JP3287152B2 - Automatic assembly of workpieces by assembly robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically assembling a work by an assembling robot, and more particularly to a method which does not require accurate positioning of an assembling work.

[0002]

2. Description of the Related Art In the work of assembling a work by an assembling robot, it is essential to check whether or not the work has been correctly assembled to an object to be assembled. The test was either performed or performed using a visual sensor.
In addition, in order to increase the success rate of assembly, high accuracy is required for the work, and in actual assembly work, it is necessary to accurately teach the operating position of the robot and accurately position the work. I was

[0003]

However, there are many resin molded products in the work for assembling, and a flexible product such as a resin molded product has a large solid difference from the manufacturing point of view. is there. Therefore, when a flexible object such as a resin molded product is used as the work for assembly, it is difficult to accurately position the work, and in practice, it is also difficult to accurately teach the operation of the robot. Therefore, in this case, it is necessary to work without teaching the movement of the robot so accurately, but rather with a feeling similar to that of a human being, that is, while feeling the degree of the force applied to the hand (hand), It is important to perform the work while performing force control by force sense to finely control the force of the assembling operation.

[0004] In the method of inspecting the quality of assembly using a visual sensor, there are places (blind spots) that cannot be seen by the visual sensor, or time is required for sensing by the visual sensor. However, there is a problem in inspection accuracy and inspection time. Further, since a visual sensor and a peripheral device for the visual sensor are required, the configuration of the robot system tends to be complicated.

The present invention has been made in view of the above-mentioned problems of the prior art, and does not use a visual device and does not require accurate positioning of an assembling work. It is an object of the present invention to provide a method for automatically assembling a workpiece by an assembling robot, which can automatically inspect the quality of the workpiece.

[0006]

According to a first aspect of the present invention, there is provided a method for automatically assembling a workpiece by an assembling robot, comprising the steps of: detecting a force sensor mounted on a wrist of the assembling robot; Make sure the value is within the specified tolerance
Then, while correcting the position of the arm of the assembling robot,
Performing the work assembling operation; opening the hand to release the work when the assembling operation to be performed while correcting is completed;
Finish the actual assembling operation at the taught hand position
A step of moving the the hand, a step of holding the workpiece by closing the hand, a step retracting movement in the opposite direction of the assembling operation taught a hand, the hand is moved forward in the same direction as the operation with the set while comparing and detecting the force information applied to the wrist, the force pattern during teaching the detected force information, the assembled state of the presence or absence of their consistency
Judging the quality of the product

According to a second aspect of the present invention, there is provided a method of automatically assembling a work by an assembling robot, wherein the hand is opened when the assembling operation is completed. Prior to the step of releasing the work, the method includes a step of moving the hand such that an error between force information applied to the hand and that at the time of teaching falls within an allowable range.

According to a third aspect of the present invention, there is provided a method of automatically assembling a workpiece by an assembling robot according to the first aspect of the present invention. After the step of comparing with the patterns and judging the coincidence of the patterns, a step of outputting a warning of an improper assembly when it is determined that they do not match is provided.

According to a fourth aspect of the present invention, there is provided a method for automatically assembling a workpiece by an assembling robot, wherein the hand is moved to a taught work end point. Wherein the hand is moved to the work end point while being retracted so as not to interfere with the work.

[0010]

According to the method for automatically assembling a work by the assembling robot according to the first aspect of the present invention, the assembling of the work is performed by using a detection value of a force sensor mounted on a wrist of the assembling robot. After the attaching operation is automatically performed, the quality of the assembled state is automatically confirmed using the detection value of the force sensor. That is, when the assembling operation is completed, the hand is opened to release the work (first stage). The position of the hand at this time is undefined because it has been subjected to force feedback control based on the value detected by the force sensor. Next, after moving the hand to the taught work end point (second stage), the hand is closed and the workpiece is gripped (third stage). At this time, the position of the work is constant because the assembly work has already been completed.
Moreover, since the hand is at the end point of the work taught, that is, at a fixed position, the gripping position of the hand is also fixed. Then, in order to judge the quality of the assembling state by comparing with the force sense pattern at the time of teaching (that is, the change pattern of the detected value of the force sensor at the time of normal assembling), the assembling in which the hand is once taught is first performed. After retreating in the reverse direction of the operation (fourth stage), force information applied to the wrist is detected while the hand is moved forward in the same direction as the assembling operation (fifth stage). At this time, the force information (force sensor detection value) matches the force pattern at the time of teaching if it is correctly assembled, and does not match if it is improperly assembled (that is, abnormal). Value), the detected force information is compared with the force pattern at the time of teaching to determine whether or not they match (step 6). Thus, the quality of the assembled state can be accurately and automatically inspected using the detection value of the force sensor.

According to a second aspect of the present invention, there is provided a method for automatically assembling a workpiece by an assembling robot, wherein when the assembling operation is completed, prior to the first stage, the force sense information applied to the hand and the force at the time of teaching are determined. Since the hand is moved so that an error with the hand falls within an allowable range, the position of the work can be brought closer to the work position at the time of teaching, and the accuracy of the hand holding position in the second and third stages is improved, The inspection accuracy of the method according to claim 1 is improved.

In the method of automatically assembling a workpiece by the assembling robot according to the third aspect, after the sixth step, when it is determined that they do not match, a warning of an assembling failure is output. You can know the defective assembly.

In the method for automatically assembling a workpiece by the assembling robot according to the fourth aspect, in the second step, the hand is moved to the work end point while retracting so as not to interfere with the workpiece. The position of the work does not shift due to the hand colliding with the work, and the method according to the above-described claim 1 can be reliably performed to perform an accurate inspection.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Here, as an assembling operation, a description will be given of an example of an operation of inserting a duct (made of resin) into an instrument panel (made of resin) and assembling the duct.

FIG. 1 is an overall view showing an example of an assembling robot to which the method for automatically assembling a work according to the present invention is applied. The assembling robot 1 is, for example, a playback-type dual-arm robot having two arms (arms) like a human, and is fixed on a work table 2 by a predetermined jig 3. The work for assembling the duct 5 to the ment panel 4 is performed. Each arm of the double-arm robot 1 is an articulated arm by a servo motor direct drive system, and can be independently taught, and a force is applied to a wrist, which is a joint between the arm (arm) 6 and the hand (hand) 7. The sense sensor 8 is mounted (see FIG. 2). When actually assembling the duct 5 to the instrument panel 4, the dual-arm robot 1 grips and moves the duct 5 at two predetermined positions A, and moves the duct 5 to the insertion port 9 inside the instrument panel 4.
(See FIG. 3). As mentioned earlier, flexible products such as resin molded products originally have large differences in solids after manufacturing, and accuracy cannot be obtained. It is necessary to be able to perform assembling work without teaching. For this reason, work is performed while appropriately correcting the operation while feeling how the force is applied, that is, performing the work while performing force control by force sense to finely control the force of the assembling operation.

The force sensor 8 mounted on the wrist of each arm of the dual-arm robot 1 is, for example, a six-axis force sensor that handles six-dimensional information, such as a reaction force acting on a hand. The moment (force information) is directly detected. The six-dimensional force information includes, for example, loads and moments in the X, Y, and Z axial directions. The structure itself of the force sensor 8 is well known. In the present embodiment, as will be described later, the work of assembling the duct 5 to the instrument panel 4 is automatically performed by feeding back the detection value (force information) of the force sensor 8 to force control. I have to.

FIG. 4 is a block diagram of a robot control system for realizing the work automatic assembling method of the present invention. Since the control system of each arm of the dual-arm robot 1 is the same, here,
Only one arm (robot arm) is targeted.

As shown in FIG. 1, each robot arm (including a hand) 6 of the dual arm robot 1 is integrally controlled by a robot controller 10. The robot controller 10 includes a robot controller 11 that stores and controls the operation of the robot arm 6, a servo amplifier 12 that supplies driving power to a servo motor (hereinafter simply referred to as an axis motor) of each drive shaft of the robot arm 6, A force sense monitoring unit 13 for inputting and monitoring a detection value (force sense signal) of the force sensor 8 mounted on the wrist of the robot arm 6, a position correcting unit 14 for generating a signal for correcting the position of the robot arm 6, have. The work (instrument panel 4, duct 5) is carried into and out of the work table 2 and the teaching board 15 which is a remote control device for storing the required work in the robot arm 6 to the robot controller 11. Various sensors (not shown) such as a limit switch for detecting the fact are connected respectively. Further, a robot signal (for example, a data warning signal or disconnection detection) related to the robot arm 6 is also input / output to / from the robot controller 11.

The control of the basic operation of the robot arm 6 is the same as in the case of a normal playback robot.
Is operated to teach the actual assembling work, so that the order, position, and other information of the work are stored in the memory 16 in the robot controller 11. This teaching work is
In the case of the dual-arm robot 1, the operation is performed for both arms. The actual assembling work is performed by reading information such as the taught order and position as needed, and performing axis motor control and brake control via the servo amplifier 12,
Each stage of the operation is sequentially advanced in accordance with the preset order, condition and position. At this time, in the present embodiment, the operation is appropriately corrected while monitoring the detection value of the force sensor 8 as described later.

As described above, the force sense monitor 13 inputs and monitors the value detected by the force sensor 8. Specifically, a change in the detection value of the force sensor 8 when a normal assembling operation is taught to the robot arm 6 is stored in advance in the memory 17 in relation to time, for example (hereinafter, stored in the memory 17). The data of the force sensor detected value with respect to the time of the normal operation is referred to as a force pattern), and the force pattern in the memory 17 is reproduced by a synchronization signal from the robot control unit 11 and compared with the current detected value. And find their errors. Then, it is determined whether or not the obtained error is within a preset allowable range, and the result is output to the robot control unit 11 (if it is within the range) or the position correction unit 14 (if it is outside the range). During the correction operation, the reproduction of the force sense pattern is stopped. Since the force sense pattern stored in the memory 17 is a change in the detection value of the force sense sensor 8 when the assembling operation is actually performed successfully, that is, when a normal assembling operation is performed, the robot arm 6. The force sense pattern is sequentially reproduced while synchronizing with the movement of Step 6, and compared with the force sense sensor detection value (unassembled state) at the corresponding assembling operation stage at that time, so as to follow the force sense pattern. By applying the position correction, the work (instrument panel 4, duct 5) can be securely assembled even if it is not so accurately positioned.

The position correction section 14 generates a signal for correcting the position of the robot arm 6 as described above. The memory 18 of the position correction unit 14 stores the error between the detected value of the force sensor 8 and the value of the force sense pattern in the corresponding operation stage within the allowable range when the error is not within the allowable range. Data relating to the direction in which the robot arm 6 should be moved (hereinafter, referred to as an operation direction instruction table) is stored. The contents of the operation direction instruction table are set appropriately in advance by performing an operation experiment or the like. For example, if the load error in the X-axis direction exceeds the allowable range and is in a plus (+) state, the robot arm 6 is moved in a direction to keep the error within the allowable range, that is, in the minus (-) direction of the X-axis. The position correction unit 14 generates a correction signal indicating a direction in which the robot arm 6 should be moved by referring to the operation direction instruction table based on the determination result (which direction is NG) of the force sense monitoring unit 13, Output to the robot controller 11. As a result, the robot control unit 11 moves the robot arm 6 in the specified direction to control the degree of the applied force.

FIG. 5 is a flowchart showing the operation of the robot controller 10. Here, a flowchart in the case where the work (instrument panel 4, duct 5) is assembled by the double-armed robot 1 after a predetermined teaching operation is completed is shown. When the robot 1 reaches the assembly work start position and the program for the assembly work starts,
The robot control unit 11 moves the robot arm 6 via the servo amplifier 12 according to the program, and the force sense monitoring unit 13 sequentially reproduces the force sense pattern in the memory 17 while synchronizing with the movement of the robot arm 6, The input detection value of the force sensor 8 is monitored. That is, the input detection value of the force sensor 8 is compared with the value of the force sensor pattern at the corresponding stage to determine those errors, and it is determined whether or not the obtained error is within an allowable range (step S1, step S1). S2).

If the result of the determination in step S2 is that the error is not within the allowable range, the result of the determination is sent to the position corrector 14
Output to The position correction unit 14 generates a correction signal indicating a direction in which the robot arm 6 should be moved by referring to the operation direction instruction table in the memory 18 based on the determination result of the force sense monitoring unit 13 (which direction is NG). Then, the data is output to the robot controller 11. The robot controller 11 moves the robot arm 6 in the specified direction to control the degree of the applied force (steps S3 and S4). Then, it is determined whether or not the current stage of the program is the assembling work ending stage, that is, whether or not the assembling work is completed (step S5). If not, the process returns to step S1 and the error is within the allowable range. Repeat the correction operation until it stops.

If the result of the determination in step S2 is that the error is within the allowable range, the force sense monitoring unit 13 outputs a signal to that effect to the robot control unit 11. Accordingly, the robot control unit 11 reads the next stage of the program to move the robot arm 6 to the next operation (step S6), and proceeds to step S6. That is, the assembly work is continued until the assembly work is completed.

In this embodiment, when it is determined in step S5 that the assembling operation has been completed, a process for automatically judging the quality of the assembling state is performed.

First, in the present embodiment, the force sense monitoring unit 13 inputs the detection value of the force sensor 8 and compares it with the value of the force sense pattern at the end of the work to determine their errors. It is determined whether the error is within an allowable range (step S
7, Step S8). If the result of this determination is that the error is not within the allowable range, the same processing as steps S3 and S4 is performed, and the process returns to step S7. That is, the position correcting unit 14 determines the operation direction of the robot arm 6 with reference to the operation direction instruction table in the memory 18 and outputs the determined operation direction to the robot control unit 11. The robot controller 11 moves the robot arm 6 in the designated direction (step S
9, step S10). This correction operation is repeated until the error falls within the allowable range. That is, once the assembly operation is completed, the hand 7 is moved so that the force information (the detection value of the force sensor 8) applied to the hand 7 matches the force information at the time of teaching within an allowable range. Let it. Accordingly, the position of the work can be brought closer to the work position at the time of teaching, so that the accuracy of the gripping position when re-gripping the work in step S13 described later is improved, and the inspection accuracy is improved.

If it is determined in step S8 that the error is within the allowable range, the robot controller 11 opens the hand 7 to release the work (step S11). The position of the hand 7 at this time is undefined because it has been subjected to the force feedback control (steps S1 to S6) based on the force sensor detected value.

Next, the robot arm 6 is moved to move the hand 7 to the work end point taught earlier (step S12). The instructed work end point is a position where the insertion operation has been normally completed (a position where no correction is applied).
At this time, in this embodiment, the hand 7 is moved to the work end point while being retracted so as not to interfere with the work.
The evacuation route is set appropriately in advance. This prevents the hand 7 from hitting the workpiece during the evacuation and causing the position of the workpiece to be displaced, so that an accurate inspection can be performed.

Then, the hand 7 is closed and the work is gripped again (step S13). At this time, the assembling work has already been completed, and in this embodiment, steps S7 to S7 are performed.
In step S10, the work position after the end of the work is corrected to the same position as at the time of teaching, so that the position of the work is constant, and the hand 7 is at the work end point taught by the processing of step S12, that is, a fixed position. , The holding position A of the hand 7 is also constant.

Then, in order to judge whether the assembly state is good or not by comparing with a force sense pattern at the time of teaching (that is, a change pattern of a detection value of the force sensor 8 when the assembly is performed normally), the robot arm is first temporarily stopped. After moving the hand 7 to move the hand 7 backward in the reverse direction of the taught assembling operation, then, while moving the hand 7 forward in the same direction as the assembling operation (step S14), the force sense applied to the wrist The information is detected by the force sensor 8 and monitored by the force monitor 13 (step S15). If the force information at this time (the value detected by the force sensor 8) is correctly assembled, the force information matches the force pattern at the time of teaching stored in the memory 17 (that is, is constant), and the improper assembly is performed. If they do not match (that is, indicate an abnormal value), the detection value of the force sensor 8 is compared with the force pattern in the memory 17 to determine whether or not those change patterns match. (Step S1
6). If a match is found as a result of the determination, it is determined that the assembled state is good, that is, the duct 5 is firmly inserted into the instrument panel 4,
The inspection is completed, and the above series of assembling work is completed.

On the other hand, if it is determined in step S16 that there is no match, it is determined that the assembly state is defective, and a warning of an assembly failure is output as an inspection result (step S17). . Thereby, the worker at the site can actually know the defective assembly.

Therefore, according to the present embodiment, when the assembling operation is completed, the assembling operation is re-executed, and the detection value of the force sensor 8 at that time is compared with the force sense pattern in the normal operation. Therefore, the quality of the assembled state can be accurately and automatically inspected.

Further, since the force sensor 8 used for force control of the assembling work is also used as a sensor for inspecting the assembling state, it is possible to cope with the addition of a program without adding any parts. Therefore, it is not necessary to use a visual device as in the related art, and the configuration of the robot system including the inspection can be simplified, and the accuracy of the inspection is improved as compared with the case where the visual device is used.

Furthermore, since the force control by the force sensor 8 is basically used, the accuracy of the resin assembling work does not matter so much, and the accuracy as in the past can be used. Therefore, accurate positioning of the assembly work is not required.

In this embodiment, the work of inserting the duct (made of resin) into the instrument panel (made of resin) and assembling it is taken as an example. However, the application of the method of inspecting the assembled state according to the present invention is limited to that case. Of course not. For example, the present invention can be applied not only to the work of inserting and fitting, but also to the work of pushing an object with nails.

[0036]

As described above, according to the method for automatically assembling a workpiece by the assembling robot according to the first aspect of the present invention, the assembling operation is restarted when the assembling operation performed while correcting is completed. Since the execution is performed and the detection value of the force sensor at that time is compared with the force pattern at the time of teaching, the quality of the assembled state can be automatically and accurately inspected by judging whether or not they match. Can be.

According to the method for automatically assembling a workpiece by the assembling robot according to the second aspect, the workpiece position after the assembling operation can be made closer to the workpiece position at the time of teaching. Claim 1 wherein the accuracy is improved.
The inspection accuracy of the described method is improved.

According to the method for automatically assembling a workpiece by the assembling robot according to the third aspect, a warning of an improper assembling is output when it is determined that they do not match. Can be.

According to the method of automatically assembling a work by the assembling robot according to the fourth aspect, the hand is moved while being retracted so as not to interfere with the work when the hand is moved to the taught work end point. The position of the work does not shift due to the collision with the work, and the method according to the first aspect can be reliably executed to perform an accurate inspection.

[Brief description of the drawings]

FIG. 1 is an overall view showing an example of an assembling robot to which a method for automatically assembling a work according to the present invention is applied;

FIG. 2 is a diagram for explaining a mounting position of a force sensor.

FIG. 3 is a schematic view showing an example of an assembling operation.

FIG. 4 is a block diagram of a robot control system for realizing the work automatic assembling method of the present invention.

FIG. 5 is a flowchart showing the operation of the robot controller.

[Explanation of symbols]

 6: Robot arm (assembly robot) 7: Hand 8: Force sensor 10: Robot controller 11: Robot controller 13: Force monitor 14: Position corrector 15: Teaching board 16, 17, 18 ... Memory

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B25J 13/08 B23P 19/04

Claims (4)

(57) [Claims] 1. An assembling robot according to claim 1, wherein a force sensor attached to a wrist of the assembling robot has a detection value within a predetermined allowable range.
Work set while correcting the position of the arm of the standing robot
The step of performing the attaching operation, the step of opening the hand to release the work when the assembling operation to be performed while correcting is completed, and the position where the assembling operation is normally completed are taught in advance.
Hand that has completed the actual assembly
A step of moving the de, and step of holding the workpiece by closing the hand, a step retracting movement in the opposite direction of the assembling operation taught hand, while the hand is moved forward in the same direction as the operation with the set Detecting the force information applied to the wrist; comparing the detected force information with the force pattern at the time of teaching;
Judging the quality of the assembling state based on the presence or absence of the coincidence of the two. 2. When the assembling operation is completed, prior to the step of opening the hand and releasing the work, the hand is moved so that an error between force information applied to the hand and that at the time of teaching falls within an allowable range. 2. The method for automatically assembling a workpiece by an assembling robot according to claim 1, further comprising the step of: 3. After the step of comparing the detected haptic information with the haptic patterns at the time of teaching and judging the coincidence of the haptic patterns, outputs an alarm of an improper assembly when it is determined that they do not match. 2. The method for automatically assembling a workpiece by an assembling robot according to claim 1, further comprising the steps of: 4. The assembly robot according to claim 1, wherein in the step of moving the hand to the taught work end point, the hand is moved to the work end point while retracting so as not to interfere with the work. Automatic work assembly method by