JPH059224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic processing device typified by a welding robot, and particularly to an automatic processing device that automatically traces a processing line using a sensor.

[Conventional technology]

Conventionally, this type of automatic processing equipment has been described in the literature “Visually Guided Arc-Welding Robot With
Self-Training Features” (TECNICAL
PAPER, 1983, Society of Manufacturing
Engineers). Figure 5a
1 is a block diagram showing a control device for a welding robot disclosed in the document, in which 1 is a robot, 2 is a control device for a welding robot;
is a torch holder attached to the arm of robot 1, 3 is a welding torch which is a processing tool, 4 is a wire,
Reference numeral 5 denotes a visual sensor (such as a CCD camera) of a welding line position detector, which is rotatably supported by the torch holder 2 and always precedes the welding torch 3.
In addition to the visual sensor 5, the welding line position detector has a sixth sensor.
As shown in FIG. Image the cutting line. FIG. 6b shows an image taken by the visual sensor 5. 6 is an image processing device that captures the video signal sent by the visual sensor 5 at a certain sampling period, processes the image, and calculates the point Ps (Xs, Ys) on the welding line WL on the imaging surface (two-dimensional). The bending point position in Fig. 6 b) is detected. Reference numeral 7 denotes a coordinate conversion device that converts position data Ps (Xs, Xs,
Ys) into position data P ^* s(Xs, Ys, Zs) on the robot coordinate system (three-dimensional). Reference numeral 8 denotes a first-in, first-out storage device (FIF0 device), which sequentially accumulates the detection point position data P ^* sent out by the coordinate conversion device 7 in each detection cycle, and stores the first stored detection point position data. The data are sequentially reproduced and sent to the Lohot control device 9. The robot control device 9 sequentially reads out the detection point position data P ^* from the FIFO device 8 in accordance with the stored control algorithm and calculates the next target point. 10 is a joint angle conversion device which converts the target point calculated by the robot control device 9 into a joint angle vector θ of the welding robot 1 and converts the joint angle command θ ₁ to
Send θ ₆ to welding pot 1. 11 is a model memory. The welding robot 1 is a six-axis robot, and the sixth axis is used to rotate the visual sensor 5 about the torch axis.

In this device, the visual sensor 5 traces the welding start point to the welding end point without welding at first, and the detected points in between are sequentially stored in the model memory 11, and the welding line WL is automatically taught. Let them do it (training mode). The position data stored in the model memory 11 is used to calculate the welding start point P ^* ₀ during welding, and also to determine the rotation angle ( 6th axis).

The visual sensor 5 moves ahead of the welding torch 3 while being controlled to capture the welding line WL within its field of view as described above, and the point on the welding line WL sent out by the visual sensor 5 is detected at a certain detection period. is detected as welding line position data P ^* on the robot coordinate system, and FIF0
The data are sequentially stored in the device 8. When one point on the welding line WL is detected as described above, the detection point position data stored first among the detection point position data P ^* _o stored in the FIFO device 8, for example, P ^* r
is read into the robot control device 9, the next target point is determined, and joint angle commands (θ ₁ to _{θ 6} ) are supplied to the welding robot 1.

[Problem that the invention seeks to solve]

In this way, in the conventional system described above, the first stored detection point position data is read every detection cycle of the detection line position data P ^* , the next target point is determined, and the joint angle command (θ ₁ to θ ₆ ) to the welding robot 1, so between adjacent detection points,
That is, when the welding torch 3 moves between P ^* _o-1 and P ^* _o , there is no guarantee that the locus of movement will be an optimal movement path, for example, a straight line or a curve. For this reason, when the welding speed becomes high as in the case of thin plate welding, the distance between detection points becomes large.
The deviation (error) between the actual welding line WL and the locus of movement of the welding torch 3 becomes large. Furthermore, the detection period is irregular because the processing speed of the image processing device changes depending on various conditions, such as the presence or absence of noise. Because the joint angles are dependent on the The problem was that it had to become expensive.

This invention was made in order to solve the above problem, and it is possible to improve the tracing accuracy of the processing tool compared to the conventional one without complicating it and without causing a significant increase in price. The object of the present invention is to obtain an automatic processing device with a sensor that can always control the path of the processing tool uniformly.

[Means for solving problems]

In order to achieve the above object, the present invention specifies the processing tool movement path between two adjacent detection points by calculation, sets a plurality of movement target points on the path, and sets a predetermined control period shorter than the detection period. The processing tool is positioned to be controlled at the movement target point.

[Effect]

In this invention, the processing tool moves along a specified movement path, and is controlled to move to a movement target point set on the movement path in a control period shorter than the detection period. By simply adding an algorithm, it is possible to significantly improve the tracing accuracy of processing tools compared to conventional methods.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

A case will be described in which the present invention is applied to the welding robot apparatus shown in FIG. 5a.

Figure 1a shows the welding line captured by the visual sensor 5.
Detection points P ₁ , P ₂ , P ₃ . . . P _{J .} (*) is omitted, P ₁ , P ₂ , P ₃ ……P _J ……
P _o ) and stored in the FIFO device 8 described in FIG. 5a as shown in FIG. 1b. When storing this, moving route interpolation information (specified during the above teaching), LNR (straight line) or
CIR (curve) is added. Assume that the welding torch 3 has just arrived at the detection point P ₁ , and this time is t ₁ and the moving speed of the welding torch 3 is v (mm/sec).
shall be. When the welding torch 3 arrives at the detection point _P1 , the robot control device 9 reads the position data _P2 of the next detection point from the FIFO device 8, and since the moving route interpolation information is LNR, the detection point _P1 -P The moving path _L12 of the welding torch 3 between _{the two} is specified as shown in FIG. 1c based on a predetermined linear interpolation formula.

When the movement route L ₁₂ is specified, the movement route L ₁₂ is changed to 1, 2, 3, . . . as shown in FIG. 1c.
N divided into N moving target points. Let the coordinates of each dividing point be P ₁ , P ₂ , P ₃ , ...P _N. The number of divisions N is determined by the robot position control cycle (T ₀ =constant), the moving speed v of the welding torch 3, and the distance of the moving path _L12 . Note that this control period T ₀ is a value smaller than the minimum value of the detection period, and for example, if this detection period is 200 ms, T ₀ is set to about 20 ms.

Movement target points P ₁ , P ₂ , P ₃ ,... on movement route L ₁₂
...After setting P _N (=P), one control cycle T ₀
The divided path (hereinafter referred to as movement vector) that the welding torch 3 should move next for each time −→Δl(Δx, Δy,
Δz) (=constant), that is, movement vector −→Δl=
Calculate p ₁・p ₁ , ₁・₂ , ₂・₃ ..., _N-1・_N.

When the calculation of the movement vector -→Δl is completed, the position vector obtained by adding the movement vector -→Δl to the current position P=P ₁ -→P ₂ =P→+−→Δl is the next movement target point and the joint angle is converted. The data is sent to the device 10. The joint angle conversion device 10 converts the position vector −→P ₂ into a joint angle vector θ→ using the joint angle conversion matrix M(−→P ₂ ).

In this way, the welding torch 3 reaches the detection point P ₂
When it arrives, the next weld line position data P ₃ is
Read from the FIFO device 8 and execute the above calculations. After this, this operation is repeated.

FIG. 2 shows the calculation algorithm for the linear interpolation. In the figure, the current position of the welding torch 3 is indicated by P, and the movement target point is indicated by Pi.

Next, the case of the above-mentioned linear interpolation will be specifically explained with reference to FIG. Assume now that the distance between P ₁ and _{P 2} is 10 m, the set speed of the welding torch 3 is 50 mm/sec, and the robot control period T ₀ is 20 msec.

The robot joint angles are controlled according to the joint angle vector θ→ in each control cycle. Since the set speed v is 50 mm/sec, the distance the robot should move in one control cycle is 1 mm. Now, since the distance between P ₁ and _{P 2} is 10 m, the number of controls (joint angle vector θ→
(N = 10)
becomes.

Once the number of divisions N is determined, the movement vector Δl to be moved in one control period is calculated based on the following formula.

−→Δl=−→/P ₂ −−→/P ₁ /N (1) Equation (1) is calculated only when starting from the detection point _P1 . Next, −→Pi=−→P ₁ +−→Δl ...(2) is calculated, −→Pi is converted to joint angle vector θ→ by joint angle matrix M, and θ→=M(− →Pi) ...(3) The welding robot position is controlled by this θ→. Thereafter, in every control cycle, P→=-→Pi, that is, until the welding torch 3 reaches the target position Pi from the current position P,
The following process is repeated.

−→Pi=P→+−→Δl, θ→=M(Pi) ...(4) In this example, the detection period is 200ms and the control period _T0 is 20msec, so the detection period is Compared to the conventional case where the control period is used, path control can be performed at ten times finer pitches, and the deviation between the moving path of the welding torch 3 and the welding line WL can be reduced accordingly.

Next, a case where curve interpolation is performed between detection points using a curve as shown in FIG. 3a, for example, an arcuate curve C, will be described. Figure 3b shows the FIFO device 8 in this case.
Fig. 4 shows the content of the calculation algorithm. When performing this curve interpolation, unlike the case of linear interpolation, the above-mentioned movement vector -→Δl is not constant but variable. When the welding torch 3 arrives at the detection point P ₁ , the number of position data that can specify the curve C, in this example, the position data P ₂
and P ₃ from the FIFO device 8, specify the curve C=P ₁ P ₂ P ₃ as the movement route, and convert the curve P ₁ P ₂ P ₃ to N
According _to the number of divisions, _the movement vector −→Δli (i=
1, 2, 3, ...). However, |−→Δl ₁ |
=|−→Δl ₂ |=……=|−→Δl _N |. From then on, the moving target point Pi is calculated as in the case of linear interpolation, and Pi
is defined by the joint angle matrix M as the joint angle vector θ→
The welding robot 1 is controlled by this θ→.

In the above embodiments, a welding robot device has been described, but the present invention can be applied to other automatic processing devices such as an automatic sealing device to obtain similar effects.

〔Effect of the invention〕

As explained above, this invention makes the control period smaller than the processing line detection period.
Since the path control of the processing tool can be performed at a fine pitch, the tracing accuracy of the processing tool can be improved compared to the conventional method, and the control period can be made independent of the detection period, so the above-mentioned Route control can always be performed uniformly, and there is no need to consider the control cycle when constructing the hardware and software of the detection section, so the device can be simplified and costs can be reduced. It has the advantage of being able to

[Brief explanation of drawings]

FIG. 1a is a diagram of the relationship between the welding torch, visual sensor, and detection points for explaining the operation of the embodiment of the present invention, and FIG. 1b is a diagram for explaining the contents of the FIFO device in the above embodiment. FIG. 1c is a diagram showing the interpolation straight line and moving target point in the above embodiment, FIG. 2 is a diagram showing the calculation algorithm in the above embodiment, and FIG. 3a is a diagram explaining the operation of another embodiment of the present invention. FIG. 3b is a diagram for explaining the contents of the FIFO device in the other embodiment, and FIG. 4 is a diagram showing the calculation algorithm in the other embodiment. Fifth
Figure a is a block diagram showing a conventional device, Figure 5 b is a diagram for explaining the operation of the above conventional example, and Figure 6 a.
6 is a diagram for explaining welding line position detection using the optical cutting line method, and FIG. 6b is a diagram showing an image of a visual sensor. 1... Welding robot, 3... Welding torch, 5...
...Visual sensor, 6... Image processing device, 7... Coordinate conversion device, 8... First-in, first-out storage device, 9...
...Robot control device, 10...Joint angle conversion device.

Claims (1)

[Claims] 1. A sensor that is located in a position preceding the processing tool and detects the processing line, a device that captures the output of the sensor at a certain period to create detection point position data, and accumulates the detection point position data from the device. In the automatic processing device with a sensor, the sensor-equipped automatic processing device includes a first-in-first-out storage device, and a control device that sequentially reads the detection point position data from the storage device and controls the processing tool to a target point given by the detection point position data. The control device specifies the processing tool movement path between the two adjacent detection points by calculation, sets a plurality of movement target points on the path, and moves the movement target points at a predetermined control cycle shorter than the above period. An automatic processing device with a sensor that controls the position of processing tools.