Philipp Schillinger

What is FlexBE?

FlexBE is an open source behavior engine for ROS. It is based on SMACH and significantly extends the core concepts. Most notable is the extensive user interface, enabling features such as

Drag&drop behavior creation
Automated code generation
Monitored behavior execution
Adjustable level of autonomy
Runtime-modification of behaviors

Also, a core concept of FlexBE is reusability. States and behaviors are handled in a way to emphasize exchange and reuse between projects, while a lot of standard functionality is readily available in provided packages (see Github links). So make sure to check what is already there when starting to use FlexBE and consider sharing your own states and behaviors.

See the FlexBE website for more information.

Visual Impressions

This is an example how behaviors are defined and visualized in FlexBE. States correspond to actions which the robot is executing and transitions represent possible outcomes. The color of a transition refers to its required level of autonomy when executed in a shared autonomy setting. The above example shows a state machine to let the robot walk to a table in order to grasp an object there.

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Behavior Dashboard

The dashboard summarizes all meta information about a behavior. Default values for variables and userdata initialization are given there as well. By defining behavior functions, behavior-specific functionality can be used to parametrize generic states.

State Machine Editor

The visual editor is the core of the user interface and lets you easily define even complex hierarchical state machines without losing the overview. Numerous utility features such as autocompletion, documentation tooltips, and comments help you here.

Runtime Monitoring

Runtime montioring can be done in a dedicated view of the user interface in addition to having the active state highlighted in the editor. Providing more than just monitoring, transitions can be forced or blocked and the status of the onboard engine is visualized.

Dataflow & Consistency

To improve robustness of defined behaviors and help to easily spot problems, additional consistency checking is performed, e.g., to check if there exists any execution path resulting in undefined userdata keys. The illustration shows the dataflow of the above example.

Concurrent Execution

Sequential execution of states in a state machine-like fashion might not always be suitable. FlexBE provides multiple different containers, for example to allow concurrent execution or interrupting behavior routines.