US 5,669,582 A · Method and apparatus for reducing unwanted sideways motion in the aft cabin and roll-yaw upsets of an airplane due to atmospheric turbulence and wind gusts

Abstract

A method and apparatus for reducing the unwanted sideways motion of an airplane by reducing the lateral side loads and upsets caused by atmospheric turbulence and gusts is disclosed. A rudder modification command that causes the rudder command of the airplane to be changed in a manner that relieves the net force across the vertical stabilizer of the airplane caused by atmospheric turbulence and gusts is produced. More specifically, the pressure differential across opposite sides of the vertical stabilizer is measured and used to produce a rudder deflection value that is roll rate and yaw rate compensated. The compensated deflection value is high-pass filtered with a corner frequency that is twenty-five percent (25%) of the Dutch roll frequency of the airplane. The result is a first rudder deflection value that is subtractively combined with a second rudder deflection value. The second rudder deflection value is derived by gain adjusting and low-pass filtering the inertial sideslip angle rate value produced by the airplane's yaw damper. The low-pass filter has a corner frequency that is also twenty-five percent (25%) of the Dutch roll frequency of the airplane. The combined rudder deflection value is modified by a steady sideslip gain value and filtered by a gain shaping filter. The gain shaping filter increases the gain above the Dutch roll frequency of the airplane. The resultant rudder modification command is subtractively combined with the yaw damper rudder command to produce a rudder command. Preferably, a flow separation monitor is included to prevent the rudder modification command from producing a rudder command that exceeds allowable structural limits. Also, preferably, the rudder modification command is used to produce a lateral control command that is used to suppress rigid body roll response and improve handling qualities by gain adjusting and low-pass filtering the rudder modification command.

Claims39

Dependent claims

A method of producing a rudder modification command for reducing unwanted sideways motion in the aft cabin of an airplane comprising:

determining the pressure differential across the opposite sides of the vertical stabilizer of the airplane;
producing an airmass sideslip angle value based on said pressure differential;
roll and yaw compensating said airmass sideslip angle value to produce a compensated airmass sideslip angle value;
high-pass filtering said compensated airmass sideslip angle value with a filter having a corner frequency that is approximately twenty-five percent (25%) of the Dutch roll frequency of the airplane to produce a first rudder deflection value;
deriving a second rudder deflection value by gain adjusting and low-pass filtering an inertially derived sideslip angle rate value with a filter having a corner frequency that is approximately twenty-five percent (25%) of the Dutch roll frequency of the airplane;
subtractively combining said first and second rudder deflection values;
and
gain shape filtering said combined first and second rudder deflection values to produce a rudder modification command, said gain shape filtering gain modifying said combined first and second rudder deflection values as a function of the Dutch roll frequency of the airplane.

5 more elements

A system for producing a rudder modification command suitable for reducing unwanted sideways motion in the aft cabin of an airplane when applied to the rudder of the airplane, said system comprising:

(a) a pressure differential sensor for measuring the differential pressure across the opposite sides of the vertical stabilizer of an airplane;
(b) a rudder modification command subsystem connected to said pressure differential sensor, said rudder modification command subsystem including:
(1) a divider for dividing pressure differential measurements by an impact pressure variable, q.sub.c, to produce a pressure coefficient value;
(2) a scaler for scaling said pressure coefficient value by a factor that converts said pressure coefficient value into an airmass sideslip angle value;
(3) a roll and yaw rate compensator for compensating said airmass sideslip angle value to produce a compensated airmass sideslip angle value;
(4) a high-pass filter for filtering said compensated airmass sideslip angle value and producing a first rudder deflection value, said high-pass filter having a corner frequency that is approximately twenty-five percent (25%) of the Dutch roll frequency of the airplane;
(5) a low-pass filter for filtering an inertially derived sideslip angle rate value and producing a second rudder deflection value, said low-pass filter having a corner frequency that is approximately twenty-five percent (25%) of the Dutch roll frequency of the airplane;
(6) a subtractor for combining said first and second rudder deflection values;
and
(7) a gain shape filter for filtering said combined first and second rudder deflection values to produce a rudder modification command, said gain shape filter gain modifying said combined first and second rudder deflection values as a function of the Dutch roll frequency of the airplane.

7 more elements

Dependencies are inferred from the claim text.

Method and apparatus for reducing unwanted sideways motion in the aft cabin and roll-yaw upsets of an airplane due to atmospheric turbulence and wind gusts

Life of this patent

Method and apparatus for reducing unwanted sideways motion in the aft cabin and roll-yaw upsets of an airplane due to atmospheric turbulence and wind gusts

Life of this patent

Abstract

Claims39