Method and apparatus to detect platform stationary status using three-axis accelerometer outputs
First Claim
1. A method to detect a platform stationary status for a navigation system, comprising the following steps of:
- measuring amplitudes of raw outputs of three-axis accelerometer mounted on a platform at a predetermined sample rate;
computing latest mean value of outputs of the three-axis accelerometer for the latest samples within a predetermined time length;
subtracting the latest mean value of the three-axis accelerometer outputs with a fixed time window from the raw three-axis accelerometer outputs; and
determining a stationary state of the platform when a difference between the latest mean value and the raw outputs is less than a threshold value.
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Abstract
A system with a capability of detecting the platform stationary status is disclosed. The first aspect is to measure three raw acceleration outputs from an apparatus of the three-axis accelerometer unit. The second aspect is to compute the mean of the latest said acceleration outputs obtained from the three-axis accelerometer unit. The third aspect is to subtract the said mean acceleration outputs from the said raw acceleration outputs obtained from the three axis accelerometer unit to find the differential acceleration components between raw and mean values. The fourth aspect is to compute the amplitude of the differential acceleration, i.e., squared total sum of the three differential acceleration components. The fifth aspect is to count the number of measurements in which the amplitude of the differential acceleration is below a certain threshold, e.g., 0.05 (m/s2) to detect the stationary status if the small amplitude lasts for a certain time length, e.g., 1 second.
34 Citations
13 Claims
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1. A method to detect a platform stationary status for a navigation system, comprising the following steps of:
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measuring amplitudes of raw outputs of three-axis accelerometer mounted on a platform at a predetermined sample rate; computing latest mean value of outputs of the three-axis accelerometer for the latest samples within a predetermined time length; subtracting the latest mean value of the three-axis accelerometer outputs with a fixed time window from the raw three-axis accelerometer outputs; and determining a stationary state of the platform when a difference between the latest mean value and the raw outputs is less than a threshold value. - View Dependent Claims (2, 3, 4)
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5. An apparatus for detecting a platform stationary status for a navigation system, comprising:
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means for measuring amplitudes of raw outputs of three-axis accelerometer mounted on a platform at a predetermined sample rate; means for computing latest mean value of outputs of the three-axis accelerometer for the latest samples within a predetermined time length; means for subtracting the latest mean value of the three-axis accelerometer outputs with a fixed time window from the raw three-axis accelerometer outputs; and means for determining a stationary state of the platform when a difference between the latest mean value and the raw outputs is less than a threshold value. - View Dependent Claims (6, 7, 8)
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9. An integrated INS/GPS navigation system, comprising:
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an INS having a three-axis accelerometer and a stationary status detection unit that receives outputs of the three-axis accelerometer; a GPS receiver which receives satellite signals from a plurality of satellites to produce GPS measurements indicating an absolute position and velocity of the ground vehicle; and a Kalman filter which combines outputs of the INS and the GPS receiver and performs a Kalman filter processing; and wherein the stationary status detection unit determines a stationary status of a platform based on the outputs of the three-axis accelerometer. - View Dependent Claims (10, 11, 12, 13)
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Specification