Autonomous velocity estimation and navigation

• US 20050143949A1
• Filed: 08/17/2004
• Published: 06/30/2005
• Est. Priority Date: 08/18/2003
• Status: Active Grant

• Current Assignee: Saab AB
• Original Assignee: Saab AB
• Inventors: Hagstedt, Anders
• Granted Patent: US 7,248,967 B2
• Time in Patent Office: Days
• US Class Current: 702/145
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01P 7/00 Measuring speed by integrating acceleration measuring travelled distance by double integration of acceleration G01C21/16

Abstract

The present invention relates to measurement of a spatial velocity vector (v_x, v_y, v_z), i.a. in order to make determination of a geographical position possible. A proposed spatial velocity meter (200) includes an inertial measurement unit (210), a direction-sensing module (220) and a velocity processor (230). The inertial measurement unit (210) registers acceleration parameters (a) and angular velocity parameters (ω) in three dimensions. The direction-sensing module (220) registers a natural reference signal (R). The velocity processor (230) receives the acceleration parameters (a), the angular velocity parameters (co) and the natural reference signal (R), and based thereon, generates the spatial velocity vector (v_x, v_y, v_z).

Claims

1. A spatial velocity meter comprising:

an inertial measurement unit adapted to register acceleration parameters and angular velocity parameters in three dimensions; and

a velocity processor adapted to receive the acceleration parameters, receive the angular velocity parameters, and based on at least these parameters, generate a velocity vector expressing a velocity in relation to the earth, wherein

the velocity meter comprises a direction-sensing module which is adapted to register a natural reference signal, and

the velocity processor is adapted to receive the natural reference signal and determine the velocity vector on further basis of the natural reference signal.

2. The spatial velocity meter according to claim 1, wherein the direction-sensing module comprises a magnetic measurement unit which is adapted to register a field vector of the terrestrial magnetic field to represent the natural reference signal, and the velocity processor is adapted to receive the field vector and determine the velocity vector on further basis of the field vector.

3. The spatial velocity meter according to claim 1, wherein it is adapted to be mounted in a craft to register the craft'"'"'s spatial velocity, and the velocity processor is adapted to implement an estimation procedure, which in turn is adapted to derive the velocity vector based on a relationship between three dimensional forces and three dimensional angular velocities in respect of an axis being parallel to a longitudinal body axis of the craft.

4. The spatial velocity meter according to claim 1, wherein it comprises a plumb-bob module adapted to receive the acceleration parameters and in response thereto produce a set of initial attitude parameters.

5. The spatial velocity meter according to claim 4, wherein it comprises an attitude updating module adapted to receive the set of initial attitude parameters receive the angular velocity parameters and based thereon produce a set of updated attitude parameters.

6. The spatial velocity meter according to claim 5, wherein characterized in that it comprises an error estimation module adapted to receive the set of updated attitude parameters receive the acceleration parameters receive the angular velocity parameters, and based thereon produce a craft velocity and at least one adjusted attitude angle.

7. The spatial velocity meter according to claim 6, wherein it comprises a course calculation module adapted to receive the natural reference signal, receive the at least one adjusted attitude angle and based thereon produce a course angle.

8. The spatial velocity meter according to claim 7, wherein it comprises a velocity transform module adapted to receive the craft velocity, receive the at least one adjusted attitude angle receive the course angle, and based thereon produce the velocity vector.

9. A navigation arrangement for determining a geographical position of a craft, comprising:

an integrator module adapted to receive an initial position coordinate, receive a velocity vector, and based thereon, generate an updated position coordinate, wherein the navigation arrangement comprises a spatial velocity meter according to claim 1, and the spatial velocity meter being adapted to produce the velocity vector.

10. A method for spatial velocity estimation comprising registering acceleration parameters and angular velocity parameters in three dimensions, the method comprising:

registering a natural reference signal; and

determining a velocity vector on basis of the acceleration parameters, the angular velocity parameters and the natural reference signal.

11. The method according to claim 10, wherein the registration of the natural reference signal involves registering a field vector of the terrestrial magnetic field;

and the determination of the velocity vector being based on the field vector.

12. The method according to claim 10, further comprising producing a set of initial attitude parameters in response to the acceleration parameters.

13. The method according to claim 12, further comprising producing a set of updated attitude parameters on basis of the set of initial attitude parameters and the angular velocity parameters.

14. The method according to claim 13, further comprising producing a craft velocity and at least one adjusted attitude angle on basis of the updated attitude parameters, the acceleration parameters, and the angular velocity parameters.

15. The method according to claim 14, further comprising calculating a course angle on basis of the natural reference signal and the at least one adjusted attitude angle.

16. The method according to claim 15, further comprising producing the velocity vector on further basis of the craft velocity, the at least one adjusted attitude angle, and the course angle.

17. A computer program directly loadable into the internal memory of a computer, comprising software for controlling the steps of claim 10 when said program is run on the computer.

18. A computer readable medium, having a program recorded thereon, where the program is to make a computer control the steps of claim 10.

19. A navigation method comprising:

receiving an initial position coordinate;

registering acceleration parameters and angular velocity parameters in three dimensions;

estimating a spatial velocity in relation to the earth based on at least the acceleration and the angular velocity parameters; and

determining an updated position coordinate based on the initial position coordinate and an integration of the velocity vector comprising estimating the spatial velocity according to claim 10.

20. A computer program directly loadable into the internal memory of a computer, comprising software for controlling the method of the claim 19 when said program is run on the computer.

21. A computer readable medium, having a program recorded thereon, where the program is to make a computer control the method of the claim 19.