Yamanaka Takao

The smell reproduction technique in addition to that for vision and hearing will be useful in the fields of virtual environments, games and e-commerce. In this study, citrus flavors were electronically recorded using. "odor recorder" composed of quartz crystal microbalance odor sensors. First, an artificial orange flavor composed of 14 constituents was successfully recorded with its approximated recipe of 3 odor components. The human sensory test revealed, that the reproduced odor was close to the target odor for the human olfaction. Next, we tried to record natural smells from citrus essential oils. The mixture smells of two essential oils were successfully recorded using the odor recorder.

The smell reproduction technique in addition to those for vision and hearing will be useful in the fields of virtual environments, games and e-commerce in fragrances and foods. We have developed an odor recorder to record odors using quartz crystal microbalance sensors and to reproduce them based on the recorded data. In this paper, the results of recording dynamical changes in odors in the atmosphere are described. The dynamical changes in the odors were successfully recorded in spite of the rapid change of the odor concentration over a few seconds due to the airflow turbulence. First, the change in a binary mixture of apple-flavor components was successfully recorded using the odor recorder based on a feedback control. Next, the changes in four fruit flavors, apple, mandarin, pineapple, and banana flavors, were successfully recorded using the odor recorder based on a pattern classification method.

The new method for the odor recorder, electronically recording the recipe of odors or scents made up of many components, was proposed. Although the apple flavors have been recorded with the mixture of five components using the odor recorder in previous work, the number of odor components should be increased to expand the applicable range of odors. Since the collinearity problem of the odor sensor array became apparent with the increase of the components, the new method based on the variable transformation using SVD (Singular Value Decomposition) was developed in this paper to extract the effective subspace of the sensor outputs for the recipe exploration. As a result, the sensor-array response pattern of the reproduced odor with the 8-component recipe almost agreed with that of the target apple flavor. Furthermore, the human sensory tests revealed that the smell of the approximated odor was identical to that of the target flavor.

A new type of olfactory display using solenoid valves controlled by delta-sigma modulation has been developed. It can be used to record and regenerate an odor with an arbitrary recipe in combination with an odor sensing system.

A new method to find a gas/odor source is proposed. A portable gas sensor array is fabricated by arranging 5x5 pulse drive semiconductor gas sensors, and is used for visualizing the flow of a target gas. The gas source can be located by tracking the measured flow direction. The redundant information from the sensor array makes the system more reliable compared with the case of a few sensors, especially under the environment with large wind turbulence and/or a quite slow wind field. The performance of the gas flow visualization has been tested in a wind tunnel, and the soundness of the basic idea is demonstrated.

The performance of the odor-source localization system has been improved. Since its working speed was limited to 1 cm/s by the slow response of its gas sensors, the response speed is raised by estimating the real rapid change of the odor concentration from the dull sensor response by applying Kalman filtering theory. Moreover, the calibration method to match the sensitivities of the plural gas sensors is refined considering their nonlinearity. As a result, the moving speed of the system has been improved to be 3 cm/s, and the time required to reach the odor source has been reduced to be one third of that in the previous paper.