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Document Title UN R140: Proposal for amendments
Reference Number GRVA/2023/9
Date
8 Mar 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Proposal Status Superseded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GRVA-15-55 UN R140: Proposal to amend provisions for steering amplitude (superseded)
GRVA-16-23/Rev.1 UN R140: Proposal for amendments (superseded)
GRVA/2023/23 UN R140: Proposal for a supplement (superseded)
Downloads
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Excerpts from session reports related to this document
GRVA | Session 16 | 22-26 May 2023

96. The expert from OICA introduced ECE/TRANS/WP.29/GRVA/2023/9 as amended by GRVA-16-23/Rev.1, aimed at modifying testing requirements on the final steering amplitude in case of front tyres saturation. The experts from Japan and UK supported the revised document, as it addressed their comments.

97. The experts from Canada and the United States of America inquired if there was enough evidence demonstrating that the modification proposed would not lead to a safety decrease. They asked for more data and documentation to support this proposal.

98. The expert from OICA responded that no negative impact on the safety of vehicles was expected, as shown in previous GRVA sessions, based on evidence. She clarified that the reason for this proposal was the introduction of new steering technologies with low steering ratio. She stated that there was no added value in continuing to increase the steering wheel amplitude during the test after the front tyre saturation.

99. GRVA agreed to resume the discussion at its next session.
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