動吸振器を利用した無重力環境下での質量測定

抄録

A new type of mass-measurement system under weightless conditions is proposed which uses a dynamic vibration absorber as a measuring device. In this system, an object to be measured is fixed to a rotating table (rotor) at a distance from the rotational axis. Since it makes the rotor unbalanced, a centrifugal force whose amplitude is proportional to the mass is generated during rotation. It works as a harmonic excitation and forces a structure supporting the table to vibrate. However, a dynamic vibration absorber attached to the structure is tuned or controlled to reduce the vibration to zero. When the structure does not move at all, the absorber mass vibrates in such a way that the product of the mass and the displacement amplitude is equal to the amount of unbalance, that is, the product of the mass to be measured and its distance from the rotational axis. Therefore, the mass of the object is determined by measuring the displacement amplitude of the absorber mass. In this study, the principles and features of the proposed mass-measurement system are investigated. Experiments are carried out with a developed apparatus having an active dynamic vibration absorber. This apparatus can perform measurement at various rotational speeds because the absorber's natural frequency can be easily tuned by a feedback parameter. Experimental results demonstrate the feasibility of the proposed mass-measurement system.