Impact force measurement using an inertial mass and a digitizer

A novel method for accurately measuring impact forces with small peak value and steep slope is proposed. In the method, a mass, which is levitated with a pneumatic linear bearing and hence encounters negligible friction, is made to collide with an object under test. The Doppler frequency shift of a laser beam reflecting from the mass is calculated by using an optical interferometer whose output signal waveform is recorded with a digitizer (i.e. a high-speed analogue-to-digital converter). The velocity, position, acceleration and inertial force of the mass are calculated from the measured varying frequency shift. The performance of the proposed method is demonstrated by evaluating the viscoelasticity of a small rubber block under an impact load with small peak value and steep slope. © 2006 IOP Publishing Ltd.