Schaeffler rear-wheel steering system goes into series production 

The new mechatronic rear-wheel steering system by Schaeffler has celebrated its series-production premiere, bringing enhanced agility on bends and superior inner-city manoeuvrability to the new electric SUV of a global vehicle manufacturer.

By adding steering functionality to the rear axle, Schaeffler’s new technology improves handling in city traffic, enhances lane-change stability, and makes the vehicle easier to park. “Schaeffler has developed from a supplier of components for chassis systems to a provider of complete steering systems,” said Matthias Zink, CEO Automotive Technologies at Schaeffler AG. “We have built up extensive capabilities around steering systems in recent years because we see this as a strategic growth area for our business.”

The key to Schaeffler’s new rear-wheel steering system is the planetary roller gear – a world-first based on precision mechanical engineering from the company’s in-house industrial technology operations. The result is a highly compact system that is lightweight, quiet in operation, and optimised for easy vehicle integration.

According to Schaeffler, this innovative steering system has been well received by the market, with the first customer onboard and various other auto makers likewise committed to using it in their vehicles. In fact, further vehicle models featuring the steering system by Schaeffler are due to go into production before the end of 2023 as well as in 2024.

Schaeffler’s innovative product is the world’s first rear-wheel steering system with planetary roller gear. Photo: Schaeffler (Daniel Karmann).

Innovative planetary roller gear
Schaeffler’s rear-wheel steering system consists of two sub-assemblies. The first – and the key to it all – is a precision mechanical system featuring a planetary roller gear from the company’s Industrial division that has been specifically adapted for automotive applications. The second is the powerpack, comprising the electronics, electric motor, and software. Schaeffler develops the overall system and takes care of its integration into the customer’s vehicles. 

The planetary roller gear sets the Schaeffler system apart from rear-wheel steering systems made by other manufacturers, which traditionally use trapezoidal screw drives. Consequently, the Schaeffler product not only meets the stringent safety standards of Automotive Safety Integrity Level D (ASIL D), but it also yields significantly increased efficiency, reduced friction, and shorter system reaction times. This allows Schaeffler to generate a precise as well as save vehicle motion. This is especially advantageous for drivers of electric vehicles because it compensates for the downsides of the longer wheelbase necessitated by the underfloor battery position common in such vehicles. A longer wheelbase means a larger turning radius and hence reduced manoeuvrability.

The Schaeffler rear-wheel steering system overcomes this problem in a number of ways. First, when the vehicle is changing lanes at higher speeds, the system turns the rear wheels in the same steering direction as the front wheels, enhancing stability, handling, and safety. Secondly, on tight bends, the system improves vehicle agility by turning the rear wheels in the opposite steering direction to the front wheels. This creates a virtual reduction in wheelbase, enabling the driver to steer through the bend with ease. In the same way, the system also reduces the vehicle’s turning radius, making it much easier to manoeuvre, park, and make U-turns in tight inner-city spaces. And finally, the technology improves the active intervention capabilities of automated lane change assist systems.

Lighter, smaller, quieter
Other benefits of the new Schaeffler system include an improved steering feel as well as increased safety and ride comfort. “Thanks to its optimised inner design, our rear-wheel steering system is more compact and requires less installation space in the vehicle,” said Clément Feltz, Head of Chassis business division at Schaeffler. “As a result, automakers can save up to 15 percent in weight compared to alternative systems.”

In addition, the whole design of the system has been acoustically optimised, making today’s ultra-quiet electric cars even quieter. Schaeffler will be exhibiting the new product and its latest portfolio at the 2023 IAA Mobility show in Munich, which opens on September 5.