Characterization of Impact Response of a Plant Stem

A method for measuring mechanical response of a plant stem against small impact force is proposed. In this method, the mechanical characteristics of the plant stem against small force are determined by means of the "levitation mass method" (LMM). The LMM is a method for accurately measuring varying force without the use of force transducers. Mechanical characteristics of a plant stem were measured with high accuracy by means of an instrument developed base on the LMM. In the measurement, a mass that is levitated with a pneumatic linear bearing, and hence encounters negligible fiction, is made to collide with a plant stem under test. During the collision, the Doppler frequency shift of a laser beam reflecting from the mass is highly accurately measured using an optical interferometer. The velocity, position, acceleration and inertial force of the mass are calculated from the measured time-varying Doppler shift. The mechanical response of a plant stem against small impact loading is also characterized from the measured data