Efficient interaction between recuperation and friction brake

Recuperation is an important component in increasing the efficiency and, therefore, the range of the Audi Q6 e-tron. During development, particular focus was therefore placed on increasing maximum efficiency and availability during standstill blending at low speeds. This means that in the Audi Q6 e-tron, around 95 percent of all everyday braking processes can be covered by regenerative braking, i.e., by the electric motors. The use of the friction brake during brake blending thus takes place later or less frequently. Under ideal conditions, the Audi Q6 e-tron recuperates up to 220 kW. The temperature and state of charge of the battery play a key role here. Recuperation takes place on the front and rear axles, with smaller decelerations handled by the rear axle alone for reasons of efficiency. Higher recuperation rates arepossible on the rear axle.

In the PPE, regenerative breaking is no longer handled by the brake control system, but by the HCP1 - one of the five high-performance computers - which is responsible for the powertrain and chassis in the PPE. This increases the influence of the powertrain on the braking system. The Intelligent Brake System (iBS) familiar from previous e-tron models has been significantly enhanced as part of the Premium Platform Electric. Axle-specific brake blending as described above is now possible for the first time.

During regenerative breaking, the system decides on an axle-specific basis whether the use of the friction brake is necessary or whether recuperation via the electric motors is sufficient. As soon as the driver presses the brake pedal, energy recuperation takes place on the rear axle in the first step. If the driver brakes harder, the front axle also recuperates. If the brake pedal is applied even harder, the front friction brakes are added first. If the braking power is increased even further, up to the use of ABS, the rear brakes provide support. Even in situations when ABS is applied, the electric motors continue to recuperate with the same power. The transition from regenerative breaking and recuperation via the electric motors to the mechanical braking effect via the hydraulically actuated friction brake is imperceptible to the driver. The brake blending ensures a well-dosed pedal feel with a clearly defined, constant pressure point.

As is typical for Audi, there is the option of two-stage coasting recuperation, adjustable via the paddles on the steering wheel with a deceleration of up to 1.5 m/s2. Furthermore, particularly efficient coasting is also possible. Here, the electric SUV rolls freely without any additional drag when the foot is taken off the accelerator pedal. Another variant available in the Audi Q6 e-tron model series is drive mode “B”, which comes very close to what is colloquially called the “one-pedal feeling”. If the driver selects the automatic function in the MMI, the vehicle automatically recuperates energy where appropriate. Parameters used inclode route data stored in the navigation system, such as gradients, curve radii, town signs or speed limits. Another important factor is the traffic ahead.

A number of components are integrated into the recuperation processes: the two electric motors, the HCP5 and HCP1 computers, the long-range radar and the front camera for Adaptive Cruise Control to scan the traffic ahead, the Intelligent Brake Control System (iBS) for brake control and blending, i.e. the transition between the friction brake and the regenerative breaking, and the HCP3 so that the amount recuperated power is displayed to the driver on the Audi Virtual Cockpit.

The Q6 e-tron is also equipped with an electronic brake control system. The technology combines brake boosting and ABS/ESC control functions in a single system. Generously dimensioned brakes with internally ventilated steel brake discs achieve outstanding deceleration. They have four-piston fixed brake callipers (six pistons on the S model) on the front axle and single-piston floating callipers with electromechanical parking brake on the rear axle. The brake callipers are optimized for braking to a stop at low speeds. Special springs support the quick and complete opening of the brake pads. Brake pad wear detection on the right-hand side of the vehicle is standard, as is the electromechanical parking brake.

The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.