Nexteer Readies Advanced Steering Tech
Electric power steering systems have come a long way in a short time. The technology, which debuted 20 years ago, now is fitted on virtually every new car and light truck.
The reason is simple: EPS can boost fuel efficiency by as much as 6% over previous hydraulic-based power steering-assist systems.
Safety Building Block
In recent years, other benefits have materialized that are making EPS a key enabling technology for next-generation steering systems.
The technology already is being used in emerging advanced driver-assistance systems (ADAS), such as lane-keeping assist, parking aids and traffic-jam assist, notes Jeff Zuraski, executive director of research and development for Nexteer Automotive.
The Michigan-based supplier, which pioneered the technology in 1999, makes about 10 million EPS units per year. Now the company is preparing for the next level, including long-awaited steer-by-wire systems, emergency steering, integrated braking and fully autonomous vehicle support.
Steer by Wire
With steer-by-wire, the mechanical connection between the steering wheel and road wheels is replaced with electronics and actuators on the steering column and rack.
The setup promises to enhance safety and performance capabilities, reduce weight and improve packaging flexibility. Engineers have been developing the technology for decades, but cost, reliability and consumer acceptance issues have thwarted commercialization efforts.
Nexteer steer-by-wire. (Image: Nexteer)
Nexteer, however, has high hopes for steer-by-wire systems, which the company shorthands as SbW. Zuraski points to more sophisticated software algorithms and other technical advances that he says now make the technology feasible.
This includes the use of more advanced sensors and improved safety redundancies, including backup microprocessors.
Part of the challenge for SbW has been how to convey the same road feedback with the electronic system that drivers get with a mechanical system, Zuraski says.
Drivers need to quickly discern changes in road conditions, such as the differences between driving on dry and wet pavement, so they can make the necessary driving adjustments to optimize safety. “The feel has to be right or drivers won’t accept it,” Zuraski says.
Nexteer’s latest SbW technology uses ADAS sensors to monitor road conditions. The system then emulates the “feel of the road” back to the driver through torque feedback on the steering wheel generated by a small motor added to the column and steering wheel assembly.
The rapid growth of EPS and ADAS in recent years has helped bring costs down.
The next step is to add features and functionality, which Zuraski says will help drive SbW’s value. Among the next-generation systems Nexteer is developing are:
- Programmable steering ratios
- Automatic emergency steering
- Integrated braking functions
A handful of vehicles currently use variable steering ratios based on vehicle speed to enable greater maneuverability at low speeds and enhanced stability at higher speeds. SbW makes this easier to do and could provide a greater performance range—from sporty to luxury—according to Nexteer.
Similar to current automatic emergency braking, emergency steering systems would temporarily take control of a vehicle to prevent an imminent collision. The steering system could be designed to limit emergency maneuvers within a vehicle’s current lane or, working in tandem with other sensors, automatically change lanes if a path is clear.
Emergency steering can be added to current EPS systems. But Zuraski says SbW provides greater benefits because it allows the road wheels to be moved without rotating the steering wheel, thus minimizing counteractive driver inputs.
Nexteer is testing the technology on a demonstration vehicle.
Motion Control Partners
Nexteer also is working with braking specialist Continental on integrated “motion control” systems through their 3-year-old CNXMotion joint venture.
The Grand Blanc, Mich., venture aims to better coordinate braking and steering inputs to enable highly automated driving systems through control and actuator systems. “There is a finite amount of force available at each wheel, integrating the functions enable the best balance between steering and braking forces,” Zuraski says.
The technology wouldn’t require a major redesign, but probably would be installed on a new platform rather than an existing one, according to Zuraski. The system could be used for electrified vehicles as well as conventionally powered models.
Autonomous Vehicle Tech
Nexteer also is developing other systems to help enable the transition between semi- and fully autonomous vehicles.
The company’s Steering on Demand technology automatically retracts the steering wheel when the vehicle is operating in autonomous mode. And its Quiet Wheel system minimizes driver distraction by preventing the steering wheel from rotating.
“We’ve made a lot of progress,” Zuraski says, noting that all of the technologies build on each other.
As for commercialization, he says most of the technologies are ready now. He envisions increased implementation of additional ADAS features in coming years, with SbW and emergency braking systems starting to appear around mid-decade.
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