Schaeffler has begun series production of a new mechatronic rear-wheel steering system, bringing enhanced agility on bends and superior inner-city maneuverability to the new electric SUV of a well-known vehicle manufacturer.
Schaeffler comes of age as a provider of mechatronic steering systems with its first rear-wheel steering solution. Photo: Schaeffler (SevenM)
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.
The key to Schaeffler’s new rear-wheel steering system is the planetary roller gear—a 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 optimized for easy vehicle integration.
Planetary roller gear: The technology innovation that sets the Schaeffler rear-wheel steering system apart from the rest. Photo: Schaeffler (SevenM)
Additional 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 rear-wheel steering system consists of two subassemblies. 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.
The system 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 maneuverability.
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.
Second, 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 maneuver, park, and make U-turns in tight inner-city spaces.
Finally, the technology improves the active intervention capabilities of automated lane change assist systems.
Other benefits of the new Schaeffler system include an improved steering feel as well as increased safety and ride comfort.
Thanks to its optimized inner design, our rear-wheel steering system is more compact and requires less installation space in the vehicle. As a result, automakers can save up to 15 percent in weight compared to alternative systems.—Clément Feltz, Head of Chassis business division at Schaeffler
In addition, the whole design of the system has been acoustically optimized, making today’s ultra-quiet electric cars even quieter.