Accurate natural frequency estimation method for myotonometer using a system identification method

Abstract

The purpose of this study is to propose a novel method to estimate natural frequency using a myotonometer with the aid of a system identification technique. A myotonometer is an instrument that measures muscle hardness based on an indentation method. The myotonometer applies a mechanical rectangular pulse to an object and records the acceleration of the indenter. This method showed the dependency of the natural frequency on the rectangular pulse width. Our proposed method extracted the acceleration that was not affected by the rectangular pulse. The extracted acceleration was regarded as an output of a system from the mechanical pulse to the acceleration. The system was identified, and then the natural frequency was calculated. We applied the method to edtimate the natural frequency of a gel-like object mimicking human soft tissue. The proposed method provided a smaller standard deviation of the natural frequency than the built-in program of the myotonometer.