Users Manual

Suction Grasp
A grasp provided by the ItemPick and BoxPick components represents the recommended pose of the TCP (Tool
Center Point) of the suction gripper. The grasp orientation is a right-handed coordinate system and is defined such
that its z axis is normal to the surface pointing inside the object at the grasp position and its x axis is directed along
the maximum elongation of the surface.
The computed grasp pose is the center of the biggest ellipse that can be inscribed in each surface.
Fig. 7.4.3: Illustration of suction grasp with coordinate system and ellipse representing the maximum suction
surface.
Each grasp includes the dimensions of the maximum suction surface available, modelled as an ellipse of axes
max
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suction
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surface
_
length and max
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suction
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surface
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width. The user is enabled to filter grasps by
specifying the minimum suction surface required by the suction device in use.
In the BoxPick component, the grasp position corresponds to the center of the detected rectangle and the dimen-
sions of the maximum suction surface available matches the estimated rectangle dimensions. Detected rectangles
with missing data or occlusions by other objects for more than 15% of their surface do not get an associated grasp.
The grasp definition is complemented by a uuid (Universally Unique Identifier) and the timestamp of the oldest
image that was used to compute the grasp.
Item model
The ItemPick and BoxPick components allow to specify a model for the items to be picked. Each item model
includes minimum and maximum dimenstions of the expected items.
• The ItemPick component supports specifying the minimum and maximum sizes of unknown flexible and/or
deformable items.
• The BoxPick component supports specifying the minimum and maximum length and width of several rect-
angles.
7.4.3 Interaction with other components
Internally, the ItemPick and BoxPick components depend on, and interact with other on-board components as
listed below.
Note: All changes and configuration updates to these components will affect the performance of the ItemPick
and BoxPick components.
Stereo camera and Stereo matching
The ItemPick and BoxPick components make internally use of the following data:
• Rectified images from the Stereo camera component (rc
_
stereocamera, Section 6.1);
7.4. ItemPick and BoxPick 86