Autonomous Underwater Vehicle Control Coordination Using a Tri-Level Hybrid Software Architecture.

摘要

This paper proposes the use of Prolog as a rule based specification language for the coordination of multiple control functions as required to perform missions with autonomous underwater vehicles. We first define terms used in this type of control system and show that such systems fall into the class of 'Hybrid' controllers coupling discrete state/time independent and continuous state/continuous time elements. The design of these systems has received little attention, but, the software architecture to implement them is often composed of three levels for ease of segregation and development of functionality. An implementation of our controller on the NPS Phoenix vehicle uses PROLOG as a rule based language to specify and execute the phases of any mission. Embedded in the rule body are functions that interface with the vehicle to gather sensory data and generate signals as required to trigger transitions between control functions, and to initiate commands for the initiation of subsequent control functions. The importance of the use of PROLOG is that the same code is used for mission specification as is used for its execution thereby eliminating the question of correctness. Control of a mission segment using command generation to simultaneously drive the vehicle to a point on space and time (to coincidentally reach a given depth and heading) is described with experimental results. The development of transitioning signals can be problematic and is discussed alongside error recovery techniques using 'guaranteed phase completion'.