Three-dimensional odor compass

A three-dimensional (3-D) odor compass is proposed to develop a navigation tool used in searching for an odor source. The compass, which continuously points to the source, is equipped with four semiconductor gas sensors and a small fan to draw air to the sensors. The direction of the source is obtai ned by rotating the compass' head to obtain the direction where the respons es of the sensors along the horizontal and vertical directions are balanced . The following algorithmic improvements have been made to reduce the measu rement time after the previous report on the two-dimensional (2-D) compass. First, the transient sensor response model is introduced to compensate the response delay of the gas sensors. Secondly, the head of the compass is ma de to rotate continuously and three-dimensionally during the directional es timation to gather plenty of data over a short time period. As a result, th e measurement time at a practical level (20 s) has been achieved. The exper imental results demonstrate the effectiveness of the compass in practical e nvironments where the wind blows three-dimensionally and/or where the odor distribution is modified by an obstacle.