Method and apparatus for finding aircraft position by integrating accelerations less time averages
First Claim
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1. A method for determining the position of an aircraft for radar mapping, comprising:
- providing a processor in the airplane;
providing a master navigation system coupled to the processor and including an aircraft speedometer for measuring a forward x-speed vXUAX (t), a lateral horizontal position sensor for measuring a lateral y-position pYUAX (t), and an altimeter for measuring a vertical z-position pZUAX (t);
providing a slave system including an inertial measurement unit coupled to the processor and further including an x-accelerometer for generating a forward-direction horizontal acceleration signal ax (t), a y-accelerometer for generating a lateral horizontal acceleration signal ay (t), and a z-accelerometer for generating a vertical acceleration signal ax (t);
(a) inputting the forward-direction acceleration signal ax (t) from the inertial system to the processor;
time-averaging over a time interval T the acceleration signal ax (t) to obtain a first x-adjustment ax (t);
subtracting the first x-adjustment ax (t) from the acceleration signal ax (t) to obtain an adjusted acceleration signal a'"'"'x (t);
integrating the adjusted acceleration signal a'"'"'x (t) over the interval T to obtain a velocity vx "(t) according to ##EQU10## time-averaging the velocity v"x (t) over the interval T to obtain a vx -adjustment vx (t);
subtracting the vx -adjustment vx (t) from the velocity v"x (t) to obtain a forward airplane speed vXIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">ν
.sub.XIMU (t)=ν
.sub.X (t)-ν
".sub.X (t) (5)estimating by method of least squares, from a difference between the speed vXIMU (t) and the speed measurement of the speedometer, an average acceleration aX0 and an average speed vX0 ;
creating a correction term vXFIT (t) from a sum of the average speed vX0 and a time integration of aX0 according to ##EQU11## correcting the speed vXIMU (t) in the desired flight direction by adding the correction term vXFIT (t) thereto to obtain a corrected flight speed vXKORR (t) according to
space="preserve" listing-type="equation">ν
.sub.XKORR (t)=ν
.sub.XIMU (t)+ν
.sub.XFIT (t)(b) inputting the lateral-direction acceleration signal ay (t) from the inertial system to the processor;
time-averaging over a time interval T the acceleration signal ay (t) to obtain a first y-adjustment ay (t);
subtracting the first y-adjustment ay (t) from the acceleration signal ay (t) to obtain an adjusted acceleration signal a'"'"'y (t);
integrating the adjusted acceleration signal a'"'"'y (t) over the interval T to obtain a velocity vy "(t) according to ##EQU12## time-averaging the velocity v"y (t) over the interval T to obtain a vy -adjustment vy (t);
subtracting the first y-adjustment vy (t) from the velocity v"y (t) to obtain an adjusted velocity signal v'"'"'y (t);
integrating the adjusted velocity signal v'"'"'y (t) over the interval T to obtain a position py '"'"'(t) according to ##EQU13## time-averaging the position p'"'"'y (t) over the interval T to obtain a py -adjustment py (t);
subtracting the py -adjustment py (t) from the velocity p'"'"'y (t) to obtain a forward airplane speed pYIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">p.sub.YIMU (t)=p'"'"'.sub.Y (t)-p'"'"'.sub.Y (t) (9)estimating by method of least squares, from a difference between the speed pYIMU (t) and the speed measurement of the speedometer, an average acceleration aY0 and an average speed vY0 ;
creating a correction term pYFIT (t) from a sum of the average speed vY0 and a time integration of aY0 according to ##EQU14## correcting the speed pYIMU (t) in the desired flight direction by adding the correction term pYFIT (t) thereto to obtain a corrected flight speed pYKORR (t) according to
space="preserve" listing-type="equation">p.sub.YKORR (t)=p.sub.YIMU (t)+p.sub.YFIT (t)correcting the motion of the aircraft along the desired flight path according to the value of pYKORR (t);
(c) inputting the lateral-direction acceleration signal az (t) from the inertial system to the processor;
time-averaging over a time interval T the acceleration signal az (t) to obtain a first z-adjustment az (t);
subtracting the first z-adjustment az (t) from the acceleration signal az (t) to obtain an adjusted acceleration signal a'"'"'z (t);
integrating the adjusted acceleration signal a'"'"'z (t) over the interval T to obtain a velocity vz "(t) according to ##EQU15## time-averaging the velocity v"z (t) over the interval T to obtain a vz -adjustment vz (t);
subtracting the first z-adjustment vz (t) from the velocity vz (t) to obtain an adjusted velocity signal v'"'"'z (t);
integrating the adjusted velocity signal v'"'"'z (t) over the interval T to obtain a position pz '"'"'(t) according to ##EQU16## time-averaging the position p'"'"'z (t) over the interval T to obtain a pz -adjustment pz (t);
subtracting the pz -adjustment pz (t) from the velocity p"z (t) to obtain a forward airplane speed pZIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">p.sub.ZIMU (t)=p'"'"'.sub.z (t)-p'"'"'.sub.z (t) (15)estimating by method of least squares, from a difference between the speed pZIMU (t) and the speed measurement of the speedometer, an average acceleration aZ0 and an average speed vZ0 ;
creating a correction term pZFIT (t) from a sum of the average speed vZ0 and a time integration of aZ0 according to ##EQU17## correcting the speed pZIMU (t) in the desired flight direction by adding the correction term pZFIT (t) thereto to obtain a corrected flight speed pZKORR (t) according to
space="preserve" listing-type="equation">p.sub.ZKORR (t)=p.sub.ZIMU (t)+p.sub.ZFIT (t) (29)andcompensating the radar mapping according to the values of vXKORR (t), pYKORR (t), and pZKORR (t).
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Abstract
A method and apparatus for short-range position determination of aircraft, used for preventing errors in radar mapping from position inaccuracies, finds velocity in the x-direction (flight direction) by integrating accelerometer outputs. The accelerometer values are averaged over a time interval and then the average is subtracted from the instantaneous signal value; this difference, called adjusted acceleration, is integrated over time to yield a velocity. In turn, this velocity is time-averaged and the time average is subtracted from the instantaneous velocity. The resulting adjustment velocity is subtracted from the output of aircraft speedometer, and the difference is used to generate estimates of the average aircraft speed and acceleration by the method of least squares. These estimates are used to create a speed correction term for correcting the flight speed. The same process is used for positions in the y-direction and z-direction (vertical), except that an additional integration, time-average, and subtraction are involved for each.
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4 Claims
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1. A method for determining the position of an aircraft for radar mapping, comprising:
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providing a processor in the airplane; providing a master navigation system coupled to the processor and including an aircraft speedometer for measuring a forward x-speed vXUAX (t), a lateral horizontal position sensor for measuring a lateral y-position pYUAX (t), and an altimeter for measuring a vertical z-position pZUAX (t); providing a slave system including an inertial measurement unit coupled to the processor and further including an x-accelerometer for generating a forward-direction horizontal acceleration signal ax (t), a y-accelerometer for generating a lateral horizontal acceleration signal ay (t), and a z-accelerometer for generating a vertical acceleration signal ax (t); (a) inputting the forward-direction acceleration signal ax (t) from the inertial system to the processor; time-averaging over a time interval T the acceleration signal ax (t) to obtain a first x-adjustment ax (t); subtracting the first x-adjustment ax (t) from the acceleration signal ax (t) to obtain an adjusted acceleration signal a'"'"'x (t); integrating the adjusted acceleration signal a'"'"'x (t) over the interval T to obtain a velocity vx "(t) according to ##EQU10## time-averaging the velocity v"x (t) over the interval T to obtain a vx -adjustment vx (t); subtracting the vx -adjustment vx (t) from the velocity v"x (t) to obtain a forward airplane speed vXIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">ν
.sub.XIMU (t)=ν
.sub.X (t)-ν
".sub.X (t) (5)estimating by method of least squares, from a difference between the speed vXIMU (t) and the speed measurement of the speedometer, an average acceleration aX0 and an average speed vX0 ; creating a correction term vXFIT (t) from a sum of the average speed vX0 and a time integration of aX0 according to ##EQU11## correcting the speed vXIMU (t) in the desired flight direction by adding the correction term vXFIT (t) thereto to obtain a corrected flight speed vXKORR (t) according to
space="preserve" listing-type="equation">ν
.sub.XKORR (t)=ν
.sub.XIMU (t)+ν
.sub.XFIT (t)(b) inputting the lateral-direction acceleration signal ay (t) from the inertial system to the processor; time-averaging over a time interval T the acceleration signal ay (t) to obtain a first y-adjustment ay (t); subtracting the first y-adjustment ay (t) from the acceleration signal ay (t) to obtain an adjusted acceleration signal a'"'"'y (t); integrating the adjusted acceleration signal a'"'"'y (t) over the interval T to obtain a velocity vy "(t) according to ##EQU12## time-averaging the velocity v"y (t) over the interval T to obtain a vy -adjustment vy (t); subtracting the first y-adjustment vy (t) from the velocity v"y (t) to obtain an adjusted velocity signal v'"'"'y (t); integrating the adjusted velocity signal v'"'"'y (t) over the interval T to obtain a position py '"'"'(t) according to ##EQU13## time-averaging the position p'"'"'y (t) over the interval T to obtain a py -adjustment py (t); subtracting the py -adjustment py (t) from the velocity p'"'"'y (t) to obtain a forward airplane speed pYIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">p.sub.YIMU (t)=p'"'"'.sub.Y (t)-p'"'"'.sub.Y (t) (9)estimating by method of least squares, from a difference between the speed pYIMU (t) and the speed measurement of the speedometer, an average acceleration aY0 and an average speed vY0 ; creating a correction term pYFIT (t) from a sum of the average speed vY0 and a time integration of aY0 according to ##EQU14## correcting the speed pYIMU (t) in the desired flight direction by adding the correction term pYFIT (t) thereto to obtain a corrected flight speed pYKORR (t) according to
space="preserve" listing-type="equation">p.sub.YKORR (t)=p.sub.YIMU (t)+p.sub.YFIT (t)correcting the motion of the aircraft along the desired flight path according to the value of pYKORR (t); (c) inputting the lateral-direction acceleration signal az (t) from the inertial system to the processor; time-averaging over a time interval T the acceleration signal az (t) to obtain a first z-adjustment az (t); subtracting the first z-adjustment az (t) from the acceleration signal az (t) to obtain an adjusted acceleration signal a'"'"'z (t); integrating the adjusted acceleration signal a'"'"'z (t) over the interval T to obtain a velocity vz "(t) according to ##EQU15## time-averaging the velocity v"z (t) over the interval T to obtain a vz -adjustment vz (t); subtracting the first z-adjustment vz (t) from the velocity vz (t) to obtain an adjusted velocity signal v'"'"'z (t); integrating the adjusted velocity signal v'"'"'z (t) over the interval T to obtain a position pz '"'"'(t) according to ##EQU16## time-averaging the position p'"'"'z (t) over the interval T to obtain a pz -adjustment pz (t); subtracting the pz -adjustment pz (t) from the velocity p"z (t) to obtain a forward airplane speed pZIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">p.sub.ZIMU (t)=p'"'"'.sub.z (t)-p'"'"'.sub.z (t) (15)estimating by method of least squares, from a difference between the speed pZIMU (t) and the speed measurement of the speedometer, an average acceleration aZ0 and an average speed vZ0 ; creating a correction term pZFIT (t) from a sum of the average speed vZ0 and a time integration of aZ0 according to ##EQU17## correcting the speed pZIMU (t) in the desired flight direction by adding the correction term pZFIT (t) thereto to obtain a corrected flight speed pZKORR (t) according to
space="preserve" listing-type="equation">p.sub.ZKORR (t)=p.sub.ZIMU (t)+p.sub.ZFIT (t) (29)and compensating the radar mapping according to the values of vXKORR (t), pYKORR (t), and pZKORR (t). - View Dependent Claims (2)
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3. A device for determining the position of an aircraft for radar mapping, comprising:
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a processor in the airplane; a master navigation system coupled to the processor and including an aircraft speedometer for measuring a forward x-speed vXUAX (t), a lateral horizontal position sensor for measuring a lateral y-position pYUAX (t), and an altimeter for measuring a vertical z-position pZUAX (t); a slave system including an inertial measurement unit coupled to the processor and further including an x-accelerometer for generating a forward-direction horizontal acceleration signal ax (t), a y-accelerometer for generating a lateral horizontal acceleration signal ay (t), and a z-accelerometer for generating a vertical acceleration signal ax (t); (a) means for inputting the forward-direction acceleration signal ax (t) from the inertial system to the processor; means for time-averaging over a time interval T the acceleration signal ax (t) to obtain a first x-adjustment ax (t); means for subtracting the first x-adjustment ax (t) from the acceleration signal ax (t) to obtain an adjusted acceleration signal a'"'"'x (t); means for integrating the adjusted acceleration signal a'"'"'x (t) over the interval T to obtain a velocity vx "(t) according to ##EQU19## means for time-averaging the velocity v"x (t) over the interval T to obtain a vx -adjustment vx (t); means for subtracting the vx -adjustment vx (t) from the velocity v"x (t) to obtain a forward airplane speed vXIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">ν
.sub.XIMU (t)=ν
.sub.x (t)-ν
".sub.X (t) (5)means for estimating by method of least squares, from a difference between the speed vXIMU (t) and the speed measurement of the speedometer, an average acceleration aX0 and an average speed vX0 ; means for creating a correction term vXFIT (t) from a sum of the average speed vX0 and a time integration of aX0 according to ##EQU20## means for correcting the speed vXIMU (t) in the desired flight direction by adding the correction term vXFIT (t) thereto to obtain a corrected flight speed vXKORR (t) according to
space="preserve" listing-type="equation">ν
.sub.XKORR (t)=ν
.sub.XIMU (t)+ν
.sub.XFIT (t)(b) means for inputting the lateral-direction acceleration signal ay (t) from the inertial system to the processor; means for time-averaging over a time interval T the acceleration signal ay (t) to obtain a first y-adjustment ay (t); means for subtracting the first y-adjustment ay (t) from the acceleration signal ay (t) to obtain an adjusted acceleration signal a'"'"'y (t); means for integrating the adjusted acceleration signal a'"'"'y (t) over the interval T to obtain a velocity vy "(t) according to ##EQU21## means for time-averaging the velocity v"y (t) over the interval T to obtain a vy -adjustment vy (t); means for subtracting the first y-adjustment vy (t) from the velocity vy (t) to obtain an adjusted velocity signal v'"'"'y (t); means for integrating the adjusted velocity signal v'"'"'y (t) over the interval T to obtain a position py '"'"'(t) according to ##EQU22## means for time-averaging the position p'"'"'y (t) over the interval T to obtain a py -adjustment py (t); means for subtracting the py -adjustment py (t) from the velocity p'"'"'y (t) to obtain a forward airplane speed pYIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">p.sub.YIMU (t)=p'"'"'.sub.Y (t)-p'"'"'.sub.Y (t)means for estimating by method of least squares, from a difference between the speed pYIMU (t) and the speed measurement of the speedometer, an average acceleration aY0 and an average speed vY0 ; means for creating a correction term pYFIT (t) from a sum of the average speed vY0 and a time integration of aY0 according to ##EQU23## means for correcting the speed pYIMU (t) in the desired flight direction by adding the correction term pYFIT (t) thereto to obtain a corrected flight speed pYKORR (t) according to
space="preserve" listing-type="equation">p.sub.YKORR (t)=p.sub.YIMU (t)+p.sub.YFIT (t)means for correcting the motion of the aircraft along the desired flight path according to the value of pYKORR (t); (c) means for inputting the lateral-direction acceleration signal az (t) from the inertial system to the processor; means for time-averaging over a time interval T the acceleration signal az (t) to obtain a first z-adjustment az (t); means for subtracting the first z-adjustment az (t) from the acceleration signal az (t) to obtain an adjusted acceleration signal a'"'"'z (t); means for integrating the adjusted acceleration signal a'"'"'z (t) over the interval T to obtain a velocity vz "(t) according to ##EQU24## means for time-averaging the velocity v"z (t) over the interval T to obtain a vz -adjustment vz (t); means for subtracting the first z-adjustment vz (t) from the velocity vz (t) to obtain an adjusted velocity signal v'"'"'z (t); means for integrating the adjusted velocity signal v'"'"'z (t) over the interval T to obtain a position pz '"'"'(t) according to ##EQU25## means for time-averaging the position p'"'"'z (t) over the interval T to obtain a pz -adjustment pz (t); means for subtracting the pz -adjustment pz (t) from the velocity p'"'"'z (t) to obtain a forward airplane speed pZIMU (t) in the desired flight direction according to
space="preserve" listing-type="equation">p.sub.ZIMU (t)=p'"'"'.sub.Z (t)-p'"'"'.sub.Z (t)means for estimating by method of least squares, from a difference between the speed pZIMU (t) and the speed measurement of the speedometer, an average acceleration aZ0 and an average speed vZ0 ; means for creating a correction term pZFIT (t) from a sum of the average speed vZ0 and a time integration of aZ0 according to ##EQU26## means for correcting the speed pZIMU (t) in the desired flight direction by adding the correction term pZFIT (t) thereto to obtain a corrected flight speed pZKORR (t) according to
space="preserve" listing-type="equation">p.sub.ZKORR (t)=p.sub.ZIMU (t)+p.sub.ZFIT (t)and means for compensating the radar mapping according to the values of vXKORR (t), pYKORR (t), and pZKORR (t). - View Dependent Claims (4)
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Current AssigneeDeutsche Telekom AG
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Original AssigneeDeutsche Telekom AG
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InventorsBuckreub, Stefan
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Primary Examiner(s)Teska, Kevin J.
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Assistant Examiner(s)NGUYEN, TAN QUANG
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Application NumberUS08/382,532Time in Patent Office698 DaysField of Search364/453, 364/449, 364/460, 364/456, 364/434, 364/447, 364/454, 364/571.01, 364/571.02, 342/451, 342/195, 342/357, 342/462, 342/25, 342/62, 342/95, 342/113, 342/191, 340/991, 340/992, 340/993, 244/3.2, 244/175US Class Current701/220CPC Class CodesG01C 21/16 by integrating acceleration...G01C 21/1652 with ranging devices, e.g. ...G01S 13/60 wherein the transmitter and...G01S 13/86 Combinations of radar syste...G01S 13/90 using synthetic aperture te...G01S 19/40 Correcting position, veloci...
