Electric vehicles (EVs) have the great advantage of regenerating brake energy. This allows deceleration of up to 3 m/s2 and covers approximately 85% of all brake procedures in real driving cycles. To date, a recuperative braking system is not officially part of the service brake by law since regenerating is not possible while the battery is not well conditioned or fully charged. Additionally, an electric vehicle needs to be equipped with a heavy battery to offer a competitive driving range compared to a vehicle with an internal combustion engine. The higher overall mass of EVs results in the need for a larger dimensioned conventional friction brake to satisfy todays performance criteria.
This paper analyses the potential of downsizing the friction brake by using auxiliary consumers in a feasibility study for battery-independent recuperative braking for a worst-case scenario. A vehicle model with an integrated simulated driver is used to generate the brake desire at a current performance test. The electric motor and inverters power losses themselves al-ready eliminate a part of the requested brake power. A control allocation algorithm is used to distribute the generated power to different energy sinks. It regulates the overactuated system with respect to the capabilities of the actuators. Beyond their basic power, auxiliary consumers can be overloaded for a certain period of time. A model of universal consumers considers their overload potential by evaluating the provided work to avoid overheating, and complements dynamic characteristics. Additionally, the paper considers the optional use of a battery in this system.
The objective is to analyse the potential of downsizing the friction brake by using battery-in-dependent regenerative braking.
Wagner Daniel, Kugelmann Philipp, Prof. Dr.-Ing. Lienkamp MarkusTechnische Universität München, Germany; Dr.-Ing. Semsch Martin, Continental Teves, Germany