A Home for all Chassis Control Systems

A control platform for everything included in the chassis – that's cubiX?. ZF's software product is already active in the first production vehicles. Some functions show the potential of the solution – which car manufacturers can also further exploit.

The challenges are clear. In automotive electronics, it becomes more and more complex when too many systems control each other in parallel. So what if all the assistance systems that aim to keep the vehicle stable were integrated into one platform?

"cubiX makes it possible to implement certain driving functions. In doing so, it is possible to address exactly those systems that are actually available in the respective vehicle."

Dr. Caspar Lovell, cubiX Program Management Lead

cubiX? from ZF is that platform, bringing together all control interventions to form Vehicle Motion Control. This is a paradigm shift in chassis development. Whereas engineers used to use the properties of certain components and systems to define the characteristics of a chassis, in the age of the software-defined vehicle, it is the other way around. Functions now determine the basic character of the chassis – then you look at how these functions can be implemented by controlling existing components. This is why cubiX is so future-proof and attractive to vehicle manufacturers as they can use their own control systems on the cubiX platform. The benefit is not tied to the use of specific hardware, not even from ZF. cubiX is scaleable and can control third-party components.

Programming the DNA of the vehicle

ZF demonstrates the potential of the platform in the form of chassis functions, which can be integrated into cubiX as software packages on request. This makes it clear that ZF is not only serving the trend toward software-defined vehicles by providing the platform but is also "filling" it with its own functions.

"Manufacturers can take over these from us, order additional functions from us or implement their own developments," explains Frank Schmidt, Head of Development cubiX.

One of these functions, Variable Driving Characteristics, makes it clear what the ZF developers are all about: adapting the specific driving character of a car individually to the driver's wishes – between quiet and comfortable cruising and agile, sporty sprints. "Unlike the 'Sport Mode' switches, which have already been widely used, we not only change the actuation force when steering, but also the vehicle's response to steering input. This gives the sportier and more direct driving experience a new quality," says Schmidt. Thanks to the software function, a much wider range of driving characteristics can be implemented with one and the same basic chassis.

Further features that ZF offers as functions for cubiX ensure greater safety: Pre-Stability Control, for example, intervenes early enough in the driving process that the sometimes violent ESP skid brake no longer must be activated. Thanks to the coordinated interaction of several actuators such as steering, brakes or rear-axle steering, oversteer or understeer can be avoided from the outset.

With the Torque Steer Compensation function, cubiX compensates for the disadvantage high-powered vehicles often have when accelerating hard: Although the steering wheel is kept straight, the slightest disturbances – such as bumps in the road – make the car unstable, which can lead to unexpected lane misalignment. The cubiX function works effectively against this with timely and concise interventions of the rear-axle steering.

Anyone who has ever driven a trailer on the highway will long for the cubiX Trailer Stability Assist function. Above a certain speed, trailers tend to sway – a threat to the stability of the vechicle and the trailer. Here, too, the assistance function available in cubiX corrects in a targeted, concise and timely manner, without having to reduce its cruising speed.

Vehicle Motion Control Packages

The Crab Move function is aimed at the not-so-distant future of highly automated driving. However, unlike most other ZF functions, it is dependent on the availability of rear-axle steering. Because it is then possible to have the rear- and front-axle steering turned in the same direction, the vehicle maneuvers to the side without turning over the vertical axis – similar to the crab gear. As a result, a vehicle can be kept stable during dynamic driving. This function is also particularly valuable when it comes to making lane changes imperceptible to the occupants. For example, car passengers who drive autonomously in accordance with Level 3 of highly automated driving can read or watch films without getting motion sick.

"We will develop further functions and bundle them into packages, for example to increase performance and safety or to facilitate automated driving," explains Dr. Caspar Lovell. "The overall goal of cubiX is to create the specific driving characteristics that the car manufacturer wants." This does not necessarily require ZF actuators or ZF software. But of course, the Group's expertise and portfolio can be put to good use for this purpose.