SYSTEM AND METHOD FOR CALIBRATING A THREE-AXIS ACCELEROMETER
First Claim
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1. A method of calibrating a three-axis accelerometer, comprising:
- receiving a set of acceleration measurement comprising three (X, Y, Z) orthogonal axes corresponding to a current time epoch;
determining whether the three-axis accelerometer is in a static condition based on the acceleration measurements from the three-axis accelerometer including the measurements from previous time epochs and the current time epoch; and
if it is determined that the three-axis accelerometer is in the static condition;
performing at least one of the following three steps;
determining a pitch angle of the three-axis accelerometer and if the pitch angle is less than a predetermined pitch angle threshold value then calculating a Z-axis bias value as a function of the set of acceleration measurements;
calculating a Z-axis bias drift value, as a function of a plurality of sets of acceleration measurements taken while the accelerometer remains in the static condition, wherein the plurality of sets of acceleration measurements are received corresponding to the current time epoch and subsequent time epochs; and
storing the set of acceleration measurements in a database and calculating error source values for at least one of the X, Y, Z axes as a function of a plurality of sets of acceleration measurements that are stored in the database for the time epochs during which the three-axis accelerometer is in the static condition.
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Abstract
An integrated calibration system and process for a three-axis (X, Y, Z) accelerometer estimates Z-axis bias, Z-axis bias drift and determines X, Y, and Z-axes error sources based on measurements taken when the accelerometer is static, i.e., sensing only the earth'"'"'s gravitational acceleration. Optimal on-the-fly error estimates for the three-axis accelerometer are obtained so that the measurements provided by the three-axis accelerometer remain error-free.
39 Citations
33 Claims
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1. A method of calibrating a three-axis accelerometer, comprising:
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receiving a set of acceleration measurement comprising three (X, Y, Z) orthogonal axes corresponding to a current time epoch; determining whether the three-axis accelerometer is in a static condition based on the acceleration measurements from the three-axis accelerometer including the measurements from previous time epochs and the current time epoch; and if it is determined that the three-axis accelerometer is in the static condition; performing at least one of the following three steps; determining a pitch angle of the three-axis accelerometer and if the pitch angle is less than a predetermined pitch angle threshold value then calculating a Z-axis bias value as a function of the set of acceleration measurements; calculating a Z-axis bias drift value, as a function of a plurality of sets of acceleration measurements taken while the accelerometer remains in the static condition, wherein the plurality of sets of acceleration measurements are received corresponding to the current time epoch and subsequent time epochs; and storing the set of acceleration measurements in a database and calculating error source values for at least one of the X, Y, Z axes as a function of a plurality of sets of acceleration measurements that are stored in the database for the time epochs during which the three-axis accelerometer is in the static condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for calibrating a three-axis accelerometer, comprising:
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a calibration component operative to; receive a set of acceleration measurement comprising three (X, Y, Z) orthogonal axes corresponding to a current time epoch,; and determine whether the three-axis accelerometer is in a static condition based on the acceleration measurements from the three-axis accelerometer including the measurements from previous time epochs and the current time epoch and if the three-axis accelerometer is determined to be in the static condition; perform at least one of the following three steps; determine a pitch angle of the three-axis accelerometer and if the pitch angle is less than a predetermined pitch angle threshold value then calculate a Z-axis bias value as a function of the set of acceleration measurements; calculate a Z-axis bias drift value, as a function of a plurality of sets of acceleration measurements taken while the accelerometer remains in the static condition, wherein the plurality of sets of acceleration measurements are received corresponding to the current time epoch and subsequent time epochs; and store of the set of acceleration measurements in a database and calculate error source values for at least one of the X, Y, Z axes as a function of a plurality of sets of acceleration measurements that are stored in the database at the time epochs during which the three-axis accelerometer is in the static condition. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A computer software product comprising a computer-readable medium in which computer program instructions are stored, which instructions, when read by a computer, cause the computer to perform a method of calibrating a three-axis accelerometer, comprising:
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receiving a set of acceleration measurement comprising three (X, Y, Z) orthogonal axes corresponding to a current time epoch; determining whether the three-axis accelerometer is in a static condition based on the acceleration measurements from the three-axis accelerometer including the measurements from previous time epochs and the current time epoch; and if it is determined that the three-axis accelerometer is in the static condition; performing at least one of the following three steps; determining a pitch angle of the three-axis accelerometer while in the static condition and if the pitch angle is less than a predetermined pitch angle threshold value then calculating a Z-axis bias value as a function of the set of acceleration measurements; calculating a Z-axis bias drift value, as a function of a plurality of sets of acceleration measurements taken while the accelerometer remains in the static condition, wherein the plurality of sets of acceleration measurements are received corresponding to the current time epoch and subsequent time epochs; and storing a plurality of sets of acceleration measurements in a database and calculating error source values for at least one of the X, Y, Z axes as a function of a plurality of sets of acceleration measurements that are stored in the database for the time epochs during which the three-axis accelerometer is in the static condition. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification