Instruments for Precise Mass Measurement under Weightless Conditions with Dynamic Vibration Absorbers

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This research studied mass measurement systems that uses a dynamic vibration absorber as a measuring device. The aim of this research was to develop mass measurement systems that can measure mass accurately even in weightless conditions. The obtained results are summarized as follows.1) The mass measurement systems were classified according to the motion of a mass to be measured, the type of the absorber, the method of vibration generation, the quantity to be measured, and the location of a mass to be measured.(2) A measurement apparatus was developed which used an active dynamic vibration absorber whose actuator was a voice coil motor. The controller used in the experiments was characterized by using exogenous signals synchronized with rotation for achieving automatic frequency tracking. It was shown experimentally that the designed controller eliminated the vibration at any rotational frequency. The experimental results demonstrated that the developed system measure mass accurately with an accuracy of 0.9 %.(3) A measurement apparatus equipped with dual inertial-mass actuators was developed for the experimental study. Both the inertial masses are driven by bimorphic piezoelectric actuators. Several mass measurements were carried out to study the performance of the developed mass measurement system. The experimental results demonstrated that the developed system measure mass accurately with an accuracy of 0.5 %.(4) A measurement apparatus using an undamped dynamic vibration absorber was developed. The measurement accuracy of the developed system was estimated experimentally when it was fixed on a rigid base and on a flexible structure. The results demonstrated that measurement accuracy was almost same in both the cases. It was also shown that the vibration of the table in transient states was reduced by increasing the excitation signal gradually from zero to an amplitude for measurement.