APPLICATION OF 2 CHAOS METHODS TO HIGHER HARMONIC CONTROL DATA

This paper presents two new data analysis methods which will reduce Hi gher Harmonic Control (HHC) flight test requirements. HHC is an active system which suppresses helicopter vibrations. These methods, origina lly used in the study or chaos, are the Poincare section and the Van d er Pol plane. Using flight test data from a McDonnell Douglas OH-6A HH C test aircraft, these methods show the following: 1) the limits of HH C vibration reduction; 2) determination of HHC controller type; and 3) that the HHC controller transfer matrix is predictable and repeatable when defined in the ''Rotor Time Domain.'' (This domain is a concept introduced in this paper. These benefits do not require an HHC equippe d helicopter, although they do require an instrumentation system insta lled. Finally, these methods can be implemented in real time in most i nstrumentation systems using only software changes and may be applicab le to other vibration control and flight testing problems.