Rotor blade force track sensing system and automatic span tracking system
AssigneeTextron Inc.
InventorMilford R. Murphy
Life of this patent
Estimating the term…
Abstract
In eliminating one-per-rev vibration in a helicopter due to rotor unbalance, a one-per-rev vibration signal manifestation of rotor unbalance is generated and sampled when the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor. A difference signal is generated from the samples to represent by magnitude and phase the character of the unbalance. The rotor is modified in magnitude proportional to the magnitude of the signal and in direction dependent upon the span and chord components of the signal. In one aspect the force track error signal is applied to the input of a cyclic pitch control actuator system dynamically to automatically correct span unbalance forces.
Claims23
The method of minimizing one-per-rev vibration in a helicopter due to rotor unbalance which comprises:
- generating a one-per-rev vibration signal for at least two blades of the rotor as a manifestation of rotor unbalance,
- sampling said signals when each of the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor, and
- generating a difference signal by comparing samples of said signals from each of the rotor blades to represent by magnitude and phase the character of said unbalance.
The method of minimizing one-per-rev vibrations in a helicopter due to a rotor unbalance which comprises:
- generating a one-per-rev vibration signal manifestation of rotor unbalance,
- sampling said signal when the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor,
- generating a difference signal from said samples to represent by magnitude and phase the character of said unbalance, and
- resolving the signal into span and chord components to isolate out of track conditions and provide a guide for required adjustment of vibration inducing rotor unbalance.
The method of minimizing one-per-rev vibration in a helicopter airframe when supported by a mast driven rotor which comprises:
- a. rotating said rotor at normal rotor speed and zero lift,
- b. generating a signal representative of unbalance force on said mast due to displacement of the center of gravity of the rotor from the mast axis,
- c. modifying the rotor in magnitude proportional to the magnitude of said signal and in direction dependent upon the span and chord components of said signal,
- d. hovering said helicopter at normal rotor speed,
- e. generating a signal representative in phase and magnitude of unbalance moments on said mast due to aerodynamic forces on said mast, and
- f. modifying the aerodynamics of said rotor in magnitude proportional to the magnitude of said signal and direction dependent upon said components of said signal.
A system to aid in minimizing one-per-rev vibration in a helicopter airframe when supported by a mast driven rotor which comprises:
- a. means to generate a signal representative of unbalance force on said mast due to displacement of the center of gravity of the rotor from the mast axis when rotating at normal rotor speed and zero lift, whereby the rotor may be modified in magnitude proportional to the magnitude of said signal and in direction dependent upon the span and chord components of said signal, and
- b. means to generate a signal representative in phase and magnitude of unbalance moments on said mast due to aerodynamic forces on said mast when hovering said helicopter at normal rotor speed whereby the aerodynamics of said rotor may be modified in magnitude proportional to the magnitude of said signal and direction dependent upon said components of said signal.
A system for sensing and comparing unbalanced vibrational forces exerted by rotor blades of a rotary wing aircraft which are transmitted through its mast to a rotor support mounting, comprising:
- a. generator means to generate a first position signal when a first rotor blade is aligned with a reference direction fixed with respect to said mounting structure and a second position signal when a second rotor blade is aligned with said reference direction,
- b. vibration sensing means responsive to said unbalanced forces exerted in said reference direction for providing a vibration signal,
- c. first sampling means connected to said vibration sensing means and responsive to the first position signal for selecting as a first force signal sample the value of the vibration signal when the first blade is aligned with the reference direction,
- d. second sampling means connected to the vibration sensing means and responsive to the second position signal for selecting as a second force signal sample the value of the vibration signal when the second blade is aligned with the reference direction, and
- e. means connected between the first and second sampling means for comparing the first force signal sample with the second force signal sample.
Dependencies are inferred from the claim text.