4.2 Pick Point Positioning

Fig. 105 Pick Point Teaching - Pick Point Positioning

Enter the part height

The part height you must enter in this step is the height where the pick point is placed.

EYE+ corrects the parallax effect induced by the variation of the position of the parts on the Asycube surface by adding an offset to the X and Y coordinates according to its position on the platform. A part located on the edge of the platform will have a greater offset than a part located in the middle. To calculate these offsets, the system must identify the height of the part where you specified the pick point.

Fig. 106 Part height depending on the pick point position

Note

In the case of custom or structured production plates (with holes, grooves…), the part height entered must be adapted to not take into account the height of the part located inside the plate.

Fig. 107 Part height depending on the production plate used

Enter the production plate height

Similar to the part height, EYE+ also needs to account for the thickness of the production plate used with the current part in order to correct the parallax effect. For a standard Asyril plate, this is the distance between the bottom of the plate and its surface as described on Fig. 108 for a standard Asycube 240 plate.

Fig. 108 Height measurement for a standard Asycube 240 production plate

Per default, EYE+ will set this value to the height of the standard Asyril production plate for your Asycube type as defined in Table 22.

Table 22 Default production plate heights

Asycube	Height (mm)
50	6.0
80	6.0
240	13.0
380	12.5
540	12.5

If the current part requires a special plate, you will need to measure the height of this plate as described in Fig. 108 and enter the value in the production plate height field in EYE+.

Pick Point Positioning

Carefully place the target on the desired pick point position. This operation must be performed carefully because it determines the accuracy of the coordinates (X, Y) that will be sent to the robot. A set of shapes is at your disposal in the toolbox to help you align the pick point relative to any visible feature, or place it at a predefined distance from them.

Fig. 109 Pick point positioning

Note

Please note that the detected features are not necessarily the exact representation of the technical drawing of your part. They can differ due to factors such as lighting, reflections, perspective, poor focus, etc.

Note

The coordinates returned by the get_part command will be directly corrected with the offset of parallax if the camera configuration has been done properly.

Feature masking

Fig. 110 Feature masking for the positioning of the pick point in the middle of the circle at the maximum height of the part

The objective of the feature masking step is to define the reference features (residual features after masking) that will be used as a model to place the pick point.

Not all features are relevant to define the reference model.

• Features at the same height: Features that are not placed at the same level as the pick point must be masked out. We only want to detect as accurately as possible those features that are at the same height as the pick point. Adding features that are not at the same level may alter the accuracy of the positioning of the pick point due to parallax (these features on a different level will not always have the same relative position depending on the position of the part in the Asycube).

• Reproducible features: It is essential that the reference model reflects a general description of the candidates. Any features that are not reproducible from one candidate to another must be masked.

• Enough features: There must be enough features to ensure that there is only one possible pick point identified by the algorithm. For example, if you want to pick the part in the middle of the circle but you do not inform the system about the circle features, there will be two possible pick point positions.

  

  Fig. 111 Not enough features to position the pick points: 2 possibilities

Use the brush to mask undesired features.

Advanced options

The advanced options provide additional settings that can be adjusted in case the default settings do not give good enough results, for example when some important features are not detected.

Contrast

By default, EYE+ automatically determines a contrast value that is used to extract features. The contrast value of a pixel is the gray value difference from its neighbors. If the pixel contrast exceeds the value specified, the pixel is selected to determine the model features.

Tweaking the contrast parameter allows creating a model that has more features than the automatically-computed one. For certain applications, it can help to precisely set the pick point.

The contrast setting can be manually set by toggling “Set contrast manually” on, as shown below:

The effect of the contrast setting is shown below:

Fig. 112 Pick point model where contrast is automatically computed by EYE+

Fig. 113 Pick point model where contrast is manually set to a lower value (e.g. 19)

Tip

The more features detected the more time it takes to run the pick angle step, remove as many features as possible using the mask functionality.