For some time, electric power steering (EPS) has dominated the mass-market in a number of major car-producing regions, helped by its ability to improve fuel economy and save designers valuable space.  Continuing just-auto's series of interviews with global components manufacturers, Matthew Beecham talked with engineers at TRW Automotive about the latest generation EPS, active front steering (AFS) and steer-by-wire systems.

Generally speaking, in the early days of EPS the system had its faults.  How does the latest generation EPS compare and what could we expect?

The performance, robustness and the feature sets offered by today's electrically powered steering systems have shown great progress. The "on-centre" steering feel issue has long since been overcome in the opinion of vehicle manufacturers and the enthusiast press, moreover, the feel of the hydraulically assisted rack and pinion steering systems that drivers had become accustomed to has been replicated.

TRW is into its third generation of both column drive and belt drive systems (also known as rack drive) and with each successive generation we are working toward greater levels of functionality and reliability. As with any technology there are challenges in the early stages as you tune the successive generations, but we are building on a solid knowledge base and delivering the features desired, such as enabling semi-automatic park assist, wind drift compensation, compensation for road surface irregularities, etc.

OEMs talk about 'steering feel'.  Can it be tuned depending on the brand?  And if so, what needs to happen to achieve that?

This is one of the big advantages of electric steering over conventional hydraulic power steering. You can effectively tune to the characteristics of a brand and deliver differing steering feel in line with a vehicle manufacturer's 'DNA', depending on the characteristics desired for a particular vehicle. And it is much easier to do so through software changes than through tuning the mechanical hardware - you can be testing various steering feels on roadways or a track almost continuously with electric steering to hone in on the desired feel - with hydraulic power steering you have to switch out componentry and do much more vehicle level testing which adds time and cost.

And with electric steering you can more easily deliver variable assist steering - high assist at low speeds for parking, for example, and low assist at high speeds for a sportier feel on the motorway.

We are also hearing a lot about the 'autonomous car'.  To what extent can EPS assist such a vehicle? And what other areas need to be developed in order to achieve it?

Electric steering can also pay big dividends in this regard. By their nature autonomous or even semi-autonomous driving will need to have all major systems electronically controlled in order to give the proper commands to get the vehicle from point A to point B. Full steer-by-wire systems could provide some advantage in an autonomous vehicle, but it may not be necessary to go to full steer-by-wire to get the desired performance.

Steer-by-wire systems have also been talked about for years.  But there are signs that they are about to become a reality.  What's your view on its prospects?

Nissan has just launched the first production steer-by-wire on the Infiniti Q50 sedan. They call it Direct Adaptive Steering and it is now available in showrooms. However, most vehicle manufacturers still feel the technology may be cost prohibitive and challenging in terms of the power requirements. And you must also have a robust solution for fault tolerance and electrical failure to allow drivers to steer in such emergencies. The interim electric power steering solution looks to be the path for at least the near term.

To what extent does active front steering (AFS) influence driving performance?

Active Front Steering was developed and launched by BMW in 2003.  The system can assist drivers in enhancing the performance of situations like tight parking manoeuvres in which the steering angle can be sensed and less turning of the steering wheel is required to complete the manoeuvre. It can also assist in helping to reduce understeer and oversteer situations in cornering by measuring actual steering angle versus driver intent and actively correcting the angle.

AFS is said to make steering more comfortable and safer.  Yet do you think that such steering technology and associated systems will become a necessity rather than a luxury?

This is most likely dependent of the ability to bring down the associated costs of the system. It is difficult to see how this technology will migrate to smaller, cost sensitive vehicle markets in the near term.

EPS has followed a growth path over the past decade, gradually permeating across all vehicle segments.  What are its continued prospects for its application in emerging markets?

Electric power steering is growing rapidly across all regions - in part due to the growing trend of global platforms where vehicle manufacturers are replicating models in each region where they have assembly plants. However, it is not limited to this phenomenon. In China, TRW has launched EPS column drive on several China domestic platforms and this number continues to grow. Brazil is also seeing the introduction of EPS and it is only a matter of time before this growth occurs with manufacturers in India and elsewhere.

In terms of EPS technologies fitted to passenger cars, is there a dominant technology emerging (i.e. rack drive EPS) or does it depend on the vehicle application?

The remainder of this interview is available on just-auto's QUBE research service