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UN R140: Proposal to amend provisions for steering amplitude
Document GRVA-15-55
27 January 2023

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.

Submitted by OICA
Status: Superseded
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Previous Documents, Discussions, and Outcomes
8. (a) | Electronic Stability Control

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.

8. (a) | Electronic Stability Control

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.

8. (c) | Clarifications
8. (a) | Electronic Stability Control

93. The expert from OICA presented GRVA-14-30, introducing GRVA-14-27 with amendments to UN Regulation No. 140 clarifying testing procedures for low gear steering. The expert from Canada noted the figures proposed for the steering robot mechanical power in the proposal and asked if OICA could share data supporting them. The expert from France expressed interest for the proposal, mentioned supporting material in ISO standards dealing with such testing conditions that could serve as a reference and required more time to study the proposal

95. GRVA agreed to keep GRVA-13-23, GRVA-13-39 and GRVA-14-27 on electronic stability control on the agenda for its next session.

Related and Previous Documents
GRVA-14-30
GRVA-14-27
GRVA/2023/9
Relates to UN R140 |