Satellite navigation system using multiple antennas

• US 20040210389A1
• Filed: 04/07/2003
• Published: 10/21/2004
• Est. Priority Date: 04/07/2003
• Status: Active Grant

• Current Assignee: Novariant Incorporated (Kubota Corporation)
• Original Assignee: Integrinautics Corporation (Kubota Corporation)
• Inventors: OʼConnor, Michael L., Cobb, H.Stewart, Montgomery, Paul, Lawrence, Dave, Zimmerman, Kurt R.
• Granted Patent: US 7,027,918 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry

Abstract

A satellite navigation system using multiple antennas for providing the position of multiple fiduciary points on an object even when fewer than four satellites are visible to some or all the antennas. Satellite signals from the multiple antennas are fed into at least one receiver. The receiver or receivers utilize constraint information, which is independent of the satellite signals. These external constraints are used to augment the signals received from the satellites, to obtain the position solution for each antenna. In a preferred embodiment, a common reference clock is used to provide an external constraint. Examples of other external constraints that can be used in the current invention are distance between the antennas, inertial measurement of attitude, rotational or linear position sensors, etc.

Claims

1. A method of obtaining a position solution in a satellite navigation system for an object using a plurality of antennas, the antennas connected to at least one receiver, the antennas having a common reference clock, the method comprising:

a. providing a common reference clock for each antenna;

b. receiving satellite signals at each antenna;

c. the receiver determining the position solution for antennas using external constraints and the signals received at the antennas, wherein the external constraints are independent of received satellite signals,

d. the position solutions being obtained using signals from fewer than four satellites at some or all antennas.

2. The method of claim 1 further comprising the steps of:

a. checking for the consistency of phase between the plurality of antennas; and

b. correcting any inconsistency using the external constraints.

3. The method of claim 1 wherein the step of determining the position further comprises the steps of:

a. calculating an integer cycle ambiguity resolution for input signals to compute position at two or more antennas;

b. predicting signal information from all potentially visible satellites using the calculated antenna positions; and

c. initializing the processor of the receiver for all the potentially visible satellites using the predicted signal information.

4. The method of claim 1 further comprising the step of initializing the plurality of antennas using an already initialized antenna.

5. The method of claim 1 further comprising the step of obtaining correction factors for each of the received satellite signals from a reference station.

6. The method of claim 1 wherein the external constraints are previously surveyed locations of at least two antennas relative to each other.

7. The method of claim 1 wherein the external constraints are obtained by measuring one or more degrees of freedom of the antenna configuration in a multi-element object.

8. The method of claim 1 wherein the external constraint is an inertial measurement of attitude of the object.

9. The method of claim 1 wherein the external constraint is a measurement of relative motion of one antenna with respect to another.

10. A satellite navigation system comprising;

a. a plurality of antennas to receive satellite signals, the antennas being mounted to the object to be tracked and having a common reference clock;

b. at least one receiver connected to the plurality of antennas, the receiver further comprising;

i. means for obtaining external constraints, the external constraints being independent of the satellite signals; and

ii. means for determining the position solutions using the signals received at the antennas and the external constraints.

11. The system of claim 11 wherein the receiver further comprises a phase tracking module for calculating the phase difference for each antenna.

12. The system of claim 11 further comprising:

a. means for checking inconsistency in phases between the plurality of antennas; and

b. means for correcting the inconsistency using the external constraints.

13. The system of claim 11 wherein the external constraints are the previously surveyed locations of some or all the antennas relative to each other.

14. The system of claim 11 wherein the external constraints are obtained by measuring one or more degrees of freedom of the instantaneous configuration in a multi-element object.

15. The system of claim 11 wherein the external constraint is an inertial measurement of attitude of the object.

16. The system of claim 11 further comprising a means for obtaining a correction factor for each of the received satellite signals from a reference station.

17. A method of obtaining a position solution for a plurality of antennas in a satellite navigation system, the antennas connected to at least one receiver, the method comprising:

a. receiving satellite signals at each antennas;

b. providing a common reference clock for each antenna;

c. correcting any inconsistency in satellite signals between the plurality of antennas, using external constraints;

d. calculating an integer cycle ambiguity resolution for the satellite signals to compute the position at two or more antennas using the signals and external constraints;

e. predicting the signal information from all potentially visible satellites using the calculated antenna positions; and

f. initializing the receiver for all potentially visible satellites using the predicted signal information.

18. A satellite navigation system comprising;

a. a plurality of antennas to receive satellite signals, the antennas being mounted to the object to be tracked and;

b. at least one receiver connected to the plurality of antennas, the receiver further comprising;

i. a plurality of phase tracking modules corresponding to the plurality of antennas;

ii. common clock means connected to each phase tracking modules;

iii. means for obtaining external constraints; and

iv. means for determining the position solution for the antennas using the signals received at each antenna and the external constraints.

19. The system of claim 18 wherein the external constraints are the previously surveyed locations of some or all the antennas relative to each other.

20. The system of claim 18 wherein the external constraints are obtained by measuring one or more degrees of freedom of the instantaneous configuration in a multi-element object.

21. The system of claim 18 wherein the external constraint is an inertial measurement of attitude of the object.

22. The system of claim 18 further comprising a means for obtaining a correction factor for each of the received satellite signals from a reference station.