Assisted & AD Enablers, Innovation, Software September 28, 2022

How Steer-by-Wire’s Dynamic Variable Steering Ratio Adds Comfort & Control for Future Mobility

Steer-by-Wire (SbW) is a game-changing steering solution because it enables advanced safety, convenience and comfort features for drivers – one of which is Dynamic Variable Steering Ratio. Dynamic Variable Steering Ratio is a software feature within a SbW system that allows automakers to tailor vehicles’ responsiveness.

Dynamic Variable Steering Ratio for Driver Comfort

Through Dynamic Variable Steering Ratio, vehicles can automatically adjust how much a driver has to turn his steering wheel to maneuver the vehicle in different driving situations and vehicle speeds.  This is accomplished by changing the steering ratio to best fit the driving situation.  A faster ratio kicks in at lower speeds, requiring fewer turns of the steering wheel (a.k.a., less steering input for sharp turns), and a slower, more traditional ratio is used at freeway speeds.

With current steering systems, drivers often must turn the steering wheel more than a full revolution to make sharp turns at low speeds – for example when turning a 90-degree corner in a residential neighborhood, maneuvering into a parking spot or making a hairpin turn around a median.  This requires repositioning the hands on the steering wheel – the classic “hand over hand” maneuver.

SbW’s Dynamic Variable Steering Ratio can enable drivers to complete these same low-speed maneuvers while only turning the steering wheel a moderate amount, less than half a rotation to the left or to the right.  This creates a highly satisfying and comfortable engagement between driver and vehicle – eliminating the need to reposition the hands on the steering wheel during turning maneuvers.

In addition, Dynamic Variable Steering Ratio can open new possibilities for drivers with limited mobility who may have no trouble making gentle turns at high speeds but can’t complete hand-over-hand maneuvers for tighter turns.

Empowering Future Design

While Dynamic Variable Steering Ratio will be valuable for vehicles with traditional steering wheels, it can also help support future steering wheel solutions. Yoke steering wheels, or those that have a sideways oblong shape (like a yoke in an airplane), are becoming more popular in prototypes and have been featured in some vehicles on the road today. They’re designed to enable drivers to easily view gauge clusters over the wheel, increase space for the knees and may eventually fit into dashboards through technology like Stowable Steering Columns. However, they come with some challenges too.

According to Consumer Reports, a big issue of yoke steering wheels is making sharp turns. Traditional hand-over-hand steering and shuffle steering are difficult or impossible with a yoke, as there is no handle at the top of the yoke to hold. While some hand-over-hand steering is still possible, it is more difficult to grab the yoke without taking your eyes off the road due to their inconsistent shape – part of the yoke that was there at the beginning of the turn may have rotated away, leaving drivers with an empty space.

Dynamic Variable Steering Ratio can help support this new steering wheel technology because it doesn’t require drivers to take their hands off the yoke or slide them along the yoke while turning during lower-speed, sharper turns.

In our industry, technology is advancing rapidly as we move toward future mobility solutions. Innovations are becoming increasingly intertwined, and Nexteer’s Steer-by-Wire with Dynamic Variable Steering Ratio is one more piece of the puzzle that we offer to support this evolution.

Alan Davis
Alan Davis is Nexteer’s Product Line and Engineering Director for Steer-by-Wire. He is responsible for the SbW product by setting product development priorities in line with OEM needs and new business pursuits.