Systems Meet Components

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Tags: AutonomousDriving, Emobility

Two ZF developers explain in an expert discussion how they join forces to make a chassis fit for autonomous driving.

ZF Editors, November 27, 2017

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ZF experts Dr. Caspar Lovell and Dominik Vogt explain how they are developing chassis that are fit for the future by using systems and component expertise.

Historically, ZF got its start as a component supplier, yet for many decades the company has also viewed itself as a systems supplier. Where does the component end and the system begin?

Lovell: Those are both flexible terms, which makes them hard to define. Many products that ZF develops and sells have the characteristics of systems: a vehicle’s brakes, steering, and transmission, for example, are all built from many different electronic and mechanical parts. So we could actually refer to them as individual systems – and we often do. For our customers, however – the automobile manufacturers – these are all components that are a part of the system that is the entire vehicle. So it always depends on your frame of reference. At ZF, we are also active at this system level – we support the integration of our products into the vehicle. And we combine our individual systems into a group that can do a whole lot more. Adding this level of functional value, like we have done with our Integral Chassis Control (ICC) software, is usually only possible at the system level.

Vogt: In general terms, I would describe a current ZF OEM component as such: an electromechanical actuator that can be controlled digitally and therefore has a software interface. So specifically, an absorber whose damping force can be varied electronically or our AKC, which adjusts the steering at the rear axle. But it’s only this interface, this ability to be controlled electronically, that makes the components interesting for systems integrators – regardless of whether they work here or at the OEM.

How much does the interaction between systems and components shape development activities at ZF?

Vogt: Both depend on each other. Our knowledge when it comes to components enhances our integration know-how or makes it possible in the first place. Since we are familiar with our AKC product, we can also think about how best to incorporate it into a chassis within the terms of connecting the entire system. The Active and Passive Safety Technology Division(formerly TRW) was especially responsible for strong growth – when it comes to components that we offer, but also with regard to systems expertise.

The Component Developer: Electrical engineer Dominik Vogt played a role in the development of AKC.

What does that mean specifically?

Vogt: On the one hand, we can now offer an entire dynamic driving chassis from one source with the brakes, front-axle and rear-axle steering, active chassis, and electric drive. On the other hand, we now know everything there is to know about all these components, you could say from the “inside view of the developers.” What, for example, do the brakes and their wheel speed sensors and accelerometers tell us about the road condition, and how can we use this information within the terms of the connected system?

What makes this kind of additional systems know-how valuable? It’s not like this will cause ZF to suddenly sell more absorbers or brakes than before...

Lovell: Maybe it will, if indirectly. The idea isn’t to just develop and then sell products. We are seeing increasing demand for our services as systems integrators, because OEMs also want to outsource these jobs to qualified suppliers. And as a result, we aren’t only generating additional revenue. Suppliers that can provide these services also play a more prominent role in the manufacturers’ strategic planning. In fact, this expertise is mandatory if we want to stay at the top of list and ahead of competitors in the future. Furthermore, it can open a lot of doors when it comes to selling additional components that specifically support this system integration.

The System Integrator: Dr. Caspar Lovell is currently the project manager of the Mechatronic Systems product line.

Which means this must work even better with the new players in the mobility market...

Lovell: You’re absolutely right, our strength in components and systems is truly a major advantage. Start-ups or IT companies simply can’t match our experience from decades of automotive development, at least not in the short term. Today we can offer them a complete dynamic driving chassis. In contrast to traditional OEMs, who usually hire multiple suppliers for the drivetrain and chassis, start-ups would benefit from obtaining the base vehicle from one source and then concentrating on the various additional pieces of equipment as well as sales. This close relationship with start-ups or IT companies would have the added benefit of giving us early insights into their strategic focuses. These new market players especially are in a position to bring about a paradigm shift through their innovative technologies.

And how do the components benefit from this game?

Vogt: A deep understanding of the system also furthers the development of its components. We have the ability to design parts in a less complex manner, and in doing so, make them more competitive. For example, we don’t need individual sensors built into single components when the information can be obtained just as well from somewhere else in the system. Component development must also meet the demands of autonomous driving – we need a new understanding of fail safety, for example.

And what would this entail?

Vogt: A good example of this is steering – if the power-assisted steering fails, you still have the ability to steer the vehicle, you just need to turn the wheel with a bit more muscle. A computer-operated vehicle that drives autonomously could no longer be controlled at all, however. Which means redundancy would need to be built into certain features. The most expensive version would be to have everything twice. Systems expertise supports us in developing appropriate redundancies. For example, an autonomous vehicle whose front-axle steering has failed could still be guided to a safe stop on the side of the road via rear-axle steering and brakes.

Our knowledge when it comes to components enhances our integration know-how or makes it possible in the first place.

Dominik Vogt, ZF development engineer

Staying on the subject of autonomous driving: how are you dealing with the increasing complexity?

Lovell: In principle, we work with the same system architecture here as we do with the Integral Chassis Control – here driver assistance systems define a trajectory, a corridor, which represents the vehicle’s desired path of movement. Our ICC then calculates which actuators need to take action, and how, in order to carry out the driving tasks. It interacts with the assistance systems, providing information from a variety of different sensor sources about the physical limits within which the vehicle is currently moving.In general, this could also be carried out within a system in which the trajectory isn’t defined by different assistance systems, but instead by a high-performance computer with artificial intelligence – and we are currently working on such an experimental vehicle.

The Component: Active Kinematics Control (AKC)

An actuator unit integrated into the rear axle electromechanically adjusts axle kinematics based on the driving situation. As a result, the toe angle can vary by plus or minus five degrees and more – meaning the rear axle steers too. A control software combines this significant, additional steering adjustment with the front axle’s steering activity. The result is a clearly noticeable, positive impact on the vehicle’s handling.

The System: Integral Chassis Control (ICC)

The ZF software connects all of the assistance systems that have an impact on driving dynamics via defined interfaces – similar to how a PC can be connected to a variety of peripheral devices via USB. When advanced driver-assistance systems (ADAS) – such as emergency braking and collision avoidance systems – take action in critical driving situations, ICC ensures that they don’t “step on each other’s toes” when taking control of the vehicle’s steering and brakes. The ICC operates between the ADAS and the actuators and transmits the calculated planned course of movement to each actuator that can actually implement it. Despite not adding any additional hardware to the vehicle’s steering, brake system, or chassis, the vehicle operates significantly more safely and more agile thanks to the integrated control software alone. This higher-level control software can also be integrated into the ZF ProAI, the control box that ZF developed together with chip manufacturer Nvidia. Thanks to high-performance computing, it brings artificial intelligence and deep learning to the automobile.