Nonlinear natural control of an experimental beam

This paper is concerned with an experiment conducted at the NASA Langley Research Center that was designed to control the motion of a beam. The experimental setup consists of a free-free uniform beam acted upon by four electromagnetic force actuators, with the motion being measured by nine displacement sensors. The entire assembly is linked to a digital computer permitting on-line real-time computation of the control forces. The control scheme is based on the independent modal-space control method in conjuction with a nonlinear, on-off control law for the modal forces. The actuator forces are then synthesized from the modal forces by means of a linear transformation, resulting in quantized forces. The sensors’ data are processed by modal filters. It is observed that the independent controls are very effective in suppressing the motion of the beam, even though there is about a 50% difference between the actual and the analytically computed natural frequencies.