Instrument calibration method including compensation of centripetal acceleration effect
First Claim
1. A method for determining the east gyro bias error of the inertial system of an aircraft comprising the steps of:
- a) providing initial estimates of crab angle, ratio of crab angle to centripetal acceleration and lever arm;
thenb) taxiing said aircraft; and
c) observing aircraft velocity with respect to an inertial axis system; and
d) observing heading angle and rate of change thereof;
thene) converting said aircraft velocity to heading and cross-heading velocity components in an aircraft body axis reference system; and
f) estimating centripetal acceleration;
theng) estimating the cross-track velocity of said taxiing aircraft;
thenh) integrating said cross track velocity to estimate the cross-track position of said taxiing aircraft; and
i) generating Kalman gains for the value of crab angle, ratio of crab angle to centripetal acceleration, lever arm and aircraft velocity with respect to said inertial reference axis;
thenj) obtaining error values by multiplying said cross-track position by said Kalman gains;
thenk) generating optimum estimates of cross-track velocity by combining said error values with said cross-heading velocity; and
thenl) generating east gyro bias error from said optimum estimates of cross-track velocity.
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Accused Products
Abstract
A method and apparatus are provided for addressing the effect of centripetal acceleration upon estimates of cross-track velocity, for determination of east gyro bias error, generated with a taxiing aircraft. After initial estimates of crab angle, ratio of crab angle to centripetal acceleration and lever arm are provided, velocity, heading angle and heading angle rate are observed as the aircraft taxis. An estimated value of centripetal acceleration is taken as the product of heading angle rate and heading velocity. Cross-track velocity is computed from cross-heading velocity and this is integrated to generate cross-track position. A Kalman filter generates various gains, including one associated with the ratio of crab angle to centripetal acceleration, for error allocation. The product of the Kalman gain pertaining to crab angle ratio and the computed cross-track position provides a crab angle ratio error that is integrated and multiplied by the estimated centripetal acceleration to provide an optimum estimate of the portion of crab angle that is associated with centripetal acceleration.
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Citations
19 Claims
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1. A method for determining the east gyro bias error of the inertial system of an aircraft comprising the steps of:
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a) providing initial estimates of crab angle, ratio of crab angle to centripetal acceleration and lever arm;
thenb) taxiing said aircraft; and c) observing aircraft velocity with respect to an inertial axis system; and d) observing heading angle and rate of change thereof;
thene) converting said aircraft velocity to heading and cross-heading velocity components in an aircraft body axis reference system; and f) estimating centripetal acceleration;
theng) estimating the cross-track velocity of said taxiing aircraft;
thenh) integrating said cross track velocity to estimate the cross-track position of said taxiing aircraft; and i) generating Kalman gains for the value of crab angle, ratio of crab angle to centripetal acceleration, lever arm and aircraft velocity with respect to said inertial reference axis;
thenj) obtaining error values by multiplying said cross-track position by said Kalman gains;
thenk) generating optimum estimates of cross-track velocity by combining said error values with said cross-heading velocity; and
thenl) generating east gyro bias error from said optimum estimates of cross-track velocity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for estimating the cross-track velocity of an aircraft as it taxis comprising the steps of:
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a) providing initial estimates of crab angle, ratio of crab angle to centripetal acceleration and lever arm;
thenb) observing aircraft velocity with respect to an inertial axis system; and c) observing heading angle and rate of change thereof;
thend) converting said aircraft velocity to heading and cross-heading velocity components in an aircraft body axis reference system; and e) estimating centripetal acceleration;
thenf) estimating the cross-track velocity of said taxiing aircraft;
theng) integrating said cross track velocity to estimate the cross-track position of said taxiing aircraft; and h) generating Kalman gains for the value of crab angle, ratio of crab angle to centripetal acceleration, lever arm and aircraft velocity with respect to said inertial reference axis;
theni) obtaining error values by multiplying said cross-track position by said Kalman gains; and
thenj) generating optimum estimates of cross-track velocity by combining said error values with said cross-heading velocity. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. Apparatus for determining the east gyro bias error of the inertial system of an aircraft comprising, in combination:
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a) means for generating initial estimates of crab angle, ratio of crab angle to centripetal acceleration and lever arm; b) means for measuring the velocity of said aircraft with respect to an inertial axis system as it taxis; c) means for measuring heading angle and its rate change while said aircraft taxis; d) means for converting said taxiing velocity to a heading velocity component and a cross-heading velocity component in an aircraft body axis reference system; e) means for computing centripetal acceleration; f) an integrator for generating a cross-track position error from said cross-track velocity; g) a statistical filter, responsive to an error model, for generating Kalman gains with respect to crab angle, ratio of crab angle to centripetal acceleration, lever arm and aircraft taxi velocity with respect to said inertial reference axes; h) a multiplier for generating error values by multiplying said cross-track position error by said Kalman gains; i) means for generating optimum estimates of cross-track velocity by combining said error values with taxiing velocity with respect to said body axis system; and j) means for generating said east gyro bias error from said optimum estimates of cross-track velocity.
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19. On-board apparatus for determining the cross-track velocity of a taxiing aircraft comprising, in combination:
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a) means for generating initial estimates of crab angle, ratio of crab angle to centripetal acceleration and lever arm; b) means for measuring the velocity of said aircraft with respect to an inertial axis system as it taxis; c) means for measuring heading angle and its rate change while said aircraft taxis; d) means for converting said taxiing velocity to a heading velocity component and a cross-heading velocity component in an aircraft body axis reference system; e) means for computing centripetal acceleration; f) an integrator for generating a cross-track position error from said cross-track velocity; g) a statistical filter, responsive to an error model, for generating Kalman gains with respect to crab angle, ratio of crab angle to centripetal acceleration, lever arm and aircraft taxi velocity with respect to said inertial reference axes; h) a multiplier for generating error values by multiplying said cross-track position error by said Kalman gains; and i) means for generating optimum estimates of cross-track velocity by combining said error values with taxiing velocity with respect to said body axis system.
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Specification