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 obtained by rotating the compass' head to obtain the direction where the responses of the sensors along the horizontal and vertical directions are balanced. The following algorithmic improvements have been made to reduce the measurement 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 made to rotate continuously and three-dimensionally during the directional estimation to gather plenty of data over a short time period. As a result, the measurement time at a practical level (20 s) has been achieved. The experimental results demonstrate the effectiveness of the compass in practical environments where the wind blows three-dimensionally and/or where the odor distribution is modified by an obstacle.