Method For Determining and Correcting Incorrect Orientations and Offsets of the Sensors of an Inertial Measurement Unit in a Land Vehicle

• US 20080208501A1
• Filed: 05/11/2006
• Published: 08/28/2008
• Est. Priority Date: 07/15/2005
• Status: Active Grant

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Continental Automotive GmbH (Continental AG)
• Inventors: Mayer, Andreas, Stratesteffen, Martin, Schweiger, Thomas, Fiedler, Jens
• Granted Patent: US 8,065,104 B2
• Time in Patent Office: Days
• 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

An inertial measurement unit (IMU) contains three linear acceleration sensors and three rotational speed sensors. For the sensors there are desired installation directions parallel to the co-ordinate axes of a Cartesian co-ordinate system which is fixed to the vehicle. The actual installation directions of the sensors may differ from the desired installation directions owing to incorrect orientations. By comparing accelerations which are measured by the linear acceleration sensors for different attitudes of the vehicle with acceleration values which are known for these different attitudes in the Cartesian co-ordinate system which is fixed to the vehicle, the actual installation directions of the linear acceleration sensors are determined. By using a co-ordinate transformation it is then possible to convert the measured accelerations into the actual accelerations.

Claims

1. A method for determining incorrect orientations of sensors of a sensor cluster in a vehicle,

wherein the sensor cluster has either three linear acceleration sensors and/or three rotational speed sensors;

the method comprising the steps of;

predetermining desired installation directions of the sensors in relation to coordinate axes of a fixed vehicle Cartesian coordinate system;

determining actual installation directions of the sensors, which can deviate from the desired installation directions due to incorrect orientations,

by comparing values measured by the sensors in different conditions with values known for these different conditions in the fixed vehicle Cartesian coordinate system.

2. The method according to claim 1, wherein

any offset is determined during measurements by the sensors by means of a suitable plurality of measurements by the sensors in different conditions, which result in known values in the fixed vehicle Cartesian coordinate system.

3. The method according to claim 1, wherein

mean values during a vehicle trip are selected as known values in the fixed vehicle Cartesian coordinate system.

4. The method according to claim 1, wherein

values determined by other sensors are selected as known values in the fixed vehicle Cartesian coordinate system.

14. A modulated data signal, which contains instructions for executing a method as claimed in claim 1, which can be executed by a computation unit, a microcontroller, DSP, FPGA or computer or by a plurality of these in a network.

5. A method for correcting measurement values of sensors of a sensor cluster in a vehicle, comprising the steps of:

determining incorrect orientations of the sensors by predetermining desired installation directions of the sensors in relation to coordinate axes of a fixed vehicle Cartesian coordinate system and determining actual installation directions of the sensors by comparing values measured by the sensors in different conditions with values known for these different conditions in the fixed vehicle Cartesian coordinate system; and

wherein with the aid of incorrect orientations determined from values measured by the sensors actual values of the vehicle in relation to a fixed vehicle Cartesian coordinate system are predicted.

11. The method according to claim 5, wherein

any offset is determined during measurement by the sensors by means of a suitable plurality of measurements by the sensors in different conditions, which result in known values in the fixed vehicle Cartesian coordinate system.

12. The method according to claim 5, wherein

mean values during a vehicle trip are selected as known values in the fixed vehicle Cartesian coordinate system.

13. The method according to claim 5, wherein values determined by other sensors are selected as known values in the fixed vehicle Cartesian coordinate system.

6. A method for determining the position of an inertial sensor cluster in a vehicle, the method comprising the steps of:

determining the position in the longitudinal direction of the vehicle,

wherein the distance between the inertial sensor cluster and the rear axle of the vehicle is determined by averaging the longitudinal acceleration of the vehicle, which is not measured on the rear axle.

7. A computer readable medium storing a computer program, which when executed on a computation unit, a microcontroller, DSP, FPGA or computer or on a plurality of these in network, performs the steps of:

predetermining desired installation directions of the sensors in relation to coordinate axes of a fixed vehicle Cartesian coordinate system;

determining actual installation directions of the sensors by comparing values measured by the sensors in different conditions with values known for these different conditions in the fixed vehicle Cartesian coordinate system.

8. The computer readable medium according to claim 7, wherein

any offset is determined during measurements by the sensors by means of a suitable plurality of measurements by the sensors in different conditions, which result in known values in the fixed vehicle Cartesian coordinate system.

9. The computer readable medium according to claim 7, wherein mean values during a vehicle trip are selected as known values in the fixed vehicle Cartesian coordinate system

10. the computer readable medium according to claim 7, wherein values determined by other sensors are selected as known values in the fixed vehicle Cartesian coordinate system.