Angle calibration method

Abstract

The robot has an actuator that changes the angle of a second member relative to a first member in accordance with a command value. In a first process of the angle calibration method, a distance between two measurement target portions, one of which is disposed on the first member and the other of which is disposed on the second member, is measured while an arbitrary command value is given to the actuator, and a measurement target portion distance is obtained. In a second process, an angle difference corresponding to the difference between the two measurement target portion distances is calculated based on a reference measurement target portion distance obtained by measuring the measurement target portion distance while an arbitrary command value is given to the actuator in the past and the measurement target portion distance obtained in the first process.

Description

Technical Field

[0001] This invention relates to a method for calibrating the angle of a robot. Background Technology

[0002] In the prior art, robots with one or more joints are known. In such robots, actuators for rotating arms and hands are configured in each joint. Electric motors are typically used as actuators.

[0003] Each actuator rotates the output shaft to achieve an angle corresponding to the input command value. In many cases, the actuators are configured during assembly to make the predetermined angle of the robot at the origin posture 0°.

[0004] To improve the positional accuracy of the robot's tip, this origin calibration (angle calibration) often requires the use of high-end equipment such as laser trackers.

[0005] Patent document 1 discloses a method that uses position measuring equipment such as laser trackers to detect the deviation of the setting position and setting posture of the working robot during the exchange, and corrects the teaching data only for the part of the deviation.

[0006] The robot disclosed in Patent Document 1 may experience problems after shipment from the factory, requiring only the replacement of the electric motor. While the laser tracker disclosed in Patent Document 1 can be used when replacing the entire robot, it is difficult to use such an expensive device when only a part is being replaced.

[0007] [Patent Documents]

[0008] [Patent Document 1]: Japanese Patent Application Publication No. 2016-78173 Summary of the Invention

[0009] In view of the above, the object of the present invention is to obtain with high precision the offset of the rotation angle in a robot caused by the exchange of actuators, etc., through a simple and short operation.

[0010] The technical problem to be solved by the present invention is as described above. The technical solution to solve the technical problem and its effects are described below.

[0011] Based on the present invention, the following angle calibration method is provided. That is, this angle calibration method is applicable to a robot comprising a first component, a second component, and an actuator. The second component is rotatably connected to the first component. The actuator, in response to a command value, causes the angle of the second component relative to the first component to change. The angle calibration method includes a first step and a second step. In the first step, under a state where the actuator is given an arbitrary command value, the distance between the walls of two measurement object parts is measured to obtain a distance between the two measurement object parts, wherein the two measurement object parts are two measurement object parts, one disposed in the first component and the other disposed in the second component. In the second step, based on a reference measurement object part distance obtained by measuring the measurement object part distance under a state where the actuator is given an arbitrary command value, and the measurement object part distance obtained in the first step, an angle difference corresponding to the difference between the two measurement object part distances is calculated.

[0012] Therefore, by adjusting the command value given to the current actuator based on the obtained angle difference, the rotation angle of the second component based on the initial actuator can be reproduced with good accuracy. Calibration can be performed simply by measuring the distance between the walls of the object being measured, without requiring the robot to move bit by bit, thus improving work efficiency.

[0013] [The effects of the invention]

[0014] Based on this invention, the displacement of rotation angle in a robot caused by actuator switching can be obtained with high precision through a simple and short operation. Attached Figure Description

[0015] Figure 1 This is a perspective view of an industrial robot representing one embodiment of the present invention.

[0016] Figure 2 This is a perspective view showing the installation of pins at the joint of the second joint body and the joint of the second arm.

[0017] Figure 3 It is a cross-sectional view showing the structure of the pin and mounting hole in detail.

[0018] Figure 4 It is a three-dimensional diagram showing the two pins that are being installed.

[0019] Figure 5 It is a three-dimensional diagram showing the use of vernier calipers to measure distances by holding two pins in place.

[0020] Figure 6 This is a schematic diagram used to illustrate the relationship between pin spacing and angle difference. Detailed Implementation

[0021] The embodiments of the present invention will now be described with reference to the accompanying drawings. Figure 1 This is a perspective view of an industrial robot 6 according to one embodiment of the present invention.

[0022] Figure 1 The industrial robot (robot) 6 shown is configured as a vertical, multi-jointed robot with six degrees of freedom of motion. This industrial robot 6 includes an arm 7 and a controller 8. The arm 7 can move according to the instructions of the controller 8 to perform a prescribed task.

[0023] The arm 7 includes a base 10, a first joint body 11, a first arm 21, a second joint body (first component) 12, a second arm (second component) 22, a third joint body 13, and a tip 23.

[0024] The base 10 is a component that functions as the base of the arm 7 and is fixed to the floor or the like.

[0025] The first joint body 11 is disposed on the upper side of the base 10. The first joint body 11 is rotatably supported on the base 10 with the vertical axis (rotation axis c1) as the center.

[0026] The first arm 21 is configured as an elongated component. One end of the first arm 21 along its length is rotatably supported on the first joint body 11. The axis of rotation c2 of the first arm 21 relative to the first joint body 11 is located in a plane perpendicular to the axis of rotation of the first joint body 11.

[0027] The second joint body 12 is configured as a block-shaped component. The second joint body 12 is rotatably supported at the tip of the first arm 21. The rotation axis c3 of the second joint body 12 relative to the first arm 21 is configured to be parallel to the rotation axis c2 of the first arm 21 relative to the first joint body 11.

[0028] The second arm 22 is configured as an elongated component. The second arm 22 is supported on the second joint body 12. The second arm 22 is rotatable about an axis (rotation axis c4) extending along the length direction of the second arm 22.

[0029] The third joint body 13 is rotatably supported at the tip of the second arm 22. The axis of rotation c5 of the third joint body 13 relative to the second arm 22 is located in a plane perpendicular to the axis of rotation of the second arm 22 relative to the second joint body 12.

[0030] The tip end 23 is rotatably supported on the third joint body 13. The rotation axis c6 of the tip end 23 relative to the third joint body 13 is located in a plane perpendicular to the rotation axis c5 of the third joint body 13 relative to the second arm 22.

[0031] The controller 8 is located near the base 10. The controller 8 enables the arm 7 to move appropriately by sending electrical signals to the electric motors (actuators) of the aforementioned rotating shafts fixed on the arm 7.

[0032] Although not shown in the figure, the electric motor controlled by the controller 8 includes an electric motor that rotates the second arm 22 relative to the second joint body 12.

[0033] For an industrial robot 6 with the above-described structure, when it is placed on a construction site or similar location, an operation called origin calibration must be performed. Origin calibration is sometimes also referred to as zeroing. In this origin calibration, angle calibration is performed on each electric motor to ensure that the predetermined angle of the robot in the origin posture is 0°.

[0034] This origin calibration can be performed, for example, using the laser tracker shown in Patent Document 1. Since the method of origin calibration is well-known, its description is omitted. Through this origin calibration, an angle of 0° is given as a command value to each electric motor, thereby enabling the industrial robot 6 to achieve the aforementioned origin posture with good accuracy.

[0035] After the industrial robot 6 begins operation, the various electric motors (e.g., the electric motor used to rotate the second arm 22 relative to the second joint body 12) may malfunction in the future. Considering this, in this embodiment, for example, at the moment immediately after the origin calibration is completed, such as... Figure 2 As shown, install two pins 51 on the arm part 7, and as... Figure 5 As shown, the distance between the two pins 51 is measured in advance.

[0036] Each pin 51 serves to mark a predetermined position on the second joint body 12 and the second arm 22. The marking can also be referred to as the measurement target section. Simultaneously, the two pins 51 are used to utilize... Figure 5 The vernier caliper 71 shown accurately measures the distance between the markings and also functions as a detachable clamp. This measurement result can be used for re-alignment (angle calibration) in subsequent situations, such as when replacing a faulty electric motor.

[0037] Specifically, a connecting portion 31 for detachably mounting the pin 51 is provided on the second joint body 12. The connecting portion 31 is integrally formed in the portion of the second joint body 12 near the second arm 22 and protrudes in a direction away from the rotation axis c4. In other words, the direction in which the connecting portion 31 protrudes from the second joint body 12 is radially out of a circle centered on the rotation axis c4.

[0038] The rotation axis c4 is the central axis of rotation of the second arm 22 relative to the second joint body 12. Therefore, it can also be said that the rotation axis c4 is the joint axis of the joint connecting the second joint body 12 and the second arm 22.

[0039] A mounting cavity 32 for mounting the pin 51 is formed on the joint 31. The mounting cavity 32 is formed as an elongated threaded hole. The axis of the mounting cavity 32 is parallel to the rotation axis c4. The mounting cavity 32 opens on the side of the joint 31 near the second arm 22.

[0040] A connecting portion 41 for detachably mounting the pin 51 is provided on the second arm 22. The connecting portion 41 is integrally formed on the portion of the second arm 22 near the second joint body 12 and protrudes in a direction away from the rotation axis c4. Alternatively, the direction in which the connecting portion 41 protrudes from the second arm 22 is radially out of a circle centered on the rotation axis c4.

[0041] A mounting cavity 42 for mounting the pin 51 is formed on the joint 41. The mounting cavity 42 is formed as an elongated threaded hole. The axial direction of the mounting cavity 42 is parallel to the rotation axis c4. The mounting cavity 42 opens on the surface of the joint 41 near the second joint body 12.

[0042] like Figure 3 As shown, the two mounting holes (32, 42) are identical in shape. Correspondingly, the two pins 51 are also identical in shape. This reduces processing costs and component costs.

[0043] Each pin 51 is a long, thin rod-shaped component. Each pin 51 has a cylindrical portion 55, a tapered portion 56, and an externally threaded portion 57. The cylindrical portion 55, the tapered portion 56, and the externally threaded portion 57 are integrally formed.

[0044] The cylindrical portion 55 is a cylindrical part with a diameter of a specified size, machined with high precision. To allow the pin 51 to be mounted on the second joint body 12 or the second arm 22 in a direction parallel to the rotation axis c4, the cross-sectional profile of the cylindrical portion 55 is circular along a plane perpendicular to the rotation axis c4. The cylindrical portion 55 is located at the end of the pin 51 in the longitudinal direction. At the end of this cylindrical portion 55, a hexagonal cavity is formed for inserting a tool used to tighten the pin 51.

[0045] The tapered portion 56 is a brim-shaped part connected to the cylindrical portion 55. The diameter of the tapered portion 56 is larger than the diameter of the cylindrical portion 55. The tapered portion 56 is configured as a truncated cone shape, with the side closer to the cylindrical portion 55 having a larger diameter and the side farther from the cylindrical portion 55 having a smaller diameter. The axis of this cone is precisely aligned with the axis of the cylinder of the cylindrical portion 55.

[0046] The external thread portion 57 is the part that is machined into an external thread. The external thread portion 57 is disposed at the end of the pin 51 on the side opposite to the cylindrical portion 55 in the longitudinal direction. The external thread portion 57 is connected to the tapered portion 56.

[0047] In the mounting cavity 32 disposed in the second joint body 12, a conical recess 36, a peripheral recess 37, and an internal thread 38 are formed.

[0048] The inner diameter of the tapered recess 36 is larger than the inner diameter of the internal thread portion 38. The tapered recess 36 is configured as a truncated cone shape, with the larger diameter on the side closer to the opening of the mounting cavity 32 and the smaller diameter on the side farther from the opening. The shape of this tapered recess 36 corresponds to the shape of the tapered portion 56 of the pin 51. The axis of the tapered recess 36 is configured to be parallel to the rotation axis c4. The axis of the tapered recess 36 is located at a precise distance from the rotation axis c4.

[0049] The peripheral recess 37 is formed as a large circle with a suitable depth around the opening of the conical recess 36. Even when the conical portion 56 of the pin 51 does not entirely enter the conical recess 36 of the mounting cavity 32, the un-entered portion can enter the peripheral recess 37. As a result, it is possible to make substantially only the cylindrical portion 55 protrude from the joint 31, thus facilitating measurement with the vernier caliper 71 described later.

[0050] The internal thread portion 38 is a portion with internal threads. The internal thread portion 38 is configured to be adjacent to the side of the tapered recess 36 that is furthest from the opening of the mounting cavity 32. The external thread portion 57 of the pin 51 can be screwed onto the internal thread portion 38.

[0051] The mounting hole 42 on the second arm 22 is the same as the mounting hole 32 on the second joint body 12, and has a conical recess 46, a peripheral recess 47, and an internal thread 48. The structure of the conical recess 46, the peripheral recess 47, and the internal thread 48 is the same as that of the conical recess 36, the peripheral recess 37, and the internal thread 38 of the mounting hole 32.

[0052] The axis of the tapered recess 46 is configured to be parallel to the rotation axis c4. The axis of the tapered recess 46 is located at a position precisely away from the rotation axis c4 by a specified distance. The distance between the axis of the tapered recess (36, 46) of each of the two mounting holes (32, 42) and the rotation axis c4 is equal.

[0053] In the above structure, a pin 51 is installed in the mounting cavity 32 of the joint 31, and a pin 51 is installed in the mounting cavity 42 of the joint 41. By rotating the pin 51, it can be screwed and fixed in the mounting cavity (32, 42). Therefore, the installation / removal of the pin 51 is relatively easy.

[0054] By tightening the thread of pin 51, tapered portion 56 can achieve a centering effect. Thus, the axis of pin 51 is perfectly aligned with the axis of the tapered recess (36, 46) of each mounting hole (32, 42).

[0055] Since the two mounting holes (32, 42) are parallel to each other, the two mounting pins 51 are also parallel to each other. Since the openings of the two mounting holes (32, 42) are 180° apart, the directions in which the two pins 51 protrude from the joints (31, 41) are also... Figure 3 and Figure 4 As shown, they differ by 180°. Since the two pins 51 are identical components, the outer diameters of the cylindrical portions 55 are also equal.

[0056] The centers of the two pins 51 are each equidistant from the rotation axis c4. In other words, the centers of the two pins 51 lie on the same virtual circle centered on the rotation axis c4. As the angle of the second arm 22 relative to the second joint body 12 changes, the pins 51 on the side of the second arm 22 move along the virtual circle. As a result, the central angles of the two pins 51 change.

[0057] At an appropriate time after the assembly of industrial robot 6 is completed and the above-mentioned origin calibration has been performed, such as Figure 5 As shown, the distance between the outer periphery walls of the cylindrical portion 55 is measured using a vernier caliper 71 clamping the two pins 51. At this point, a predetermined command value (e.g., 0°) is given to the electric motor driving the second arm 22. This command value can be any value, but it is preferable to set it so that the two pins 51 are neither too close nor too far apart.

[0058] The outer diameter of the cylindrical portion 55 is known. Therefore, the distance between the centers of the two cylindrical portions 55 can be obtained by subtracting the radii of the two cylindrical portions 55 from the distance between the wall surfaces measured with vernier calipers 71. In this embodiment, the distance between the centers is defined as the marking distance (distance between the measured object portions). However, the distance between the wall surfaces can also be used as the marking distance instead of the distance between the centers of the pins 51. In this embodiment, the obtained pin center distance is recorded as the reference pin center distance (reference marking distance, reference distance between the measured object portions) in a suitable location for future reference. After the above measurement, the two pins 51 are removed, and the industrial robot 6 can begin operation.

[0059] Subsequently, consider the scenario where the electric motor used to rotate the second arm 22 relative to the second joint body 12 malfunctions and is replaced with a new electric motor. In this case, after the replacement is completed, the pin 51 is reinstalled on the second joint body 12 and the second arm 22, as follows. Figure 5 As shown, the distance between the outer periphery walls of the two pins 51 is measured using vernier calipers 71. Subtracting the radii of the two cylindrical portions 55 from this distance yields the center-to-center distance (marking distance) of the pins 51 (first step). At this point, the state is such that a specified command value is given to the electric motor after the exchange. This command value can be any value, but for the sake of simplicity in subsequent calculations, it is preferable that this command value is the same as the command value (0°) given to the electric motor before the exchange when initially measured with vernier calipers 71.

[0060] Below, based on the measurement results obtained using vernier caliper 71, a brief explanation will be given of the method for obtaining the central angle corresponding to the two pins 51.

[0061] like Figure 6 As shown, the distance R between the rotation axis c4 of the second arm 22 and the centers of the two pins 51 is equal. Therefore, the triangle formed by the rotation axis c4 and the centers of the two pins 51 is an equilateral triangle. The vertex angle θ of this equilateral triangle represents the angle relative to the centers of the two pins 51.

[0062] The distance L between the centers of the pins 51, as described above, can be obtained from the measurement results obtained using vernier calipers 71.

[0063] In general, in triangle ABC, if a = BC, b = CA, c = AB, and α = ∠CAB, then cosα = (b 2 +c 2 -a 2 The relationship ) / (2bc) holds. This is well-known as the Law of Cosines. Furthermore, substituting a=L, b=c=R, and α=θ, we get cosθ=(1-(L / 2bc) / (2bc)). 2 / 2R 2 Therefore, θ can be obtained through θ = arccos(1 - (L)). 2 / 2R 2 )) to obtain.

[0064] The re-origin calibration will be explained below.

[0065] Consider the scenario where θ differs even when the same command value is given to the electric motor before and after the swap. The angle difference Δθ between the electric motor before and after the swap can be obtained by calculating the angle θ for both the original and new L values ​​(second step). Next, the offset of the command value used to compensate for this angle difference Δθ is calculated (third step). By offsetting the command value given to the swapped electric motor by the calculated value, the angle deviation of the electric motor before and after the swap can be eliminated. This allows for re-alignment at the origin.

[0066] Different command values ​​can also be given to the electric motor before and after the exchange. In this case, when calculating the aforementioned angle difference Δθ, the angle corresponding to the offset of the command value needs to be considered.

[0067] However, in addition to the methods described in this embodiment, several other methods can be considered for re-origin calibration.

[0068] The first method uses a dial gauge. In this method, after the initial origin calibration, the dial is immediately fixed at a predetermined position on the arm 7. In this state, appropriate command values ​​are given to each of the robot's electric motors, causing the dial to align with the appropriate frame. The value displayed on the dial is then recorded. During the re-origin calibration, the dial is similarly fixed at the robot's predetermined position, aligning with the frame. In this state, the robot is moved little by little, and the command offset value is calculated based on the command value displayed on the dial when it matches the initial value.

[0069] This method requires fixing the dial to the robot, which can easily make the operation cumbersome. In addition, when moving the robot little by little, due to factors such as motion decomposition energy, it is sometimes difficult to make the dial value exactly match the initial value.

[0070] The second method uses an inclinometer. In this method, during the manufacturing of the industrial robot 6, suitable surfaces of the arm 7 are pre-machined with high precision. After the initial origin calibration, an inclinometer is immediately set up on this surface using a suitable fixture, and the value displayed by the inclinometer is recorded. The same inclinometer is set up during the re-origin calibration. The command offset value is calculated based on the value displayed by the inclinometer.

[0071] This method requires the formation of a high-precision machined surface on the arm section 7, incurring processing costs. Furthermore, since the origin calibration is performed based on the mounting surface of the inclinometer, the accuracy of the origin calibration is not necessarily high.

[0072] The third method utilizes pin contact. In this method, pins are installed on the two relatively moving frames (e.g., the second joint 12 and the second arm 22). However, unlike the pin 51 described above, the pins are installed such that they directly contact each other when the two frames form a predetermined angle. After the initial origin calibration, the robot is immediately moved little by little until the pins contact each other, and the command value at the point of contact is recorded. In the re-origin calibration, the pins are installed in the same manner as in the initial origin calibration, and the robot is moved little by little. The command offset value is calculated based on the command value at the point of pin contact.

[0073] In this method, determining the contact between the pins is difficult. For example, a thin sheet can be sandwiched between the pins, and contact can be determined based on whether the sheet moves, but this process is cumbersome. Furthermore, excessive robot movement can deform the pins, significantly reducing the accuracy of the origin calibration, thus requiring precise operation. Additionally, since origin calibration is based on the pinhole where the pin is installed, the accuracy of the re-origin calibration is not necessarily high. In the case of insert-type pins, the gap used to insert the pinhole is related to the low accuracy of the re-origin calibration.

[0074] In this respect, the method of this embodiment allows for the high-precision installation of easily manufactured pins 51 using the tapered portion 56. Furthermore, since the operation does not require the robot to move little by little, re-origin calibration can be completed in a shorter time, thereby enabling early robot recovery. Moreover, because the re-origin calibration is based on the measurement data from the initial origin calibration, high-precision re-origin calibration can be performed.

[0075] As described above, the industrial robot 6 of this embodiment includes a second joint body 12, a second arm 22, and an electric motor. The second arm 22 is rotatably connected to the second joint body 12. The electric motor changes the angle of the second arm 22 relative to the second joint body 12 according to a command value. The re-angle calibration method performed in this embodiment includes a first step and a second step. In the first step, with an arbitrary command value given to the electric motor, the distance between the walls of the pins 51 can be obtained to determine the distance (pin center distance) between two pins 51 (markers), that is, the distance between two pins 51, one disposed on the second joint body 12 and the other disposed on the second arm 22. In the second step, based on the reference pin center distance obtained by measuring the pin center distance with an arbitrary command value given to the electric motor during the initial origin calibration, and the pin center distance obtained in the first step, the angle difference Δθ corresponding to the difference between the two pin center distances is calculated.

[0076] Therefore, by adjusting the command value given to the swapped electric motor based on the obtained angle difference Δθ, the rotation angle of the second arm 22 based on the electric motor before the swap can be reproduced with good accuracy. Since the industrial robot 6 does not need to move little by little, and only the distance between the walls of the pins 51 needs to be measured for re-origin calibration, the work efficiency can be improved.

[0077] In addition, in this embodiment, one of the two markings is a pin 51 protruding from the second joint body 12, and the other is a pin 51 protruding from the second arm 22.

[0078] This enables the implementation of a simple structure for re-origin calibration.

[0079] In addition, in this embodiment, the two pins 51 protrude in opposite directions.

[0080] This allows for both a shorter length for each pin 51 and easy measurement of the distance between the walls of the pins 51.

[0081] In addition, in this embodiment, the two pins 51 are respectively detachable from the second joint body 12 or the second arm 22.

[0082] Therefore, pin 51 can be removed to avoid obstructing the operation of industrial robot 6.

[0083] In this embodiment, the two pins 51 are respectively installed in the mounting holes 32 and 42 formed on the second joint body 12 or the second arm 22. The mounting holes 32 and 42 are screw holes.

[0084] Thus, the pin 51 can be fixed to the second joint body 12 or the second arm 22 by a simple operation such as turning the pin 51.

[0085] In addition, in this embodiment, each of the two pins 51 has a tapered portion 56. On the second joint body 12 or the second arm 22, tapered recesses 36 and 46 corresponding to the tapered portions 56 of the pins 51 are formed.

[0086] Therefore, by using the tapered portion 56 for centering, the center of the pin 51 can be precisely aligned with the centers of the tapered recesses 36 and 46. As a result, the accuracy of re-origin calibration can be improved.

[0087] Furthermore, in this embodiment, the cross-sectional profiles of the cylindrical portions 55 of the two pins 51, when cross-sectioned along a plane perpendicular to the axis, are both circular. The diameters of the circles of the cross-sectional profiles of the two pins 51 (in other words, the outer diameters of the cylindrical portions 55) are equal. The distances between the cylindrical portions 55 of the two pins 51 and the rotation axis c4 are equal.

[0088] Therefore, it is easy to calculate the angle θ corresponding to the two pins 51.

[0089] In addition, in this embodiment, the pin spacing is measured by bringing the vernier caliper 71 into contact with the respective wall surfaces of the two pins 51.

[0090] Therefore, distances can be measured using a low-cost and universal method such as the Vernier 71.

[0091] The preferred embodiments of the present invention have been described above, but the above structure may also be modified in the following ways.

[0092] If pin 51 does not impede the operation of the industrial robot 6, it can remain installed even after the initial origin calibration. Therefore, at least one pin 51 can also be non-removably fixed to the second joint body 12 or the second arm 22.

[0093] Alternatively, the pin 51 can be fixed to the second joint body 12 or the second arm 22 by means other than screwing (e.g., by inserting the pin into the conical cavity).

[0094] Alternatively, the two pins 51 can be made to protrude in the same direction instead of in opposite directions.

[0095] Even if joints 31 and 41 are not formed, space can still be ensured for the pins 51 used as markers, so joints 31 and 41 can be omitted.

[0096] The two pins 51 can also have different shapes. For example, the diameters of the two cylindrical portions 55 can be different. The cross-sectional profile of one or both pins 51 on the plane perpendicular to the rotation axis c4 can also not be circular.

[0097] The distances between the axes of the two pins 51 and the rotation axis c4 can also be different. In this case, the triangle is not... Figure 6 The bilateral triangle shown. However, if the distance between the axis of each pin 51 and the axis of rotation c4 is known, θ can be calculated using the law of cosines.

[0098] It can replace pin 51 and be used as a marker in the cylindrical recess formed by joint 31 and joint 41. The cylindrical axis of the recess can be arranged parallel to the rotation axis c4. In this case, the distance between the centers of the recess can be obtained by measuring the distance between the inner circumferential surfaces (wall surfaces) of the recess with vernier calipers 71.

[0099] The angle calibration method of the present invention can be applied to any two components of an industrial robot 6 that are connected by joints.

[0100] The angle calibration method of this invention is not limited to vertical multi-joint robots, but is also applicable to horizontal multi-joint robots. Furthermore, the angle calibration method of this invention is also applicable to cylindrical coordinate robots and polar coordinate robots.

[0101] Explanation of reference numerals in the attached figures

[0102] 6. Industrial robots (robotics)

[0103] 12. Second joint body (first component)

[0104] 22. Second arm (second component)

[0105] 31 Joint

[0106] 32 installation holes

[0107] 36 tapered recess

[0108] 41 Joint

[0109] 42 installation holes

[0110] 46 tapered recess

[0111] 51 Pin (Marking)

[0112] 55 Cylindrical section

[0113] 56 conical parts

[0114] 71 Vernier Caliper

Claims

1. An angle calibration method, comprising a robot having a first component, a second component rotatably connected to the first component, and an actuator that changes the angle of the second component relative to the first component according to a command value, characterized in that: Include In the first step, under a state where the actuator is given an arbitrary command value, the distance between the walls of two measuring objects is measured to obtain the distance between the two measuring objects, which is the distance between the two measuring objects. The two measuring objects are two measuring objects, one disposed on the first component and the other disposed on the second component. The second step involves calculating the angle difference corresponding to the difference between the two measurement object distances, based on the reference measurement object distance obtained by measuring the distance between the measurement object parts under conditions where the actuator has been given arbitrary command values, and the measurement object distance obtained in the first step. Of the two measuring objects, one is configured as a pin protruding from the first component, and the other is configured as a pin protruding from the second component. The two pins protrude in opposite directions. The axial direction of the two pins is parallel to the axial direction of the central axis of rotation of the second component relative to the first component.

2. The angle calibration method as described in claim 1, characterized in that: At least one of the two pins is detachable from the first component or the second component.

3. The angle calibration method as described in claim 2, characterized in that: At least one of the two pins is installed in a screw hole formed on the first component or the second component.

4. The angle calibration method as described in claim 2, characterized in that: At least one of the two pins has a tapered portion. A tapered recess corresponding to the tapered portion is formed on the first component or the second component.

5. The angle calibration method according to any one of claims 1 to 4, characterized in that: The cross-sectional profile of the two measured objects along a plane perpendicular to the central axis of the second component is circular.

6. The angle calibration method as described in claim 5, characterized in that: The diameters of the circles representing the cross-sectional profiles of the two measured objects are equal.

7. The angle calibration method according to any one of claims 1 to 4, characterized in that: The distances between the two measurement objects and the central axis of the second component are equal.

8. The angle calibration method according to any one of claims 1 to 4, characterized in that: In the first step, the distance between the two measuring objects is measured by contacting the walls of the two measuring objects with a vernier caliper.

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