Moment excitation using two synchronized impact hammers

Moment mobilities are difficult to measure because there is no simple way to excite a structure with a well controlled moment. In this paper, a technique to apply a pure moment is presented. It is based on a simple approach which uses two impact forces applied respectively by two impact hammers. This paper will focus on the detailed description of the experimental system developed to obtain identical synchronized forces. Two hammers driven by electric motors controlled by a Digital Signal Processor are used. Experimental results are compared to theoretical predictions. It is shown that the technique yields to accurate measurements of moment frequency response functions (FRF).