Application of a Notch Digital Filter to Elimination of Sinusoidal Disturbances from Helicopter Flight Data

摘要

Helicopter flight data, especially measurements of linear accelerations and angular velocities, are typically corrupted by sinusoidal deterministic disturbances, that are associated with the rotor frequency and its harmonics. In an effort to eliminate these disturbances without distorting the underlying trends, a new digital notch filter, developed under a research agreement between Aeronautical Research Laboratories and the University of Newcastle, has been modified and implemented on the ARL ELXSI 6400 computer. In this memo, the filter is described and the frequency and transient response characteristics are summarised. Practical considerations arising out of application of single and cascaded filters to Sea King flight data are discussed, and the performance of the new filter is compared with that of comparable Butterworth filters.