Fundamental research for the tactile sensor to apply an endoscope

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When a tactile sensor gets brought in contact with silicone rubber, metals and plastics, their hardness or softness could be discriminated by judging from an increase in impedance change of a quartz-crystal tuning-fork tactile sensor at resonant vibration. From the contact examination of brass, stainless steel, copper, iron, aluminum, acrylic resin, and many kinds of silicone rubber, the impedance change becomes bigger as their hardness becomes harder, but smaller as their softness becomes bigger. It turns out that it is possible to discriminate their hardness by judging from an increase in impedance change of a quartz-crystal tuning-fork tactile sensor between before and after the contact examination. Furthermore, a model for a quartz-crystal tuning-fork tactile sensor in contact with an object is constructed. The base of a quartz crystal tuning fork undergoes flexural vibration. The reaction force, determined using Winkler's foundation, of an object in contact with the base is applied to the equation of motion of the base. The frequency of the tuning-fork tactile sensor is analyzed by considering the lateral clamping force of an acrylic resin case and Winkler's foundation of the object in contact. The frequency depends sensitively on the ratio Young's modulus/density. As for metals examination, the frequency is classified into two groups : one includes brass and copper, and the others include stainless steel, aluminum, and iron. As for silicone rubber examinations, the frequency also depends sensitively on the ratio Young's modulus/density. The frequency is classified into two groups. It is possible for the tactile sensor to discriminate viscoelasticity of a silicone rubber as a frequency change because silicone rubber is viscoelastic material.