Ford-Werke GmbH on Suspension Systems

Automotive IQ interviewed Dr. Thomas Schmitz from Ford-Werke GmbH on the topics suspension systems for AVs, EVs and HEVs.

Dear Dr. Schmitz, could you provide us a quick insight into the topic you are presenting on?

We will show a paper which deals with the optimization of suspension systems and components. Tailored analytical models and methods have been developed within our globalCAE group. The application of these tools to critical loadcases which were collected from real world experience will be presented.

In addition it will be shown how the suspension components will need to be designed in order to address the lessons learned.

With AVs, EVs and HEVs coming in a big way, what are the major challenges in integrating suspension systems for these vehicles and how can they be overcome?

The biggest challenge we are facing with electric vehicles is to offer the customer the desired driving range. This means the vehicle needs to be packaged around a maximum size battery. This drives the front wheel forward as much as possible and demands a package efficient rear suspension.

Hence new suspension concepts need to be developed. For example, rear wheel drive with a unique geometry and a steering gear in front of the front axle and a five link rear suspension is an interesting architecture for this purpose.

How are the current damping systems evolving and what solutions do you think will provide the best systems in the future?

Passive damper systems have been significantly refined in the last couple of years. With the introduction of new highly tunable valve systems including highly sophisticated features like frequency selective damping or position sensing we seem to approach the physical vehicle dynamics performance limit which is achievable with passive systems. The improvement potential of these kinds of systems is so small that even experts struggle to clearly identify the improvements in blind appraisals.

Improvements are only possible with semi-active systems but even here the performance improvement is relatively small and hence it is very difficult to convince the customer to spend the money for such a feature.

As soon as active suspension systems with a big customer perceived performance improvement compared to passive/semi-active systems including better roll control will be more mature and affordable we may see increased customer acceptance and increased sales.

How do you design a versatile and adaptable architecture? How can you accommodate different wheelbases, tire sizes, powertrain types etc. in the same basic design? What challenges do you face and what are the solutions?

It is clearly obvious that all OEMs are developing new flexible vehicle architectures to be able to derive a lot of new vehicle models manufactured in various regional plants with minimum part complexity.

Key to success is a detailed upfront definition of the architecture constraints and bandwidth: tire sizes, axle loads, track width, wheelbase and powertrain line-up need to be in a reasonable predefined range which must not be significantly changed during the course of the development program. There are many approaches to design a suspension in a way so that it is scalable for various parameters mentioned above. Examples are control arms with variable ball joint positions to scale track or subframes with scalable attachment points.

Also the body interfaces need to be defined upfront so that different suspension types can be exchanged as plug and play elements.

There is a lot of focus on cost and lightweighting, how can both be achieved through design?

It is key to differentiate between weight efficiency and weight buys.

Making systems efficient in terms of weight using conventional materials and smart manufacturing processes has to be the prime strategy. This involves also questioning the historically developed strength and stiffness targets for the respective components. There are many examples where parts made of steel can be designed significantly lighter by deploying optimization methods and creative thinking.

A weight buy on the other hand means spending money for new materials in order to bring the weight down. This is a very expensive approach and should be only used in those cases where a significant weight reduction can be achieved compared to weight efficient designs.

Thank you for your time!