Improving the Modularity of AUV Control Systems using Behaviour Trees

Abstract

In this paper, we show how behaviour trees (BTs) can be used to design modular, versatile, and robust control architectures for mission-critical systems. In particular, we show this in the context of autonomous underwater vehicles (AUVs). Robustness, in terms of system safety, is important since manual recovery of AUVs is often extremely difficult. Further more, versatility is important to be able to execute many different kinds of missions. Finally, modularity is needed to achieve a combination of robustness and versatility, as the complexity of a versatile systems needs to be encapsulated in modules, in order to create a simple overall structure enabling robustness analysis. The proposed design is illustrated using a typical AUV mission.

A Cyber-Physical System for Hydrobatic AUVs: System Integration and Field Demonstration

“…This makes FSMs hard to extend and maintain during the development phase of vehicles. As previously shown in [12], behavior trees avoid these complications and enable goal-based and deliberative mission-planning systems. Another advantage of using BTs comes from the fact that they are trees.…”

“…2) Mission execution: In order to execute the missions created in Neptus, a mission-critical behaviour tree (BT) is devel- Fig. 3: The SAM cyber-physical system architecture integrating a user interface, software, hardware, and simulation tools oped [12]. Although conventionally-used finite-state machines (FSM) can predictably respond to faults and mission progression triggers, they are inherently limited to the operator's expectations and inflexible to unexpected observations [13].…”

“…In addition to the usual safety and execution requirements, we also wanted to be able to use the exact same BT on a different vehicle, with minimal changes in implementation. In order to achieve this seamless transition, the BT design described in [12] was extended with a data-acquisition subtree. This part of the tree is responsible for reading in all relevant data from the sensors and other connected modules into the memory of the BT.…”

A Survey of Behavior Trees in Robotics and AI

“…The operation of Autonomous Underwater Vehicles (AUVs) also requires very reliable systems, not to avoid damage to bystanders, but rather to reduce the risk of loosing the vehicle itself. Thus, a BT approach for AUV mission management, including fault handling, was proposed in [156].…”

Analysis and Exploitation of Synchronized Parallel Executions in Behavior Trees

“…Applications span from manipulation [1], [2] to non-expert programming [3]- [5]. Other works include task planning [6], learning [7]- [9], and UAV systems [10], [11]. Using BTs, the designer creates robots behaviors by composing together actions and condition in a hierarchical fashion.…”