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Dr.-Ing. Gerrit Nowald, Continental Teves AG & Co.oHG, GERMANY
Dr.-Ing. Benjamin Siegl, Continental Teves AG & Co.oHG, GERMANY
The ongoing shift of the automotive industry towards electric vehicles (EVs) also influences the development of brake systems. Since a large share of comfort brake actuations can be realized through recuperation with the electric engine, todays brakes for EVs are often oversized. Additionally, strict regulations for brake dust emissions are expected in the near future. This favors the development of nonstandard brake concepts. Furthermore, a system development approach becomes increasingly important to fulfill increasingly challenging requirements.
The thermal capacity plays a major role for the sizing of brake components and is usually evaluated using downhill and performance tests. Especially in the early development process, simulation reduces design loops and expensive prototypes. Current simulations for sizing can be divided into two categories. On the one hand, lumped thermal models are used for system sizing. Those models are fitted to known products but are not easily applied to new designs. On the other hand, the Finite Element Method (FEM) is used, which yields accurate results for arbitrary designs. However, this method is time-consuming due to model setup, calculation and post-processing and requires expensive licenses. Furthermore, design loops are costly since new CAD geometry has to be designed.
In this work, an in-house simulation tool is presented which enables fast calculation with sufficient accuracy. Rotational symmetry is assumed for the time-dependent temperature field. Arbitrary two-dimensional cross-sections are meshed with triangular elements. The Finite Volume Method (FVM) is used, which in contrast to FEM conserves energy and yields good results even with few elements. Sections with different materials can be defined and temperature-dependent material parameters are considered. The simulation tool has been validated by comparison with FEM simulation results and dyno measurements and has been successfully applied to disc and drum brakes.
The simulation tool is embedded in MatLab Simulink. Arbitrary maneuvers can be calculated, which can be predefined, simulated, or measured on the dyno or during test drives. Additional components of the brake system such as ABS and ESP or the drivetrain such as battery and electric engine including recuperation and derating can be easily coupled to the thermal model. Furthermore, the thermal feedback during braking due to temperature-dependent friction properties can be considered. A rapid model setup combined with short simulation times allow fast variation of vehicle parameters, brake system design, maneuver and boundary conditions as well as brake geometry and material.
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