JP2021089206A - Angle detection method, encoder unit, and robot - Google Patents

Abstract

To provide an angle detection method and an encoder unit that can improve detection accuracy, and to provide a robot including the encoder unit.SOLUTION: A method for detecting a rotation angle by using an encoder having a scale unit including first marks and second marks, a first image pick-up device, and a second image pick-up device arranged at a position symmetrical thereto, includes the steps of: acquiring a first [i] template image when the scale unit is at a [i]-th calibration angle; acquiring a second [i] template image when the scale unit is at the [i]-th calibration angle; determining the correlation relationship established between the amount of change of the [i]-th calibration angle, the amount of movement of the first marks, and the amount of movement of the second marks; determining a first angle measurement movement amount of the first marks by template matching; determining a second angle measurement movement amount of the second marks by template matching; and determining a measurement angle based on the [i]-th calibration angle, first angle measurement movement amount, second angle measurement movement amount, and correlation relationship.SELECTED DRAWING: Figure 10

Description

The present invention relates to an angle detection method, an encoder unit and a robot.

Conventionally, an optical rotary encoder is known as a kind of encoder. For example, the rotary encoder described in Patent Document 1 includes a scale plate, a code pattern provided near the periphery of the scale plate, and a pair of CCD linear sensors that read a code pattern at a symmetrical position. In this rotary encoder, the eccentricity factor related to the eccentricity of the dial is stored in advance, and the measured value is corrected by the eccentricity factor to remove the angle error due to the eccentricity.

Japanese Unexamined Patent Publication No. 2007-178320

Since the output shafts of speed reducers, motors, etc. cause shaft runout (dynamic eccentricity) as they rotate, eccentricity is caused by using an eccentric factor stored in advance as in the method described in Patent Document 1. Even if an attempt is made to remove the angle error, the error caused by the shaft runout cannot be reduced. For this reason, the conventional rotary encoder has a problem that it is difficult to improve the detection accuracy when the shaft runout is involved.

The angle detection method according to the application example of the present invention is
A scale unit having a plurality of marks including the first mark and the second mark arranged in an annular shape around the rotation axis, a first image sensor that images the first mark, and the first image pickup with respect to the rotation axis. It has a second image sensor that is arranged at a position symmetrical to the element and images the second mark, and the scale portion is around the rotation axis with respect to the first image sensor and the second image sensor. An angle detection method for detecting the rotation angle of the rotation shaft using a relatively rotating encoder.
When the scale unit is at the first [i] calibration angle, the first mark is imaged by the first image sensor to generate a first [i] reference image, and the first [i] template image and the first [I] A step of acquiring the first [i] reference coordinates of the first mark in the reference image, and
When the scale unit is at the [i] calibration angle, the second mark is imaged by the second image sensor to generate a second [i] reference image, and the second [i] template image and the first 2 [i] A step of acquiring the second [i] reference coordinates of the second mark in the reference image, and
[I] When the calibration angle is changed, the step of obtaining the correlation established between the amount of change, the amount of movement of the first mark, and the amount of movement of the second mark.
When the scale unit is at the measurement angle, the first mark is imaged by the first image sensor to generate a first angle measurement image, and the first is performed by template matching based on the first [i] template image. The step of obtaining the first angle-measurement movement amount from the first [i] reference coordinate of the first mark in the angle-measurement image, and
When the scale unit is at the measurement angle, the second mark is imaged by the second image sensor to generate a second angle measurement image, and template matching based on the second [i] template image is performed to obtain the second mark. 2. A step of obtaining the second angle movement amount of the second mark from the second [i] reference coordinate in the angle measurement image, and
The step of obtaining the measurement angle based on the first [i] calibration angle, the first angle movement amount, the second angle measurement movement amount, and the correlation.
It is characterized by having.

It is a side view which shows the robot which concerns on embodiment. It is sectional drawing which shows the encoder unit which concerns on 1st Embodiment. It is a functional block diagram which shows the encoder of FIG. It is a figure for demonstrating the scale part provided in the encoder of FIG. It is an enlarged view of E1 part of the scale part shown in FIG. It is an enlarged view of E2 part of the scale part shown in FIG. It is a partially enlarged view of the scale part shown in FIG. It is a flowchart which shows the angle detection method which concerns on 1st Embodiment. Of the angle detection methods shown in FIG. 8, it is a flowchart showing step S1 in detail. It is a figure for demonstrating step S1 shown in FIG. It is a list which shows the calibration angle, the template image, the reference coordinate, and the coefficient acquired by the angle detection method shown in FIG. It is a flowchart which shows step S1 in detail in the angle detection method which concerns on 2nd Embodiment. It is a list which shows the calibration angle, the template image, the reference coordinate, and the coefficient acquired by the angle detection method shown in FIG. It is a flowchart which shows step S1 in detail among the angle detection method which concerns on 3rd Embodiment. It is a list which shows the calibration angle, the template image, the reference coordinate, and the coefficient acquired by the angle detection method shown in FIG. It is a flowchart which shows step S1 in detail in the angle detection method which concerns on 4th Embodiment. It is a list which shows the calibration angle, the template image, the reference coordinate, and the coefficient acquired by the angle detection method shown in FIG.

Hereinafter, preferred embodiments of the angle detection method, encoder unit, and robot of the present invention will be described in detail with reference to the accompanying drawings.

1. 1. Robot FIG. 1 is a side view showing a robot according to an embodiment. In the following, for convenience of explanation, the upper side in FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”. Further, the base side in FIG. 1 is referred to as a "base end side", and the opposite side is referred to as a "tip side".

The robot 100 shown in FIG. 1 is a so-called horizontal articulated robot (SCARA robot), and is used, for example, in a manufacturing process for manufacturing precision equipment and the like, and can grip and transport precision equipment and parts. ..

As shown in FIG. 1, the robot 100 has a base 110, a first arm 120, a second arm 130, a work head 140, an end effector 150, and a wiring routing portion 160. Hereinafter, each part of the robot 100 will be briefly described in sequence.

The base 110 is fixed to, for example, a floor surface (not shown) with bolts or the like. The first arm 120 is connected to the upper end of the base 110. The first arm 120 is rotatable around the first axis J1 passing through the base 110.

A motor 111 that generates a driving force for rotating the first arm 120 and a speed reducer 112 that reduces the driving force of the motor 111 are installed in the base 110. The input shaft of the speed reducer 112 is connected to the rotation shaft of the motor 111, and the output shaft of the speed reducer 112 is connected to the first arm 120. Therefore, when the motor 111 is driven and the driving force is transmitted to the first arm 120 via the speed reducer 112, the first arm 120 rotates around the first axis J1 with respect to the base 110.

Further, the base 110 and the first arm 120 are encoders that are first encoders that detect the rotational state of the first arm 120 with respect to the base 110 by detecting the rotation angle of the output shaft of the speed reducer 112. 1 is provided.

A second arm 130 is connected to the tip of the first arm 120. The second arm 130 is rotatable around the second axis J2 with respect to the first arm 120. Although not shown, a second motor that generates a driving force for rotating the second arm 130 and a speed reducer that reduces the driving force of the second motor are installed in the second arm 130. Then, the driving force of the second motor is transmitted to the first arm 120 via the speed reducer, so that the second arm 130 rotates around the second axis J2 with respect to the first arm 120. Further, although not shown, the second motor is provided with an encoder different from the encoder 1 described above, which detects the rotational state of the second arm 130 with respect to the first arm 120.

A work head 140 is arranged at the tip of the second arm 130. The working head 140 has a spline shaft 141 inserted through a spline nut (not shown) and a ball screw nut (not shown) coaxially arranged at the tip of the second arm 130. The spline shaft 141 can rotate around the third axis J3 with respect to the second arm 130, and can move (up and down) in the vertical direction.

Although not shown, a rotary motor and an elevating motor are arranged in the second arm 130. The driving force of the rotary motor is transmitted to the spline nut by a driving force transmission mechanism (not shown), and when the spline nut rotates forward and reverse, the spline shaft 141 rotates forward and reverse around the third axis J3 along the vertical direction. Further, although not shown, the rotary motor is provided with an encoder different from the encoder 1 described above, which detects the rotational state of the spline shaft 141 with respect to the second arm 130.

On the other hand, the driving force of the elevating motor is transmitted to the ball screw nut by a driving force transmission mechanism (not shown), and when the ball screw nut rotates in the forward and reverse directions, the spline shaft 141 moves up and down. The elevating motor is provided with an encoder different from the encoder 1 described above, which detects the amount of movement of the spline shaft 141 with respect to the second arm 130.

An end effector 150 is connected to the tip end portion (lower end portion) of the spline shaft 141. The end effector 150 is not particularly limited, and examples thereof include those that grip an object to be transported, those that process an object to be processed, and the like.

A plurality of wirings connected to each electronic component arranged in the second arm 130, for example, a second motor, a rotary motor, an elevating motor, each encoder, etc., are tubular connecting the second arm 130 and the base 110. It is routed to the base 110 through the wiring route 160 of the above. Further, such a plurality of wirings are grouped in the base 110, and together with the wirings connected to the motor 111 and the encoder 1, are installed outside the base 110 to a control device (not shown) that controls the robot 100 in an integrated manner. Be routed.

The configuration of the robot 100 has been briefly described above. As described above, the robot 100 has a base 110 which is a first member and a first arm which is a second member which rotates with respect to the base 110. A 120 and an encoder unit 10 are provided. Here, the encoder unit 10 according to the present embodiment is a speed reducer 112 having an output shaft that rotates around a rotation shaft and outputs a driving force, and an encoder 1 that detects the rotation angle of the output shaft of the speed reducer 112. And have. A speed reducer 112 is installed in the base 110, and the output shaft of the speed reducer 112 is connected to the first arm 120. According to such a robot 100, as will be described later, the rotation angle of the first arm 120 can be detected with high accuracy, and the drive control of the first arm 120 can be performed with high accuracy based on the detection result. ..

2. First Embodiment 2.1. Encoder Unit Hereinafter, the encoder unit 10 according to the first embodiment will be described. The encoder unit 10 is incorporated in various devices, but the case where the encoder unit 10 is incorporated in the robot 100 will be described below as an example.

FIG. 2 is a cross-sectional view showing an encoder unit according to the first embodiment. FIG. 3 is a functional block diagram showing the encoder of FIG. FIG. 4 is a diagram for explaining a scale unit included in the encoder of FIG. FIG. 5 is an enlarged view of the E1 portion of the scale portion shown in FIG. FIG. 6 is an enlarged view of the E2 portion of the scale portion shown in FIG. FIG. 7 is a partially enlarged view of the scale portion shown in FIG. In FIGS. 2 and 4 to 7, the scale of each part is appropriately changed for convenience of explanation, the structure shown does not necessarily match the actual scale, and the illustration of each part is simplified as appropriate. ing.

As shown in FIG. 2, the base 110 of the robot 100 described above has a support member 114 that supports the motor 111 and the speed reducer 112, and houses the motor 111 and the speed reducer 112. With respect to such a base 110, the first arm 120 is rotatable around the first axis J1.

The first arm 120 has an arm main body 121 extending to the left and right in FIG. 2 and a shaft portion 122 protruding downward from the arm main body 121, and these are connected to each other. The shaft portion 122 is rotatable around the first shaft J1 with respect to the base 110 via the bearing 115, and is connected to the output shaft of the speed reducer 112. Further, the input shaft of the speed reducer 112 is connected to the rotation shaft 1111 of the motor 111. The speed reducer 112 is not particularly limited, and examples thereof include a wave speed reducer, a planetary gear speed reducer, a cyclo speed reducer, and an RV speed reducer.

Here, the base 110 is a structure to which a load due to its own weight or another mass supported by the base 110 is applied. Similarly, the first arm 120 is also a structure to which a load due to its own weight or another mass supported by the first arm 120 is applied. The constituent materials of the base 110 and the first arm 120 are not particularly limited, and examples thereof include a metal material.

In the present embodiment, the outer surfaces of the base 110 and the first arm 120 form a part of the outer surface of the robot 100. An exterior member such as a cover or a shock absorbing material may be mounted on the outer surfaces of the base 110 and the first arm 120.

Such a relatively rotating base 110 and the first arm 120 are provided with an encoder 1 for detecting these rotating states.

The encoder 1 includes a scale unit 2 provided on the first arm 120, a first detection unit 3a and a second detection unit 3b provided on the base 110, and a first detection unit 3a and a second detection unit 3b. It has a circuit unit 4 electrically connected to the circuit unit 4. The circuit unit 4 includes a processing unit 5 and a storage unit 6.

As shown in FIG. 2, the scale portion 2 is provided on a portion of the arm main body portion 121 facing the base 110, that is, a portion on the lower surface of the arm main body portion 121 that surrounds the shaft portion 122. As shown in FIG. 4, the scale portion 2 has a dot pattern arranged around the first axis J1 at a position different from that of the first axis J1.

The scale portion 2 is provided on the surface of the first arm 120, for example. As a result, it is not necessary to provide a member for providing the scale portion 2 separately from the first arm 120. Therefore, the number of parts can be reduced. The scale portion 2 is not limited to the case where it is provided directly on the surface of the first arm 120, and may be provided on, for example, a sheet-like member attached to the surface of the first arm 120. However, it may be provided on a plate-shaped member provided so as to rotate together with the first arm 120. That is, the member provided with the scale portion 2 may be a member that rotates around the first axis J1 with respect to the base 110 together with the first arm 120.

As shown in FIGS. 4 to 7, the scale unit 2 has a plurality of marks 21 in which a plurality of dots 20 are arranged in a row. The plurality of marks 21 are arranged at substantially equal intervals along the circumference centered on the first axis J1. In the following description, the direction in which the radius of the circle centered on the first axis J1 extends is referred to as "radial DR", and the direction orthogonal to the radial DR is referred to as "circumferential DC".

As shown in FIGS. 5 and 6, the mark 21 has a shape in which the length in the radial direction DR is longer than the length in the circumferential direction DC, respectively. As shown in FIG. 7, the mark 21 has a plurality of dots 20 arranged in a row along the radial DR, and the rows are arranged in four rows along the circumferential direction DC. In each column, some dots 20 are displaced along the circumferential DC, and the pattern of the deviation of the dots 20 functions as a unique identifier that uniquely identifies the mark 21. In the present embodiment, a row formed by four dots 20 arranged in the radial direction DR is set as one unit, and 16 dots 20 in which the units are arranged in four rows in the circumferential direction DC are used in template matching described later. An array pattern that can be a template image is configured. Therefore, each mark 21 contains an arrangement pattern different from that of the other marks 21.

Then, when the scale portion 2 having such a mark 21 is rotated around the first axis J1, the same array pattern does not appear more than once in a predetermined region in the captured image described later. In the specification of the present application, having such distinctiveness is referred to as "unique", and a unique pattern is referred to as "unique pattern UP". If the unique unique pattern UP included in each mark 21 can be identified, the absolute position of the scale portion 2 in the circumferential direction can be identified.

Further, it is preferable that the unique pattern UP is repeatedly included in the radial DR of the mark 21. As a result, even when the imaging region RI1 shown in FIG. 5 and the imaging region RI2 shown in FIG. 6 are displaced in the radial direction, the unique pattern UP can be captured in these regions.

The positions, sizes, numbers, arrangement patterns, and the like of the dots 20 shown in FIG. 7 are examples, and are not limited thereto. Further, contrary to FIG. 2, the scale unit 2 may be arranged on the base 110 side, and the detection units 3a and 3b may be arranged on the first arm 120 side.

The mark 21 shown in each figure is configured by uniquely arranging a plurality of black dots 20 on a white background. The shape of the dot 20 is circular in the drawing, but is not limited to this, and may be, for example, an ellipse, a quadrangle, or an irregular shape. Further, the mark 21 is not limited to a dot pattern composed of a plurality of dots 20, and for example, a pattern composed of linear lines, a pattern composed of curved lines, dots, linear lines, and the like. The pattern may be composed of a combination of at least two of the curved lines. Further, the mark 21 may be a pattern in which the white background and the black dots or lines of the above-mentioned pattern are inverted, that is, a pattern of the black background and the white dots or lines. Further, the dots 20 may be formed of, for example, an ink such as a dye or a pigment, or may have an uneven shape.

Further, the mark 21 is not limited to the one using a pattern such as a dot 20, and may include, for example, a number, a character such as a Roman character, an Arabic character, or a Chinese character, or a character. Other symbols, codes, marks, marks, designs, one-dimensional barcodes, QR codes (registered trademarks) and the like may be included.

The first detection unit 3a shown in FIG. 2 includes a first image sensor 31a provided in the base 110 and a first optical system 32a provided in the opening of the base 110. 1 The image sensor 31a images a part of the circumferential direction DC of the scale unit 2, specifically, the image pickup region RI1 of FIG. 5 via the first optical system 32a. The angle of view of the imaging region RI1 is preferably set to an angle at which a plurality of marks 21 can be captured in the same image. If necessary, a light source that illuminates the image pickup region RI1 of the first image sensor 31a may be provided.

Examples of the first image sensor 31a include CCD (Charge Coupled Devices), CMOS (Complementary Metal Oxide Semiconductor), and the like. Such a first image sensor 31a converts the captured image into an electric signal for each pixel and outputs the image. The first image sensor 31a may be either a two-dimensional image sensor (area image sensor) or a one-dimensional image sensor (line image sensor). It is desirable that the one-dimensional image sensor is arranged in a direction in which the arrangement of pixels is in contact with the swirling circle of the arm. When a two-dimensional image sensor is used, a two-dimensional image having a large amount of information can be generated, and it is easy to improve the detection accuracy of the dot 20 by template matching described later. As a result, the rotational state of the first arm 120 can be detected with high accuracy. When a one-dimensional image sensor is used, since the image sampling cycle, that is, the frame rate, is high, it is possible to increase the detection frequency, which is advantageous during high-speed operation. In the present embodiment, the first image sensor 31a is a two-dimensional image sensor.

The first optical system 32a is an imaging optical system arranged between the scale unit 2 and the first image pickup device 31a. It is preferable that at least the object side (scale portion 2 side) of the first optical system 32a is telecentric. As a result, even if the distance between the scale unit 2 and the first image sensor 31a fluctuates, the change in the imaging magnification to the first image sensor 31a can be reduced, and as a result, the detection accuracy of the encoder 1 can be reduced. Can be reduced. In particular, when the first optical system 32a is telecentric on both sides, even if the distance between the lens of the first optical system 32a and the first image sensor 31a fluctuates, the image magnification on the first image sensor 31a is increased. The change can be reduced. Therefore, there is an advantage that the first optical system 32a can be easily assembled.

Here, as shown in FIG. 5, the image pickup region RI1 of the first image pickup device 31a is set so as to overlap a part of the scale unit 2 in the circumferential direction DC. As a result, the first image sensor 31a can image the dots 20 in the image pickup region RI1. Therefore, by reading the dot 20 in the circuit unit 4, the rotational state of the first arm 120 can be known.

On the other hand, the second detection unit 3b is arranged at a position symmetrical to the first detection unit 3a with respect to the first axis J1 which is the rotation axis. The second detection unit 3b is configured in the same manner as the first detection unit 3a described above. That is, the second detection unit 3b has a second image sensor 31b provided in the base 110 and a second optical system 32b provided in the opening of the base 110, and the second image pickup is performed. The element 31b images a part of the scale unit 2 in the circumferential direction via the second optical system 32b, specifically, the image pickup region RI2 of FIG.

It is preferable that the second image sensor 31b images the scale unit 2 with the same resolution as the first image sensor 31a. This simplifies the calculation when calculating the rotation angle of the scale unit 2 by the method described later. From this point of view, the second image sensor 31b preferably has the same size and number of pixels as the first image sensor 31a, and the second optical system 32b has the same magnification as the first optical system 32a. Is preferable.

The symmetrical position means that the first image sensor 31a and the second image sensor 31b point to each other with the first axis J1 as the axis of symmetry when viewed from the direction along the first axis J1 which is the rotation axis. A position that satisfies a symmetrical relationship. However, some deviation is allowed in this position. For example, the angle formed by the line segment connecting the center of the first imaging element 31a and the first axis J1 and the line segment connecting the center of the second imaging element 31b and the first axis J1 is point-symmetrical as described above. When the relationship is completely satisfied, it becomes 180 °, but a deviation of about 180 ± 6 ° is allowed. Even if there is such a deviation, the effect of the present embodiment can be obtained.

The circuit unit 4 shown in FIGS. 2 and 3 includes a processing unit 5 (processor) which is a processing device, and a storage unit 6 (memory) such as a ROM (Read only memory) and a RAM (Random Access Memory). Here, the storage unit 6 stores instructions and information that can be read by the processing unit 5, and the processing unit 5 realizes various functions by appropriately reading and executing the instructions and information from the storage unit 6. To do. Such a circuit unit 4 can be configured by using, for example, a microcomputer, an ASIC (application specific integrated circuit), an FPGA (field-programmable gate array), or the like. In particular, by hardwareizing the circuit unit 4 using an ASIC or FPGA, it is possible to increase the processing speed, reduce the size, and reduce the cost of the circuit unit 4. At least a part of the circuit unit 4 may be incorporated in the control device of the robot 100 described above.

The processing unit 5 estimates the relative rotational state of the base 110 and the first arm 120 based on the detection results of the first detection unit 3a and the second detection unit 3b. Examples of the rotation state include a rotation angle, a rotation speed, a rotation direction, and the like.

In particular, the processing unit 5 recognizes the unique pattern UP by template matching using the template image with respect to the captured images of the first image sensor 31a and the second image sensor 31b, and uses the recognition result to base the image. The relative rotation state of the first arm 120 with respect to the base 110 is estimated. In this way, by estimating the rotational state using the captured images of both the first image sensor 31a and the second image sensor 31b, it is caused by the shaft runout (eccentricity) accompanying the rotation of the output shaft of the speed reducer 112. The detection error can be reduced. As a result, the detection accuracy can be improved as compared with the case where the rotational state is estimated using only either the first image sensor 31a or the second image sensor 31b. This point will be described in detail later.

Further, the processing unit 5 makes the relative rotation angle of the first arm 120 with respect to the base 110 finer based on the positions of the unique patterns UP in the captured images of the first image sensor 31a and the second image sensor 31b. It has a function to estimate. Further, the processing unit 5 obtains the rotation speed based on the time interval in which the unique pattern UP is detected and the movement amount of the unique pattern UP, and determines the rotation direction based on the order of the types of the detected unique pattern UP. It also has a function to estimate. Then, the processing unit 5 outputs a signal corresponding to the above-mentioned estimation result, that is, a signal corresponding to the relative rotation state of the first arm 120 with respect to the base 110. This signal is input to, for example, a control device (not shown) and used to control the operation of the robot 100.

In addition, the processing unit 5 has a function of cutting out a part of the image captured by the first image sensor 31a and the image captured by the second image sensor 31b to generate a template image. The generation of this template image is prior to estimating the rotational state of the first arm 120 relative to the base 110, or as needed, relative to the first arm 120 relative to the base 110. It is performed at each predetermined calibration angle in the rotation angle. Then, the generated template image is stored in the storage unit 6 corresponding to each calibration angle. Then, the processing unit 5 performs template matching using the template image stored in the storage unit 6. The template matching and the estimation of the rotation state using the template matching will be described in detail later.

The processing unit 5 may be configured to include both a device (internal device) provided inside the base 110 and a device (external device) provided outside the base 110. In this case, the external device is composed of, for example, a personal computer. The external device preferably has a function of cutting out a part of the captured image to generate a template image. By assigning this function to the external device, the function of the internal device can be simplified, and it becomes easy to reduce the size and cost of the base 110.

In addition to instructions (programs) that can be read by the processing unit 5, various information (data) that can be read by the processing unit 5 is stored in the storage unit 6. Specifically, in the storage unit 6, the above-mentioned captured image relates to the coordinates (reference coordinates) of the unique pattern UP in the captured image for each relative rotation state of the first arm 120 with respect to the base 110. It is stored together with the information and the information (angle information) regarding the rotation angle of the first arm 120. Such a storage unit 6 may be either a non-volatile memory or a volatile memory, but can hold a state in which information is stored without supplying power, and power saving can be achieved. From the viewpoint of being able to do so, a non-volatile memory is preferable.

2.2. Angle detection method Next, the angle detection method according to the first embodiment will be described.

The angle detection method according to the first embodiment includes a step S1 for acquiring a template image and information related thereto, and a step S2 for detecting the rotation angle of the scale unit 2 based on the acquired template image. According to such an angle detection method, the detection accuracy can be improved even when the shaft runout is involved.

FIG. 8 is a flowchart showing the angle detection method according to the first embodiment. FIG. 9 is a flowchart showing step S1 in detail among the angle detection methods shown in FIG. FIG. 10 is a diagram for explaining step S1 shown in FIG. FIG. 11 is a list showing the calibration angle, the template image, the reference coordinates, and the coefficients acquired by the angle detection method shown in FIG.

Step S1 includes steps S101 to S118, as shown in FIG. Hereinafter, each step will be described.

2.2.1. Acquisition of template image, etc. In step S1 shown in FIG. 8, prior to estimating the relative rotation state of the first arm 120 with respect to the base 110 by using template matching, the template image used for template matching and related to the template image. Get a dataset that contains information. The acquisition of the template image or the like may be performed only once before the first template matching, but may be performed after that as needed. In that case, the template image used for template matching can be updated with the newly acquired template image.

In step S1, first, as step S101, the rotation shaft of the encoder 1 and a calibration encoder (not shown) are mechanically connected. The calibration encoder is an angle calibration encoder that detects the rotation angle of the rotation shaft of the encoder 1, that is, the rotation angle of the scale unit 2 with sufficiently high accuracy. As a result, highly accurate angle information can be added to the template image.

Next, in step S102, the rotation shaft of the encoder 1 is rotated to align the scale portion 2 with the start angle. The start angle is not particularly limited, but is a rotation angle when one of the plurality of marks 21 included in the scale unit 2 is captured in the image captured by the first image sensor 31a.

Here, the rotation angle of the rotation shaft of the encoder 1 detected by the calibration encoder, that is, the rotation angle of the scale unit 2 is defined as the calibration angle θ [i] (the [i] calibration angle). The variable i is a value corresponding to the number assigned to the mark 21 along the circumferential direction DC, and takes an integer from 0 to n corresponding to the number n + 1 of the marks 21 provided in the scale unit 2.

Next, in step S103, the variable i is set to 0. When the rotation axis of the encoder 1 is at the start angle described above, either mark 21 is captured in the image captured by the first image sensor 31a and the image captured by the second image sensor 31b, respectively.

Next, in step S104, the calibration angle θ [i] detected by the calibration encoder is stored in the storage unit 6. Here, since 0 is set as the variable i, the calibration angle θ [0] is stored.

Next, in step S105, the first image sensor 31a of the encoder 1 is made to image the mark 21. As a result, the captured image 1 [i] (first [i] reference image) is generated. Here, since 0 is set as the variable i, the captured image 1 [0] is generated. In the captured image 1 [0], the unique pattern UP (first mark) included in the mark 21 is captured. Further, the mark 21 is imaged by the second image sensor 31b of the encoder 1. As a result, the captured image 2 [i] (second [i] reference image) is generated. Here, since 0 is set as the variable i, the captured image 2 [0] is generated. The unique pattern UP (second mark) included in the mark 21 is also captured in the captured image 2 [0]. The generated captured image 1 [0] and captured image 2 [0] are temporarily stored in the storage unit 6.

Next, in step S106, it is determined whether or not the variable i is larger than 0. If the variable i is larger than 0, the process proceeds to steps S107 to S109. If the variable i is 0, the process proceeds to steps S110 to S118. Since the variable i is 0 at this point, steps S110 to S118 will be described first, and steps S107 to S109 will be described later.

In step S110, it is determined whether or not the variable i is n or less. If this variable i is n or less, it is necessary to continue to acquire the template image described later, so the process proceeds to step S111. When the variable i is larger than n, that is, when it is n + 1, it means that the acquisition of the template image is completed for all the marks 21, so the step flow for acquiring the template image and the like is completed. Since the variable i is 0 at this point, step S111 and the like will be described first in the following description.

In step S111, the captured image 1 [i] (first [i] reference image) is read from the storage unit 6, and the captured image 1 [i] is included so that the unique pattern UP (first mark) is included without being missing. Determine the cutting position. Here, since 0 is set as the variable i, the cutout position of the captured image 1 [0] is determined.

In step S112, the coordinates of the upper left end of the cutout position in the captured image 1 [i] are set as the reference coordinates 1 [i] (first [i] reference coordinates). Here, since 0 is set as the variable i, as shown in FIG. 10, the coordinates of the upper left end of the cutout position in the captured image 1 [i] are set to the reference coordinates 1 [0] (first [0] reference coordinates. ).

In step S113, an image of the unique pattern UP is cut out based on the reference coordinate 1 [i] of the captured image 1 [i]. As a result, the template image 1 [i] (the first [i] template image) is acquired. Here, since 0 is set as the variable i, the template image 1 [0] (first [0] template image) is acquired as shown in FIG. The acquired template image 1 [0] and reference coordinates 1 [0] are stored in the storage unit 6. On the other hand, the temporarily stored captured image 1 [i] is subsequently overwritten when it is discarded at an arbitrary timing or when a new captured image is generated.

As described above, in the present embodiment, when the template image 1 [i] is acquired, the region including the unique pattern UP is selected as the cutout position from the captured image 1 [i] having a size larger than that of the unique pattern UP. , The method of adopting the image cut out from the template image 1 [i] is used. As a result, the template image 1 [i] can be acquired without increasing the formation accuracy of the unique pattern UP more than necessary. Therefore, the scale portion 2 can be easily formed and the formation cost can be reduced. In other words, even when the scale portion 2 having a low forming accuracy is used, the low forming accuracy can be made unquestioned when the template image 1 [i] is acquired.

FIG. 10 shows an example of the captured image 1 [0] captured when the rotation axis of the encoder 1 is at the calibration angle θ [0]. Among the plurality of marks 21 captured in the captured image 1 [0], the one close to the center of the image is selected, the unique pattern UP (first mark) is specified from the marks, and the area in which the unique pattern UP (first mark) is included without being missing is included. Is the cutout position. Then, the coordinates of the upper left end of the cutout position are obtained from the captured image 1 [0], and this is obtained as the reference coordinates 1 [0] (first [0] reference coordinates). Further, the image of the unique pattern UP included in the cutout position is cut out as the template image 1 [0] as shown in FIG.

In step S114, the captured image 2 [i] (second [i] reference image) is read from the storage unit 6, and the captured image 2 [i] is included so that the unique pattern UP (second mark) is included without being missing. Determine the cutting position. Here, since 0 is set as the variable i, the cutout position of the captured image 2 [0] is determined.

In step S115, the coordinates of the upper left end of the cutout position in the captured image 2 [i] are set as the reference coordinates 2 [i] (second [i] reference coordinates). Here, since 0 is set as the variable i, the coordinates of the upper left end of the cutout position in the captured image 2 [0] are set as the reference coordinates 2 [0] (second [0] reference coordinates).

In step S116, an image of the unique pattern UP is cut out based on the reference coordinate 2 [i] of the captured image 2 [i]. As a result, the template image 2 [i] (second [i] template image) is acquired. Here, since 0 is set as the variable i, the template image 2 [0] (second [0] template image) is acquired. The acquired template image 2 [0] and reference coordinates 2 [0] are stored in the storage unit 6. On the other hand, the temporarily stored captured image 2 [i] is subsequently overwritten when it is discarded at an arbitrary timing or when a new captured image is generated.

As described above, in the present embodiment, when the template image 2 [i] is acquired, the region including the unique pattern UP is selected as the cutout position from the captured image 2 [i] having a size larger than that of the unique pattern UP. , The method of adopting the image cut out from the template image 2 [i] is used. As a result, the template image 2 [i] can be acquired without increasing the formation accuracy of the unique pattern UP more than necessary. Therefore, the scale portion 2 can be easily formed and the formation cost can be reduced. In other words, even when the scale portion 2 having a low forming accuracy is used, the low forming accuracy can be made unquestioned when the template image 2 [i] is acquired.

FIG. 10 shows an example of the captured image 2 [0] captured when the rotation axis of the encoder 1 is at the calibration angle θ [0]. Among the plurality of marks 21 captured in the captured image 2 [0], the one close to the center of the image is selected, the unique pattern UP (second mark) is specified from the marks, and the area in which the unique pattern UP (second mark) is included without being chipped Is the cutout position. Then, the coordinates of the upper left end of the cutout position are obtained from the captured image 2 [0], and this is obtained as the reference coordinates 2 [0] (second [0] reference coordinates). Further, the image of the unique pattern UP included in the cutout position is cut out as the template image 2 [0] as shown in FIG.

Next, in step S117, the rotation axis of the encoder 1 is advanced by a predetermined angle. The predetermined angle is, for example, an angle corresponding to the arrangement interval of the marks 21, and the mark 21 captured near the center of the captured image 1 [i] at the calibration angle θ [i] and the mark 21 adjacent thereto. It is an angle corresponding to the elongation. As a result, the first image sensor 31a and the second image sensor 31b can capture the adjacent mark 21, that is, the mark 21 corresponding to the calibration angle θ [i2] described later in the field of view.

Next, in step S118, i + 1 is set as the variable i (the variable i is updated). Here, in order to distinguish between the variable i before the update and the variable i after the update, the variable i after the update is referred to as “i2”. In each flowchart, the variable i is used without distinguishing between before and after the update for convenience of illustration.

Immediately before this step S118, 0 was set as the variable i, so in this step S118, 1 is set as the variable i2. When step S118 is completed, the step flow returns to step S104.

Also in the second step S104, the storage unit 6 stores the calibration angle θ [i2] (the [i2] calibration angle). Here, since 1 is set as the variable i2, the calibration angle θ [1] is stored.

Also in the second step S105, the first image sensor 31a is made to image the mark 21. As a result, the captured image 1 [i2] (first [i2] reference image) is generated. Here, since 1 is set as the variable i2, the captured image 1 [1] is generated. Further, the second image sensor 31b is made to image the mark 21. As a result, the captured image 2 [i2] (second [i2] reference image) is generated. Here, since 1 is set as the variable i2, the captured image 2 [1] is generated. The generated captured image 1 [1] and captured image 2 [1] are temporarily stored in the storage unit 6.

Also in the second step S106, it is determined whether or not the variable i2 is larger than 0. If the variable i2 is larger than 0, the process proceeds to steps S107 to S109. In the example of this explanation, since the variable i2 is 1 at this point, steps S107 to S109 will be described below.

In step S107, the template image 1 [i2-1] is read out from the storage unit 6, and template matching is performed on the generated captured image 1 [i2]. Then, in the captured image 1 [i2], the unique pattern UP (first mark) that matches the template image 1 [i2-1] is captured. Therefore, the coordinates of the upper left end of the captured unique pattern UP are set to the matching coordinates 1 [. i2-1]. Here, since 1 is set as the variable i2, the template image 1 [0] is read out, and template matching is performed on the generated captured image 1 [1]. Then, as shown in FIG. 10, the matching coordinates 1 [0] are obtained. The obtained matching coordinates 1 [0] are temporarily stored in the storage unit 6.

In step S108, the template image 2 [i2-1] is read out from the storage unit 6, and template matching is performed on the generated captured image 2 [i2]. Then, in the captured image 2 [i2], the unique pattern UP (second mark) that matches the template image 2 [i2-1] is captured. Therefore, the coordinates of the upper left end of the captured unique pattern UP are set to the matching coordinates 2 [. i2-1]. Here, since 1 is set as the variable i2, the template image 2 [0] is read out, and template matching is performed on the generated captured image 2 [1]. Then, as shown in FIG. 10, the matching coordinates 2 [0] are obtained.

In steps S107 and S108, a process called sub-pixel estimation may be performed when performing template matching. According to the sub-pixel estimation, when the position of the unique pattern UP is estimated by template matching, the position can be estimated in units of one pixel or less. As a result, the matching coordinates 1 [i2-1] and the matching coordinates 2 [i2-1] can be obtained with higher accuracy.

In step S109, the difference between the obtained matching coordinates 1 [i2-1] and the reference coordinates 1 [i2-1] stored in the storage unit 6 is obtained. This difference is when the rotation axis of the encoder 1 rotates from the calibration angle θ [i2-1] (the [i2-1] calibration angle) to the calibration angle θ [i2] (the [i2] calibration angle). Corresponds to the amount of movement of the unique pattern UP in the captured image 1 [i2]. Then, the obtained difference is defined as the movement amount 1 [i2-1] (first [i2-1] reference movement amount). Here, since 1 is set as the variable i2, as shown in FIG. 10, the difference between the matching coordinate 1 [0] and the reference coordinate 1 [0] stored in the storage unit 6 is obtained. .. Then, the obtained difference is set to the movement amount 1 [0].

Similarly to this, the difference between the obtained matching coordinates 2 [i2-1] and the reference coordinates 2 [i2-1] stored in the storage unit 6 is obtained. This difference is when the rotation axis of the encoder 1 rotates from the calibration angle θ [i2-1] (the [i2-1] calibration angle) to the calibration angle θ [i2] (the [i2] calibration angle). Corresponds to the amount of movement of the unique pattern UP in the captured image 2 [i2]. Then, the obtained difference is defined as the movement amount 2 [i2-1] (second [i2-1] reference movement amount). Here, since 1 is set as the variable i2, as shown in FIG. 10, the difference between the matching coordinate 2 [0] and the reference coordinate 2 [0] stored in the storage unit 6 is obtained. .. Then, the obtained difference is set to the movement amount 2 [0].

Then, the calibration angle θ [i2-1] (the [i2-1] calibration angle), the calibration angle θ [i2] (the [i2] calibration angle), the movement amount 1 [i2-1] (the first [i2-]). 1] Reference movement amount) and movement amount 2 [i2-1] (second [i2-1] reference movement amount) are obtained, and stored in the storage unit 6. This correlation indicates the correlation between the rotation angle of the scale unit 2 and the distance in the captured image, and may be expressed in any form, but in step S2 described later, The rotation angle can be calculated back from the amount of movement.

Here, the captured image 1 [i2-1] used to calculate the movement amount 1 [i2-1] and the captured image 2 [i2-] used to calculate the movement amount 2 [i2-1]. 1] is an image generated at the timing when the rotation axes of the encoder 1 are at the same rotation angle (calibration angle θ [i2-1]). The timing at which the rotation axes of the encoder 1 are at the same rotation angle is the rotation angle when the captured image 1 [i2-1] is imaged and the rotation when the captured image 2 [i2-1] is imaged. It means that the moving angle is the same timing.

Similarly, the captured image 1 [i2] used to calculate the movement amount 1 [i2-1] and the captured image 2 [i2] used to calculate the movement amount 2 [i2-1] are also This is an image generated at the timing when the rotation axes of the encoder 1 are at the same rotation angle (calibration angle θ [i2]). Also in this case, as described above, the timing at which the rotation axes of the encoder 1 are at the same rotation angle is the rotation angle when the captured image 1 [i2] is imaged and the captured image 2 [i2]. This is the timing at which the rotation angle at the time of imaging is the same.

When the rotation axis of the encoder 1 is stopped, even if the time for capturing the captured image 1 [i2-1] and the time for capturing the captured image 2 [i2-1] are different. Similarly, the time at which the captured image 1 [i2] is captured and the time at which the captured image 2 [i2] is captured may be different, but these are preferably at the same time.

In addition, the first image sensor 31a that captures the captured image 1 [i2-1] and the captured image 1 [i2] and the second image sensor 31b that captures the captured image 2 [i2-1] and the captured image 2 [i2]. Are arranged at positions that are symmetrical (point symmetric) with respect to the first axis J1 which is the rotation axis, as described above.

By satisfying such conditions, the captured image 1 [i2-1] and the captured image 2 [i2-1], and the captured image 1 [i2] and the captured image 2 [i2] are each rotated by the encoder 1. Even if the moving axes are accompanied by axial runout, they include an axial translation component in which the translation directions are opposite to each other and the translation lengths are equal to each other. Therefore, it is obtained from the movement amount 1 [i2-1] obtained from the captured image 1 [i2-1] and the captured image 1 [i2], and from the captured image 2 [i2-1] and the captured image 2 [i2]. In the movement amount 2 [i2-1], the change in the axial translation component that occurs while the rotation axis of the encoder 1 changes from the calibration angle θ [i2-1] to the calibration angle θ [i2] is the translation direction. Are reflected while satisfying the relationship that they are opposite to each other and their translation lengths are equal to each other.

Therefore, by using the movement amount 1 [i2-1] and the movement amount 2 [i2-1] in obtaining the correlation in this step S109, the influence of the axial translation component can be reduced or offset. As a result, when the rotation angle is calculated back from the movement amount in step S2 described later, the influence of the shaft translation component is reduced or eliminated, in other words, only the shaft rotation component is extracted, and there is little error. The rotation angle can be calculated. That is, by obtaining in advance a correlation capable of reducing or eliminating the influence of such an axial translation component in this step S109, in step S2 described later, based on this correlation, the accuracy is higher in a shorter time. The rotation angle can be obtained. Along with this, it becomes easy to improve the resolution of the rotation angle to be detected.

As described above, in step S1 for obtaining the correlation described above, when the scale unit 2 is at the calibration angle θ [i2] (the [i2] calibration angle), the mark 21 including the first mark in the first image sensor 31a Image 1 [i2] (first [i2] reference image) is generated, and image 1 is captured by template matching based on template 1 [i2-1] (first [i2-1] template image). Obtain the movement amount 1 [i2-1] (first [i2-1] movement amount) from the reference coordinate 1 [i2-1] (first [i2-1] reference coordinate) of the first mark in [i2]. In step S107 and when the scale unit 2 is at the calibration angle θ [i2] (the [i2] calibration angle), the second image sensor 31b is made to image the mark 21 including the second mark, and the captured image 2 [i2] ( The second [i2] reference image) is generated, and the reference coordinates 2 of the second mark in the captured image 2 [i2] are obtained by template matching based on the template 2 [i2-1] (second [i2-1] template image). It includes step S108 for obtaining the movement amount 2 [i2-1] (second [i2-1] movement amount) from [i2-1] (second [i2-1] reference coordinates).

As an example, this correlation is the difference between the calibration angle θ [i2] (the [i2] calibration angle) and the calibration angle θ [i2-1] (the [i2-1] calibration angle), and the amount of movement 1. It is a correlation established between [i2-1] (first [i2-1] reference movement amount) and the sum of movement amount 2 [i2-1] (second [i2-1] reference movement amount). To. By including the sum of the movement amount 1 [i2-1] and the movement amount 2 [i2-1], it is possible to derive a correlation capable of reducing or canceling the axial translation component with a small amount of calculation. Therefore, by reflecting such a correlation, it is possible to reduce the calculation load when calculating the rotation angle and to increase the speed.

Further, as specific forms of the correlation, for example, the movement amount 1 [i2-1] (first [i2-1] reference movement amount) and the movement amount 2 [i2-1] (second [i2-1]). ] Reference movement amount), and the ratio of the difference between the calibration angle θ [i2] (the [i2] calibration angle) and the calibration angle θ [i2-1] (the [i2-1] calibration angle). The coefficient [i2-1] obtained as the above can be mentioned. As a form of correlation, for example, a list (calculation table) for obtaining the rotation angle from the movement amount based on the sum and difference described above can be considered, but in this case, when it takes time to calculate the rotation angle. There is also. On the other hand, by calculating such a coefficient [i2-1] and storing it in the storage unit 6, when the rotation angle is back-calculated from the movement amount in step S2 described later, the calculation speed is increased. be able to.

The coefficient [i2-1] is obtained by, for example, the following equation.

Since 1 is set as the variable i2 here, the coefficient [0] is obtained by the formula shown in FIG.

After the end of step S109, the process proceeds to step S110.
In step S110, as described above, it is determined whether or not the variable i2 is n or less. Here, since the variable i2 is 1, the process proceeds to step S111. After that, the step flow is advanced in the same manner as in steps S111 to S118 described above, and then the process returns to step S104. In step S118, i2 + 1 is set as the variable i2 (the variable i2 is updated). The updated variable i2 is referred to as "i3".

Subsequently, in the same manner, the third steps S104 to S106 and the second steps S107 to S109 can be performed to obtain the coefficient [i3-1].

After that, the coefficient [i4-1], the coefficient [i5-1], ..., The coefficient [i (n + 1) -1] can be obtained in the same manner. As a result, for all the marks 21, the correlation by the coefficient can be obtained and stored in the storage unit 6. Then, by using these correlations, it is possible to obtain a highly accurate rotation angle in step S2, which will be described later, regardless of the rotation angle of the rotation shaft of the encoder 1.

After that, the process proceeds to step S110 again. In step S110, as described above, it is determined whether or not the variable i (n + 2) is n or less. After obtaining the correlation for all the marks 21, since n + 1 is set as the variable i (n + 2), the step flow shown in FIG. 9 ends. At this time, since the calibration encoder is unnecessary, the calibration encoder is removed after the determination in step S110 (step S120).

As described above, it is possible to obtain a data set composed of the calibration angle, the template image, the reference coordinates, and the coefficients necessary for detecting the rotation angle in step S2 described later.

2.2.2. Detection of rotation angle In step S2 shown in FIG. 8, the rotation angle θ of the scale unit 2 is detected using the data set acquired in step S1.

Step S2 includes steps S201-S205, as shown in FIG. Hereinafter, each step will be described.

In step S2, first, in step S201, when the scale unit 2 is at an unknown rotation angle θ (measurement angle), the first image sensor 31a is made to image the mark 21. As a result, the angle measurement image 1 (first angle measurement image) is generated. The generated angle measurement image 1 is stored in the storage unit 6.

Next, in step S202, when the scale unit 2 is at the same rotation angle θ (measurement angle) as step S201, the second image sensor 31b is made to image the mark 21. As a result, the angle measurement image 2 (second angle measurement image) is generated. The generated angle measurement image 2 is stored in the storage unit 6.

As in step S1, the angle measurement image 1 and the angle measurement image 2 are images taken when the scale unit 2 is at the rotation angle θ (measurement angle) of the same rotation axis, and are preferably taken at the same time. It is said to be an image. Further, it is assumed that the rotation angle θ is between the calibration angle θ [i] and the calibration angle θ [i2].

In the next step S203, the angle measurement image 1 and the template image 1 [i] acquired in step S1 are read out from the storage unit 6, and template matching is performed on the angle measurement image 1. At the time of template matching, sub-pixel estimation is performed as necessary. By performing template matching, the unique pattern UP (first mark) that matches the template image 1 [i] is captured in the angle measurement image 1, so the coordinates of the upper left end of the captured unique pattern UP are matched in the angle measurement. Let the coordinates be 1. The obtained angle measurement matching coordinates 1 are stored in the storage unit 6.

In the next step S204, the angle measurement image 2 and the template image 2 [i] acquired in step S1 are read out from the storage unit 6, and template matching is performed on the angle measurement image 2. At the time of template matching, sub-pixel estimation is performed as necessary. By performing template matching, the unique pattern UP (second mark) that matches the template image 2 [i] is captured in the angle measurement image 2, so the coordinates of the upper left end of the captured unique pattern UP are matched by the angle measurement. Let the coordinates be 2. The obtained angle measurement matching coordinates 2 are stored in the storage unit 6.

In the next step S205, the angle-measurement matching coordinates 1 and the angle-measurement matching coordinates 2 are read out from the storage unit 6. Further, the reference coordinates 1 [i] corresponding to the template image 1 [i] and the reference coordinates 2 [i] corresponding to the template image 2 [i] acquired in step S1 are read out. Then, the movement amount 1 (first angle measurement movement amount) and the movement amount 2 (second angle measurement movement amount) are calculated based on the following calculation formulas.

Movement amount 1 = Angle matching coordinate 1-Reference coordinate 1 [i]
Movement amount 2 = Angle matching coordinates 2-Reference coordinates 2 [i]

The movement amount 1 and the movement amount 2 are the movement amounts of the unique patterns UP in the angle measurement image 1 and the angle measurement image 2 when the scale unit 2 rotates from the calibration angle θ [i] to the rotation angle θ. Corresponds to.

Here, in the angle measurement image 1 used to calculate the movement amount 1 and the angle measurement image 2 used to calculate the movement amount 2, the scale portions 2 have the same rotation angle with each other as described above. It is an image generated at the timing at θ (measurement angle). Therefore, the angle measurement image 1 and the angle measurement image 2 include an axial translation component in which the translation directions are opposite to each other and the translation lengths are equal to each other even if the scale portion 2 is accompanied by axial runout. It becomes. Therefore, by calculating the rotation angle θ by the procedure described later using the movement amount 1 and the movement amount 2, the influence of the axial translation component can be reduced or eliminated, and the rotation angle θ with less error can be calculated. it can. That is, it is possible to obtain a highly accurate rotation angle θ in a shorter time. Along with this, it becomes easy to improve the resolution of the rotation angle θ to be detected.

Subsequently, in step S205, the coefficient [i] is read from the storage unit 6. Then, the rotation angle θ is calculated by the following formula.
Rotation angle θ = Calibration angle θ [i] + (Movement amount 1 + Movement amount 2) × Coefficient [i]

As described above, the rotation angle θ can be calculated. The calculated rotation angle θ is output from the circuit unit 4, and is used, for example, in the control device of the robot 100 for driving control of the arm. In the present embodiment, an example is shown in which the angle measurement image generated in step S2 is stored in the storage unit 6 and then the angle measurement matching coordinates are acquired by using template matching, but the processing unit 5 has a plurality of processes. It is preferable to provide an apparatus and perform template matching processing by the processing unit 5 each time the angle measurement pixels are transferred from each image sensor to the processing unit 5, so that the generation of the angle measurement image and the acquisition of the angle measurement matching coordinates are processed in parallel. ..

As described above, the angle detection method according to the present embodiment is a method of detecting the rotation angle of the rotation shaft by using the encoder 1 having the scale unit 2, the first image sensor 31a, and the second image sensor 31b. Is. Of these, the scale portion 2 has a plurality of marks 21 including a first mark and a second mark arranged in an annular shape around the first axis J1 which is a rotation axis. Further, the first image sensor 31a is an element that images the first mark, and the second image sensor 31b is arranged at a position symmetrical to the first image sensor 31a with respect to the first axis J1 to form the second mark. It is an image sensor. The encoder 1 is configured such that the scale unit 2 rotates relative to the first image sensor 31a and the second image sensor 31b around the rotation axis.

Such an angle detection method includes a step S1 including the above-mentioned steps S101 to S118 and a step S2 including the above-mentioned steps S201 to S205.
Of these, in steps S104, S105, and S111 to S113, when the scale unit 2 is at the calibration angle θ [i] (the [i] calibration angle), the first image sensor 31a is made to image the first mark to capture an image. 1 [i] (first [i] reference image) is generated, and the reference coordinates 1 [i] of the first mark in the template image 1 [i] (first [i] template image) and the captured image 1 [i] are generated. This is a step of acquiring (first [i] reference coordinates).

In steps S104, S105, and S114 to S116, when the scale unit 2 is at the calibration angle θ [i] (the [i] calibration angle), the second image sensor 31b is made to image the second mark, and the captured image 2 [i] is captured. ] (Second [i] reference image), and the reference coordinates 2 [i] (second) of the second mark in the template image 2 [i] (second [i] template image) and the captured image 2 [i]. [I] This is a step of acquiring the reference coordinates).

Steps S104 to S109 and S118 change the calibration angle θ [i2-1] to the calibration angle θ [i2] as a correlation between the rotation angle of the scale unit 2 and the distance in the captured image. Amount (difference between calibration angle θ [i2] and calibration angle θ [i2-1]), movement amount of the first mark (movement amount 1 [i2-1]), movement amount of the second mark (movement amount) This is a step of finding the correlation that holds between 2 [i2-1]) and.

In steps S201, S203, and S205, when the scale unit 2 is at the rotation angle θ (measurement angle), the first image sensor 31a is made to image the first mark to generate the angle measurement image 1 (first angle measurement image). To do. Then, by template matching based on the template image 1 [i] (first [i] template image), the first mark in the angle measurement image 1 is derived from the reference coordinates 1 [i] (first [i] reference coordinates). This is a step of obtaining the first angular movement amount, which is the movement amount.

In steps S202, S204, and S205, when the scale unit 2 is at the rotation angle θ (measurement angle), the second image sensor 31b is made to image the second mark to generate the angle measurement image 2 (second angle measurement image). To do. Then, by template matching based on the template image 2 [i] (second [i] template image), the reference coordinates 2 [i] (second [i] reference coordinates) of the second mark in the angle measurement image 2 are obtained. This is a step of obtaining the second angular movement amount, which is the movement amount.

Then, in step S205, the rotation angle θ is obtained based on the calibration angle θ [i] (the [i] calibration angle), the first angle measurement movement amount, the second angle measurement movement amount, and the above-mentioned correlation. It's a step.

In such an angle detection method, the movement amount of the first mark and the movement amount of the second mark are calculated based on the images captured when the scale units 2 are at the same calibration angle, and these movement amounts and calibration are performed. The rotation angle θ is obtained by using the correlation with the change in the angle. Further, the first image sensor 31a and the second image sensor 31b used for capturing this image are arranged at positions symmetrical with respect to the first axis J1 which is the rotation axis. Therefore, the movement amount of the first mark and the movement amount of the second mark include an axial translation component in which the translation directions are opposite to each other and the translation lengths are equal to each other. Therefore, by deriving the correlation between these movement amounts and the calibration angle in advance, a highly accurate rotation angle θ that reduces or eliminates the influence of the axial translation component when measuring the rotation angle θ can be obtained. Can be sought.

Further, since this method is not a method of removing the angle error by using an eccentricity factor obtained in advance as in the conventional method, for example, even if a speed reducer in which dynamic eccentricity is generated is used as the speed reducer 112, the axial translation component It is possible to reduce or eliminate the influence of the above, and it is possible to obtain a highly accurate rotation angle θ. That is, since it is not a method of calculating using a predetermined eccentricity factor, the rotation angle θ can be accurately obtained even when a speed reducer whose eccentricity amount changes dynamically is used.

Further, in this method, when acquiring the template image 1 [i], a region including the unique pattern UP without being missing is selected as a cutout position from the captured image 1 [i] having a size larger than that of the unique pattern UP. The method of adopting the image cut out from the above as the template image 1 [i] is used. As a result, the template image 1 [i] can be acquired without increasing the formation accuracy of the unique pattern UP more than necessary. Therefore, the scale portion 2 can be easily formed and the formation cost can be reduced. In other words, even when the scale portion 2 having a low forming accuracy is used, the low forming accuracy can be made unquestioned when the template image 1 [i] is acquired. Similar effects can be obtained when the template image 2 [i] is acquired.

Further, the encoder unit 10 according to the present embodiment includes an encoder 1, a processing unit 5, and a storage unit 6. Of these, the encoder 1 has a scale unit 2, a first image sensor 31a, and a second image sensor 31b, and the scale unit 2 has a rotation axis with respect to the first image sensor 31a and the second image sensor 31b. It is configured to rotate relatively around. The scale portion 2 has a plurality of marks 21 including a first mark and a second mark arranged in an annular shape around the first axis J1 which is a rotation axis. The first image sensor 31a is an element that images the first mark, and the second image sensor 31b is arranged at a position symmetrical to the first image sensor 31a with respect to the first axis J1 to image the second mark. It is an element. The processing unit 5 executes a process of obtaining the rotation angle of the rotation axis of the encoder 1 based on the image pickup result of the first image pickup element 31a and the image pickup result of the second image pickup element 31b. The storage unit 6 stores an instruction that can be read by the processing unit 5.

In such an encoder unit 10, when the scale unit 2 is at the calibration angle θ [i] (the [i] calibration angle), the first image sensor 31a is made to image the first mark, and the captured image 1 [i] ( The first [i] reference image) is generated, and the reference coordinates 1 [i] (first [i]) of the first mark in the template image 1 [i] (first [i] template image) and the captured image 1 [i] are generated. ] Reference coordinates) is acquired.

Further, in the encoder unit 10, when the scale unit 2 is at the calibration angle θ [i] (the [i] calibration angle), the second image sensor 31b is made to image the second mark, and the captured image 2 [i] (third). 2 [i] reference image) is generated, and the reference coordinates 2 [i] (second [i]) of the second mark in the template image 2 [i] (second [i] template image) and the captured image 2 [i] are generated. Reference coordinates) are acquired.

Further, the encoder unit 10 changes the calibration angle θ [i2-1] to the calibration angle θ [i2] as a correlation between the rotation angle of the scale unit 2 and the distance in the captured image. (Difference between calibration angle θ [i2] and calibration angle θ [i2-1]), movement amount of the first mark (movement amount 1 [i2-1]), and movement amount of the second mark (movement amount 2). [I2-1]) and the correlation that holds between them are obtained.

Further, when the scale unit 2 is at the rotation angle θ (measurement angle), the encoder unit 10 causes the first image sensor 31a to image the first mark to generate the angle measurement image 1 (first angle measurement image). .. Then, by template matching based on the template image 1 [i] (first [i] template image), the first mark in the angle measurement image 1 is derived from the reference coordinates 1 [i] (first [i] reference coordinates). The first angular movement amount, which is the movement amount, is obtained.

Further, when the scale unit 2 is at the rotation angle θ (measurement angle), the encoder unit 10 causes the second image sensor 31b to image the second mark to generate the angle measurement image 2 (second angle measurement image). .. Then, by template matching based on the template image 2 [i] (second [i] template image), the reference coordinates 2 [i] (second [i] reference coordinates) of the second mark in the angle measurement image 2 are obtained. The second angular movement amount, which is the movement amount, is obtained.

Further, the encoder unit 10 obtains the rotation angle θ based on the calibration angle θ [i], the first angle measurement movement amount, the second angle measurement movement amount, and the above-mentioned correlation.

In such an encoder unit 10, the movement amount of the first mark and the movement amount of the second mark are calculated based on the images captured when the scale units 2 are at the same calibration angle, and these movement amounts and calibration are performed. The rotation angle θ is obtained by using the correlation with the change in the angle. Further, the first image sensor 31a and the second image sensor 31b used for capturing this image are arranged at positions symmetrical with respect to the first axis J1 which is the rotation axis. Therefore, the movement amount of the first mark and the movement amount of the second mark include an axial translation component in which the translation directions are opposite to each other and the translation lengths are equal to each other. Therefore, by deriving the correlation between these movement amounts and the calibration angle in advance, a highly accurate rotation angle θ that reduces or eliminates the influence of the axial translation component when measuring the rotation angle θ can be obtained. Can be sought.

Further, the robot 100 according to the present embodiment includes a base 110 which is a first member, a first arm 120 which is a second member which rotates with respect to the base 110, and an encoder unit 10. .. The scale unit 2 is provided on the first arm 120, and the first image sensor 31a and the second image sensor 31b are provided on the base 110.

According to such a robot 100, since the accuracy of the rotation angle of the first arm 120 detected by the encoder unit 10 is high, the first arm 120 can be controlled with high accuracy. As a result, it is possible to realize a highly reliable robot 100 capable of performing more accurate and delicate work.

3. 3. Second Embodiment Next, the angle detection method according to the second embodiment will be described.

FIG. 12 is a flowchart showing step S1 in detail in the angle detection method according to the second embodiment. FIG. 13 is a list showing the calibration angle, the template image, the reference coordinates, and the coefficients acquired by the angle detection method shown in FIG.

Hereinafter, the second embodiment will be described, but in the following description, the differences from the first embodiment will be mainly described, and the same matters will be omitted. Further, in FIGS. 12 and 13, the same reference numerals are given to the same configurations as those in the first embodiment.

The second embodiment is the same as the first embodiment except that the coefficient indicating the correlation between the calibration angle and the movement amount of the mark is different. Specifically, in the first embodiment described above, a coefficient is calculated for each calibration angle and used for calculating the rotation angle θ. On the other hand, in the second embodiment, the average coefficient is calculated at a plurality of calibration angles, and the average coefficient is used for calculating the rotation angle θ regardless of the vicinity of any calibration angle.

3.1. Acquisition of template image and the like The position detection method shown in FIG. 12 includes step S109A instead of step S109 shown in FIG.

In step S109A, as in step S109 according to the first embodiment, first, all the marks 21, that is, all of the calibration angles θ [i] from i = 0 to i = n, are respectively.
Movement amount 1 [i] = Match coordinates 1 [i] -Reference coordinates 1 [i]
Movement amount 2 [i] = Match coordinates 2 [i] -Reference coordinates 2 [i]
The movement amount 1 [i] and the movement amount 2 [i] defined in are calculated.

Then, the movement amount 1 [i] and the movement amount 2 [i] are added up to obtain the movement amount sum [i] by the following equation.
Total amount of movement [i] = amount of movement 1 [i] + amount of movement 2 [i]

Here, the step flow of the position detection method according to the present embodiment will be described with reference to FIG.

First, in step S103, the variable i is set to 0, and the cumulative movement amount sum is also reset to 0.

In the first step S109A, since the variable i is updated to the variable i2, the calibration angle θ [i2-1] (first position), the calibration angle θ [i2] (second position), and the movement amount The sum [i2-1] is obtained. Then, the cumulative movement amount sum is updated by the following formula.
Cumulative movement sum after update = Cumulative movement sum before update + movement sum [i2-1]

Here, since 1 is set as the variable i2 and the cumulative movement amount sum before the update is 0, the cumulative movement amount sum after the update is the movement amount sum [0].

In the second step S109A, since the variable i2 has been updated to the variable i3, the calibration angle θ [i3-1] (second position), the calibration angle θ [i3] (third position), and the amount of movement The sum [i3-1] is obtained. Then, the cumulative movement amount sum is updated by the following formula.
Cumulative movement sum after update = Cumulative movement sum before update + movement sum [i3-1]

Here, since 2 is set as the variable i3, the cumulative movement amount sum after the update is the movement amount sum [0] (cumulative movement amount sum before the update) + the movement amount sum [1].

Then, each time the variable is updated, the cumulative movement amount sum can be updated at any time by repeating step S109A as described above. Then, the average coefficient A, which will be described later, can be obtained from the finally obtained cumulative movement amount sum.

Specifically, in the first embodiment, the step flow is terminated after the final step S110, but in the present embodiment, step S119 is added after the final step S110.

In step S119, first, the total amount of change from the first calibration angle θ [0] to the last calibration angle θ [m + 1] when the template image is acquired is set to the calibration angle θ [m + 1] − calibration angle θ [0]. Obtained by. Then, the average coefficient A is calculated by the following formula.

In the above equation, m is an arbitrary integer of m ≦ n.
The average coefficient A thus obtained is a coefficient set for each calibration angle θ [i] in the first embodiment, and is common to all calibration angles θ [i] as shown in FIG. Can be replaced. As a result, it is not necessary to calculate individual coefficients for each calibration angle θ [i] and store them in the storage unit 6, and it is sufficient to store only one average coefficient A. As a result, it is possible to save labor in calculation and reduce the amount of use of the storage unit 6. At this time, since the calibration encoder is unnecessary, the calibration encoder is removed after step S119 (step S120).
The integer m when calculating the cumulative movement amount described above may be less than n.

3.2. Detection of Rotation Angle In the first embodiment described above, the rotation angle θ is calculated using the coefficient [i] peculiar to the calibration angle θ [i], the movement amount 1 and the movement amount 2. On the other hand, the reference image and the angle measurement image captured by the first image sensor 31a and the second image sensor 31b are used for the calculation of each coefficient [i], and the random noise inevitably generated in these images is used. It is included. Therefore, each coefficient [i] includes a measurement error due to random noise.

On the other hand, in the present embodiment, the average coefficient A is obtained from the cumulative amount of movement, and the rotation angle θ is calculated using this. Specifically, the rotation angle θ is calculated by the following formula.
Rotation angle θ = Calibration angle θ [i] + (angle measurement matching coordinates-reference coordinates [i]) × average coefficient A

Here, it is known that the above-mentioned random noise follows a normal distribution. Therefore, the process of calculating the average coefficient A, which is to obtain the cumulative movement amount in step S1, has the effect of converging the measurement error due to the random noise following the normal distribution to the average value of zero. Therefore, in the rotation angle θ calculated by the above formula, the occurrence of measurement error due to random noise is suppressed. Therefore, according to the present embodiment, the measurement error is smaller than that of the first embodiment, and the rotation angle θ can be detected with higher accuracy.
In the second embodiment as described above, the same effect as that of the first embodiment can be obtained.

4. Third Embodiment Next, the angle detection method according to the third embodiment will be described.

FIG. 14 is a flowchart showing step S1 in detail in the angle detection method according to the third embodiment. FIG. 15 is a list showing calibration angles, template images, reference coordinates, and coefficients acquired by the angle detection method shown in FIG.

Hereinafter, the third embodiment will be described, but in the following description, the differences from the first embodiment will be mainly described, and the same matters will be omitted. Further, in FIGS. 14 and 15, the same reference numerals are given to the same configurations as those in the first embodiment.

The third embodiment is the same as the first embodiment except that the coefficient indicating the correlation between the calibration angle and the movement amount of the mark is different. Specifically, in the first embodiment described above, the rotation angle θ is calculated using the coefficient [i2-1] including the sum of the movement amount 1 [i2-1] and the movement amount 2 [i2-1]. doing. On the other hand, in the third embodiment, the first coefficient is calculated from the movement amount 1 [i2-1], the second coefficient is calculated from the movement amount 2 [i2-1], and then the calculation angle θ1 is used. And the calculation angle θ2 is calculated, and then the rotation angle θ is calculated.

4.1. Acquisition of template image and the like The angle detection method shown in FIG. 14 includes steps S109C and S109D instead of step S109 of step S1 shown in FIG.

In step S109C, the calibration angle θ [i2-1] (the [i2-1] calibration angle), the calibration angle θ [i2] (the [i2] calibration angle), and the movement amount 1 [i2-1] (the first). The first correlation that holds between 1 [i2-1] reference movement amount) is obtained.

In step S109D, the calibration angle θ [i2-1] (the second i2-1 calibration angle), the calibration angle θ [i2] (the [i2] calibration angle), and the movement amount 2 [i2-1] (the second [i2-1]). The second correlation that holds between i2-1] reference movement amount) is obtained.

As described above, in the present embodiment, the correlation used when calculating the rotation angle θ in step S2 described later is the difference between the calibration angle θ [i2] and the calibration angle θ [i2-1], and The first correlation established between the movement amount 1 [i2-1], the difference between the calibration angle θ [i2] and the calibration angle θ [i2-1], and the movement amount 2 [i2-1]. Includes a second correlation that holds between them. The rotation angle θ can also be detected accurately by a method in which such a first correlation and a second correlation are obtained in advance and then reflected in the calculation of the rotation angle θ.

Further, as a specific form of the first correlation, the calibration angle θ [i2] and the calibration angle θ [i2-1] with respect to the movement amount 1 [i2-1] (the first [i2-1] reference movement amount). ] And the coefficient 1 [i2-1] (first coefficient) obtained as a ratio of the difference. Further, as a specific form of the second correlation, the calibration angle θ [i2] and the calibration angle θ [i2-1] with respect to the movement amount 2 [i2-1] (the second [i2-1] reference movement amount) ] And the coefficient 2 [i2-1] (second coefficient) obtained as a ratio of the difference. The rotation angle θ can also be obtained with high accuracy by a method in which such coefficients are obtained in advance and then reflected in the calculation of the rotation angle θ. Further, by calculating the coefficient in advance, the calculation load when calculating the rotation angle θ can be reduced and the speed can be increased. The obtained coefficient 1 [i2-1] and the coefficient 2 [i2-1] are stored in the storage unit 6.

For example, when 1 is set as the variable i2, the coefficient 1 [0] and the coefficient 2 [0] are obtained by the equations shown in FIG. 15, respectively.

4.2. Detection of Rotation Angle In step S2 according to the present embodiment, the first embodiment is performed except that the rotation angle θ is obtained by using the coefficient 1 [i] (first coefficient) and the coefficient 2 [i] (second coefficient). This is the same as step S2 according to the embodiment.

In step S205 according to the present embodiment, the coefficient 1 [i] and the coefficient 2 [i] are read out from the storage unit 6. Then, the calculation angle θ1 and the calculation angle θ2 are calculated by the following equations.

Calculation angle θ1 = Calibration angle θ [i] + Movement amount 1 x Coefficient 1 [i]
Calculation angle θ2 = Calibration angle θ [i] + Movement amount 2 x Coefficient 2 [i]

The calculated calculation angle θ1 and the calculation angle θ2 include an angle error due to the influence of the axial translation component included in the movement amount 1 and the movement amount 2, respectively. On the other hand, the influence of the axial translation components included in the movement amount 1 and the movement amount 2 is that the translation directions are opposite to each other and the translation lengths are equal to each other. Therefore, the angle errors included in the calculation angles θ1 and the calculation angles θ2 are also opposite to each other and have the same magnitude.

Therefore, the error due to the axis translation can be canceled by obtaining the sum of the calculation angle θ1 and the calculation angle θ2 by the following equation. Then, the rotation angle θ is calculated by calculating half of the sum.
Rotation angle θ = (calculation angle θ1 + calculation angle θ2) ÷ 2

As described above, the rotation angle θ can be calculated.
In addition, even in such a third embodiment, the same effect as that of the first embodiment can be obtained.

5. Fourth Embodiment Next, the angle detection method according to the fourth embodiment will be described.

FIG. 16 is a flowchart showing step S1 in detail in the angle detection method according to the fourth embodiment. FIG. 17 is a list showing calibration angles, template images, reference coordinates, and coefficients acquired by the angle detection method shown in FIG.

Hereinafter, the fourth embodiment will be described, but in the following description, the differences from the third embodiment will be mainly described, and the description of the same matters will be omitted. Further, in FIGS. 16 and 17, the same reference numerals are given to the same configurations as those in the third embodiment.

The fourth embodiment is the same as the third embodiment except that the coefficient indicating the correlation between the calibration angle and the movement amount of the mark is different. Specifically, in the third embodiment described above, the coefficient 1 [i] and the coefficient 2 [i] are calculated for each calibration angle and used for calculating the rotation angle θ. On the other hand, in the fourth embodiment, the first average coefficient and the second average coefficient are calculated at a plurality of calibration angles and used for calculating the rotation angle θ regardless of the calibration angle.

5.1. Acquisition of template image and the like The position detection method shown in FIG. 16 includes steps S109E and S109F instead of step S109 shown in FIG.

In steps S109E and S109F, as in step S109 according to the first embodiment, first, all the marks 21, that is, all of the calibration angles θ [i] from i = 0 to i = n, are respectively.
Movement amount 1 [i] = Match coordinates 1 [i] -Reference coordinates 1 [i]
Movement amount 2 [i] = Match coordinates 2 [i] -Reference coordinates 2 [i]
The movement amount 1 [i] and the movement amount 2 [i] defined in are calculated.

Then, the cumulative movement amount 1 [i] and the movement amount 2 [i] are added up to obtain the cumulative movement amount 1 and the cumulative movement amount 2 by the following equation.

In the above equation, m is an arbitrary integer of m ≦ n.
Here, the step flow of the position detection method according to the present embodiment will be described with reference to FIG.

First, in step S103, in addition to setting the variable i to 0, the cumulative movement amount 1 and the cumulative movement amount 2 are also reset to 0, respectively.

In the first steps S109E and S109F, since the variable i is updated to the variable i2, the calibration angle θ [i2-1] (first position), the calibration angle θ [i2] (second position), and the calibration angle θ [i2] (second position). The movement amount 1 [i2-1] (first [i2-1] reference movement amount) and the movement amount 2 [i2-1] (second [i2-1] reference movement amount) are obtained. Then, the cumulative movement amount 1 and the cumulative movement amount 2 are updated by the following equations.

Cumulative movement amount 1 after update = Cumulative movement amount 1 before update + movement amount 1 [i2-1]
Cumulative movement amount 2 after update = Cumulative movement amount 2 before update + movement amount 2 [i2-1]

Here, 1 is set as the variable i2, and the cumulative movement amount 1 before the update and the cumulative movement amount 2 before the update are set to 0, respectively. Therefore, the cumulative movement amount 1 after the update is the movement amount 1 [0]. The cumulative movement amount 2 after the update is the movement amount 2 [0].

In the second steps S109E and S109F, since the variable i2 has been updated to the variable i3, the calibration angle θ [i3-1] (second position), the calibration angle θ [i3] (third position), and the calibration angle θ [i3] (third position). The movement amount 1 [i3-1] (first [i3-1] reference movement amount) and the movement amount 2 [i3-1] (second [i3-1] reference movement amount) are obtained. Then, the cumulative movement amount 1 and the cumulative movement amount 2 are updated by the following equations.

Cumulative movement amount 1 after update = Cumulative movement amount 1 before update + movement amount 1 [i3-1]
Cumulative movement amount 2 after update = Cumulative movement amount 2 before update + movement amount 2 [i3-1]

Here, since 2 is set as the variable i3, the cumulative movement amount 1 after the update is the movement amount 1 [0] (cumulative movement amount 1 before the update) + the movement amount 1 [1], and is updated. The subsequent cumulative movement amount 2 becomes the movement amount 2 [0] (cumulative movement amount 2 before the update) + the movement amount 2 [1].

Then, by repeating the above steps S109E and S109F each time the variable is updated, the cumulative movement amount 1 and the cumulative movement amount 2 can be updated at any time. Then, the above-mentioned average coefficient 1 and average coefficient 2 can be obtained from the finally obtained cumulative movement amount 1 after renewal and cumulative movement amount 2 after renewal.

Specifically, in the third embodiment, the step flow is terminated after the final step S110, but in the present embodiment, step S119A is added after the final step S110.

In step S119A, first, the total amount of change from the first calibration angle θ [0] to the last calibration angle θ [m + 1] when acquiring the template image is calculated by the calibration angle θ [m + 1] − calibration angle θ [0]. Obtained by. Then, the average coefficient 1 and the average coefficient 2 are calculated by the following formulas.

The average coefficient 1 and the average coefficient 2 obtained in this way are all the first and second coefficients set for each calibration angle θ [i] in the third embodiment, as shown in FIG. It can be replaced with the average coefficient 1 and the average coefficient 2 in common with the calibration angle θ [i]. As a result, it is not necessary to calculate the individual first coefficient and the second coefficient for each calibration angle θ [i] and store them in the storage unit 6, and only the two average coefficients 1 and 2 are stored. It will be good to do it. As a result, it is possible to save labor in calculation and reduce the amount of use of the storage unit 6. At this time, since the calibration encoder is unnecessary, the calibration encoder is removed after step S119A (step S120).

The integer m may be less than n.

5.2. Detection of Rotation Angle Step S2 according to the present embodiment is the same as step S2 according to the third embodiment except that the rotation angle θ is obtained by using the average coefficient 1 and the average coefficient 2.

In step S2, the rotation angle θ is calculated using the above-mentioned average coefficient 1 and average coefficient 2. Specifically, the calculation angle θ1 and the calculation angle θ2 are first calculated by the following formulas.

Calculation angle θ1 = Calibration angle θ [i] + Movement amount 1 x Average coefficient 1
Calculation angle θ2 = Calibration angle θ [i] + Movement amount 2 x Average coefficient 2

The calculated calculation angle θ1 and the calculation angle θ2 include an angle error due to the influence of the axial translation component included in the movement amount 1 and the movement amount 2, respectively. On the other hand, the influence of the axial translation components included in the movement amount 1 and the movement amount 2 is that the translation directions are opposite to each other and the translation lengths are equal to each other. Therefore, the angle errors included in the calculation angles θ1 and the calculation angles θ2 are also opposite to each other and have the same magnitude.

Therefore, the error due to the axis translation can be canceled by obtaining the sum of the calculation angle θ1 and the calculation angle θ2 by the following equation. Then, the rotation angle θ is calculated by calculating half of the sum.
Rotation angle θ = (calculation angle θ1 + calculation angle θ2) ÷ 2

As described above, the rotation angle θ can be calculated.
Then, even in such a fourth embodiment, the same effect as that of the third embodiment can be obtained.

In the third embodiment described above, the rotation angle θ is calculated using the coefficients 1 [i] and the coefficients 2 [i] peculiar to the calibration angle θ [i], and the movement amount 1 and the movement amount 2. To do. On the other hand, the reference image and the angle measurement image captured by the first image sensor 31a and the second image sensor 31b are used for the calculation of each coefficient 1 [i] and each coefficient 2 [i]. , Contains inevitably generated random noise. Therefore, each coefficient 1 [i] and each coefficient 2 [i] include a measurement error due to random noise.

On the other hand, in the present embodiment, the measurement error caused by the random noise can be suppressed. Specifically, in the calculation process of the average coefficient 1 and the average coefficient 2 of obtaining the cumulative movement amount 1 and the cumulative movement amount 2 in step S1, the measurement error due to the random noise following the normal distribution is set to zero, which is the average value. It has the effect of converging on. Therefore, in the rotation angle θ calculated by the above formula, the occurrence of measurement error due to random noise is suppressed. Therefore, in the present embodiment, the measurement error is smaller than in the third embodiment, and the rotation angle θ can be detected with higher accuracy.

Although the angle detection method, the encoder unit, and the robot of the present invention have been described above based on the preferred embodiments shown in the drawings, the present invention is not limited thereto, and the configuration of each part is arbitrary having the same function. Can be replaced with the one of the configuration of. Moreover, other arbitrary components may be added. Further, the configurations of the two or more embodiments described above may be combined.

Further, the encoder unit of the present invention can be applied to both absolute type and incremental type.

Further, in the above-described embodiment, the case where the base of the robot is the “first member” and the first arm is the “second member” has been described as an example, but the present invention is not limited to this, and the robot rotates relatively. One of any two members can be referred to as a "first member" and the other can be referred to as a "second member". That is, the location where the encoder is installed is not limited to the joint between the base and the first arm, and may be the joint of any two arms that rotate relative to each other. Further, the installation location of the encoder is not limited to the joint portion of the robot.

Further, in the above-described embodiment, the number of robot arms is one, but the number of robot arms may be two or more. That is, the robot of the present invention may be a multi-arm robot such as a dual-arm robot, for example.

Further, in the above-described embodiment, the number of arms possessed by the robot arm is six, but the number of arms is not limited to this, and may be one, or two or more and five or less or seven. The above may be sufficient.

Further, the installation location of the robot is not limited to the floor surface, and may be, for example, a ceiling surface, a side wall surface, or a moving body such as an AGV (Automatic Guided Vehicle).

1 ... Encoder, 2 ... Scale unit, 3a ... 1st detection unit, 3b ... 2nd detection unit, 4 ... Circuit unit, 5 ... Processing unit, 6 ... Storage unit, 10 ... Encoder unit, 20 ... Dot, 21 ... Mark , 31a ... 1st imaging element, 31b ... 2nd imaging element, 32a ... 1st optical system, 32b ... 2nd optical system, 100 ... robot, 110 ... base, 111 ... motor, 112 ... reducer, 114 ... support Member, 115 ... Bearing, 120 ... First arm, 121 ... Arm body, 122 ... Shaft, 130 ... Second arm, 140 ... Work head, 141 ... Spline shaft, 150 ... End effector, 160 ... Wiring route, 1111 ... Rotation axis, DC ... Circumferential direction, DR ... Radial direction, J1 ... 1st axis, J2 ... 2nd axis, J3 ... 3rd axis, RI1 ... Imaging area, RI2 ... Imaging area, S1 ... Step, S101 ... Step, S102 ... Step, S103 ... Step, S104 ... Step, S105 ... Step, S106 ... Step, S107 ... Step, S108 ... Step, S109 ... Step, S109A ... Step, S109C ... Step, S109D ... Step, S109E ... Step, S109F ... step, S110 ... step, S111 ... step, S112 ... step, S113 ... step, S114 ... step, S115 ... step, S116 ... step, S117 ... step, S118 ... step, S119 ... step, S119A ... step, S120 ... Step, S2 ... Step, S201 ... Step, S202 ... Step, S203 ... Step, S204 ... Step, S205 ... Step, UP ... Unique pattern

Claims (7)

A scale unit having a plurality of marks including the first mark and the second mark arranged in an annular shape around the rotation axis, a first image sensor that images the first mark, and the first image pickup with respect to the rotation axis. It has a second image sensor that is arranged at a position symmetrical to the element and images the second mark, and the scale portion is around the rotation axis with respect to the first image sensor and the second image sensor. An angle detection method for detecting the rotation angle of the rotation shaft using a relatively rotating encoder.
When the scale unit is at the first [i] calibration angle, the first mark is imaged by the first image sensor to generate a first [i] reference image, and the first [i] template image and the first [I] A step of acquiring the first [i] reference coordinates of the first mark in the reference image, and
When the scale unit is at the [i] calibration angle, the second mark is imaged by the second image sensor to generate a second [i] reference image, and the second [i] template image and the first 2 [i] A step of acquiring the second [i] reference coordinates of the second mark in the reference image, and
[I] When the calibration angle is changed, the step of obtaining the correlation established between the amount of change, the amount of movement of the first mark, and the amount of movement of the second mark.
When the scale unit is at the measurement angle, the first mark is imaged by the first image sensor to generate a first angle measurement image, and the first is performed by template matching based on the first [i] template image. The step of obtaining the first angle-measurement movement amount from the first [i] reference coordinate of the first mark in the angle-measurement image, and
When the scale unit is at the measurement angle, the second mark is imaged by the second image sensor to generate a second angle measurement image, and template matching based on the second [i] template image is performed to obtain the second mark. 2. A step of obtaining the second angle movement amount of the second mark from the second [i] reference coordinate in the angle measurement image, and
The step of obtaining the measurement angle based on the first [i] calibration angle, the first angle movement amount, the second angle measurement movement amount, and the correlation.
An angle detection method characterized by having. The step of finding the correlation is
When the scale unit is at the first [i2] calibration angle, the first mark is imaged by the first image sensor to generate a first [i2] reference image, which is based on the first [i2-1] template image. A step of obtaining the first [i2-1] reference movement amount from the first [i2-1] reference coordinates of the first mark in the first [i2] reference image by template matching, and
When the scale unit is at the [i2] calibration angle, the second mark is imaged by the second image sensor to generate a second [i2] reference image, which is used as a second [i2-1] template image. A step of obtaining the second [i2-1] reference movement amount from the second [i2-1] reference coordinates of the second mark in the second [i2] reference image by template matching based on the above.
Including
The correlation includes the difference between the [i2] calibration angle and the [i2-1] calibration angle, and the first [i2-1] reference movement amount and the second [i2-1] reference movement amount. The angle detection method according to claim 1, which is a relationship that holds between the sum and the sum. The angle detection method according to claim 2, wherein the correlation is a coefficient obtained as a ratio of the difference to the sum. The step of finding the correlation is
When the scale unit is at the first [i2] calibration angle, the first mark is imaged by the first image sensor to generate a first [i2] reference image, which is based on the first [i2-1] template image. A step of obtaining the first [i2-1] reference movement amount from the first [i2-1] reference coordinates of the first mark in the first [i2] reference image by template matching, and
When the scale unit is at the [i2] calibration angle, the second mark is imaged by the second image sensor to generate a second [i2] reference image, which is used as a second [i2-1] template image. A step of obtaining the second [i2-1] reference movement amount from the second [i2-1] reference coordinates of the second mark in the second [i2] reference image by template matching based on the above.
Including
The correlation is
The first correlation established between the difference between the first [i2] calibration angle and the first [i2-1] calibration angle and the first [i2-1] reference movement amount,
The second correlation established between the difference between the second [i2] calibration angle and the [i2-1] calibration angle and the second [i2-1] reference movement amount,
The angle detection method according to claim 1. The first correlation is a first coefficient obtained as a ratio of the difference to the first [i2-1] reference movement amount.
The angle detection method according to claim 4, wherein the second correlation is a second coefficient obtained as a ratio of the difference to the second [i2-1] reference movement amount. A scale unit having a plurality of marks including the first mark and the second mark arranged in an annular shape around the rotation axis, a first image sensor that images the first mark, and the first image pickup with respect to the rotation axis. It has a second image sensor that is arranged symmetrically with the element and images the second mark, and the scale unit is around the rotation axis with respect to the first image sensor and the second image sensor. With a relatively rotating encoder,
A processing unit that executes a process of obtaining the rotation angle of the rotation axis of the encoder based on the image pickup result of the first image pickup element and the image pickup result of the second image pickup element.
A storage unit that stores instructions that can be read by the processing unit,
Have,
The processing unit is based on the instruction stored in the storage unit.
When the scale unit is at the first [i] calibration angle, the first image sensor is made to image the first mark to generate a first [i] reference image, and the first [i] template image and the first [I] Acquire the first [i] reference coordinates of the first mark in the reference image, and obtain the first [i] reference coordinates.
When the scale unit is at the [i] calibration angle, the second image sensor is made to image the second mark to generate a second [i] reference image, and the second [i] template image and the first 2 [i] Acquire the second [i] reference coordinates of the second mark in the reference image, and obtain the second [i] reference coordinates.
When the first [i] calibration angle is changed, the correlation established between the amount of change, the amount of movement of the first mark, and the amount of movement of the second mark is obtained.
When the scale unit is at the measurement angle, the first image sensor is made to image the first mark to generate a first angle measurement image, and the first is performed by template matching based on the first [i] template image. The amount of movement of the first angle measurement from the first [i] reference coordinate of the first mark in the angle measurement image is obtained.
When the scale unit is at the measurement angle, the second image sensor is made to image the second mark to generate a second angle measurement image, and template matching based on the second [i] template image is performed to obtain the second mark. The second angle movement amount of the second mark from the second [i] reference coordinate in the two angle measurement image is obtained.
[I] An encoder unit characterized by executing a process of obtaining the measurement angle based on the calibration angle, the first angle measurement movement amount, the second angle measurement movement amount, and the correlation. The first member and
A second member that rotates with respect to the first member,
The encoder unit according to claim 6 and
With
A robot characterized in that the scale portion is provided on the second member, and the first image pickup element and the second image pickup element are provided on the first member.

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