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In the rapidly evolving world of electric vehicles (EVs), regenerative braking is transforming how we design and predict the longevity of brake systems. But how do traditional testing methods hold up in this new era? A groundbreaking SAE technical paper from ZF Active Safety US Inc. dives deep into adapting the Simulated Los Angeles City Traffic (SLACT) procedure to account for regen braking, offering practical strategies for optimizing pad thickness, reducing costs, and enhancing packaging without compromising safety.
High-Level Summary
This SAE paper, authored by Wael Jayyousi and Saikiran Divakaruni, presents a modified SLACT dynamometer test procedure tailored for EVs with regenerative braking. Originally designed for internal combustion engine (ICE) vehicles, the standard SLACT test underestimates lining life in EVs where regen systems handle much of the deceleration, leading to less wear on foundation brakes. The authors detail a step-by-step approach to incorporate vehicle regen strategies: calculating braking power and energy per stop, subtracting regen contributions (up to 40 kW in the studied EV with a 60/40 front-rear split), and adjusting dynamometer inertia for accurate simulations.
Key findings include:
- Extended Lining Life: Baseline SLACT without regen projected ~29,000 miles; with regen, it soared to ~230,000 miles for a 10 mm usable lining thickness.
- Pad Thickness Optimization: Reducing thickness to 7 mm still yields ~161,000 miles, enabling cost savings and better packaging while ensuring performance in regen-failure scenarios.
- Testing Details: Based on 925 stops simulating 2,000 miles, with results from six lining materials showing consistent trends in wear reduction.
- Practical Implications: The updated procedure helps manufacturers predict real-world lining life more accurately, supporting EV design advancements.
The paper includes detailed equations, tables (e.g., vehicle parameters, wear measurements), figures (e.g., power calculations, pad diagrams), and an appendix with raw data, making it a valuable resource for brake engineers and suppliers.
View the full SAE paper here to explore the complete methodology, results, and conclusions.
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