MBSnavigation: technical overview

MBSnavigation is made of a kernel in charge of generic navigation and modules to address various robot mechanics, tasks and environments.

The kernel is a multithreaded real-time process executing the following tasks:

• Motion estimation (including odometry),

• Local mapping, i.e. mapping of the immediate surroundings of the robot. This map is necessary for enhanced and robust sensor based navigation.

• Global mapping: this is the map of the whole area in which the robot navigates. MBSnaviagation can use an initial map or build the map autonomously (SLAM: Simultaneous Localization And Mapping). The map is automatically updated when the area is modified (new obstacles appear, old obstacles disappear).

• Obstacle avoidance: this task does reactive avoidance based on sensor data and predictive avoidance based on local map,

• Execution controller: in charge of mission execution, motion and action primitives start and stop in accordance with current robot state and map data.

• Supervision: user interface management and global system supervision.

There are four types of modules:

• Sensor management modules are in charge of sensor data acquisition and preprocessing. MBSnavigation contains modules for many sensor types: digital and analog inputs, inertial sensors, telemeters, cameras, etc. 

• User interface modules inform the user of the machine state and task progression; input modules manage user choices. Interfaces can be as simple as buttons and light indicators or advanced like LCDs and voice synthesizers.

• The mission planner is the tool that converts a generic mission definition at user level such as "mow my lawn" or "clean my office" into a sequence of actions. The kernel execution controller handles the execution of this sequence.

• Motion and action templates (or primitives) are closed loop controls that guarantee navigation robustness and safety. They are also sometimes called behaviours. The robot never executes open loop action. It is the fact that MBSnavigation is able to execute missions with a set of closed loop motion templates that makes it so efficient and safe. MBSnavigation contains many motion templates and is open to include new templates for specific actions.