Vehicle sensor calibration for determining vehicle dynamics
First Claim
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1. A method of calibrating a tri-axial accelerometer that provides uncalibrated outputs for X, Y and Z Cartesian axes resident in a locator that is installed on a mobile asset, comprising the steps of:
- a) obtaining the uncalibrated X, V, and Z axes accelerometer output data;
b) determining, via a processor, in two phases and in at least one of auto and self calibration modes a coordinate transform T that is appropriate for the tri-axial orientation of the accelerometer relative to the frame of reference of the mobile asset, wherein;
the transform T is a Euler transform comprising a yaw correction angle φ
, a roll correction angle θ
, and a pitch correction angle ψ
;
the mobile asset is static on a plumbed surface in a first of said two phases, in which the roll correction angle θ and
the pitch correction angle ψ
are calculated; and
the mobile asset is moving in a second of said two phases, in which the yaw correction angle φ
is calculated;
c) applying said transform T to said uncalibrated X, Y, and Z axes accelerometer output data to obtain calibrated X, Y, and Z axes accelerometer data; and
d) removing from acceleration data, an offset created by gravity when the mobile asset is moving on a sloped terrain, comprising the steps of;
low pass filtering the Z axis acceleration data to obtain â
z;
calculating the terrain pitch;
p=arc cos(â
z/G);
determining the sign (negative or positive) of the slope; and
correcting said calibrated X axis acceleration data by subtracting therefrom G·
sin(ρ
).
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Abstract
An accelerometer sensor equipped device uses GPS and known alignment data to determine the alignment of the accelerometer sub-system when the vehicle is stationary and in motion. The alignment data is determined from known surface information, measured GPS velocity, and measured GPS Heading.
74 Citations
15 Claims
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1. A method of calibrating a tri-axial accelerometer that provides uncalibrated outputs for X, Y and Z Cartesian axes resident in a locator that is installed on a mobile asset, comprising the steps of:
-
a) obtaining the uncalibrated X, V, and Z axes accelerometer output data; b) determining, via a processor, in two phases and in at least one of auto and self calibration modes a coordinate transform T that is appropriate for the tri-axial orientation of the accelerometer relative to the frame of reference of the mobile asset, wherein; the transform T is a Euler transform comprising a yaw correction angle φ
, a roll correction angle θ
, and a pitch correction angle ψ
;the mobile asset is static on a plumbed surface in a first of said two phases, in which the roll correction angle θ and
the pitch correction angle ψ
are calculated; andthe mobile asset is moving in a second of said two phases, in which the yaw correction angle φ
is calculated;c) applying said transform T to said uncalibrated X, Y, and Z axes accelerometer output data to obtain calibrated X, Y, and Z axes accelerometer data; and d) removing from acceleration data, an offset created by gravity when the mobile asset is moving on a sloped terrain, comprising the steps of; low pass filtering the Z axis acceleration data to obtain â
z;calculating the terrain pitch;
p=arc cos(â
z/G);determining the sign (negative or positive) of the slope; and correcting said calibrated X axis acceleration data by subtracting therefrom G·
sin(ρ
). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification