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Smart Sensors and Car Chassis from A to Z

Chassis actuators are involved whenever cars brake, steer or cruise along on a comfortable suspension. ZF has the most comprehensive offering in the industry, including software functions for the control system. The result is an attractive mix.

Author: Andreas Neemann, 2023-07-21

Cars are becoming increasingly intelligent. In addition to the driver, the software often determines how new vehicle models respond. Code is integrated into assistance systems or autonomous driving functions. These functions define the specific path within milliseconds. Or algorithms determine the optimal parameters in terms of acceleration, steering angle and damping depending on the selected driving profile. Thanks to a wealth of information from camera and sensor data, the software always calculates the most efficient, most comfortable or safest driving style.

The software-defined vehicle is a trend that the entire industry, including ZF, is embracing. The "command structure" – also known as the E/E architecture – is changing in the automobile. Decentralized is becoming centralized. A complex control program located on a host computer assumes more and more powers. Figuratively speaking, software is the "new queen" that governs with her greater overview over the heads of existing "small princes," namely decentralized control for brakes, damping, steering and many other systems.

Functions are Trumps

"This trend brings numerous future opportunities for ZF, because no matter how comprehensive the "powers" of the host computer are in the new software-defined vehicle, actuators will continue to provide the steering, braking and damping force adjustment," explains Dr. Christoph Elbers, Head of Engineering Vehicle Motion Control at ZF.
"This trend brings numerous future opportunities for ZF."
Dr. Christoph Elbers, Head of Engineering Vehicle Motion Control

And for all these the Group has a complete portfolio that is unique in the industry. These products will also be bundled in a separate division from 2024. With regard to the physical handling degrees of freedom of longitudinal, transverse, and vertical dynamics (i.e., braking or accelerating, steering or damping), the new Group unit provides everything that a passenger car needs with the further networking with the drive.

What ZF offers is not only mechanical and mechatronic components such as axles, dampers, brakes and steering systems. ZF's immense wealth of experience of functions that control the respective mechanics is almost more valuable. ZF has been developing the functions for its individual systems for decades. "We adapt this advantage to current requirements and develop software for ZF chassis functions so that they can be conveniently networked with each other," says Elbers. For example, a ZF rear axle steering system harmonizes "ex works" with a ZF front axle steering system and brakes – and precisely this combination can respond brilliantly to an incredible number of driving dynamics requirements and dangerous situations. The Group is therefore a market-leading technology partner and overall supplier for vehicle motion control (VMC).

Everything From a Single Source

ZF serves the new trends toward electrification and software-defined vehicles in several ways: As a system integrator, as a platform provider, as an innovator or, as before, as a supplier.

Firstly, ZF can support automotive manufacturers as a system integrator. "This is particularly attractive for relatively new players without decades of in-house development tradition, corresponding experience and major resources," says Manfred Meyer, Head of Engineering Division Chassis Solutions at ZF.

Everything from a single source

The manufacturers specify the desired driving behavior, the individual "chassis DNA" of their model – such as crisp, sporty steering, tight suspension, precise steering behavior. ZF provides all systems including functions that turn this behavior into reality.

A second approach is aimed at automotive manufacturers who see themselves responsible for system integration or who at least partly want to rely on actuators from other suppliers. You can still use a ZF platform: cubiX. The control software package acts as vehicle motion control coordinator. Based on sensor data from the entire vehicle, the cubiX control algorithms coordinate steering, brakes, chassis and drive actuators as a holistic system. With an electric drive, cubiX also influences the recuperative braking component. ZF's VMC platform not only optimizes vehicle handling with regard to comfort, dynamics and efficiency, but also forms the basis for advanced driver assistance systems (ADAS). "cubiX is our first pure software product with a decisive advantage: It is compatible with various actuators, regardless of the manufacturer or the specific design," says Engelke. "We therefore offer manufacturers the flexibility to implement different model ranges with one and the same control platform without additional integration effort."

Innovative Steer-by-Wire Technology

Thirdly, ZF's role as an innovation driver is becoming increasingly important. Especially with the increasing uptake of electric vehicles, the demand for by-wire technologies will increase – in particular steering systems and brakes with no mechanical connection between the driver's seat and actuator. ZF was one of the first suppliers to go into volume production with a by-wire steering system in 2022. Steer-by-wire systems stand out with greater design leeway and improved system capability. The latter is not only important for highly automated assistance systems such as lane keeping assist. Even if drivers steer themselves, these systems make life easier.
"Our particular strength is that we can design steer-by-wire systems so that they are indistinguishable in terms of feel and feedback from previous electric power steering systems with a mechanical connection to the road."
Manfred Meyer, Head of Engineering Division Chassis Solutions at ZF

For example, when parking, half a turn of the steering wheel triggers a much larger steering angle than during normal driving. The extent to which the people behind the steering wheel accept these systems will also depend on how safe, comfortable and dynamic they are – in other words, how they "feel." Nobody wants to drive a car whose steering wheel has the same kind of vague response as a joystick on a computer game. Feedback is required for you to "feel" via the steering wheel the contact between road and tires. When developing its steer-by-wire system, ZF draws on the immense experience of three decades of steering expertise. The Group has developed a unique torque feedback concept. "Our particular strength is that we can design steer-by-wire systems so that they are indistinguishable in terms of feel and feedback from previous electric power steering systems with a mechanical connection to the road," explains Meyer.

This leads to the fourth point: The uncompromisingly high level of safety that is still required for many passenger car systems. "Because steering and brakes must never fail, their control relies on multiple redundant systems," explains Meyer. Not only does the host computer access these systems for networked driving functions – other control units always remain one level below it. Engineers talk about "brain" and "spinal cord" in allusion to biology. Reflexes are often embedded in the spinal cord in humans and animals where they can be reliably and instantly retrieved through thought processes. The car electronics must control the steering and the brake in an equally reliable and fail-safe manner.

The Future Needs Everything

Even if the trend toward software-defined vehicles currently dominates – not all ZF actuators will in future be smart actuators designed to receive their commands from a host computer. Nor will ZF become a "code vendor" for automotive manufacturers, allowing them to supplement their own driving functions in future based on ZF's decades of experience. "But we are open to a reallocation of roles with manufacturers and to new business models," says Elbers. This applies, for instance, to the need for over-the-air updates – when new functions can be "loaded" onto the vehicle via the cloud without a workshop visit. And it also includes faster and leaner development cooperation.

Or to use the same metaphor: ZF has long recognized the "new queen" software in automotive electronics – and will either be able to build a castle for her or support her with very efficient bureaucracy that ensures optimal administration. She just needs to say what she needs.