Platform relative navigation using range measurements

• US 9,645,243 B2
• Filed: 07/13/2012
• Issued: 05/09/2017
• Est. Priority Date: 07/15/2011
• Status: Active Grant

• Current Assignee: Airbus Defence and Space GmbH
• Original Assignee: Astrium GmbH (Airbus SE)
• Inventors: Wendel, Jan
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US14/131,444
• Publication Number:
  US 20140247184A1
• Time in Patent Office: 1,761 Days
• Field of Search: 34235748
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/15 Aircraft landing systems
• CPC Class Codes: G01S 19/53 Determining attitude
• CPC Class Codes: G01S 5/0247 Determining attitude
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A method for platform relative navigation using range measurements involves four or more transmitters of positioning signals located on and/or near a platform of a first object and a second object approaching the platform that includes three or more receivers for receiving the positioning signals. For each received positioning signal, a range measurement between the transmitter of the positioning signal and the receiver of the positioning signal is performed. The relative position and relative attitude of a body frame of the second object is estimated with regard to the first object by processing the range measurements with a state space estimation algorithm implementing a model of the system of the first and second object.

Claims

1. A method for platform relative navigation using range measurements, wherein four or more transmitters of positioning signals are located on or near a platform of a first object and a second object approaching the platform comprises three or more receivers for receiving the positioning signals, wherein the method comprises the acts of:

performing, for each received positioning signal, a range measurement between one of the transmitters of the positioning signal and one of the receivers of the positioning signal; and

directly estimating, by a processor, a relative position and relative attitude of a body frame of the second object with regard to the first object by processing the range measurements with a state space estimation algorithm implementing a model of the system of the first and second object,

wherein the state space estimation algorithm comprises an error state space formulation and performs the following iterative acts of;

assuming a relative position and relative attitude of the second object from the range measurements,

estimating errors in the assumed relative position and relative attitude of the second object, and

correcting the assumed relative position and relative attitude of the second object based on the estimated errors.

2. The method of claim 1, wherein the state space estimation algorithm is a Kalman filter, a Sigma-Point filter or another filter allowing a state space estimation to be performed either in a total state space or an error state space formulation.

3. The method of claim 1, wherein the state space estimation algorithm implements the following system differential equation for estimating errors in the assumed relative position and relative attitude of the second object:

4. The method of claim 1, wherein the system model implemented by the state space estimation algorithm is augmented with relative velocity error states, and the method further comprises the acts of:

performing a Doppler measurement with each received positioning signal; and

estimating relative velocity of the body frame of the second object with regard to the first object by processing the Doppler measurements with the augmented state space estimation algorithm.

5. A method for platform relative navigation using range measurements, wherein four or more transmitters of positioning signals are located on or near a platform of a first object and a second object approaching the platform comprises three or more receivers for receiving the positioning signals, wherein the method comprises the acts of:

performing, for each received positioning signal, a range measurement between one of the transmitters of the positioning signal and one of the receivers of the positioning signal; and

directly estimating, by a processor, a relative position and relative attitude of a body frame of the second object with regard to the first object by processing the range measurements with a state space estimation algorithm implementing a model of the system of the first and second object,

wherein the directly estimating of the relative position and relative attitude of a body frame of the second object with regard to the first object further comprises processing measurements of one or more additional sensors, which include a radar or laser altimeter.

6. The method of claim 5, wherein the state space estimation algorithm comprises an error state space formulation and performs the following iterative acts of:

assuming a relative position and relative attitude of the second object from the range measurements;

estimating errors in the assumed relative position and relative attitude of the second object, and

correcting the assumed relative position and relative attitude of the second object based on the estimated errors.

7. The method of claim 5, wherein an assumed relative attitude of the second object is propagated in a filter prediction step of the state space estimation algorithm using measurements of an inertial measurement unit.

8. The method of claim 5, wherein the state space estimation algorithm models a range measurement {tilde over (ρ

)}_ij , between j-th transmitter and i-th receiver as follows;

{tilde over (ρ

)}_ij=√

{square root over ((r_A,i^s−

r_T,j^s)^T(r_A,i^s−

r_T,j^s))}+n<sub>ρ

ij</sub>

wherein r_T,j^s denotes the position of the j-th transmitter, n<sub>ρ

ij</sub> denotes range measurement noise, and wherein the position of the i-th receiver r_A,i^s is given by

r_A,i^s=r_Ob^s+C_b^sI_i^b,

wherein r_ob^s denotes the position of the origin O_b of the body frame of the second object, I_i^b denotes a lever arm from the origin O_b of the body frame of the second object to the i-th receiver, and C_b^s denotes a direction cosine matrix that transforms from the body frame of the second object to the body frame of the first object, wherein this direction cosine matrix is related to an assumed direction cosine matrix via the relative attitude errors.

9. A non-transitory record carrier storing a computer program, which, when executed by a processor causes the processor to perform the acts of:

performing, for each received positioning signal, a range measurement between a transmitter of a positioning signal and a receiver of the positioning signal; and

directly estimating, by a processor, a relative position and relative attitude of a body frame of a second object with regard to a first object by processing the range measurements with a state space estimation algorithm implementing a model of the system of the first and second object,

wherein four or more transmitters of positioning signals are located on or near a platform of the first object and the second object approaching the platform comprises three or more receivers for receiving the positioning signals,

wherein the state space estimation algorithm comprises an error state space formulation and performs the following iterative acts of;

assuming a relative position and relative attitude of the second object from the range measurements,

estimating errors in the assumed relative position and relative attitude of the second object, and

correcting the assumed relative position and relative attitude of the second object based on the estimated errors.

10. A device for platform relative navigation comprising:

a range measurement unit configured to perform, for a received positioning signal, a range measurement between a transmitter of the positioning signal located on or near a platform of a first object and a receiver of a second object approaching the platform, with which the positioning signal is received; and

a processor configured to estimate a relative position and relative attitude of a body frame of the second object with regard to the first object by processing range measurements between transmitter of positioning signals and receiver of the positioning signals with a state space estimation algorithm implementing a model of the system of the first and second object,

wherein the state space estimation algorithm comprises an error state space formulation and performs the following iterative acts of;

assuming a relative position and relative attitude of the second object from the range measurements,

estimating errors in the assumed relative position and relative attitude of the second object, and

correcting the assumed relative position and relative attitude of the second object based on the estimated errors.

11. The device of claim 10, wherein the device is an unmanned aerial vehicle, which further comprises:

three or more receivers configured to receive positioning signals emitted by four or more transmitters located on or near a platform of another vehicle.

12. A system for platform relative navigation using range measurements comprising:

four or more transmitters of positioning signals, which are located on or near a platform of a first object;

three or more receivers configured to receive the positioning signals, which are located on board of a second object approaching the platform, and

a device comprising

a range measurement unit configured to perform, for a received positioning signal, a range measurement between one of the transmitters of the positioning signal located on or near a platform of the first object and one of the receivers of the second object approaching the platform, with which the positioning signal is received; and

a processor configured to estimate a relative position and relative attitude of a body frame of the second object with regard to the first object by processing range measurements between transmitter of positioning signals and receiver of the positioning signals with a state space estimation algorithm implementing a model of the system of the first and second object,

wherein the transmitters of the positioning signals are transponder configured to reply to an interrogation signal transmitted by one of the receivers with a reply signal, and

wherein the receivers are configured to receive, as the positioning signal, the reply signal from the transponder and to measure a time between transmission of the interrogation signal and the reception of the reply signal, wherein the measured time is processed for a range measurement.