JP2012139776A - Work quality determination system and quality determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an increase of a size near a holding part of a work and an increase of the number of cables in a machine device of a robot 1 etc. and to prevent failures of a sensor or the like.SOLUTION: The machine device of the robot 1 etc. is provided with the holding part (for example, a chuck 8) of the work and a movable part (for example, a compliance device 7) between the holding part and its supporting part (for example, a wrist 6) to determine quality from changes in positions of the holding part and the supporting part accompanied by a task. For example, markers M are installed at both the holding part side and the supporting part side of the movable part to detect the positions of the markers in an image taken by a camera 11 by image processing and determine the quality of the task from changes in the distance between the holding part and the supporting part.

Description

  The present invention relates to determination of quality of work in which a workpiece is processed and assembled by a machine device such as a machine tool or a robot.

  Conventionally, industrial robots and automatic assembly machines have been used to automate the process of assembling a workpiece into a product at the production site. In order to detect the position of the workpiece and the position of the product to be assembled, the workpiece is also a product. Various sensors are used to determine whether or not they are properly assembled.

  For example, in the automatic screw tightening machine described in Patent Document 1, a displacement sensor is provided in the vicinity of the chuck unit through which the driver bit is inserted, and the screw tightening is completed according to the detected distance from the detected object. It comes to detect. In addition, in the automatic screw tightening machine described in Patent Document 2, a torque sensor is built in an electric driver disposed in the vicinity of a screw tightening bit, whereby the tightening torque of the screw can be detected.

JP 2000-343347 A JP 2004-306161 A

  However, in the above-described conventional example, the displacement sensor and the torque sensor are disposed in the vicinity of the part for holding the work such as the driver bit and the screw in the mechanical device. There is a difficulty in increasing the number of cables. In general, vibrations and shocks associated with work are likely to be applied in the vicinity of the work holding part, which may cause a failure of a sensor that is a precision instrument.

  In view of this point, the object of the present invention is to devise a method for detecting the state of work performed by a robot, an automatic assembly machine, etc., and to increase the size of the work holding portion in the vicinity of the work and increase the number of cables. Is to prevent sensor failure.

  The present invention for achieving the above object is a system for judging the quality of work performed by a mechanical device, and between the workpiece holding portion and the support portion supporting the workpiece in the mechanical device, A movable part is provided so as to be relatively displaced by the force received from the work during work. And it is detected by the non-contact-type position detection apparatus which can detect the position of each of this holding part and a support part apart from both the said holding part and a support part, and the said work at the time of the said operation | work. And a pass / fail judgment means for judging pass / fail of the work from the relative positional relationship between the holding part and the support part.

  In such a system, a movable part is provided between a work holding part and a support part that supports the work holding part in the mechanical device, and the holding part and the support part are relatively displaced by a force received from the work during work. To do. As an example, when a workpiece, which is a part, is inserted into a predetermined position of a product, if a large force is applied to the workpiece due to a variation in dimensions or a deviation in the assembly position, the relative displacement between the holding portion and the support portion increases accordingly. Become. Therefore, the work state can be detected from the relative positional relationship between the holding unit and the support unit detected by the position detection device, and the quality of the work can be determined based on this.

  In addition, in order to detect the state of work by the relative displacement between the holding portion and the support portion generated in the movable portion as described above, the movable portion has an appropriate elastic force and damping force with respect to the relative displacement of both portions. You may make it add. For example, when an elastic body is interposed between the holding part and the support part, the magnitude of the force acting between the holding part and the support part detected by the position detection device during work is obtained. Therefore, the quality of the work can also be determined based on this.

  And since the position detecting device is separated from both the holding portion and the supporting portion, unlike the conventional case in which a sensor or the like is disposed in the vicinity of the work holding portion, the periphery of the work holding portion of the mechanical device However, there will be no increase in size or the number of cables. In addition, there is no fear that the position detection device will break down due to vibrations and shocks associated with work.

  In order to accurately detect the position of the work holding unit or the support unit from such a remote location, various known non-contact type position detection devices can be used, but as an example, an imaging device such as a camera Thus, an image processing apparatus that detects the position of the object in the captured image may be used. In this case, the shape, color, surface state, lighting method, etc. may be devised so that the movable part can be easily identified by image processing, but a suitable marker corresponding to the algorithm of the image processing calculation is used. You may provide in each member of the holding | maintenance part side and support part side of a movable part.

  In this way, the imaging device is arranged so that the marker can be photographed, and it becomes easy to detect the position of the marker in the image obtained by photographing by image processing calculation. In addition, it is not necessary to provide a marker for each workpiece, and it is only necessary to provide a marker on the movable part of the mechanical device, so that the cost increase is small.

  More specifically, the distance between the two members is obtained from the respective marker positions of the holding part side and support part side members detected immediately before the start of the work, and the two members detected after the start of the work. The interval between the two members may be obtained from the respective marker positions, and the quality may be determined from the change in the interval between the two members accompanying the work. For example, in the case of screw tightening work, just before the start, the screw may be pressed against the screw hole so that the movable part is contracted to some extent. As it enters the hole, the holding part side member descends and the distance from the support part side member increases.

  In this case, preferably, the quality of the work is determined by comparing the ratio between the distance between the two members obtained immediately before the start of the work and the distance between the two members obtained after the work is started with a preset threshold value. You may do it. In this way, it is possible to accurately detect the distance between the holding unit side and the support unit side member regardless of the distance between the place where the work is performed and the installation location of the imaging device. Further, it is not necessary to perform precise calibration for positioning the coordinate system of the captured image at the actual space coordinates every time the image pickup apparatus is replaced or the position is changed.

  In addition, in order to shorten the time required for the image processing calculation as much as possible, the marker position is detected after the start of the work based on the marker positions on the holding part side and the support part side detected immediately before the start of the work as described above. The range of the image processing calculation for this purpose may be narrowed down. In other words, since the direction in which the marker moves in accordance with the work is usually known in the captured image, the range of the image processing calculation is set in an elongated area extending in the moving direction of the marker from the marker position first detected in the image. Just squeeze it.

  Alternatively, or in addition thereto, the range of image processing calculation for detecting the marker position may be narrowed down based on control data of the mechanical device such as robot teaching data. In this way, the time required for the image processing calculation at the time of marker position detection before the start of work can be shortened.

  Further, at least one of an imaging device and an image processing device may be provided as the position detection device. In this way, acquisition of an image including the marker and image processing calculation can be performed in parallel so that at least a part of the image proceeds simultaneously, which also contributes to shortening the processing time.

  By the way, when a screw or bolt as a work is tightened into a product as an example, the work is rotated together with the holding part. In this case, the holding part side of the movable part is used. In addition, each of the members on the support part side may be a disk-shaped member orthogonal to the rotation center line of the workpiece, and the marker may be provided on the outer periphery of the disk-shaped member. In this way, the distance between the marker and the imaging device does not change even if a part of the work holding part, the movable part, and the support part rotates, so that the position can be detected continuously during work or at an arbitrary timing. Yes.

  If an operation that does not include a rotation operation is performed, one marker may be provided on each of the holding unit side and the support unit side member of the movable unit so as to be positioned in front of the imaging device during the operation. . Further, when the work is performed at two or more locations within the field of view of one imaging device, the holding unit side and the support unit are provided so that the marker is positioned in front of the imaging device corresponding to each work location. A plurality of markers may be provided on each of the side members.

  Moreover, specifically about the structure of the said movable part, a guide shaft is provided so that it may extend between the holding | maintenance part side member and support part side member of a workpiece | work, One of both members may be penetrated, The said one member May be movably supported so as to be close to / separated from the other member, and a spring member may be interposed between the two members so as to apply a biasing force so as to be separated from each other. If it carries out like this, the member of the said holding | maintenance part side and the support part side will come to move relatively in the direction where a guide shaft is extended, and it is preferable when detecting the quality of work from the space | interval of both members.

  In other words, the present invention is a method for determining the quality of work performed by a mechanical device, and between the work holding portion and the support portion supporting the work in the mechanical device, A movable part is provided so as to be relatively displaced by the force received from the workpiece, and at a place away from both the holding part and the supporting part during the work, the non-contact type position detection device is used to detect the holding part and the supporting part. The relative positional relationship is detected to determine whether the work is good or bad.

  In this case, as described above, a marker is provided on each of the members on the holding unit side and the support unit side of the movable unit, and an imaging device is arranged so that the marker can be photographed, and the marker in an image photographed by the imaging device This position may be detected by image processing, and a change in the interval between the members on the holding part side and the support part side accompanying the work may be obtained from the detected marker position to determine whether the work is good or bad.

  In addition, an elastic body is interposed between the members on the holding portion side and the support portion side of the movable portion so as to be elastically deformed by the force received from the work during the work, and the holding portion side detected during the work And the magnitude | size of the force which acts between both may be calculated | required from the space | interval of the member by the side of a support part, and you may make it determine the quality of work.

  As described above, according to the present invention, it is possible to determine the quality of work without disposing a precision device such as a sensor in the vicinity of a work holding portion of a mechanical device such as a robot or an automatic assembly machine. It is possible to avoid an increase in size in the vicinity of the work holding portion and an increase in the number of cables, and it is possible to prevent the sensor from being broken.

It is a perspective view which shows an example of the robot which applies the quality determination system of the operation | work which concerns on this invention. It is an enlarged view of the compliance apparatus with which a robot arm is equipped. It is a schematic block diagram of a quality determination system. It is a flowchart figure which shows the procedure of the quality determination of work. It is explanatory drawing of the insertion operation | work of a pin, (a) shows the state just before the start of insertion operation, (b) shows the state where insertion was successful, (c) shows the state which failed in insertion, respectively. FIG. 5 is a diagram corresponding to FIG. 5 relating to the bolt tightening operation, where (a) shows the state immediately before the start of the screw tightening operation, (b) shows the state where the screw tightening is successful, and (c) shows the state where the screw tightening fails. Each one is shown. It is the FIG. 2 equivalent view which concerns on other embodiment of the compliance apparatus which made the bracket the disk shape.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a robot as a mechanical device to which a work quality determination system according to the present invention is applied. FIG. 2 is an enlarged view of a compliance device attached to an arm of the robot 1. ing. The robot 1 is used, for example, in an operation of assembling various workpieces on a product or an assembly (semi-finished product) in the middle of manufacture in an assembly line of a factory.

-Robot configuration example-
The robot 1 shown in FIG. 1 is a so-called multi-joint type, a fixed portion 2 fixed to a floor or the like, a base portion 3 capable of turning (shown by an arrow A) around a vertical axis a at the upper portion thereof, First and second arm portions 4 and 5 are sequentially attached to the upper portion of the base portion 3. A wrist portion 6 is attached to the distal end portion 5 a of the second arm portion 5, and a chuck 8 is attached to the wrist portion 6 via a compliance device 7.

  That is, a pair of left and right support wall portions 3a is provided on the upper portion of the base portion 3, and the base end portion of the first arm portion 4 is supported so as to be rotatable around the horizontal axis b while being sandwiched between them. Has been. Thereby, the first arm portion 4 can be tilted up and down as indicated by an arrow B. The first arm portion 4 is composed of a pair of plate-like members extending from the left and right sides of the base end portion, and supports the base end portion of the second arm portion 5 so as to be rotatable about the axis c therebetween. . As a result, the second arm portion 5 can also be tilted in the vertical direction (arrow C).

  A bifurcated tip portion 5a is provided at the tip of the second arm portion 5 so as to be rotatable (arrow D) around an axis d in the longitudinal direction, and a columnar wrist portion 6 is interposed therebetween. It is supported so as to be rotatable (arrow E) around the axis e. A chuck 8 is attached via a compliance device 7 to the tip of the wrist 6, that is, the end closer to the left front in the figure. The chuck 8 can be rotated (arrow F) around the axis f by the operation of an electric motor built in the wrist 6 together with the compliance device 7, for example.

  In FIG. 1, reference numeral 9 denotes a work that is held by the chuck 8, and as an example, shows a pin that is inserted into an insertion hole 10 a that opens on the upper surface of the product 10. In the example shown in the drawing, the peripheral edge of the insertion hole 10a is enlarged in a taper shape so as to guide the pin 9 to be inserted.

-Compliance device-
In the present embodiment, a compliance device 7 (movable part) is interposed between the chuck 8 (holding part) and the wrist part 6 (supporting part) of the robot 1 to insert a pin 9 and a bolt 15 (see FIG. 6). ) Is tightened by receiving a force applied due to misalignment or the like, and absorbs an impact. In particular, during the screw tightening operation, the bolt 15 is pushed out as it is rotated as will be described later, thereby contributing to the simplification of the control of the robot 1.

  As shown in FIG. 2 in an enlarged manner, the compliance device 7 of the present embodiment includes a bracket 70 (positioned downward in the drawing, hereinafter referred to as a lower bracket) as a member on the chuck 8 side, and a wrist 6 of the robot arm. And a bracket 71 (positioned upward in the figure, hereinafter referred to as an upper bracket). In the illustrated example, both brackets 70 and 71 are substantially triangular plate members, and round holes 70a and 71a are opened in the center. A cable or the like for supplying electric power to the motor of the chuck 8 is inserted into the round holes 70a and 71a.

  In the illustrated example, the central circular hole 70a of the lower bracket 70 has a larger diameter than the circular hole 71a of the upper bracket 71, and a plurality of bolt holes 70b (four in the illustrated example) are formed so as to surround the circular hole 70a. Has been. Although not shown, the chuck 8 is fastened to the lower portion of the lower bracket 70 by bolts inserted into these bolt holes 70b. Similarly, a plurality of bolt holes 71 b are formed in the upper bracket 71 so as to surround the central circular hole 71 a, and some of them have bolts for fastening the upper bracket 71 to the wrist 6 of the robot 1. Inserted.

  The brackets 70 and 71 are connected to each other by three guide shafts 72 provided therebetween. Each guide shaft 72 has an upper end fixed to the upper bracket 71, and a lower end penetrating the lower bracket 70 to support the lower bracket 70 so as to be slidable up and down. In addition, a coil spring 73 (elastic body) is extrapolated to each guide shaft 72, and a pressing biasing force is applied to both the brackets 70 and 71 so as to be separated vertically. The coil spring 73 is elastically deformed by the force received during the operation, and the relative displacement of the upper and lower brackets 70 and 71 is allowed.

  The upper and lower brackets 70, 71 are formed with three through holes 70c, 71c at equal intervals in the circumferential direction surrounding the central circular holes 71a, 70a so as to correspond to the tops of the triangles. The end of the guide shaft 72 is inserted into the shaft. The three guide shafts 72 are arranged substantially parallel to each other and at equal intervals. In FIG. 2, only two of the three guide shafts 72 and the coil springs 73 in the front of the figure are shown, and one guide shaft 72 and the coil springs 73 at the back of the figure are Hidden in the upper bracket 71.

  As an example, a reamer bolt is used for the guide shaft 72, and its shaft portion is press-fitted into the through hole 71 c of the upper bracket 71 to the root. The head of the reamer bolt located on the upper surface of the upper bracket 71 is pressed by a pressing plate 74 from above. The pressing plate 74 has the same triangular shape as that of the upper bracket 71, and has a deformed ring shape by opening a large round hole 74a therein. The holding plate 74 is fastened to the upper bracket 71 by bolts 75 on both sides of the guide shaft 72.

  On the other hand, in this example, a flanged bush 76 is inserted into the through hole 70c of the lower bracket 70 from above, and the guide shaft 72 is slidably inserted into the cylindrical hole. The bush 76 is formed of a resin material in which lubricating oil is dispersed as an example, and has high slidability. The flange portion 76a of the bush 76 functions as a receiving seat that covers the peripheral edge of the through hole on the upper surface of the lower bracket 70 and receives the lower end of the coil spring 73 that contacts the upper surface.

  A male screw is formed at the lower end portion of the guide shaft 72 that protrudes downward through the bush 76, and a nut 77 is screwed into the male screw. The nut 77 is in contact with the peripheral edge of the through hole 70 c on the lower surface of the lower bracket 70 from below, and functions as a stopper that prevents the lower bracket 70 from falling off the guide shaft 72. In other words, the lower bracket 70 is supported by the guide shaft 72 so as to be slidable (movable) up and down (approaching / separating from the upper bracket 71), and is urged downward by the pressing force of the coil spring 73. The nut 77 is pressed against the nut 77.

  In this state, the shaft portion of the reamer bolt that constitutes the guide shaft 72 is located in the through hole 70c (the tube hole of the bush 76) of the lower bracket 70. The diameter of this shaft portion is the tube diameter of the bush 76. Therefore, a gap is formed between them so that they can slide smoothly. For this reason, when the lower bracket 70 slides along the guide shaft 72, the lower bracket 70 is unlikely to be inclined with respect to the upper bracket 71, and moves up and down in a substantially parallel state.

  And the marker M which is easy to detect by image processing is provided in both the upper and lower brackets 70 and 71 which are approaching / separating from each other. As an example, the marker M is a perfect circle-shaped seal, and is affixed to the approximate center in the longitudinal direction of the three surfaces corresponding to the three sides of the triangle on the outer periphery of each of the upper and lower brackets 70 and 71. The marker M is used to detect the interval between the brackets 70 and 71 when determining the quality of work as described below, and is not limited to sticking a seal but can be provided by printing or stamping. .

-Work quality judgment-
FIG. 3A shows a schematic configuration of the pass / fail judgment system of the present embodiment. This system is a camera 11 (imaging device) installed so as to be able to photograph the marker M of the compliance device 7 at a predetermined distance from the site of work by the robot 1 and an image photographed by the camera 11. And a computer device 12 to which the data is transferred. The computer device 12 performs a predetermined image processing operation on the image data while transmitting and receiving signals to and from the robot controller 13, and an example of the position of the marker M in the image P shown in FIG. Is detected. In FIG. 3A, the robot controller 13 is schematically shown as if it is in the fixed portion 2 of the robot 1, but actually the robot controller 13 is provided outside the robot 1. .

  Further, the computer device 12 calculates the distance D between the upper and lower brackets 70 and 71 from the respective marker positions of the upper and lower brackets 70 and 71 detected in this way, and the quality of the work is determined based on how this changes as the work progresses. Determine. That is, the camera 11 and the computer device 12 constitute a non-contact type position detection device capable of detecting the positions of the upper and lower brackets 70 and 71 of the compliance device 7 provided on the robot arm. Further, it also constitutes work quality judgment means.

  That is, in the image P photographed as shown in FIG. 3B, the outer peripheral surfaces of the brackets 70 and 71 appear in a horizontally long strip shape, and the marker M appears in an elliptical shape thereon. Two of the three markers M may fall within the field of view of the camera 11 due to misalignment of the product 10 or erroneous control. However, for example, by detecting patterns that are as close to a perfect circle as possible by pattern matching. The marker M located near the front of the camera 11 can be detected.

  The distance D between the centers of the markers M of the upper and lower brackets 70 and 71 thus detected is defined as the distance between the upper and lower brackets 70 and 71. Then, as will be described in detail with reference to FIGS. 4 to 6 below, the interval between the upper and lower brackets 70 and 71 is calculated at least twice immediately before the start of the work and after the start of the work, and the state changes. Judge the quality of work.

  FIG. 4 shows a procedure for determining whether or not the work is good, and FIG. 5 is an explanatory view of the work for inserting the pin 9 held by the chuck 8 of the robot 1 into the insertion hole 10a of the product 10 as an example. First, in step S1 after the start in FIG. 4, the robot controller 13 operates the robot arm, and the pin 9 gripped by the chuck 8 is positioned above the insertion hole 10a of the product 10 as shown in FIG. Move to location). At this time, the distance between the upper and lower brackets 70 and 71 is a value set by the position of the nut 77 on the guide shaft 72 in the compliance device 7.

  Upon receiving a signal from the robot controller 13, the computer device 12 takes in the image data taken from the camera 11 and performs image processing calculation, detects the positions of the two markers M as described above, that is, A distance D1 between the upper and lower brackets 70 and 71 is calculated (step S2: detection of the distance D1). The distance D1 obtained in this way corresponds to the set value, and by using this as a reference, the influence of the distance between the robot 1 and the camera 11 can be eliminated as will be described later. In this embodiment, the distance D1 is set to about 30 mm as an example.

  In the image processing calculation, the position where the marker M appears is estimated in advance based on the teaching data of the robot 1, and the image processing calculation is performed within a predetermined range L (indicated by a broken line in FIG. 3B). Narrow the range. In this way, the amount of calculation is much smaller than when performing calculations over the entire image, and the processing time can be shortened.

  Then, the robot controller 13 operates the robot arm, the chuck 8 is lowered, and the pin 9 is inserted into the insertion hole 10a from above (step S3: start of operation). At this time, if the position of the pin 9 substantially matches the insertion hole 10a of the product 10, the pin 9 is smoothly inserted into the insertion hole 10a as schematically shown in FIG. For this reason, a very large force is not applied to the compliance device 7, and the distance D2 between the upper and lower brackets 70 and 71 does not change much from the distance D1 before the work starts.

  On the other hand, when the positional deviation of the pin 9 with respect to the insertion hole 10a of the product 10 becomes large for some reason, the pin 9 is pressed against the opening peripheral edge of the insertion hole 10a as schematically shown in FIG. , Receive upward reaction force. As a result, the lower bracket 70 of the compliance device 7 is pressed upward and is displaced upward as the chuck 8 is lowered. That is, the distance D2 between the upper and lower brackets 70 and 71 of the compliance device 7 is considerably smaller than the distance D1 before the work starts.

  Therefore, the robot controller 13 temporarily stops the robot arm after lowering the robot arm by a predetermined distance, for example, about half of the maximum compression amount allowed for the compliance device 7. Then, the computer device 12 that has received the signal sent from the robot controller 13 takes in the image data taken from the camera 11 in the same manner as in step S2, performs image processing calculation, detects the positions of the two markers M, and detects both of them. That is, the distance D2 between the upper and lower brackets 70 and 71 is calculated (step S4: detection of the distance D2). Note that the marker position may be detected in real time in parallel with the operation without stopping the robot arm.

  At this time, the range of the image processing calculation is narrowed down based on the position of the marker M immediately before the start of work detected in step S2. That is, since the compliance device 7 is lowered by the operation of the robot arm that inserts the pins 9, it is considered that the marker M after the work starts appears in a long region below and below the marker M before the work starts. Therefore, the range of the image processing calculation is narrowed down within this area to shorten the processing time.

  A ratio D2 / D1 between the distance D2 between the upper and lower brackets 70 and 71 after the start of work thus obtained and the distance D1 immediately before the start of work is calculated (step S5), and this ratio D2 / D1 is a preset threshold value R. It is discriminated whether or not (step S6). The threshold value R may be set such that, for example, the difference D1-D2 in the interval before and after the start of work is about 1.0 mm, and the ratio D2 / D1 is larger than this (that is, the absolute value of the difference D1-D2 is small). That is, it can be determined that the compliance device 7 is not compressed so much and the pin 9 is inserted smoothly.

  Instead of determining the work status based on the interval ratio D2 / D1 before and after the start of the work, the work status is determined based on the difference D1-D2 between the intervals before and after the start of the work. Also good. However, the distances D1 and D2 between the upper and lower brackets 70 and 71 detected by the image processing as described above vary depending on the distance between the place where the work is performed and the place where the camera 11 is installed, and the difference D1-D2 is large. Since this also changes, it can be said that if it is compared with the threshold value R, it is preferable to make a determination based on the ratio. As a specific method of taking the ratio, for example, D1 / D2 may be used, (D2-D1) / D1 may be used, or another format may be used.

  If the determination in step S6 is YES, the insertion operation has proceeded smoothly, and it is only necessary to continue this. Therefore, the robot controller 13 that has received the signal from the computer device 12 completes the predetermined operation routine to the end. This is executed (step S7), and the control is ended (END). Therefore, the robot arm further lowers by a predetermined amount, then opens the chuck 8 and releases the pin 9 and then retreats upward.

  On the other hand, if the ratio D2 / D1 calculated in step S5 is equal to or less than the threshold value R (NO in step S6), the compliance device 7 has been compressed by receiving a large resistance force to some extent, and the pin 9 is It is considered difficult to insert into the insertion hole 10a. Therefore, the robot controller 13 that has received a signal from the computer device 12 interrupts the work routine and raises the chuck 8 (step S8), prepares for a retry and returns to step S1, or stops the work. Announce abnormality.

  That is, in this example, if a predetermined resistance or more is applied to the insertion due to the size or assembly error of the pin 9 or the like, or the influence of foreign matter such as burrs, it is determined that the work is not performed well. If the insertion is possible even if there is some resistance due to friction or the like, it is determined that the work is performed well. In other words, the quality of the work is determined by obtaining the magnitude of the resistance against the insertion of the pin 9 from the interval between the brackets 70 and 71 of the compliance device 7.

  For the determination, the ratio D2 / D1 of the distance D2 after the work is started with respect to the distance D1 between the upper and lower brackets 70 and 71 in the compliance device 7 before the work is started. As a result, the distance between the upper and lower brackets 70 and 71 can be accurately detected without being affected by the distance between the robot 1 and the camera 11 whether the distance between the robot 1 and the camera 11 is long or close, and the quality of the work can be accurately determined. .

  Next, the case of screw tightening work will be described with reference to FIG. In this case, the bolt 15 gripped by the chuck 8 of the robot 1 is screwed into the screw hole 16 a of the product 16. In this case, in step S1 of the flow of FIG. 4 described above, the lower end of the bolt 15 gripped by the chuck 8 is pressed against the opening of the screw hole 16a of the product 16 (moved to the work place). At this time, the lower bracket 70 of the compliance device 7 is pressed upward by the upward force received by the bolt 15 and displaced upward as shown in FIG.

  Thus, in the case of the screw tightening work, the coil spring 73 is compressed in the state immediately before the start of the work, and the distance between the upper and lower brackets 70 and 71 is reduced, and the reference marker distance D1 is detected in this state ( Step S2). That is, similar to the insertion operation of the pin 9 described above, the computer device 12 that has received the signal from the robot controller 13 takes in the image data from the camera 11 and performs image processing calculation to calculate the interval D1 between the two markers M.

  Subsequently, the screw tightening operation is started. When the compliance device 7 and the chuck 8 are rotated by the electric motor of the wrist portion 6 without changing the position of the robot arm, the bolt 15 is screwed into the screw hole 16a along with the rotation. Go (step S3). At this time, the bolt 15 receives a pressing force from the compliance device 7 and is pushed downward. The bolt 15 is lowered by a screw pitch every rotation, so that the robot 8 is moved down in synchronization with the rotation of the bolt 15. Advanced motion control that moves the arm accurately is unnecessary.

  Then, after the bolt 15 is rotated a predetermined number of times, the bolt 15 is once stopped and the computer device 12 detects the interval between the two markers M, that is, the interval D2 between the upper and lower brackets 70 and 71 (step S2). Step S4). Then, an interval ratio D2 / D1 before and after the start of work is calculated (step S5), and it is determined whether or not it is larger than a preset threshold value R (step S6).

  In the case of this screw tightening operation, as in the case of the insertion operation described above, instead of the interval ratio D2 / D1 before and after the start of the operation, another ratio such as D1 / D2, (D2-D1) / D1 is used. It may be used, or the work status may be determined based on the difference between the intervals. In this case, since the distance D2 is larger, the difference between the distances may be D2-D1, but the absolute value of D1-D2 may be used.

  Further, for example, when the pressing force of the bolt is varied for each work location, the interval D1 may vary depending on the work location. In such a case, the marker interval before the lower end of the bolt 15 is pressed against the opening of the screw hole 16a of the product 16 is detected in the same manner as the insertion operation of the pin 9 described above, and this is replaced with the interval D1. It may be used as a reference value.

  The threshold R is, for example, based on a value obtained by multiplying a screw pitch by a desired number of rotations, more specifically, a screw pitch 1 mm × 2 rotations = 2 mm as a reference, and an interval difference D2-D1 between before and after the start of work is about 2 mm. If the ratio D2 / D1 is larger than this (YES in step S6), it is schematically shown in FIG. 6B as the bolt 15 is screwed into the screw hole 16a. Thus, it is considered that the distance D2 between the upper and lower brackets 70 and 71 in the compliance device 7 is widened. Therefore, if YES is determined in step S6, the work routine is executed to the end (step S7), the bolt 15 is further screwed in, the chuck 8 is opened, the bolt 15 is released, and the robot arm is retracted upward. End of work (end).

  On the other hand, if the ratio D2 / D1 calculated in step S5 is equal to or less than the threshold value R (NO in step S6), the compliance device 7 is the same as before the work starts as schematically shown in FIG. It is determined that it remains compressed and the bolt 15 is idle and not fully screwed. Therefore, the work routine is interrupted and the chuck 8 is pulled up (step S8), and preparations for retry are made and the process returns to step S1, or the work is stopped and an abnormality is notified.

  That is, in the case of the screw tightening operation, the change in the interval between the upper and lower brackets 70 and 71 of the compliance device 7 that is gradually released from the compression with the progress of the operation on the basis of the state in which the compliance device 7 is compressed immediately before the start. The quality of the work is determined based on the above.

  As described above, according to the quality determination system for work according to the present embodiment, the compliance device 7 is interposed between the chuck arm 8 of the robot arm that grips a workpiece such as the pin 9 and the bolt 15 and the wrist portion 6. It is compressed by the force received during work. Then, the marker M provided on each of the brackets 70 and 71 of the compliance device 7 is photographed by the camera 11, and the quality of the work is determined based on the change in the distance D between the brackets 70 and 71 detected by the image processing. Can do.

  Therefore, there is no need to dispose a displacement sensor, a torque sensor, or the like in the vicinity of the chuck 8 or the wrist 6 of the hand of the robot 1, and it is possible to suppress the increase in size and increase in the number of cables, There is no need to worry about sensor failure due to impact or the like.

-Other embodiments-
The above description of the embodiment is merely an example, and does not limit the present invention, its application, or its use. For example, in the above-described embodiment, the brackets 70 and 71 of the compliance device 7 have a triangular shape, and the circular markers M are provided on the three outer peripheral surfaces, respectively, but the marker M has one or two surfaces. The shape may not be limited to a circle.

  However, since a plurality of markers M are provided on each of the brackets 70 and 71, in the above-described embodiment, when the robot 1 performs work at two or more places in the field of view of the camera 11, it corresponds to each work place. This is advantageous in setting the marker M to be positioned in front of the camera 11.

  Further, when the bolt 15 is rotated as in the above-described screw tightening operation, the compliance device 7 is also rotated together with the chuck 8 that grips the bolt 15. Therefore, as shown in FIG. The shape of 171 may be a disk shape orthogonal to the rotation axis f (rotation center line of the workpiece) of the electric motor, and the marker M may be provided on substantially the entire outer periphery thereof.

  In this way, even if the compliance device 7 rotates as the bolt 15 is tightened, the markers M on the outer periphery of the brackets 170 and 171 are always in the field of view of the camera 11 and the distance between the marker M and the camera 11 Therefore, it is possible to determine the quality of the work by detecting the marker position at any timing during the work or continuously during the work, that is, in real time. In addition, in the case of the insertion work of the pin 9, even if it is the marker M like the said embodiment, a marker position can be detected in real time and the quality of work can be determined.

  Furthermore, in the compliance device 7 of the above-described embodiment, the coil spring 73 is extrapolated to the three guide shafts 72 to apply the urging force between the upper and lower brackets 70, 71. is not. Instead of the coil spring 73, a large coil spring or a leaf spring may be interposed between the upper and lower brackets 70, 71 concentrically with the round holes 71a, 70a. Moreover, you may interpose a rubber elastic body. For example, a damping means such as a viscous damper or a friction damper may be provided. The number of guide shafts 72 may be one or two, but is preferably three or more from the viewpoint of suppressing unnecessary inclination between the upper and lower brackets 70 and 71.

  In the above-described embodiment, the camera 11 and the computer device 12 are used one by one to detect the distance between the upper and lower brackets 70 and 71 of the compliance device 7. 11 and at least one of the computer devices 12 may be provided to perform photographing (image acquisition) and image processing calculation in parallel so that at least a part of them simultaneously proceeds.

  In addition, the distance between the upper and lower brackets 70 and 71 of the compliance device 7 is detected by using a non-contact type position detection device such as a laser displacement meter or a laser surveying instrument instead of using the camera 11 or the computer device 12. You may do it.

  Furthermore, the quality determination apparatus according to the present invention is not limited to the work performed by the robot 1 as in the above-described embodiment, but is applied to the work performed by other various automatic assembly machines, machine apparatuses such as processing apparatuses. Also good.

  As described above, according to the work quality determination system according to the present invention, it is possible to avoid an increase in size and an increase in the number of cables due to the provision of a sensor in the vicinity of the work holding unit in a robot, an automatic assembly machine, etc. Since failure can be prevented, it is very useful for an assembly robot, for example.

1 Robot (mechanical device)
6 Arm wrist (support)
7 Compliance device (movable part)
70 Lower bracket (member on holding side)
71 Upper bracket (support side member)
72 Guide shaft 73 Coil spring (spring member)
8 Chuck (holding part)
9 pins (work)
11 Camera (imaging device)
12 Computer device (image processing device, pass / fail judgment means)
15 bolts (work)
M marker

Claims (14)

A system for judging the quality of work performed by a mechanical device,
A movable part is provided between the holding part of the work in the mechanical device and the support part that supports the holding part so that both are relatively displaced by the force received from the work during the work,
A non-contact type position detection device capable of detecting the positions of the holding unit and the support unit apart from both the holding unit and the support unit,
A quality determination means for determining quality of the work based on a relative positional relationship between the holding part and the support part detected by the position detection device at the time of the work. Pass / fail judgment system. Markers are respectively provided on the holding part side and the support part side members of the movable part,
The position detection device is an imaging device arranged so as to be capable of photographing the marker;
The work quality determination system according to claim 1, further comprising: an image processing device that detects a position of the marker in an image photographed by the imaging device.   The pass / fail judgment means obtains an interval between the two members from the respective marker positions of the holding part side and support part side members detected immediately before the start of the work, and both the detected two parts detected after the start of the work. The work quality determination system according to claim 2, wherein an interval between the two members is obtained from each marker position of the member, and the quality of the work is determined from a change in the distance between the two members accompanying the work.   The pass / fail judgment means compares a ratio between the interval between the holding unit side and the support unit side members obtained immediately before the start of the work and the interval between the members obtained after the start of the operation with a preset threshold value. The work quality determination system according to claim 3, wherein the quality of the work is determined.   The image processing apparatus sets an image processing calculation range for detecting a marker position after the start of the operation based on the marker positions on the holding unit side and the support unit side detected immediately before the start of the operation. The quality determination system for work according to claim 3, wherein the system is narrowed down.   The work quality determination system according to any one of claims 3 to 5, wherein the image processing device narrows a range of an image processing calculation for detecting the marker position based on control data of the mechanical device. .   The position detection device includes at least one of at least one of an imaging device and an image processing device, and performs acquisition of an image including the marker and image processing calculation in parallel so that at least a part thereof proceeds simultaneously. The work quality determination system according to any one of 2 to 6. The work includes an operation of rotating the workpiece,
The members on the holding part side and the support part side of the movable part are respectively disk-shaped members orthogonal to the rotation center line of the workpiece, and the marker is provided on the outer periphery thereof over substantially the entire circumference. Item 9. The system for determining whether work is good or bad according to any one of Items 2 to 7.   The elastic body is interposed between the members on the holding portion side and the support portion side of the movable portion so as to be elastically deformed by the force received from the work during the work. The system for judging the quality of work described in 1.   The pass / fail judgment means obtains the magnitude of the force acting between the two members from the interval between the members on the holding part side and the support part side detected by the position detection device during the work. The work quality determination system according to claim 9, wherein: The movable part is provided between the holding part side member and the support part side member, and penetrates one of the members to support the one member so as to move toward and away from the other member. With a shaft,
The work quality determination system according to claim 10, wherein the elastic body is a spring member that applies an urging force that separates the two members from each other. A method for determining the quality of work performed by a mechanical device,
A movable part is provided between the holding part of the work in the mechanical device and the support part that supports the holding part so that both are relatively displaced by the force received from the work during the work,
At the time of the work, the relative positional relationship between the holding part and the support part is detected by a non-contact type position detection device at a place away from both the holding part and the support part, and the work result is determined based on the detection result. A work quality determination method characterized by determining quality. A marker is provided on each of the movable part holding part side and supporting part side members,
An imaging device is arranged so that the marker can be photographed, and the position of the marker in an image photographed by the imaging device is detected by image processing,
The work quality determination method according to claim 12, wherein the quality of the work is determined by determining a change in a distance between the holding part side and the support part side members associated with the work from the position of the detected marker. An elastic body is interposed between the members on the holding portion side and the support portion side of the movable portion so as to be elastically deformed by the force received from the work during the work,
The quality of the work is determined by determining the magnitude of the force acting between the members on the holding part side and the support part side detected during the work, and determining the quality of the work. A method for determining the quality of the described work.

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