Recent studies demonstrate that a key advantage of Flexible Matrix Composite (FMC) shaft technology is the ability to accommodate misalignments without need for segmenting or flexible couplings as required by conventional alloy and graphite/epoxy composite shafts. While this is indeed a very promising technology for rotorcraft driveshafts, the high damping loss-factor and thermal stiffness and damping sensitivities of the urethane matrix, makes FMC shafting more prone to self-heating and whirl instabilities. Furthermore, the relatively low bending stiffness and critical speeds of FMC shafts makes imbalance vibration a significant challenge to supercritical operation. To address these issues and advance the state-of-the-art, this research explores Active Magnetic Bearing (AMB) technology together with a robust-adaptive hybrid H feedback/Synchronous Adaptive Vibration Control law designed to ensure stable supercritical operation of a prototype FMC rotorcraft driveline. The effectiveness of the proposed new approach is demonstrated through analysis of a helicopter driveline testbed.
DeSmidt, H.A., Wang K.W. and Smith, E.C., ”Robust-Adaptive Magnetic Bearing Control of Flexible Matrix Composite Rotorcraft Driveline,” Journal of the American Helicopter Society, Vol. 53, No. 2, pp. 115-124., 2008.