ACTIVE CONTROL OF WAVE-TYPE VIBRATION ENERGY FOR IMPROVED STRUCTURAL RELIABILITY

Degradation of the structural integrity of flexible, composite structu res occurs over time when subjected to vibratory disturbances. Active vibration control methods present a way to minimize vibration levels i n structures for improved structural reliability. Control architecture s which have been developed and specialized for vibration reduction in flexible structures are presented. These are based on the interpretat ion of vibration behavior in the form of waveform propagation and moda l response. To reduce the potential energy of a structure with vibrati on characteristics dominated by standing waves, a nonlinear rate-feedb ack scheme and a dual-controller scheme for both transient and steady- state vibration minimization have been developed. Vibration in flexibl e structures may also be dominated by travelling waves with standing w ave components superimposed. A new concept, the total energy absorptio n (TEA) compensator, allows control of stationary and propagating wave forms in flexible structures based on feedback of wave-type energy-fie ld measurements. The TEA formulation considers vibration energy-fields in the structure in the form of complex intensity and energy density for effective vibration minimization. Lightweight piezoelectric materi als and accelerometers are used as sensors to estimate the energy-fiel d parameters. Piezoelectric materials are used as distributed actuator s to drive the flexible structure. Numerical and experimental results on the reduction of the total vibrational energy in flexible structure s using these active control methods are presented.