A method for determining a minimal set of adjustments for the blades of a
rotor supported by a supporting structure for reducing rotation-induced
vibration in the supporting structure at at least one harmonic rotation
order and/or for reducing track deviation while maintaining structure
vibration over at least one harmonic order within an acceptable limit. In
one embodiment, a relationship is established by which vibration of the
supporting structure may be calculated at harmonic orders of rotor
rotation from Fourier coefficients of adjustment, Fourier coefficients of
unit vibration influence and Fourier coefficients of vibration
measurements. Thereafter, a value is determined for each selected Fourier
coefficient of adjustment that provides a desired virtual reduction of
vibration of the supporting structure at the harmonic order of the
selected Fourier coefficient of adjustment using the vibration
relationship. A group of minimal sets of virtual blade adjustments are
determined for each type based on the determined value of the
corresponding selected Fourier coefficient of adjustment, and from the
group, a minimal set of virtual blade adjustments of each type is
determined based on its affect on the vibration relationship at at least
one harmonic order of rotor rotation other than the harmonic order of the
selected Fourier coefficient of adjustment. In another embodiment, track
measurements are provided that are resolved into corresponding Fourier
coefficients of track that are used to establish a relationship by which
track of the rotating blades may be calculated. Thereafter, a value is
determined for each selected Fourier coefficient of adjustment that
provides a desired reduction of track deviation using the track
relationship. A group of minimal sets of virtual blade adjustments is
determined based on the determined values, and from the group, a minimal
set of virtual blade adjustments is determined based on its affect on the
vibration relationship.