Method for improving the measurement values of an inertial measurement system

• US 6,738,721 B1
• Filed: 06/18/2001
• Issued: 05/18/2004
• Est. Priority Date: 12/18/1998
• Status: Expired due to Fees

• Current Assignee: Autoflug Gmbh (Autoflug Gruppe GmbH)
• Original Assignee: Autoflug Gmbh (Autoflug Gruppe GmbH)
• Inventors: Hinsch, Thomas, Drücke, Peter
• Primary Examiner(s): Barlow, Jr., John E
• Assistant Examiner(s): PRETLOW, DEMETRIUS R
• Application Number:
  US09/868,734
• Time in Patent Office: 1,065 Days
• Field of Search: 702/95, 702/96, 702/104, 702/141, 702/142, 73/13.7, 73/13.8, 73/17--
• US Class Current: 702/95
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

Inertial measurement systems for measuring accelerations and angular speeds are currently widely used in vehicles where they serve as sensors for safety devices and navigation systems. The required reliability and precision, however, can be obtained only with extremely accurate sensors and precise finishing. The invention therefore provides for a method according to which an inertial measurement system comprising economical, mass-produced sensors is first gauged overall in a testing device in one calibration operation. During gauging any offset, mounting position and scaling errors are detected as coefficients of coupling matrices of the sensors and converted into compensation values which are then used to improved the accuracy of the sensors'"'"' measurement values when the measurement system is in operation. The above method is suitable for inertial measurement systems in land, air and water craft.

Claims

1. A method for improving the measurement values of an inertial measurement system that includes a computer for coordinate conversion and for each coordinate axis x, y, z, includes a sensor for accelerations and a sensor for angular speeds that are measured in a coordinate system allocated to the orthogonal axes of the measurement system and are converted such that the output values are provided in an inertial system, said method including the steps of:

compensating measurement values of the sensors with correction values obtained in an alignment mode,

wherein in said alignment mode, the measurement system is mounted on a testing device, wherein said testing device has a mounting surface rotatable about at least one coordinate axis, such that orthogonal coordinate axes of the testing device and measurement system are parallel, wherein each coordinate axis of the measurement system is successively oriented in the vertical and in the inverse vertical and in the direction of the axis of rotation of the testing device, wherein for each orientation of said measurement system, the measurement values of said sensors are acquired, and wherein, taking into account a linear equation system for cross couplings of the sensors, the correction values are calculated from the measurement values stored in a memory.

2. A method according to claim 1, wherein when the measurement system is in a state of rest, the measurement values of the angular speed sensors are acquired as angular speed.

3. A method according to claim 2, wherein the measurement system is rotated at a constant angular speed about a coordinate axis that is oriented to the axis of rotation, wherein the measurement values of the angular speed sensors are acquired continuously, and wherein correction values are calculated from the angular speeds and the angular speed offsets as coefficients of a compensation matrix of said angular speeds.

4. A method according to claim 3, wherein for an acceleration sensor that coincides with the vertical, with the gravitational acceleration as a reference, an acceleration offset is calculated from the measurement values of the acceleration sensor in the vertical and in the vertical inverse thereto by finding a mean, and wherein correction values are calculated with the measurement values allocated to the coordinate axes and the acceleration offsets as coefficients of a compensation matrix of the accelerations.

5. A method according to claim 4, wherein the compensation matrices are stored in said memory.

6. A method according to claim 1, wherein the measurement system in a state of rest, is subjected to a temperature cycle, wherein measurement values of angular speed sensors are stored as temperature-dependent angular speed offsets in a ω

-temperature table together with an associated temperature, wherein temperature-dependent measurement values of acceleration sensors are stored in a B-temperature table, and wherein for each acceleration sensor, temperature-dependent acceleration offsets are determined from the stored temperature-dependent measurement values and from the measurement values in the vertical and in the inverse vertical and are stored in a B-offset temperature table.

7. A method according to claim 6, wherein measurement values of angular speed and acceleration sensors are corrected by angular speed and acceleration offsets stored in said tables, as a function of the temperature.

8. A method according to claim 6, wherein compensation of measurement values is performed using compensation matrices stored in the memories.

9. A method according to claim 1, wherein more than a required number of available measurement values are used in a linear regression method for calculating the coefficients of the linear equation system.