17.1 Motivation

The exploration strategies presented so far in Part III of this thesis have differed in the extent to which the map has been used to control the navigational choices. Wall-Following (Chapter 12) and Longest Lines (Chapter 16) were both totally reactive, not using the map at all. Supervised Wall-Following (Chapter 14) used the map to detect circumstances in which wall following was becoming ineffective. Chapter 15 showed the results that could be obtained when a human operator used the map to guide the exploration. This chapter will present an exploration strategy in which ARNE's decisions are driven primarily by the information present in the partially-formed map.

The implementation described in Section 17.2 builds on the ideas presented in Section 4.2; ARNE approaches the interesting regions of the environment. The central issue is, of course, the definition of ‘interesting’. The definition adopted here focuses on the edges of free space, the regions in which free cells are next to unknown cells.

Section 17.3 presents the results of experiments to evaluate this strategy and Section 17.4 summarises the results.

17.2 Implementation

The first step in this implementation was to identify the cells on the free-space map which were to be examined. The decision was made that ARNE should approach unknown regions but, to avoid collisions or panic stops, it should not actually enter unknown regions. The interesting cells are therefore those on the boundary between free and unknown space.