Efficient representation of reflecting structures for a sonar navigation model

Abstract

A physically-based simulation model for a sonar navigation system is described, in which the reflecting elements consist of walls, corners and edges arranged in a floor plan. When the transducer is operating in the pulse/echo mode, each element that falls in the transducer field-of-view contributes to the reflected signal through its impulse response. The floor plan is represented as a two-dimensional grid of visibels, that indicate which elements are visible from a particular location. A visibel is represented by a word in computer memory, each bit of which is assigned to a particular element (corner, wall or edge) in the floor plan. The advantage of this conceptually simple approach is that it allows the transducer to move through the floor plan efficiently. This efficiency results because the visibel values are set prior to signal generation, thus allowing a variety of transducer types or transducer locations to be examined quickly. Examples of simulated sonar maps using the time-of-flight ranging system are shown for two floor plans, one simple and the second more complicated. The simulations are verified by comparing them with actual sonar maps obtained with the Polaroid sensor.