Audi e-tron brakes
The Audi e-tron is the first electric series production model uses an electrohydraulically integrated brake control system.
The wheel brakes are actuated hydraulically, the reinforcement is actuated electrically, and the activation is actuated electronically.
The control unit detects with how much force the driver is depressing the brake pedal and calculates how much braking torque is needed within milliseconds.
If the recuperation torque is not sufficient, hydraulic pressure for the conventional friction brake is generated in addition. Put into motion by an electric spindle drive, the displacement piston pushes the brake fluid into the brake lines. The transition from the engine brake to the pure friction brake is smooth, and the driver does not notice it.
A second piston generates the familiar pedal feeling for the driver’s foot by means of a pressure-resistant element. Thanks to this brake pedal simulator, the driver is not affected by what is happening in the hydraulics. In the case of ABS braking, pressure buildup and reduction are not noticeable in the form of irritating hard pulsations.
The electrohydraulic brake system is activated when the driver depresses the left-hand pedal so hard that the deceleration exceeds 0.3 g; otherwise, the Audi e-tron decelerates through recuperation via the two electric motors. The brake control system build up brake pressure for the wheel brakes with great precision and roughly twice as fast as a conventional system.
When automated emergency braking is performed, there are only 150 milliseconds between the initiation of the brake application and the presence of maximum brake pressure between the pads and disks. This is barely more than a blink of the eye and creates impressively short braking distances. Even at a very slow speed, such as during maneuvering, the car decelerates via the wheel brakes because this is more efficient than electric braking in this case. Otherwise, the electric motor would have to use valuable battery current to decelerate actively at low rotational speeds.
The “brake-by-wire” technology of the electrohydraulically integrated brake control system enables a larger air gap, i.e. a greater distance between the brake pad and brake disk, to be set. This minimizes possible friction and heat generation and contributes actively to the vehicle’s long range.
The recuperation technology in e-tron can significantly increase range, depending on topografy on roads.
On e-tron 55 and 50 the recuperation can reach 220kW depending on speed. On e-tron S it can reach 275kW. The most powerful recuperation on the marked.
The video below shows how the system works.
See also article on one pedal driving