Method of kinetic thrust measurement using observer of linear oscillatory actuator

The kinetic thrust of a linear motor (LM) is measured with a load cell connected between the LM and a load motor. The case of linear oscillatory actuator (LOA), the kinetic thrust obtained using this method is not accurate, because the inertial force affects the load cell under the high-speed reciprocating motion of the LOA. In this paper, we propose a novel method of measuring kinetic thrust using an observer-inputted output of the load cell and the displacement of the load motor, and examine the proposed method. The estimated kinetic thrust Fe obtained by the observer agrees with the kinetic thrust obtained by simulation. In the measurement, the ratio of Fe to √2KfI1 (Kf is the thrust constant of the LOA, I1 is the exciting current) is 0.93 at frequency f = 37.3 Hz. Fe decreases with increasing frequency because of the eddy currents in the yokes of the LOA. Therefore, it is considered that the proposed method is appropriate, as ascertained by simulation and measurement. In addition, it is necessary for the leaf spring of the LOA to be light and to have a fixed spring constant for the high-precision measurement of kinetic thrust.