SENSOR SYSTEM

• US 20080046214A1
• Filed: 04/13/2007
• Published: 02/21/2008
• Est. Priority Date: 04/13/2006
• Status: Active Grant

• Current Assignee: Tiax, LLC
• Original Assignee: Tiax, LLC
• Inventors: Fowler, John Thomas
• Granted Patent: US 7,555,398 B2
• Time in Patent Office: Days
• US Class Current: 702/150
• CPC Class Codes: G01C 17/00 Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes using gyroscopic effect G01C19/00
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A sensor system includes a first measurement subsystem including a driver and a measurement component. The measurement component includes a set of sensors for generating complimentary signals representing each of one or more characteristics. The complimentary signals representing a characteristic include related error components. The driver is configured to accept the complimentary signals for a characteristic and to determine a measurement value for the characteristic by combining the complimentary signals to reduce effects of the error components in the complimentary signals.

Claims

1. A sensor system comprising:

a first measurement subsystem including a driver and a measurement component, the measurement component including a plurality of sensors for generating complimentary signals representing each of one or more characteristics, the complimentary signals representing a characteristic including related error components;

wherein the driver is configured to accept the complimentary signals for a characteristic and to determine a measurement value for the characteristic by combining the complimentary signals to reduce effects of the error components in the complimentary signals.

2. The system of claim 1 wherein the sensor system comprises an orientation computation module for using the measurement value in computing an orientation.

3. The system of claim 1 wherein the plurality of sensors comprises two accelerometers substantially aligned along a common axis and fixed in opposite orientations, each of the two accelerometers being configured to generate a different one of the complimentary signals.

4. The system of claim 3 wherein the plurality of sensors comprises two accelerometers substantially aligned along each of three different axes and fixed in opposite orientations along the axes, each of the two accelerometers for an axis being configured to generate a different one of the complimentary signals.

5. The system of claim 1 further comprising:

a second measurement subsystem comprising a driver and a measurement component, the measurement component, being configurable for generating for generating one of a plurality of complimentary signals in each of a corresponding plurality of configurations.

6. The system of claim 5 wherein the measurement component of the second measurement subsystem comprises a magnetometer configurable to be coupled to the driver in two opposite polarities, each of the two polarities for generating a different one of the complimentary signals.

7. The system of claim 6 wherein the magnetometer includes a two-terminal fluxgate coil, and a switching circuit that includes two configurations for coupling terminals of the coil to the driver.

8. The system of claim 6 wherein the second measurement subsystem is calibrated in absence of substantial interference and is configured to estimate a degree of error in measurement values provided by the subsystem in the presence of an interference.

9. The system of claim 8 wherein the interference comprises an iron interference.

10. The system of claim 8 wherein the degree of error comprises a quantity characterizing an RMS error in heading.

11. The system of claim 1 wherein the one or more characteristics include three substantially orthogonal components of orientation, and the measurement component includes a sensor configuration for generating complimentary signals for each of the orientation components.

12. The system of claim 1 wherein the first measurement subsystem is configured to measure orientation, and the sensor system further includes a second measurement subsystem for measuring magnetic characteristics.

13. The system of claim 12 further comprising an orientation computation module for using measurement values for orientation from the first measurement subsystem and measurement values from the second measurement subsystem for determining an orientation of the sensor.

14. The system of claim 1 wherein a sensor configuration for generating complimentary signals representing each of one or more characteristics represents a substantially symmetric transfer function between the characteristic and the signal.

15. A method for sensing orientation comprising:

generating complimentary signals each from a corresponding different measurement component, the complimentary signals representing each of one or more characteristics, the complimentary signals including related error components; and

determining a measurement value for each of the characteristics by combining the complimentary signals to reduce effects of the error components in the complimentary signals.

16. The method of claim 15 further comprising computing an orientation using the determined measurement value.

17. The method of claim 15 wherein generating the complimentary signals includes generating signals from each of two accelerometers substantially aligned along a common axis and fixed in opposite orientations.

18. The method of claim 17 wherein generating the complimentary signals includes generating signals from each of two accelerometers substantially aligned along each of three different axes and fixed in opposite orientations along the axes.

19. The method of claim 15 further comprising generating complimentary signals from a configurable measurement component, including generating one of a plurality of complimentary signals in each of a corresponding plurality of configurations of the measurement component.

20. The method of claim 19 wherein generating the complimentary signals includes generating signals from a magnetometer configurable to generating a different one of the complimentary signals in each of two polarities of the magnetometer.

21. The method of claim 20 further comprising calibrating the magnetometer in absence of substantial interference and estimating a degree of error in measurement values provided by the magnetometer in the presence of an interference.

22. The method of claim 21 wherein the interference comprises an iron interference.

23. The method of claim 21 wherein the degree of error comprises a quantity characterizing an RMS error in heading.

24. The method of claim 15 wherein generating the complimentary signals includes generating complimentary signals for each of three substantially orthogonal components of magnetic characteristics and three substantially orthogonal components of orientation.

25. The method of claim 15 wherein the system is configured to measure orientation, and to measure magnetic characteristics, and to compute an orientation of using measurement values for the orientation and from the magnetic characteristics.

26. The method of claim 15 wherein generating complimentary signals representing each of one or more characteristics includes generating signals with a substantially symmetric transfer function between the characteristic and the signal.