Design for navigation

The navigation and guidance of a mobile robot depend on inferences made from sensor measurements. Acoustic rangers offer the prospect of a simple means of determining range and direction but cannot in general be relied upon to measure the true range. To overcome this problem acoustic cats´ eyes (the acoustical analog of optical retroreflectors found on highways) were attached to the smooth vertical surfaces in the laboratory. A standard Polaroid sonar ranger was rotated through one complete circle while range measurements were taken at regular intervals. This experiment was repeated without these devices. The range readings were then superimposed onto an architect´s plan view of the area. The range scans taken with the acoustic cats´ eyes show a significantly higher degree of correspondence to the plan view than do the range scans taken without them. It is shown that by identifying step changes in the derivative (the curvature) with respect to direction a decision space is created from which the presence and location of corners, walls, and doorways can be inferred