JP4056662B2 - Appearance inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an appearance inspection apparatus that inspects the appearance of an inspection object using an imaging unit.
[0002]
[Prior art]
Conventionally, in order to inspect the appearance of a three-dimensional workpiece positioned on a jig at high speed, various methods for inspecting at high speed without stopping the robot by attaching a camera to the tip of the robot have been proposed. CP (continuous path) control has been proposed as an example of the method. In this CP control, an operation point for interpolation is set between predetermined inspection points, and control is performed so that the robot tip passes through an operation point including the inspection point. It is a working method. Therefore, the robot tip is controlled so that it passes through each operating point and assumes a predetermined posture at the timing when it is positioned at the operating point. Therefore, the workpiece is moved at the timing when the camera mounted on the robot tip is positioned at the predetermined inspection point. By picking up an image, the appearance of the workpiece can be inspected by the image processing apparatus.
[0003]
[Problems to be solved by the invention]
However, in such an appearance inspection apparatus, since the position and orientation of the camera for imaging the workpiece are fixed at the inspection point, it is necessary to position the workpiece at a predetermined position with a jig, which reduces the cost of the jig. In addition to being expensive, a conveyance cost for setting the jig at a predetermined position is also required.
[0004]
In this case, in order to reduce the cost of the appearance inspection apparatus, for example, the workpiece is placed in an arbitrary state where the workpiece is not positioned on the conveyor, the workpiece placed in the arbitrary posture is imaged by the camera, and the position and posture of the workpiece are It is conceivable to inspect the workpiece by correcting the movement path of the camera attached to the tip of the robot in accordance with the position and orientation of the workpiece by detecting the image with an image processing apparatus.
[0005]
However, in the above-described CP control, an operation point is automatically set between inspection points, and the posture of the camera is controlled simultaneously at the operation point. If the robot is operated at a predetermined speed, the robot tip may pass near the singular point. This singular point is a point that restricts the performance of the actuator that must move a specific axis of the robot at high speed. The trajectory of the robot tip changes from the set motion path, or the robot tip This causes a situation where the speed of the robot is reduced or the robot must be stopped.
[0006]
FIG. 7 shows an operation example of the two-axis robot, and each solid line shows an axis (manipulator). In FIG. 7, the shaft 2 is provided at the tip of the shaft 1, and the tip of the shaft 2 is set as the tip of the robot. When this robot tip is linearly moved from the operating point A to the operating point B, an axis at the operating point C (singular point) must be rotated at a high speed, and the robot cannot operate normally.
[0007]
By the way, when a workpiece is visually inspected at a plurality of inspection points at a high speed, it is sufficient that the inspection point to be inspected passes through the teaching position and teaching posture taught in advance by the robot tip, and the path between the inspection points is not a problem. Therefore, in order to realize high-speed inspection without stopping the robot while passing through an arbitrary route, it is necessary to use a PTP (point to point) control method in which the robot is operated using control for each axis level of the manipulator. desirable.
[0008]
FIG. 8 shows an operation example of the biaxial robot by PTP control in comparison with the CP control shown in FIG. As shown in FIG. 8, when the robot tip is moved from the operating point A to the operating point B, the trajectory of the robot tip does not become a straight line, but each axis moves with a smooth speed change, so that it can operate. is there.
[0009]
However, even in the PTP control, a problem when the robot is continuously operated is that the robot tip does not pass the inspection point taught in advance. That is, in order to continuously operate the robot, the operation time is shortened by overlapping the deceleration of one operation and the acceleration of the next operation. More specifically, when A, B, and C are set as operating points as shown in FIG. 9, they are not stopped at the operating point B as shown in FIG. 9, but at the operating point B as shown in FIG. Since deceleration and acceleration are executed at the same time, the locus of continuous movement from A → B → C does not pass through point B as shown by the solid line. When this is expressed as a robot movement path for the inspection of the entire workpiece, it becomes as shown in FIG. 11, and the inspection point at the time of inspection (indicated by a solid line) is different from the inspection point at the time of teaching (indicated by a broken line). Thus, the work 3 cannot be imaged correctly by the camera.
[0010]
The present invention has been made in view of the above circumstances, and its purpose is to examine the appearance of an inspection object using an imaging means, even if the position and orientation of the inspection object are arbitrary. An object of the present invention is to provide an appearance inspection apparatus capable of reliably inspecting an object at high speed.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, the robot tip is continuously moved at a high speed by overlapping the deceleration of a certain motion and the acceleration of the next motion without stopping the tip of the robot by PTP control. In the appearance inspection apparatus that inspects the inspection object with a large number of inspection points by the provided imaging means, after setting the numerous inspection points stored in the storage means as operating points when executing the PTP control, Without stopping the robot tip, a simulation operation is performed to obtain a passing point when continuously operating at high speed by overlapping deceleration of one motion and acceleration of the next motion. The passing position of the provided imaging means can be simulated in advance . The robot tip is inspected by the imaging means provided at the robot tip in a state where the robot tip is continuously operated at high speed by overlapping the deceleration of one motion and the acceleration of the next motion without stopping by the PTP control. By inspecting an object with a large number of inspection points, it is possible to perform high-speed imaging that shortens the operation time. However, as described above, the inspection points at the time of inspection differ from the inspection points at the time of teaching. However, as a result of the simulation operation, when the distance between the passing point and the inspection point exceeds a predetermined value, the position of the operating point is set on the side opposite to the direction of deviation of the passing point with respect to the inspection point. The simulation operation is set as a new correction operation point shifted by a deviation amount between the passing point and the inspection point, and all the distances between the passing point and the inspection point are predetermined values. As a result, the operating point when all the distances between the passing point and the inspection point are within a predetermined value is set as an operating point for actually executing the PTP control. By doing so, it is possible to control so that the motion trajectory of the robot tip passes through the multiple inspection points stored in the storage means.
[0018]
The conveyor 12 conveys the placed work (corresponding to an inspection object) 18. First and second fixing members 19 and 20 are erected at positions along the conveyor 12, and a position correction camera (corresponding to position correction imaging means) 15 is installed on the first fixing member 19. ing. The position correction camera 15 images the workpiece 18 conveyed by the conveyor 12 from above.
[0019]
A robot 13 is mounted on the second fixing member 20 downward and is positioned above the conveyor 12. The robot 13 includes a multi-axis manipulator 21, and the position and posture of the robot tip 13 a are controlled by operating the manipulator 21 by the robot controller 14. A shutter camera 16 is attached to the robot tip 13a, and the workpiece 18 conveyed by the conveyor 12 is imaged by the shutter camera 16. In this case, the position and posture of the shutter camera 16 can be controlled by controlling the robot tip 13a.
[0020]
The robot controller 14 controls the robot tip 13a by PTP control so that the teaching position and teaching posture taught in advance are obtained.
The image processing device 17 processes image signals from the shutter camera 16 and the position correction camera 15.
[0021]
FIG. 1 schematically shows the overall electrical configuration. In FIG. 1, the robot 13 drives a manipulator 21 by a servo motor 22 and detects the position of the manipulator 21 by an encoder 23.
[0022]
The robot controller 14 includes a main control unit (corresponding to control means) 24, a teaching point storage unit 25, an operation point correction unit (corresponding to operation point correction means) 26, a correction operation point storage unit 27, and an operation point coordinate conversion unit (operation). And an operating point order changing unit (corresponding to the operating point order changing means) 29.
[0023]
The teaching point storage unit 25 sequentially stores the position and posture of the robot tip 13a at the teaching point taught by a teach pendant (not shown).
The operating point correction unit 26 simulates the position and posture of the robot tip 13a when the robot 13 is continuously operated based on the position and posture at the teaching point, and the robot tip 13a is taught in the teaching position and teaching posture based on the simulation result. The position of the operating point is corrected so that
The corrected operation point storage unit 27 stores the corrected operation point corrected by the operation point correction unit 26.
[0024]
The operation point coordinate conversion unit 28 converts the position and orientation of the operation point stored in the correction operation point storage unit 27 into new coordinates based on the position and orientation of the workpiece 18 imaged by the position correction camera 15.
[0025]
The operation point order changing unit 29 sets the operation order of the operation points so that the operation disabled range is not included when the operation disabled range of the robot tip 13a is included in the locus where the robot tip 13a connects the operation points in the operation order. change.
[0026]
Then, the main control unit 24 controls the robot 13 so that the robot tip 13a is in the position and orientation converted by the operation point coordinate conversion unit 28 in the operation order of the operation points converted by the operation point order changing unit 29. .
[0027]
On the other hand, the image processing device 17 determines the position and orientation of the workpiece 18 based on the image captured by the position correction camera 15 and inspects the appearance of the workpiece 18 based on the image captured by the shutter camera 16. In this case, the imaging timing by the position correction camera 15 and the imaging timing by the shutter camera 16 are determined based on the detection result of a sensor (not shown).
[0028]
Next, the operation of the above configuration will be described.
FIG. 3 shows the operation of the robot controller 14. In FIG. 3, the robot controller 14 executes the inspection mode after executing the teaching mode.
[0029]
In the teaching mode, when the workpiece 18 put on the conveyor 12 is transported to a predetermined position by the conveyor 12, the workpiece 18 stops at the predetermined position. Therefore, the robot tip at a desired inspection point by the teach pendant in the stopped state. The robot controller 14 is taught the position and posture of 13a (shutter camera 16). Then, the robot controller 14 sequentially stores the position and orientation of the robot tip 13a at the taught inspection point in the teaching point storage unit 25 (S101).
[0030]
Subsequently, when the teaching of the position and orientation of the robot tip 13a at the desired inspection point is completed by the teach pendant, the robot controller 14 moves the robot tip 13a based on the position and orientation stored in the teaching point storage unit 25. The operation at the time of continuous operation is simulated (S102). This simulation is executed using a PTP (point to point) control method in which the robot tip 13a is operated using control for each axis level of the manipulator 21.
[0031]
Here, the robot controller 14 obtains a passing point when the robot tip 13a continuously operates at each taught inspection point, and calculates a deviation amount thereof. Here, the amount of deviation includes not only the amount of deviation of the position of the robot tip 13a but also the amount of deviation of posture.
[0032]
Specifically, if the position indicated by a circle shown in FIG. 4 is an inspection point taught by teaching, the shutter camera 16 needs to image the workpiece 18 in a predetermined posture at the position indicated by a circle. When the motion trajectory of the robot tip 13a when the robot tip 13a is continuously operated with the position of the circle marked as an operating point is simulated, it becomes as shown by a one-dot chain line in the figure, and does not pass the inspection point and is in the vicinity of the inspection point. It will pass the + sign. As described in the means for solving the problem, when the robot 13 continuously operates, the operation time is shortened by overlapping the deceleration of one operation and the acceleration of the next operation. Because.
[0033]
Here, the robot controller 14 calculates the amount of deviation between the ◯ mark and the + mark (S103), and corrects it by shifting the position of the operating point to the opposite side of the deviation direction by this deviation amount (S103). S104). As a result, the operating point shifts to the position indicated by Δ, and the position where the robot 13 continuously moves shifts accordingly, and the motion trajectory of the robot tip 13a moves from the one-dot chain line to the two-dot chain line. Pass the mark. In this case, when attention is paid to one operation point, the operation point can be corrected based on the amount of deviation between the operation point and the teaching point, but the previous and next operation points are also shifted due to the correction. If the distance between the passing point and the inspection point is not within the predetermined value ε (S103: NO), the simulation operation is executed again until the distance between the passing point and the inspection point is within the predetermined value ε. .
[0034]
When the distance between all the passing points obtained by the simulation and the corresponding inspection point is within the predetermined value ε (S103: YES), the robot controller 14 determines that the correction for the operating point has been completed. The corrected operating point is stored in the corrected operating point storage unit 27 (S105).
[0035]
When the correction of all inspection points is completed in the teaching mode as described above, the workpiece 18 is loaded into the conveyor 12 at an arbitrary position and posture (however, the bottom surface contacting the conveyor 12 is the same). Thereby, the work 18 is conveyed by the conveyor 12.
[0036]
At this time, the workpiece 18 is put on the conveyor 12 at an arbitrary position and posture, and the position and posture of the workpiece 18 are different from the teaching teaching the inspection point. When the position correction camera 15 is driven at the predetermined position, the position and orientation of the workpiece 18 are measured (S106).
[0037]
Based on the position and orientation of the workpiece 18 thus detected, the robot controller 14 performs coordinate conversion of the operating point generated during teaching (S107). That is, by converting the coordinate system based on the position and orientation of the workpiece 18 at teaching to a coordinate system based on the position and orientation of the workpiece 18 at inspection, the position of the robot tip 13a in each coordinate system at teaching and inspection and The posture is matched.
[0038]
When the work 18 conveyed by the conveyor 12 stops at a predetermined inspection position, the robot controller 14 controls the robot tip 13a by the PTP control method so as to pass the coordinate-converted operating point (S109). Thereby, the workpiece | work 18 can be test | inspected on the same test | inspection conditions as the time of teaching.
[0039]
By the way, the robot tip 13a can pass through the same inspection point as the teaching with respect to the workpiece 18 by converting the coordinates of the operating point at the time of the inspection in this way. In some cases, it may not be possible to operate with the same inspection order. That is, since each manipulator 21 has a unique rotatable angle, the rotatable angle of the robot tip 13a is a combination of the rotations of the manipulators 21, and there is an inoperable range where the robot tip 13a cannot operate. For this reason, depending on the order of the operating points, the robot tip 13a cannot be operated when the trajectory connecting the operating points is located within the inoperable range of the robot tip 13a.
[0040]
FIG. 5 shows inspection points for the workpiece 18 during teaching. In FIG. 5, since the operable range of the robot tip 13a with the shutter camera 16 facing the workpiece 18 is α to β, the robot controller 14 sets the inspection points in the inspection sequence to A → B → C → D. → E → F → G → H.
[0041]
Now, assuming that the workpiece 18 is positioned in the posture shown in FIG. 6 at the time of inspection, the inspection points A to H are positions shown in the drawing with respect to the workpiece 18. That is, the coordinates of the workpiece 18 have been rotated since the teaching. In this case, since the inoperable range of the robot tip 13a is the same as that at teaching, the movement locus of the inspection point E → F is located in the inoperable range, and the robot tip 13a moves between the inspection points E → F. I can't.
[0042]
Therefore, the robot controller 14 changes the movement trajectory of the inspection points in the inspection order to be in the range from α to β (S108). That is, the inspection order is changed from F → G → H → A → B → C → D → E to execute the inspection. As a result, the robot tip 13a does not move within the inoperable range, and the robot tip 13a can move the inspection points in order.
[0043]
According to such an embodiment, the position correction camera 15 detects the position and orientation of the workpiece 18, and the teaching position and teaching posture of the inspection point set by teaching are based on the position and orientation of the workpiece 18 at the time of inspection. Therefore, the workpiece 18 can be inspected at the time of inspection under the same inspection conditions as at the time of teaching. Therefore, the robot tip 13a can pass the inspection point as compared with the conventional example in which the robot does not pass the inspection point for the workpiece, so that the workpiece 18 can be reliably inspected.
[0044]
In this case, if the trajectory connecting the position-corrected operating point includes the inoperable range of the robot tip 13a, the operation order of the operating point is changed, so that the robot tip 13a can be reliably operated.
Moreover, since the workpiece | work 18 was conveyed by the conveyor 12, conveyance of the workpiece | work 18 can be automated and a conveyance cost can be reduced significantly.
[0045]
The present invention is not limited to the above embodiment, and can be modified or expanded as follows.
The shutter camera 16 mounted on the robot tip 13a itself may be used as the position correction imaging means for detecting the position and posture of the workpiece 18 put on the conveyor 12. In this case, when detecting the position and orientation of the workpiece 18, the shutter camera 16 needs to be held at a fixed position.
A SCARA robot may be used as the robot.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration according to an embodiment of the present invention. FIG. 2 is an overall perspective view. FIG. 3 is a flowchart showing the operation of a robot controller. FIG. 5 is a diagram showing the position and posture of the robot tip at the time of teaching. FIG. 6 is a diagram showing the position and posture of the robot tip at the time of inspection. FIG. 8 is a diagram showing changes in the position and posture of the robot tip by PTP control. FIG. 9 is a diagram showing changes in the robot speed when the robot is stopped at the operating point. FIG. Fig. 11 shows the change in robot speed when the robot is not stopped. Fig. 11 shows the position and orientation of the robot tip during teaching and inspection.
11 is an appearance inspection apparatus, 12 is a conveyor (conveying means), 13 is a robot, 13a is a robot tip, 14 is a robot controller, 15 is a position correcting camera (position correcting imaging means), and 16 is a shutter camera (imaging means). , 17 is an image processing apparatus (image processing means), 18 is a workpiece (inspection object), 24 is a main control section (control means), 26 is an operating point correcting section (operating point correcting means), and 28 is operating point coordinate conversion. Reference numeral (operation point coordinate conversion means) 29 denotes an operation point order change section (operation point order change means).

Claims (1)

An object to be inspected by the imaging means provided at the tip of the robot in a state where the robot tip is continuously operated at high speed by overlapping deceleration of a certain motion and acceleration of the next motion without stopping by the PTP control. Is an appearance inspection device that inspects at a number of inspection points ,
Storage means for storing the position of the robot tip at a number of inspection points taught by an operator;
After setting the plurality of inspection points stored in the storage means as operating points when executing the PTP control, without stopping the tip of the robot , a certain operation is decelerated and the next operation is accelerated. When a simulation operation is performed to obtain a passing point when continuously operating at high speed by overlapping, and as a result of the simulation operation, the distance between the passing point and the inspection point exceeds a predetermined value Is set as a new operation point for correction by shifting the position of the operation point by the amount of deviation between the passing point and the inspection point on the opposite side to the direction of deviation of the passing point with respect to the inspection point. Simulation means for repeating the simulation operation until all distances between the passing point and the inspection point are within a predetermined value;
As a result of the simulation by the simulation means, the operating point when all the distances between the passing point and the inspection point are within a predetermined value is set as an operating point for actually executing the PTP control. Control means for controlling the movement trajectory of the robot tip to pass through the plurality of inspection points stored in the storage means;
An appearance inspection apparatus comprising: an image processing unit that inspects the inspection object by imaging the inspection object by the imaging unit at a timing when the robot tip passes an operating point.

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