An experimental comparison of hierarchical and subsumption software architectures for control of an autonomous underwater vehicle

Abstract

A three-level hybrid architecture is used to model both a hierarchical and a subsumption controller for an autonomous underwater vehicle (AUV). The hierarchical model uses a backward chaining language (PROLOG) while the subsumption model uses a forward chaining language (CLIPS). The details of the backward chaining hierarchical implementation of the strategic level of mission control are first presented. This is followed by a similar description of the functionally equivalent subsumption controller. Experimental results and the advantages and disadvantages of each approach are discussed. CLIPS and PROLOG ran virtually even in terms of execution time. Also, the total run time of the experiment was dominated by the graphical simulator. A repeat of the experiment in which the controllers were decoupled from the simulator resulted in execution times between three and four seconds. This reinforces the view of PROLOG and CLIPS as viable language alternatives for the mission control of complex systems. However, PROLOG is the more concise of the two languages and is easier to read.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>