Three-dimensional gas-plume tracking using gas sensors and ultrasonic anemometer

A new sensing system for gas-source localization is proposed. Gas molecules released from their source are carried by airflow and form an aerial trail called a plume. The authors' group has been developing smart sensing systems and robots that can track gas flows and find their sources for, e.g., fire alarming and detection of flammable or hazardous gas leakage. The present report demonstrates the first sensing system that has accomplished sensitive detection and reliable tracking of gas plumes in real-life indoor environments. An ultrasonic anemometer is used to accurately measure the 3D vector of the airflow direction. Six tin-oxide semiconductor gas sensors are placed around the anemometer to estimate the 3D direction of the gas concentration gradient. The direction to follow is obtained by combining those two vectors. The experimental results show that the proposed system can track a gas plume formed in a field of airflow as low as 3 cm/s.