LoadCarrier¶
Introduction¶
The LoadCarrier module allows the detection of load carriers, which is usually the first step when objects or grasp points inside a bin should be found. The models of the load carriers to be detected have to be defined in the LoadCarrierDB module.
The LoadCarrier module is an optional on-board module of the rc_visard and is licensed with any of the modules ItemPick and BoxPick or SilhouetteMatch. Otherwise it requires a separate LoadCarrier license to be purchased.
Detection of load carriers¶
The load carrier detection algorithm detects load carriers that match a specific load carrier model, which must be defined in the LoadCarrierDB module. The load carrier model is referenced by its ID, which is passed to the load carrier detection. The detection of a load carrier is based on the detection of its rectangular rim. For this, it uses lines detected in the left camera image and the depth values of the load carrier rim. Thus, the rim should form a contrast to the background and the disparity image must be dense on the rim.
If multiple load carriers of the specified load carrier ID are visible in the scene, all of them will be detected and returned by the load carrier detection.
By default, when assume_gravity_aligned is true and gravity
measurements are available, the algorithm searches for load carriers whose rim planes
are perpendicular to the measured gravity vector. To detect tilted load carriers,
assume_gravity_aligned must be set to false or the load carrier’s approximate
orientation must be specified as pose and the pose_type should be set to
ORIENTATION_PRIOR.
Load carriers can be detected at a distance of up to 3 meters from the camera.
When a 3D region of interest (see RoiDB) is used to limit the volume in which load carriers should be detected, only the load carriers’ rims must be fully included in the region of interest.
The detection algorithm returns the poses of the load carriers’ origins (see Load carrier definition) in the desired pose frame.
The detection functionality also determines if the detected load carriers are overfilled,
which means, that objects protrude from the plane defined by the load carrier’s outer part of the rim.
Fig. 25 Load carrier models and reference frames
Detection of filling level¶
The LoadCarrier module offers the detect_filling_level
service to compute the filling level of all detected load carriers.
The load carriers are subdivided into a configurable number of cells in a 2D grid. The maximum number of cells is 10x10. For each cell, the following values are reported:
level_in_percent: minimum, maximum and mean cell filling level in percent from the load carrier floor. These values can be larger than 100% if the cell is overfilled.level_free_in_meters: minimum, maximum and mean cell free level in meters from the load carrier rim. These values can be negative if the cell is overfilled.cell_size: dimensions of the 2D cell in meters.cell_position: position of the cell center in meters (either incameraorexternalframe, see Hand-eye calibration). The z-coordinate is on the level of the load carrier rim.coverage: represents the proportion of valid pixels in this cell. It varies between 0 and 1 with steps of 0.1. A low coverage indicates that the cell contains several missing data (i.e. only a few points were actually measured in this cell).
These values are also calculated for the whole load carrier itself. If no cell subdivision is specified, only the overall filling level is computed.
Fig. 26 Visualizations of the load carrier filling level: overall filling level without grid (left), 4x3 grid (center), 8x8 grid (right). The load carrier content is shown in a green gradient from white (on the load carrier floor) to dark green. The overfilled regions are visualized in red. Numbers indicate cell IDs.
Interaction with other modules¶
Internally, the LoadCarrier module depends on, and interacts with other on-board modules as listed below.
Note
All changes and configuration updates to these modules will affect the performance of the LoadCarrier module.
Stereo camera and Stereo matching¶
The LoadCarrier module makes internally use of the following data:
- Rectified images from the Camera module
(
rc_camera); - Disparity, error, and confidence images from the Stereo matching module
(
rc_stereomatching).
All processed images are guaranteed to be captured after the module trigger time.
IO and Projector Control¶
In case the rc_visard is used in conjunction with an external random dot
projector and the IO and Projector Control module (rc_iocontrol), it is recommended to connect
the projector to GPIO Out 1 and set the stereo-camera module’s
acquisition mode to SingleFrameOut1 (see Stereo matching
parameters, so that on each
image acquisition trigger an image with and without projector pattern is
acquired.
Alternatively, the output mode for the GPIO output in use should be set
to ExposureAlternateActive (see Description of run-time parameters).
In either case,
the Auto Exposure Mode exp_auto_mode should be set to AdaptiveOut1 to optimize the exposure
of both images (see Stereo camera parameters.
No additional changes are required to use the LoadCarrier module in combination with a random dot projector.
Hand-eye calibration¶
In case the camera has been calibrated to a robot, the loadcarrier module
can automatically provide poses in the robot coordinate frame.
For the loadcarrier nodes’ Services, the frame of the
output poses can be controlled with the pose_frame argument.
Two different pose_frame values can be chosen:
- Camera frame (
camera). All poses provided by the modules are 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). All poses provided by the modules are 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 the mounting is static, no further information is needed. If the sensor is robot-mounted, therobot_poseis required to transform poses to and from theexternalframe.
Note
If no hand-eye calibration is available, all pose_frame values should be set to camera.
All pose_frame values that are not camera or external are rejected.
Parameters¶
The LoadCarrier module is called rc_load_carrier
in the REST-API and is represented in the
Web GUI under
.
The user can explore and configure the LoadCarrier
module’s run-time parameters, e.g. for development and testing, using the
Web GUI or the REST-API interface.
Parameter overview¶
This module offers the following run-time parameters:
| Name | Type | Min | Max | Default | Description |
|---|---|---|---|---|---|
assume_gravity_aligned |
bool | false | true | true | When true, only gravity-aligned load carriers are detected, if gravity measurement is available. |
crop_distance |
float64 | 0.0 | 0.05 | 0.005 | Safety margin in meters by which the load carrier inner dimensions are reduced to define the region of interest for detection |
min_plausibility |
float64 | 0.0 | 0.99 | 0.8 | Indicates how much of the plane surrounding the load carrier rim must be free to count as valid detection |
model_tolerance |
float64 | 0.003 | 0.025 | 0.008 | Indicates how much the estimated load carrier dimensions are allowed to differ from the load carrier model dimensions in meters |
Description of run-time parameters¶
Each run-time parameter is represented by a row on the LoadCarrier Settings section
of the Web GUI’s LoadCarrier page under Modules.
The name in the Web GUI is given in brackets behind the parameter name and the parameters are
listed in the order they appear in the Web GUI. The parameters are prefixed with load_carrier_
when they are used outside the rc_load_carrier module from another detection module
using the REST-API interface.
assume_gravity_aligned (Assume Gravity Aligned)¶
If this parameter is set to true, then only load carriers without tilt will be detected. This can speed up the detection. If this parameter is set to false, tilted load carriers will also be detected.
This parameter is ignored for load carriers with an orientation prior.
model_tolerance (Model Tolerance)¶
indicates how much the estimated load carrier dimensions are allowed to differ from the load carrier model dimensions in meters.
Via the REST-API, this parameter can be set as follows.
PUT http://<host>/api/v2/pipelines/0/nodes/rc_load_carrier/parameters?model_tolerance=<value>PUT http://<host>/api/v1/nodes/rc_load_carrier/parameters?model_tolerance=<value>
crop_distance (Crop Distance)¶
sets the safety margin in meters by which the load carrier’s inner dimensions are reduced to define the region of interest for detection (ref. Fig. 57).
Via the REST-API, this parameter can be set as follows.
PUT http://<host>/api/v2/pipelines/0/nodes/rc_load_carrier/parameters?crop_distance=<value>PUT http://<host>/api/v1/nodes/rc_load_carrier/parameters?crop_distance=<value>
min_plausibility (Minimum Plausibility):¶
The minimum plausibility defines how much of the plane around the load carrier rim must at least be free to count as valid detection. Increase the minimal plausibility to reject false positive detections and decrease the value in case a clearly visible load carrier cannot be detected.
Via the REST-API, this parameter can be set as follows.
PUT http://<host>/api/v2/pipelines/0/nodes/rc_load_carrier/parameters?min_plausibility=<value>PUT http://<host>/api/v1/nodes/rc_load_carrier/parameters?min_plausibility=<value>
Status values¶
The LoadCarrier module reports the following status values:
| Name | Description |
|---|---|
data_acquisition_time |
Time in seconds required to acquire image pair |
last_timestamp_processed |
The timestamp of the last processed image pair |
load_carrier_detection_time |
Processing time of the last detection in seconds |
Services¶
The user can explore and call the LoadCarrier module’s services, e.g. for development and testing, using the REST-API interface or the rc_visard Web GUI on the LoadCarrier page under Modules.
The LoadCarrier module offers the following services.
detect_load_carriers¶
Triggers a load carrier detection as described in Detection of load carriers.
Details
This service can be called as follows.
PUT http://<host>/api/v2/pipelines/0/nodes/rc_load_carrier/services/detect_load_carriersPUT http://<host>/api/v1/nodes/rc_load_carrier/services/detect_load_carriersRequired arguments:
pose_frame: see Hand-eye calibration.
load_carrier_ids: IDs of the load carriers which should be detected. Currently only one ID can be specified.Potentially required arguments:
robot_pose: see Hand-eye calibration.Optional arguments:
region_of_interest_id: ID of the 3D region of interest where to search for the load carriers.
region_of_interest_2d_id: ID of the 2D region of interest where to search for the load carriers.Note
Only one type of region of interest can be set.
The definition for the request arguments with corresponding datatypes is:
{ "args": { "load_carrier_ids": [ "string" ], "pose_frame": "string", "region_of_interest_2d_id": "string", "region_of_interest_id": "string", "robot_pose": { "orientation": { "w": "float64", "x": "float64", "y": "float64", "z": "float64" }, "position": { "x": "float64", "y": "float64", "z": "float64" } } } }
load_carriers: list of detected load carriers.
timestamp: timestamp of the image set the detection ran on.
return_code: holds possible warnings or error codes and messages.The definition for the response with corresponding datatypes is:
{ "name": "detect_load_carriers", "response": { "load_carriers": [ { "height_open_side": "float64", "id": "string", "inner_dimensions": { "x": "float64", "y": "float64", "z": "float64" }, "outer_dimensions": { "x": "float64", "y": "float64", "z": "float64" }, "overfilled": "bool", "pose": { "orientation": { "w": "float64", "x": "float64", "y": "float64", "z": "float64" }, "position": { "x": "float64", "y": "float64", "z": "float64" } }, "pose_frame": "string", "rim_ledge": { "x": "float64", "y": "float64" }, "rim_step_height": "float64", "rim_thickness": { "x": "float64", "y": "float64" }, "type": "string" } ], "return_code": { "message": "string", "value": "int16" }, "timestamp": { "nsec": "int32", "sec": "int32" } } }
detect_filling_level¶
Triggers a load carrier filling level detection as described in Detection of filling level.
Details
This service can be called as follows.
PUT http://<host>/api/v2/pipelines/0/nodes/rc_load_carrier/services/detect_filling_levelPUT http://<host>/api/v1/nodes/rc_load_carrier/services/detect_filling_levelRequired arguments:
pose_frame: see Hand-eye calibration.
load_carrier_ids: IDs of the load carriers which should be detected. Currently only one ID can be specified.Potentially required arguments:
robot_pose: see Hand-eye calibration.Optional arguments:
filling_level_cell_count: Number of cells in the filling level grid.
region_of_interest_id: ID of the 3D region of interest where to search for the load carriers.
region_of_interest_2d_id: ID of the 2D region of interest where to search for the load carriers.Note
Only one type of region of interest can be set.
The definition for the request arguments with corresponding datatypes is:
{ "args": { "filling_level_cell_count": { "x": "uint32", "y": "uint32" }, "load_carrier_ids": [ "string" ], "pose_frame": "string", "region_of_interest_2d_id": "string", "region_of_interest_id": "string", "robot_pose": { "orientation": { "w": "float64", "x": "float64", "y": "float64", "z": "float64" }, "position": { "x": "float64", "y": "float64", "z": "float64" } } } }
load_carriers: list of detected load carriers and their filling levels.
timestamp: timestamp of the image set the detection ran on.
return_code: holds possible warnings or error codes and messages.The definition for the response with corresponding datatypes is:
{ "name": "detect_filling_level", "response": { "load_carriers": [ { "cells_filling_levels": [ { "cell_position": { "x": "float64", "y": "float64", "z": "float64" }, "cell_size": { "x": "float64", "y": "float64" }, "coverage": "float64", "level_free_in_meters": { "max": "float64", "mean": "float64", "min": "float64" }, "level_in_percent": { "max": "float64", "mean": "float64", "min": "float64" } } ], "filling_level_cell_count": { "x": "uint32", "y": "uint32" }, "height_open_side": "float64", "id": "string", "inner_dimensions": { "x": "float64", "y": "float64", "z": "float64" }, "outer_dimensions": { "x": "float64", "y": "float64", "z": "float64" }, "overall_filling_level": { "cell_position": { "x": "float64", "y": "float64", "z": "float64" }, "cell_size": { "x": "float64", "y": "float64" }, "coverage": "float64", "level_free_in_meters": { "max": "float64", "mean": "float64", "min": "float64" }, "level_in_percent": { "max": "float64", "mean": "float64", "min": "float64" } }, "overfilled": "bool", "pose": { "orientation": { "w": "float64", "x": "float64", "y": "float64", "z": "float64" }, "position": { "x": "float64", "y": "float64", "z": "float64" } }, "pose_frame": "string", "rim_ledge": { "x": "float64", "y": "float64" }, "rim_step_height": "float64", "rim_thickness": { "x": "float64", "y": "float64" }, "type": "string" } ], "return_code": { "message": "string", "value": "int16" }, "timestamp": { "nsec": "int32", "sec": "int32" } } }
reset_defaults¶
Restores and applies the default values for this module’s parameters (“factory reset”).
Details
This service can be called as follows.
PUT http://<host>/api/v2/pipelines/0/nodes/rc_load_carrier/services/reset_defaultsPUT http://<host>/api/v1/nodes/rc_load_carrier/services/reset_defaultsThis service has no arguments.The definition for the response with corresponding datatypes is:
{ "name": "reset_defaults", "response": { "return_code": { "message": "string", "value": "int16" } } }
set_load_carrier (deprecated)¶
Persistently stores a load carrier on the rc_visard.
This service is not available in API version 2. Use set_load_carrier inrc_load_carrier_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/set_load_carrierThe definitions of the request and response are the same as described in set_load_carrier in
rc_load_carrier_db.
get_load_carriers (deprecated)¶
Returns the configured load carriers with the requested
load_carrier_ids.This service is not available in API version 2. Use get_load_carriers inrc_load_carrier_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/get_load_carriersThe definitions of the request and response are the same as described in get_load_carriers in
rc_load_carrier_db.
delete_load_carriers (deprecated)¶
Deletes the configured load carriers with the requested
load_carrier_ids.This service is not available in API version 2. Use delete_load_carriers inrc_load_carrier_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/delete_load_carriersThe definitions of the request and response are the same as described in delete_load_carriers in
rc_load_carrier_db.
set_region_of_interest (deprecated)¶
Persistently stores a 3D region of interest on the rc_visard.
This service is not available in API version 2. Use set_region_of_interest inrc_roi_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/set_region_of_interestThe definitions of the request and response are the same as described in set_region_of_interest in
rc_roi_db.
get_regions_of_interest (deprecated)¶
Returns the configured 3D regions of interest with the requested
region_of_interest_ids.This service is not available in API version 2. Use get_regions_of_interest inrc_roi_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/get_regions_of_interestThe definitions of the request and response are the same as described in get_regions_of_interest in
rc_roi_db.
delete_regions_of_interest (deprecated)¶
Deletes the configured 3D regions of interest with the requested
region_of_interest_ids.This service is not available in API version 2. Use delete_regions_of_interest inrc_roi_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/delete_regions_of_interestThe definitions of the request and response are the same as described in delete_regions_of_interest in
rc_roi_db.
set_region_of_interest_2d (deprecated)¶
Persistently stores a 2D region of interest on the rc_visard.
This service is not available in API version 2. Use set_region_of_interest_2d inrc_roi_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/set_region_of_interest_2dThe definitions of the request and response are the same as described in set_region_of_interest_2d in
rc_roi_db.
get_regions_of_interest_2d (deprecated)¶
Returns the configured 2D regions of interest with the requested
region_of_interest_2d_ids.This service is not available in API version 2. Use get_regions_of_interest_2d inrc_roi_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/get_region_of_interest_2dThe definitions of the request and response are the same as described in get_regions_of_interest_2d in
rc_roi_db.
delete_regions_of_interest_2d (deprecated)¶
Deletes the configured 2D regions of interest with the requested
region_of_interest_2d_ids.This service is not available in API version 2. Use delete_regions_of_interest_2d inrc_roi_dbinstead.This service can be called as follows.
PUT http://<host>/api/v1/nodes/rc_load_carrier/services/delete_regions_of_interest_2dThe definitions of the request and response are the same as described in delete_regions_of_interest_2d in
rc_roi_db.
Return codes¶
Each service response contains a return_code,
which consists of a value plus an optional message.
A successful service returns with a return_code value of 0.
Negative return_code values indicate that the service failed.
Positive return_code values indicate that the service succeeded with additional information.
The smaller value is selected in case a service has multiple return_code values,
but all messages are appended in the return_code message.
The following table contains a list of common codes:
| Code | Description |
|---|---|
| 0 | Success |
| -1 | An invalid argument was provided |
| -4 | Data acquisition took longer than allowed |
| -10 | New element could not be added as the maximum storage capacity of load carriers has been exceeded |
| -11 | Sensor not connected, not supported or not ready |
| -302 | More than one load carrier provided to the detect_load_carriers or detect_filling_level services, but only one is supported |
| 3 | The detection timeout during load carrier detection has been reached. Consider reducing the model tolerance. |
| 10 | The maximum storage capacity of load carriers has been reached |
| 11 | An existent persistent model was overwritten by the call to set_load_carrier |
| 100 | The requested load carriers were not detected in the scene |
| 102 | The detected load carrier has no points inside |
| 300 | A valid robot_pose was provided as argument but it is not required |