HM Command — Harsh Maneuver Detector

Driving event detection with 8 independent instances and 8 algorithms: acceleration and braking by GPS; turns, strong maneuver and crashes by accelerometer.

What is it for?

Description

The HM module detects driving events using 8 independent instances (HM00-HM07) where each can be configured for any algorithm type (0-7):

• HMxx = Module index (independent instance)
• eventType = Detection algorithm type (0-7)
• Total flexibility: HM03 can use algorithm type 5, HM00 can use type 2, etc. The type is set by eventType, not by the index.

Configuration

Syntax

Full configuration (parameters are positional and trailing ones may be omitted):

SHMxx,eventType,magnitude,min_speed_kmh,hysteresis_percent,time_window_ms,cooldown_s

Short forms (no comma between xx and the letter):

Parameters

Algorithm Types

🌐 GPS-based (Types 0-1)

They measure the GPS speed change from one second to the next. They do not depend on how the device is mounted.

📐 Accelerometer with minimum speed (Types 2-4)

⚡ Crashes (Types 5-7)

They ignore min_speed_kmh: they also detect with the vehicle stopped.

How the Firmware Evaluates

GPS: one sample per second

The speed change is evaluated once per second and must hold for consecutive seconds until time_window_ms is completed; if one second falls short of the threshold, the count restarts. With a window of T ms, T/1000 + 1 consecutive seconds are needed:

Accelerometer

The device reads the accelerometer every 20 ms and averages 4 readings (about 80 ms); HM checks that average every 100 ms. time_window_ms requires the threshold to hold on every check within that period, and with 0 a single one is enough. magnitude is in mg (1000 mg = 1 g).

Hysteresis

hysteresis_percent is added to the threshold: effective threshold = magnitude × (1 + hysteresis_percent / 100). There is no deactivation threshold, so more hysteresis makes it harder to fire. Example: 330 mg with 10 % fires from 363 mg.

Cooldown

After an event, the same instance does not detect again until cooldown_s seconds have passed.

Device Orientation

Before deploying to a fleet, test it on one vehicle: make a clear left turn and check which event arrives, then brake firmly on a straight road and check that no turn fires. Side crashes (type 5) and strong maneuver (type 4) use the axis magnitude, so they depend less on orientation.

Presets by Vehicle Class

These are the same presets offered by the configurator under Modules → Maneuvers → Presets. The three classes use the same slot map, so the rules work for any of them. They are starting values: tune them with the fleet’s real events.

🚗 Car / Light

>SHM00E,0,7,5,0,1000,5<     // Harsh acceleration: +7 km/h per second, 2 consecutive s
>SHM01E,1,9,10,0,1000,5<    // Harsh braking: −9 km/h per second, 2 consecutive s
>SHM02E,2,330,15,10,2000,3< // Harsh left turn: 0.36 g sustained 2 s
>SHM03E,3,330,15,10,2000,3< // Harsh right turn: 0.36 g sustained 2 s
>SHM04E,5,2000,0,5,0,30<    // Side crash: 2.1 g, no delay
>SHM05E,6,2000,0,5,0,30<    // Frontal crash: 2.1 g, no delay
>SHM06E,7,2000,0,5,0,30<    // Rear crash: 2.1 g, no delay
>SHM07E,4,330,20,10,2000,5< // Strong maneuver: 0.36 g horizontal sustained 2 s

🚛 Van / Fleet

>SHM00E,0,6,5,0,1000,5<     // Harsh acceleration: +6 km/h per second, 2 consecutive s
>SHM01E,1,8,10,0,1000,5<    // Harsh braking: −8 km/h per second, 2 consecutive s
>SHM02E,2,280,15,0,2000,3<  // Harsh left turn: 0.28 g sustained 2 s
>SHM03E,3,280,15,0,2000,3<  // Harsh right turn: 0.28 g sustained 2 s
>SHM04E,5,2000,0,5,0,30<    // Side crash: 2.1 g, no delay
>SHM05E,6,2000,0,5,0,30<    // Frontal crash: 2.1 g, no delay
>SHM06E,7,2000,0,5,0,30<    // Rear crash: 2.1 g, no delay
>SHM07E,4,300,20,0,2000,5<  // Strong maneuver: 0.30 g horizontal sustained 2 s

⛽ Heavy / Hazmat

>SHM00E,0,5,5,0,1000,5<     // Harsh acceleration: +5 km/h per second, 2 consecutive s
>SHM01E,1,6,10,0,1000,5<    // Harsh braking: −6 km/h per second, 2 consecutive s
>SHM02E,2,220,15,0,2000,5<  // Harsh left turn: 0.22 g sustained 2 s
>SHM03E,3,220,15,0,2000,5<  // Harsh right turn: 0.22 g sustained 2 s
>SHM04E,5,1500,0,5,0,30<    // Side crash: 1.6 g, no delay
>SHM05E,6,1500,0,5,0,30<    // Frontal crash: 1.6 g, no delay
>SHM06E,7,1500,0,5,0,30<    // Rear crash: 1.6 g, no delay
>SHM07E,4,250,20,0,2000,5<  // Strong maneuver: 0.25 g horizontal sustained 2 s

Full Example: Event and Black Box

Each maneuver fires a rule that generates its event (UC0 report) and the black box with the seconds before and after, all to the log so nothing is lost without coverage.

>SCXBB,U0,1,10,20<                                  // Black box: UC0 every 1 s, 10 samples after and 20 before
>SRL70E;TRG=HM00+;ACC={GBBFFH;@LOG}{GU070H;@LOG}<  // Event 70: harsh acceleration
>SRL71E;TRG=HM01+;ACC={GBBFFH;@LOG}{GU071H;@LOG}<  // Event 71: harsh braking
>SRL72E;TRG=HM02+;ACC={GBBFFH;@LOG}{GU072H;@LOG}<  // Event 72: harsh left turn
>SRL73E;TRG=HM03+;ACC={GBBFFH;@LOG}{GU073H;@LOG}<  // Event 73: harsh right turn
>SRL74E;TRG=HM04+;ACC={GBBFFH;@LOG}{GU074H;@LOG}<  // Event 74: side crash
>SRL75E;TRG=HM05+;ACC={GBBFFH;@LOG}{GU075H;@LOG}<  // Event 75: frontal crash
>SRL76E;TRG=HM06+;ACC={GBBFFH;@LOG}{GU076H;@LOG}<  // Event 76: rear crash
>SRL77E;TRG=HM07+;ACC={GBBFFH;@LOG}{GU077H;@LOG}<  // Event 77: strong maneuver

To add the maneuvers to the trip score, add {STPGCI,n} to each rule: acceleration → GC2, braking → GC3, turns → GC4 (see GC Counters).

Validations

Limits by Parameter

Recommendations

For Crash Detection

• Types 5, 6 and 7 with magnitude between 1500 and 2000 mg
• time_window_ms at 0: a crash lasts about 100 ms and a longer window lets it through
• Long cooldown_s (30 s)

For Driver Evaluation

• Acceleration and braking by GPS (types 0-1) with a 1000 ms window and 0 hysteresis
• Turns and strong maneuver (types 2-4) with a 2000 ms window to filter potholes
• Moderate cooldown_s (3-5 s)
• Combine with the TRIP module counters for the trip score

Before Deploying to a Fleet

• Run the orientation test on at least one vehicle
• Review the number of events in the first week and tune magnitude per vehicle class

Associated Signals

Compatibility

See Also

• Axis Calibration — Accelerometer calibration
• AC Command — Accelerometer reading
• CXAC Command — Accelerometer configuration
• MVT Command — Movement detection
• Black Box (CXBB) — Reports before and after an event
• GC Counters — Per-trip driving score