Neural net controller for noise and vibration reduction

A system for actively controlling the noise and vibration produced by the blades of a rotorcraft as measured by a plurality of noise and vibration sensors mounted on the rotor blades and within the rotorcraft by altering the aerodynamic characteristics of the rotor blades, comprising:

• a preprocessing filtering module which isolates the measured noise and vibration desired to be controlled;
• a sensor for measuring the rotational rate at which the rotor of the rotorcraft is operating;
• means for determining the angular positions of said blades;
• a reference signal;
• an adaptive feed-forward three-layer controller neural network adapted to receive as input said reference signal and a positional velocity of said rotorcraft and produce an adjustment signal wherein said adjustment signal comprises multiple phase and amplitude shifted harmonics of said reference signal;
• means for altering the airflow over said blades;
• a feed-forward three-layer emulator neural network trained to model the dynamics of the blade as well as the results and transfer function of changes induced by said altering means wherein said model receives as input the state of said altering means, the positional velocity of said rotorcraft, and the relative positions of said blades, calculates estimated vibration and noise envelope signals, compares the estimated signals with said sensed vibration and noise envelope signals, produces plant gradient signals representing the errors in the emulator model of the plant, and feeds back said plant gradient signals to said controller neural network to allow said controller neural network to adapt itself during runtime using a gradient descent algorithm based on said plant gradient output of said emulator neural network and said sensor preprocessing module;
• and
• a time-based filter which produces time-based representations of the inputs to said emulator neural network and said controller neural network comprising delay lines which store the input values for a given time period and permit access to each of the stored values.