Optimization For Rotor Track And Balance

Abstract

This investigation examines optimization methods for minimizing undesired vibrations in a helicopter. An iterative weighting system for adjusting emphasis of different flight conditions is implemented as an extension of current weighting schemes and performance results are discussed. Next, a cascaded method of least squares optimization is applied to incorporate minimization of vibrations at higher harmonics. A real coded genetic algorithm to prescribe integer-valued rotor modifications is then executed. Optimization methods are simulated using a linear sensitivity model to demonstrate the effects of rotor adjustments, specifically modifications in pitch change rod, outboard tabs, and hub weights on the Sikorsky S-76C++ aircraft. Applying an iterative flight condition weighting scheme with integer-bounded rotor adjustments while extending the range of harmonic frequencies included in the analysis develops a robust prescription of rotor adjustments. By virtue of their integer-based properties, these prescribed adjustments are more realistic and eliminate previously occurring loss of accuracy in implementation.