ROBOT CONTROL METHOD, ROBOT CONTROL DEVICE, AND INSPECTION SYSTEM

Abstract

To provide a control method for a robot, a control device for a robot, and an inspection system that enable quick inspection even for a hole of small dimensional tolerance.SOLUTION: A control method for a robot 2, according to an embodiment, comprises a force sensor 4 that detects a direction and magnitude of an external force applied to a hand of the robot 2 capable of holding a work piece 7 on a hand side. This control method controls the robot 2 by including: a rotation insertion step (S5) of, in a state in which a plug gauge 5 is fixed in a predetermined position in an operating range of the robot 2, inserting the plug gauge 5 into a hole portion 10 while rotating the work piece 7 and moving the work piece 7 in a direction in which the external force detected by the force sensor 4 decreases; and a determination step (S9) of determining quality of the hole portion 10, based on whether the work piece 7 has reached a predetermined target position while the plug gauge 5 is kept inserted in the hole portion 10.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a control method for a robot that inspects holes formed in a workpiece using a plug gauge, a control device for the robot, and an inspection system. [Background technology]

[0002] Conventionally, robots have been used to inspect holes formed in a workpiece. For example, Patent Document 1 proposes providing a force sensor on the robot, and moving an inspection gauge based on the detection value of the force sensor while fitting the inspection gauge into the hole to inspect the dimensions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-28227 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if a force sensor is provided on the robot to correct the position, the gauge needs to be inserted correctly into the hole for inspection, and the positional relationship between the gauge and the hole needs to be taught with high accuracy in advance. Conventionally, even experienced workers had to spend a lot of time and effort repeatedly readjusting the posture control parameters and teaching positions to achieve stable inspection operations.

[0005] The present invention has been made in consideration of the above-mentioned situation, and its object is to provide a robot control method, a robot control device, and an inspection system that are capable of quickly inspecting even holes with small dimensional tolerances. [Means for solving the problem]

[0006] The robot control method described in claim 1 includes a force sensor that detects the direction and magnitude of an external force applied to a hand of the robot capable of holding a workpiece on the hand side, and includes a rotation and insertion process in which, with the plug gauge fixed at a predetermined position within the operating range of the robot, the workpiece is rotated and moved in a direction in which the external force detected by the force sensor decreases while inserting the plug gauge into the hole, and a judgment process in which the quality of the hole is judged based on whether the workpiece has reached a predetermined target position with the plug gauge inserted in the hole.

[0007] When inspecting a hole using a plug gauge, it is necessary to insert the plug gauge into the hole. In this case, it is thought that it is possible to assist the insertion of the plug gauge by correcting the position to the side where the external force is reduced using a force sensor. However, if the control is simply repeated to move in the direction where the external force is reduced, the plug gauge will be inserted into the hole while the robot's hand makes an oscillatory movement like a pendulum that swings back and forth in a straight line.

[0008] In that case, the plug gauge, which is made of a highly rigid material and has a flat upper end at the small diameter portion as in the embodiment, may engage with the inner wall of the hole and become unable to be inserted, making inspection impossible.

[0009] Therefore, a control method is adopted that includes a rotation insertion process in which the plug gauge is inserted into the hole while rotating the workpiece and moving the workpiece in a direction in which the external force detected by the force sensor decreases. In this case, the center position of the hole always moves in the direction in which the external force decreases, i.e., toward the central axis of the plug gauge. In other words, by rotating the workpiece, it becomes possible to insert the plug gauge while gradually moving the center position of the hole closer to the central axis of the plug gauge.

[0010] This makes it possible to insert the plug gauge into the hole while reducing the risk of interference between the hole, which has a small dimensional tolerance, and the plug gauge. In addition, since the positional relationship between the hole and the plug gauge can be corrected during actual operation, inspection can be performed even in an actual field where the placement position of the workpiece in which the hole is formed may be slightly shifted. Therefore, the hole can be quickly inspected using the plug gauge.

[0011] In the robot control method described in claim 2, in the stage of inserting the tip of the plug gauge into the hole, the robot is controlled by a control method including a probing step of inserting the plug gauge into the hole while tilting the workpiece to the opposite side across the axis of the plug gauge from the position where the external force is detected by the force sensor, and moving the workpiece in a direction in which the external force detected by the force sensor decreases.

[0012] When inspecting holes with small dimensional tolerances, there is a high possibility that the plug gauge will get caught on the edge of the hole when it is inserted. In that case, even if precise positioning is performed in advance, there is a risk that the plug gauge will get caught on the edge of the hole in the actual site where the workpiece placement position may be slightly shifted.

[0013] Therefore, when inserting the tip of the plug gauge, the workpiece is tilted to the opposite side of the position where the external force was detected. This is because, if a certain position at the top end of the plug gauge gets caught on the edge of the hole, the upper part of the position on the opposite side of the central axis from that position is considered to be within the width of the hole. This makes it possible to easily insert the plug gauge into the hole while reducing the possibility of insertion errors during the insertion of the plug gauge into the hole, which is the basis of the inspection.

[0014] In the robot control method described in claim 3, the probing step is performed until the workpiece moves from the tip position of the plug gauge to a predetermined confirmation position. When inspecting a hole with a small dimensional tolerance, the gap between the plug gauge and the hole is considered to be very small. Therefore, if the tip side of the plug gauge can be inserted to a certain extent, that is, if the workpiece can be moved to the confirmation position, it is considered that the plug gauge can be inserted all the way in that state. This reduces the risk of interference between the plug gauge and the hole.

[0015] In the robot control method described in claim 4, the plug gauge is provided with a small diameter section at the tip for inspecting the minimum dimension of the hole, and a large diameter section at the rear end of the small diameter section for inspecting the maximum dimension of the hole, and in the judgment step, the quality of the hole is judged based on the inspection results of both the minimum and maximum dimensions of the hole. This makes it possible to inspect the minimum and maximum diameters of the hole in one inspection cycle, and therefore allows for efficient inspection.

[0016] The robot control device described in claim 5 is equipped with a force sensor that detects the direction and magnitude of an external force applied to the robot's hand, and is equipped with a control unit that controls the robot to perform a rotational insertion operation in which the plug gauge is inserted into the hole while rotating the workpiece in which a hole is formed, and moving the workpiece in a direction in which the external force detected by the force sensor decreases, when the plug gauge is fixed at a predetermined position within the robot's operating range, and a judgment unit that judges the quality of the hole based on whether the workpiece has reached a predetermined target position with the plug gauge inserted in the hole.

[0017] With such a configuration, the control device that implements the above-mentioned control method can also correct the positional relationship between the hole and the plug gauge during actual operation, making it possible to perform inspection even in an actual site where the placement position of the workpiece in which the hole is formed may be slightly shifted, and to quickly inspect the hole using the plug gauge, thereby obtaining effects similar to those of the control method.

[0018] The inspection system described in claim 6 includes a robot, a force sensor provided on the robot for detecting the direction and magnitude of an external force applied to the robot's hand, a plug gauge fixed at a predetermined position within the robot's operating range, a control unit for controlling the robot to perform a rotational insertion operation in which the plug gauge is inserted into a hole while rotating the workpiece and moving the workpiece in a direction in which the external force detected by the force sensor decreases, and a control device having a judgment unit for judging the quality of the hole based on whether the workpiece reaches a predetermined target position with the plug gauge inserted in the hole.

[0019] With this type of inspection system, it is possible to correct the positional relationship between the hole and the plug gauge during actual operation, making it possible to perform inspection even in an actual field where the position of the workpiece in which the hole is formed may be slightly misaligned, and it is possible to quickly inspect the hole using the plug gauge, thereby obtaining the same effects as the control method and control device described above. [Brief description of the drawings]

[0020] [Figure 1] A diagram showing the configuration of an inspection system and a robot control device. [Diagram 2] FIG. 13 is a diagram showing a schematic view of a state in which a hole of a workpiece is inserted into a plug gauge; [Diagram 3] FIG. 2 is a schematic diagram showing a manner in which a robot operates in a vibrational manner; [Figure 4] A diagram showing the flow of the inspection process [Diagram 5] FIG. 13 is a diagram showing a typical mode of a searching operation; [Figure 6] FIG. 13 is a schematic diagram showing a state in which a plug gauge and a hole interfere with each other; [Figure 7] FIG. 13 is a diagram showing a typical aspect of a rotational insertion operation; [Figure 8] A schematic diagram showing the workpiece in the stopped position [Figure 9] FIG. 13 is a diagram showing a schematic configuration example of another hole portion; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment will be described with reference to the drawings. As shown in Fig. 1, an inspection system 1 of this embodiment includes a robot 2, a control device 3 that controls the robot 2, a force sensor 4 provided on the tip side of the robot 2, and a plug gauge 5 fixed at a predetermined position within the operating range of the robot 2.

[0022] The robot 2 is a so-called six-axis robot of a horizontal articulated type, and includes a base 2a installed on the installation surface 6, a first arm 2b rotatably provided around a first axis (J1) perpendicular to the installation surface 6, a second arm 2c rotatably provided around a second axis (J2) perpendicular to the first axis, a third arm 2d rotatably provided around a third axis (J3) perpendicular to the second axis, a fourth arm 2e rotatably provided coaxially with the third arm 2d around a fourth axis (J4) perpendicular to the third axis, a fifth arm 2f rotatably provided around a fifth axis (J5) perpendicular to the fourth axis, and a flange 2g rotatably provided around a sixth axis (J6) perpendicular to the fifth axis. In this embodiment, the flange 2g is configured so that there is no limit to its rotation range.

[0023] In the following description, the side on which the flange 2g is provided is referred to as the hand of the robot 2. In addition, in the following description, one axis perpendicular to the installation surface 6 of the robot 2 is referred to as the Z axis, and two axes perpendicular to the Z axis and forming a plane parallel to the installation surface 6 are referred to as the X axis and the Y axis. In the case of this embodiment, the first axis of the robot 2 shown in FIG. 1 is the Z axis, the left-right direction in the figure is the X axis, and the direction perpendicular to the paper surface is the Y axis. In addition, the point where the first axis intersects with the installation surface 6 is the origin of the coordinate system of the robot 2.

[0024] The control device 3 includes a control unit 3a and a judgment unit 3b. The control unit 3a is composed of a microcomputer (not shown) and generates and outputs a control command for driving a motor (not shown) included in the robot 2, thereby controlling the operation of the robot 2, i.e., the posture of the robot 2. The judgment unit 3b, which will be described in detail later, judges whether or not the hole 10 formed in the workpiece 7 shown in FIG. 2 is good or bad based on whether the workpiece 7 has reached a predetermined target position with the plug gauge 5 inserted in the hole 10. In this embodiment, the judgment unit 3b is realized by software by executing a program in the control unit 3a.

[0025] 1 and 2, the force sensor 4 has a roughly cylindrical outer shape and is attached to the flange 2g of the robot 2 with its central axis coinciding with the sixth axis of the robot 2. This force sensor 4 detects force components acting in three mutually perpendicular axial directions and torque components acting around each axis, thereby detecting the direction and magnitude of the external force applied to the hand of the robot 2 in terms of force components in six directions.

[0026] A tool 8 for gripping the workpiece 7 is attached to the force sensor 4 on the side opposite to the flange 2g. This tool grips the workpiece 7 by changing the distance between two gripping portions 8a. Therefore, the force sensor 4 detects the direction and magnitude of the external force applied to the workpiece 7 or the tool 8 as the direction and magnitude of the external force applied to the hand of the robot 2. In the case of this embodiment, the force sensor 4 detects a force component acting in one direction along the sixth axis of the robot 2 and two directions perpendicular to the sixth axis, as well as a torque component acting around these axes.

[0027] The plug gauge 5 is fixed to a mounting surface 9 that is within the operating range of the robot 2 and is provided parallel to the installation surface 6 in this embodiment. The plug gauge 5 is used to inspect whether the diameter (D) and depth of a hole 10 formed in a workpiece 7 as shown in FIG. 2 are within a predetermined dimensional tolerance. For this reason, the plug gauge 5 is formed of a material with high rigidity to maintain dimensional accuracy. In this embodiment, since the hole 10 is assumed to be a through hole, the depth of the hole 10 corresponds to the thickness of the portion where the hole 10 is formed. In addition, the hole 10 has a flat shape in cross section without being chamfered on the opening side.

[0028] Now, minimum and maximum diameter values ​​are set as dimensional tolerances for the hole 10 formed in the workpiece 7. Therefore, the plug gauge 5 is provided with a small diameter portion 5a formed in a rod shape with a relatively small diameter at the tip side, which is the upper side in the figure, and a large diameter portion 5b formed in a rod shape with a relatively large diameter at the rear end side, which is the lower side in the figure of the small diameter portion 5a.

[0029] The small diameter portion 5a is formed with a diameter (D1) that can inspect the minimum value of the hole 10, and the large diameter portion 5b is set with a diameter (D2) that can inspect the maximum value allowed for the hole 10. The plug gauge 5 is provided with its center axis (JG) aligned along the Z-axis direction perpendicular to the mounting surface 9. The length (H1) of the small diameter portion 5a is formed longer than the depth of the hole 10. As a result, if the small diameter portion 5a on the pass-through side can be inserted into the hole 10 and the large diameter portion 5b on the stop side cannot be inserted into the hole 10, it can be determined that the hole 10 is formed within the range of the dimensional tolerance. The upper end of the small diameter portion 5a is not chamfered, and is flat when viewed in cross section.

[0030] The plug gauge 5 has a fixed overall length (H2), which is the distance from the placement surface 9 to the tip on the upper side in the figure. Therefore, the X and Y coordinates indicating the position of the central axis of the plug gauge 5 on the XY plane of the coordinate system of the robot 2, and the Z coordinates indicating the tip of the plug gauge 5 in the Z-axis direction are Equivalent to the tip positionThe Z coordinate indicating the upper end position can be known in advance. Note that the configuration of the plug gauge 5 is one example, and a configuration having an attachment structure below the large diameter portion 5b in the drawing can also be adopted.

[0031] Then, the inspection system 1 uses the robot 2 to grasp the workpiece 7 with the tool 8, moves the workpiece 7 to above the plug gauge 5, and inserts the plug gauge 5 into the hole 10 of the workpiece 7 to inspect the hole 10.

[0032] Next, the operation of the above-mentioned configuration will be described. In order to inspect the hole 10 using the plug gauge 5, it is considered possible to assist the insertion of the plug gauge 5 by providing a force sensor 4 on the robot 2 and correcting its position to the side that reduces the external force detected by the force sensor 4.

[0033] However, even if the force sensor 4 is provided to correct the position, it takes a lot of time and effort for even an experienced worker to repeatedly readjust the posture control parameters and teaching positions to ensure that the gauge is correctly inserted into the hole 10, resulting in stable inspection. These parameters are, for example, the direction and extent of the posture change in response to the detected external force.

[0034] Furthermore, when inspecting a hole 10 with a small dimensional tolerance, another problem may occur in which the plug gauge 5 cannot be inserted, as described below. Specifically, for example, as shown in Fig. 3, when the plug gauge 5 is inserted into the hole 10, if they interfere with each other, that is, come into contact with each other at point P1, the force sensor 4 detects an external force indicated by an arrow F1. At this time, the external force is detected in a direction passing through the central axis of the plug gauge 5 and point P1.

[0035] When an external force is detected, the control device 3 controls the robot 2 so as to reduce the external force. At this time, in this embodiment, since the plug gauge 5 is fixed and the hole 10, i.e., the workpiece 7, is configured to move, the control device 3 moves the hole 10 toward the radial outside of the plug gauge 5, as indicated by the arrow V1, along the direction of the external force so as to reduce the external force.

[0036] However, when the inspection target is a hole 10 with a small dimensional tolerance, it is expected that the gap between the plug gauge 5 and the hole 10 will be very small. For example, when the dimensional tolerance of the hole 10 is equivalent to H7 in the fit tolerance of JIS B 0401, it is expected that the gap between the plug gauge 5 and the inner wall of the hole 10 will be extremely small. Note that the allowable range equivalent to H7 is only an example, and is not intended to limit the target of the inspection system 1, and holes 10 with other fit tolerances can also be targeted.

[0037] Therefore, when the hole 10 is moved in a direction in which the external force decreases, the hole 10 may interfere with the plug gauge 5 at point P2, which is on the opposite side of point P1 across the plug gauge 5. If an external force indicated by arrow F2 occurs when interference occurs at point P2, the hole 10 is controlled to move in a direction in which the external force decreases, and therefore there is a possibility of interference again at point P3 on the opposite side. In that case, the external force indicated by arrow F3 is detected, and therefore movement in the direction in which the external force decreases is performed again.

[0038] For this reason, when control is repeated to simply move in a direction in which the external force decreases, the hand of the robot 2 makes a vibrating motion of swinging back and forth in a straight line like a pendulum while inserting the plug gauge 5 into the hole 10. However, when such a vibrating motion occurs, the plug gauge 5, which is made of a highly rigid material and has a flat upper end at the small diameter portion 5a, may engage with the inner wall of the hole 10 and become unable to be inserted, which may make inspection impossible.

[0039] Of course, if the robot 2 is moved to a position where the external force is no longer detected by a very small distance, such as the minimum unit of motion, when an external force is detected, it is possible to insert the plug gauge 5 without interfering with the hole 10. However, in that case, it is expected that the inspection time will be long because it takes time to move the robot 2 to a position where the external force is no longer detected. In addition, considering that the robot 2 performs repetitive tasks, a long inspection time will ultimately result in a large decrease in work efficiency.

[0040] Therefore, the inspection system 1 and control device 3 of this embodiment employ the control method described below to quickly inspect the hole 10 with small dimensional tolerances. Note that although the following process is performed by the control unit 3a and the determination unit 3b, for the sake of simplicity, the following description will be centered on the control device 3.

[0041] The control device 3 executes the inspection process shown in Fig. 4, and in step S1, moves the work 7 to above the plug gauge 5. At this time, based on the coordinates of the central axis position and the upper end position of the plug gauge 5 that are grasped in advance, the control device 3 moves the work 7 held by the tool 8 to a position at a predetermined height where the center of the hole 10 coincides with the central axis of the plug gauge 5 and does not contact the plug gauge 5, as shown in Fig. 2. Note that the work 7 is placed at a predetermined placement position before being held by the tool 8, and basically, by holding the work 7 at the placement position, the tool 8 holds the work 7 with the center of the hole 10 coinciding with the sixth axis of the robot 2.

[0042] Next, in step S2, the control device 3 moves the work 7 to the upper end position of the plug gauge 5. At this time, the control unit 3a moves the work 7 along the central axis of the plug gauge 5 so that the lower surface of the work 7 shown in FIG. 2, i.e., the surface on which the hole 10 is formed, is at the upper end position of the plug gauge 5. Then, in step S3, the control unit 3a performs a searching operation. This step S3 corresponds to a searching process.

[0043] As described above, if the workpiece 7 placed in the placement position is gripped by the tool 8, it is considered that the center of the hole 10 will basically coincide with the sixth axis. However, if the dimensional tolerance of the hole 10 is small, if the placement position of the workpiece 7 is slightly shifted, the center of the hole 10 and the center of the plug gauge 5 will be misaligned as shown in the contact state in Figure 5, and the upper end of the plug gauge 5 may come into contact with the edge of the hole 10.

[0044] At this time, the force sensor 4 detects the external force indicated by the arrow F4 at the contact position. Since the force sensor 4 detects the external force in six directions as described above, it is possible to grasp at which position in the circumferential direction of the hole 10 the contact has occurred.

[0045] Therefore, if an external force is detected when the workpiece 7 is moved to the contact position, the control device 3 tilts the workpiece 7 to the opposite side to the position where the external force is detected, as shown as a tilting operation in Fig. 5, and moves the workpiece 7 so that the gauge is inserted into the hole 10, as shown as an insertion operation in Fig. 5. This is because, when an external force is detected at a certain position at the upper end of the plug gauge 5, the position opposite to that position is considered to be within the range of the hole 10.

[0046] If a new external force is detected during insertion, the control device 3 repeats the probing operation of inserting the work 7 while tilting it in the opposite direction, while moving the work 7 along the central axis of the plug gauge 5. Move In this manner, the plug gauge 5 is inserted into the hole 10. At this time, in this embodiment, the control device 3 performs a tilting insertion operation while rotating the work 7, thereby inserting the plug gauge 5 into the hole 10 while checking that no interference occurs with respect to the entire circumferential direction of the plug gauge 5. This makes it possible to prevent insertion errors in which the end of the plug gauge 5 gets caught.

[0047] Next, in step S4, the control device 3 determines whether the workpiece 7 has reached a predetermined confirmation position. In other words, the control device 3 determines whether the upper end side of the plug gauge 5 has been inserted to a certain extent into the hole 10 without getting caught on the edge of the hole 10. This is because, in the case of a hole 10 with a small dimensional tolerance, the gap between the hole 10 and the plug gauge 5 is small as described above, and therefore, if the plug gauge 5 can be inserted to a certain extent, it can be assumed that continued insertion is possible in that position.

[0048] As one example, if the depth of hole 10 is, for example, 15 mm, then by setting the confirmation position to about 10 to 20% of that, it is believed that it will be possible to estimate whether plug gauge 5 can be inserted. However, the confirmation position is not limited to the above numerical range, and can be set appropriately based on the depth of hole 10 and dimensional tolerances.

[0049] If the workpiece 7 fails to reach the confirmation position, for example because the hole 10 is not formed according to the dimensions, the control device 3 judges NO in step S4, and proceeds to step S11 to perform error processing and end the current inspection. In this error processing, the fact that the inspection of the hole 10 has failed is reported or recorded as an inspection history. Note that the determination of whether the workpiece 7 has reached the confirmation position can be made based on the relationship between the control command value output to move the workpiece 7 and the actual position of the workpiece 7, etc.

[0050] On the other hand, if the workpiece 7 reaches the confirmation position, the control device 3 determines YES in step S4, and proceeds to step S5 to perform a rotation insertion operation. This step S5 corresponds to a rotation insertion process. In this rotation insertion operation, the control device 3 inserts the plug gauge 5 into the hole 10 while rotating the workpiece 7 and moving the workpiece 7 in a direction in which the external force detected by the force sensor 4 decreases, while maintaining the attitude of the workpiece 7 at the time of reaching the confirmation position. In other words, the rotation insertion operation is a combination of a rotation operation that rotates the workpiece 7, an insertion operation that inserts the plug gauge 5 into the hole 10, and a movement operation that moves the workpiece 7 in response to the external force.

[0051] For example, as shown as the check position state in Fig. 6, if the attitude of the workpiece 7 is slightly tilted when it reaches the check position, although this depends on the depth of the hole 10, if the workpiece 7 is moved in this attitude, the plug gauge 5 may interfere with the inner wall of the hole 10 at point P4, as shown as the interference state. Then, if the workpiece 7 is simply moved in a direction that reduces the external force based on the external force detected when the workpiece interferes at point P4, this may result in a vibrational movement as described above, making it impossible to insert the plug gauge 5.

[0052] Therefore, in step S5, as shown in Fig. 7, the control device 3 rotates the work 7 clockwise in a plan view perpendicular to the central axis of the plug gauge 5 as indicated by an arrow R, while moving the work 7 so as to insert the plug gauge 5 into the hole 10. At this time, in this embodiment, the work 7 is rotated at a rotational speed that allows the work 7 to rotate at least one time before it reaches a target position described later.

[0053] 7 is provided for reference as a black square mark M1 to indicate the manner in which the workpiece 7 rotates. It is possible to arbitrarily select whether to rotate the workpiece 7 clockwise or counterclockwise. In this embodiment, the control device 3 rotates the flange 2g to rotate the workpiece 7 in the rotary insertion operation.

[0054] 7, when the plug gauge 5 interferes with the workpiece 7 at point P4, the plug gauge 5 is inserted while the workpiece 7 rotates and moves in the direction in which the external force decreases, as indicated by arrow V4, as shown in rotational movement state A. At this time, by setting the amount of movement of the workpiece 7 within a range that does not exceed the minimum value of the expected difference between the diameter of the plug gauge 5 and the diameter of the hole 10, it is possible to reduce the risk of the two colliding with each other due to excessive force.

[0055] Then, if the control unit 3a detects interference with the plug gauge 5 at point P5 when rotating and moving the workpiece 7 and an external force indicated by arrow F5 is detected, the control unit 3a rotates the workpiece 7, as shown in rotational movement state B, while moving the workpiece 7 in the direction in which the external force indicated by arrow V5 is reduced, and moves the workpiece 7 so as to insert the plug gauge 5 into the hole 10.

[0056] In this way, by inserting the plug gauge 5 while rotating the work 7, the center position of the hole 10 always moves in the direction in which the external force is reduced when an external force is detected, that is, toward the central axis of the plug gauge 5. In other words, by inserting the plug gauge 5 while rotating the work 7, it is possible to move the center position of the hole 10 closer to the central axis of the plug gauge 5. As a result, it is possible to insert the plug gauge 5 into the hole 10 while reducing the risk of interference between the hole 10 and the plug gauge 5.

[0057] Now, the control device 3 continues the rotational insertion operation until the workpiece 7 reaches the target position, as shown by rotational movement state C and rotational movement state D. In this embodiment, this target position corresponds to the depth of the hole 10. Then, in step S6, the control device 3 determines whether the workpiece 7 has reached the target position with the plug gauge 5 inserted into the hole 10.

[0058] At this time, the control device 3 determines whether the workpiece 7 has reached the target position based on the relationship between the control command and the actual position of the workpiece 7. If the workpiece 7 has not reached the target position, for example because the hole 10 is not needed, the result is NO in step S6, and the process proceeds to step S11 to perform error processing and terminate this inspection.

[0059] On the other hand, if the workpiece 7 reaches the target position, the control device 3 determines YES in step S6, and moves the workpiece 7 further to a stop position in step S7. This stop position corresponds to the position of the upper end of the large diameter portion 5b of the plug gauge 5. Specifically, it corresponds to a position moved a distance of H1 from the upper end of the plug gauge 5, or a position (H2-H1) from the surface of the mounting surface 9. Note that step S7 and step S8 described later are steps for inspecting the maximum diameter of the hole portion 10, and therefore can be omitted when it is only necessary to inspect the minimum diameter of the hole.

[0060] When the control device 3 moves the workpiece 7 to the stop position, in step S8, it determines whether the workpiece 7 will move beyond the stop position. This determination can be made by outputting a control command value for moving the workpiece 7 to a position beyond the stop position and confirming the actual position of the workpiece 7.

[0061] Since the large diameter portion of the plug gauge 5 is a portion for inspecting the maximum diameter of the hole 10, if the diameter of the hole 10 is within the range of the dimensional tolerance, the large diameter portion will not be inserted into the hole 10, and the work 7 will not move beyond the stop position downward as shown in FIG. 8. In other words, a situation in which the work 7 moves to a position beyond the stop position means that the large diameter portion 5b of the plug gauge 5 is inserted into the hole 10, and the hole 10 is formed with a size that exceeds the dimensional tolerance. Therefore, when the work 7 moves beyond the stop position, the controller 3 determines YES in step S8, and proceeds to step S11 to perform error processing and terminates the current inspection.

[0062] On the other hand, if the workpiece 7 does not move beyond the stop position, the control device 3 judges the hole 10 to be good in step S9 because the result in step S8 is NO. In other words, it is judged that the hole 10 is formed within the range of the dimensional tolerance. This step S9 corresponds to the judgment process. Then, in step S10, the control device 3 performs a rotation removal operation to remove the workpiece 7 from the plug gauge 5 while rotating it, and ends this inspection. In this way, the inspection system 1 inspects the hole 10 formed in the workpiece 7 using the plug gauge 5, and in the judgment process, judges the pass / fail of the hole 10 based on the inspection results of both the minimum dimension and the maximum dimension of the hole 10.

[0063] According to the embodiment described above, the following effects can be obtained. When inspecting a hole 10 formed in a workpiece 7 using a plug gauge 5, the robot 2 is provided with a force sensor 4 that detects the direction and magnitude of an external force applied to the hand, and the plug gauge 5 is fixed at a predetermined position within the operating range of the robot 2. The robot 2 is controlled by a control method including a rotation insertion process in which the workpiece 7 is rotated and moved in a direction in which the external force detected by the force sensor 4 decreases while inserting the plug gauge 5 into the hole 10, and a determination process in which the quality of the hole 10 is determined based on whether the workpiece 7 reaches a predetermined target position with the plug gauge 5 inserted in the hole 10.

[0064] When inspecting the hole 10 using the plug gauge 5, it is necessary to insert the plug gauge 5 into the hole 10. In this case, it is considered possible to assist the insertion of the plug gauge 5 by correcting the position using the force sensor 4 to the side where the external force is reduced. However, if the control of simply moving in the direction where the external force is reduced is repeated, the plug gauge 5 will be inserted into the hole 10 while the hand of the robot 2 makes an oscillatory movement like a pendulum reciprocating in a straight line.

[0065] In that case, the plug gauge 5, which is made of a highly rigid material and has a flat upper end at the small diameter portion 5a as in the embodiment, may engage with the inner wall of the hole 10 and become unable to be inserted, which may make inspection impossible.

[0066] Therefore, a control method is adopted that includes a rotation insertion step in which the plug gauge 5 is inserted into the hole 10 while rotating the workpiece 7 and moving the workpiece 7 in a direction in which the external force detected by the force sensor 4 decreases. In this case, the center position of the hole 10 always moves in the direction in which the external force decreases, that is, toward the central axis of the plug gauge 5. In other words, by rotating the workpiece 7, it becomes possible to insert the plug gauge 5 while gradually moving the center position of the hole 10 closer to the central axis of the plug gauge 5.

[0067] This makes it possible to insert the plug gauge 5 into the hole 10 while reducing the risk of interference between the hole 10, which has a small dimensional tolerance, and the plug gauge 5. In addition, since the positional relationship between the hole 10 and the plug gauge 5 can be corrected during actual operation, inspection can be performed even in an actual site where the placement position of the workpiece 7 in which the hole 10 is formed may be slightly shifted. Therefore, the inspection of the hole 10 can be performed quickly using the plug gauge 5.

[0068] In addition, in the stage of inserting the tip of the plug gauge 5 into the hole 10, the robot 2 is controlled by a control method including a probing process in which the workpiece 7 is tilted to the opposite side of the axis of the plug gauge 5 relative to the position where the external force is detected by the force sensor 4, and the plug gauge 5 is inserted into the hole 10 while moving the workpiece 7 in a direction in which the external force detected by the force sensor 4 decreases.

[0069] When a hole 10 having a small dimensional tolerance is to be inspected, there is a high possibility that the plug gauge 5 will get caught on the edge of the hole 10 when the plug gauge 5 is inserted. In that case, even if precise positioning is performed in advance, in an actual site where the placement position of the workpiece 7 may be slightly shifted, the plug gauge 5 may get caught on the edge of the hole 10.

[0070] Therefore, when inserting the tip of the plug gauge 5, the workpiece 7 is tilted to the opposite side of the position where the external force was detected. This is because, when a certain position of the upper end of the plug gauge 5 gets caught on the edge of the hole 10, the upper side of the position opposite to that position across the central axis is considered to be within the range of the width of the hole 10. This makes it possible to easily insert the plug gauge 5 into the hole 10 while reducing the possibility of an insertion error occurring when inserting the plug gauge 5 into the hole 10, which is the basis of the inspection.

[0071] The probing process is performed until the workpiece 7 moves from the tip position of the plug gauge 5 to a predetermined confirmation position. When inspecting a hole 10 with a small dimensional tolerance, the gap between the plug gauge 5 and the hole 10 is considered to be very small. Therefore, if the tip side of the plug gauge 5 can be inserted to a certain extent, that is, if the workpiece 7 can be moved to the confirmation position, it is considered that the plug gauge 5 can be inserted all the way in that state. This can reduce the risk of interference between the plug gauge 5 and the hole 10.

[0072] The plug gauge 5 has a small diameter section 5a at its tip end for inspecting the minimum dimension of the hole 10, and a large diameter section 5b at its rear end for inspecting the maximum dimension of the hole 10, and in the rotation insertion process, after the small diameter section 5a is inserted into the hole 10, the work 7 is moved to the large diameter section 5b. This makes it possible to inspect the minimum and maximum diameters of the hole 10 in one inspection cycle, enabling efficient inspection.

[0073] The control device 3 is also equipped with a force sensor 4 that detects the direction and magnitude of an external force applied to the hand of the robot 2. When the plug gauge 5 is fixed at a predetermined position within the operating range of the robot 2, the control unit 3a controls the robot 2 to perform a rotational insertion operation in which the workpiece 7 in which the hole 10 is formed is rotated and the workpiece 7 is moved in a direction in which the external force detected by the force sensor 4 decreases, while the plug gauge 5 is inserted into the hole 10. The control device 3 is also equipped with a determination unit 3b that determines whether the hole 10 is good or bad based on whether the workpiece 7 reaches a predetermined target position with the plug gauge 5 inserted in the hole 10. The control device 3 is capable of implementing the above-mentioned control method. Since the positional relationship between the hole 10 and the plug gauge 5 can be corrected during actual operation, inspection can be performed even in an actual field where the placement position of the workpiece 7 in which the hole 10 is formed may be slightly shifted. In addition, the plug gauge 5 can be used to quickly inspect the hole 10, and other effects similar to those of the control method can be obtained.

[0074] In addition, the inspection system 1 includes a robot 2, a force sensor 4 provided on the robot 2 for detecting the direction and magnitude of an external force applied to the hand of the robot 2, a plug gauge 5 fixed at a predetermined position within the operating range of the robot 2, a control unit 3a for controlling the robot 2 to perform a rotational insertion operation in which the plug gauge 5 is inserted into the hole 10 while rotating the workpiece 7 and moving the workpiece 7 in a direction in which the external force detected by the force sensor 4 decreases, and a control device 3 having a judgment unit 3b for judging the quality of the hole 10 based on whether the workpiece 7 reaches a predetermined target position with the plug gauge 5 inserted in the hole 10. Therefore, the positional relationship between the hole 10 and the plug gauge 5 can be corrected during actual operation, so that inspection can be performed even in an actual field where the placement position of the workpiece 7 in which the hole 10 is formed may be slightly shifted, and the hole 10 can be quickly inspected using the plug gauge 5. Thus, the same effects as those of the control method and control device 3 described above can be obtained.

[0075] The present invention is not limited to the embodiments described above or illustrated in the drawings, and can be modified or expanded without departing from the spirit and scope of the present invention. For example, although the embodiment has been described with respect to a configuration for inspecting the hole portion 10 of a through hole, it is also possible to inspect a non-through hole portion 10 as shown as a non-through hole in Fig. 9. In this case, the stopping position of step S8 in the inspection process shown in Fig. 4 may be set to the maximum depth of the hole portion 10.

[0076] Alternatively, as shown in Fig. 9 as a multi-stage hole, a hole portion 10 in which a small hole 10a and a large hole 10b are formed concentrically can be inspected. In this case, the same inspection as in the embodiment can be performed by making the small hole 10a side the contact position. Also, by using a plug gauge 5 having a small diameter portion 5a and a large diameter portion 5b for inspecting the small hole 10a, and a small diameter portion 5a and a large diameter portion 5b for inspecting the large hole 10b, the small hole 10a and the large hole 10b can be inspected in one inspection. Note that a multi-stage hole having three or more stages can also be inspected.

[0077] Furthermore, although the embodiment has been exemplified as a configuration using a so-called 6-axis robot, it is also possible to adopt a so-called 7-axis robot with one more degree of freedom, or a so-called 4-axis robot of a horizontally articulated type. Furthermore, in the embodiment, an example has been shown in which the rotary insertion operation is performed by rotating the flange 2g of the robot 2, but the rotary insertion operation can also be performed by rotating the tool 8. In addition, in the embodiment, an example is shown in which the workpiece 7 is rotated at a rotational speed that rotates the workpiece 7 at least one rotation before it reaches the target position, but as long as the workpiece 7 is rotating, the rotational speed can also be set to less than one rotation.

[0078] In addition, in the embodiment, an example in which the workpiece 7 is removed while being rotated is shown, but it is not necessary to combine a rotation operation when removing. However, for example, in a configuration in which the rotation range of the flange 2g is limited, if the flange 2g is rotated during the rotation insertion operation, the operation of removing the workpiece 7 and the operation of returning the flange 2g to its original rotation position can be performed simultaneously by removing the workpiece 7 while rotating it in the opposite direction to the rotation insertion operation, which can lead to a shortened inspection cycle. [Explanation of symbols]

[0079] In the drawings, 1 is an inspection system, 2 is a robot, 3 is a control device, 3a is a control unit, 3b is a judgment unit, 4 is a force sensor, 5 is a plug gauge, 5a is a small diameter portion, 5b is a large diameter portion, 7 is a workpiece, 10 is a hole portion, S3 is a searching process, S5 is a rotational insertion process, and S9 is a judgment process.

Claims

1. A method for controlling a robot that inspects a hole formed in a workpiece using a plug gauge, comprising the steps of: The robot moves the workpiece from the tip position of the plug gauge to a predetermined confirmation position, and holds the workpiece at a rotational speed that allows the workpiece to rotate at least one revolution from the confirmation position to a predetermined target position corresponding to the depth of the hole, and is provided with a force sensor on the hand side that detects the direction and magnitude of an external force applied to the hand, the plug gauge is fixed at a predetermined position within an operating range of the robot; a rotation insertion process in which the robot rotates the workpiece at the rotation speed and moves the workpiece in a direction in which the external force detected by the force sensor decreases while inserting the plug gauge into the hole; and a determination step of determining whether the hole is good or bad based on whether the workpiece has reached the target position with the plug gauge inserted in the hole.

2. 2. A robot control method as described in claim 1, further comprising a probing step of, when an external force is detected by the force sensor at a stage where the workpiece is moved to a contact position where the tip of the plug gauge is inserted into the hole, inserting the plug gauge into the hole while tilting the workpiece to the opposite side across the axis of the plug gauge from the position where the external force is detected by the force sensor, and moving the workpiece in a direction where the external force detected by the force sensor decreases.

3. 3. The robot control method according to claim 2, wherein the probing step is performed until the workpiece is moved from the tip position of the plug gauge to the confirmation position.

4. the plug gauge is provided at a tip end side with a small diameter portion for inspecting a minimum dimension of the hole, and is provided at a rear end side of the small diameter portion with a large diameter portion having a relatively large diameter for inspecting a maximum dimension of the hole, 4. The robot control method according to claim 1, wherein in the judging step, the quality of the hole is judged based on inspection results of both a minimum dimension and a maximum dimension of the hole.

5. A control device for a robot that inspects a hole formed in a workpiece using a plug gauge, the robot has a hand that moves the workpiece from the tip position of the plug gauge to a predetermined confirmation position, and holds the workpiece at a rotational speed that allows the workpiece to rotate at least one revolution from the confirmation position to a predetermined target position corresponding to the depth of the hole, and is provided with a force sensor that detects the direction and magnitude of an external force applied to the hand; the plug gauge is fixed at a predetermined position within a motion range of the robot; a control unit that controls the robot so as to perform a rotational insertion operation in which the workpiece having the hole formed therein is rotated at the rotational speed and the plug gauge is inserted into the hole while moving the workpiece in a direction in which the external force detected by the force sensor is reduced; and a determination unit that determines whether the hole is good or bad based on whether the workpiece reaches the target position with the plug gauge inserted in the hole; A robot control device comprising:

6. A plug gauge fixed at a predetermined position within the operating range of the robot; a robot that moves a workpiece having a hole formed therein from a tip position of the plug gauge to a predetermined confirmation position on a hand side, and holds the workpiece at a rotational speed that allows the workpiece to rotate at least one revolution from the confirmation position until the workpiece reaches a predetermined target position corresponding to the depth of the hole; a force sensor provided on the robot for detecting a direction and a magnitude of an external force applied to a hand of the robot; a control device including: a control unit that controls the robot to perform a rotational insertion operation in which the plug gauge is inserted into the hole while rotating the work at the rotational speed and moving the work in a direction in which the external force detected by the force sensor decreases; and a determination unit that determines whether the hole is pass or fail based on whether the work reaches the target position with the plug gauge inserted into the hole; An inspection system comprising:

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