Measurement of Mass of Spherical Model by Magnetic Suspension and Balance System

This paper aims to verify the feasibility of measuring the mass of a spherical model using a Magnetic Suspension and Balance System (MSBS). The MSBS was developed to support models and conduct wind tunnel tests without airflow interference. The MSBS levitates the model by using magnetic force. Therefore, physical support devices are unnecessary during wind tunnel tests. In this study, a spherical model levitated in the air using the MSBS was excited at a constant frequency. The mass of the spherical model was calculated based on the relationship between the applied external force, model amplitude, natural frequency, and excitation frequency during oscillation. The applied external force was electromagnetic force, and it was determined based on the relationship between the electromagnetic force and the distance between permanent magnets positioned at the top of the MSBS and inside the spherical model. The amplitude was calculated using the sensor voltage and the width of the laser. Additionally, the natural frequency was determined based on the bode plot of the open loop transfer function. Consequently, this method confirmed the feasibility of measuring the mass of the model using the MSBS. In further study, the model will be levitated in water using the MSBS and excited to experimentally measure the added mass.