Porsche’s New Brake Force Distribution Concept for EVs

Battery electric vehicles, or BEVs, present new challenges for chassis development, particularly when it comes to braking and recuperation. Porsche engineers are working on new concepts for brake force distribution that will improve recuperation without compromising comfort.

One of the major technical challenges in chassis development for BEVs is blending, which combines regenerative and hydraulic braking. Ensuring a smooth transition between the systems is crucial, as the braking systems operate differently. An electric motor always delivers the same braking torque, while the torque from its hydraulic counterpart may vary due to environmental influences such as temperature and humidity.

Porsche has developed algorithms for the Taycan that prevent this from happening. They monitor the hydraulic system continuously and calibrate the brake during each charging process to determine the current ratio of brake pedal travel to brake pedal force. This allows the algorithm to estimate how much power the hydraulic system will deliver the next time the vehicle is braked and deploy it precisely so that the transition to recuperation mode remains smooth.

Brake Force - Porsche's breakthrough in blending regenerative and hydraulic braking in electric vehicles.

With typical, everyday driving in Taycan, 90 percent of the braking is done using electric power only, i.e., without the involvement of the hydraulic system. The latter is only used at speeds below 5 km/h when the electric motors barely develop braking power. In addition, the friction brake steps in when the electric motors do not have sufficient deceleration power, for example, during full braking from high speeds. The Taycan Turbo S can generate up to 290 kW of electric power during braking. At this power level, two seconds of deceleration are enough to generate electricity to drive around 700 meters. Overall, recuperation increases the range by up to 30 percent.

In vehicles, braking power is usually unequally distributed: Two-thirds of it is provided by the front axle, and one-third by the rear axle. The same ratio applies to the electric system in the Taycan: The front electric motor provides two-thirds of the braking power, and the rear one provides one-third. This potential could be leveraged by varying the distribution of the braking force between the axles. In this context, it is important to note that, for reasons of driving stability, the brake force distribution is not changed during normal driving.

“The driver must not feel the transition between the systems,” emphasizes Martin Reichenecker, Senior Manager Chassis Testing at Porsche Engineering.

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