12 - Wall-Following

Summary

Section 4.1 described the attraction of wall-following as an exploration strategy and gave examples of its use in a number of research projects. It was argued in Section 4.3 that wall-following should be the first strategy to be implemented and tested because it will give an indication of what can be achieved when ARNE acts only on the basis of immediatelyavailable information and does not use the map to guide its exploration. This chapter describes the way in which wall-following was implemented on ARNE and presents the results of some explorations using this strategy.

12.1 Implementation

Wall-following has been implemented in two stages. First, ARNE approaches the nearest object that it can detect and positions itself ready for wall-following proper to start. The bulk of the exploration is then a repetitive process of ‘scan,turn,move’ actions in which ARNE moves so as to maintain an ideal distance from the nearest detected object. The remainder of this section describes the implementation of these two stages.

The first stage is quite simple. ARNE performs a complete sensor scan and groups the raw returns into readings, as described in Section 6.3. ARNE then selects the smallest range reading and moves so as to be at a standard distance, IDEAL-WALL-CLEARANCE, from the object. If the minimum range is greater than IDEAL-WALL-CLEARANCE, this means turning in the direction of the minimum reading. Otherwise ARNE turns directly away from the shortest reading.