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Template:FMB640 Accelerometer Features settings (view source)
Revision as of 07:49, 11 October 2021
, 07:49, 11 October 2021→Accelerometer Calibration
==Accelerometer Calibration==
==Accelerometer Calibration==
There are two conditions when auto calibration takes place:
Calibration algorithm is used to recalculate accelerometer axes to represent vehicle‘s axes (see Picture below). Vehicles axes are as follows:<br>
1. X is front.<br>
2. Y is left.<br>
3. Z is down.<br>
[[File:Vehicle axis.PNG.png|center|800px|Vehicle Axis]]
Once vehicle‘s axes are calculated, device is considered calibrated.<br>
<br>
Note: moving forward along any axis will generate negative values. This means acceleration will generate -X values, accordingly breaking will generate X values. Same goes for other axes. <br>
Configurable parameters can be found at [[{{{model|FMB1YX}}}_System_settings#Accelerometer_Auto_Calibration|System Settings Accelerometer Auto Calibration]]
Commands that can be used during calibration:<br>
<center>
{| class="wikitable"
|-
!Command!!Response!!Description
|-
|auto_calibrate:set||Yes||Request auto calibration task start
|-
|auto_calibrate:get||Yes||Request calibration info (time, ground vector, side vector)
|-
|auto_calibrate:clear||Yes||Request calibration clear from flash and stop calibration task
|-
|auto_calibrate:status||Yes||Request calibration status and calibration task status
|}
</center>
====Auto calibration before firmware version 03.25.07.Rev.00.====
Accelerometer auto calibration functionality has one purpose - determine how FMB device
is mounted in a vehicle. After the calibration process ''eco driving'' functionality becomes active
and calibration data will be used to determine harsh acceleration, braking and cornering events.<br />
There are two conditions when auto calibration takes place:<br />
*If on device startup no calibration was detected;
*If on device startup no calibration was detected;
*If the device receives an SMS/GPRS message with ''auto_calibrate:set'' text.<br />
*If the device receives an SMS/GPRS message with ''auto_calibrate:set'' text.<br />
After functionality has started FMB device periodically checks current appliance GNSS, ignition and movement source parameters and if the conditions match:
After functionality has started FMB device periodically checks current appliance GNSS,
ignition and movement source parameters and if the conditions match:<br />
*position fix got;
*position fix got;
*first calibration vector was not saved yet;<br />
*first calibration vector was not saved yet;<br />
Then first vector is taken. Saved vector will be considered as ground vector and it will be used at further calibration calculations.
Then first vector is taken. Saved vector will be considered as ground vector and it will be
used at further calibration calculations.<br />
''Note: When FMB device saves first ground vector vehicle must be parked on flat ground''. Crooked vector may have an impact on further calculations.
''Note: When FMB device saves first ground vector vehicle must be parked on flat ground''.
Crooked vector may have an impact on further calculations.<br />
Afterwards first ground vector was taken, device analyses conditions:
Afterwards first ground vector was taken, device analyses conditions:<br />
*position fix got;
*position fix got;
*vehicle speed increase by 7km/h within 1 second.<br />
*vehicle speed increase by 7km/h within 1 second.<br />
For next vector. Second vector will be taken if all conditions match. Immediately after second vector is received, it will be multiplied by first (ground) vector, the result of these vectors is vector multiplication cross product which is the right side of a car. By using same vector multiplication method, device front, left side will be calculated. At this point calibration is successfully ended as indication device sends an SMS/GPRS message with ''Device is calibrated, to recalibrate send:auto_calibrate:set''.
For next vector. Second vector will be taken if all conditions match. Immediately after
second vector is received, it will be multiplied by first (ground) vector, the result of these
''Note: SMS/GPRS message will be sent only if auto calibration functionality was triggered by'' SMS/GPRS message''.''
vectors is vector multiplication cross product which is the right side of a car. By using
same vector multiplication method, device front, left side will be calculated. At this point
For user convenience in case auto calibration functionality fails then notification message will be sent. For exact messages, check algorithm section.
calibration is successfully ended as indication device sends an SMS/GPRS message with
''Device is calibrated, to recalibrate send:auto_calibrate:set''.<br />
''Note: SMS/GPRS message will be sent only if auto calibration functionality was triggered by'' SMS/GPRS message''.''
''Note: SMS/GPRS message will be sent only if auto calibration functionality was triggered by''
SMS/GPRS message''.<br />''
To get current calibration status ''auto_calibrate:get'' SMS/GPRS command must be sent to the device. If device is calibrated it will respond with ''Calibration state: calibrated'' or otherwise ''Calibration state: not calibrated''. Also this command returns saved Ground and Side vectors.
For user convenience in case auto calibration functionality fails then notification message
will be sent. For exact messages, check algorithm section.<br />
After every TRIP START event, device starts shadow calibration. This type of calibration is running in parallel with already saved vectors (this means that vectors does not reset until shadow calibration have both new vectors). After shadow calibration is done, device updates the vector values to the new ones. There are two conditions when shadow calibration does not run at TRIP start event:
''Note: SMS/GPRS message will be sent only if auto calibration functionality was triggered by''
SMS/GPRS message''.<br />''
To get current calibration status ''auto_calibrate:get'' SMS/GPRS command must be sent to
the device. If device is calibrated it will respond with ''Calibration state: calibrated'' or otherwise
''Calibration state: not calibrated''. Also this command returns saved Ground and Side vectors.<br />
After every TRIP START event, device starts shadow calibration. This type of calibration is
running in parallel with already saved vectors (this means that vectors does not reset until
shadow calibration have both new vectors). After shadow calibration is done, device updates the
vector values to the new ones. There are two conditions when shadow calibration does not run
at TRIP start event:<br />
*Normal calibration is still running.
*Normal calibration is still running.
*Shadow calibration is still running from previous TRIP event.<br />
*Shadow calibration is still running from previous TRIP event.<br />
To take ground vector these conditions should be met:
To take ground vector these conditions should be met:<br />
*Ignition is ON
*Ignition is ON
*Vehicle speed = 0km/h<br />
*Vehicle speed = 0km/h<br />
Device will check these conditions every 1sec until they will pass.
Device will check these conditions every 1sec until they will pass.<br />
To take side vector these conditions should be met:<br />
To take side vector these conditions should be met:
*Vehicle speed >= 20km/h
*Vehicle speed >= 20km/h
*Ignition is ON
*Ignition is ON
*Device angle does not change more than 5 degrees in past 1 sec
*Device angle does not change more than 5 degrees in past 1 sec
*Speed need to increase by 7km/h in 1s period.<br />Device will check these conditions every 1 sec until they will pass.
*Speed need to increase by 7km/h in 1s period.<br />
Device will check these conditions every 1 sec until they will pass.<br />
====Auto calibration rework and improvements from firmware version 03.25.07.Rev.00.====
*Exponential moving average (EMI) Filter added.
=====Auto-calibration Improvement=====
Auto calibration task is launched on one of these conditions (assume calibration is enabled in configuration):<br>
1. Every time device turns on, it checks whether it was previously calibrated and has calibration stored in flash. If device has no calibration in flash, auto calibration task is started.<br>
2. Device calibration was previously disabled by configuration and now is enabled.<br>
3. SMS “auto_calibrate:set” is received. Note: SMS response is sent after calibration has been acquired.<br>
This SMS triggers an SMS response to be sent. Response is sent when calibration is acquired. When 1 hour passes without successful calibration, failed SMS response is sent.<br>
4. Calibrated device’s mean axes of set interval differ more than set amount from desired (0,0,1) calibration is considered inaccurate. Calibration is deleted from flash and auto calibration task started.<br>
After auto calibration task has been started, it will go on indefinitely until satisfactory calibration is acquired.<br>
=====Data Required=====
Auto calibration need to fill two buffers to calibrate device:<br>
1. All accelerometer data – buffer which collects all data from accelerometer at 10Hz frequency. To fill this buffer set seconds of data samples are needed. When buffer is full, oldest data is dumped and new data is placed into the buffer.<br>
2. Straight accelerometer data – buffer which collect straight accelerations data from accelerometer at 10Hz frequency. To fill this buffer set seconds of data samples (set times Hz samples) are needed. When buffer is full, oldest data is dumped and new data is placed into the buffer. Algorithm rules to acquire these samples:<br>
2.1. GPS fix is present.<br>
2.2. Ignition is on.<br>
2.3. GPS speed is more than 5 km/h.<br>
2.4. GPS heading is equal to last GPS heading (+/-1 degree) at GPS sample rate 1Hz.<br>
2.5. GPS speed more then 5 km/h from last sample (accelerating).<br>
Once both buffers are full, auto calibration is attempted. If calibrated values pass calibration quality threshold, calculated calibration is written to flash as current calibration – device is calibrated. <br>
Note: If GPS fix is lost or ignition is turned off, buffers’ data is dumped and must be gathered from 0 again.<br>
=====Re-Calibration=====
When calibration is present, device checks for re-calibration every 60s indefinitely. Re-calibration requires fix and ignition to run also re-calibration is turned off when vehicle is stopped for more than 15s until conditions are satisfied again. When calibrated device’s mean axes of set interval(calibrated accelerometer data) differ more than set amount from desired (0,0,1) (perfect vehicle’s axes) calibration is considered inaccurate, or device’s position has changed and re-calibration is needed. Calibration is cleared from flash and auto calibration task is started.<br>
Note: turning device around calibrated Z axis will not trigger re-calibration, after turning device around Z axis manual re-calibration is advised.
After calibration if quality value is less than 0.80, calibration update functionality is run. Calibration update constantly tries calibrating device in background until 0.80 quality is reached. Calibration update functionality does not change calibration if calculated new calibration quality is less than 0.80.
==Excessive Idling==
==Excessive Idling==