Mass measurement using the fixed-point of a spring-mass system with a dynamic vibration absorber and an inertial-mass vibrator

摘要

A mass-spring system with a dynamic vibration absorber has a fixed point in its frequency response curves. A method of measuring mass using this property was proposed. It has an advantage that mass is estimated independently of the damping in the absorber. The developed system was characterized by using a phase-looked loop to achieve the tuning condition. However, because the actuator producing the harmonic force was mounted on the base, the reaction force was transmitted to the surrounding structure. It may cause a severe vibration of the surrounding structure. Therefore, it is necessary to prevent transmission of force to the surrounding structure in measuring. In this paper, a new type of mass measurement system is proposed which uses an inertial-mass vibrator to reduce the transmitted vibration. The tuning conditions are derived for both systems with a damped absorber and with an undamped absorber. The principles of measurement are described based on a mathematical model. An experimental apparatus is designed and fabricated. The efficacy of the measurement system with an inertial mass-type vibrator is studied both analytically and experimentally.