Architecture:Specification of BABEL Modules

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This page contains detailed information about a collection of modules and their role in the control architecture. The complete list of modules available for download is available here.

Layer 1: HAD Modules

All the interfaces are defined in the previous section.

Module (ICE) name Description Implemented Driver Interfaces
HAD_MobileBase_Pioneer Driver for the Pioneer3 DX/AT mobile bases, through a COM serial port and the ARIA library. DRV_WHEELS_MOBILE_BASE, DRV_IOBOARD, DRV_BATTERY_LEVEL
HAD_MobileBase_Simulator A simulated 2D mobile base. DRV_IOBOARD, DRV_WHEELS_MOBILE_BASE, DRV_2D_RANGE_SCANNER
HAD_Laser_Sick_USB Driver for the SICK laser range scanner via RS422-USB board. Hw version is JLBC/APR-05. DRV_2D_RANGE_SCANNER
HAD_Laser_Hokuyo Driver for the HOKUYO laser range scanner via a COM serial port. DRV_2D_RANGE_SCANNER
HAD_GPS Driver for COM-connected GPSs. DRV_GPS
HAD_GasSensors Driver for the custom-built e-Noses (Hardware Feb-2007). DRV_GAS_SENSOR
HAD_Generic_Camera Driver for any OpenCV/FFmpeg/Bumblebee camera (any camera supported by MRPT's CCameraSensor). DRV_CAMERA_SENSOR

Layer 2: Basic Sensory (BS) Modules

Recall that all these modules share a common IF as described in the previous section.


  • Description: This module collects data from odometry, and possibly from visual odometry, etc... to provide incremental estimations of the robot pose.
  • Interface: Sensory frames of objects CObservationOdometry.


  • Description: This module collects images from the available cameras and:
    • Provides the raw images, as CObservationImage or CObservationStereoImages objects.
    • Performs real-time feature tracking from stereo images (if available) and provides the tracked landmarks as an object of the class CObservationVisualLandmarks.


  • Description: This module collects data from laser range scanners, and ultrasonic sensors.

Layer 2: Basic Actuators (BA) Modules


  • Description: This module implements DRV_WHEELS_MOBILE_BASE and redirects all the calls to the actual underlying device, either a real robot or the simulator. This is the module to use when we want the mobile base to move or stop.

Layer 3: Sensory Detector (SD) Modules


  • Description: This module detects people around the robot using sensor data from range scanners, images, etc....
  • Interface: Create a new type of observation? and/or add some specific method to retrieve the detected data.


  • Description: This module maintains a 3D representation of close obstacles around the robot, by fusing data from sonars, laser scanners, and stereo vision.
  • Interface: TODO: Specific IF to retrieve:
    • A 2D obstacle point map.
    • A 2D occupancy grid.
    • A 3D point cloud.

Layer 3: Function Executors (FE) Modules

Recall that all these modules implement the Common Actions Interface.


Controls the reactive navigation capabilities of the robot in 2D. If a request is received while navigating, the previous one is automatically marked as cancelled.

  • Action: "navigate"
  • Action parameters (text lines within 'params' in the service executeAction(...) ):
    • "target_x = ...": The target location (in meters), X-coordinate in the current sub-map.
    • "target_y = ...": The target location (in meters), Y-coordinate in the current sub-map.
    • "relative = 0 | 1" (OPTIONAL, default=0): If set to "1", (x,y) coordinates are interpreted as relative to the current robot pose.
    • "max_dist = ...": (OPTIONAL) The distance (in meters) to the target location such as navigation can be considered successful.
    • "max_speed = ...": (OPTIONAL) If supplied, indicates the max. speed (m/s) of the robot. Angular max. speed is automatically derived. This can be used in situations known to be dangerous for the robot.


Asks a nearby human to open the door.

  • Action: "openDoor"
  • Action parameters (text lines within 'params' in the service executeAction(...) ):
    • None.

A practical example

An example of the low-level control architecture for a 2D robot with 2 laser scanners and a stereo camera:

Example control arch 1.png