English 
inline speedometer calibrator
An In-line speedometer calibration method for a vehicle-mounted accelerometer, comprising: obtaining a detected speed of a vehicle and a longitudinal acceleration detected by the vehicle-mounted accelerometer; differentiating the detected speed of the vehicle to determine the calculated acceleration; and based on the longitudinal acceleration and the calculated acceleration determines an acceleration factor used to calibrate the on-board accelerometer.
The determining the acceleration factor based on the longitudinal acceleration and the calculated acceleration includes: responding to the fact that the vehicle is in a uniform acceleration phase within a preset time and the fluctuation of the longitudinal acceleration detected by the on-board accelerometer is less than a preset threshold, based on the acceleration factor is determined by an average value of the calculated acceleration determined within the preset time and an average value of the longitudinal acceleration within the preset time. Judging whether the detected speed of the vehicle is greater than a preset speed; and judging that the vehicle is in a uniform acceleration stage in response to the detected speed being greater than a preset speed.
Calculating the standard deviation of the longitudinal acceleration detected by the on-board accelerometer within the preset time; and in response to the standard deviation being less than a preset threshold, judging that the fluctuation of the longitudinal acceleration detected by the on-board accelerometer is less than a preset threshold. The acceleration factor is calculated by using the acceleration factor calculation formula, wherein, k is the acceleration factor, is the average value of the calculated acceleration within the preset time, and is the average value of the longitudinal acceleration within the preset time. Filtering the detected velocity and the longitudinal acceleration; and said differentiating the detected velocity of the vehicle to determine the calculated acceleration comprises: differentiating the filtered detected velocity to determine the calculated acceleration; Determining the acceleration factor by the longitudinal acceleration and the calculated acceleration includes: determining the acceleration factor by using the calculated acceleration determined by the filtered detection speed and the filtered longitudinal acceleration. The raw longitudinal acceleration detected by the on-board accelerometer is calibrated for installation errors to determine the longitudinal acceleration. The installation error calibration of the original longitudinal acceleration detected by the vehicle-mounted accelerometer includes: installing the vehicle-mounted accelerometer on the vehicle; collecting the original acceleration value output by the vehicle-mounted accelerometer under static conditions, the The original value of acceleration includes original longitudinal acceleration, original roll acceleration and original pitch acceleration; the acceleration is determined by using the theoretical value of three-axis acceleration of the vehicle in the vehicle coordinate system under static conditions and the original value of acceleration output by the vehicle accelerometer an installation deflection angle of the accelerometer relative to the vehicle; and using the installation deflection angle to calibrate the raw longitudinal acceleration of the on-board accelerometer to determine the longitudinal acceleration.
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