JP2013006244A - Method and control device for alignment of robot cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time before resuming production without causing cost increase, when changing a work content of a robot cell.SOLUTION: A method is provided for alignment of the robot cell 1 including a robot 4, a working tool T selectively detached to the wrist of the robot 4, and a tool stand 3 for retaining the working tool T in a standby mode. The method includes: executing a tool change operation for replacing the working tool T based on a preset command value; and correcting a command value in the direction of decreasing a load based on the size and orientation of the load, which is generated by the interference between the robot 4 and the working tool T during the tool change operation.

Description

  The present invention relates to a position correction before starting production of a robot that includes a tool change mechanism for exchanging a tool according to a program and performs a machining operation or the like by changing the tool according to the work content.

  In recent years, robots have been introduced into production lines such as vehicles, and in particular, a plurality of tools such as screw tightening, welding, and grease application are performed by a single unit by appropriately replacing a plurality of tools by a tool change mechanism. The introduction of robots that can do this is progressing. Such a robot is unitized as a robot cell together with a jig (locator) for fixing a workpiece and a tool stand for holding a plurality of tools to be used, and the work is performed using a plurality of robot cells on one production line. Things are also done.

  When using a robot cell, it is necessary to learn the relative relationship between the robot and the tool previously held on the tool stand and the relative relationship between the robot and the workpiece, so-called alignment is required. Is done. This teaching needs to be performed for each robot cell when a plurality of robot cells are used in one production line. This is because the position where the tool is held on standby and the processing part of the workpiece differ depending on the work contents of the robot cell, and there are also deviations due to individual differences for each robot cell.

  These teachings need to be performed with the robot cell installed on the production line. This is because the relative relationship between the robot and the tool stand and the relative relationship between the robot and the locator may change depending on the state of the installation location, for example, the smoothness of the floor surface.

  Thus, since it is necessary to perform teaching for each robot cell, it takes a considerable amount of time to operate the production line.

  By the way, in the production line, it is desirable to be able to flexibly cope with the increase / decrease adjustment of the production volume and the model change of the product. For example, in order to reduce the production amount, it is sufficient to slow down the workpiece conveyance speed and conveyance timing, but this reduces the facility operation rate. Therefore, the work contents of the robot cell are changed, for example, the work that has been shared by the five robot cells so far is changed to be shared by the three. According to this, it is possible to move the surplus two units to another line of the production increase system or to perform maintenance during the suspension.

  However, when the work content is changed, teaching is necessary for the position of the tool to be newly used. Also, when moving the robot cell to another line, it is necessary to perform teaching on the destination line. As described above, since teaching takes a considerable amount of time, not only the cost increases due to an increase in the number of man-hours, but also the line suspension period until the production is started after changing the work content is lengthened.

  Therefore, as a configuration for shortening the time required for teaching, a program is installed in which a camera is mounted on the arm of the robot, a deviation from a predetermined position of the robot is detected by image processing, and the deviation is corrected based on the detection result. Such a configuration is disclosed in Patent Document 1.

JP 2009-208209 A

  However, when detecting a positional shift by image processing, it is necessary to increase the resolution of the camera as the required accuracy of position adjustment increases, resulting in an increase in cost. Further, although only one camera is mounted in Patent Document 1, a plurality of cameras are required to detect a three-dimensional position shift, which further increases the cost.

  Furthermore, since the weight increases by mounting a plurality of cameras, an increase in the size of an actuator that drives the robot and securing of the load-bearing performance of the arm also cause an increase in cost.

  In order to avoid these cost increases, all teaching cannot be abolished. Therefore, when the work contents of the robot cell are changed, it takes a considerable time to resume production.

  Therefore, in the present invention, when changing the work contents of the robot cell in accordance with a change in the production plan, etc., a robot and a tool stand that can resume production promptly without causing an increase in cost, It is an object of the present invention to provide an alignment method.

  The present invention is a method for aligning a robot cell, which includes a robot, a work tool that is selectively attached to and detached from the wrist of the robot, and a tool stand that holds a work tool that is on standby. Then, based on the step of performing a tool change operation for exchanging the work tool based on a preset command value, and the magnitude and direction of the load generated by the interference between the robot and the work tool during the tool change operation, And a step of correcting the command value in the direction in which the load decreases.

  According to the present invention, since the command value for the robot is corrected so as to reduce the load generated by the interference between the robot and the work tool, the cost can be increased in a shorter time than conventional teaching and as in image processing. Production can be resumed without incurring.

It is a front view which shows the structure of the robot cell to which embodiment of this invention is applied. It is a top view which shows the structure of the robot cell to which embodiment of this invention is applied. It is a figure which shows the arm tip vicinity of a robot. It is a figure which shows an example of a hand. It is a figure which shows an example of a tool. It is a figure which shows the state which the robot hold | gripped the tool. It is a top view of a locator. It is a front view of a locator. It is a figure which shows a 1st positioning pin. It is a figure which shows a 2nd positioning pin. It is a flowchart which shows the routine of the alignment performed by a control apparatus. It is a figure which shows the relationship between the load input into a force sensor, and the positional offset amount between a robot and a tool.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show a robot cell to which the present embodiment is applied. FIG. 1 is a front view and FIG. 2 is a plan view.

  The robot cell 1 includes a tool stand 3 that holds each work tool T and a hand H for assembling parts to a work, and a robot 4 that performs assembly work by attaching or detaching either the work tool T or the hand H to the tip of a wrist. With.

  The robot cell 1 is transported from the previous stroke by the conveyor 2 for transporting the workpiece and the parts to be assembled to the workpiece. The conveyor 2 includes a locator 2A for loading and fixing a workpiece and a kit pallet 2B for loading a component to be assembled to the workpiece. The conveyor 2 is stopped at a predetermined position with respect to the robot cell 1, and after the parts on the kit pallet 2B are sequentially assembled to the workpiece, they are transported to the next process.

  The tool stand 3 includes an upstream tool stand 3A disposed across the conveyor 2 on the upstream side in the transport direction, and a downstream tool stand 3B disposed on the downstream side in the transport direction. In the following description, when an individual tool stand is shown, the symbol is 3A and 3B, and when both are collectively referred to, the symbol is simply 3.

  Tools T2, T3, and a hand H3 are detachably mounted on the rear side (upper side in FIG. 2) across the conveyor 2 of the upstream tool stand 3A. Further, a hand H2 is detachably mounted on the front side (lower side in FIG. 2) across the conveyor 2 of the upstream tool stand 3A. Further, the downstream tool stand 3B is equipped with a tool T1, a hand H1, and a tool T4 so as to be detachable. Examples of the tools T1-T4 include a screw tightening tool, a grease application tool, a soldering tool, and the like. Examples of the hands H1-H3 include a board assembling hand, a power module assembling hand, and the like.

  In the following description, the symbol is T1-T4 when indicating an individual tool, and the symbol is simply T when indicating an overall tool. Similarly, for the hand, the codes H1-H3 and H are properly used.

  3 shows an arm 4a of the robot 4, FIG. 4 shows a sheet assembling hand as an example of the hand H, and FIG. 5 shows a grease application tool as an example of the tool T.

  The robot 4 includes a tool change mechanism that changes the tool T or the hand H according to the work content in accordance with a program stored in the control device 5, and a main body side adapter 20 is provided at the tip of the arm 4a. ing. On the hand H side and the tool T side, a hand adapter 21 and a tool side adapter 22 detachably attached to the main body side adapter 20 are provided.

  As shown in FIG. 4, a plurality of suction nozzles 23 </ b> A that are fixed to the tip plate 25 and suck and grip a plate-like sheet are arranged on the hand H side. Further, as shown in FIG. 5, the same plate 25 as that provided on the hand H side adapter 21 is also provided on the tool T side, and the working tool T is fixed to the tip side with the plate 25 interposed therebetween. Equipped.

  Note that the plate 25 is, for example, a quadrangular plate material, and this portion is engaged with a receiving piece provided on the tool stand 3, whereby the waiting tool T and hand H are held by the tool stand 3.

  The main body side adapter 20 has a tapered portion 20A at the tip, and the attachment / detachment portion of the hand side adapter 21 and the tool side adapter 22 to the main body side adapter 20 of the robot 4 (the surface on the left end side in FIGS. 4 and 5) Recesses 21A and 22A in which the main body side adapter 20 is accommodated are provided.

  Even if there is a deviation from the design value in the position of the robot 4 and the tool T or hand H, if the taper portion 20A is displaced within the range where it hits the peripheral edge of the recesses 21A and 22A during the tool change operation, the tool can be pushed in You can make changes. The tapered portion 20A is designed so that the tool can be changed even when there is a deviation of about ± 1 mm.

  In addition, the robot 4 includes a force sensor 30 that can detect inputs from the three axes of X, Y, and Z on the arm 4a. The detection values of the force sensor 30, that is, the input direction and the input load are read into a control unit built in the robot 4 and used for alignment described later.

  FIG. 6 shows a state where the robot 4 holds the tool T. Here, a grease application tool is shown as an example of the tool T. As shown in FIG. 6, in a state where the robot 4 grips the tool T, the main body side adapter 20 is accommodated in the recess 21 </ b> A provided in the tool side adapter 22.

  7A and 7B show an example of the locator 2A. FIG. 7A is a plan view and FIG. 7B is a front view. The locator 2A is a pedestal 71 fixed to the conveyor 2 with bolts, a support column 72 extending vertically upward therefrom, and a horizontal direction at the upper end of the support column 72 and orthogonal to the traveling direction of the conveyor 2 (hereinafter referred to as the conveyance direction). And a support member 74 and 75 extending from both ends of the plate member 73 in the transport direction.

  The support member 74 includes a first positioning pin 76 near the rear end in the transport direction. The support member 75 includes a first positioning pin 76 near the front end in the transport direction, and two second positioning pins 77 behind the first positioning pin 76 in the transport direction. The first positioning pin 76 is, for example, a cylindrical pin having a stepped shape as shown in FIG. 8A. Further, the second positioning pin 77 is a pin having a cylindrical body protruding from the support member 75 as shown in FIG. 8B, for example. The first positioning pin 76 and the second positioning pin 77 fix the work to the locator 2A by fitting the positioning pin on the vehicle side into the service hole that becomes a reference for dimension measurement when the product is mounted on the vehicle. Is for. Therefore, it is not limited to the position shown in FIGS. 7A and 7B and the shape shown in FIGS. 8A and 8B, and the arrangement and shape differ depending on the product to be manufactured.

  The robot cell 1 described above can execute all the processes up to the completion of the product with one unit. However, in an actual production line, a plurality of robot cells 1 are arranged in series, parts are attached, and screws are tightened. , Share and execute work such as welding and grease application. Accordingly, only the tool T for work performed in the robot cell 1 is provided on the tool stand 3. And before starting production, the tool T to be used and the robot 4 are aligned.

  By the way, in the production line in which five robot cells 1 of # 1 to # 5 are arranged, for example, when the production is reduced by changing the production plan, the following pattern can be taken. The first is a pattern in which five robot cells 1 are used as they are, and the transfer speed and timing are changed. The second pattern is a pattern in which the number of robot cells 1 that perform work is reduced from, for example, three to # 1 to # 3, and the remaining two # 4 and # 5 are suspended.

  In the first pattern, it is possible to cope with the change of the production plan because it can be dealt with only by changing the conveyance speed and timing, but the operation efficiency of the facility is lowered.

  On the other hand, in the second pattern, it is possible to effectively use the suspension period, for example, by transferring the two robot cells that have been suspended to another production line or performing maintenance.

  However, if the work that was previously shared by 5 units is shared by 3 units, the work that was shared by the 2 units that have been suspended will be assigned to one of the 3 units. The used tool T or the like is moved to any of # 1 to # 3. In this case, it is necessary to align the tool T or the like that has newly moved with the robot 4. This alignment is necessary even if the position in the tool stand 3 is the same as the position in the tool stand 3 in the robot cell 1 used so far. For example, although the tool T3 is provided in # 4, but the tool T3 in FIG. 2 is not used because the tool T3 is not used in # 1, the tool T3 used in # 4 is replaced by # Even when moving to the position of one tool T3, it is necessary. This is because the positional relationship between the robot 4 and the tool stand 3 has individual differences in the tolerance range even if the design values are the same.

  When moving to another production line, in addition to the alignment between the tool T and the robot 4, the alignment between the robot 4 and the locator 2A is also required. This is because if the place where the robot cell 1 is installed changes, conditions such as smoothness and inclination change, and as a result, the positional relationship between the robot 4 and the locator 2A also changes.

  For the alignment as described above, an operation called teaching is generally performed. For example, first, the coordinates of the position where the robot 4 grips the tool T are set based on the design value of the robot cell 1 and the robot 4 is operated. The position where the robot 4 actually grips the tool T and the position of the tool T Find the deviation from the position. Then, the coordinates are reset so as to eliminate this deviation, and the robot 4 is operated again. This process is repeated until there is no deviation.

  Such teaching is executed for every robot cell 1 for all tools T and hands H used in the robot cell 1. Therefore, teaching takes a considerable amount of time, and if it is executed every time the production plan is changed, the production efficiency is lowered.

  Therefore, in the present embodiment, alignment is performed by the method described below without performing the above teaching.

  Note that the control device 5 of each robot cell 1 stores a program for all the operations to be executed on the production line. Therefore, even when the work content of the robot 4 is changed, the program can be handled only by changing the selected program.

  First, alignment between the robot 4 and the tool T or hand H will be described.

  FIG. 9 is a flowchart showing a routine for alignment between the robot 4 and the tool T or hand H, which is executed by the control device 5. This routine is executed before resuming production in principle, but may be executed at the first tool change after resuming production.

  The control device 5 sets the coordinates of the position where the tool T or the hand H is gripped (gripping position) based on the design value, and executes the tool change operation. At this time, if there is a deviation between the design value and the actual position, the robot 4 cannot grasp the tool T or the hand H, and the input value to the force sensor 30 becomes larger than when there is no deviation. Therefore, the control device 5 corrects the grip position of the robot 4 so that the detection value of the force sensor 30 becomes small. Hereinafter, it demonstrates according to the step of a flowchart.

  In step S <b> 10, the control device 5 decreases the operation speed of the robot 4. Specifically, after the tool change, the speed of the robot 4 is made lower than the speed when the tool T moves to the work part of the workpiece. This is to reduce the impact when the robot 4 collides with the tool T or the hand H in an operation in steps described later.

  In step S20, the control device 5 starts a tool change operation. At this time, coordinates calculated based on the design value are set as the gripping positions.

  In step S <b> 30, the control device 5 determines whether there is a positional shift based on the detection value of the force sensor 30. The presence / absence of positional deviation can be determined by the magnitude of the input load to the force sensor 30. FIG. 10 is a diagram illustrating a relationship between an input load to the force sensor 30 and a positional shift in the X-axis direction. The “target value” in the figure is an input load to the force sensor 30 when a tool change is performed with no positional deviation. That is, the load is generated when the main body side adapter 20 and the tool T or the hand H come into contact with each other when the tool change operation is performed in a state where there is no positional deviation.

  As shown in FIG. 10, the input load to the force sensor 30 becomes a target value when there is no positional deviation, and the input load increases away from the target value as the positional deviation amount increases. If the displacement is such that the tool can be changed by the action of the tapered portion 20A described above, the input load becomes substantially the target value. This characteristic is the same as that of FIG. 10 for the Y axis and the Z axis.

  Therefore, in step S30, the control device 5 determines that there is a positional deviation if the input load exceeds a preset value before the robot 4 reaches the coordinates set as the gripping position. On the other hand, if the input load reaches the gripping position without becoming larger than a preset value, it is determined that there is no positional deviation. As the preset value, for example, an input load when the tool change exceeds a possible range by the action of the taper portion 20 is set.

  When it is determined that there is a positional deviation, the process of step S50 is executed, and when it is determined that there is no positional deviation, the process of step S40 is executed.

  In step S40, the control device 5 executes a tool change, restores the operating speed of the robot 4, and ends this routine.

  In step S50, the control device 5 adjusts the position where the robot 4 grasps the tool T or the hand H according to the following procedure. When the adjustment is completed, the operation speed of the robot 4 is returned to the original and the routine is finished.

  First, the direction and magnitude of the input load to the force sensor 30 are read, and the coordinates of the grip position are corrected in the direction in which the input load decreases based on these data. The correction amount is determined from the positional shift amount and the input load in FIG. When the coordinates of the grip position are corrected, the robot 4 is operated according to the corrected coordinates, and a tool change is performed. Hereinafter, the corrected coordinates are used as the gripping position.

  If the alignment is performed as described above, the robot 4 and the tool T or hand can be measured without performing conventional teaching that repeats the measurement of the positional deviation and the change of the coordinates of the gripping position based on the measurement value until the positional deviation is eliminated. Alignment with H can be performed. Therefore, when the work content of the robot cell 1 is changed by changing the production plan or the like, the production can be resumed promptly.

  Although it is possible to mount a camera on the arm 4A of the robot 4 and perform alignment by image processing, a plurality of cameras are required to detect misalignment in the X, Y, and Z directions. In order to increase the detection accuracy of the deviation, a camera with high resolution is required. Both increase the cost, and when mounting multiple cameras, it is necessary to ensure the load bearing performance of the arm 4A and the output of the driving actuator as the weight of the arm 4A increases. This also increases the cost.

  However, the force sensor 30 is generally about several tens of grams, which is significantly lighter than a camera and can be manufactured at a low cost.

  Next, alignment between the robot 4 and the locator 2A will be described.

  When the robot cell 1 is moved to another production line, the support members 74 and 75 are changed to those used in the production line, and the arm 4A of the robot 4 is caused to grip a dial gauge as the tool T. Further, in the control device 5, the positions in the X, Y, and Z directions of the first positioning pin 76 and the second positioning pin 77 based on the design value are set in advance as the reference position of the locator 2A.

And the position of the 1st positioning pin 76 and the 2nd positioning pin 77 is measured with a dial gauge. For example, as shown in FIGS. 8A and 8B, for the first positioning pin 76, a dial gauge is applied to the side surface 76A of the small diameter portion to measure the position in the X direction and the Y direction, and the upper surface 76B of the large diameter portion is measured. Apply the dial gauge to measure the position in the Z direction. About the 2nd positioning pin 77, a dial gauge is applied to the upper surface 77A, and the position of a Z direction is measured. These measured values are compared with a reference value, and the reference value is corrected using the difference as a correction amount. Since the positioning accuracy increases as the number of measurement parts increases, the side surface of the second positioning pin 77 may also be measured.

  If the positioning of the robot 4 and the locator 2A is performed as described above, teaching as in the prior art becomes unnecessary, and the cost does not increase as in the case of positioning by image processing or the like. In addition, the program that has been used can be used as it is.

  When the robot cell 1 is moved to another production line, not only alignment with the locator 2A but also alignment with the tool T and hand H described above is required.

  As described above, according to the present embodiment, the following effects can be obtained.

  (1) A tool change for exchanging the tool T or the like is executed based on the command value calculated from the design value, and the magnitude and direction of the load generated by the interference between the robot 4 and the tool T or the like during the tool change operation. Based on this, the command value is corrected in the direction in which the load decreases. Thereby, the conventional teaching becomes unnecessary and production can be resumed promptly. In addition, the cost does not increase unlike image processing using a camera.

  (2) Since the position of the predetermined part of the locator 2A is measured and corrected based on the difference between the reference value, which is the position of the predetermined part determined based on the design value, and the actual measurement value, it matches the actual measurement value. Teaching is not required for the locator 2A, and production can be resumed promptly.

  (3) Since the speed of the tool change operation is lower than the speed of moving to the workpiece after the tool change is completed, the impact when the robot 4 and the tool T collide can be reduced.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Robot cell 2 Conveyor 2A Locator 2B Kit pallet 3 Tool stand 4 Robot 5 Control apparatus 20 Main body side adapter 21 Hand adapter 22 Tool side adapter 30 Force sensor 76 1st positioning pin 77 2nd positioning pin

Claims (4)

With robots,
A work tool selectively attached to and detached from the wrist of the robot;
A tool stand for holding the waiting work tool;
A method for aligning a robot cell including
Performing a tool change operation for replacing the work tool based on a preset command value;
Correcting the command value in the direction in which the load decreases based on the magnitude and direction of the load generated by the robot and the work tool interfering during the tool change operation;
A method for aligning a robot cell, comprising: The robot cell further includes a locator for fixing and supporting the workpiece;
Measuring the position of the predetermined part of the locator;
Correcting the reference value to match the actual measurement value based on the difference between the reference value that is the position of the predetermined part calculated from the design value and the actual measurement value obtained by the measurement;
The robot cell positioning method according to claim 1, further comprising:   The robot cell alignment method according to claim 1, wherein a speed of the tool change operation is lower than a speed of moving to the workpiece after the tool change is completed. With robots,
A work tool selectively attached to and detached from the wrist of the robot;
A tool stand for holding the waiting work tool;
In a robot cell alignment control device having a tool change function in which the robot replaces the work tool based on a command value,
Load detecting means for detecting the magnitude and direction of the load generated by the interference between the robot and the work tool during a tool change operation;
With
The robot cell alignment control apparatus, wherein the command value is corrected so that the load is reduced based on the magnitude and direction of the load.

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