The LoadCarrierDB module (Load carrier database module) allows the global definition of load carriers, which can then be used in many detection modules. The specified load carriers are available for all modules supporting load carriers on the rc_visard.
The LoadCarrierDB module is a base module which is available on every rc_visard.
|Supported load carrier types||4-sided or 3-sided|
|Supported rim types||solid rim, stepped rim or ledged rim|
|Min. load carrier dimensions||0.1 m x 0.1 m x 0.05 m|
|Max. load carrier dimensions||2 m x 2 m x 2 m|
|Max. number of load carriers||50|
|Load carriers available in||ItemPick and BoxPick and SilhouetteMatch|
|Supported pose types||no pose, orientation prior, exact pose|
|Supported reference frames||camera, external|
Load carrier definition¶
A load carrier (bin) is a container with four walls, a floor and a rectangular rim, which can contain objects. It can be used to limit the volume in which to search for objects or grasp points.
A load carrier is defined by its
outer_dimensions are 2.0 meters in every dimension.
The origin of the load carrier reference frame is in the center of the load carrier’s outer box and its z axis is perpendicular to the load carrier’s floor pointing outwards (see Fig. 57).
Typically, outer and inner dimensions of a load carrier are available in the specifications of the load carrier manufacturer.
The inner volume of the load carrier is defined by its inner dimensions, but includes a region
of 10 cm height above the load carrier, so that also items protruding from the load carrier
are considered for detection or grasp computation. Furthermore, an additional
crop_distance is subtracted from the inner volume in every dimension, which acts as a safety margin and can
be configured as run-time parameter in the LoadCarrier module (see Parameters).
Fig. 58 visualizes the inner volume of a load carrier. Only
points which are inside this volume are considered for detections.
Since the load carrier detection
is based on the detection of the load carrier’s rim, the rim geometry must be specified if it
cannot be determined from the difference between outer and inner dimensions. A load carrier with a stepped rim can be defined by setting a
rim_thickness. The rim
thickness gives the thickness of the outer part of the rim in the x and y direction.
When a rim thickness is given, an optional
rim_step_height can also be
specified, which gives the height of the step between the outer and the inner part of the rim.
When the step height is given, it will also be considered during collision checking
(see CollisionCheck). Examples of load
carriers with stepped rims are shown in Fig. 59 A, B.
In addition to the
rim_ledge can be specified
for defining load carriers whose inner rim protrudes into the interior of the load carrier, such as pallet cages.
rim_ledge gives the thickness of the inner part of the rim in the x and y direction.
An example of a load carrier with a ledged rim is shown in Fig. 59 C.
The different rim types are applicable to both, standard 4-sided and 3-sided load carriers. For a
3-sided load carrier, the
type must be
THREE_SIDED. If the type is set to
left empty, a 4-sided load carrier is specified. A 3-sided load carrier has one side that is lower
than the other three sides. This
height_open_side is measured from the outer bottom of the load carrier. The open side is at the negative
y-axis of the load carrier’s coordinate system. Examples of the two load carrier types are given
in Fig. 60. The height of the lower side is only considered during
collision checking and not required for the detection of the load carrier.
A load carrier can be specified with a full 3D
pose consisting of a
orientation quaternion, given in a
pose_frame. Based on the given
this pose is either used as an orientation prior (
ORIENTATION_PRIOR or empty),
or as the exact pose of the load carrier (
In case the pose serves as orientation prior, the detected load carrier pose is guaranteed to have the minimum rotation with respect to the load carrier’s prior pose. This pose type is useful for detecting tilted load carriers and for resolving the orientation ambiguity in the x and y direction caused by the symmetry of the load carrier model.
In case the pose type is set to
EXACT_POSE, no load carrier detection will be performed on the scene data,
but the given pose will be used in exactly the same way as if the load carrier is detected at
that pose. This pose type is especially useful in cases where load carriers do not change their positions
and/or are hard to detect (e.g. because their rim is too thin or the material is too shiny).
The rc_visard can persistently store up to 50 different
load carrier models, each one identified by a different
The configuration of a load carrier model is normally performed offline,
during the set up the desired application.
This can be done via the REST-API interface or in the rc_visard Web GUI.
The configured load carrier models are persistent even over firmware updates and rollbacks.
Load carrier compartments¶
Some detection modules can make use of a
load_carrier_compartment to further limit the volume for the detection,
for example ItemPick’s compute_grasps service.
A load carrier compartment is a box whose
pose is defined as the transformation from the load carrier reference frame to the compartment
reference frame, which is located in the center of the compartment box (see Fig. 61).
The load carrier compartment is defined for each detection call separately and is not part of the load carrier definition in the
The compartment volume is intersected with the load carrier inner volume to compute the volume for the detection. If this intersection should also contain the 10 cm region above the load carrier, the height of the compartment box must be increased accordingly.
Interaction with other modules¶
Internally, the LoadCarrierDB module depends on, and interacts with other on-board modules as listed below.
In case the camera has been calibrated to a robot, the load carrier’s exact pose
or orientation prior can be provided in the robot coordinate frame by setting the corresponding
pose_frame argument to
pose_frame values can be chosen:
- Camera frame (
camera). The load carrier pose or orientation prior is provided in the camera frame, and no prior knowledge about the pose of the camera in the environment is required. This means that the configured load carriers move with the camera. It is the user’s responsibility to update the configured poses if the camera frame moves (e.g. with a robot-mounted camera).
- External frame (
external). The load carrier pose or orientation prior is provided in the external frame, configured by the user during the hand-eye calibration process. The module relies on the on-board Hand-eye calibration module to retrieve the sensor mounting (static or robot mounted) and the hand-eye transformation.
If no hand-eye calibration is available, all
pose_frame values should be set to
pose_frame values that are not
external are rejected.
The LoadCarrierDB module is called
rc_load_carrier_db in the REST-API and is represented in the
Web GUI under
The user can explore and call the LoadCarrierDB module’s services,
e.g. for development and testing, using the
REST-API interface or
the Web GUI.
The LoadCarrierDB module offers the following services.
Persistently stores a load carrier on the rc_visard. All configured load carriers are persistent over firmware updates and rollbacks.
This service can be called as follows.PUT http://<host>/api/v2/nodes/rc_load_carrier_db/services/set_load_carrier
Returns the configured load carriers with the requested
load_carrier_ids. If no
load_carrier_idsare provided, all configured load carriers are returned.
This service can be called as follows.PUT http://<host>/api/v2/nodes/rc_load_carrier_db/services/get_load_carriers
Deletes the configured load carriers with the requested
load_carrier_ids. All load carriers to be deleted must be explicitly stated in
This service can be called as follows.PUT http://<host>/api/v2/nodes/rc_load_carrier_db/services/delete_load_carriers
Each service response contains a
which consists of a
value plus an optional
A successful service returns with a
return_code value of
return_code values indicate that the service failed.
return_code values indicate that the service succeeded with additional information.
The smaller value is selected in case a service has multiple
but all messages are appended in the
The following table contains a list of common codes:
|-1||An invalid argument was provided|
|-10||New element could not be added as the maximum storage capacity of load carriers has been exceeded|
|10||The maximum storage capacity of load carriers has been reached|
|11||An existent persistent model was overwritten by the call to