JPH05293725A - Assembling system for free bearing table - Google Patents

Abstract

PURPOSE:To provide an assembling system suitable for efficiently assembling a table with free bearing. CONSTITUTION:This system is provided with a robot hand 3 for sucking free bearings one by one and transferring them to a position with a predetermined offset against an assembling position on a table face, an image processing device 9 for taking a picture of the assembling position on the table face at this position and calculating a difference between this position and a desired position, and a robot controller 7 for driving the robot hand 3 with referring to a correction amount calculated by this device. A control computer is provided for driving a screwing device 4 provided at the hand 3, free bearings are assembled to the predetermined assembling position and carrying out repeated assembling work for a large number of free bearings while inspecting the screwed state of the screwing device 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly system for efficiently assembling a free bearing table having a large number of free bearings on its surface.

[0002]

2. Description of the Related Art As fixed or movable tables used in various processing machines, those with free bearings are often used. This is one in which various works can be arbitrarily moved on a ball of a bearing having no drive mechanism, and generally, a large number of free bearings are fixed in a lattice on a table surface.

Conventionally, this type of table with free bearings (free bearing table) has been assembled by manually fixing one free bearing to each free bearing assembly position on the table surface with screws.

Further, in order to save labor, some parts are assembled using a robot.

[0005]

However, in the conventional assembly work of the free bearing table by the robot, the positioning is performed at the preassembled teaching position, the parts are assembled and the bolts are tightened, and then the bolt tightening torque is confirmed. It was not possible to assemble because the bolt did not enter if the assembly position was misaligned or if the bolt was too tight, it could not be detected that the assembly was not completed. There was a problem that defects were generated.

In view of this, the present invention provides a free bearing table that enables accurate assembly by accurately detecting the assembly position, and can detect an assembly failure on the spot by integrally providing a screw tightening state inspection device. It is an object of the present invention to provide an assembly system of.

[0007]

In order to solve the above problems, the present invention provides an assembly system for a free bearing table as set forth in the claims.

[0008]

Since the assembly system of the free bearing table of the present invention has the above-mentioned configuration, the screw tightening work can be performed smoothly without any displacement in the assembly position, and the screw tightened state after the screw tightening is completed on the spot. It is efficient because it is inspected.

The screw tightening inspection may be made, for example, by judging that the tightening torque is a certain value or more, the tightening time is within a certain value, and the tightening stroke is a certain amount. In this case, if the screw is tightened until a certain torque is output, it can be known that the screw part has been screwed in because a certain stroke has been obtained, and it must be conditioned that it has been screwed in within a certain time. Therefore, it is possible to comprehensively determine that the screw member itself has no abnormality and that an unexpected accident has not occurred.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an explanatory view showing the outline of an assembly system according to an embodiment of the present invention.

As shown in the figure, the body 1 of the robot R / B is provided with a hand 3 via an articulated arm 2, and the hand 3 has a screw tightening device 4 as an assembly tool and a CCD.
An image pickup device including a camera 5 and a lighting fixture 6 is fixed.

A robot controller 7 for controlling the robot R / B and the screw tightening device 4 is connected to a management computer 8 for controlling the operation timing of connecting members. The management computer 8 is connected to an image processing device 9 which is connected to an image pickup device.

2 and 3 are a front view and a side view showing the details of the hand 3 having the screw tightening device 4 and the image pickup device (5, 6). However, in the front view of FIG. 2, the image pickup device is removed.

In FIG. 2, the hand 3 is provided with a pair of screw tightening devices 4 as an assembly tool.

In the assembling work in this example, as shown in the lower part of FIG. 2, it is assumed that the free bearing W2 is assembled from the back surface of the table W1. This free bearing W2
Has a pair of through holes in an elliptical plate having a bearing ball housed in the center thereof, and bolts are inserted into the through holes for assembly. Use these bolts for the corresponding screw holes (nut holes) H1, H2 of the table W1.
It is the role of the screw tightening device 4 to be screwed into.

The screw tightening device 4 comprises a nut runner body 10
A nut runner socket 11 that moves up and down with respect to the hand 3, a spring 13 that constantly urges the nut runner body 10 downward, and a wrench 14 that rotates as the socket 11 rotates. Be prepared.

A sensor mounting plate 16 is provided on the bracket 15 fixedly provided to the nut runner body 10, and the upper end position of the nut runner socket 11 is fixed to the sensor mounting plate 16 at a tightening start position and a tightening end position. Proximity switch 17 for stroke detection which detects at two positions is provided.

A vacuum pad 18 is provided at an intermediate portion of both nut runner sockets 11 so that its lower surface is substantially aligned with the lower surface of the wrench 14, and a vacuum generator 19 provided on the upper portion of the hand 3 is located on the lower surface thereof. The free bearing W2 can be adsorbed. Each nut runner main body 10 is provided with a limit switch 20 for torque detection that is turned on at a certain torque or more.

Therefore, according to the hand portion of this example, the hand 3 is moved with respect to the free bearing W2 located at the height of the level L1, and then the hand 3 is resisted against the spring 13.
By lowering and adsorbing the free bearing W2 by the vacuum pad 18, the free bearing W2 can be fixed to the tip of the hand 3 in the state shown on the right side of FIG.

After that, the hand 3 is moved to perform a position correcting operation described later, and then the free bearing W2 is moved to the assembly position of the table W1 and is appropriately lowered to screw the bolt 21 of the free bearing W2 into the screw hole H1. , H2 can be screwed in to rotate the wrench 14. When the wrench 14 is rotated, the bolts 21 are screw holes H1 and H2.
The nut runner socket 11 is lowered with respect to the nut runner body 10. After tightening the bolt 21,
The hand 3 may be moved for the next work from the state shown in the left half.

As shown in FIG. 3, in front of the hand 3 (on the right side in the figure), a CCD camera 5 having a lens portion 22 is provided below the hand. CCD camera 5
A pair of lighting fixtures 6 are provided on both side surfaces of the. The mounting interval of the lighting fixture 6 is substantially the same as the interval between the screw holes H1 and H2 of the table W1.

The camera 5 is operated when the free bearing W2 is moved to the assembly position of the table W1 after the free bearing W2 is adsorbed by the vacuum pad 18 by the hand portion of FIG. The hand 3 moves the camera 5 to a position above the assembly position of the table W1, illuminates the screw holes H1 and H2 at this position, and images the table W1 including the screw holes H1 and H2.
As will be described later in detail, the image processing device 9 compares the image pickup position with a predetermined position, calculates the deviation of the work position of the table W1 with respect to the hand 3, calculates a correction amount, and outputs the correction amount to the robot controller 7. It outputs and causes the robot R / B to perform a position correction operation.

FIG. 4 shows the system configuration shown in FIG.
In particular, it is a block diagram showing details of the image processing apparatus 9.

As shown in the figure, the image processing apparatus 9 includes a communication unit 23 connected to the management computer 8 and a camera 5.
And an image pickup command signal output unit 24 and an image pickup signal input unit 25 connected to the image pickup apparatuses 5 and 6 including the illumination device 6, and a central processing unit 26 and an image processing unit 27 connected to these. The image processing unit 27 includes a binarization level adjusting unit 2
8 and the robot correction amount calculation unit 29 are connected.

The image processing unit 27 processes the image including the screw holes H1 and H2 at the assembly position taken in the frame memory and performs numerical analysis. Binarization level adjustment unit 2
Reference numeral 8 optimizes the binarization level when the shape of the image processing unit 27 is recognized. The robot correction amount calculation unit 29
According to the numerical analysis result of the image processing unit 27, the robot R / B
Is obtained.

FIG. 5 is a block diagram showing the configuration of the robot controller 7.

In the figure, the robot controller 7 is
A data communication unit 30 for data communication with the management computer 8 and a central processing unit 31 connected to the communication unit 30 are provided. The central processing unit 31 is a robot R / B.
It is the core of a so-called NC device for numerically controlling.

The system bus 32 connected to the central processing unit 31 has various servo motors M _{i for the} robot R / B.
And a motor drive unit 33 for driving other actuators, for example, an actuator drive unit 34 for driving a nut runner and a vacuum generator 19 incorporated in the screw tightening device 4.
And a sensor signal input unit 35 for inputting various sensor signals, for example, detection signals of the stroke detection proximity switch 17 and the torque detection limit switch 20, and an inspection unit 3.
6 and the clock 37 are connected. The inspection unit 36 is for inspecting the screw tightened state on the spot after the screw tightening is completed.

In the robot controller 7 having the above structure, the central processing unit 31 moves the robot R / B to a predetermined target position via the motor drive unit 33, drives the nut runner of the screw tightening device 4, and then performs inspection. The screw tightened state is inspected at the portion 36, and the screw tightening is sequentially performed, and the assembling work is performed.

FIG. 6 is a flow chart showing the overall flow of the assembly work.

In step 601, the conditions of the work contents are set, and in step 602, the robot R / R is reached to the assembly position after the free bearing W2 is adsorbed by the vacuum pad 18.
B is moved and the camera 5 is positioned directly above the center positions of the screw holes H1 and H2, and in step 603, the screw holes H1 and H2 of the table W1 as the assembly position are imaged.
In step 604, the robot R / B is corrected and
The screw tightening work is executed in step 605, and step 6
Check the screw tightening condition at 06. If the screw is not properly tightened, alarm processing is performed in step 608.

FIG. 7 shows the camera 5 and the table W1 at the time of image pickup.
Shows the correspondence relationship of. In the figure, the component mounting hole H3 is a screw hole H
1 and H2, which are holes provided in the central portion of the free bearing W2. Normal robot R / B
Is moved with respect to the center position P3 (not shown) of the hole H3 and defines the mounting direction of the free bearing W2 with a straight line passing through the center positions P1 and P2 (not shown) of the holes H1 and H2.

FIG. 8 is an explanatory diagram showing an image picked up on the plane coordinates (XY) of the frame memory FM of the image processing unit 27. As shown in the figure, when a black-and-white pixel is determined and its shape is recognized at a certain binarization level, circles H1'H2'H3 'appear corresponding to the screw holes H1, H2 and the mounting hole H3. The center position of each shape is defined as P1 ', P2', P3 '.

Here, the shapes H1 ', H2', shown in FIG.
H3 'may be distorted and recognized due to illumination, the properties of the screws in the screw holes H1 and H2, the state of the fracture surface of the mounting hole, or the like. Therefore, the shapes H1 ', H2', H3 'recognized at a certain binarization level
Therefore, if the positions of the holes H1, H2, H3 are recognized as they are, a recognition error may occur, a large error may occur in a correction value calculated later, a mounting failure may occur, and a defective product may be generated.

Therefore, in this example, the binarization level is adjusted and the shapes H1 ', H2', H3 'are adjusted by the procedure shown in FIG.
Is properly recognized and the correction amount to be output to the robot R / B is calculated.

First, when an image is picked up in step 901, in step 902, the screw hole shapes H1 'and H2 are obtained.
For ', the difference ΔSi between the measured area Si (i = 1, 2) and the reference area Sio is obtained.

ΔSi = Si-Sio Then, in steps 903 and 904, it is determined whether or not this difference ΔSi is less than or equal to the allowable value ΔSio, and if it is greater than or equal to the allowable value, the direction (positive or negative) is determined. To do.

If the difference ΔSi is within the allowable value, step 90
If the difference ΔSi is out of the allowable value, the process proceeds to step 906 or step 907, and the binarization level (brightness) is set as shown in FIG. Decrease or increase by ΔL, step 902
Return to.

Therefore, in this example, each shape H1 ', H
Since the binarization level is adjusted so that the area of 2 ′ becomes the Si reference value Sio, the regular shape H is obtained from the binarized image obtained according to the level change shown in FIG. 10 as shown in FIG.
1 ', H2' are obtained.

Therefore, in this example, in step 905, the central coordinates P1 '(X1, Y1), P2' of the screw holes H1, H2 are set.
(X2, Y2) is calculated, and its center coordinate P3 '(X3,
Y3) X3 = (X1 + X2) / 2 Y3 = (Y1 + Y2) / 2 is determined as the center coordinate of the mounting hole H3, and the screw hole center coordinate P is calculated.
A straight line m connecting 1 and P2 is obtained, and a correction amount is calculated in step 906.

The correction amount is calculated by the difference ΔP3 between the center coordinate P3 'of the mounting hole H3 and the regular value, and the deviation angle ΔA of the straight line m from the regular straight line. The correction amount thus calculated is transferred via the management computer 8 to the robot controller 7
The robot R / B obtains the moving position and the rotation angle in consideration of the correction amount, rotates the wrench 14 in the relationship shown in FIGS. 6 and 4, and performs the screw tightening work.

When tightening the screw, torque is detected, and the proximity switch 17 for stroke detection is used for the wrench 1.
After the stroke amount of 4 is detected and it is confirmed that the screw is securely tightened, the next operation is performed. If an alarm is generated, the contents of the generated alarm are stored, the operation at that time is interrupted, and the assembly operation for the next free bearing W2 is continued. The alarm occurrence probability is a small value, for example, several thousandths or less.

FIG. 12 is a flow chart showing a screw tightening method performed by the actuator drive section 34 and the inspection section 36.

In step 1201, the upper proximity switch 17
When the screw tightening start position is confirmed by the off operation of (LS1), the process proceeds to step 1202, and the nut runner of the screw tightening device 4 is driven until it is confirmed in step 1203 that the drive torque T has reached the predetermined value To. . However, an upper limit is set for the drive time, and if the drive torque does not increase at any time, the drive is stopped after the set time has elapsed. In this example, the drive torque T
Limit switch 20 when is above a certain torque To
Is configured to turn on, so step 1203
Then, actually, it depends on whether the limit switch 20 is turned on.

When the screw tightening device 4 is stopped in step 1204, the driving time t is set to a constant value to in step 1205.
It is determined whether or not it is within the range, and at step 1206, the screw tightening end position is determined by the ON operation of the lower proximity switch 17 (LS2).
If yes, then step 1
The process shifts to 207, and the non-defective process, that is, the next screw tightening work is performed.

On the other hand, if the determination is NO in step 1205 or 1206, the process proceeds to step 1208, and the defect processing, that is, this state is stored and the next screw tightening operation is performed. The state memory here is the place,
The cause of the failure (time over or stroke shortage).

As described above, in this example, the bolt 21 as a screw member adsorbed by the vacuum pad 18 can be screwed with a constant torque by driving the nut runner.
With the timepiece 37 and the position detection by the limit switch or the like, it is possible to reliably determine the tightening state by detecting that the tightening is completed within a certain time and the predetermined stroke is obtained.

If the screw is tightened until a constant torque is generated, it is possible to know that the screw portion is screwed in by the constant stroke being obtained, and it is necessary that the screw is screwed in within a constant time. It is possible to comprehensively determine that there is no abnormality in the screw member itself or that an unexpected accident has not occurred.

Assuming the cause of screw tightening failure, the screw does not fit. Foreign matter is attached to the screw. Misalignment and other unexpected factors may be considered. It can be determined by not having it. The factor can be determined by the fact that the stroke does not occur even when a constant torque is applied.
Similarly to, the factor of can be determined by the fact that torque or stroke is not produced. The factor (1) can be discriminated almost 100% within the fixed time after the constant torque is applied and the condition that the constant stroke can be obtained.

Further, in the present example, for a defect that rarely occurs, the defective portion and the contents are stored in this way and the process proceeds to the next process, so that there is no delay in the assembly work due to the occurrence of the defect. For defective parts, only that part should be repaired later.

As described above, according to the assembly system of the free bearing table of the present example, the pair of bolts 21 are used for the assembly work of the free bearing W2 on the surface of the table W1.
Can be simultaneously attached to the pair of screw holes H1 and H2.

The assembly procedure is as follows. The free bearing W1 is sucked by the vacuum pad 18 and then the wrench 14 is rotated.
Since 1 is simply slid onto the nut runner main body 10, the device configuration is simple and the control procedure of the robot R / B is easy.

Further, in this example, the image processing device 9 is provided, and after imaging the screw holes H1 and H2 of the table W1,
A pair of bolts 2 for the pair of holes H1 and H2 that are imaged
Since 1 is screwed in, there is less risk of installation failure and the chance of alarm occurrence is reduced. Further, particularly, the binarization level adjusting unit 2
8 adjusts the binarization level so that the area Si becomes the regular area Sio by the method shown in FIGS.
Even if the images of the screw holes H1 and H2 are slightly disturbed, the normal center position can be accurately obtained, and highly accurate assembly work can be performed.

The present invention is not limited to the above embodiments, but can be carried out in appropriate modes by making appropriate design changes.

[0056]

As described above, since the present invention is the assembly system of the free bearing table as set forth in the claims, it is possible to perform the screw tightening work smoothly without any displacement in the assembly position, and to perform the screw tightening. It is efficient because the screw tightening state after the completion is inspected on the spot.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an assembly system according to an embodiment of the present invention.

FIG. 2 is a front view showing a state in which the screw tightening device is integrally attached to the robot hand.

FIG. 3 is a side view of the screw tightening device.

FIG. 4 is a block diagram showing a configuration of a control system for an assembly robot.

FIG. 5 is a block diagram showing details of a robot controller.

FIG. 6 is a flowchart showing an assembly method of the robot.

FIG. 7 is an explanatory diagram showing an arrangement relationship between an imaging position and an assembly position.

FIG. 8 is an explanatory diagram of an image.

FIG. 9 is a flowchart showing an image processing method.

FIG. 10 is an explanatory diagram of an image signal (video signal) along the X axis.

11 is an explanatory diagram of a signal obtained by binarizing the video signal of FIG.

FIG. 12 is a flowchart showing a screw tightening method.

[Explanation of symbols]

 3 Robot hand 4 Screw tightening device 17 Proximity switch for stroke detection 20 Limit switch for torque detection 36 Inspection section W1 table W2 Free bearing H1, H2 Screw holes

Claims (1)

[Claims] 1. An assembly system for assembling a free bearing table by sequentially screwing a number of free bearings to a table surface, wherein the free bearings are sucked one by one, and the sucked free bearings are assembled on the table surface. A robot hand that transfers to a position where a predetermined offset is given is provided, and an image of the assembly position on the table surface is imaged at this position, the deviation between this position and the planned position is calculated, and the result is given to the robot hand. An image processing device for calculating a correction amount for the robot hand is provided, the robot hand is driven by referring to the correction amount calculated by the device, and the robot controller for adjusting the free bearing to the assembly position is provided. By driving the screw tightening device provided, the free bearing is assembled in a predetermined assembly position. Together assembled in the while checking the screw fastening state of the screw tightening devices, the free bearing table assembly system, characterized in that a management computer to execute the repetitive assembling work for a number of free bearings.