Brake-by-Wire: Purely electric brake system of the future by ZF for software-defined vehicles
At its Next Generation Mobility Day in Shanghai, ZF presents a new, purely electro-mechanical brake system for the first time. Braking force is generated at each wheel by an electric motor, i.e. without a hydraulic system and brake fluid. The brake system was developed at ZF’s development centers in China, the USA, and Germany for the global market.
“Our purely electrically controlled braking system is a significant addition to our portfolio of networked chassis systems,” said Dr. Holger Klein, CEO of ZF Group. “With such by-wire systems, we are opening the door to a new era of vehicle control.” Klein added that this is especially true in software-defined and electrically driven vehicles where this type of brake system has even more advantages and open up new freedom in design and development.
In a so-called ‘dry’ brake system, brake fluid is not required any more. Brake pressure is therefore no longer generated by the pressure of fluids in the hydraulic system, but by electric motors. Brake signals from the pedal to the electric motor are also transmitted purely electrically, which is why the term ‘dry brake-by-wire’ is used.
Safe, reliable and sustainable
Compared with conventional braking systems, the new brake-by-wire system, like Integrated Brake Control (IBC), enables shorter braking distances, better recovery of braking energy, and lower maintenance costs.
During automatic emergency braking, the braking distance at a speed of 100 km/h can be up to nine meters shorter than with conventional braking systems. In addition, electric cars can achieve up to 17 percent more range via even better recuperation of braking energy.
With dry brake-by-wire systems in particular, the residual drag torques that occur with conventional braking systems due to minimal contact between the brake pads and the brake discs can be reduced to almost zero. This results in even fewer particulate emissions due to brake abrasion. This lower resistance during driving also saves energy and can increase range in an EV.
Dispensing with a hydraulic system means significantly lower assembly and logistics costs even during vehicle production, as the system consists of fewer parts. And during the vehicle’s service life, the user benefits because brake fluids no longer need to be changed, reducing the amount of servicing required in the workshop.
Even though there is no longer a mechanical connection between the brake pedal and the brake actuators, the braking feel is the same as that of a hydraulic brake. The safety of the data transmission and processing as well as the energy supply to the electric motors is ensured by the duplication of all connections and systems, as is also common in by-wire systems in aviation.
Purely electric, purely hydraulic or combined
With more than 50 years of experience in the development and production of brake systems and with more than three billion brake components manufactured, ZF is one of the largest and most renowned suppliers worldwide.
Vehicle manufacturers can put together their optimum braking system from the classic purely hydraulic to the new purely electric braking system depending on their requirements. Hybrid forms with, for example, a hydraulic system at the front and a purely electric system on the rear axle are also possible. In addition, ZF offers all components of a braking system from a single source, from wheel brakes to parking brakes, and hardware to software.
By-Wire in combination: brake, steering and damping
ZF has one of the most comprehensive portfolios of purely electronically controlled steering, brakes or damping systems for software-defined vehicles. “Networked chassis systems for longitudinal, lateral, and vertical dynamics can improve driving dynamics, and ZF is uniquely positioned in the market with its range of actuators and functions for combining all three dimensions of vehicle dynamics as well,” said Klein. Purely electronically controlled and networked by-wire systems offer better vehicle control, shorter braking distances, more steering flexibility, greater driving stability at high speeds, and greater range and efficiency.