JP2889622B2 - Polishing robot controller - Google Patents

Description

The present invention relates to an industrial robot, and more particularly, to a robot control device suitable for performing a polishing operation.

2. Description of the Related Art In the case where a butt portion of an automobile frame is arc-welded, it is necessary to perform a polishing operation with a rotary grindstone in order to remove a swelling caused by a weld metal and smooth the surface.

Generally, when a robot performs a polishing operation by moving a predetermined trajectory, for example, as shown in Japanese Patent Application Laid-Open No. 60-20858, a sensor for detecting a pressing amount of a grindstone at a tip is provided, and the created teaching is performed. The grinding wheel is moved based on the data, the pressing amount of the grinding wheel is detected, and if it exceeds a predetermined threshold, the teaching data is corrected and calculated so that the pressing amount of the grinding wheel is always constant, and the movement locus of the grinding wheel is changed. While polishing work was done.

`` Problems to be solved by the invention '' However, when the robot performs a process of correcting the teaching data so that the pressing amount of the grindstone is always constant during the polishing work and changing the movement locus of the grindstone as described above, Since the correction calculation process takes a long time, the operation of the robot is slow, and there is a problem that it is inefficient to polish a large number of workpieces having the same shape.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a polishing robot control device having a short cycle time without lowering the accuracy of polishing work.

"Means for Solving the Problems" In order to achieve the above object, according to the present invention, as shown in FIG. 1, a tool 27 attached to the tip of the robot 10 is movably held, and the tool 27 is A floating cylinder device 20 for urging the processing location with a predetermined pressing force,
A distance sensor 28 for detecting the stroke amount of the floating cylinder device 20; a target trajectory storage means 1 for storing a target operation trajectory taught by the reference workpiece beforehand; A base material position storage means 2 for contacting the periphery of the processed part, which is not the same, and storing each contact position as a base material position; a target trajectory correction means 3 for correcting the target trajectory from data of the base material position; The robot 10 is operated in accordance with the corrected target
The processing execution means 4 for performing the processing by urging the processing location with the predetermined pressing force, and the distance sensor 28 detects the stroke amount of the tool 27 which retracts according to the swelling state of the processing location during the processing. A repetition means 5 for repeating the machining execution means 4 until the stroke amount falls within a threshold value.
And a polishing robot control device characterized by comprising:

[Operation] In the polishing robot controller configured as described above,
The base material position based on the stroke amount of the floating cylinder device 20, that is, the base material position including the variation in the shape of the base material 50 in a state where the tool 27 is pressed against the base material 50 with a constant pressing force is stored. The target machining locus is corrected based on the base material position. Then, polishing is performed according to the corrected target processing locus. During this processing, the tool 27 pressed against the base material 50 with a predetermined pressing force by the floating cylinder device 20 is retracted by the swelling of the base material 50 due to the swelling state of the processing portion of the base material 50. This change in the stroke amount is detected by the distance sensor 28, and polishing is continued until the detected stroke amount converges within a predetermined threshold value.

"Example" An example 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 an articulated robot having six degrees of freedom, and performs a polishing operation using a rotary grindstone 27 attached to the tip of an arm. The workpiece is an automobile frame, which performs a polishing operation to smoothly finish a bead portion obtained by arc welding a joint between a pillar and a roof.

The structure of the robot will be described. A trapezoidal revolving base 12 is rotatably supported on a fixed base 11 about a vertical first axis A1 in a horizontal plane, and is revolved by a first axis driving motor M1. On the swivel base 12, the first arm 13
Is swingably supported about a horizontal second axis A2.
The swing drive is performed by the shaft drive motor M2. The first arm
A second arm 14 in the form of a cylinder has a horizontal third axis on 13.
It is swingably supported around A3, and is swingably driven by a third shaft drive motor M3 (not shown). At the distal end of the second arm 14, a twist list 15 has a fourth axis centered on the second arm 14.
It is rotatably supported around A4 and is turned by a fourth shaft drive motor M4. A bend wrist 16 is supported on the twist wrist 15 so as to be pivotable about a fifth axis A5, and is pivotally driven 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 is moved to the sixth axis A6.
, And is turned by a sixth-axis drive motor M6 (not shown). The sixth axis A6 is the fifth axis
It is provided in a direction inclined with respect to A5. On the swivel list 17, a floating cylinder device 20 is mounted. Each of the axis drive motors M1 to M6 is a pulse motor, and includes a pulse encoder E1 to E6 for detecting a 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 wrist 17 of the robot 10, and is urged by compressed air in a direction to retract the piston rod 23. A conduction sensor 24 is provided in the cylinder so as to be able to contact the piston 22. Continuity sensor 24 is a piston
The piston also serves as a stopper at the stroke end of 22
The contact of 22 detects electrical continuity and detects the stroke end of floating cylinder device 20.

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

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

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

The robot controller 35 is a part that mainly controls the motion trajectory of the robot, and the CPU 31 stores the teaching points taught by the JOG operation from the CRT console 33 and the operating box 34 in the memory 32 and stores the information in the information. The target positions of the axes J1 to J6 are calculated based on interpolation calculations based on the calculated positions, and the target positions θ ₁ , θ ₂ ... Θ ₆ are output to the axis servo drive units D1 to D6. Each servo drive unit D1~D6 of each axis includes a CPU for servo control, each axis drive motor so as to realize the target position theta ₁ through? ₆ commanded position signal is detected and the pulse encoder E1~E6 Controls M1 to M6.

The auxiliary control unit 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 determination circuit 38 determines 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 determines + 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 determination signals are stored for each section divided between the teaching points. In which section the robot 10 is currently traveling is notified to the PC 36 by a machining section discrimination signal from the CPU 31. After the end of traveling, the CPU 31 reads out the determination signal stored in the internal memory of the PC 36 and performs processing such as correction of an operation locus.

The signal from the conduction sensor 24 is also sent to the CPU 3 via the PC 36.
Conveyed to 1.

In the present embodiment, the target trajectory storage means 1 and the base material position storage means 2 store the processing of the CPU 31 of the robot controller 35 and the memory 32.
Is realized by: Further, the target trajectory correction means 3, the processing execution means 4, and the repetition means 5 are realized by 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 as a workpiece. The base material 50 is a sheet metal member having a curved surface shape, and has a bead portion 51 formed by brazing welding. The bead portion 51 is removed by a polishing operation using a tool (rotary grindstone) 27 so as not to cause distortion in the base material 50, thereby obtaining a smooth curved surface.

First, the processing surface 27A of the grindstone 27 is brought into contact with the base material 50 near the bead portion without rotating the tool (rotary grindstone) 27, and the contact position is detected as the base material position. The contact detection is performed by the conduction sensor 24. Measuring points 52, 5 for contact detection
3 is appropriately selected from the shape of the base material. Then, the target motion locus is corrected based on the detected base material position. By this correction, the wear of the grindstone of the tool 27 and the displacement of the base material 50 are corrected, and a target operation trajectory corresponding to the base material 50 to be processed is obtained. As the first target motion trajectory, data taught by the reference workpiece is set in the memory 32 in advance.

Next, polishing is performed according to the corrected target operation locus. The rising height and width of the bead portion 51 are not fixed, but are absorbed by the stroke of the floating cylinder device 20. The stroke amount is monitored every time one cycle of polishing processing for polishing the entire length of the bead portion 51 is completed. Probably, the stroke amount will not fall within the predetermined threshold value in one polishing process, but by returning to the original position and repeating the polishing process many times, the stroke amount over the entire region of the bead portion 51 is obtained. The amount will fall within a predetermined threshold. At this time, the pushing amount of the floating cylinder device 20 is substantially constant over the entire polishing processing region,
The bead portion 51 is removed and the surface of the base material 50 is polished to a smooth curved surface.

FIG. 6 is a flowchart showing the processing in the CPU for realizing the above-described control concept.

When the process is started (step 100), first, the base material 50
Is positioned at a position where it can approach the measurement points 52 and 53, and the posture is determined (step 101). Next, the approach to the base material 50 is started, and the contact of the tool 27 with the base material 50 is waited (steps 102 and 103). Contact with the base material 50
It is detected when the electrical continuity of 4 is cut off. Base material 50
As soon as the contact of the tool 27 with the robot is detected, the robot 10 is stopped (step 104), and the coordinates θ ₁ ,
The contact point position is stored by storing θ ₂ ... θ ₆ (step 105). By repeating the above processing at each of the measurement points 52 and 53 (step 106), the base material position as data including a large number of contact point positions is stored.

When the contact detection of all the measurement points 52 and 53 is completed, the process proceeds to step 107, where a process of correcting the target trajectory from the data of the base material position including the plurality of contact point positions is performed. This correction is performed by searching for a movement vector whose trajectory obtained by translating the target trajectory by a very small distance best matches the base material position. For simplicity, it is possible to simply correct the approach amount.

Next, in step 108 and subsequent steps, polishing is performed according to the corrected target locus. That is, step
At 108, a command is output to the PC 36 to start the rotation of the tool 27 to the tool drive unit 37, and at step 109, the robot 10 is caused to travel in accordance with the corrected target trajectory, and polishing is performed. During the polishing process, a weaving operation of moving the tool (rotary grindstone) 27 in a zigzag or spiral shape along the bead portion 51 is performed.

During this weaving operation, the CPU 31 successively outputs a machining section discrimination signal to inform the PC 36 which section is currently running. The PC 36 successively stores the + NG, OK, and -NG signals from the NG discrimination circuit 38 in the internal memory for each section according to the processing section discrimination signal.

When one cycle of polishing processing comprising a series of weaving operations is completed, in step 110, the CPU 31 reads the internal memory of the PC 36 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, step 111 is repeated from step 1
Return to 09, polishing operation from the beginning (weaving operation)
repeat.

Then, when only the OK signal is present in all the sections, the process proceeds from step 111 to step 112 and ends.

As described above, in the present embodiment, the rotating grindstone 27 is
Without stopping at the floating cylinder device 20
Since the bead portion 51 is removed by repeating the weaving operation many times with a predetermined pressing force, the bead portion 51 to be polished and removed does not burn, so that the base material 50 is not adversely affected.

[Effects of the Invention] The present invention uses the floating cylinder device having the above-described configuration to repeatedly process a processing location until the tool stroke amount falls within a threshold value, while the tool is retracted due to the bulging of the processing location. Therefore, without performing the correction control of the motion trajectory corresponding to the remaining amount of the machining location,
There is an excellent effect that the sizing process can be performed by simple control, the swelling of the processed portion can be uniformly removed to the position of the surface of the base material, and the polishing operation can be performed in a short time with high accuracy.

Further, since the tool is brought into direct contact with the base material to detect the position of the base material and correct the target trajectory, correction of tool wear and correction of the base material position can be performed simultaneously.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, FIG. 1 is a structural view showing the structure 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. FIG. 5 is a block diagram showing the apparatus, FIG. 5 is a diagram showing a base material as a workpiece, and FIG. 6 is a flowchart showing actual processing. 10… Robot, 20… Floating cylinder device,
24: Conductivity sensor, 26: Tool head, 27: Tool (rotary grindstone), 28: Distance sensor, 30: Robot controller, 31: CPU, 35: Robot controller, 36: PC (Programmable controller), 38 ... NG discriminating circuit, 39 ...
... Auxiliary control unit, 50 ... Base material, 51 ... Bead unit, 52,53 ...
... Measurement points.

Continuation of the front page (72) Inventor Hiroshi Niwa 1-1-1, Asahi-cho, Kariya-shi, Aichi Pref. 63-180458 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24B 27/00, 9/04

Claims (1)

(57) [Claims] 1. A polishing robot for performing a polishing process on a processed portion in order to smooth the surface of a processed portion raised from a base material, wherein a tool attached to a tip of the robot is movably held and said tool is mounted. , A distance sensor for detecting a stroke amount of the floating cylinder device, and a target trajectory storage means for storing a target operation trajectory previously taught by a reference workpiece. And a base material position storage means for bringing the tool into contact with the periphery of the processing location other than the processing location of the base material and storing each contact position as a base material position; and correcting the target trajectory from data of the base material position. A target trajectory correcting means for operating the robot in accordance with the corrected target trajectory, and pressing the tool onto the processing location by the predetermined pressing. A machining execution unit for performing machining by urging with force, and a stroke amount of a tool that retreats according to a swelling state of the machining location during the machining is detected by the distance sensor, and the stroke amount is within a threshold value. A polishing robot control device comprising: a repetition unit that repeats the processing execution unit until the processing execution unit is settled.