JPH0227100B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a position correction device for a robot. Assembly, which has recently been put into practical use
An important issue for robots is how to quickly and skillfully perform fastening operations, parts insertion operations, etc. repeatedly without failure. For example, in the case of fastening work, an automatic screw tightening machine that automatically supplies screws can be gripped by a mechanical hand attached to the tip of a robot's movable part, or it can be attached directly to the tip of a robot's movable part.
It is conceivable to accurately position the tip of the automatic screw driver over the screw hole of the workpiece, and then lower the automatic screw driver vertically to perform the screw tightening work. However, in order to perform this work effortlessly and quickly,
It is natural to improve the repeatability of the robot, but if the screw hole position of the workpiece supplied to the robot's working position is not constant, the positioning of the tip of the automatic screwdriver, which is the working end of the robot, will not be accurate. Even then, the probability of failure increases. For example, when configuring a screw tightening work line using a robot, it is conceivable that the work flowing on the conveyor is temporarily stopped at the robot's work position and the screw tightening work is performed.
In this case, a stopping error of the workpiece becomes a problem, and if this stopping error occurs in millimeter units, it becomes difficult to fasten the workpiece. The above-mentioned stopping error will not be a problem if a high-precision positioning device is installed, but if a high-precision positioning device like the one described above is used for a relatively large workpiece such as an automobile instrument panel, for example. When trying to make one, not only did the equipment become large-scale, but the equipment costs were extremely high. Therefore, in recent years, attempts have been made to equip robots with a visual recognition function to visually recognize the positions of screw holes in the workpiece and correct the position of the tip of an automatic screw tightening machine. However, even with this method, there are disadvantages in that it takes too much time to process the image data from the TV camera with the current technology, and the screw hole position is in a narrow or deep part of the workpiece, and the color of the workpiece may vary. If there is not much difference between the color of the screw hole (black), it is difficult to recognize, and the entire device is expensive, so it is not very practical. This invention was made in view of the above-mentioned background, and it is possible to quickly correct positional deviation errors between the working position of the robot, such as the aforementioned screw hole, and the working tool of the robot using a relatively simple device. The purpose is to make it possible to absorb corrections. In order to achieve the above object, the present invention is arranged such that the relative positional relationship of the robot with respect to the work object is constant, and a mark is made at a predetermined position corresponding to the work position of the robot on the work object. a copying base; an arm that is attached to the robot and rotates in a plane parallel to the surface of the copying base; and a rotating shaft that is attached to the tip of the arm and extends in a direction toward the surface of the copying base; a double-headed head having a work tool for performing a predetermined work at the work position and a detection body for detecting the mark; a synchronizing means for matching a working position and a relative positional relationship with the mark; a plurality of detecting units disposed on the detecting body in a fixed arrangement in a region narrower than the mark and each detecting the mark; The moving direction and amount of movement of the power tool are uniquely determined in advance in order to guide more detecting parts into the mark according to the position and number of detecting parts in the detecting body when detecting the presence of the mark. a position correction data storage means storing position correction data consisting of a data group; and when the double-headed working tool is positioned at a target position near the working position,
selection means for selecting position correction data corresponding to the position and number of detection parts on the detection object in which the presence of the mark has been detected from among a data group stored in the position correction data storage means; drive means for driving the movable part of the robot based on the selected position correction data; and selection of position correction data by the selection means until all the detection parts of the detection body are positioned within the mark. A position correction device for a robot, comprising a position correction control means for repeatedly driving the movable part by the drive means and correcting the position of the working tool. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing a fastening operation performed by a horizontal articulated robot to which the present invention is applied. In the figure, a horizontal articulated robot 1, also called the SCARA type, has a column 3 fixed upright on a base 2, and an elevating section 4 that moves up and down in the Z direction with respect to the column 3. , a first arm 5 that pivots in the direction of arrow θ ₁ on the x-y plane with respect to the lifting unit 4, and a first arm 5 that pivots in the direction of arrow θ ₂ on the x-y plane with respect to this first arm 5. The second arm 6 and the end plate 6a of this second arm 6
The wrist part 8 is attached to a shaft part 7a of a double-headed head (schematically shown in FIG. 1), which will be described later, via a bearing, and the shaft part 8 is rotatably attached thereto. The elevating unit 4 is operated by the motor M ₁ attached to the column 3 through the speed reducer GB ₁ and the rotation inside the column 3.
The first arm 5 is driven in the direction of arrow Z via a linear motion conversion mechanism, and the first arm 5 is driven by a motor attached to the lifting section 4.
It is driven by M ₂ in the direction of arrow θ ₁ via reduction gear GB ₂ . Further, the second arm 6 is driven in the θ ₂ direction by a motor M ₃ attached to the first arm 5 via a speed reducer GB ₃ . The arms 5 and 6 are a copying base 1 which will be described later.
1 and rotates in a plane parallel to the surface 11a of the object. Note that PG ₁ to PG ₃ are pulse generators attached to the output shafts of the respective motors M ₁ to _{M 3} , and detect the movement positions of the elevating section 4 and the first and second arms 5 and 6, respectively. In addition, a toothed pulley PU ₁ is rotatably attached to the connecting shaft of the elevating part 4 and the first and second arms 5 and 6.
A toothed belt is connected between the PU ₂ and the toothed pulley PU ₃ fixed around the shaft portion 7a of the double-headed head 7.
VT ₁ and VT ₂ are tensioned, so that the first,
Even if the second arms 5 and 6 turn in the directions of arrows θ ₁ and θ ₂ , the posture of the double-headed head 7 remains constant. In other words,
The toothed belts VT1 and VT2 are provided with synchronizing means for matching the working position (hole 10b) and the relative positional relationship between the mark MRK and the double-headed head 7, which will be described later, in response to the turning movement of the arms 5 and 6. It consists of This horizontal articulated robot 1 is transported from the direction of arrow Y by a workpiece transport conveyor 9 disposed in front of the robot 1, and stops at the position shown in the figure. Tighten the screws on the glow box slide 10a and the instrument panel (not shown). Each instrument panel 10 flowing on the workpiece conveyor 9 is individually fixed to a work jig 11 on the upstream side, and this work jig 11 is, for example, conveyed by the free-flow type workpiece conveyor 9. and air cylinder SL in the position shown.
It is stopped by a stopper ST which moves forward and backward in the direction of arrow X. However, in order to keep the working jig 11 in a substantially constant stopping position, the conveyor 9 is provided with a stopping reference plane (not shown). On the upper surface 11a of the work jig 11, there are holes 10b for attaching the glow box slide 10a, which is the true working position of the robot 1 in the instrument panel 10 determined from the design drawing, and an instrument panel that does not appear in the drawing. Marks with a diameter slightly larger than the size of each hole are placed at designated positions corresponding to the mounting holes.
MRK has been applied. That is, this upper surface 11a functions as a copying base, and since the instrument panel 10 is fixed to the work jig 11, each hole in the instrument panel 10 and each mark on the upper surface 11a
The relative positional relationship with MRK is constant. The glow box slide 10a and an unillustrated instrument panel are arranged upstream of the conveyor 9 so that the respective holes and the holes on the instrument panel 10 side are in phase with each other. Further, in this embodiment, the instrument panel 10 is fixed to the work jig 11 on the upstream side, but for example, the instrument panel 10 may be clamped and transported as it is on the work conveyor 9, and the instrument panel 10 may be ment panel 1
0 stops at the position shown in the figure, the work jig 1
A copying base body configured in the same manner as the top surface 11a of FIG. 1 may be moved from the side of the conveyor 9 toward the instrument panel 10 and stopped at a predetermined position. Then, the instrument panel 10 and the work jig 1 are installed by the stopper ST as shown in FIG.
Since there is a possibility that an error may occur in the stopping position of robot 1, one automatic screw tightening machine 12 in the double-headed head 7 attached to the tip of the robot 1 is used.
(described later) is moved to a target position obtained in advance by teaching, for example, when the other sensing head (detection object) [described later] 13 of the double-headed head 7
Marks on the top surface 11a of the work jig 11 by
MRK is detected, and based on the detection result, the instrument panel 1 is
This is intended to absorb the positional deviation error between the hole on the 0 side and the tip of the automatic screw tightening machine 12. In addition to the positional deviation error caused by the above-described stop error, errors in teaching data for each instrument panel 10 can also be absorbed. Next, the structure of the double-headed head 7 will be explained with reference to FIGS. 2 and 3. First, in FIG. 2, an automatic screw tightening machine 12 is fixed to a guide bar 14 that is slidably attached to one U-shaped support portion 7b of the double-headed head 7 in the direction of arrow Z. This screw tightening machine 1
The automatic screw tightening machine 12 is raised and lowered by moving the automatic screw tightening machine 2 along with a guide bar 14 in the direction of the arrow Z using an air cylinder 15 fixed to the support part 7b. When the tip of the automatic screw tightening machine 12 is positioned over, for example, a hole 10c for installing an instrument panel in the instrument panel 10, an air cylinder 15 is activated by a command from a control section, which will be described later.
The tip descends toward the hole 10c, and the tip reaches the hole 10c.
When it comes into contact with the upper surface of the hole 10c, the tapping screw supplied from the screw supply port 12b is screwed into the hole 10c by a bit rotated by an internal motor. Also, the other support portion 7c in the double-headed head 7
The head 13a has a built-in detection circuit which will be described later.
, a base portion 13b, and a rod portion 1 for attaching the sensing portion.
A sensing head 13 consisting of a sensor 3c, a sensing section 13d, etc. is attached. The sensing portion 13d of the sensing head 13 has a structure as shown in FIG. That is, four detection parts 13f _{1 to} 13f ₄ for detecting the presence of the mark MRK on the upper surface 11a of the work jig 11 are respectively attached to the disk 13e smaller in diameter than the mark MRK attached to the tip of the rod 13c. 1
The detection parts 13f 1 to 13f 4 have truncated cone-shaped relief holes 13g provided at the tips of the detection parts 13f ₁ to 13f ₄ , which are in contact with the outer circumferential circle of the detection parts 3e and distributed in a fixed arrangement so as to be symmetrical to each other. Light receiving end face portions 16a _{1 to} 16a 4 of four optical fibers 16 molded in detection portions 13f 1 to 13f ₄ , respectively, are fixed to the bottoms _of the optical fibers ₁ to 13g4 _, respectively. These four optical fibers 16 are connected to the second
Head 13 of sensing head 13 as shown in the figure.
It is guided to a detection circuit provided inside a. In addition, automatic screw tightening machine 1 with double head 7
2 and the respective tips of the sensing head 13, as shown in FIG.
If the tip of the sensing head 13 is located directly above the mark MRK, the tip of the automatic screw tightener 12 will be aligned with the hole 10b.
Or it will be located directly above 10c. The detection circuit includes, for example, four circuit sections configured as shown in FIG. In this circuit section, the phototransistor PT receives the light transmitted through the optical fiber 16, and causes a current to flow through the resistor R in accordance with the intensity of the light. Then, the voltage _VX generated across this resistor R
For example, the CMOS trigger buffer SH
The circuit constants are set so that the output e becomes "H" or "L" depending on whether the voltage _VX is larger or smaller than the input threshold level _VTH . For example, the diameter d ₁ of the disk 13e, the diameter of the mark MRK
d ₂ and the opening diameter d ₃ of the escape holes 13g ₁ to 13g ₄ , for example, if _a size relationship is set as shown in FIG. Output e when looking more than 2/3 of the way
is set to "L", and set to "H" otherwise. Note that the color of the mark MRK is, for example, black, and the color of the upper surface 11a of the work jig 11 is a color lighter than black, for example, white. This will reduce the trigger buffer
When the output e of SH is “L”, the output transistor Tr
is off, the output _P4 becomes "1" by the constant current source CI, and when the output e is "H", the output transistor Tr is turned on and the output _P4 becomes "0". In the same circuit, diode D is used to prevent reverse connection, Zener diode ZD ₁ is used to prevent backflow, and Zener diode ZD ₂ is used to absorb surge. Therefore, by checking whether the output _P4 is "1" or "0", it is possible to know whether the light-receiving end surface 16a of the optical fiber 16 within the relief hole _13g4 has detected the presence of the mark MRK. be able to. Hereinafter, as shown in FIG. 6, the detection units 13f ₁ to 1
_3f4 are respectively referred to as _Q1 to _Q4 , and the outputs of the corresponding detection circuit sections are referred to as _P1 to _P4 . FIG. 7 is a control block diagram of the horizontal articulated robot 1 of FIG. 1 including the robot position correction device according to the present invention. Note that the deviation counter 21, drive section 22, speed detection section 23, and position counter 24 from the pulse distributor 20 in FIG. 7 are a digital DC servo system of the motor _M1 that drives the lifting section 4 in FIG. Since the digital DC servo systems of the other first and second arms 5 and 6 are configured in exactly the same way, illustration thereof is omitted. First, the basics for driving and controlling the robot will be explained. In the same figure, the movement data calculation unit 17 calculates a position indicating the target position of the tip of the automatic screw tightening machine 12 shown in _FIG . Based on the data and the current position data of the elevating portion 4 and each part of the first and second arms 5 and 6 stored in the current position register 25, the amount of movement of the elevating portion 4 and the first and second arms 5 and 6 are determined. , and outputs the calculation results to the pulse distributor 20. Note that the memory 19 stores a plurality of position data, which is the result of determining the positions of the holes 10b and 10c (FIG. 2) in the instrument panel 10 of FIG. 1, for example, by teaching, data on the origin position of the robot, etc. are stored and read out according to a predetermined work order. However, with these position data, there is no guarantee that the automatic screw tightening machine 12 in the double-headed head 7 at the tip of the robot 1 can be accurately positioned over the holes 10b and 10c of the instrument panel 10, which have different stopping positions. However, it is possible to position it at least in its vicinity. The pulse distributor 20 forms a pulse signal that expresses the amount of movement (angle) of each part by the number of pulses based on the calculation result from the movement data calculation unit 17, and distributes each pulse signal to each digital DC servo system. It is distributed and output to the deviation counter 21. In digital DC servo system, deviation counter 21
The rotation of the motor M1 is controlled via the D/A converter and servo amplifier in the drive section 22 according to the count output of the motor _M1 , and the outline of the control of its speed and position (amount of rotation) is as follows. It's like this. That is, when the motor _M1 should be rotated in the forward direction, the pulse signal from the pulse distributor 20 is sent to the up count terminal U of the deviation counter 21, and the motor is
A pulse signal fed back from the pulse generator _PG1 operated by _M1 is inputted to the down-count terminal D of the deviation counter 21 via a switching circuit (not shown). In this way, the count value of the deviation counter 21 will be kept at a speed determined by the period of the pulse signal and the output characteristics of the pulse generator PG ₁ until a certain period of time has elapsed since the motor M ₁ started rotating. After the predetermined time has elapsed, the count value of the deviation counter 21 is kept constant. When the pulse signal input to the up-count terminal U of the deviation counter 21 disappears, the count value is decremented by the pulse signal from the pulse generator _PG1 . Using the count value of the deviation counter 21 that changes in this way as a speed reference value, this speed reference value and the actual speed value from the speed detection section 23 (pulse generator
(obtained by F/V converting the pulse signal from PG ₁ ), and the drive unit 22 performs speed feedback control so that the two match. In this way, when the deviation counter 21 starts counting the pulse signals from the pulse distributor 20, the motor _M1 starts to rotate, and the deviation counter 2
As the count value of M1 increases, remains constant, or decreases to zero, the motor _M1 rotates by the number of rotations corresponding to the number of pulses and then stops, thereby controlling the position (rotation amount). However, motor M ₁
If the amount of rotation is greater than or equal to a predetermined value, the following correction is performed. In other words, if an incremental type pulse generator PG ₁ is used, the motor M ₁
The direction of rotation can be detected by distinguishing the phase of its output pulse signal. Therefore, the above-mentioned switching circuit is provided with this discrimination function, and when the motor M ₁ is rotating in the forward direction, the pulse signal from the pulse generator PG ₁ is sent to the down count terminal D of the deviation counter 21 as described above, and when the motor M 1 is rotating in the reverse direction, the pulse signal is sent to the down count terminal D of the deviation counter 21. The pulse signals are respectively input to the up count terminals U. By doing this, the count value of the deviation counter 21 will not become zero when the amount of rotation is less than the predetermined value, so the count value will become zero by rotating the motor _M1 further in the positive direction. If the amount of rotation exceeds the predetermined value, the count value of the deviation counter 21 is a negative value, so the motor _M1 is rotated in the opposite direction and the pulse generator is adjusted in accordance with the rotation. The negative count value is incremented in the positive direction by the pulse signal output from the generator _PG1 , so that the count value becomes zero. As a result, the motor _M1 eventually rotates by the number of rotations corresponding to the number of pulses of the pulse signal from the pulse distributor 20 and then stops. The current position register 25 includes three position counters that count the apparent amount of rotation (forward rotation amount - reverse rotation amount) of each motor M ₁ to _{M 3} whose drive is controlled as described above from the time of starting. The count output from 24 is stored, so that current position data indicating how far each part of the robot 1 has moved from the origin position is always held. Each of these position counters 24 also detects the phase of the pulse signal from each pulse generator PG ₁ to _{PG 3} and sends the pulse signal during forward rotation of the motors M ₁ to _{M 3} to the up count terminal. A switching circuit for inputting a pulse signal at the time of reverse rotation to the down count terminal is connected to each input side. As described above, the tip of the automatic screw tightening machine 12 on the double-headed head 7 attached to the wrist portion 8 of the robot 1 shown in FIG.
It can be positioned near (or even coincident with). Note that the positioning of the automatic screw tightening machine 12 also positions the sensing head 13 with respect to the mark MRK. Then, the positioning error is determined based on how the detection units Q ₁ to _{Q 4} in the sensing head 13 positioned as described above detect the mark MRK. Next, parts related to this invention will be explained.
In FIG. 7, the detection circuit 26 includes four detection circuit sections shown in FIG. 4, including detection sections _Q1 to _Q4.
The above-mentioned outputs P ₁ to _{P 4} are output according to the detection results. The discrimination circuit 27 receives outputs P ₁ to _{P 4} from the detection circuit 26 as binary data through a gate circuit 28 opened by a gate signal G ₂ to be described later, and outputs them as shown in Table 1. The signals S ₀ to S ₁₃ are output under such conditions. In Table 1, for example, when Q ₁ to _{Q 4} are off, it means that all of the detection units Q ₁ to _{Q 4} have not detected the presence of the mark MRK, and when Q ₁ is on, it means that the detection unit Q Only ₁ indicates that the presence of mark MRK is detected.

[Table] Also, in Table 1, Q ₁ and Q ₃ are on or Q ₂ ,
_The reason why there is no state in which Q _{4 is} turned on is because, as is clear from FIG. This is because it is impossible to detect it. It should be noted that the discrimination circuit 27 that operates in this manner can be easily made using, for example, a known binary-hexadecimal conversion circuit. The control unit 29 is in charge of overall control of the robot, including control according to the present invention. That is, when the control section 29 receives the robot start command _ST shown in FIG. 8A, it first outputs the gate signal _G1 shown in FIG.
The gate circuit 18 is opened, thereby outputting position data indicating the first target position from the memory 19 to the movement data calculating section 17. After receiving the position data, the movement data calculation unit 17 calculates the movement data of each part of the robot 1 based on the falling timing of the gate signal _G1 as shown in FIG. The result is output to the pulse distributor 20. Then, in response to the calculation result, the pulse distributor 20 distributes and outputs a pulse signal according to the calculation result to each deviation counter 21 of each digital DC servo system at the timing shown in FIG. 8D. As a result, positioning control is performed according to the input pulse signal by the action of the digital DC servo system described above, so that the tip of the automatic screw tightening machine 12 at the double-headed head 7 attached to the wrist portion 8 of the robot 1 is , instrument panel 10
For example, it is positioned at a target position near the first hole 10c. In the above explanation, the robot 1 is suddenly moved from the origin to the first target position, but in reality, multiple relay points are set between the two to limit the movement trajectory of the robot 1. There is. Next, when the pulse distributor 20 finishes distributing the pulse signal, a distribution end signal _PE shown in FIG. Upon receiving this distribution end signal _PE , the control section 29 outputs a gate signal _G2 as shown in FIG. 8 to the gate circuit 28, thereby opening the gate circuit 28. When this gate circuit 28 opens, the outputs P ₁ to _{P 4} corresponding to the hole detection status of the detection parts Q ₁ to _{Q 4} of the sensing head 13 in the double-headed head 7 are sent to the detection circuit 26.
The signals S 0 to S 13 are outputted to the discrimination circuit 27 and subjected to the discrimination described above, whereby one of the signals S ₀ to _{S 13} is inputted to the control unit 29 at the timing shown in FIG. 8G. When the control unit 29 receives this signal and the signal is S ₀ , since none of the detection units Q ₁ to _{Q 4} has detected the mark MRK, it considers that the position cannot be corrected and sends an abnormal signal.
Outputs NG and performs abnormality processing such as stopping the operation of the robot 1. Further, if the input signal is S ₁ to S ₁₂ , one of the corresponding selection signals T ₁ to _{T 12} is selected by the readout circuit 30.
Output to. The selection readout circuit 30 selects one of the registers RST1 to _RST12 storing position correction data indicating the moving direction and amount of movement of the tip of the sensing head 13, respectively, in accordance with the selection signals _T1 to T12.
The position correction data is transferred from the selected register to the eighth register.
The data is output to the movement data calculation unit 17 at the timing shown in FIG. The relationship between the contents of the position correction data stored in the registers RST1 to RST12 and the selection signals _T1 to _T12 is set as shown in Table 2, for example.

【table】

[Table] The reason for setting as shown in Table 2 is that, for example, as shown in Figure 9A, only the detection part Q ₄ is marked.
When detecting the presence of MRK, if the sensing head 13 is moved a distance l ₁ in the direction of the detection part Q ₄ (arrow direction), the detection parts Q ₁ and Q ₂ will be moved as shown in FIG.
starts to detect the presence of mark MRK, and from this state the center direction of detection parts Q ₁ to _{Q 2} (in the direction of the arrow)
If the sensing head 13 is moved a distance l ₂ to
As shown in Figure C, detection parts Q ₁ , Q ₃ , and Q ₄ are marked.
This is because the presence of MRK will be detected. Furthermore, if the sensing head 13 is moved a distance l ₃ in the direction of the detection section _Q4 (in the direction of the arrow) from the state shown in FIG.
This is because Q ₁ to _{Q 4} will detect the presence of mark MRK. Therefore, by setting as shown in Table 2, one of the four detection units Q ₁ to _{Q 4} can be set as the mark MRK.
If the presence of
All of Q ₁ to _{Q 4} now detect the presence of mark MRK, and if two of the detection parts Q ₁ to _{Q 4} detect the presence of mark MRK, repeating the position correction twice will cause the 9th detection part to detect the presence of mark MRK. The result will be as shown in Figure D. Further, if the three detection units Q ₁ to _{Q 4} detect the presence of the mark MRK, the position shown in FIG. 9D will be obtained with one position correction. Returning to FIG. 7, if the signal input from the discrimination circuit 27 to the control unit 29 is _S13 , the gate signal _G1 shown in FIG. Therefore, position data for performing the screw tightening work is read out from the memory 19, and the position data is output to the movement data calculation section 17. Based on the above-mentioned premise, the flow of the control operation executed by the control section 29 will be explained with reference to the flowchart of FIG. 10. STEP 1 The automatic screw tightening machine 12 in the double-headed head 7 attached to the wrist portion 8 of the robot 1 as described above is moved to the target position by teaching. STEP 2 When the tip of the automatic screw tightening machine 12 is located at the target position, the signal from the discrimination circuit 27
Based on S ₀ to S ₁₃ , check how many of the detection units Q ₁ to _{Q 4} have detected the presence of marks MRK, and if none has been detected, output an abnormal signal NG and perform abnormal processing. . 1 to 3 marks from detection part Q ₁ to _{Q 4}
If the presence of MRK is detected, the readout circuit 30 selects one of the selection signals _T1 to _T12 .
If the presence of all four marks MRK is detected, the gate signal _G1 is output to the gate circuit 18 and the process proceeds to STEP 4. STEP3 Selection signal output in STEP2
The position correction data shown in Table 2 read out from any one of the registers RST1 to _RST12 selected by any one of _T1 to T12 is output to the movement data calculation unit 17, thereby performing the above-mentioned movement. Data calculation section 1
7. Through the action of the pulse distributor 20 and the digital DC servo system of each part of the robot,
The position of the tip of the sensing head 13 is corrected. Then, the loop of STEP 3 and STEP 2 is repeated, and when all of the detection units Q ₁ to Q ₄ detect the presence of the mark MRK, the process exits from the loop and proceeds to STEP 4. STEP 4 Since all of the detection parts Q ₁ to _{Q 4} of one of the sensing heads 13 in the double-headed head 7 have detected the presence of the mark MRK, the tip of the sensing head 13 (specifically, the disk 13e) is completely marked.
It is located at the top of MRK. Therefore, the tip of the other automatic screw tightening machine 12 in the double-headed head 7 is completely visible in the hole 10c of the instrument panel 10, and screw tightening is possible. Therefore, an operating signal is sent to the electromagnetic switching valve (not shown) that controls the air cylinder 15 shown in FIG. do the work. STEP 5 It is monitored whether or not the screw tightening work in STEP 4 has been completed, and when it is completed, the automatic screw tightening machine 12 is raised and the process proceeds to STEP 6. Note that methods for monitoring whether or not the screw tightening work has been completed include detecting the torque applied to the bit of the automatic screw tightening machine 12, or simply measuring time using a timer. Conceivable. STEP 6 Check whether the screw tightening work for all the holes 10c and 10b in the instrument panel 10 is completed. If not, return to STEP 1 and repeat the above operation, and if completed, STEP 7.
Proceed to. Note that the target positions to be processed in STEP 1 from the second time onwards are sequentially read out from the memory 19 corresponding to each hole 10c, 10b of the instrument panel 10. STEP 7 Instrument panel 10 on conveyor 9 stopped at the working position of robot 1
Since all the screw tightening work has been completed, the robot 1 is returned to the origin and waits until the next work timing.
The air cylinder SL shown in FIG. 1 is driven to retract the stopper ST and the instrument panel 10 whose work has been completed is flown downstream. In addition, in FIG. 7, the discrimination circuit 27, the control section 29, the selection readout circuit 30, and the register RST1
~RST 12 constitutes position correction amount determining means, and movement data calculation section 17, pulse distributor 20, current position register 25, and each digital DC servo system constitute position correction control means. Further, modifications of the above embodiment are listed below. (b) As shown in Fig. 11, four detection parts Q ₁ ~
A new detection part _Q5 may be provided at the center of _Q4 , and the screw tightening work may be started when this detection part _Q5 detects the presence of the mark MRK. In this case, the accuracy is lower than in the above example, but
Since the center of the tip of the automatic screw tightening machine 12 can be seen into the hole 12b or 12c, screw tightening is possible. (b) The number of detection parts may be any number as long as it is two or more,
For example, the number may be seven as shown in FIG. In this case, the diameter d ₄ of the disk 13e is marked
The diameter is a little less than twice the diameter d ₂ of MRK, and three of the seven detecting parts are inscribed in the same circle as the mark MRK. And one of the detection parts is marked MRK.
If the presence of is detected, l ₄ = d ₄ /2 - d ₃ /2 (d ₃ : diameter of the detection part) in the direction of the detected detection part.
and two of the detection parts are marked
If the presence of MRK is detected, if you move the two detecting parts that have been detected by the distance l ₄ in the direction of the center, the center detecting part will always detect the presence of mark MRK, and Therefore, screw tightening work can be performed without failure. (C) In the above embodiment, the present invention was applied to the work of fastening glow box slides and instrument panels in automobile instrument panels, but the invention can be applied to the fastening work of any workpiece in exactly the same way. Applicable. Incidentally, in the case of tightening a nut on a stud bolt, for example, in the fastening work, a nut runner may be attached to the double-headed head 7 instead of the automatic screw tightening machine 12. (d) In addition to the fastening work, for example, a pin insertion work can be considered, but in this case as well, a chuck or mechanical hand for grasping the pin may be attached to the double-headed head 7 instead of the automatic screw tightening machine 12. (e) In the above embodiment, the upper surface 11 of the work jig 11
Instead of the mark MRK made on a, a hole may be drilled and the hole may be used as a mark. (f) In the above embodiment, an example was described in which the present invention was applied to a three-axis horizontal articulated robot.
The invention is not limited to this, and can be similarly applied to robots with any axis configuration. As explained above, according to the present invention, positional deviation errors between the robot's working position and the robot's work tool, such as a screw hole, can be corrected and absorbed at high speed with a relatively simple device, so that the robot can be produced easily. It has a great effect when installed on the line.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a fastening operation performed by a horizontally articulated robot to which the present invention is applied;
The figure is an enlarged side view showing the configuration of the double-headed head in Figure 1, Figure 3 is a sectional view and bottom view showing the structure of the tip of the sensing head in the double-headed head, and Figure 4 is the detection shown in Figure 3. FIG. 5 is an explanatory diagram showing the size relationship between the disk in the sensing head, the detection part and the mark, and FIG.
FIG. 7, which is a diagram for defining the names of the detection units, shows the first detection unit including the robot position correction device according to the present invention.
A block diagram showing an example of a control device for a horizontally articulated robot shown in FIG.
D is a diagram for explaining the outline of position correction, and 1st
FIG. 0 is a flowchart showing the control operation executed by the control section in FIG. 7, and FIGS. 11 and 12 are explanatory diagrams showing other configuration examples of the detection section in the sensing head, respectively. 1... Horizontal articulated robot, 7... Double-headed head, 9... Parts conveyor, 10... Instrument panel, 10a... Glove box slid, 10b, 10c... Hole, 12... Automatic screw tightening machine, 13...sensing head (detection object),
13g ₁ to 13g ₄ ... escape hole, 16 ... optical fiber, 16a ₁ to 16a ₄ ... light receiving end face section, 17 ... movement data calculation section, 20 ... pulse distributor, 21 ...
... Deviation counter, 22 ... Drive section, 23 ... Speed detection section, 24 ... Position counter, 25 ... Current position register, 26 ... Detection circuit, 27 ... Discrimination circuit, 29 ... Control section, 30 ... ...selective readout circuit,
M ₁ to M ₃ ... Motor, PG ₁ to _{PG 3} ... Pulse generator, Q ₁ to _{Q 5} ... Detection section, RST1 to RST1
2...Register.

Claims (1)

[Scope of Claims] 1. A copy base body arranged so that the relative positional relationship with respect to the work object of the robot is constant, and a mark is provided at a predetermined position corresponding to the work position of the robot on the work object; an arm that is attached to the robot and rotates in a plane parallel to the surface of the copying base; and an arm that is attached to a rotation shaft that is provided at the tip of the arm and extends in a direction toward the surface of the copying base; a double-headed head having a work tool for performing a predetermined work and a detection body for detecting the mark; and when the arm turns, the double-headed head is rotated in response to the turning movement, and the double-headed head is moved between the work position and the work position. synchronizing means for matching the relative positional relationship with the mark; a plurality of detecting units disposed on the detecting body in a fixed array in a distributed manner within an area narrower than the mark, each detecting the mark; and detecting the presence of the mark. From a data group of the movement direction and movement amount of the power tool that is uniquely determined in advance to guide more detection parts into the mark according to the position and number of detection parts in the detection object at the time of detection. a position correction data storage means storing position correction data, and a position and number of detection parts on the detection body that detect the presence of the mark when the double-headed work tool is positioned at a target position near the work position; selecting means for selecting position correction data corresponding to the position correction data from a data group stored in the position correction data storage means; and controlling the movable part of the robot based on the position correction data selected by the selection means. a driving means for driving the power tool; and repeating the selection of position correction data by the selection means and the driving of the movable part by the driving means until all detection parts of the detection body are positioned within the mark, and 1. A position correction device for a robot, comprising a position correction control means for performing position correction.