초록 ▼

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

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.

대표청구항 ▼

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 senso

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 [Figure] (2) 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 nXIMU(t)=nX(t)-nX(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 [Figure] (19) [Figure] (20) 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 nXKORR(t)=nXIMU(t)+nXFIT(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 [Figure] (6) 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 [Figure] (8) 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 pYIMU(t)=p′Y(t) -p′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 [Figure] 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 pYKORR(t)=pYIMU(t)+pYFIT(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 [Figure] (12) 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 [Figure] (14) 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 pZIMU(t)=p′z(t)-p′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 [Figure] (27) [Figure] (28) 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 pZKORR(t)=pZIMU(t)+pZFIT(t)(29) and compensating the radar mapping according to the values of vXKORR(t), pYKORR(t), and pZKORR(t).