501 is superimposed on the torque actually applied to the joint of the robotic arm 201. Since the torque sensor 500 includes four encoders 5101 to 5104, the error can be reduced to a certain extent by averaging the values ​​detected by these encoders. However, since the amount of displacement originating from the elliptic deformation varies in encoders 5101 to 5104, the error cannot be eliminated simply by averaging.

[0081] Therefore, in the first embodiment, the displacement in the Y direction is also measured in encoders 5101 to 5104, and the measured displacement in the X direction is corrected based on the measured displacement in the Y direction to calculate an accurate torque value.

[0082] Figure 8 This is an illustrative diagram based on scale 2 of the first embodiment. Figure 8 The illustration shows an enlarged view of the entire scale 2 and a portion thereof. Scale 2 comprises a substrate such as glass. The patterned portion 80 is formed by patterning a chromium film on the substrate. Note that the substrate of scale 2 can be a resin such as polycarbonate or a metal such as stainless steel. Furthermore, it is sufficient that the patterned portion 80 serves as a reflective film, and the patterned portion 80 can be formed from, for example, aluminum.

[0083] The pattern of the scale track 81 of the pattern portion 80 is read by the light receiving element array 91. The pattern of the scale track 82 of the pattern portion 80 is read by the light receiving element array 92. The scale track 81 includes pattern rows 801 as at least one first pattern row. The scale track 82 includes multiple pattern rows 802 as at least one second pattern row.

[0084] Pattern row 801 includes a plurality of pattern elements 810 serving as a plurality of first pattern elements arranged periodically in the X direction. The plurality of pattern elements 810 are arranged at intervals in the X direction with a predetermined spacing P1 serving as a modulation period. Each of the plurality of pattern elements 810 has a shape symmetrical with respect to an axis L1 serving as a first axis extending in the Y direction.

[0085] Each pattern row 802 includes a plurality of pattern elements 820 serving as a plurality of second pattern elements arranged periodically in the X direction. The plurality of pattern elements 820 are spaced apart in the X direction at a predetermined spacing P2, which serves as a modulation period. Each of the plurality of pattern elements 820 has an asymmetrical shape relative to an axis L2, which serves as a second axis extending in the Y direction. In this embodiment, the spacing P1 of the plurality of pattern elements 810 is equal to the spacing P2 of the plurality of pattern elements 820. That is, the interval between two adjacent axes L1 is equal to the interval between two adjacent axes L2.

[0086] Here, pattern element 820 is asymmetrical at each position in the X direction with respect to each virtual axis extending in the Y direction. That is, there is no axis in which pattern element 820 is symmetrical with respect to its line. In contrast, pattern element 810 has one axis in which it is symmetrical with respect to its line among the virtual axes extending in the Y direction, and that axis is axis L1.

[0087] In the first embodiment, multiple pattern rows 802 are arranged continuously in the Y direction. The length of each pattern row 802 in the Y direction is represented by Y2. Multiple pattern elements 820 in a continuous row in the Y direction constitute a pattern element group 825. In the pattern element group 825, multiple pattern elements 820 of the same shape are arranged in the Y direction with a period of length Y2. In the first embodiment, multiple pattern element groups 825 are arranged at equal intervals with a spacing P2 in the X direction.

[0088] In each pattern row 802, a plurality of pattern elements 820 arranged at intervals in the X direction each include a rectangular portion 821 serving as a first portion and a rectangular portion 822 positioned in the X direction offset from portion 821 serving as a second portion. The displacement of portion 822 relative to portion 821 in the X direction is preferably 1 / 6 of the spacing P2 between two adjacent pattern elements 820. Furthermore, the length of portion 821 in the Y direction is preferably equal to the length of portion 822 in the Y direction; that is, the length of each of portions 821 and 822 in the Y direction is preferably Y² / 2.

[0089] Although the spacings P1 and P2 can be different, they are preferably equal. The spacing P1 used for measuring torque is preferably as small as possible. By setting the spacing P1 small, high resolution of the torque sensor 500 can be achieved. In the following description, the case where the spacings P1 and P2 are 100 μm and the length Y2 is 50 μm will be described.

[0090] Figure 9 This is a plan view of the optical receiver array 91 according to the first embodiment. Note that the configuration of the optical receiver array 92 is substantially the same as that of the optical receiver array 91, therefore its illustration and description will be omitted. The optical receiver array 91 includes a plurality (e.g., 32) of optical receiver elements 90 arranged at a spacing of 50 μm in the X direction. Each optical receiver element 90 has a width X_pd of 50 μm in the X direction and a width Y_pd of 800 μm in the Y direction. The total width X_total of the optical receiver array 91 is 1600 μm.

[0091] The pattern on scale 2 is projected onto the light-receiving element array 91 as an image of doubled size. Therefore, the detection range on scale 2 is 800 μm in the X direction and 400 μm in the Y direction. On the light-receiving element array 92, due to the relationship between width Y_pd and length Y2, the detection range on scale 2 is 8 pattern rows 802. Note that when the value of Y_pd / Y2 is not an integer, the phase in the X direction varies depending on the detection position in the Y direction. Therefore, the value of Y_pd / Y2 is preferably an integer so that the position in the Y direction does not affect the detection phase in the X direction. The respective detection signals of the light-receiving element arrays 91 and 92 are output to... Figure 6A The circuit sections 511 and 512 are shown in the diagram.

[0092] Figure 10 This is a circuit diagram of the circuit section 511 of the signal processing circuit 50 in the first embodiment. Note that since the circuit section 512 has a substantially the same configuration as the circuit section 511, the illustration and description of the circuit section 512 will be omitted.

[0093] In the stage following the optical receiver array 91, four IV-conversion amplifiers 34, 35, 36, and 37 are provided as first-stage amplifiers. The IV-conversion amplifiers 34, 35, 36, and 37 generate four-phase sine wave outputs S1(A+), S1(B+), S1(A-), and S1(B-) from a detection signal that is a current signal read from each optical receiver element 90 of the optical receiver array 91. Regarding the relative phase of the four-phase sine waves, when S1(A+) is set to standard relative to the detection spacing, the phase of S1(B+) is approximately +90°, S1(A-) is approximately +180°, and S1(B-) is approximately +270°.

[0094] In the stages following IV conversion amplifiers 34, 35, 36, and 37, an A-phase differential amplifier 39 and a B-phase differential amplifier 40 are provided. The A-phase differential amplifier 39 and the B-phase differential amplifier 40 perform the calculations of equations (1) and (2) using four-phase sinusoidal outputs S1(A+), S1(B+), S1(A-), and S1(B-). The result is that the A-phase differential amplifier 39 and the B-phase differential amplifier 40 generate two-phase sinusoidal signals S1(A) and S1(B) with the DC component removed.

[0095] S1(A)=S1(A+)-S1(A-)...(1)

[0096] S1(B)=S1(B+)-S1(B-)...(2)

[0097] In the stage following phase A differential amplifier 39 and phase B differential amplifier 40, the following is provided Figure 5AThe computer 650 shown in the figure has two phase sine wave signals S1(A) and S1(B) output to the computer 650.

[0098] As mentioned above, Figure 6A The circuit unit 511 shown in the figure generates two-phase sinusoidal signals S1(A) and S1(B) obtained by removing the DC component from the detection signal S1 obtained from the optical receiving element array 91. Similar to the circuit unit 511, the circuit unit 512 generates two-phase sinusoidal signals S2(A) and S2(B) obtained by removing the DC component from the detection signal S2 obtained from the optical receiving element array 92.

[0099] here, Figure 8 The pattern in pattern row 801 is the pattern that is detected by sensor head 7 as displacement in the X direction when sensor head 7 and scale 2 are displaced relative to each other in the X direction. Note that the pattern in pattern row 801 is the pattern that is not detected by sensor head 7 as displacement in the X direction when sensor head 7 and scale 2 are displaced relative to each other in the Y direction.

[0100] Furthermore, the pattern in pattern row 802 is a pattern that is detected by sensor head 7 as displacement in the X direction when sensor head 7 and scale 2 are displaced relative to each other in the X direction. Additionally, the pattern in pattern row 802 is a pattern that is detected by sensor head 7 as displacement in the X direction when sensor head 7 and scale 2 are displaced relative to each other in the Y direction.

[0101] In the first embodiment, the computer 650 obtains a torque value τ that removes the error caused by the elliptical deformation of the support portion 501 by using sinusoidal wave signals S1(A), S1(B), S2(A), and S2(B) which are based on the phase information of the detection signals S1 and S2 from the sensor head 7. Among the phase information, the sinusoidal wave signals S1(A) and S1(B) are used as first information, and the sinusoidal wave signals S2(A) and S2(B) are used as second information.

[0102] The control method for robot 200 and the torque detection method for torque sensor 500 according to the first embodiment will be described in detail. Figure 11A This is a flowchart illustrating an example of a control method for a robot 200 according to a first embodiment.

[0103] First, refer to Figure 11AThe flowchart shown in the figure describes a control method for robot 200. In step S101, robot control device 300 controls robot 200 so that robot 200 operates according to trajectory data corresponding to a robot program including teach data. At this time, robot control device 300 supplies drive current to motor 141 of each of joints J1 to J3 to drive joints J1 to J3. The torque as a load can be applied externally to joints J1 to J3 or not.

[0104] In step S102, the robot control device 300 obtains the torque value τ from the torque sensor 500 during the control of the robot 200.

[0105] Next, in step S103, the robot control device 300 determines whether the torque value τ is greater than the threshold TH. That is, whether the robot 200 has come into contact with an operator or object around the robot 200. If the robot 200 has come into contact with something, the torque value τ exceeds the threshold TH.

[0106] If the torque value τ is equal to or less than the threshold TH, that is, if the result of step S103 is negative, the robot control device 300 returns to the processing of step S101 and controls the robot 200.

[0107] If the torque value τ is greater than the threshold TH, that is, if the result of step S103 is yes, in step S104, the robot control device 300 stops the operation of the robot 200. Additionally, in step S105, the robot control device 300 performs alarm processing. In this embodiment, since the robot system 100 includes three torque sensors 500, if any of the three torque values ​​exceeds the threshold TH, the robot control device 300 proceeds to the processing steps S104 and S105.

[0108] Examples of methods for stopping the operation of robot 200 include rapid stopping, slow stopping, moving in the opposite direction, and switching to impedance control. Additionally, as alarm handling, robot control device 300 may cause robot 200 to output an error signal or alarm, display the torque value τ on a terminal such as teach pendant 400, or obtain and store a log in the storage unit of robot control device 300.

[0109] Note that the order of steps S104 and S105 can be reversed, or steps S104 and S105 can be performed simultaneously. Alternatively, one of steps S104 or S105 can be omitted.

[0110] The torque value τ obtained by the robot control device 300 in step S102 is detected as follows.Figure 11B This is a flowchart illustrating an example of the torque detection method according to the first embodiment. Here, Figure 11B Steps S201 to S204 shown in the diagram are Figure 5B The arithmetic processing of each displacement calculation unit 680 shown in the figure, and step S205 is Figure 5B The arithmetic processing of the torque calculation unit 681 shown in the diagram. Because... Figure 5B Each displacement calculation unit 680 shown in the figure performs substantially the same calculation, therefore, in the description of the process in steps S201 to S204 below, one of the multiple displacement calculation units 680 will be described.

[0111] In step S201, the displacement calculation unit 680 detects the phase Φ11 of the displacement in the X direction from the pattern row 801. That is, the displacement calculation unit 680 obtains the first displacement of the scale 2 relative to the sensor head 7 in the X direction as the phase Φ11 by using the sinusoidal wave signals S1(A) and S1(B) obtained from the circuit unit 511. The phase Φ11 is obtained according to the following formula (3).

[0112] Φ11=ATAN2[S1(A),S1(B)]...(3)

[0113] ATAN2[Y,X] is a function that determines the quadrant and performs an arctangent calculation to convert the phase to 0 to 2π. The positions of phase Φ11 and scale 2 have Figure 12 The relationship is illustrated in the curve graph.

[0114] It should be noted that before performing the calculation of Equation (3), the gain ratio and offset error originating from the offset, gain variation, etc. of each amplifier and included in the sinusoidal signals S1(A) and S1(B) can be corrected using pre-obtained correction values. For example, for each of the sinusoidal signals S1(A) and S1(B), the gain ratio—that is, the amplitude ratio—can be calculated by (maximum value - minimum value) / 2 to calculate the correction value used to make the signal amplitudes equal. Similarly, the amount of offset error can be calculated by (maximum value + minimum value) / 2 to calculate the correction value used to correct the offset error. These correction values ​​can be stored in the storage device 670.

[0115] Incidentally, phase Φ11 includes the error Φ10' in the X direction of the relative displacement of scale 2 relative to sensor head 7 in the X direction caused by the elliptical deformation of support 501. Note that even if the relative displacement of scale 2 relative to sensor head 7 in the Y direction is caused by the elliptical deformation of support 501, phase Φ11 is unaffected.

[0116] That is, when the phase obtained under the assumption that the support 501 is not elliptical and does not include the error Φ10' from the elliptical deformation is represented by Φ10, the phase Φ11 satisfies the following equation (4).

[0117] Φ11=Φ10+Φ10'...(4)

[0118] For example, when no torque is applied to the torque sensor 500, the phase Φ10 is zero, but the actually detected phase Φ11 includes an error Φ10' caused by the elliptical deformation of the support 501.

[0119] Next, in step S202, the displacement calculation unit 680 detects the phase Φ12, which is the amount of displacement in the X direction, from the pattern row 802. That is, the displacement calculation unit 680 obtains the amount of displacement of the scale 2 relative to the sensor head 7 in the X direction as the phase Φ12 by using the sinusoidal wave signals S2(A) and S2(B) obtained from the circuit unit 512. The phase Φ12 is obtained according to the following formula (5).

[0120] Φ12=ATAN2[S2(A),S2(B)]...(5)

[0121] Phase Φ12 includes the error Φ10' in the X direction of the relative displacement of scale 2 with respect to sensor head 7 in the X direction caused by the elliptical deformation of support 501.

[0122] In addition, the phase Φ12 includes the error in the Y direction of the relative displacement of the scale 2 with respect to the sensor head 7 in the Y direction caused by the elliptical deformation of the support 501, which is taken as the error Φ10 in the X direction. That is, the phase Φ12 satisfies the following equation (6).

[0123] Φ12=Φ10+Φ10'+Φ10”...(6)

[0124] The following describes how the error Φ10” is superimposed on the phase Φ12. For the sake of simplicity, the description will assume that the scale 2 is displaced relative to the sensor head 7 only in the Y direction and not in the X direction. Figure 13A and Figure 13B This is an illustrative diagram used to explain how the error Φ10” is superimposed on the phase Φ12 in the first embodiment.

[0125] The detection range of the scale track 82 will be represented by R2. The light receiving element array 92 only receives reflected light from the detection range R2, and does not receive reflected light from areas outside the detection range R2. In the scale track 82, light emitted from the light source 1 is incident diagonally onto it, and in the light receiving element array 92, the reflected light from the scale track 82 is received diagonally. Therefore, the amount of reflected light is not uniformly distributed in the detection range R2. Among the reflected light from the detection range R2, the large amount of reflected light significantly affects the light receiving sensitivity of the light receiving element array 92. Therefore, in the detection signal S2 output from the light receiving element array 92, the reflected light from the portion with the large amount of light in the detection range R2 dominates. Then, when the detection range R2 moves from the Y direction... Figure 13A The state shown in the middle diagram moves to Figure 13B In the state shown in the diagram, even if the detection range R2 does not move in the X direction, the detection signal S2 changes according to the shape of the pattern element 820, which is asymmetrical with respect to axis L2.

[0126] In the first embodiment, as a result of multiple pattern elements 820 of the same shape being continuous in the Y direction, each pattern element group 825 has a periodic shape. Therefore, when the detection range R2 moves in the Y direction by an amount equal to or greater than the length Y2, the phase Φ12 also changes periodically. Figure 13C This is a schematic diagram of a Lissajous waveform according to the first embodiment. The horizontal axis represents the sine wave signal S2(A) in the detection signal S2, and the vertical signal represents the sine wave signal S2(B) in the detection signal S2. When the detection range R2 moves in the Y direction, the point P12 (S2(A), S2(B)) reciprocates within a predetermined range on the circle of the Lissajous waveform.

[0127] In the first embodiment, as Figure 8 As shown in the diagram, the displacement of portion 822 relative to portion 821 in the X direction is 1 / 6 of the spacing P2. In this pattern, in... Figure 13C In the Lissajous waveform represented by dashed lines, high-frequency components can be reduced using the principle of optical interference. As described above, since the displacement of portion 822 relative to portion 821 in the X direction of pattern element 820 is 1 / 6 of the spacing P2, the removal of the third high-frequency component and therefore the high-precision phase Φ12 can be detected.

[0128] In step S203, the displacement calculation unit 680 obtains the displacement amount ΔY, which is used as the second displacement amount of the scale 2 relative to the sensor head 7 in the Y direction. Specifically, firstly, the displacement calculation unit 680 obtains the difference ΔΦ by subtracting the phase Φ11 from the phase Φ12. The difference ΔΦ is represented by the following formula (7).

[0129] ΔΦ=Φ12-Φ11(=Φ10”)...(7)

[0130] That is, the difference ΔΦ corresponds to the error Φ10". This means that the displacement calculation unit 680 calculates the error Φ10 by obtaining the difference ΔΦ. The difference ΔΦ - that is, the error Φ10" is a value that changes periodically based on the displacement ΔY of the scale 2 relative to the sensor head 7 in the Y direction. Figure 14 It is a graph illustrating the relationship between the difference ΔΦ and the displacement ΔY. Figure 14 The relationships illustrated in the diagram are pre-stored in storage device 670. For example, the relationship between the difference ΔΦ and the displacement ΔY is stored in storage device 670 as tabular data or a calculation formula. Figure 14 The relationships illustrated in the diagram can be generated using design values ​​of the light distribution characteristics of the light source and design values ​​of the pattern row 802 on the scale, or they can be obtained through experiments. The displacement calculation unit 680 is based on... Figure 14 The relationship shown in the diagram converts the difference ΔΦ into the displacement ΔY.

[0131] Pattern element 820 is a pattern in which parts 821 and 822 are asymmetrically displaced by 1 / 6 of the spacing P2. Therefore, the difference between the maximum and minimum values ​​of the difference ΔΦ changes periodically within the range of (1 / 6) × 2π [rad] according to the relative displacement of scale 2 relative to sensor head 7 in the Y direction. The displacement calculation unit 680 counts the number of cycles of change of difference ΔΦ that have occurred, and obtains the displacement ΔY from the count value and the value of difference ΔΦ at this time.

[0132] In this way, the displacement calculation unit 680 obtains the phase Φ11 from the sinusoidal signals S1(A) and S1(B), and obtains the displacement ΔY from the phase Φ11 and the sinusoidal signals S2(A) and S2(B).

[0133] Next, the displacement calculation unit 680 obtains the elliptical shape, i.e., the ellipticity of the support 501, from the displacement amount ΔY obtained by switching the phase Φ11 and the displacement amount ΔX in the X direction. Here, depending on the rotation direction of the waveform generator 151, which is the input shaft of the reduction gear 143, the sign of the error amount in the X direction originating from the deformation of the support 501 into an elliptical shape is reversed. Therefore, the displacement calculation unit 680 obtains information about the rotation direction of the input shaft of the reduction gear 143 in advance from the robot control device 300. Specifically, when the input shaft of the reduction gear 143 is as follows... Figure 7BWhen the support portion 501 rotates clockwise as illustrated in the diagram, it is assumed that the support portion 501 has an elliptical shape that is a circle deformed at a predetermined angle in the clockwise direction, and the ellipticity is a positive value. In contrast, when the input shaft of the reduction gear 143 rotates counterclockwise, it is assumed that the support portion 501 has an elliptical shape that is a circle deformed at a predetermined angle in the counterclockwise direction, and the ellipticity is a negative value.

[0134] The displacement calculation unit 680 obtains the ellipticity of the support 501 based on information considering the rotation direction of the input shaft of the reduction gear 143, and obtains the amount and direction of the error component in the X direction caused by the deformation of the support 501 in the Y direction.

[0135] The displacement calculation unit 680 obtains the ellipticity and distance of the support 501 for use as... Figure 7A The difference between the distances of the rotation axis C0 of the rotation center of the support 501, which does not receive deformation force, as shown in the diagram. This results in an error Φ10', which is the detection error in the X direction influenced by the displacement of the support 501 based on the elliptical motion of the reduction gear 143.

[0136] Next, in step S204, the displacement calculation unit 680 obtains the phase Φ10 as displacement information in the X direction corresponding to the torque value τ from the following formula (8). The phase Φ10 as displacement information corresponds to the relative displacement of the support 501 relative to the support 502, which originates from the elastic deformation of the elastic part 503, which eliminates the error originating from the elastic deformation of the support 501.

[0137] Φ10=Φ11-Φ10'...(8)

[0138] Then, in step S205, the torque calculation unit 681 calculates the torque value τ based on the four phases Φ10 obtained for the four encoders 510 respectively. For example, the torque calculation unit 681 averages the four phases Φ10 and calculates the torque value τ by, for example, multiplying the average value by a predetermined coefficient such as a sensitivity coefficient proportional to the elastic modulus of the elastic unit 503. Note that the method for calculating the torque value τ is not limited to this, and the torque value τ can also be obtained by converting each phase Φ10 into a temporary torque value and averaging the four temporary torque values. The displacement calculation unit 680 outputs the calculated torque value τ to the robot control device 300.

[0139] As described above, according to the first embodiment, even when the deformation force originating from the elliptical deformation of the reduction gear 431 is applied to the torque sensor 500 included in the joint of the robot 200, the torque value τ can be obtained with high accuracy. That is, the detection accuracy of the torque value τ is improved. Since the detection accuracy of the torque value τ is improved, the operating accuracy of the robot 200 can be improved. For example, by using the torque value τ to determine whether to stop the operation of the robot 200, the operation of the robot 200 can be stopped quickly when the robot 200 comes into contact with an operator or object. In addition, when force control of the robot 200 is performed by using the torque value τ, the operation of the robot 200 can be controlled with high accuracy.

[0140] Furthermore, the order of the processing in step S201 and the processing in step S202 is not limited to the above order, and the processing in step S201 can be performed after the processing in step S202, or if possible, they can be performed simultaneously.

[0141] Variations

[0142] Variations will be described. Figure 15 This is a plan view of the scale track 82 according to the modified scale 2. The modified scale track 82 includes multiple pattern rows 802. The multiple pattern rows 802 are arranged continuously in the Y direction. The length of each pattern row 802 in the Y direction is represented by Y2. In the scale track 82, focus is placed on multiple pattern elements 820 in a continuous row in the Y direction. Multiple pattern elements 820 of the same shape are arranged in the Y direction with a period of length Y2. The multiple pattern elements 820 arranged continuously in a row in the Y direction constitute a pattern element group 825. In the modified example, the multiple pattern element groups 825 are arranged at equal intervals of spacing P2 in the X direction. Each pattern element 820 in each pattern row 802 is preferably asymmetrical with respect to axis L2 and may have, for example, Figure 15 The waveform shown in the diagram.

[0143] Second Embodiment

[0144] The second embodiment will be described. Figure 16A This is a schematic diagram of an encoder device 550A used as an example of a displacement detection device according to the second embodiment. Note that in the second embodiment, elements substantially the same as those in the first embodiment will be indicated by the same reference numerals, and their descriptions will be omitted. Similar to the first embodiment, the encoder device 550A includes an encoder 510A, a signal processing circuit 50A, a displacement calculation unit 680, and a storage device 670.

[0145] In the second embodiment, in Figure 1 In the robot system 100 shown in the diagram, the following is used: Figure 16A The encoder 510A shown in the diagram replaces...Figure 4 The encoder 510 is shown in the torque sensor 500 illustrated in the figure. A description will now be given with appropriate reference to the accompanying drawings described in the first embodiment.

[0146] Encoder 510A can be a linear encoder or a rotary encoder, but similar to the first embodiment, it is also a linear encoder in the second embodiment. Furthermore, encoder 510A is an optical encoder of the optical interferometry type and is an incremental encoder. Additionally, although encoder 510 is reflective in the second embodiment, encoder 510A can be transmissive.

[0147] The encoder 510A includes a scale 2A and a sensor head 7A positioned in the Z direction opposite to the scale 2A. The scale 2A includes a patterned portion 80A. Figure 16B This is a plan view of the sensor head 7A according to the second embodiment.

[0148] The sensor head 7A reads the pattern portion 80A of the scale 2A and outputs the detection signal S to the signal processing circuit 50A. The sensor head 7A includes a light source 1 composed of an LED, used as an example of a light-emitting unit, and a light-receiving unit 3. The light-receiving unit 3 has a configuration that is substantially the same as that of the light-receiving unit 31 described in the first embodiment. That is, in the second embodiment, the size of the sensor head 7A is reduced by omitting the light-receiving unit 32.

[0149] A light receiving unit 3 is positioned in the Y direction at a distance from the light source 1. The light receiving unit 3 includes a light receiving element array 9. The light source 1 and the light receiving unit 3 are mounted on a printed wiring board 4 and sealed by a transparent resin 5 that allows light to pass through. A transparent glass 6 that allows light to pass through is disposed on the surface of the resin 5. According to this configuration, the light source 1 and the light receiving unit 3 are protected by the resin 5 and the glass 6.

[0150] The signal processing circuit 50A is composed of semiconductor elements, such as IC chips. The signal processing circuit 50A is mounted on, for example, the surface of a printed circuit board 4. It should be noted that the location of the signal processing circuit 50A is not limited to this, and the signal processing circuit 50A can be deployed at a location different from its position on the printed circuit board 4. Figure 16A For ease of description, the signal processing circuit 50A is positioned differently from its location on the printed circuit board 4. The signal processing circuit 50A includes a switching circuit 41 and a circuit section 51. The switching circuit 41 outputs detection signals S1 and S2 from the photodetector array 9 and switches between them. The circuit configuration of the circuit section 51 is substantially the same as that of the circuit section 511 described in the first embodiment.

[0151] Figure 17 This is an illustrative diagram based on scale 2A of the second embodiment. Figure 17The illustration shows an enlarged view of the entire scale 2A and a portion thereof. Scale 2A comprises a substrate such as glass. The patterned portion 80A is formed by patterning a chromium film on the substrate material. Note that the substrate of scale 2A can be a resin such as polycarbonate or a metal such as stainless steel. Furthermore, it is sufficient that the patterned portion 80A serves as a reflective film, and the patterned portion 80A can be formed from, for example, aluminum.

[0152] The pattern of pattern portion 80A is read by the light receiving element array 9. Pattern portion 80A includes a plurality of pattern rows 801A as at least one first pattern row. In addition, pattern portion 80A includes a plurality of pattern rows 802A as at least one second pattern row.

[0153] Each pattern row 801A includes a plurality of pattern elements 810A serving as a plurality of first pattern elements arranged periodically in the X direction. The plurality of pattern elements 810A are arranged at intervals in the X direction with a predetermined spacing P4 serving as a modulation period. Each of the plurality of pattern elements 810A has a shape symmetrical with respect to an axis L4 serving as a first axis extending in the Y direction.

[0154] Each pattern row 802A includes a plurality of pattern elements 820A serving as a plurality of second pattern elements arranged periodically in the X direction. The plurality of pattern elements 820A are arranged at intervals in the X direction with a predetermined spacing P5 serving as a modulation period. Each of the plurality of pattern elements 820A has an asymmetrical shape relative to an axis L5 serving as a second axis extending in the Y direction. In this embodiment, the spacing P4 of the plurality of pattern elements 810A is different from the spacing P5 of the plurality of pattern elements 820A. For example, the spacing P4 is 100 μm, and the spacing P5 is 200 μm. Note that pattern rows different from pattern rows 801A and 802A may be included in the pattern portion 80A.

[0155] In the second embodiment, multiple pattern rows 801A and multiple pattern rows 802A are arranged alternately in the Y direction. The length of a pair of pattern rows 801A and pattern rows 802A in the Y direction is represented by Y4. The pattern portion 80A is configured such that the same shape is repeated in the Y direction with a period of length Y4.

[0156] Figure 18 and Figure 19Each is a plan view of the light receiving element array 9 according to the second embodiment. The light receiving element array 9 includes a plurality of (e.g., 32) light receiving elements 90. Each light receiving element 90 has a width X_pd of 50 μm in the X direction and a width Y_pd of 800 μm in the Y direction. The total width X_total of the light receiving element array 9 is 1600 μm. Note that when the value of Y_pd / Y4 is not an integer, the phase in the X direction varies depending on the detection position in the Y direction. Therefore, the value of Y_pd / Y4 is preferably an integer, such that the position in the Y direction does not affect the detection phase in the X direction. In the pattern portion 80A, it is preferable that the total area of ​​the detection range on which light is reflected and incident on the light receiving element array 9 is constant, regardless of the position in the Y direction. According to this configuration, the output light amount of the light source 1 can be controlled based on the sum of S(A+), S(B+), S(A-), and S(B-) obtained for each of the spacings P4 and P5.

[0157] In the second embodiment, the detection resolution can be switched using the switching circuit 41. The switching circuit 41 allows the optical receiver array 9 to output a detection signal S1 based on pattern row 801A and a detection signal S2 based on pattern row 802A, respectively. That is, in the second embodiment, the circuit unit 51 can selectively obtain either the detection signal S1 or the detection signal S2 from the optical receiver array 9 using the switching circuit 41. The circuit unit 51 generates two-phase sinusoidal signals S1(A) and S1(B) obtained by removing the DC component from the detection signal S1 obtained from the optical receiver array 9. Similarly, the circuit unit 51 generates two-phase sinusoidal signals S2(A) and S2(B) obtained by removing the DC component from the detection signal S2 obtained from the optical receiver array 9. It should be noted that when the pattern portion 80A includes pattern rows different from pattern rows 801A and 802A, the switching circuit 41 can be configured to be switchable between three or more detection resolutions.

[0158] Here, the pattern in pattern row 801A is the pattern that is detected by sensor head 7A as displacement in the X direction when sensor head 7 and scale 2A are displaced relative to each other in the X direction. Note that the pattern in pattern row 801A is the pattern that is not detected by sensor head 7A as displacement in the X direction when sensor head 7A and scale 2A are displaced relative to each other in the Y direction.

[0159] In addition, the pattern of pattern row 802A is the pattern that is detected by sensor head 7A as displacement in the X direction when sensor head 7A and scale 2A are displaced relative to each other in the Y direction.

[0160] In the second embodiment, the displacement calculation unit 680 obtains the phase Φ10 for the torque calculation unit 681 to obtain the torque value τ by using sinusoidal wave signals S1(A), S1(B), S2(A), and S2(B) which are based on the phase information of the detection signals S1 and S2 from the sensor head 7A. Among the phase information, the sinusoidal wave signals S1(A) and S1(B) are used as first information, and the sinusoidal wave signals S2(A) and S2(B) are used as second information.

[0161] In the following text, due to the second embodiment Figure 1 The control method for robot 200 illustrated in the middle is the same as that described in the first embodiment. Figure 11A The flowcharts of the control methods shown in the diagrams are essentially the same, therefore their descriptions will be omitted. The torque detection method of the torque sensor in the second embodiment is also similar to the torque detection method in the first embodiment, but differs from the first embodiment in this respect due to the switching operation performed by the switching circuit 41. That is, the detection method in the second embodiment is similar to... Figure 11B The detection methods illustrated in the diagram are basically the same, but the processing of step S201 and step S202 is performed by switching via switch circuit 41. Specifically, in step S201, switch circuit 41 is switched to... Figure 18 The state is shown in the diagram, and in step S202, the switching circuit 41 is switched to... Figure 19 The state shown in the diagram.

[0162] In step S201, the switching circuit 41 is switched to Figure 18 As shown in the diagram, every three optical receiving elements in the plurality of optical receiving elements 90 are electrically connected to each other, and a current signal is input to... Figure 10 One of the IV conversion amplifiers 34 to 37 shown in the diagram. As a result, a pattern with spacing P4 was detected.

[0163] In step S202, the switching circuit 41 is switched to Figure 19 As shown in the diagram, each pair of adjacent optical receiving elements in the plurality of optical receiving elements 90 is electrically connected to each other, and a current signal is input to... Figure 10 One of the IV conversion amplifiers 34 to 37 shown in the diagram. The result is that a pattern with a spacing of P5 is detected.

[0164] As described above, by switching the detection resolution by the switching circuit 41, the detection signal S1 based on the periodic pattern of the spacing P4 and the detection signal S2 based on the periodic pattern of the spacing P5 can be selectively output to the circuit section 51 by using a light receiving element array 9.

[0165] As described above, according to the second embodiment, similar to the first embodiment, even when the deformation force originating from the elliptical deformation of the reduction gear 431 is applied to the torque sensor, the torque value τ can be obtained with high accuracy. That is, the detection accuracy of the torque value τ is improved. Since the detection accuracy of the torque value τ is improved, the operating accuracy of the robot 200 can be improved. In addition, the size of the encoder 510A can be reduced, and therefore the size of the torque sensor and the robot can also be reduced.

[0166] It should be noted that the order of processing steps S201 and S202 is not limited to the order described above, and the processing of step S201 can be performed after the processing of step S202. Furthermore, each of the pattern elements 820A is preferably asymmetrical with respect to axis L5, and may, for example, have the following characteristics: Figure 15 The wavy shape of pattern element 820 shown in the diagram.

[0167] Third Embodiment

[0168] The third embodiment will be described. Figure 20A This is a schematic diagram of an encoder device 550B used as an example of a displacement detection device according to a third embodiment. Note that in the third embodiment, elements substantially the same as in the first embodiment will be indicated by the same reference numerals, and their description will be omitted. Similar to the first embodiment, the encoder device 550B includes an encoder 510B, a signal processing circuit 50B, a displacement calculation unit 680, and a storage device 670.

[0169] In the third embodiment, Figure 1 In the robot system 100 shown in the diagram, the following is used: Figure 20A The encoder 510B shown in the diagram replaces... Figure 4 The encoder 510 is shown in the torque sensor 500 illustrated in the figure. A further description will now be given with reference to the accompanying drawings described in the first embodiment.

[0170] Encoder 510B can be a linear encoder or a rotary encoder, but similar to the first embodiment, it is also a linear encoder in the third embodiment. Furthermore, encoder 510B is an optical encoder of the interferometric type and is an incremental encoder. Additionally, although encoder 510B is reflective in the third embodiment, it can also be transmissive.

[0171] The encoder 510B includes a scale 2B and a sensor head 7B positioned in the Z direction opposite to the scale 2B. The scale 2B includes a patterned portion 80B. Figure 20B This is a plan view of the sensor head 7B according to the third embodiment.

[0172] The sensor head 7B reads the pattern portion 80B of the scale 2B and outputs the detection signal S2 to the signal processing circuit 50B. The sensor head 7B includes a light source 1 composed of an LED, used as an example of a light-emitting unit, and a light-receiving unit 3. The light-receiving unit 3 has a configuration substantially the same as the light-receiving unit 32 described in the first embodiment. That is, in the third embodiment, the size of the sensor head 7B is reduced by omitting the light-receiving unit 31.

[0173] A light receiving unit 3 is positioned in the Y direction at a distance from the light source 1. The light receiving unit 3 includes a light receiving element array 9. The light source 1 and the light receiving unit 3 are mounted on a printed wiring board 4 and sealed by a transparent resin 5 that allows light to pass through. A transparent glass 6 that allows light to pass through is disposed on the surface of the resin 5. According to this configuration, the light source 1 and the light receiving unit 3 are protected by the resin 5 and the glass 6.

[0174] The signal processing circuit 50B is composed of semiconductor elements, such as IC chips. The signal processing circuit 50B is mounted on, for example, the surface of a printed circuit board 4. It should be noted that the location of the signal processing circuit 50B is not limited to this, and the signal processing circuit 50B can be deployed at a location different from its position on the printed circuit board 4. Figure 20A For ease of description, the signal processing circuit 50B is positioned at a location different from that on the printed circuit board 4. The signal processing circuit 50B includes a circuit section 51 that obtains the detection signal S2 from the photodetector array 9 and processes the obtained signal. The circuit configuration of the circuit section 51 is substantially the same as that of the circuit section 512 described in the first embodiment, that is, substantially the same as that of the circuit section 511.

[0175] Figure 21 This is an illustrative diagram based on scale 2B of the third embodiment. Figure 21 The illustration shows an enlarged view of the entire scale 2B and a portion thereof. The scale 2B comprises a substrate such as glass. The patterned portion 80B is formed by patterning a chromium film on the substrate material. Note that the substrate of the scale 2B can be a resin such as polycarbonate or a metal such as stainless steel. Furthermore, it is sufficient that the patterned portion 80B serves as a reflective film, and the patterned portion 80B can be formed from, for example, aluminum.

[0176] The pattern of pattern portion 80B is configured in a manner similar to the scale track 82 described in the first embodiment, and the scale track 81 described in the first embodiment is omitted. The pattern of pattern portion 80B is read by the light receiving element array 9. Pattern portion 80B includes a plurality of pattern rows 802 as at least one pattern row. That is, pattern portion 80B includes a plurality of pattern rows 802 configured in a manner similar to the first embodiment, and does not include the pattern row 801 described in the first embodiment.

[0177] Each pattern row 802 includes a plurality of pattern elements 820 periodically arranged in the X direction. The plurality of pattern elements 820 are spaced apart in the X direction at a predetermined spacing P2, which serves as a modulation period. Each of the plurality of pattern elements 820 has an asymmetrical shape relative to an axis L2 extending in the Y direction.

[0178] Multiple pattern rows 802 are arranged continuously in the Y direction. The length of each pattern row 802 in the Y direction is represented by Y2. Multiple pattern elements 820 in a continuous row in the Y direction constitute a pattern element group 825. In the pattern element group 825, multiple pattern elements 820 of the same shape are arranged in the Y direction with a period of length Y2. In the third embodiment, the multiple pattern element groups 825 are arranged at equal intervals with a spacing P2 in the X direction.

[0179] In each pattern row 802, a plurality of pattern elements 820 arranged at intervals in the X direction each include a rectangular portion 821 serving as a first portion and a rectangular portion 822 disposed at a position offset from portion 821 in the X direction serving as a second portion. The displacement of portion 822 relative to portion 821 in the X direction is preferably 1 / 6 of the spacing P2 between two adjacent pattern elements 820 among the plurality of pattern elements 820. Furthermore, the length of portion 821 in the Y direction is preferably equal to the length of portion 822 in the Y direction; that is, the length of each of portions 821 and 822 in the Y direction is preferably Y² / 2. Note that each pattern element 820 is preferably asymmetrical with respect to axis L2 and may, for example, have the following characteristics: Figure 15 The wavy shape of pattern element 820 in the modified example shown in the figure.

[0180] The pattern in pattern row 802 is a pattern that is detected by sensor head 7B as displacement in the X direction when sensor head 7B and scale 2B are displaced relative to each other in the X direction. Additionally, the pattern in pattern row 802 is a pattern that is detected by sensor head 7B as displacement in the X direction when sensor head 7B and scale 2B are displaced relative to each other in the Y direction.

[0181] In the third embodiment, the displacement calculation unit 680 obtains the phase Φ10 for the torque calculation unit 681 to obtain the torque value τ by using sine wave signals S2(A) and S2(B) which are based on the phase information of the detection signal S2 from the sensor head 7B.

[0182] In the following text, due to the third embodiment Figure 1 The control method for robot 200 illustrated in the middle is the same as that described in the first embodiment. Figure 11A The flowcharts of the control methods shown in the diagrams are basically the same, therefore their descriptions will be omitted. In the third embodiment, Figure 11AThe flowchart shown in the middle illustrates the operating mode for enabling robot 200 to actually perform operations for manufacturing products.

[0183] The torque detection method of the torque sensor in the third embodiment differs from that in the first embodiment. Robot 200 is an industrial robot. Robot 200 is used to continuously manufacture the same product and repeat the same operations for this purpose. Therefore, in the third embodiment, a calibration value is pre-measured and stored in the storage device 670. This storage operation is performed in test run mode. Then, during the actual operation of robot 200, i.e., in operation mode, the detection result of the encoder device 550B included in the torque sensor is calibrated using the calibration value. For example, this can be achieved through operator operation. Figure 1 The teach pendant 400 shown in the diagram performs the selection between an operating mode used as the first mode and a test run mode used as the second mode. The robot control device 300 executes the mode selected by the operator.

[0184] Figure 22A This is a flowchart illustrating the preprocessing of the robot system according to the third embodiment. That is, Figure 22A The flowchart shown in the figure illustrates the test operation mode. In step S301B, the robot control device 300 operates the robot 200 without load based on the trajectory data used in the operation mode. At this time, the corresponding joints J1 to J3... Figure 5A The CPU 651 shown in the diagram obtains the correction value associated with the trajectory data. In step S302B, the CPU 651 stores the correction value associated with the trajectory data. Figure 20A The data is stored in the storage device 670 shown in the figure as table data 671B. In this way, a profile of the error in the detection results caused by the elliptical deformation of the reduction gear 143 is measured in advance as a correction value.

[0185] Here, the correction values ​​will be described in detail. Operating the robot 200 without load refers to rotating the waveform generator 151 of the reduction gears 143 of each of joints J1 to J3 without the robot 200 colliding with a person or object. In other words, this phrase means that the robot 200 does not contact a person or object, and no object collision occurs during product assembly, thus no torque is generated. Normally, when operating a robot, even when the robot does not collide with a person or object, a load is generated due to gravity and the robot's operation. Therefore, even without a collision with a person or object, the torque sensors included in each joint of the robot detect torque depending on the robot's orientation and operation. Therefore, a correction value needs to be obtained by acquiring trajectory data based on the robot's orientation and operation. The trajectory data to be obtained is a profile of the rotation angle of the waveform generator 151. That is, the CPU 651 obtains the correction value based on the rotation angle of the waveform generator 151, which serves as the trajectory data. Furthermore, this correction value corresponds to the phase Φ10'+Φ10" expressed by equation (6) when the robot 200 is operated without load. That is, by operating the robot 200 without load, a profile corresponding to the error of phase Φ12 is obtained as the correction value. By calculating the correction value according to the robot's orientation and operation in this way, for example, when the robot system of this embodiment is applied to a human collaborative robot, the contact force between the robot and a person or object can be accurately detected.

[0186] Control methods and references for robot 200 in manufacturing processes Figure 11A The flowchart shown in the figure is the same as the control method described in the first embodiment, therefore its description will be omitted. The detection is performed as follows... Figure 11A The torque value τ obtained by the robot control device 300 in step S102. Figure 22B This is a flowchart illustrating an example of a torque detection method according to a third embodiment. Here, Figure 22B The steps S201B to S204B shown in the figure are arithmetic processes performed by the displacement calculation unit 680, and step S204B is arithmetic processes performed by the torque calculation unit 681.

[0187] In step S201B, the displacement calculation unit 680 loads correction values ​​from table data 671B.

[0188] Next, in step S202B, the displacement calculation unit 680 detects the phase Φ12, which is the displacement amount in the X direction, from the pattern row 802. That is, the displacement calculation unit 680 obtains the displacement amount in the X direction of the scale 2B relative to the sensor head 7B as the phase Φ12 by using the sine wave signals S2(A) and S2(B) from the circuit unit 51. The phase Φ12 is obtained by equation (5) of the first embodiment described above. The phase Φ12 satisfies equation (6) of the first embodiment described above. The correction value loaded in step S201B corresponds to the error Φ10'+Φ10 in equation (6).

[0189] Therefore, in step S203B, the displacement calculation unit 680 corrects the phase Φ12 by using a correction value, that is, by subtracting the correction value from the phase Φ12 to obtain the phase Φ10.

[0190] The processing in step S204B is essentially the same as that in step S205 described in the first embodiment. That is, in step S204B, the torque calculation unit 681 obtains the torque value τ based on the four phases Φ10 obtained for the four encoders 510 respectively.

[0191] As described above, according to the third embodiment, the torque value τ can be obtained with high precision. That is, the detection accuracy of the torque value τ is improved. Since the torque value τ can be obtained with high precision, the operating accuracy of the robot can be improved. In addition, the size of the encoder 510B can be reduced, and therefore the size of the torque sensor 500 and the robot 200 can also be reduced.

[0192] It should be noted that the present invention is not limited to the above embodiments and can be modified in many ways within the scope of the inventive concept. Furthermore, the effects described in the embodiments merely illustrate the most preferred effects obtainable by the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0193] While the above embodiments have described the case where the robotic arm 201 is a vertically articulated robotic arm, the configuration is not limited to this. For example, various robotic arms such as horizontally articulated robotic arms, parallel-linked robotic arms, and orthogonal robots can be robotic arm 201.

[0194] Furthermore, although the above embodiments describe a torque sensor deployed on the output side of the reduction gear, the configuration is not limited to this, and the torque sensor can also be deployed on the input side of the reduction gear. It is sufficient that the torque sensor is deployed at the location where the elliptical deformation force of the reduction gear is transmitted to the joint or drive mechanism.

[0195] Additionally, although the above embodiments describe the case where the encoder is an incremental encoder, the configuration is not limited to this, and the encoder can be an absolute encoder.

[0196] Furthermore, although the above embodiments describe a torque sensor comprising four encoders, the configuration is not limited to this. For example, it is also possible for the torque sensor to include only one encoder. In this case, when calculating the torque value τ, it is not necessary to calculate the averaging of phase τ10. Of course, it is preferable that the torque sensor includes four encoders, and the error of the detected phase can be reduced by averaging the four phases Φ10 detected by the four encoders.

[0197] Furthermore, although the above embodiments have described a case where the reduction gear is a strain wave reduction gear and the flexible gear of the strain wave reduction gear has a cup shape, the configuration is not limited to this. The flexible gear can have a shape different from a cup shape, for example, a top hat shape.

[0198] Furthermore, although a case has been described in which a CPU 651 implements the functions of multiple displacement calculation units 680 and torque calculation units 681, the configuration is not limited to this, and these functions can be implemented by multiple CPUs.

[0199] As described above, the detection accuracy can be improved according to the present invention.

[0200] Other embodiments

[0201] One or more embodiments of the present invention can also be implemented by a computer that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transient computer-readable storage medium") to perform the functions of one or more embodiments described above and / or includes one or more circuits (e.g., application-specific integrated circuits (ASICs)) for performing the functions of one or more embodiments described above, and by a method executed by a computer of a system or device, for example, by reading and executing computer-executable instructions from a storage medium to perform the functions of one or more embodiments described above and / or controlling one or more circuits to perform the functions of one or more embodiments described above. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessor unit (MPU)) and may include a network of individual computers or individual processors to read and execute the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or storage medium. The storage medium may include, for example, a hard disk, random access memory (RAM), read-only memory (ROM), storage devices for distributed computing systems, optical discs (such as CDs, DVDs, or Blu-ray discs). TM One or more of the following: flash memory devices, memory cards, etc.

[0202] Other embodiments

[0203] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads and executes the program.

[0204] While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to include all such modifications and equivalent structures and functions.

Claims

1. A robot system comprising: a robot including a reduction gear and at least one encoder in a joint thereof; a support portion fixed to the reduction gear; and a processing portion, wherein the encoder includes: a scale including a pattern portion, and a head portion disposed opposite the scale and configured to read the pattern portion of the scale and output a detection signal, wherein the pattern portion includes: at least one first pattern row including a plurality of first pattern elements arranged periodically in a first direction, the plurality of first pattern elements each having a shape symmetrical with respect to a first axis extending in a second direction, and at least one second pattern row including a plurality of second pattern elements arranged periodically in the first direction, the plurality of second pattern elements each having a shape asymmetrical with respect to a second axis extending in the second direction, and wherein phase information includes first information obtained by the head portion reading the at least one first pattern row and second information obtained by the head portion reading the at least one second pattern row, and wherein the processing portion is configured to: obtain a first displacement amount of the support portion in the first direction from the first information, and obtain a second displacement amount of the support portion in the second direction from the second information and the first displacement amount, wherein one of the scale and the head portion is supported by the support portion, and wherein a rotational direction of the reduction gear is defined as the first direction and a radial direction of the reduction gear is defined as the second direction, and wherein the processing portion is configured to: obtain an ellipticity of the support portion from the first displacement amount and the second displacement amount, obtain an error in the first direction of a relative displacement of the scale with respect to the head portion in the first direction resulting from an elliptical deformation of the support portion based on a difference between the ellipticity of the support portion and a distance from a rotational axis of the support portion to which a deformation force is not received, correct the first displacement amount based on the error, and calculate a torque value based on the corrected displacement amount in the first direction. The at least one second pattern row includes a plurality of second pattern rows arranged continuously in the second direction.

2. The robotic system of claim 1, wherein, 3. The robot system according to claim 1, the at least one first pattern row includes a plurality of first pattern rows, wherein, wherein the at least one second pattern row includes a plurality of second pattern rows, and wherein the plurality of first pattern rows and the plurality of second pattern rows are arranged alternately in the second direction. The reduction gear is a strain wave reduction gear.

4. The robotic system of claim 1, wherein, 5. A torque sensor comprising: at least one encoder disposed in a drive device including a reduction gear; a support portion fixed to the reduction gear; and a processing portion, wherein the encoder includes: a scale including a pattern portion, and a head portion disposed opposite the scale and configured to read the pattern portion of the scale and output a detection signal, wherein the pattern portion includes: at least one first pattern row including a plurality of first pattern elements arranged periodically in a first direction, the plurality of first pattern elements each having a shape symmetrical with respect to a first axis extending in a second direction, and at least one second pattern row including a plurality of second pattern elements arranged periodically in the first direction, the plurality of second pattern elements each having a shape asymmetrical with respect to a second axis extending in the second direction, and at least one first pattern row including a plurality of first pattern elements arranged periodically in a first direction, the plurality of first pattern elements each having a shape symmetrical with respect to a first axis extending in a second direction, and at least one second pattern row including a plurality of second pattern elements arranged periodically in the first direction, the plurality of second pattern elements each having a shape asymmetrical with respect to a second axis extending in the second direction, and wherein the phase information includes first information obtained by the head reading the at least one first pattern row and second information obtained by the head reading the at least one second pattern row, and wherein the processing portion is configured to: obtain a first displacement amount of the support portion in the first direction from the first information, and obtain a second displacement amount of the support portion in the second direction from the second information and the first displacement amount, and wherein one of the scale and the head is supported by the support portion, and wherein a rotational direction of the reduction gear is defined as the first direction and a radial direction of the reduction gear is defined as the second direction, and wherein the processing portion is configured to: obtain an ellipticity of the support portion from the first displacement amount and the second displacement amount, obtain an error in the first direction of a relative displacement of the scale with respect to the head in the first direction caused by an elliptical deformation of the support portion from a difference between the ellipticity of the support portion and a distance from a rotational axis of the support portion to which the deformed force is not applied, correct the first displacement amount based on the error, and calculate a torque value based on the corrected displacement amount in the first direction.

6. A displacement detecting apparatus, comprising: at least one encoder disposed in a driving apparatus including a reduction gear; a support portion fixed to the reduction gear; and a processing portion, wherein the encoder includes: a scale including a pattern portion, and a head disposed opposite the scale and configured to read the pattern portion of the scale and output a detection signal, wherein the pattern portion includes: at least one first pattern row including a plurality of first pattern elements arranged periodically in a first direction, the plurality of first pattern elements each having a shape symmetrical with respect to a first axis extending in a second direction, and at least one second pattern row including a plurality of second pattern elements arranged periodically in the first direction, the plurality of second pattern elements each having a shape asymmetrical with respect to a second axis extending in the second direction, and wherein the phase information includes first information obtained by the head reading the at least one first pattern row and second information obtained by the head reading the at least one second pattern row, and wherein the processing portion is configured to: obtain a first displacement amount of the support portion in the first direction from the first information, and obtain a second displacement amount of the support portion in the second direction from the second information and the first displacement amount, and wherein one of the scale and the head is supported by the support portion, and wherein a rotational direction of the reduction gear is defined as the first direction and a radial direction of the reduction gear is defined as the second direction, and wherein the processing portion is configured to: obtain an ellipticity of the support portion from the first displacement amount and the second displacement amount, obtain an error in the first direction of a relative displacement of the scale with respect to the head in the first direction caused by an elliptical deformation of the support portion from a difference between the ellipticity of the support portion and a distance from a rotational axis of the support portion to which the deformed force is not applied, correct the first displacement amount based on the error, and calculate a torque value based on the corrected displacement amount in the first direction. wherein a rotational direction of the reduction gear is defined as a first direction, and a radial direction of the reduction gear is defined as a second direction, and wherein the processing section is configured to: obtain an ellipticity of the support section from the first displacement amount and the second displacement amount, obtain an error in the first direction of a relative displacement of the scale with respect to the head in the first direction caused by an elliptical deformation of the support section based on a difference between the ellipticity of the support section and a distance from a rotational axis of the support section to which the deforming force is not received, correct the first displacement amount based on the error, and calculate a torque value based on the corrected displacement amount in the first direction.

7. A detection method for a torque sensor, the torque sensor comprising an encoder, a support portion, and a processing portion, the encoder portion being disposed in a driving device including a reduction gear, the support portion being fixed to the reduction gear, the encoder including a scale and a head portion, the scale including a pattern portion, the head portion being disposed opposite the scale and configured to read the pattern portion of the scale and output a detection signal, the pattern portion comprising: at least one first pattern row including a plurality of first pattern elements arranged periodically in a first direction, the plurality of first pattern elements each having a shape symmetrical with respect to a first axis extending in a second direction, and at least one second pattern row including a plurality of second pattern elements arranged periodically in the first direction, the plurality of second pattern elements each having a shape asymmetrical with respect to a second axis extending in the second direction, the phase information including first information and second information, the first information being obtained by the head reading the at least one first pattern row, and the second information being obtained by the head reading the at least one second pattern row, one of the scale and the head being supported by a support section, a rotational direction of the reduction gear being defined as a first direction, and a radial direction of the reduction gear being defined as a second direction, the detection method including: obtaining, by the processing section, a first displacement amount of the support section in the first direction from the first information, obtaining, by the processing section, a second displacement amount of the support section in the second direction from the second information and the first displacement amount, obtaining, by the processing section, an ellipticity of the support section from the first displacement amount and the second displacement amount, obtaining, by the processing section, an error in the first direction of a relative displacement of the scale with respect to the head in the first direction caused by an elliptical deformation of the support section based on a difference between the ellipticity of the support section and a distance from a rotational axis of the support section to which the deforming force is not received, correcting, by the processing section, the first displacement amount based on the error, and calculating, by the processing section, a torque value based on the corrected displacement amount in the first direction.

8. A method for manufacturing a product by using the robot system according to any one of claims 1 to 4.

9. A computer-readable recording medium recording a program for causing a computer to execute the detection method according to claim 7.

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