A Multifunction Tactile and Proximity Sensing Method by Optical and Electrical Simultaneous Measurement

This paper presents a new single-unit tactile and proximity sensing method which simultaneously uses optical and electrical measurement. The proposed sensor consists of electrodes and a photodiode with a light-emitting diode. In the proposed method, the admittance between the electrodes and the photodiode is measured. The electrical properties of most objects vary with the distance between the sensor and the object, and in this sensor, they are measured from the admittance between the electrodes. Additionally, the optical properties of the sensor surface (indentation) are measured from the admittance of the photodiode. In the experiment, discrimination between six materials (acrylic, glass, aluminum, and sponges with three different hardness values) and detection of the indentation were demonstrated during contact, while the object proximity could also be detected. The proposed sensor may be useful as a tactile sensor in robots.