CENTRING BODY AND METHOD FOR THE ALIGNMENT THEREOF

Abstract

A centring body is inserted into a reference opening of a component along the longitudinal axis of the centring body. The centring body includes an objective lens defining an optical axis which coincides with the longitudinal axis. A smart measure arrangement including the centring body and an industrial robot including such an arrangement are also disclosed as is a method for relatively aligning the centring body.

Claims

1. A centring body for insertion into a reference opening of a component along a longitudinal axis defined by said centring body, the centring body comprising an objective lens defining an optical axis coincident with said longitudinal axis.

2. The centring body of claim 1, further comprising an image sensor arranged downstream of said objective lens.

3. The centring body of claim 2, further comprising an exchangeable camera arrangement incorporating said objective lens and said image sensor.

4. The centring body of claim 3, wherein said exchangeable camera is provided with an alignment mark.

5. The centring body of claim 1, wherein said longitudinal axis is simultaneously an axis of symmetry of said centring body.

6. A smart measure arrangement comprising: a centring body for insertion into a reference opening of a component along a longitudinal axis defined by said centring body; said centring body including an objective lens defining an optical axis coincident with said longitudinal axis; a mini camera arranged within said centring body for capturing image data utilizing said objective lens; and, an evaluation unit configured to evaluate said image data, to determine an outer shape of the start of said reference opening of said component and to determine a current center point (M) of said reference opening and to determine the position of said center point (M) relative to said optical axis.

7. The smart measure arrangement of claim 6, wherein at least one second camera arrangement is provided.

8. The smart measure arrangement of claim 6, wherein said reference opening is a hole or recess.

9. An industrial robot comprising: a smart measure arrangement having a centring body for insertion into a reference opening of a component along a longitudinal axis defined by said centring body; said centring body including an objective lens defining an optical axis coincident with said longitudinal axis; said smart measure arrangement including a mini camera arranged within said centring body for capturing image data utilizing said objective lens; and, said smart measure arrangement further including an evaluation unit configured to evaluate said image data, to determine an outer shape of the start of said reference opening of said component and to determine a current center point (M) of said reference opening and to determine the position of said center point (M) relative to said optical axis.

10. The industrial robot of claim 9, wherein said reference opening is a hole or recess.

11. A method for aligning a centring body of a smart measuring arrangement and a reference opening of a component relative to each other, the smart measuring arrangement including: said centring body defining a longitudinal axis and having an objective lens mounted therein; said objective lens defining an optical axis coincident with said longitudinal axis; and, a camera arranged to coact with said objective lens, the method comprising the steps of: moving said centring body to a detection position from which image data of the component are captured by said camera with said objective lens; determining at least one current center (M) of said reference opening based on said image data by virtually matching an outer shape of the start of said reference opening to a circular shape and/or to a shape of an ellipse to arrive at a circle and/or ellipse; determining the center of said circle determined in this way or determining the center of an ellipse determined in this way; comparing each determined current center (M) of the reference opening to the position of said optical axis; generating and making ready control commands based on deviations of the position of said optical axis and of at least one current center (M); and, applying said control commands to cause a positioning device to bring the position of said optical axis and said current center (M) mutually closer when a pregiven tolerance threshold is exceeded so that said optical axis passes through said current center (M) or triggers a warning signal when a pregiven threshold value is exceeded.

12. The method of claim 11, further comprising the steps of: virtually adapting said outer shape of said reference opening to a circular shape and to the shape of an ellipse and determining respective current center points (M); forming a difference between the coordinates of the determined current center points (M); comparing the formed difference to a predetermined threshold and generating at least one control command for positionally adjusting said optical axis and said current center (M) when the threshold is maintained and a warning signal when the threshold is exceeded.

13. The method of claim 11, wherein the method steps are repeated to determine the current center (M), the different formation and the comparison of the difference with a predetermined threshold after completion of the positional adjustment of the optical axis and the current center (M).

14. The method of claim 11, wherein said reference opening is a hole or recess.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will now be described with reference to the drawings wherein:

[0033] FIG. 1 shows a longitudinal cross-sectional view of an embodiment of a centring body according to the disclosure;

[0034] FIG. 2 shows an exploded view of another embodiment of a centring body according to the disclosure;

[0035] FIG. 3 shows an embodiment of an arrangement according to the disclosure;

[0036] FIG. 4 shows a first example of the determination of a current center by adaptation of a circular shape;

[0037] FIG. 5 shows a first example of the determination of a current center by adaptation of the shape of an ellipse;

[0038] FIG. 6 shows a second example of the determination of a current center by adaptation of a circular shape; and,

[0039] FIG. 7 shows a second example of the determination of a current center by adaptation of the shape of an ellipse.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] An embodiment of a centring body 1 according to the disclosure is schematically shown in a longitudinal cross-sectional view in FIG. 1. The centring body 1 is rotationally symmetrical about its longitudinal axis 3 and tapered towards one end. The tip of the centring body 1 is open. On the inside, an objective lens 2 is provided the optical axis 3 of which coincides with the longitudinal axis 3. In addition, a camera 4 by means which image data can be captured using the objective lens 2 is disposed on the inside of the centring body 1. In the embodiment of FIG. 1, the centring body further includes a clamping device 10. In the example of FIG. 1, the clamping device 10 includes three outer jaws which are radially adjustable relative to the longitudinal axis and radially evenly distributed on the centring body. The centring body 1 can thus be inserted into a reference opening to gently pick up components such as, for example, workpieces or semi-finished parts in this defined pick-up position and deposit them again at a target position.

[0041] FIG. 2 shows another embodiment of the centring body 1 according to the disclosure. The centring body includes a miniaturised camera arrangement 4 (here also referred to as a mini camera) which includes an image sensor 4.2 and a camera objective. In the simplest case, the camera objective is formed by the objective lens 2. The mini camera 4 is pin-shaped and has an outer diameter of 3.2 mm. The mini camera 4 further includes an alignment mark 4.3. In the embodiment of FIG. 2, the alignment mark 4.3 is a notch formed in a circumferential collar 4.4 of the housing 4.1 of the mini camera 4. The position of the notch 4.3 on the collar 4.4 and the depth of the notch 4.3 depend on the calibration data of the mini camera 4 determined by a prior optical measurement of the mini camera 4.

[0042] The centring body 1 further includes a rotationally symmetrical head portion 1.1. The head portion 1.1 has a central bore 1.1.1 formed so as to match the outer housing diameter of the pin-shaped camera arrangement 4. The head portion 1.1 includes a projection 1.1.2 at its rear (proximal) end. The mini camera 4 is inserted into the bore 1.1.1 of the head portion and aligned so that the projection 1.1.2 of the head portion 1.1 engages with the notch 4.2 on the collar 4.3 of the camera housing 4.1. Aligned in this manner, the camera 4 is fixed to the head portion 1.1 by a ring nut. In an alternative embodiment (not shown in FIG. 2), the calibration data are stored in a database and can be read via a machine-readable code 4.2 attached to the camera housing 4.1 and transferred to the camera software which will then incorporate the calibration data and thus potential image errors of the camera arrangement 4 in image acquisition and/or image evaluation. In the embodiment of FIG. 2, the head portion 1.1 is followed by a fixing member 1.2 including a rapid receptacle for fastening the centring body to a robot arm, and an electrical connection for the transfer of camera image data.

[0043] An arrangement of a centring body 1 including an objective lens 2 and a camera 4 is schematically shown in FIG. 3. The camera 4 is disposed outside of the centring body 1 and obtains image data via a light-conducting fibre which is only illustrated in outlines. The optical axis 3 is directed to a component 5 provided with a reference opening 6 in the form of a RPS receiving hole. The camera 4 is connected to an evaluation unit 7 which is configured to obtain the coordinates of at least one current center M (see FIGS. 4 to 7) of the reference opening 6 based on the received image data and to compare the coordinates of the determined current centers M. A control unit 8 serves to generate control commands depending on the results of the evaluation unit 7. A positioning device 9 via which the positions of the optical axis 3 and of a current center M can be moved closer to each other is controlled by the control commands.

[0044] In FIG. 4, the determination of a current center M is shown by way of example. A circular shape is virtually adapted to the outer shape of the hole top of the reference opening 6 by approximating a circle to the bright-dark transition of the reference opening 6. The center of the circle obtained in this way is the current center M of the reference opening 6. In addition, a penetration point DP of the optical axis 3 (not shown) at which it would penetrate the reference opening 6 is virtually determined. The respective coordinates of the current center M and the penetration point DP are determined, for example as the X and Y coordinates of a Cartesian coordinate system. Based on the difference between the coordinates of the current center M and the penetration point DP, control commands can be generated, and the penetration point DP can be adjusted to the current center M or vice versa.

[0045] To adapt the outer shape of the hole top of the reference opening 6 to the shape of an ellipse (FIG. 5), the smallest diameter of the outer shape is identified as the small axis of an ellipse based on the image data. Based on the center of the small axis, a large axis of the ellipse orthogonal to it is determined. The current center M of the ellipse is determined and compared to the penetration point DP as described above.

[0046] It is also possible to compare the coordinates of the current centers M determined via the two approaches to each other. When the reference opening 6 has the desired shape and size the coordinates of the current centers M are very close to each other in case of round reference openings 6.

[0047] Such a situation is shown in the table below:

TABLE-US-00001 Offset to Center Algorithm X Y Diameter Circle (FIG. 4) 0.839 −0.029 20.009 Ellipse (FIG. 5) 0.840 −0.020 19.955 −0.001 −0.009 0.054

[0048] The coordinates only deviate slightly in the X or Y direction. Also, the deviation of the determined diameter is below a predetermined threshold and is deemed tolerable.

[0049] The situation illustrated in FIG. 6 (circle) and FIG. 7 (ellipse) is similar. However, the reference opening 6 is partly obstructed. In particular, the current center M determined via an adaptation to the shape of an ellipse is distinctly displaced upwards (FIG. 7). When comparing the coordinates of the current centers M determined via the two approaches significant deviations emerge which exceed a predetermined critical threshold (refer to the table below). In consequence of these deviations, a warning signal is set off.

TABLE-US-00002 Offset to Center Algorithm X Y Diameter Circle (FIG. 6) 0.859 −0.025 20.037 Ellipse (FIG. 7) 0.972 −2.955 12.730 −0.113 2.930 7.307

[0050] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

REFERENCE NUMERALS

[0051] 1 centring body

[0052] 1.1 head portion

[0053] 1.1.1 bore

[0054] 1.1.2 projection

[0055] 1.2 fixing member

[0056] 2 objective lens, camera objective

[0057] 3 optical axis, longitudinal axis

[0058] 4 camera arrangement, mini camera

[0059] 4.1 camera housing

[0060] 4.2 image sensor

[0061] 4.3 alignment mark, code, projection

[0062] 4.4 collar

[0063] 5 component

[0064] 6 reference opening

[0065] 7 evaluation unit

[0066] 8 control unit

[0067] 9 positioning device

[0068] DP penetration point

[0069] M current center