Stowable steering column for the car of the future

Autonomous driving functions will revolutionize driving as we know it today. For developers in the automotive industry, this megatrend means entirely new challenges, especially in terms of interior design. One player actively shaping the change is thyssenkrupp Steering. With the stowable steering column, the steering expert enables its customers in the automotive industry to create completely new interior concepts. And not just for autonomous driving.

A premium German automaker has made a start: Its new luxury sedan will be certified for highly automated driving to Level 3 of the renowned SAE ("Society of Automotive Engineers") at speeds of up to 130 km/h. It is a decisive step toward the fully autonomously driving automobile. Other levels will follow. Initially, Level 4, in which drivers can completely relinquish control of the vehicle and become passengers while the vehicle drives certain routes completely independently. Further in the future lies autonomous driving according to SAE level 5. Here, the vehicle takes over all tasks automatically, and the passengers can sit back and relax.

New vehicle concepts call for new steering systems

But even the SAE 3 and 4 automation levels will require new vehicle concepts that will have a significant impact on the steering system of the future, and make new steering functions possible or even necessary. As one of the world's biggest manufacturers of steering systems, thyssenkrupp Steering is right in the middle of it all. One particularly exciting innovation that the steering specialists are working on is the stowable steering column (SSC).

A system that is of utmost importance to the expert in the field of steering columns, as Gerhard Waibel emphasizes. "We recognized the potential of adjustable or even completely stowable steering columns very early on, and have been developing corresponding systems since 2016," says the overall head of preliminary and application development for steering columns at thyssenkrupp Steering. "The topic has gained significant momentum with the strong push for automated driving as well as the need for new interior concepts." The first concepts were presented at the IAA in Frankfurt in 2017, and later at the North American International Auto Show (NAIAS) in Detroit. Waibel and his team also further developed the systems in several development cooperations together with leading automotive manufacturers (OEMs). All systems are compatible with steer-by-wire technology, which does not require a mechanical connection between the steering wheel and the steered wheels, and in which the steering commands are transmitted exclusively electrically to the electromechanical actuator.

Innovative steering column concepts for the car of the future

For Level 3 of automated driving, the steering specialists have developed the so-called "Extended Steering Column" (ESC), an adjustable steering column. "With this system, drivers can have the steering wheel move forward electrically toward the engine compartment," explains Daniel Kreutz. As team leader in Gerhard Waibel's department, the engineer is responsible for the development of the stowable steering column and the standardization of electrically adjustable steering column components. "The steering wheel is still fully accessible and fully rotatable in this situation," Kreutz added.

While drivers can reach the steering wheel at any time by leaning forward if necessary, the completely stowable steering column is the logical further development. Kreutz: "With the SSC, the steering wheel moves forward by up to 250 mm, depending on the vehicle architecture, and can be stowed completely in the cockpit, depending on requirements. We then see this solution mainly for Level 4 vehicles, which are highly automated." Since 2016, thyssenkrupp Steering has developed several solutions that have been tested in driving simulators and demonstrators as well as in test vehicles.

Autonomous and automated driving: vehicle interior gains considerable importance

With automated and autonomous driving, vehicle interiors are becoming enormously important. After all, if you no longer have to keep an eye on the traffic all the time and do not need to drive the vehicle, you have more opportunities to do other things. Comfort and entertainment features take center stage. Adjustable and stowable steering columns are then central elements that make new interior architectures possible. Daniel Kreutz: "In the future, during autonomous driving, drivers will have the option of positioning the steering wheel further forward, so they'll have much more space available as a driver." Space, for example, to work at a desk that extends from the dashboard. Or for front seats that swivel.

With electric mobility, Daniel Kreutz brings another, initially surprising area into play: "Even when I am parking my vehicle, or charging my electric car at the charging station, these new interior concepts allow me as a driver to have more space and make better use of my time."

Great challenges – ingenious solutions

The steering specialists at thyssenkrupp Steering had to overcome numerous challenges to develop the revolutionary steering column systems. One issue during predevelopment, for example, was the adjustment speed. "With conventional steering columns, we are talking about adjustment speeds of 10 to 12 mm/s," says Gerhard Waibel. However, the adjustment speed requirements for the ESC and SSC are significantly higher. "Here we had to significantly increase the speeds in the drives. With the stowable steering column, we are talking about speeds of 40 to 60 mm/s. And such adjustment drives did not even exist on the market until then. So we've been heavily involved in developing solutions that can deliver these speed ranges."

Another challenge is the limited installation space. "There is relatively significant demand for installation space in the front area of vehicles," Gerhard Waibel reveals. "We can't afford to take up too much space." In order to be able to realize large adjustment travels of up to 250 mm in a installation space-saving way, the developers therefore designed multiple telescoping variants. "With the kit we developed, we also have the option of using a second telescope for the adjustment. Such a double telescope does not yet exist in series production today." This unique technology has been patented by thyssenkrupp Steering.

Decisive advantages over the competition

"With our telescopic solution, we have a decisive advantage. This is because others require concepts with up to three drives for the same functions. We only need two and thus have cost advantages. We also have advantages in terms of stiffnesses, natural frequency behavior and, above all, adjustment speeds." The safety requirements for a safety-relevant component such as the steering column are also extensive. Both ESC and SSC must meet stricter functional safety requirements due to their higher functionality. For certain functions, the systems meet the highest safety requirements.

Game-changer software

"For our part, we have to ensure that errors are reliably diagnosed and avoided," Gerhard Waibel reports. "In terms of integrating our system into the vehicle, there are several ways to do this. On the one hand, we can connect our system via the existing vehicle software, for example. On the other hand, we can also offer our customers the complete package, which includes the ESC or SSC steering column, the electronics, the actuators and also the software." The software is programmed at the company's own software and development center for steering technology in Budapest. Here, with more than 1,000 employees, the company combines the complete software development for electromechanical steering systems and develops, among other things, new software functions for improved driving safety.

But the software used is not only of elementary importance for the driving function and safety. It is also becoming a game changer in terms of aftersales service: "On the electronics and software side, we will have the advantage in the future of being able to change functionalities with over-the-air updates," explains Daniel Kreutz. "This will allow us to respond to changing regulatory approvals and, for example, approve a complete stowage of the steering wheel for a Level 4 vehicle."

What sounds a bit like science fiction is not that far away from being ready for the market. "Today, there is still no stowable steering column in series production. We could see the first series solutions as early as 2024/2025," says Daniel Kreutz. "We are still in the predevelopment stage, but we are in discussions and also already have series production inquiries."