Template:FMX Ver4 Accelerometer Based Features
Crash Detection
Crash Detection is a feature that automatically detects crash events by continuously monitoring device accelerometer data.
Crash detection is essential for such applications as fleet management, emergency response, and insurance, where detailed data and immediate notification of vehicle incidents are critical.
A crash is detected when acceleration exceeds the threshold value for a predefined duration. The device then generates detailed event records and can send SMS notifications. The system includes crash counting, classification, and filtering to distinguish between genuine crashes and false positives (such as potholes or sudden braking), using GNSS speed analysis to verify the authenticity of detected events.Crash tracing functionality allows the device to capture comprehensive acceleration, GNSS, and I/O data before, during, and after the crash for detailed analysis.
Prerequisites and Important Settings
- All accelerometer-related features depend on proper device mounting, see “Mounting recommendations” [link].
- To send SMS messages and/or make calls, at least one number must be predefined in the “GSM Predefined Numbers” list (“SMS / Call Settings” menu).
- To get higher quality accelerometer data (accurate direction, not only magnitude) it is recommended to enable “Accelerometer auto calibration” in the “System” menu.
- GNSS fix is required to detect fake crashes – without the fix, the device cannot verify speed changes to distinguish genuine crashes from false positives. Also, GNSS fix is required if you use position-related scenarios.
- To properly receive crash trace data, data protocol in the “System Settings” group (“System” menu) must be set to any protocol except “Codec 8” (e.g., Codec 8 Extended or Codec JSON). This helps to optimize sending crash trace data from device to server.
- To correlate a crash event record to its trace (in the management system you use), enable both "Crash Counter" and "Crash Trace".
- To receive the desired I/O element data with the crash event record: in “I/O” menu(s) of the Configurator, under the “Event Only” column, set the element to “Crash”.
Basic Operation
Basic crash detection
- The device continuously reads accelerometer data, and checks if threshold and duration are exceeded.
- When the configured threshold is exceeded for the specified duration, crash event generation is triggered.
- The device classifies and verifies the crash using various criteria (accelerometer calibration state, GNSS speed dynamics).
Crash trace
- If “Trace Full” is enabled, the device gathers additional information about the crash.
- Acceleration magnitude and direction along X, Y, Z axes. Use “Trace filter” parameter to filter acceleration data.
- GNSS data.
- Any I/O element data configured in the “I/O” menus.
- When “Trace Changes” is selected, the device records data only when acceleration changes exceed 50 mG.
- The device processes data (filtering, resampling, timestamping, etc.).
- The crash end is detected.
- Crash event record is generated and sent.
Crash trace with IMU
This is an optional scenario, for devices with an IMU (gyroscope).
- If “Gyroscope crash trace” is enabled, the device gathers additional information about the crash from the IMU (inertial measurement unit).
- An additional record is generated and sent.
Crash counter
- If “Crash counter” is enabled, the device adds AVL ID 317 to both the crash event packet and the related trace data packets.
Parameters
Attention! The following parameters depend on hardware/firmware – you may not see them in software:
- Threshold (16 g) (mG)
- Accel Duration (s)
- Gyroscope crash trace
- IMU trace duration before crash (s)
- IMU trace duration after crash (s)
Where applicable, the table also shows AVL ID values that are directly related to a certain parameter (in parentheses). Always double-check the AVL IDs in the page of your device.
| PARAMETER NAME | PARAMETER ID (RELATED AVL ID) | DESCRIPTION | VALUES |
|---|---|---|---|
| Scenario Settings | 11500 (252) |
Sets the scenario priority level. |
0 = Disable Disable scenario. |
| Duration (ms) | 11401 | Sets the minimal time period for how long the acceleration value should be higher than "Threshold" to trigger the event. | Minimum value = 0 Maximum value = 1000 |
| Threshold (mG) | 11402 | Sets the acceleration threshold value to detect the event. | Minimum value = 100 Maximum value = 6000 |
| Threshold (16 g) (mG) | 11416 | Acceleration threshold (applicable for devices with max 16 g range accelerometer) | Minimum value = 100 Maximum value = 14000 |
| Send SMS to | 7037 | Sets the GSM number of SMS event recipient. | Number selected from “GSM Predefined Numbers” list in menu “SMS / Call Settings”. |
| SMS Text | 8037 | Toggle filtering of accelerometer data in the crash trace. IF enabled, data is passed through EMA filter with 0.4 beta value (can be changed through serial command). | Maximum text length = 160 symbols |
| Trace Filter | 11412 | Toggle filtering of accelerometer data in the crash trace. IF enabled, data is passed through EMA filter with 0.4 beta value (can be changed through serial command). | 0 = Disable 1 = Enable |
| Crash Trace | 11406 (257) |
Enable tracing of crash events to get additional data about the crash. Related parameters: "Trace ODR", "Accel duration", "GNSS duration". | 0 = Disable Generates only an eventual crash record. 1 = Trace Changes Records timestamps, GNSS data and acceleration values ONLY WHEN acceleration values change my 50 mG or more (saves mobile data). |
| Crash Counter | 11415 (317) |
Toggle crash counter. This allows relating the eventual record of a particular crash with its trace packets by adding IO ID 317 to both. “Crash Counter“ and “Crash Trace“ must be enabled. The first crash will send an eventual record with IO ID 317 value 1. Subsequent crashes will add 1 to the value, overflowing at 255 and starting again from 0. | 0 = Disable 1 = Enable |
| Trace ODR (Hz) | 11410 | Sets the output data rate (frequency) of crash event data recording. | Minimum value = 20 Maximum value = 200/400
|
| Accel Duration (s) | 11407 | Sets monitoring duration of linear accelerometer values before and after crash event. This parameter is available for trackers without a gyroscope (IMU). |
Minimum value = 2 Maximum value = 15 |
| GNSS Duration (s) | 11408 | Sets monitoring duration of GNSS data before and after the crash event. | Minimum value = 2 Maximum value = 30 |
| Gyroscope crash trace | 78112 (1422) |
Gyroscope data is collected and processed simultaneously with accelerometer data. If enabled, collected data will be included in accelerometer + gyroscope crash trace, AVL ID 1422. This parameter is available for trackers that have a gyroscope (IMU) |
0 = Disable 1 = Enable |
| IMU trace duration before crash (s) | 78100 | Accelerometer and gyroscope crash trace duration before the crash. Sum of crash trace durations (before and after the crash) cannot be more than 20 seconds.
This parameter is available for trackers that have a gyroscope (IMU) |
Minimum value = 2 Maximum value = 15
|
| IMU trace duration after crash (s) | 78101 | Accelerometer and gyroscope crash trace duration after the crash. Sum of crash trace durations (before and after the crash) cannot be more than 20 seconds. This parameter is available for trackers that have a gyroscope (IMU) |
Minimum value = 2 Maximum value = 11
|
Unplug Detection
Unplug Detection is a feature that notifies when the device is disconnected from its external power source, and again when reconnected. This feature is available for devices that have an internal battery.
Unplug detection is useful in all industries and applications where uninterrupted tracking and notifications about unplugging are essential, e.g. to detect tampering with the device or disconnection attempts by a person.
The Unplug Detection feature monitors the voltage level of the external power source, e.g. of a car battery to which the tracker is connected. If the voltage level drops below a device-specific value for longer than Unplug Delay, an event is generated and notifications can be sent (SMS, calls). The Speed Threshold parameter helps prevent unwanted unplug events in vehicles with smart alternators.
Prerequisites and Important Settings
- This feature is available for devices that have an internal battery.
- All accelerometer-related features depend on proper device mounting, see “Mounting recommendations” [link].
- To send SMS messages and/or make calls, at least one number must be predefined in the “GSM Predefined Numbers” list (“SMS / Call Settings” menu).
Basic Operation
If Unplug detection scenario is enabled, conditions to determine unplug state are checked every second. Initially external power is checked to set device to appropriate unplug state. If external power is less than 5.25 volts, unplugged state is set, on the other hand, if external power is higher than or equal 5.25 volts, plugged state is set.
It is required 1 to 3 seconds to determine the power loss of a device. Consequently, if a device is not being moved any more after few seconds after removing it from the power source, no event will be generated. This can happen, if a device is quickly throwed on the ground after ripping it off.
Simple mode
- Unplug detection constantly monitors external power source voltage.
- Unplug scenario changes states from plugged to unplugged, when external power is less than 5.25 volts and Unplug delay counter reaches its limit.
- Active Unplug event is recorded and SMS notifications are sent.
- Unplug scenario changes states from unplugged to plugged, when external power is higher than or equal 5.25 volts. It resets Unplug delay counter. Plugged event is generated again and SMS notifications are sent accordingly.
Advanced mode
- Unplug detection constantly monitors external power source voltage and accelerometer source for movement changes.
- Unplug scenario changes states from plugged state to unplugged, when unplugged state detected by accelerometer flag is set to true.
- If Speed Threshold is not exceeded, then unplugged event detected by accelerometer, flag is set to true when external power is less than 5.25 volts and measured accelerometer threshold exceeds 0.31 mg.
Once accelerometer threshold exceeds 0.31 mg it is not going to be measured again until external power will be higher or equal to 5.25 volts.
- Active Unplug event is recorded and SMS notifications are sent.
- Unplug scenario changes states from unplugged state to plugged, when external power is higher than or equal 5.25 volts. Plugged event is recorded and SMS notifications are sent.
Unplug Status After Reset
When Unplug Detection Mode is configured as Advanced, Unplug status is saved to flash memory every time when Unplug status is changed. On the first run after soft/hard reset Unplug status is retrieved from flash memory. After configuration change, if previous Unplug Detection Mode was Simple and current alarm sensor ripped off Unplug Detection Mode is Advanced – Unplug status persists from previous mode. This does not work the other way around when configuration changes from Advanced to Simple.
Unplug Detection with Low Power Mode
When Unplug Detection is being used together with Low Power Mode (LPM), depending on configured Sleep mode it will or will not send Unplug Detection record, make a call, or send SMS message.
In Deep Sleep mode record and SMS will be created but they will not be sent, because entering LPM device immediately enters sleeping mode without checking any of the conditions. Since modem is disabled in Deep Sleep, record and SMS will be sent when device will wake up according to LPM conditions. Call will not be made.
In Online Deep Sleep mode record and SMS will be created and sent as well as call will be made since modem is not being turned off. Link will be closed immediately after sending is completed.
Parameters
Where applicable, the table also shows AVL ID values that are directly related to a certain parameter (in parentheses). Always double-check the AVL IDs in the page of your device.
| PARAMETER NAME | PARAMETER ID (RELATED AVL ID) | DESCRIPTION | VALUES |
|---|---|---|---|
| Scenario Settings | 11500 (252) |
Sets the scenario priority level. |
0 = Disable Disable scenario. |
| Eventual Records | 11501 | Toggle appending scenario status to eventual records. | 0 = Disable When enabled, scenario status will be appended only to eventual records. 1 = Enable When disabled, scenario status will be appended in each AVL record. |
| Detection Mode | 11502 | Toggle between simple and advanced unplug detection modes. | 0 = Simple Detects unplugging according to change in external voltage. Event created when external voltage drops below minimum operating voltage of this device. 1 = Advanced Detects unplugging according to changes in external voltage and accelerometer data. Event created when the accelerometer detects movement and external voltage drops below minimum operating voltage of this device. |
| Speed Threshold (km/h) | 11510 | Sets the speed over which unplug events are ignored. | Minimum value = 0. Maximum value = 5000.
|
| Unplug Delay (s) | 11511 | Sets the value by which to delay an Unplug event. Record is generated only if the unplug event is detected and persists for the delay period. If the unplug state keeps changing during the delay period, the unplug event is ignored. | Minimum value = 0. Minimum value = 3600.
|
| Make Call to | 11503 | Select the GSM number for the device to make a call upon event. | Number selected from “GSM Predefined Numbers” list in menu “SMS / Call Settings”. |
| Send SMS to | 7036 | Sets the GSM number of SMS event recipient. | Number selected from “GSM Predefined Numbers” list in menu “SMS / Call Settings". |
| SMS Text | 8036 | Sets the SMS text that will be sent to SMS recipient when the event is triggered. | Maximum text length = 160 symbols. |
Limitations, Edge Cases
Unplug event may not be generated in Advanced detection mode when GNSS signal quality is poor:
- When the GNSS signal quality is poor, speed values may be incorrectly reported, e.g. non-zero values when the vehicle is actually stationary.
- If, during a real unplug event, this incorrect speed value is higher than the configured Speed Threshold, the unplug event will not be registered.
- In such cases, we recommend setting a higher Speed Threshold value.