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Document Title UN R140: Proposal to amend provisions for steering amplitude
Reference Number GRVA-15-55
Date
27 Jan 2023
Summary Proposal to add the text, "In case that saturation of the front tyres happens before the above calculated magnitude angle, this angle may be used as the final steering amplitude, but only if this angle is greater or equal to 6.5 A.” based on the following justification:
  1. Reaching fixed amplitude, i.e., fixed steering wheel angular speed due to given 0.7 Hz sine frequency, needs much more torque with quick steering gear ratio systems than with slow steering gear ratio systems, and produces much more wheel steer.
  2. Car behavior (yaw rate, lateral acceleration and thus trajectory) is similar for all amplitudes above approx. 7 to 8 A (i.e., more than 7 times the steering wheel angle corresponding to 0.3 g), because front tires are saturated. More steer of the tires doesn’t provide more lateral force, so yaw rate and lateral acceleration don’t increase. Continuing to increase steering wheel amplitude after front tire saturation doesn’t give more information.
  3. There might appear in the future some vehicles which have significantly low steering gear ratio (i.e., quick steering characteristics) and may need too much steering wheel torque to achieve the 270 degrees sine amplitude at 0.7 Hz (not reachable by conventional steering robots), then jeopardizing the easy approval of future beneficial steering equipment e.g. steering-by-wire systems.
Source(s) OICA
Rulemaking Area(s) UN R140 ESC Systems
Proposal Status Superseded
Meeting(s)
Related Documents
GRVA-14-30 UN R140: Supporting information on proposal for amendments
GRVA-14-27 UN R140: Proposal for amendments (superseded)
GRVA/2023/9 UN R140: Proposal for amendments (superseded)
Downloads
UNECE server .pdf format .docx format
Excerpts from session reports related to this document
GRVA | Session 15 | 23-27 Jan 2023

109. The expert from OICA introduced GRVA-15-55, an amendment proposal to UN Regulation No. 140 to adapt technical provisions for steering systems with low steering gear. The expert from Canada announced that their delegation would contact OICA for further exchange.

110. GRVA requested the secretariat to distribute GRVA-15-55 with an official symbol at the May 2023 session.
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