INERTIAL/DOPPLER-SATELLITE NAVIGATION SYSTEM

• US 3,702,477 A
• Filed: 06/23/1969
• Issued: 11/07/1972
• Est. Priority Date: 06/23/1969
• Status: Expired due to Term

• Current Assignee: Robert G. Brown
• Original Assignee: Robert G. Brown
• Inventors: Brown, Robert G.
• Primary Examiner(s): Farley, Richard A.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US04/835,819
• Time in Patent Office: 1,233 Days
• Field of Search: 235/150.25,150.27 343/112.1,1ST
• US Class Current: 342/451
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence

Abstract

Terrestrial navigation apparatus for a vehicle includes a system of inertial sensors generating signals representative of the position and velocity of the vehicle, a data processor, and a receiver for receiving data from a doppler satellite system including a signal of known frequency as well as signals representative of the satellite'"'"''"'"'s position. The difference between the doppler frequency shift computed from the information received from the satellite and the doppler frequency shift computed by the inertial system is modeled as an observable in a Kalman filter programmed into the data processor to generate a set of error signals representative of estimates of the errors in the position and velocity signals generated by the inertial sensors. The error estimate signals are then used to correct the errors in the inertial sensors. In one disclosed embodiment, the external, observed parameter is a discrete frequency; whereas in an alternative system, it is a frequency count.

Claims

1. Terrestrial navigation apparatus for a vehicle comprising means including inertial means for generating signals representative of the position and velocity of the vehicle, data processing means, a receiver for receiving data from a dopplersatellite system transmitting a reference signal as well as signals from which the satellite'"'"''"'"'s position and velocity may be computed, difference means for generating a signal representative of the difference between the actual doppler frequency shift measured from the signals received from the satellite and the predicted doppler frequency shift computed by the inertial system, Kalman filter means in said data processor receiving said difference signal for generating a set of error signals representative of estimates of the errors in the position and velocity signals generated by said inertial sensors.

2. The system of claim 1 further comprising correction means receiving said error estimate signals for correcting said inertial means in response thereto.

3. The system of claim 2 wherein said inertial means includes a plurality of gyroscope means and accelerometer means associated with said gyroscope means, and wherein said Kalman filter means generates a set of error signals representative of estimates of errors in the biases of said gyroscope means and said accelerometer means.

4. The system of claim 3 further comprising means receiving said last-named error signals for correcting said biases.

5. The system of claim 1 wherein said difference signals are discrete frequency difference signals representative of the difference between the actual doppler shift frequency received from said satellite and a doppler frequency computed in said data processing means based on signals received from said inertial means.

6. The system of claim 1 wherein said difference signals are representative of the difference in frequency count between the actual doppler frequency count and a doppler frequency count computed in said data processing means based on signals received from said inertial means.

7. The system of claim 1 wherein said Kalman filter means includes a digital computer programmed to solve Equations (32) through (36) receiving a frequency count signal representative of a difference in received doppler shift frequency and a doppler shift freQuency computed by said data processing means responsive to the output signals of said inertial means.

8. In a method of navigation for a vehicle having means for generating signals representative of position and velocity of the vehicle, the steps comprising receiving from an earth orbiting satellite signals indicative of the position and velocity of said satellite and a reference frequency signal, generating from said received signals a signal representative of an actual doppler shift in said reference frequency signal, generating a signal from said signals representative of position and velocity of said vehicle and said received signals a signal representative of a predicted doppler shift, comparing said actual doppler shift signal and said predicted doppler shift signal to generate a difference signal representative of the difference between said compared signals, and computing from said difference signals error signals representative of error estimates in said vehicle position and velocity signals, said step of computing comprising using discrete-time least-square filter techniques substantially as described.

9. The method of claim 8 further comprising generating from said difference signal signals representative of accelerometer bias errors, gyroscope bias errors and doppler bias errors.

10. The method of claim 8 wherein said difference signal is representative of a frequency count difference between the actual doppler shift of said reference signal received from said satellite and the frequency count computed based on an estimate of the vehicle'"'"''"'"'s position and velocity from said inertial means.