Document ID: chunk:federal_register_of_legislation:F2021C00476:body:0:p8
Version: federal_register_of_legislation:F2021C00476
Segment Type: other
Provision Reference: 
Character Range: 22501–25498

is made by automatic means in which vehicle retardation is secondary to vehicle behaviour modification.

         2.22. "Braking signal": logic signal indicating brake activation as specified in paragraph 5.2.22.

         2.23. "Emergency braking signal": logic signal indicating emergency braking as specified in paragraph 5.2.23.

         2.24. "Ackerman steer angle" means the angle whose tangent is the wheelbase divided by the radius of the turn at a very low speed.

         2.25. "Electronic Stability Control System" or "ESC System" means a system that has all of the following attributes:

         2.25.1. That improves vehicle directional stability by at least having the ability to automatically control individually the braking torques of the left and right wheels on each axle [1]/ to induce a correcting yaw moment  based on the evaluation of actual vehicle behaviour in comparison with a determination of vehicle behaviour demanded by the driver;

         2.25.2. That is computer controlled with the computer using a closed-loop algorithm to limit vehicle oversteer and to limit vehicle understeer based on the evaluation of actual vehicle behaviour in comparison with a determination of vehicle behaviour demanded by the driver;

         2.25.3. That has a means to determine directly the value of the vehicle's yaw rate and to estimate its side-slip or side-slip derivative with respect to time;

         2.25.4. That has a means to monitor driver steering inputs; and

         2.25.5. That has an algorithm to determine the need, and a means to modify propulsion torque, as necessary, to assist the driver in maintaining control of the vehicle.

         2.26. "Lateral acceleration" means the component of the acceleration vector of a point in the vehicle perpendicular to the vehicle x axis (longitudinal) and parallel to the road plane.

         2.27. "Oversteer" means a condition in which the vehicle's yaw rate is greater than the yaw rate that would occur at the vehicle's speed as a result of the Ackerman steer angle.

         2.28. "Side-slip or side-slip angle" means the arctangent of the ratio of the lateral velocity to the longitudinal velocity of the centre of gravity of the vehicle.

         2.29. "Understeer" means a condition in which the vehicle's yaw rate is less than the yaw rate that would occur at the vehicle's speed as a result of the Ackerman steer angle.

         2.30. "Yaw rate" means the rate of change of the vehicle's heading angle measured in degrees/second of rotation about a vertical axis through the vehicle's centre of gravity.
         2.31. "Peak braking coefficient (PBC)": means the measure of tyre to road surface friction based on the maximum deceleration of a rolling tyre.

         2.32. "Common space" means an area on which more than one tell-tale, indicator, identification symbol, or other message may be displayed but not simultaneously.

         2.33. "Static stability factor" means one-half the track width