Theoretical and Experimental Results on Active Vibration Dampers

The use of active feedback elements to produce damping of multiresonant structures is examined analytically, and the analysis is compared with experimental results obtained for a 48 in.‐long uniform beam damped at its midpoint. The analysis method involves an adaption of the conventional Nichols‐chart technique and appears to be quite reliable. By using commercially available components, a simultaneous reduction in resonant mobilities of resonances below 10 kc/sec is predicted and demonstrated. Reductions were proportional to the mobility values prior to active‐damping applications and also to the gain in the feedback path. The limitations on the amount of damping possible are imposed by stability conditions for the feedback loop, which in turn depend primarily upon the transfer function of the forcing and pickup components of this loop. The stability analysis for particular components used in the beam experiment is presented.