Dynamic system characterization and design using mechanical impedance representations
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Vibration testing is a critical aspect in the qualification of fieldable hardware as dynamic environments are typically design drivers. However, it is difficult to provide representative boundary conditions for component testing and the presence of an ill-matched boundary condition can alter the test outcomes. To achieve more realistic boundary conditions, test fixtures could be strategically designed such that they emulate the impedance of the next level of assembly. The body of work presented herein proposes various strategies for matching the drive point impedance of a target frequency response function (FRF) using undamped lumped parameter emulators. Two primary techniques have been developed to accomplish this impedance matching: a constrained exhaustive search algorithm and a constrained optimization algorithm. The constrained exhaustive search exploits newly identified high and low frequency limits in order to minimize the number of parameters that must be searched. The optimization algorithm provides an innovative methodology for the identification of a comprehensive and bounded design space and presents a novel implementation of particle swarm optimization that produces an optimized set of parameters for every identified physically realizable topology. This resultant emulator design space provides a basis from which low-complexity, low-cost fixtures can be constructed, thus offering an attainable path for better matching of boundary conditions and more representative vibration testing.