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Motion detection

This feature is supported by all Abeeway trackers.

Overview​

The tracker embeds a three axes accelerometer, which detects accelerations and triggers motion events. It is configurable with three parameters:

  • motion_sensitivity: Allow a fine tuning of the acceleration intensity to trigger a motion event.
  • motion_debounce: Minimum duration of a movement to be detected (applicable if motion_sensitivity parameter is set to a value between 1 and 99).
  • motion_duration: Define the delay needed without any motion detection to generate a motion end event.

The accelerometer is always active except in OFF mode.

Motion sensitivity​

The accelerometer sensitivity can be fine-tuned by configuration via the parameter motion_sensitivity. Prior to this version, this parameter expressed the accelerometer sensitivity in percentage. From the AT2 v2.3, this parameter accepts different value ranges selecting different modes:

  • 1-30: high sensitivity/low power
  • 100: Default mode (same behavior as the default value 0 in the previous versions).
  • 101..200: Low sensitivity (sensitivity ranging from 1% to 100% as before).

The new motion_debounce parameter is used to define a motion minimum duration in the high sensitivity/low power mode.

High sensitivity/low power mode​

The configuration parameters used for this mode are:

  • The measurement range is +/- 4g
  • The debounce value is configured via the parameter motion_debounce
  • The detection threshold is configured via the motion_sensitivity parameter,and follows the formula: (motion_sensitivity * 0.063g). A movement will be detected if its intensity is above or equals to the motion_sensitivity value during at least the motion_debounce time. This time is calculated from the following formulas:
    • For an initial movement, the duration is given by the formula: motion_debounce * 160 milliseconds
    • For a continuous motion, the duration is given by the formula: motion_debounce * 80 milliseconds
Note

A motion_sensitivity value between 31 and 99 is capped to 30.

Default mode​

Accelerometer configuration:

  • The measurement range is +/- 2g. All values above or below this range are capped.
  • The debounce value is fixed to 80ms
  • The threshold is fixed to 1.126g.
  • The accelerometer is in low power mode/low sensitivity.

Default configuration is obtained when Motion Sensitivity parameter is set to 100.

Low sensitivity mode​

The configuration used for this mode is:

  • The measurement range is +/- 4g
  • The debounce value is fixed to 80ms
  • The threshold is configured via the motion_sensitivity parameter. The value in mg is 1080+29.2*(200-motion_sensitivity)
Note

The following picture shows the conversion between mg (milli Gravity unit) and percentage (low sensitivity mode):

Motion duration​

The end of a motion is detected by the absence of movement during a delay configured via the parameter motion_duration.

This parameter is expressed in seconds and ranges from [60 .. 3600]. The factory default value is 120 seconds.

Device orientation​

The acceleration values from the three axes are available within the motion end event messages or by sending a specific downlink (Refer to Request device configuration for more details). This allows the application to determine the tracker orientation.

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