Inertial measurement unit with magnetometer for detecting stationarity

• US 6,496,779 B1
• Filed: 03/30/2000
• Issued: 12/17/2002
• Est. Priority Date: 03/30/2000
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Hwang, Patrick Y.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): MARC-COLEMAN, MARTHE Y
• Application Number:
  US09/539,329
• Time in Patent Office: 992 Days
• Field of Search: 701/220, 244/165, 244/3.1, 244/3.2, 244/79, 244/80, 735/10, 735/14, 734/88, 333/21, 333/23
• US Class Current: 701/220
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A device for measuring a velocity and/or position of a body includes a magnetometer and a measurement unit. The magnetometer is configured to sense a magnetic flux to which the body is exposed. The measurement unit includes a sensor sensing one of an acceleration and a velocity of the body. The measurement unit also includes a processor coupled to the magnetometer and to the measurement unit and configured to determine one on a velocity value and a position value for the body based on the sensed magnetic flux and based or one of the sensed acceleration and the sensed velocity of the body.

Claims

1. A device for measuring a velocity and/or position of a body, comprising:

a magnetometer configured to sense a magnetic flux to which the body is exposed, wherein the magnetic flux being substantially constant is indicative of the body being at rest; and

a measurement unit including

a sensor sensing one of an acceleration and a velocity of the body, and

a processor coupled to the magnetometer and to the sensor and configured to determine one of a velocity value and a position value for the body based on the sensed magnetic flux and based on the one of the sensed acceleration and the sensed velocity of the body;

wherein the sensor is configured to sense as the acceleration a linear acceleration of the body, wherein the processor is configured to one of

calculate as the velocity value a linear velocity value based on the sensed linear acceleration, and wherein the processor is configured to set the linear velocity value at zero if the sensed magnetic flux is substantially constant, and

calculate as the position value a spatial position value based on the sensed linear acceleration, and wherein the processor is configured to maintain the spatial position value at a present value if the sensed magnetic flux is substantially constant.

2. A device for measuring a velocity and/or position of a body, comprising:

a magnetometer configured to sense a magnetic flux to which the body is exposed, wherein the magnetic flux being substantially constant is indicative of the body being at rest; and

a measurement unit including

a sensor sensing one of an acceleration and a velocity of the body, and

a processor coupled to the magnetometer and to the sensor and configured to determine one of a velocity value and a position value for he body based on the sensed magnetic flux and based on the one of the sensed acceleration and the sensed velocity of the body;

wherein the sensor is configured to sense as the velocity a rotational velocity of the body, wherein the processor is configured to one of

determine as the velocity value a rotational velocity value based on the sensed rotational velocity, and wherein the processor is configured to set the rotational velocity value at zero if the sensed magnetic flux is substantially constant, and

calculate as the position value a rotational attitude value based on the sensed rotational velocity, and wherein the processor is configured to maintain the rotational attitude value at a present value if the sensed magnetic flux is substantially constant.

3. A method of reducing degradation of an accuracy of an inertial measurement unit for measuring a velocity and position of a body, the method comprising:

sensing a magnetic flux to which the inertial measurement unit is exposed; and

invoking stationarity conditions if the sensed magnetic flux is substantially constant,

wherein the inertial measurement unit is configured to determine one of a velocity value for the body and a position value for the body, said velocity value comprising one of a linear velocity value and a rotational velocity value, said position value comprising one of a spatial position value and a rotational attitude value, and wherein invoking stationarity conditions comprises one of setting the velocity value at zero and maintaining the position value at a present value.