TURN_MAX_G: Turning maximum G force

Description

The maximum turning acceleration (in units of gravities) that the rover can handle while remaining stable.

Values

• Range: 0.1 to 10
• Units: G (Gravities)
• Default: 0.6

Description

This parameter is a safety limit for Rover.

• Function: It tells the navigation controller the maximum lateral acceleration (cornering force) the vehicle can sustain without flipping over or skidding.
• Effect: If a waypoint requires a turn that would exceed this G-force at current speed, the rover will automatically slow down before entering the turn to keep the G-force below this limit.
• Tuning:
  • Low CG / Wide vehicles: Can handle higher values (e.g., 1.0G or more).
  • High CG / Narrow vehicles: Must be set lower (e.g., 0.3G) to prevent rollovers.

Turn radius of vehicle (TURN_RADIUS)

Description

This parameter defines the Physical Minimum Turn Radius of the rover at low speeds. It is a critical constraint for the navigation path planner (L1 controller). The autopilot uses this value to ensure it does not attempt turns sharper than the vehicle is mechanically capable of making, which would result in large crosstrack errors.

The Mathematics

Used to clamp lateral acceleration demand:
$$ a\_{lat\_{max}} = \frac{V^2}{\text{TURN\_RADIUS}} $$
(Simplified relation for limiting path curvature).

The Engineer's View

Defined in Rover/Parameters.cpp.

• Skid Steering: Even though skid steer vehicles can turn in place (Radius = 0), setting a non-zero value here (e.g., 0.5m) helps produce smoother, flowing turns during waypoint missions rather than stopping and pivoting.
• Ackermann Steering: Must be set to the actual mechanical limit (plus a safety margin).

Tuning & Behavior

• Default Value: 0.9 m
• Procedure: Drive the rover in a full lock circle manually, measure the radius, and enter that value here.