Heat-Flow-Type Warmth Sensor with Sub-Second Response for Material Discrimination

This paper presents a heat-flow-type warmth sensor with sub-second response that discriminates materials for tactile sensing of robots. In previous study, the original sensor structure was proposed, and the material discrimination using a heat-flow peak in the heat-flow transitional phenomenon was demonstrated. In this study, to realize the material discrimination function as high response as human, the heat-flow-type warmth sensor with sub-second response was developed. Firstly, a thermal equivalent circuit of the sensor was proposed to simulate the transitional heat-flow characteristics. The simulation results showed that the response time of heat-flow peak is improved by reducing a heat capacity of the sensor and a thermal resistance of a surface material in the sensor. Secondly, miniaturized heat-flow-type warmth sensors downsized to 1/3.4 of previous one were fabricated according to the simulation results. The three miniaturized sensors were fabricated using three surface materials with different thermal resistances, and the experimental characteristics were compared to the simulation results. The tendencies of the experimental characteristics were agreement with those of the simulation results. Finally, the experimental results demonstrated the heat-flow-peak response times of 0.2 s with sufficient material discrimination function. Compared to the previous warmth sensor, the response time was improved 28 times.