JP2552743B2 - Robot controller - Google Patents

Description

The present invention relates to an industrial robot, and more particularly to a robot controller capable of automatically teaching a motion locus. The device of the present invention is suitable for application to a robot that performs polishing work.

"Prior Art" In general, when a robot is moved along a predetermined locus to perform a polishing work, for example, as shown in JP-A-60-20858, a sensor is provided at the tip to detect the pressing force of a grindstone. , The work start point and work end point of the work to be polished, and a predetermined position on the line connecting the two points are brought into contact with each other by applying a constant pressing force, coordinate data is input, and the coordinates are entered. Based on the data, linear interpolation or circular interpolation is selected according to the shape of the workpiece, interpolation data is created, and teaching is completed. After that, the grindstone was moved based on the created teaching data, and the polishing operation was performed while correcting the locus so that a constant pressing force was applied to the grindstone.

[Problems to be Solved by the Invention] By the way, in the above teaching, if the workpiece is planar, the line between the work start point and the work end point is linearly interpolated between these two points. It is not necessary to input the coordinate data of the points for interpolation on the connecting line. However,
In the case of a curved surface, even when simple circular interpolation is used, the coordinates of a plurality of interpolation points are stored in order to accurately determine the curvature, and the operator's teaching There was a problem that the load increased.

The present invention has been made to solve the above problems, and an object of the present invention is to automatically teach a motion trajectory conforming to actual machining at a small number of points regardless of whether a workpiece is a curved surface or a flat surface. It is to provide a robot control device capable of performing the above.

[Means for Solving the Problem] In order to achieve the above object, in the present invention, as shown in FIG. 1, the tool 27 attached to the tip of the robot 10 is biased in a certain direction with a predetermined pressing force. Floating cylinder device 20 to hold, distance sensor 28 for detecting the stroke amount of the floating cylinder device 20, and its distance sensor
From the output of 28, the NG discrimination means 1 for discriminating that the stroke amount deviates from the predetermined target value by the predetermined threshold value or more and outputting the NG signal, and the teaching point storage means 2 for storing the target motion locus of the robot 10 as the teaching point. And a traveling means 3 that interpolates between the teaching points to cause the robot 10 to travel on a target motion locus, and an interpolation point obtained by interpolating between the teaching points whether or not the NG signal is generated during the traveling. NG section storage means 4 for storing each section divided by, and correction means 5 for correcting the teaching point so as to move the interpolation point of the section where the NG signal is generated in the direction to make the stroke amount proper. Until the NG signal is not generated in all the sections, the traveling means 3, the
Provided is a robot control device comprising: an NG section storage means 4 and a repeating means 6 for repeatedly executing the correcting means 5.

[Operation] In the robot control device configured as described above, first, each teaching point is stored in the teaching point storage means 2 by rough teaching. Next, the tool 27 is actually used as a model base material 50.
The interpolation point obtained by interpolating the above-mentioned teaching point by running the robot 10 in a state of being in contact with is corrected.

That is, if the motion locus interpolated from the teaching point has a portion that is not appropriate for the shape of the base material 50, the stroke amount of the floating cylinder device 20 fluctuates at that portion and deviates from the predetermined threshold value. Inappropriate locations outside the predetermined threshold are treated as NG sections for each section corresponding to the interpolation point, and the NG section storage means 4
And the interpolation point of the section is corrected by the correction means 5 after the traveling of the motion locus is completed.

Then, the second motion is performed based on the new motion locus based on the corrected interpolation point, and thereafter, the robot 10 is operated until the stroke amount falls within the predetermined threshold value in all the sections.
And the correction of each teaching point are repeated.

Therefore, the teaching point taught first roughly is such that the tool 27 contacts the base material 50 with a predetermined pressing force and the stroke amount of the floating cylinder device 20 becomes a constant value within a predetermined threshold value over the entire operation locus. , Corrected by automatic operation.

[Examples] Examples of the present invention will be described with reference to the drawings. FIG. 2 is a perspective view showing the robot 10. This robot is a multi-joint type robot having 6 degrees of freedom, and performs polishing work with a rotary grindstone 27 attached to the end of the arm. The work piece is an automobile frame, and is used to perform a polishing work to smoothly finish a bead portion obtained by arc-welding a joint portion between a pillar and a roof.

The structure of the robot will be described. A trapezoidal swivel base 12 is rotatably supported on a fixed base 11 in a horizontal plane about a vertical first axis A1, and swung by a first shaft drive motor M1. On the swivel base 12, the first arm 13
Is swingably supported about a horizontal second axis A2,
It is oscillated by an axis drive motor M2. The first arm
A cylindrical second arm 14 is provided on the third axis line 13 which is horizontal.
It is swingably supported around A3 and is swingably driven by a third shaft drive motor M3 (not shown). At the tip of the second arm 14, the twist wrist 15 has a fourth axis centered on the second arm 14.
It is rotatably supported around A4 and is driven to rotate by a fourth shaft drive motor M4. A bend list 16 is supported on the twist list 15 so as to be rotatable about a fifth axis A5, and is driven to rotate by a fifth axis drive motor M5. The fifth axis A5 is provided in a direction inclined with respect to the fourth axis A4. On the bend list 16, the swivel list 17 has the sixth axis A6.
It is rotatably supported around and is driven to rotate by a sixth shaft drive motor M6 (not shown). 6th axis A6 is the 5th axis
It is provided in a direction inclined with respect to A5. The floating cylinder device 20 is mounted on the swivel list 17. Each of the axis drive motors M1 to M6 is a pulse motor, and each of them has pulse encoders E1 to E6 for detecting the position. The motors M1 to M6 and the pulse encoders E1 to E6 are connected to and controlled by the robot controller 30.

FIG. 3 is a sectional view showing the floating cylinder device 20. The floating cylinder device 20 has an air cylinder structure. A piston 22 is fitted into a cylinder body 21 fixed on the swivel list 17 of the robot 10, and is urged by compressed air in a direction to retract the piston rod 23. A continuity sensor 24 is provided in the cylinder so as to be able to contact the piston 22. Continuity sensor 24 is a piston
Also serves as a stopper at the stroke end of 22, and the piston
The electrical contact is detected by the contact of 22 and the stroke end of the floating cylinder device 20 is detected.

A tool head 26 is attached to the piston rod 23 via a bracket 25. The tool head 26 includes a tool 27 made of a rotary grindstone. A distance sensor 28 is provided in the cylinder body 21, and the stroke amount of the floating cylinder device 20 is detected by detecting the distance to the tool head 26 by light.

In the free state, the floating cylinder device 20 is at the stroke end position where the piston 22 is pressed against the conduction sensor 24 by the urging force of compressed air. Tool (rotary whetstone)
When 27 is pressed against the base material 50 as a workpiece, the piston 22 and the piston rod 23 move against the biasing force of the compressed air. That is, the pressing force with which the tool 27 presses the base material 50 as the workpiece is determined by the urging force of the compressed air.

FIG. 4 is a block diagram showing the robot controller 30. The robot controller 30 includes a CPU 31 (central processing unit 3
1), memory 32, CRT console 33 with integrated display and keyboard, operating box 34 which is a portable operation panel, and robot controller 35 consisting of servo drive units D1 to D6 for each axis, and programmable controller (PC) 36, tool drive unit 37, auxiliary control section 39 consisting of NG discrimination circuit 38.

The robot control unit 35 is a part that mainly controls the movement trajectory of the robot, and in the CPU 31, the teaching points taught by the JOG operation from the CRT console 33 and the operating box 34 are stored in the memory 32, and the information is stored in the information. based on calculated interpolation points by performing an interpolation operation or the like stored in the memory 32, the target position theta ₁ in each axis servo drive unit D1~D6 calculates a target position of each axis J1~J6 from the interpolation point, theta ₂ ... Outputs θ ₆ . The servo drive units D1 to D6 for each axis each have a CPU for servo control, and each axis drive motor to detect the position signals from the pulse encoders E1 to E6 and realize the commanded target positions θ _{1 to} θ _6. Controls M1 to M6.

The auxiliary controller 39 is a programmable controller (PC)
Auxiliary control such as control of the tool drive unit 37 by the 36 is performed, and data is exchanged with the robot control CPU 31. That is, the NG discriminating circuit 38 discriminates whether or not the stroke amount of the floating cylinder device 20 is within a predetermined threshold value of, for example, 1 mm ± 0.1 mm according to the output from the distance sensor 28, and discriminates between + NG, OK, and −NG. Output a signal. PC
At 36, an NG section storage area is secured in the internal memory, and + NG, OK, and -NG discrimination signals are stored for each section divided between the interpolation points. The section in which the robot 10 is currently traveling is notified to the PC 36 by a processing section determination signal from the CPU 31. After the traveling ends, the CPU 31 reads the above-mentioned determination signal stored in the internal memory of the PC 36, and performs processing such as correction of the motion locus.

In addition, the signal from the continuity sensor 24 is sent to the CPU3 via the PC36.
Passed to 1.

In this embodiment, the NG discrimination means 1 is realized by the NG discrimination circuit 38, and the teaching point storage means 2 and the NG section storage means 4 are realized by the processing of the CPU 31 of the robot control unit 35 and the memory 32. Also, the traveling means 3, the correcting means 5, and the repeating means 6
Is realized by the processing in the CPU 31.

 The operation will be described based on the above configuration.

FIG. 5 is a plan view (a), a front view (b), and a cross-sectional view (c) showing a base material which is a workpiece. The base material 50 is a sheet metal member having a curved curved surface shape, and has a bead portion 51 left by brazing welding. This bead portion 51 is removed by a polishing operation with a tool (rotary grindstone) 27 so as not to cause distortion in the base material 50, and a smooth curved surface is obtained.

In order to teach the movement trajectory of the robot 10, a bead portion 51 is removed and a master base material 50 having an ideal profile is prepared. First, the processing surface 27A of the grindstone 27 is brought into contact with the tool (rotary grindstone) 27 without rotating the master base material 50, and the contact position is detected as the master base material position. Contact detection is performed by the continuity sensor 24. The measurement points 52 and 53 for contact detection are appropriately selected from the base material shape. Then, the detected master base material position is stored as a teaching point.

Next, arithmetic processing is performed to shift each teaching point by 1 mm in the direction in which the floating cylinder device 20 is pushed. This is because the measurement of the master base material shape is detected at the contact position of the tool 27, but since a constant pressing force is applied to the tool during the polishing work, the floating cylinder device 20 accurately measures 1 mm.
This is because the target motion locus is determined so that the vehicle runs while being pushed in only.

Next, based on the shifted teaching points, the teaching points are interpolated to obtain interpolation points, and the robot 10 is actually run to measure the degree of contact of the tool 27 with the master base material 50. This is because the robot 27 is run by bringing the tool 27 into contact with the master base material 50 without rotating, and the NG is generated for each section divided at each interpolation point.
This is performed by storing whether or not the NG signal from the determination circuit 38 is output. Then, even if only one NG signal is output, the interpolation point is corrected to make the stroke amount of the floating cylinder device 20 appropriate, and the robot 10 is run again to hit the tool with the master base material 50. Measure the condition. By repeating traveling and correction of interpolation points many times, each interpolation point is corrected so that the stroke amount of the floating cylinder device 20 falls within the threshold value of 1 mm ± 0.1 mm in all traveling sections.

In this way, each teaching point that gives the target motion locus,
The continuous motion locus itself is automatically taught as a locus along the master base material 50, not as merely sampled points.

6 and 7 are flowcharts showing the processing in the CPU that realizes the above control concept.

When the teaching point measurement process is started (step 100), first, the base material 50 is positioned so that it can approach the measurement points 52 and 53, and the posture is determined (step 101). Then, the approach to the base material 50 is started, and the contact of the tool 27 with the base material 50 is awaited (steps 102 and 103). The contact with the base material 50 is detected when the electrical continuity of the continuity sensor 24 is cut off. As soon as the contact of the tool 27 with the base material 50 is detected, the robot 10 is stopped (step 104), and the contact point position is stored by storing the coordinates θ ₁ , θ ₂ ... θ ₆ of each joint at that time. (Step 105). Perform the above process at each measurement point 5
By repeating the processing at 2,53 (step 106), the teaching point is stored as data including a large number of contact point positions.

When the contact detection of all measurement points is completed, step 10
Proceeding to step 7, correction is made to shift the teaching point consisting of the numerous contact point positions in the direction in which the floating cylinder device 20 is pushed in by 1 mm. This is the end of the teaching point measurement process.

Next, the trajectory correction process shown in FIG. 7 is started. When the processing is started (step 200), in step 201, interpolation calculation is performed between the measured teaching points, the interpolation points are obtained and stored in the memory 32, and the robot 10 travels according to the locus connecting the interpolation points. Done. At this time, the tool 27 is not rotated.

During this traveling operation, the CPU 31 outputs to the PC 36 one after another machining section discrimination signals for informing which section is currently traveling.
The PC 36 stores the + NG, OK, and -NG signals from the NG discrimination circuit 38 in the internal memory one after another according to the machining section discrimination signal.

When one cycle of traveling operation consisting of a series of traveling operations is completed, the CPU 31 reads the internal memory of the PC 36 at step 202 and checks whether or not there is a section in which the + NG signal or the -NG signal is stored. If there is at least one section in which the NG signal is stored, proceed from step 203 to step 204
The interpolation point in the section where the signal is stored is corrected by a predetermined minute amount according to whether it is the + NG signal or the -NG signal. And step 20
Return to 1 and repeat the running operation from the beginning.

Then, if only the OK signal is present in all the sections, the process proceeds from step 203 to step 205 to end the process.

As described above, in this embodiment, the tool 27 is directly connected to the base material 50.
The teaching point is detected by touching the workpiece, and the target motion locus is run based on the interpolation point calculated from the teaching point while the tool 27 is in contact with the base material 50, and the interpolation point of the defective point is corrected. To do. Therefore, the motion trajectory of the robot 10 can be automatically corrected and the base material 50 having a curvature can be corrected.
It was possible to set the motion locus of the robot 10 moving with the tool 27 always at a constant angle with an accuracy of ± 0.1 mm.

The application of the present invention is not limited to robots for polishing work. By applying this to a robot that uses a force sensor for deflashing, it is possible to automatically set a motion trajectory with a constant pressing force.

[Advantages of the Invention] The present invention has the above-mentioned configuration and is provided with a means for actually moving the robot to correct the teaching point. Therefore, the tool is appropriately contacted with a workpiece having a curved surface. There is an excellent effect that the motion locus of the robot can be automatically taught with high accuracy at a few teaching points. Further, since the tool (rotary grindstone) is brought into direct contact with the base material to detect the position of the base material and correct the target locus, the wear of the grindstone can be corrected at the same time.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a configuration diagram showing the configuration of the invention, FIG. 2 is a perspective view showing a robot, FIG. 3 is a sectional view showing a floating cylinder device, and FIG. 4 is robot control. FIG. 5 is a block diagram showing the apparatus, FIG. 5 is a diagram showing a base material, and FIGS. 6 and 7 are flowcharts showing actual processing. 10 …… Robot, 20 …… Floating cylinder device,
24 …… Continuity sensor, 26 …… Tool head, 27 …… Tool (rotating grindstone), 28 …… Distance sensor, 30 …… Robot control device, 31 …… CPU, 35 …… Robot control unit, 36 …… PC (Programmable controller), 38 ... NG discrimination circuit (NG discrimination means), 39 ... Auxiliary control unit, 50 ... Base material, 51 ... Bead portion, 52, 53 ... Measuring point.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiro Niwa 1-1-1, Asahi-cho, Kariya city, Aichi Prefecture Nobuo Fujimoto, Examiner, Toyota Koki Co., Ltd. (56) Reference JP-A-63-15306 (JP, A)

Claims (1)

(57) [Claims] 1. A floating cylinder device attached to the tip of a robot for holding a tool by urging the tool in a certain direction with a predetermined pressing force, a distance sensor for detecting a stroke amount of the floating cylinder device, and an output of the distance sensor. NG discriminating means for discriminating that the stroke amount deviates from the predetermined target value by a predetermined threshold value or more and outputting an NG signal, teaching point storing means for storing the robot's target motion locus as a teaching point, and between the teaching points. And a traveling means for causing the robot to travel on the target motion locus, and for each section divided by interpolation points obtained by interpolating between the teaching points whether or not the NG signal is generated during the traveling. NG section storing means for storing the NG signal, correction means for correcting the teaching point so as to move the interpolation point in the section where the NG signal is generated in the direction to make the stroke amount proper, The traveling means to the NG signal in the interval of Te is not generated, the NG section storage unit and the robot control apparatus characterized by comprising a repeating unit, a repeatedly executing said modifying means.