Key to autonomous driving: Technology trend at the IAA: Braking by cable

Electronics replace mechanics: By-wire systems eliminate pedal travel and hydraulic pressure. This creates space, saves energy—and is an important building block on the path to autonomous driving.

At the IAA Mobility in Munich, the spotlight is on a technology designed to make cars quieter, more fuel-efficient, and safer. And it paves the way for automated driving: "By-Wire." The principle behind it is simple: Instead of transmitting power mechanically or via hydraulic fluid, commands from the pedal or steering wheel are transmitted as electronic signals to compact actuators in the brakes, steering, or drivetrain. This saves components, frees up space in the vehicle, and enables functions that would be difficult to implement with conventional technology.

The supplier ZF is primarily showcasing its brake-by-wire systems at the trade fair. The "dry" version of the system requires no brake fluid at all: an electric motor is located at each wheel, directly applying the brake pads. The system is said to be particularly fast and precise compared to the hydraulic version. It also prevents the slight "grinding" of the pads against the disc, which consumes energy and generates particulate matter in conventional brakes. For the supplier's customers, the automakers, the by-wire approach offers even more advantages: fewer parts, fewer wires, simpler installation—and more freedom in the layout of the engine compartment and interior.

ZF also offers a hybrid variant, in which the rear axle typically brakes electrically ("dry"), while the front axle continues to operate hydraulically. This is suitable for heavy pickup trucks, for example, where the rear axle must provide high holding forces for parking. The entire system is controlled by a compact unit that combines the brake booster, stability control, and—if desired—other driving dynamics functions.

"Act-by-Wire" from Bosch

Bosch takes this even further and speaks of "act-by-wire" – the electronic control of several vehicle functions simultaneously. At the trade fair, the Stuttgart-based company is showcasing a brake-by-wire system that eliminates any mechanical connection between the pedal and the brake, as well as software that controls the brakes, steering, chassis, and drivetrain together. The result should be more precise interventions by assistance systems, shorter reaction times in emergencies, and noticeably more comfort in everyday driving. One example is the "Comfort Stop": The controlled interaction of brakes and electric drive is said to reduce the usual braking jolt by 70 to 90 percent – ​​according to Bosch, this increases the feeling of comfort and reduces travel sickness.

But why do suppliers and manufacturers go to all this trouble? Firstly, modern assistance systems and future automated driving require brakes that can be dosed with lightning speed and precision. Electric actuators can build up pressure almost instantly, and the electronics coordinate the intervention seamlessly with the engine and chassis. Secondly, by-wire helps with efficiency: If the friction brake operates less frequently because the car decelerates a lot using the electric motor and recovers energy in the process, the range increases. And if the pads aren't constantly in minimal contact, wear and brake dust are reduced – an issue that is becoming even more important due to new EU limits.

Updates like on a smartphone

Last but not least, the technology is a perfect fit for new vehicle architectures: Instead of dozens of individual control units, a few high-performance computers handle the work, and functions are added via software updates – much like with smartphones. In the future, it might be possible to purchase and download a particularly sporty steering feel from a car manufacturer's online store. Or even software that completely handles steering itself. Because in the medium term, the steering system will also become a candidate for de-mechanization: If commands are transmitted electronically, more variable gear ratios, more compact steering wheels or joysticks, and more legroom are conceivable.

This is still a cautious transition – especially in Europe. Many manufacturers are initially opting for hybrid solutions in which traditional technology and by-wire work together. But the direction is clear: The more cars become electric, networked, and software takes center stage, the more worthwhile the leap will be. In most cases, there will no longer be a mechanical fallback option in the future. This would miss out on much of the potential of wired technology. By-wire also opens the door to entirely new vehicle concepts. Eliminating the need for bulky brake boosters and long hydraulic lines allows for more freedom in the design of the front end and interior.

Other suppliers are also driving change

It's no wonder that other suppliers are also driving change. Continental, for example, offers a very compact, electro-hydraulic brake with a "one-box" solution and is also working on variants that combine electric and hydraulic systems. Brembo, with "Sensify," is pursuing a modular by-wire approach that can completely remove the pads from the disc during normal operation. This reduces losses and wear without compromising safety.

What all systems have in common is that they have consistent redundancies, ensuring the car stops safely even if a control component fails. This is a basic prerequisite for authorities to approve the technology and for manufacturers to be able to widely introduce it.

By-wire systems are not about technology for technology's sake, but about tangible benefits in everyday life: shorter braking distances in dangerous situations, smoother stops in city traffic, less wear, greater range - and the basis for assistance and automated driving to function safely.