Satellite signal receiver with integrity control and exclusion of defective axes

• US 6,191,729 B1
• Filed: 12/07/1998
• Issued: 02/20/2001
• Est. Priority Date: 06/07/1996
• Status: Expired due to Fees

• Current Assignee: Sextant Avionique
• Original Assignee: Sextant Avionique
• Inventors: Arethens, Jean-Pierre
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Mull, Fred H.
• Application Number:
  US09/147,359
• Time in Patent Office: 806 Days
• Field of Search: 342/357.02, 342/357.06
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

A satellite positioning receiver with integrity check and exclusion of defective axes. In order to improve the reliability of the measurements which are divergent with respect to the measurements provided by the other satellites in the constellation which is used at a given time. The invention proposes a solution for more rapidly recalculating the position by eliminating the data from a defective satellite: the means for calculating the position vector X on the basis of n satellites include an iteration process with n steps, the j^th step involving the j^th satellite; a position X′ is recalculated using only n−1 satellites on the basis of the n steps already calculated, by adding an (n+1)^th iteration step, using the measurements from the defective satellite of rank m, this last step being slightly different from the previous ones and the difference being such that the calculation result after this (n+1)^th step is identical to that which an iteration with n−1 steps excluding the divergent satellite of rank m would give.

Claims

1. Satellite positioning receiver, comprising measurement means which simultaneously use n satellites of rank j=1 to n and deliver an n-dimensional measurement vector Z representing the measurements along the n director axes joining the receiver to the n satellites, means for calculating a four-dimensional state vector X on the basis of the measurement vector Z, means for determining the degree of divergence between the n measurements, means for identifying a satellite of rank m which is the most probable cause of excessive divergence, and means for determining a new state vector X′

on the basis of a vector Z′

of n−

1 measurements excluding the measurement coming from the divergent satellite of rank m, characterized in that the means for calculating the vector X include means for performing an iteration process with n steps, the j^th step involving the j^th satellite, and in that the means for determining the vector X′

include means for performing an (n+1)^th iteration step, using the measurements from the divergent satellite of rank m, this last step being different from the previous ones and the difference being such that the calculation result after this (n+1)^th step is identical to that which an iteration with n−

1 steps excluding the divergent satellite of rank m would give.

2. Receiver according to claim 1, characterized in that, if:

Z_j denotes the component of rank j of the measurement vector

X_j denotes the estimate of the measurement vector at step j of the iteration,

P_j denotes a matrix of coefficients at step j,

K_j denotes a 4×

1 gain vector at step j,

s_j denotes the component of estimated noise for the measurement on the axis j,

H denotes the n×

4 matrix of the director cosines of the n satellites, (H)<sup><

j></sup>

denotes the j^th row of this matrix, and (H)<sup><

j>

T</sup> denotes the transpose of this j^th row,

the iteration formula is as follows;

K_j=P<sub>j−

1</sub>.(H)<sup><

j>

T</sup>.[(s_j²)+(H)<sup><

j></sup>

.P<sub>j−

1</sub>.(H)<sup><

j>

T</sup>]<sup>−

1</sup>

P_j=P<sub>j−

1</sub>−

K_j.(H)<sup><

j></sup>

.P<sub>j−

1</sub>

X_j=X<sub>j−

1</sub>+K_j.[Z_j−

(H)<sup><

j></sup>

.X<sub>j−

1</sub>]

and the (n+1)^th step of the iteration is obtained by calculating, on the one hand, the gain vector by the formula;

K_n+1=P_n.(H)<sup><

m>

T</sup>.[−

s_m²+H<sup><

m></sup>

.P_n.(H)<sup><

m>

T</sup>]<sup>−

1</sup>,

and, on the other hand, the state vector X′

by the formula;

X′

=X_n+K_n+1.[Z_m−

(H)<sup><

m></sup>

.X_n].

3. Receiver according to claim 2, characterized in that the means for identifying the satellite of rank m comprise means for calculating a residue DX=(|Z−

H.X|)² for n different configurations with n−

1 satellites each, each configuration corresponding to the exclusion of a determined satellite, means for each time comparing the residue with a threshold, means for identifying a satellite of rank m such that the residue is greater than the threshold for all the configurations in which this satellite is present and less than the threshold for the configuration in which it is absent.

4. Receiver according to claim 3, characterized in that the measurement vector is a position vector.

5. Receiver according to claim 3, characterized in that the measurement vector is a velocity vector.

6. Receiver according to claim 2, characterized in that the measurement vector is a position vector.

7. Receiver according to claim 2, characterized in that the measurement vector is a velocity vector.

8. Receiver according to one of claim 1, characterized in that the measurement vector is a position vector.

9. Receiver according to one of claim 1, characterized in that the measurement vector is a velocity vector.