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EuroBrake 2022: New procedures for brake testing and type approval session overview

The New procedures for brake testing and type approval session will take place on Wednesday May 18th and will be chaired by Ignacio Lafuente of Applus IDIADA and co-chaired by Carlos Agudelo of Link Engineering Co.

Topics and speakers for the session include:

New assessment and testing methodology for vehicle type approval

Carlos Lujan, Applus IDIADA

Technological innovations in the field of Connected and Automated Driving have a strong impact in different areas in the automotive industry. Among those areas, the effect on vehicle homologation procedures is game changing, in a way that requires a brand-new approach. Traditionally, the homologation process based on the UNECE Regulatory framework has been a single step at the end of the development phase, where regulations normally defined a series of repeatable scenarios to be evaluated, where the effect of the driver is typically suppressed by means of the measurement of the inputs on the vehicle commands or by means of the use of driving robots.

This approach was initially challenged by the introduction of assisted systems, such as Advance Emergency Brake. Those systems are commanded by Electronic Control Systems which, in some circumstances, may control certain vehicle functions, such as braking or steering. The introduction of such functions required a different approach to the vehicle type approval, to evaluate possible failures associated to the Electronic Control Systems.

In such context, concepts such as Functional Safety (FuSa) or Safety Of The Intended Functionality (SOTIF) were introduce as part of the type approval process. This new approach turned the technical evaluation of the compliance from a testing activity in selected scenarios into a combination of testing and assessment of the manufacturer safety concept.

However, the introduction of the first SAE L3 functions into the market add a new layer of complexity into the type approval. Such technologies replace the human driver during certain dynamic driving tasks, within an unlimited number of scenarios. This circumstance does not allow the classic strategy of removing the human effect from the test scenarios and required a second loop in the modification of the type approval processes, so as to move from an evaluation of the performance to an evaluation of the behaviour of the vehicle. As a result, UNECE WP.29 published the “Framework Document on Automated/Autonomous Vehicles”, a document whose purpose was:

a) To provide guidance to WP.29 subsidiary Working Parties (GRs) by identifying key principles for the safety and security of automated/autonomous vehicles of levels 3 and higher.

b) To define the work priorities for WP.29 and indicate the deliverables, timelines and working arrangements for those certain work products related to those priorities.

Consequently, several actions took place which have paved the road into a new type approval approach, currently under development, but with a series of principles widely accepted by the rulemaking community. Examples of such actions include:

a) New working group structure within UNECE WP.29

b) Development of a series of New Assessment and Testing Methods (NATM) which combine the classic test on the proving ground with new tools, such as the assessment of the manufacturer safety concept, the use of simulation or the real-world testing.

Emission of brake wear particles from modern passenger car brakes: a necessary certification family for brake emissions?

Hiroyuki Hagino, Japan Automobile Research Institute

A brake wear dynamometer with a constant-volume sampling system was demonstrated to measure driving distance-based mass emission factors of airborne brake wear particulate matter (PM) and particle number (PN).

This presentation will show the effect of emissions associated with vehicle type on brake loads in the WLTP-Brake cycle. According to the worst-case principle, the EU suggests that criteria pollutant emissions of all vehicles of the certification family should be determined for a test mass equalling test mass high and the respective road load factors. (e.g. WLTP-DHC14-DTP11-02).

The results of this study contribute to the discussion of the necessity of a certification family based on a function of vehicle weight per brake friction for the measurement of brake emissions.

New brake test procedures under development and planning

Carlos Agudelo, Link Engineering Co.

This presentation focuses on industry standards under revision or development to address new braking technologies involving regenerative braking, and novel friction couples. New vehicle architectures, upcoming type approvals for non-exhaust brake emissions, new propulsion and powertrain systems, and the introduction of new materials and coatings demand a deep revision of current laboratory methods. Also, extended service lives and usage, are making new failure modes (like corrosion), require particular attention. The presentation provides an overview of the main standards under development from SAE, ISO, and the European Commission.

Wet grip braking performance on worn tyres

Ricard Anadon, Applus IDIADA

Regulatory performance parameters are always measured on new state tyres.

Most of performance parameters are not showing relevant deterioration overtime, however, it is proven that Wet Grip performance is deteriorating progressively as the tyre worn out during its life.

Wet grip performance deterioration means vehicle longer stopping distance on wet condition.

It was also found that the wet grip index on worn tyres could not be predicted from the wet grip index on new condition tyres, at least on C1 tyres. No correlation was found. As this is a safety issue, Regulatory authorities and major stakeholders agreed to develop new test method and thresholds for wet grip on worn tyres.

Basic test protocols described in UN R117.02 are observed, however, there are many specific topics that need to be addressed, such as, how to obtain artificially worn tyres fully representative of natural worn tyres, the use of reference test tyres in worn or new condition, new limits, among others.

This presentation is a summary of the conclusions so far and the proposal for new Regulatory requirements is proven that Wet Grip performance is deteriorating progressively as the tyre worn out during its life. Regulatory authorities and major stakeholders agreed to develop new test method and thresholds for wet grip on worn tyres.

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