Method for determining and correcting incorrect orientations and offsets of the sensors of an inertial measurement unit in a land vehicle
View Patent ↗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.
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:
installing the sensor cluster in a vehicle;
determining the position of a sensor cluster with respect to the longitudinal direction of a vehicle;
wherein the distance between the sensor cluster and a rear axle of the vehicle is determined by averaging the longitudinal acceleration of the vehicle, which is not measured on the rear axle;
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, wherein
at least values determined by other sensors arranged in the vehicle are selected as known values 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 the other sensors arranged in the vehicle are selected from the group consisting of wheel speed sensor and steering angle sensor.
5. A method for correcting measurement values of sensors of a sensor cluster in a vehicle, comprising:
installing the sensor cluster in a vehicle;
determining the position of a sensor cluster with respect to the longitudinal direction of a vehicle;
wherein the distance between the sensor cluster and a rear axle of the vehicle is determined by averaging the longitudinal acceleration of the vehicle, which is not measured on the rear axle;
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, wherein
at least values determined by other sensors arranged in the vehicle are selected as known values 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.
6. The method according to claim 5 , 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.
7. 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.
8. The method according to claim 5 , wherein
values determined by other sensors are selected as known values in the fixed vehicle Cartesian coordinate system.
9. The method according to claim 5 , wherein the other sensors arranged in the vehicle are selected from the group consisting of wheel speed sensor and steering angle sensor.
10. A method for determining the position of an inertial sensor cluster in a vehicle, the method comprising the steps of:
installing the inertial sensor cluster in a vehicle;
receiving sensor data from the inertial sensor cluster during movement of the vehicle and determining the position of the inertial sensor cluster from the received sensor data with respect to the longitudinal direction of the vehicle,
wherein for determining the position of the inertial sensor cluster, the distance between the inertial sensor cluster and a rear axle of the vehicle is determined by averaging the longitudinal acceleration of the vehicle, which is not measured on the rear axle.
11. A non-transitory 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 a network, performs the steps of:
determining the position of an inertial sensor cluster with respect to the longitudinal direction of a vehicle;
wherein the distance between the inertial sensor cluster and a rear axle of the vehicle is determined by averaging the longitudinal acceleration of the vehicle, which is not measured on the rear axle;
predetermining desired installation directions of sensors of the sensor cluster within a vehicle in relation to coordinate axes of a fixed vehicle Cartesian coordinate system;
determining actual installation directions of the sensors within the vehicle by comparing values measured by the sensors in different conditions with values known for these different conditions in the fixed vehicle Cartesian coordinate system, wherein
values determined by other sensors arranged in the vehicle are selected as known values in the fixed vehicle Cartesian coordinate system.
12. The non-transitory computer readable medium according to claim 11 , 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.
13. The non-transitory computer readable medium according to claim 11 , wherein mean values during a vehicle trip are selected as known values in the fixed vehicle Cartesian coordinate system.
14. 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:
installing the sensor cluster in a vehicle remote from an unsteered axle;
determining the position of the sensor cluster with respect to the longitudinal direction of the vehicle,
wherein the distance between the sensor cluster and a rear axle of the vehicle is determined by averaging the longitudinal acceleration of the vehicle, which is not measured on the rear axle;
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 within the vehicle, 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, wherein mean values accumulated during a vehicle trip are selected as known values in the fixed vehicle Cartesian coordinate system, and wherein values determined by other sensors arranged in the vehicle are selected as known values in the fixed vehicle Cartesian coordinate system.
15. The method according to claim 14 , wherein the vehicle trip includes starts and ends with a stationary state.