JPS5991308A - Method for detecting surface configuration - Google Patents

Abstract

PURPOSE:To obtain a compact and durable device, by projecting light beams sequentially on the surface of an object body by using three or more light sources, receiving the reflected light beams from the object body by a two dimensional light point detector, and detecting the three dimensional positions of the reflecting points based on the outputs. CONSTITUTION:A plurality of at least 3 or more point light source 21 such as highly directive infrared ray light emitting diodes are arranged on an imaginary single circumference with, e.g., an inverval being provided in the circumferential direction, in a sensor 3 of a robot, which is used in an arc welding and the like. Said light sources 21 are sequentially lighted one by one. The light beams 24 undergo scatterred reflection on the surface of a work 6. The images of the reflecing points 25 are formed on a light receiving surface of a light receiving element 20 by a lens 23. The currents from electrodes 52-55 of the element 20 are imparted to a processor 57, the required values are obtained, and the three dimensional positions of the reflecting points are obtained by a specified computation. Thus the constitution becomes compact, faults do not occur by mechanical shocks, and excellent durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to maintain a tool attached to the working end of a working machine such as a robot at a constant distance and attitude relative to a target object such as a workpiece, and to The present invention relates to a method for detecting the surface shape of a target object, which is necessary when moving the target object along a path.

For example, in the teaching work of industrial robots for arc welding, a method is currently generally used in which a worker operates a switch or the like on a control panel to guide the tip of a welding torch along a welding line. In such prior art, the target position of the torch must be set with high precision, which places a heavy burden on the operator and requires a long time for teaching.

As a way to simplify this teaching work and improve efficiency,
Conventionally, methods using optical sensors have been proposed.

This method irradiates the workpiece with slit light and images the surface with an industrial television camera to detect steps in the weld line.

The equipment for carrying out such a method is large in size.

In another conventional method using an optical sensor, a beam of light is scanned over a workpiece by the angular displacement of a reflecting mirror.
The reflected light from the workpiece is detected. In this method, since the reflecting mirror is mechanically driven, there is a problem in that it is easily damaged by impact force. In addition, all of the conventional methods using optical sensors have only the function of detecting flaws and weld lines, and therefore only assist a part of the work that the welding operator is supposed to do.

Another prior art technique for simplifying teaching operations and improving efficiency is a method of detecting weld lines by contacting a plurality of styli on a workpiece. This method has problems in that the stylus is in contact with the workpiece, resulting in poor durability and an increase in the size of the device.

An object of the present invention is to provide an improved surface shape detection method that can detect the three-dimensional shape of the surface of a target object, is compact, has improved durability, and is easy to maintain.

FIG. 1 is an overall system diagram of an embodiment of the present invention. The procedure for teaching an industrial robot for arc welding is performed as follows.

(1) The teaching sensor 3 according to the present invention is installed in the hand of the working machine l.

(2) Operate the switch on the operation panel 4 to control the control processing device 50
The teaching sensor 3 provided on the hand 2 is guided to the teaching starting point 5 by the operator.

(3) The teaching sensor 3 detects the distance to the workpiece 6, which is the target object, the posture, and the position and direction of the welding line 7, and the control device 8 included in the control processing device 50 controls the teaching sensor for the workpiece 6. The distance and posture of 3 are maintained in a predetermined constant state, and the welding line 1 is moved along the welding line 7.

(4) While moving along the welding line 7, the output signal of the teaching sensor 3 is sent from the line 10 to the sensor signal processing device J1 for information processing. The teaching information obtained from line 9 is once stored in buffer memory 12 at predetermined constant time intervals.

Next, the data is edited by the teaching data editing device 13 and stored in the teaching data storage memory 14.

(5) When the teaching sensor 3 reaches the teaching end point 15,
After inputting the teaching end conditions, the teaching work of following the welding line 7 is completed, and the robot's hand 2 is moved to a predetermined waiting location.

(6) Replace the teaching sensor 3 with a welding torch as a tool and perform the regeneration work based on the teaching data described above. Teaching is done in this way.

The principle according to the present invention for detecting the distance and attitude of the teaching sensor 3 to the workpiece 6 and the position and direction of the welding line 7 will be described. FIG. 2 is a simplified sectional view showing the configuration of the teaching sensor 3. FIG. The two-dimensional light spot position detector 51 is
The workpiece 6 is placed on the light-receiving surface of the detection element 20 and the detection element 20.
It includes a lens 23 that forms a surface image of the image, and an optical filter 22.

As shown in FIG. 3, the point light sources 21 such as highly directional infrared light emitting diodes include at least three or more point light sources 21, such as highly directional infrared light emitting diodes.
They are spaced apart on an imaginary single circumference at intervals in the circumferential direction. The light sources 21 are sequentially turned on one by one, and when one light source 21 is turned on, the remaining light sources are turned off. When one light source 21 is turned on, its light beam 24 is diffusely reflected on the surface of the workpiece 6, and a reflection point 25 is imaged by the lens 23 on the light receiving surface of the detection element 20.

FIG. 4 shows the configuration of the detection element 20. The detection element 20 has four electrodes 52 to 5 arranged on each side of an imaginary square.
5. These electrodes 52 to 55 are provided within a high resistance semiconductor that constitutes a photodiode. The current from these electrodes 52 to 55 depends on the position of the light spot imaged on the detection element 20. By detecting the currents from these electrodes 52 to 55, the two-dimensional coordinates of the centroid of a single light spot can be detected and obtained, and when two light spots are being imaged, their coordinates can be determined. It is possible to detect the two-dimensional coordinates of a point that internally divides a straight line connecting the centroid in inverse proportion to the amount of light between the two.

FIG. 5 is a diagram showing the principle of detecting the three-dimensional coordinates of the reflection point 25. The principal point of the lens 23 is the origin 0, the vertical direction perpendicular to the light receiving surface of the detection IOB Shiko 20 included in the two-dimensional light spot position detector 51 is the Y axis, and the X axis is orthogonal to each other in the horizontal direction. and take the z-axis. FIG. 5(a) is a diagram in which the irradiated light and reflected light from the light source 21 are projected onto the XY plane.

Regarding the irradiation light, the first equation holds true.

y=tanθx (-x+lx) -(1)
Here, θX is the angle that line segment PQ makes with the X axis, and ix is line segment OQ
is the length of

The coordinates of the imaging position of the light receiving surface of the detection element 20 are (h, v)
Assuming that the distance from the origin 0 to the light receiving surface is 7, the following relational expression holds between these values and the coordinate values of the reflection point P (x, y, z).

The third equation is established from the first equation and the second equation.

xp= (x-h+Az)tanθx
-(3) Find the value K from the third equation.

K(F-h*tan θx)=4x*taxX θx
-(4) Substituting the fifth equation into the second equation, x
,7. When z is determined, the equations 6 to 8 are obtained.

FIG. 5 (1)) shows the irradiation light and reflected light from the light source 21
- It is a figure projected on the y plane. The reflection point P (X, 7°2) is found as follows.

y=tanθz (z+zz) ・
(9) Here, O2 is the angle that line segment PR makes with the Z axis, t! z is the length of the line segment OR-.

Using equation (9) instead of equation (1), equation 10 ~
Equation 12 is obtained.

The larger the lengths lx and lz, the more the detection accuracy can be improved. Therefore, for the light sources 21 arranged in a circle, for which the relationship ljx≧lz holds, Equations 6 to 8 are used, and for those for which the relationship lX<lz holds, the 10th equation is used. Formulas to Formula 12 are used.

The principle for finding a plane including the three reflection points 25 and finding the distance between the teaching sensor 3 and the workpiece 6 and the relative posture between the teaching sensor 3 and the workpiece 6 will be explained. However, the distance will be expressed as the distance d from the origin 0 to the point where the y-axis intersects the plane, as shown in FIG. Also, the posture is shown in Figures 7(a) to 7(0).
), the angles of rotation around the X-axis, y-axis, and two axes are represented by α, β, and r. Of these, the rotation angle β corresponds to the rotation of the welding torch around the axis in the case of welding work, and therefore the rotation angle β is not necessary for calculation and is not used in this embodiment.

The plane equation is generally expressed by Equation 13.

ax+by+c z==dp −・・O3
Now, three points P 1 (xl, yl, zl), P 2 (x2
sy2ez2), P 3(x3.y3.z3), each coefficient @IL, b, Q, dl
) and the coordinates of the three points p1゜P2, P3 (xi, yi, zi
) (where 1=1 to 3) has the following relationship.

The relationships expressed by Equations 18 to 20 exist between the rotation angle a with respect to the distance d1x@ between this plane and the principal point 0 of the lens 23, the rotation angle γ with respect to the z-axis, and each coefficient.

Furthermore, the coordinates (xl, yl, = 1) (however, 1 = 1 to 3)
The coordinates (hi
, F, v) (where i=1 to 3) and 1 (where 1
=1 to 3), it becomes as shown in Equations 1 to 24.

p (1=- --((h'1v2-h2vi)+(h3vl-hlv
3)+(h2v3-h3v2)) -HFigure 8 is
FIG. 3 is a diagram showing the principle for detecting a weld line 7 for lap welding. 811(a) is a perspective view thereof, and FIG. 8(b) is a plan view thereof.

The upper workpiece 5m and the lower workpiece 6b are collectively referred to as reference mark 6.
It is expressed as The optical axis of the light source 21 is inclined with respect to the workpiece 6. Therefore, the beam light irradiated to the overlapping part, that is, the welding line 7, is transmitted to the workpiece 6a above the overlapping part.
The light is divided into the reflected light on the upper part and the reflected light on the lower workpiece 6b, and the two divided circles 30 and 31 become discontinuous.

Therefore, the divided circles 30 and 31 are imaged on the light receiving surface of the detection element 20 as shown in FIG. 8(b). If the y-axis is taken in the direction of the chord of the two divided circles 30 and 31, and the relationship between the divided position and the output value of the y-axis component of the detection element 20 is determined, it is as shown in Equation 25.

Here, Al and A2 are images Ll corresponding to the split circles 30 and 31,
The area of L2, Kol, KO2 is the brightness of 6 images Ll, 112, VGI, V
C) 2 is the X coordinate of the image Ll, L2 (7) centroid, and ■ is the output value of the y-axis component of the detection element 20.

Equation 26 is obtained from Equation 25.

K1・AI V=, (VGI−VC2)+
VG2 = K (VGI - VC2) + VG2 - GlK
2@A2 for l·A1+ Since KOI and KO2 are inversely proportional to the square of the distance from the light source 21, Equation 27 holds true.

Here, R1 and R2 are the radii of the images Lj and L2.

Therefore, K shown in Equation 26 is as shown in Equation 28.

Here, ωl and ω2 are the spread angles of the images LI and L2, and can be regarded as 1 ω1 + ω2 - π.That is, if the optical axis is set at the origin 0 of the X coordinate and the distance to the string is xG, then , ``The relationship between xG and V can be found from Equations 31 and 32.

FIG. 9 is a diagram for explaining the operation when the spotlight is moved in a direction perpendicular to the weld line 7, which is the overlapping groove. Work 6 as shown in Figure 9(C)
When the groove is shown, a spot light is imaged on the light receiving surface of the detection element 20 as shown in No. 91J(a). This causes the output of the detection element 20 to change to the 9th ffl
It changes as shown in (b). Here, ωl=-...) The position of the t edge is the weld line 7, which is the groove, and if the value of V at -R1<x<R2... (to) is found, then The X coordinate of a certain welding line 7 can be calculated. Therefore, a plurality of light sources 21
are arranged in a circular manner as described above, and if the spotlights on the workpiece 6 overlap as shown in FIG. It is understood that the position of the groove can be determined by the reflected light from the light source 21.

FIG. 11 is a diagram showing the moving direction of the teaching sensor 3 moved by the working machine 1, which is a robot. When welding overlapping grooves, the image formation state of the light receiving surface of the detection element 20 corresponds to the light source 21 individually, as shown by the black dots in FIG. 11, and the direction of movement of the teaching sensor 3 is ΔXV(Δ
XV, Δyv, Δzv).

The distance between the teaching sensor 3 and the workpiece 6, the posture, and the welding line 7 determined by the detection principle according to the present invention.
Using the position and direction of , the teaching sensor 3 follows the welding line 7 at a predetermined distance and attitude relative to the workpiece 6 according to the hand 2 of the working machine using the control device shown in FIG. I can do it. The output from the detection element 20 is given to the processing device 57 (see FIG. 4), and the values ΔX, Δy, Δ2 . Δα, Δβ, ΔXV,
Δyv.

Δ27 is obtained. These values are calculated in coefficient circuit 58. In this coefficient circuit 58, Kl,
2. 3. α and γ are circuits with gains representing position and orientation, and KVI and KV2°k■3 are circuits with gains of velocity. Gain Kl, 2.
A signal from a circuit with 3 and gains KVI, K
V2. The outputs from the circuit having KV3 are added in addition circuits 59, 60, 61, and coordinate conversion circuit 4.
given to 0. The coordinate conversion circuit 40 calculates positional deviations Δxa, Δya, Δ in the absolute coordinate system of the working machine 1.
za and posture deviations Δaa and Δγa are calculated.

The angles θ1 to θ5 between the five axes of the work machine 1 are calculated by the coordinate conversion circuit 41, and the current position and orientation of the teaching sensor 3 in the absolute coordinate system are calculated by the coordinate conversion circuit 41.
, α, and γ are calculated. The outputs from the coordinate conversion circuits 40 and 41 are added in addition circuits 62 to 66 to obtain a position and orientation command value xr in the absolute coordinate system.

yr, zr, αr, and γr are determined and provided to the coordinate conversion circuit 42. The coordinate conversion circuit 42 obtains command values θlr, θ2r, θ3r, θ4r, and θ5r for the angles of the respective spaces. These command values θ1r to θ5r are given to the control devices 43 to 47 for each section. The control device 43 has a control element Hc for proportional, integral, arithmetic, etc., a drive means having a transfer function Ga, and an arithmetic element E, and the remaining control devices 44 to 47 also have a similar configuration.

In the above embodiment, a configuration using a large number of light sources is explained.
If p≦, the same function may be provided by a combination of one light source and a mechanism for scanning the light.

Further, although the light source is arranged in a circular shape, it may be arranged in a triangular or quadrangular shape depending on the object and purpose.

The above explanation has been made using the teaching of arc welding work as an example, but it can also be applied to teaching of sealing work where filler is applied to gaps, etc. Furthermore, it can also be applied to teaching work such as sealing work where filler is applied to gaps, etc. Furthermore, it can be applied to correction of the position and posture of tools during playback, and other uses. Needless to say, it can also be applied to

These embodiments described above have the following advantages.

(1) The time required for teaching can be shortened.

(2) High reliability because information necessary for teaching can be detected without contact.

(3) Since the sensor 3 is small and lightweight, it does not become an obstacle during work.

(4) The detection time is shorter than that of other chemical sensors, and the working machine 1 can be operated at high speed.

As described above, according to the present invention, the structure is miniaturized, the device does not break down even under mechanical impact force, has excellent durability, and three-dimensional detection can be performed over a relatively wide range.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of an embodiment of the present invention, FIG. 2 is a sectional view showing a simplified configuration of the teaching sensor 3, and FIG. 3 is a lower part of FIG. 2 showing the arrangement of the light source 21. FIG. 4 is a circuit diagram showing the detection element 20 and the processing circuit 57, FIG. 5 is a diagram showing the principle of detecting the three-dimensional coordinates of the reflection point, and FIG. 7 is a diagram for explaining how to represent distance, FIG. 7 is a diagram for explaining how to represent attitude angles α, β, and γ, and FIG. 8 is a diagram for explaining the principle of detecting weld line 7.
FIG. 9 is a diagram showing the relationship between the optical axis of the spot light and the output of the two-dimensional light spot detector 51, FIG. 10 is a diagram showing the spot light on the workpiece 6, and FIG. FIG. 12, which is a diagram for explaining the movement direction, is a block diagram showing a control system related to the working machine 1. l... Working machine, 3... Teaching sensor, 6... Workpiece 17... Welding connection, 20... Detection element, 21...
・Light source, 51...2 Ash source, light spot position detector Patent attorney Kei Nishi Part 1 Figure 2/ Figure 3 - Figure 4 (a) ■ Figure 5 (b) Figure 6 Figure 7 (a) (b) (c) Figure 8

Claims (1)

[Claims] The light from three or more point light sources is sequentially irradiated onto the surface of the target object, and the reflected light from the light sources is received by a two-dimensional light spot position detector, and based on the output of this two-dimensional light spot position detector. A method for detecting a surface shape, characterized in that the three-dimensional position of a reflection point is detected using a three-dimensional position of a reflection point, and the surface shape of a target object is thereby detected.