Abstract
This paper describes an online measurement method of time-varying viscoelasticity of subcutaneous tissues by external stimulation. Time-varying dynamic stiffness in subcutaneous tissues may be estimated by using the self-excited vibration generated by the positive feedback of velocity. Then we showed that viscoelastic coefficients in subcutaneous tissues, which didn't depend on measurement conditions, could be quantified with the estimated dynamic stiffness, based on the Hertz's formula and the correspondence principle between the theory of elasticity and viscoelasticity. In this report, we show that spring constant may be rapidly measured by the frequency estimation using Kalman filter as an adaptive filter, and that time-varying viscoelasticity on human body by muscular contraction can be measured by this technique.
