Los Angeles City Traffic is one of the main standards for Brake Durability testing worldwide. Almost all the OEM's (US and non-US brands) are periodically performing this test during the development and validation of their braking systems. Generally, vehicles are tested in this route to characterize the brake noise performance (low and high frequency) but also to define a clear usage pattern for brake usage. During the recent years, with the increase of market share for BEVs (Battery Electric Vehicles), the brake NVH development has slowly taken different path, concentrating on different concepts (severity and not only occurrence), but also using very well known NVH routes in order to analyze how regenerative braking is changing the behavior of the braking systems from an holistic point of view. The technical objective of this abstract is to find and define precise metrics and objective data that better help to objectivize and compare the regenerative braking behavior results in brake NVH durability routes. The main parameters are mainly related with brake usage metrics (Brake application/km, speed, deceleration and brake pressure outputs, brake temperature distribution) and brake NVH (noise events outputs). In detail, it is needed to characterize not only traditional parameters for brake usage, but also how many regenerative stops are performed in a very well know and characterized route as LACT. This is providing a very useful analysis about the energy management of the vehicle in real conditions of usage. The total recovered energy is calculated, analyzing every single performed stop. A brake classification in terms of regeneration is also proposed in terms of type of stops: throttle release, full regen stops or partial regen are considered during the route (and the analysis about the relative occurrence of this type of stops over the route is proposed). Obviously also noise occurrence, SPL and frequency are studied to qualitatively appreciate the occurrence reduction in this route, despite this is not the main objective of the paper. To provide a robustness analysis, different routes for LACT are also considered to demonstrate the variability consistency between different routes. In particular, stops per km, brake temperatures, speed, deceleration and pressure distributions, and finally NVH characteristics are evaluated in order to establish the robustness of the methodology.
Ing. Fabio Squadrani, Senior Manager, Applus IDIADA; Mr. Bernat Ferrer Almirall, Chassis, Active Safety & Durability Manager USA, Applus IDIADA; Mr. Suguru Nakajima, Business Development Japan, Applus IDIADA