Automatic teaching method for robots and robot control device

Abstract

To be able to automatically teach centers of stages to a robot that conveys a work-piece between the stages, more accurately.SOLUTION: An automatically teaching method of a robot executes: a step (a step 101) of making a hand 14 of a robot 1 approach a position-determining jig 61 from three different directions to determine position coordinates (X1 and Y1) of the position-determining jig 61 in a robot coordinate system, when the position-determining jig 61 in a columnar shape is arranged at a known position with respect to a center C of a stage, in a Y-direction pointing from inside of a working area 5 in which the robot 1 is installed to the center of the stage; and a step (a step 102) of making the hand 14 approach the position-determining jig 61 along the Y-direction to determine a Y coordinate value Y2 of the position-determining jig in the robot coordinate system. The position coordinates (X1 and Y2) are used as coordinates for the position-determining jig 61 that are used in teaching the robot 1.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an automatic teaching method for a robot, and to a robot control apparatus that executes such an automatic teaching method. [Background Art]

[0002] In a semiconductor device manufacturing process, a transfer robot that transfers a semiconductor wafer, which is a workpiece, between stages is used. In the following description, objects that are targets of workpiece pickup (i.e., loading) and unloading (i.e., unloading) by a robot are collectively referred to as stages. Cassettes used for storing wafers in semiconductor manufacturing processes and workpiece processing apparatuses that perform any processing on wafers are each a stage. Each stage has a strictly defined area where a workpiece should be placed when transferred by the robot (referred to as a workpiece placement area), and the center of the workpiece placement position is referred to as the stage center. In order to transfer workpieces between stages using a robot, it is necessary to teach the robot the coordinates of the stage center in the robot's coordinate system for each stage. In the case where a horizontal articulated robot transfers a plate-shaped workpiece such as a semiconductor wafer, the workpiece is transferred while maintaining its horizontal posture, and the workpiece is slightly moved in the vertical direction for loading and unloading the workpiece on the stage, so it is only necessary to accurately teach the stage center in the horizontal plane.

[0003] Conventionally, the precise position of the stage was taught to the robot by connecting a pendant to a robot control device that controls the robot and manually operating the robot via the pendant. However, manual teaching has problems such as variations depending on the worker performing the teaching and the long time required for teaching. The approximate positional relationship between the robot and the stage is known from the design data of the robot and stage, and the installation data when the robot and stage are installed on site.Therefore, Patent Documents 1 and 2 disclose a method for accurately determining the stage center by placing a cylindrical jig (also called a pin) whose positional relationship with the center of the stage is known inside the stage, and detecting this jig non-contactively by a sensor attached to the hand (also called an end effector) of the robot's tip while moving it in three different directions.According to this method, the position of the center of the stage can be accurately determined in the robot's coordinate system, and automatic teaching of the stage center can be performed.As the sensor, a through-beam sensor equipped with a light-emitting part and a light-receiving part that detects when the optical path is blocked by the jig is used. Patent Document 3 discloses methods for improving detection accuracy when detecting jigs using a through-beam sensor by performing regression analysis by performing multiple detection operations, or by performing least-squares approximation and numerical search. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-284728 [Patent Document 2] Japanese Patent Publication No. 2013-153187 [Patent Document 3] Special Publication No. 2022-520052 [Overview of the project] [Problems that the invention aims to solve]

[0005] When determining the coordinate values ​​of the stage center by non-contact detection of a cylindrical jig using a through-beam sensor mounted on the hand, the error in determining the coordinate values ​​may not always be small, which can prevent the robot from being automatically taught with sufficient accuracy.

[0006] The object of the present invention is to provide an automatic teaching method that can more accurately automatically teach the center of the stage, and a robot control device that performs such an automatic teaching method. [Means for solving the problem]

[0007] An automatic teaching method according to one aspect of the present invention is an automatic teaching method for a robot equipped with a hand and positioned inside a work area, which automatically teaches the position of the center of a stage connected to the work area via an opening connection part, wherein an XY coordinate system is defined with the direction from inside the work area toward the center of the stage via the connection part as the Y direction and the direction perpendicular to the Y direction as the X direction, the XY coordinate system is made the robot coordinate system, and a cylindrical position-determining jig is placed inside the stage at a position where the relative positional relationship with the center of the stage is known, and the hand is moved inside the stage in three different directions The robot has a first position determination step in which the hand is brought close to the position determination jig, the position determination jig is detected non-contact by a sensor provided on the hand, and the coordinates of the position determination jig in the robot coordinate system consisting of a first X coordinate value and a first Y coordinate value, and a second position determination step in which the hand is moved along the Y direction to bring it close to the position determination jig, the position determination jig is detected non-contact by a sensor, and the Y coordinate value of the position determination jig in the robot coordinate system is obtained as a second Y coordinate value, and the first X coordinate value and the second Y coordinate value are used as the coordinates of the position determination jig in teaching the robot.

[0008] When a hand that detects a positioning jig without contact approaches the jig from three different directions to determine its position, the positioning error in the Y direction tends to be large. However, in one embodiment of the automatic teaching method, a second positioning step is separately performed in which the hand is moved along the Y direction to determine the Y coordinate value of the positioning jig in the robot coordinate system. This improves the accuracy of positioning the jig, and consequently, the accuracy of automatic teaching.

[0009] In one embodiment of the automatic teaching method, the robot is a horizontal articulated robot, and both the X and Y directions are directions within the horizontal plane. In this case, if the horizontal articulated robot is a transport robot that transports workpieces, the frequency of workpiece placement failures can be reduced. In this case, it is preferable to move the hand in the horizontal plane in the first position determination step. By moving the hand in the horizontal plane, the influence of mechanical errors in the robot caused by moving the hand in the vertical direction can be eliminated. In another embodiment, the Y direction is, for example, a direction perpendicular to the wall surface of the work area at the position of the connection part. With this configuration, when stages are lined up on the wall surface of the work area along the X direction, automatic teaching of the stage center of each stage can be easily performed.

[0010] In one embodiment of the automated teaching method, it is preferable to repeatedly perform the second position determination step to obtain the average value of the second Y coordinate value, and to use this average value as the second Y coordinate value for teaching the robot. By obtaining the average value of the second Y coordinate value, the position determination accuracy of the position determination jig is improved. In this case, it is preferable to repeatedly perform the second position determination step while changing the position of the hand in the X direction when moving the hand along the Y direction. The second Y coordinate value obtained in the second position determination step may vary depending on the position of the hand in the X direction, but by repeating the second position determination step while changing the position of the hand in the X direction, the position determination accuracy of the position determination jig is further improved.

[0011] In one embodiment of the automated teaching method, when the Y-direction is included in the three different directions used in the first position determination step, the Y-coordinate value of the position determination jig in the robot coordinate system obtained when the hand is moved along the Y-direction in the first position determination step may be used as the second Y-coordinate value for teaching the robot. By configuring it in this way, the first position determination step and the second position determination step can be performed simultaneously, thereby reducing the time required for automated teaching.

[0012] In one embodiment of the automated teaching method, the sensor is, for example, a through-beam sensor. When the robot is used for transporting semiconductor wafers, such a through-beam sensor is often provided to confirm the presence of wafers, and in such cases, the accuracy of automated teaching can be improved by using the existing through-beam sensor.

[0013] One embodiment of a robot control device controls a robot equipped with a hand and positioned inside a work area, and automatically teaches the robot the position of the center of a stage connected to the work area via an opening connection part, wherein an XY coordinate system is defined with the direction from inside the work area toward the center of the stage via the connection part as the Y direction and the direction perpendicular to the Y direction as the X direction, and the XY coordinate system is the robot coordinate system, and when a cylindrical position-determining jig is positioned inside the stage at a known position relative to the center of the stage, the hand is positioned inside the stage The robot is instructed to approach the positioning jig from three different directions, and the positioning jig is detected non-contact by a sensor on the hand. The coordinates of the positioning jig in the robot coordinate system are calculated from a first X coordinate value and a first Y coordinate value. The hand is then moved along the Y direction to approach the positioning jig, and the positioning jig is detected non-contact by a sensor to obtain the Y coordinate value of the positioning jig in the robot coordinate system as a second Y coordinate value. The robot is then taught by assuming that the coordinates of the positioning jig in the robot coordinate system are represented by the first X coordinate value and the second Y coordinate value.

[0014] When a non-contact hand is used to detect a positioning jig and approach it from three different directions to determine its position, the positioning error in the Y direction tends to be large. However, by using one embodiment of a robot control device, a second positioning process is also performed in which the hand is moved along the Y direction to determine the Y coordinate value of the positioning jig in the robot coordinate system. This improves the accuracy of positioning the positioning jig, and consequently, the accuracy of automatic teaching is also improved. [Effects of the Invention]

[0015] According to the present invention, it becomes possible to more accurately and automatically teach the robot the center of the stage. [Brief explanation of the drawing]

[0016] [Figure 1] (a) is a plan view of the robot, (b) is a schematic cross-sectional view along line BB in Figure 1(a), and (c) is an enlarged plan view of the hand. [Figure 2] (a) to (d) are diagrams illustrating stage-centered automated teaching. [Figure 3] This diagram illustrates the error in determining the coordinates of the jig center O. [Figure 4] This is a diagram illustrating an automated teaching method that is one embodiment of the present invention. [Figure 5] This is a flowchart explaining the automated teaching method. [Figure 6] This figure shows an example of the variation in Y-direction error due to position in the X-direction. [Modes for carrying out the invention]

[0017] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 shows a robot to which an automatic teaching method according to an embodiment of the present invention is applied. The illustrated robot 1 is a horizontal articulated robot, which is installed in a work area 5, for example, a rectangular space. The robot 1 is used to transfer plate-shaped workpieces 50 between stages 51 provided on wall surfaces surrounding the work area 5. The work area 5 is a space where the robot 1 can move its arms 11 to 13 and hand 14 without interfering with wall surfaces or the like when transferring the workpiece 50 between the stages 51. Each stage 51 is a place where the robot 1 loads and unloads the workpiece 50, and is connected to the work area 5 via a connection portion 52 thereof. The connection portion 52 is configured as an opening provided on a wall surface of the work area 5 so that the hand 14 of the robot 1 carrying the workpiece 50 can access the interior of the stage 51. Therefore, when the robot 1 loads or unloads a workpiece 50 to or from the stage 51, the moving direction of the hand 14 when passing through the connection portion 52 is generally a direction perpendicular to the wall surface of the work area 5. In addition, when the robot 1 loads or unloads the workpiece 50, a workpiece placement position 53, which is a position where the workpiece 50 is placed on the stage 51, is defined on the stage 51. The center of the workpiece placement position 53 is taken as a stage center C.

[0018] Next, a detailed configuration of the robot 1 will be described. The robot 1 includes a base 10 that is placed and fixed on the floor surface of a work area 5, three arms connected in series to the base 10, that is, a first arm 11, a second arm 12, and a third arm 13, and a hand 14 attached to the third arm 13. The base 10 includes a lifting cylinder 15 that is driven by a lifting motor (not shown) to move up and down in the vertical direction. Each of the arms 11 to 13 and the hand 14 has a base end and a distal end. The first arm 11 is held by the base 10 by rotatably connecting the base end of the first arm 11 to the lifting cylinder 15. The first arm 11 can move up and down relative to the base 10 as the lifting cylinder 15 moves up and down. The arms 11 to 13 and the hand 14 move up and down integrally by the lifting and lowering of the lifting cylinder 15. However, the present embodiment relates to teaching of the horizontal articulated robot 1 in a horizontal plane, and the movement in the height direction by the lifting cylinder 15 is smaller than the movement of the arms 11 to 13 and the hand 14 in the horizontal plane. Therefore, detailed description of the movement of the robot 1 in the height direction by the lifting cylinder 15 will be omitted below.

[0019] The first arm 11 is driven by a motor 21 built in the lifting cylinder 15 to rotate in a horizontal plane around a rotation axis J0. A base end of the second arm 12 is rotatably connected to a distal end of the first arm 11. The second arm 12 is held by the first arm 11 and driven by a motor 22 built in the first arm 11 to rotate in a horizontal plane around a rotation axis J1. Similarly, the base end of the third arm 13 is rotatably held by the distal end of the second arm 12, and the third arm 13 is driven by a motor 23 built in the second arm 12 to rotate in a horizontal plane around a rotation axis J2. The base end of the hand 14 is rotatably held by the distal end of the third arm 13, and the hand 14 is driven by a motor 24 built in the third arm 13 to rotate in a horizontal plane around a rotation axis J3.

[0020] Figure 1(c) is an enlarged plan view showing the configuration of the hand 14. The hand 14 has a fork-like branch at its tip, forming a fork section 20. When transporting, the workpiece 50 is placed horizontally on the surface of the fork section 20 by the hand 14. A light-emitting unit 26 that emits laser light is provided at the tip of one branch of the fork section 20, and a light-receiving unit 27 into which the laser light from the light-emitting unit 26 is incident is provided at the tip of the other branch, and the light-emitting unit 26 and the light-receiving unit 27 constitute a through-beam sensor 25. In the figure, the arrow pointing from the light-emitting unit 26 to the light-receiving unit 27 indicates the optical path 28 of the light from the light-emitting unit 26 to the light-receiving unit 27. The through-beam sensor 25 can detect, without contact, whether or not an object is blocking the optical path 28 between the light-emitting unit 26 and the light-receiving unit 27 by determining whether or not the light from the light-emitting unit 26 can be detected by the light-receiving unit 27. Such through-beam sensors 25 are generally provided in robots 1 used for transporting semiconductor wafers, in order to perform mapping to check the loading status of each slot in a cassette when the stage 51 is a cassette that stores workpieces 50 such as semiconductor wafers in each slot.

[0021] To explain the operation of robot 1, which is a horizontal articulated robot, we set up an XY coordinate system in the horizontal plane. Here, as shown in the figure, the work area 5 is a rectangular space with multiple stages 51 arranged along its long side. The direction in which the long side extends is defined as the X direction, and the direction perpendicular to the X direction is defined as the Y direction. When robot 1 accesses a stage 51 using its hand 14, the hand 14 moves in the Y direction, passes through the connection part 52, and enters the interior of the stage 51. The coordinate system of robot 1 in the horizontal plane (hereinafter referred to as the robot coordinate system) is represented by the XY coordinate system described above, with the position of the rotation axis J0 as the origin. Hereafter, the horizontal plane in which the XY coordinate system is set in this way will be referred to as the XY plane. Furthermore, when loading or unloading a workpiece 50 onto a stage 51, it is necessary to operate robot 1 using the coordinates of the stage center C in the robot coordinate system. Therefore, when teaching robot 1, it is necessary to teach the precise position of the stage center C in the XY plane. As shown in Figure 1(b), a robot control device 30 is connected to the robot 1, and the robot control device 30 can drive and control motors 21-24 and a lifting motor (not shown) based on commands input from an external source. The robot control device 30 can also control the robot 1 to perform the automatic teaching described below.

[0022] Next, we will explain automatic teaching for accurately determining the position of the stage center C in the robot coordinate system. In automatic teaching, the coordinates of the stage center C in the robot coordinate system in the horizontal plane, that is, the coordinates of the stage center C in the XY plane as described above, are determined. To do this, cylindrical position-determining jigs 61 and 62 are placed at two locations on the stage 51 that are away from the stage center C and whose relative position to the stage center C is known. In the figure, the position-determining jigs 61 and 62 are depicted as being placed on the outer circumference of the workpiece placement position 53, but the positions where the position-determining jigs 61 and 62 are placed are not limited to this. Since the position-determining jigs 61 and 62 are provided so as to be upright with respect to the XY plane, i.e., the horizontal plane, the axis of the cylindrical position-determining jigs 61 and 62 extends in the vertical direction, and the position of this axis in the XY plane is taken as the jig center O. If the coordinates of the centers O of the two position-determining jigs 61 and 62 in the robot coordinate system are known, then the positional relationship between each jig center O and the stage center C is also known, and thus the position of the stage center C in the robot coordinate system, i.e., its XY coordinate values, can be calculated.

[0023] Figure 2 illustrates automatic teaching. In this embodiment, the XY coordinate values ​​of the center O of each position-determining jig 61, 62 in the robot coordinate system are determined non-contact using a through-beam sensor 25 provided on the hand of the robot 1. The position-determining jigs 61, 62 are cylindrical, and their cross-sectional shape in the horizontal plane is a perfect circle, with the center of this circle being the jig center O. The robot 1 is then operated to bring the hand 14 closer to each position-determining jig 61, 62 from the side of the work area 5 in three different directions. In this case, since the hand 14 enters the stage 51 through the opening of the connection part 52, the range of angles that the hand 14 can take for each position-determining jig 61, 62 is constrained by the size of the opening of the connection part 52. Based on the design data for the work area 5 and stage 51, and the installation data indicating where robot 1 was placed within the work area 5, the approximate positions of the stage center C and each position-determining jig 61, 62, expressed in the robot coordinate system, are known. Therefore, the hand 14 can be brought closer to each position-determining jig 61, 62 without causing robot 1 to collide with the walls of the work area 5 or the stage 51.

[0024] Figure 2(a) shows the hand 14 approaching one of the positioning fixtures 61 from three different directions. When the hand 14 approaches the positioning fixture 61, the optical path 28 of the through-beam sensor 25 is blocked by the positioning fixture 61. At the moment the optical path 28 is blocked during the movement of the hand 14, the optical path 28 coincides with the tangent to the circle representing the outer circumference of the positioning fixture 61 in the XY plane. The angles of each axis of the robot 1 at the moment the optical path 28 is blocked can be determined from the outputs of encoders connected to motors 21-24, and the lengths of the arms 11-13 and the hand of the robot 1 are known. Therefore, based on the fact that the optical path 28 is blocked by the positioning fixture 61, the equation of the tangent to the circle represented by the positioning fixture 61 in the XY plane can be obtained. When the hand 14 is brought close to the positioning jig 61 from three different directions, three tangent lines L1 to L3 in the XY plane are obtained, as shown in Figure 2(b), and the equations for each of these tangent lines L1 to L3 can be obtained. If the intersection of the angle bisectors between these tangent lines is, for example, the angle bisector of tangent lines L1 and L2 is line M1, and the angle bisector of tangent lines L2 and L3 is line M2, then the intersection of lines M1 and M2 is the jig center O. Therefore, the exact XY coordinates of the jig center O of the positioning jig 61 can be determined from the equations of the tangent lines L1 to L3. By applying the same procedure to the other positioning jig 62, the exact XY coordinates of the jig center O of the positioning jig 62 can also be determined, and the exact positions of the positioning jigs 61 and 62 in the robot coordinate system have been determined. Since the precise relative positional relationship between the stage center C and the positioning jigs 61 and 62 is known, the precise position of the stage center C in the robot coordinate system can be determined using the precisely determined positioning jigs 61 and 62, as shown in Figure 2(c). In other words, the position of the stage center C can be automatically taught.

[0025] The above explanation describes the case where the two position-determining jigs 61 and 62 are placed away from the stage center C. However, as shown in Figure 2(d), if the position-determining jig 61 can be placed at the stage center C, the coordinates of the stage center C can be determined by determining the coordinates of the position-determining jig 61 in the robot coordinate system, as described above. In other words, in this case, automatic teaching of the stage center C can be performed using only one position-determining jig 61 placed at the stage center C.

[0026] However, due to various mechanical errors in the robot 1, the finite beam diameter of the optical path 28 of the through-beam sensor 25, and the influence of ambient light, errors occur when determining the positions of the position-determining fixtures 61 and 62 in the robot coordinate system, i.e., the coordinates of the fixture centers O, as described above. These errors result in teaching errors for the stage center C. As mentioned above, there are constraints on the angular range that the hand 14 can take when approaching the position-determining fixtures 61 and 62. For example, the hand 14 can only approach the position-determining fixtures 61 and 62 from an angular range of, for example, several tens of degrees, centered on the respective fixture centers O of the position-determining fixtures 61 and 62 and facing the work area 5. As a result, when determining the coordinates of the fixture centers O in the robot coordinate system, the error in the Y coordinate value is larger than the error in the X coordinate value.

[0027] Figure 3 illustrates the error when determining the jig center O. It shows how the results of each position determination varied when the operation of determining the position of the same position determination jig 61 provided on the stage 51 was repeatedly performed. A larger variation indicates a larger error. In one position determination, the coordinates of the jig center O are determined by approaching the position determination jig 61 from three directions with the hand 14. At the same time, the radius R of the position determination jig 61 in cross-section using the XY plane can also be calculated. In the figure, the small solid circles indicate the position of the contact point when the optical path 28 of the through-beam sensor 25 coincides with the tangent to the position determination jig 61 during position determination. The dashed circles indicate the outer circumference of the position determination jig 61 in the XY plane, calculated backward from the position determination results. As shown in the figure, when the position of the jig center O is determined multiple times, the variation in the X direction is small, while the variation in the Y direction is large. This indicates that, assuming the coordinates of the jig center O are determined by a single position determination, the error in the Y direction will be greater than the error in the X direction.

[0028] In this embodiment, a first position determination step and a second position determination step are performed in order to more accurately determine the coordinates of the jig center O in the robot coordinate system. Taking one position determination jig 61 as an example, in the first position determination step, as described above, the hand 14 is brought close to the position determination jig 61 from three different directions to determine the coordinates of the jig center O. At this time, the radius R of the position determination jig 61 may also be determined. The coordinates of the jig center O determined at this time are denoted as (X1, Y1). Separately, in the second position determination step, as shown in Figure 4(a), the hand 14 is moved along the Y direction toward the position determination jig 61, and the optical path 28 of the through-beam sensor 25 is detected to be blocked by the position determination jig 61 to determine the Y coordinate Y2 of the jig center O in the robot coordinate system. At this time, the Y coordinate Ya of the position where the optical path 28 of the through-beam sensor 25 is blocked may be determined based on the position of the hand 14 when the optical path 28 is blocked, and the previously determined radius R may be added to it to obtain the coordinate value Y2. Alternatively, the hand 14 may be moved in the Y direction even after the optical path 28 is blocked to determine the Y coordinate Yb of the position where the optical path 28 is no longer blocked, and the coordinate value Y2 may be determined by Y2 = (Ya + Yb) / 2. In this embodiment, the X coordinate value X1 obtained in the first position determination step and the Y coordinate value Y2 obtained in the second position determination step are combined to make (X1, Y2) the coordinate of the jig center O of the position determination jig 61.

[0029] Figure 5 is a flowchart illustrating the automatic teaching method of this embodiment, showing the process of determining the jig center O of the position determination jig 61. First, in step 101, a first position determination process is performed, in which the hand 14 is brought close to the position determination jig 61 from three different directions to determine the coordinates (X1, Y1) of the position of the position determination jig 61 in the robot coordinate system. Next, in step 102, a second position determination process is performed, in which the hand 14 is brought close to the position determination jig 61 along the Y direction to determine the Y coordinate value Y2 of the position determination jig 61 in the robot coordinate system. Finally, in step 103, (X1, Y2) is set as the position of the position determination jig 61 in the robot coordinate system, i.e., the coordinates of the jig center O. In order to execute the process shown in Figure 5, the robot control device 30 controls the robot 1 and monitors the output of the light receiving unit 27 of the through-beam sensor 25, and performs calculations to determine the coordinates of the jig center O in the robot coordinate system.

[0030] Similarly, the first and second position determination steps are performed on the other position determination jig 62 to determine the coordinates of the jig center O. Once the precise positions of the two position determination jigs 61 and 62 in the robot coordinate system are determined, the coordinates of the stage center C in the robot coordinate system are calculated based on the relative positional relationship between the position determination jigs 61 and 62 and the stage center C. Even when the position determination jig 61 is placed on the stage center C itself (as shown in Figure 2(d)), as shown in Figure 4(b), the second position determination step involves moving the hand 14 closer to the position determination jig 61 along the Y direction to determine the Y coordinate value Y2 of the position determination jig 61 in the robot coordinate system.

[0031] In this embodiment, in addition to the first position determination step of determining the XY coordinate values ​​of the jig center O by moving the hand 14 from three different directions, a second position determination step is performed in which the hand 14 is moved along the Y direction to determine the Y coordinate of the jig center O. This reduces the error in the Y direction of the jig center O's coordinates, thereby reducing the error in the jig center O's coordinates and, consequently, the teaching error of the stage center C in automatic teaching. To further reduce the teaching error by reducing the error in the jig center O's coordinates, it is effective to repeatedly perform the first and second position determination steps and calculate the average value. That is, it is preferable to perform the first position determination step multiple times and determine the coordinates (X1, Y1) of the jig center O from the average of the results, and to perform the second position determination step multiple times and determine the Y coordinate value Y2 of the jig center O from the average of the results. In particular, in the second position determination step, since the Y coordinate value is considered to have a relatively large error among the coordinate values ​​obtained by the first position determination step, it is preferable to increase the number of repetitions. Furthermore, if the Y direction is included among the three different directions used when moving the hand 14 closer to the positioning jigs 61 and 62 in the first positioning step, the first positioning step may be performed to determine the coordinates (X1, Y1) of the jig center O, and the data obtained in the first positioning step when the hand 14 is moved in the Y direction may be treated as data to be used in the second positioning step to determine the Y coordinate value Y2.

[0032] In the second position determination step, the hand 14 is moved along the Y direction to detect when the optical path 28 of the through-beam sensor 25 is obstructed by the position determination jigs 61 and 62. At this time, the direction in which the optical path 28 extends is the X direction. The length of the optical path 28, that is, the narrow distance between the light-emitting part 26 and the light-receiving part 27 of the through-beam sensor 25, depends on the size of the workpiece 50 assumed by the robot 1, but is for example, several centimeters to several tens of centimeters. In contrast, the radius of the cylindrical position determination jigs 61 and 62 is about several millimeters to several centimeters. The radius of the position determination jigs 61 and 62 is sufficiently small compared to the length of the optical path 28. The Y coordinate value Y2 of the position of the position determination jigs 61 and 62 in the robot coordinate system should not change depending on where in the X direction the optical path 38 obstructs the position determination jigs 61 and 62 when the hand 14 is moved in the Y direction. However, in reality, due to mechanical errors in the robot 1, particularly angular transmission errors in the reduction gear installed in the robot 1, the Y coordinate value Y2 changes periodically depending on the position of the hand 14 in the X direction. Figure 6 shows an example of how the Y coordinate value differs depending on the position of the hand 14 in the X direction when the hand 14 is moved in the Y direction to detect the position determination jig 61. Three measurements were taken for each position in the X direction. If the position of the hand 14 in the X direction is the same, the variation in the obtained Y coordinate value is extremely small (e.g., about 0.1 mm), but if the position in the X direction is different, the Y coordinate value also changes significantly. If the influence of such variation in the Y coordinate value on the teaching error cannot be ignored, it is preferable to change the position of the hand 14 in the X direction each time the second position measurement step is performed, within a range that satisfies the condition that the optical path 28 is blocked by the position determination jigs 61 and 62, and average the obtained Y coordinate value Y2.

[0033] When the position (X1, Y1) of the jig center O in the robot coordinate system is determined by approaching the positioning jig with the hand from three different directions, the error in the Y direction tends to be large. However, according to the embodiment described above, by separately performing a second positioning step to determine the Y coordinate value Y2 of the jig center O, the error in the position of the jig center O in the Y direction can be reduced, and thereby the teaching error for the stage center C can also be reduced. By improving the accuracy of automatic teaching, the frequency of failures in placing the workpiece 50, which is the conveyed object, and the re-doing of automatic teaching can be reduced, and the productivity of the entire system, including the robot 1, can be improved.

[0034] Furthermore, this technology can be configured as follows:

[0035] (1) An automatic teaching method for automatically teaching a robot equipped with a hand and positioned inside a work area the position of the center of a stage connected to the work area via a connecting part which is an opening, The direction from inside the work area toward the center of the stage via the connection part is defined as the Y direction, and the direction perpendicular to the Y direction is defined as the X direction, and the XY coordinate system is defined as the robot coordinate system. The process involves placing a cylindrical position-determining jig at a position within the stage where its relative positional relationship with the center of the stage is known. A first position determination step involves moving the hand into the stage and approaching the position determination jig from three different directions, detecting the position determination jig non-contact using a sensor provided on the hand, and calculating the coordinates of the position determination jig in the robot coordinate system consisting of a first X coordinate value and a first Y coordinate value. A second position determination step involves moving the hand along the Y direction to approach the position determination jig, detecting the position determination jig non-contact with the sensor, and determining the Y coordinate value of the position determination jig in the robot coordinate system as a second Y coordinate value. It has, An automatic teaching method in which the first X coordinate value and the second Y coordinate value are used as the coordinates of the position determination jig in the teaching of the robot.

[0036] (2) The automatic teaching method according to (1), wherein the robot is a horizontal articulated robot, and both the X direction and the Y direction are directions in the horizontal plane.

[0037] (3) The automatic teaching method according to (2), wherein in the first position determination step, the hand is moved in the horizontal plane.

[0038] (4) The automatic teaching method according to any one of (1) to (3), wherein the Y direction is a direction perpendicular to the wall surface of the work area at the position of the connection portion.

[0039] (5) The automatic teaching method according to any one of claims (1) to (4), wherein the second position determination step is repeated to obtain the average value of the second Y coordinate values, and the average value is used as the second Y coordinate value for teaching the robot.

[0040] (6) The automatic teaching method according to (5), wherein the second position determination step is repeatedly performed while changing the position of the hand in the X direction when the hand is moved along the Y direction.

[0041] (7) The automatic teaching method according to any one of (1) to (6), wherein the Y direction is included in the three different directions used in the first positioning step, and the Y coordinate value of the positioning jig in the robot coordinate system obtained when the hand is moved along the Y direction in the first positioning step is used as the second Y coordinate value for teaching the robot.

[0042] (8) The automatic teaching method according to any one of (1) to (7)3, wherein the sensor is a through-beam sensor.

[0043] (9) A robot control device that controls a robot equipped with a hand and positioned inside a work area, and automatically teaches the robot the position of the center of a stage connected to the work area via a connecting part which is an opening, An XY coordinate system is defined with the direction from inside the work area toward the center of the stage via the connection part as the Y direction, and the direction perpendicular to the Y direction as the X direction, and the XY coordinate system is the robot coordinate system, and a cylindrical positioning jig is placed inside the stage at a position where its relative positional relationship with the center of the stage is known, The hand is brought into the interior of the stage and approached the position determination jig from three different directions, the position determination jig is detected non-contact by a sensor provided on the hand, and the coordinates of the position determination jig in the robot coordinate system consisting of a first X coordinate value and a first Y coordinate value are calculated. The hand is moved along the Y direction to approach the position determination jig, the position determination jig is detected non-contact by the sensor, and the Y coordinate value of the position determination jig in the robot coordinate system is obtained as a second Y coordinate value. A robot control device that teaches the robot, assuming that the coordinates of the position-determining jig in the robot coordinate system are represented by the first X coordinate value and the second Y coordinate value. [Explanation of Symbols]

[0044] 1...Robot; 5...Work area; 10...Base; 11...First arm; 12...Second arm; 13...Third arm; 14...Hand; 15...Lifting cylinder; 20...Fork section; 21-24...Motor; 25...Through-beam sensor; 26...Light-emitting part; 27...Light-receiving part; 28...Optical path; 30...Robot control device; 50...Workpiece; 51...Cassette; 52...Stage; 53...Workpiece placement position; 61, 62...Jig for position determination; C...Stage center; O...Jig center.

Claims

1. An automatic teaching method for automatically teaching the position of the center of a stage connected to a work area via an opening-shaped connection part to a robot equipped with a hand and positioned inside the work area, The direction from inside the work area toward the center of the stage via the connection part is defined as the Y direction, and the direction perpendicular to the Y direction is defined as the X direction, and the XY coordinate system is defined as the robot coordinate system. The process involves placing a cylindrical position-determining jig at a position within the stage where its relative positional relationship with the center of the stage is known. A first position determination step involves moving the hand into the stage and approaching the position determination jig from three different directions, detecting the position determination jig non-contact using a sensor provided on the hand, and calculating the coordinates of the position determination jig in the robot coordinate system consisting of a first X coordinate value and a first Y coordinate value. A second position determination step involves moving the hand along the Y direction to approach the position determination jig, detecting the position determination jig non-contact with the sensor, and determining the Y coordinate value of the position determination jig in the robot coordinate system as a second Y coordinate value. It has, An automatic teaching method in which the first X coordinate value and the second Y coordinate value are used as the coordinates of the position determination jig in the teaching of the robot.

2. The automatic teaching method according to claim 1, wherein the robot is a horizontal articulated robot, and both the X direction and the Y direction are directions in the horizontal plane.

3. The automatic teaching method according to claim 2, wherein in the first position determination step, the hand is moved in the horizontal plane.

4. The automatic teaching method according to any one of claims 1 to 3, wherein the Y direction is perpendicular to the wall surface of the work area at the location of the connection portion.

5. The automatic teaching method according to any one of claims 1 to 3, wherein the second position determination step is repeated to obtain the average value of the second Y coordinate values, and the average value is used as the second Y coordinate value for teaching the robot.

6. The automatic teaching method according to claim 5, wherein the second position determination step is repeatedly performed while changing the position of the hand in the X direction when the hand is moved along the Y direction.

7. The automatic teaching method according to any one of claims 1 to 3, wherein the Y direction is included in the three different directions used in the first position determination step, and the Y coordinate value of the position determination jig in the robot coordinate system obtained when the hand is moved along the Y direction in the first position determination step is used as a second Y coordinate value for teaching the robot.

8. The automatic teaching method according to any one of claims 1 to 3, wherein the sensor is a through-beam sensor.

9. A robot control device that controls a robot equipped with a hand and positioned inside a work area, and automatically teaches the robot the position of the center of a stage connected to the work area via an opening connection part, An XY coordinate system is defined such that the direction from inside the work area toward the center of the stage via the connection is the Y direction, and the direction perpendicular to the Y direction is the X direction, and the XY coordinate system is the robot coordinate system, and a cylindrical position-determining jig is placed inside the stage at a position where its relative positional relationship with the center of the stage is known, The hand is brought into the interior of the stage and approached the position determination jig from three different directions, the position determination jig is detected non-contact by a sensor provided on the hand, and the coordinates of the position determination jig in the robot coordinate system consisting of a first X coordinate value and a first Y coordinate value are calculated. The hand is moved along the Y direction to approach the position determination jig, the position determination jig is detected non-contact by the sensor, and the Y coordinate value of the position determination jig in the robot coordinate system is obtained as a second Y coordinate value. A robot control device that teaches the robot, assuming that the coordinates of the position-determining jig in the robot coordinate system are represented by the first X coordinate value and the second Y coordinate value.

Images