JPH0551438B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a movable table positioned along a long control axis X, and another control axis or This relates to an industrial robot that supports a controlled object positioned along a plurality of other control axes that can be positioned at least in a plane including the X-axis direction, and has position control means for these control axes, and has a particularly large inertial force. Even if the bottom stop position of the movable table where the movement table acts deviates from the command position, it does not adversely affect the positioning of the controlled object by the other control axis.

(Prior Art) For example, an industrial robot is known in which a controlled object is supported in a three-dimensionally positionable manner with respect to a movable table that is positioned along a long control axis X. In this case, since the entire weight of the three-dimensional positioning mechanism for the controlled object acts on the movable table, it is extremely difficult to accurately stop the movable table at the teaching position due to inertial force. In addition, when the controlled object grasps and transports a workpiece, the inertial force acting on the moving table is different when the workpiece is being held and when it is unloaded, which makes the accuracy of the stopping position even more difficult. cannot be expected.

Therefore, in order to deal with this problem, for example, the deviation of the stop position caused by the load acting on the moving platform is determined in advance, and the target value is corrected by this deviation, thereby allowing accurate positioning in the end. Something like this is being considered. However, if there are different types of workpieces and their weights differ, the deviation will change.

(Problems to be Solved) This invention has been made in view of the above-mentioned circumstances, and the inertia of the moving table is reduced by changing the load acting on the moving table and changing the acceleration time due to the length of the moving distance. Even if the deviation between the command position and the stop position changes due to the difference in The purpose of this is to enable positioning of the device at a predetermined position.

(Means for Solving the Problems) The present invention provides for a movable table positioned along a long control axis The industrial robot supports a controlled object positioned along a plurality of other control axes that can be positioned at least in a plane, and has position control means for the control axes, the position control means having the following means. This includes. That is, (a) means for calculating the difference ΔXi between the stop position information Xi during teaching for the control axis X in the i step and the actual stop position information Xinow.

(b) Means for adding ΔXi to teaching stop position information xi ₊₁ in the x direction of the other control axis in the same direction as the X in the (i+1) step.

(Function) Teaching position information of control axis X of i step
Find the difference △Xi between Xi and the actual stop position information Xinow. Next, in the (i ₊₁ ) step, the control axis
x direction in other control axes (same direction as X)
For the teaching position information xi ₊₁ , an x-direction converted value Δxi′ corresponding to the ΔXi is added. This added value is then output as a command value.

(Example) Reference numeral 1 denotes a straight horizontal guide, and a movable table 2 is supported on this guide 1, and its position in the X direction is forced by a hydraulic motor Mx.

3 is a horizontal first arm that is vertically supported on the movable table 2, and is forced to have a turning angle β ₁ by a hydraulic motor M ₁ .

A horizontal second arm 4 is vertically supported at the tip of the arm 3, and is forced to have a turning angle β ₂ by a hydraulic motor M ₂ .

Reference numeral 5 denotes a first rotating body vertically supported at the tip of the arm 4, and a rotating angle β ₃ is forced by a hydraulic motor M ₃ (not shown).

6 is a vertical arm supported on the rotating body 5, and its position in the Z direction is forced by a hydraulic motor _M4 .

Reference numeral 7 denotes a gripping means as a first end effector horizontally supported at the lower end of the arm 6, and the rotation angle β ₄ is forced by a hydraulic motor M ₅ . Further, the claws 7a of the gripping means 7 can be opened and closed by a hydraulic cylinder (not shown).

A second rotating body 8 is supported coaxially with the rotating body 5, and is forced to have a rotation angle α ₁ by an electric motor M ₁₁ (not shown).

Reference numeral 9 denotes a vertically rotating first arm that is horizontally supported on the rotating body 8, and is forced to have an elevation angle α ₂ by an electric motor M ₁₂ .

A vertically rotating second arm 10 is horizontally pivoted at the tip of the arm 9, and an elevation angle α ₃ is forced by an electric motor M ₁₃ .

A third arm 11 is horizontally supported at the tip of the arm 10, and an elevation angle α ₄ is forced by an electric motor M ₁₄ .

12 is a holder for the second end effector (welding torch) supported on the arm 11 and on a shaft perpendicular to the elevation axis of the arm 11, and is forced to rotate at a rotation angle α ₅ by an electric motor M ₁₅ . .

As described above, the robot R has the control axes X, β ₁ ,
A child robot (α-based robot) having 5 degrees of freedom α ₁ to α ₅ is supported in the middle of a parent robot (β-based robot) having 6 degrees of freedom β ₂ , β ₃ , β ₄ , and Z. It is something.

Each degree of freedom of this robot R is controlled by conventionally known means (for example, a microcomputer).
It is also assumed that the device is configured to be controlled by a known playback method.

CO is a control means (computer) for the β-based robot, and includes a CPU and memory. The bus line BU of the computer CO includes the teaching box TB, X-axis servo system, β _1- axis servo system, β ₂
An axis servo system, β _3- axis servo system, Z-axis servo system, β _4- axis servo system, and gripping means 7 are connected.

CO is a control means (computer) for α-based robots, and includes a CPU and memory. The bus line BU of the computer CO includes a teaching box TB, welding power source WS, α _1- axis servo system, α ₂
The axis servo system, α _3- axis servo system, α _4- axis servo system, and α _5- axis servo system are connected.

Note that both computers CO〓 and CO〓 are connected via a known interface.

Furthermore, the operation of this embodiment will be described.

It is assumed that the steel plate W ₁ is positioned horizontally in the movement area of the robot R by another device (not shown), and the robot R grips the channel material W ₂ with the grip means 7 and holds the channel material W ₂ in the second position. As shown in Figure 2, the parts to be welded are temporarily attached using a torch T while being pressed against the steel plate _W1 from above.

First, the operator teaches the robot R step by step the work to be done in the auto mode using known means.

i step of one user program (i:
1, 2, 3...), there is a command to control the movable table 2 to another position separated by a distance Xi' from the position indicated by the solid line in Fig. 3A, that is, to the position indicated by the two-dotted chain line 2' in Fig. 3A, and furthermore, In the next step, that is, the (i+1) step, the moving platform 2 remains stopped, and the arms 3,
A case in which there is a command to control the turning angle of No. 4 as shown by the two-dot chain line in FIG. 3 will be explained. Please refer to Figures 3 and 5.

(a) In advance, in processing S1, ΔXo is initially set to 0.

(b) In process S2, each axis position information (X _i , β _1i , β _2i , β _3i , Z _i , β _4i ) of the taught i step regarding the β-based robot is retrieved from the memory.
Import into CPU.

(c) In process S3, the position information of each axis is converted into rectangular coordinates as shown in FIG. 1B. In other words, change it like (X′i, xi, yi, zi, θi, i). Note that X′1=(k・Xi), and k is Xi
This is a constant for converting the pulse count value of to the distance in the X direction.

(d) And in process S4, xi=(xi+△X′i _-1 )
and correct the value of command position information xi. In addition, △
X'i _-1 is the difference △Xi -1 between the X-axis teaching stop position information Xi _-1 and the playback stop position information _{Xi -1} now at the (i _-1 ) step multiplied by a constant k. This is the distance in the X direction. That is, the command position information xi is corrected by the X-direction error ΔX'i _-1 determined in the step immediately before the i step to be reproduced. This point will become clearer in the discussion below.

(E) Then, in processing S5, (Xi, corrected
Based on the i-step information of xi, yi, zi, θi, i), a reproduction command is output to each servo system of the β-system robot, and the β-system robot is controlled in position.

(f) Then, in process S6, it is determined whether the position control of the β-based robot is completed.

It is assumed that when this position control is completed, the movable table 2 is located at the one-dot chain line 2'' in FIG. 3A, and is slightly deviated from the two-dot chain line 2' position in FIG.

(g) After the position control is completed, in process S7, the difference △Xi between the X-axis stop position information Xinow at the time of completion and the X-axis stop information Xi at the time of teaching is calculated as follows:
Calculate as ΔXi=(Xinow−Xi).

(H) Furthermore, in processing S8, the △Xi value is
Convert to directional distance. That is, △X′i=(k・△
Xi) is calculated.

Therefore, the position of the movable table 2 at the time of reproduction deviates from the position at the time of teaching by this distance ΔX′i.

(li) Next, in process S9, it is determined whether or not i is the final step number.

(N) In this case, it is not the final step, so the process
In S10, i is updated by 1, and the work contents after step S2 are repeated.

By the way, even if the turning angles of the arms 3 and 4 are controlled in accordance with the taught command position information in the next step when the moving table 2 ΔXi is at a deviated position, the position of the gripping means 7 will naturally be different from the target position. .

(ru) Therefore, after processing S2, the position information of step (i ₊₁ ) is taken into the CPU 〓 and then converted to the position in rectangular coordinates (Xi ₊₁ , xi ₊₁ , yi ₊₁ , zi _{+ 1} ,
Furthermore _, the command position information xi ₊ 1 is corrected to (Xi+1+△X'i), and then (Xi+1, corrected xi+1, yi+1, zi
+1, θi+1, i+1) based on the position information,
A regeneration command is output to each servo system of the β-system robot. Therefore, the position of the β-type robot is controlled as shown by the solid line in FIG. In other words, the tip position of the arm 4'' coincides with the tip position indicated by the dotted chain line 4' in FIG. 3 during teaching.

As described above, the difference _{△ Xi} between the stop position information Xi during teaching and the stop position information Xinow during playback with respect to _the By adding this to the stop position information xi ₊₁ during teaching, the position of the gripping means 7 is accurately controlled to the target position.

Therefore, if the β-type robot is accurately controlled to the target position, the α-type robot supported by it can naturally perform accurate tack welding.

The robot R mentioned above supports a control axis that can be positioned three-dimensionally on the control axis X, but for example, there is a robot R that supports a control axis that can position two-dimensionally only the β ₁ and β ₂ axes on the control axis X. , a control shaft that can be positioned two-dimensionally in the X direction and a direction perpendicular thereto may be supported. Furthermore, on the control axis
It may be possible to support one control shaft that can be positioned in the same direction as this.

Further, the control axis X may not be a straight line but may be a circle.

Replacement of other components with equivalents is also included within the technical scope of the present invention.

As described above, in this invention, even if the stop position Xinow at the time of reproduction with respect _to the control axis Since it is added to the stop position information xi ₊₁ during teaching in the x direction of other control axes other than the X axis,
When reproducing the (i ₊₁ ) step, the end effector is precisely controlled to the target position.

[Brief explanation of the drawing]

Each of the figures shows an embodiment of the present invention.
Figure A is an overall perspective view of the industrial robot, Figure 1B is the rectangular coordinates determined for the industrial robot, Figure 2 is an explanatory diagram showing the state of workpiece processing by the industrial robot, Figure 3A, 4 is a block diagram, and FIG. 5 is a flowchart. In the figure, R...Industrial robot, CO〓,
CO =...Control means, 1...Linear horizontal guide, 2...Moving table, 3...Horizontal first arm, 4...Horizontal second arm, 5...First rotating body, 6...Vertical arm ,7
. . . a first end effector (gripping means in the embodiment).

Claims (1)

[Claims] 1. With respect to the movable table positioned along the elongated control axis X, another control axis that can be positioned in the same direction as the long control axis while supporting a controlled object positioned along the
The industrial robot has position control means for these control axes, and the position control means includes stop position information Xi during teaching for the control axis X in the i step and stop position information for playback.
Means for calculating the difference △Xi from Xinow, and adding the difference △Xi to stop position information xi ₊₁ during teaching of the other control axis in the x direction (same direction as X) in the next step. The industrial robot comprising: means.