A unique way to MANOEUVRE

By-wire technology is nothing new in motoring, but would you trust it with your car’s steering? Chris Randall tries it out.

It seems that barely a week goes by without one car-maker or another trumpeting their latest piece of technical or electronic wizardry, which is something that either fills you with excitement or dread depending on how you view such things. However, there’s one piece of engineering technology that seems to have slipped in below the radar of many motorists, which is surprising given that it was touted as a world-first by Japanese manufacturer Infiniti.

The premium badge of automotive giant Nissan, Infiniti has found sales hard to come by since arriving in the UK market, struggling to compete with rival premium marques such as Audi, BMW and Mercedes-benz. In 2013, it announced that its Q50 saloon could be optioned with a rather forward-looking piece of technology. Aside from the widespread adoption of electric assistance to boost efficiency, steering systems haven’t changed a great deal over the decades, but doing away with a mechanical connection between the steering and road wheels was a development of note.

Known as direct adaptive steering (DAS), how does it work? Well, there are three key components. The steering force actuator is located at the top of the steering column; this not only monitors the steering angle and effort applied by the driver so the appropriate movement at the wheels can be made, but also works in reverse to provide a level of feedback at the steering wheel. With the actuator informing the electronic control unit (ECU) of the driver’s intended actions, the ECU generates a signal that is sent to the pair of steering angle actuators at the variable-ratio rack which move the road wheels as appropriate.

The steering angle actuators – which comprise a main and sub actuator, both of which contain a motor, reduction gear and sensors measuring parameters such as angle and torque – are also responsible for sending signals back to the steering force actuator, in theory allowing the driver to feel what’s happening at the wheels in much the same way as they would using a conventional steering arrangement. It also means that steering effort can be electronically increased with speed and lateral G forces, again providing a level of natural feel.

Quick thinking

The system is capable of making up to 1000 adjustments to the steering every second, but, as Infiniti points out, that feedback is ‘filtered’ by the electronics so that DAS allows less vibration and kickback from the road surface to reach the steering wheel, thereby increasing refinement and reducing driver fatigue, while also removing the corrupting effects of torque steer. That’s the theory anyway, although not everyone is convinced. A number of motoring journalists have criticised the system for unpredictable changes in steering weight and lack of natural feedback.

Undeterred, Infiniti has pressed ahead with a second-generation system and, following 625,000 miles of testing, says this is the most advanced version yet. Sold as something of a precursor to fully autonomous driving – something that a number of car manufacturers are introducing to one degree or another – it’s available on both the latest Q50 model and the recently-introduced Q60 sports coupé.

The new system incorporates a number of developments. The first is a system of selectable modes that enables the driver to alter the way the steering feels and reacts in different driving situations. There are three ‘core’ modes to choose from: Standard, Sport and Sport+. The first of these reduces steering effort and provides slower responses, while selecting Sport quickens the steering ratio for faster response, with Sport+ making it quicker again depending on speed. According to Infiniti, the steering ratio is 4% quicker in Sport and 12% quicker in Sport+ compared to Standard.

The driver can also choose from three levels of steering response: Default, Dynamic and Dynamic+. In all, there are seven combinations of mode, but the company has gone further by integrating DAS into a suite of systems that it calls

PROPILOT Assist, which incorporates features such as intelligent cruise control, blind-spot warning and forward emergency braking, among others.

One of the most interesting is Active Lane Control, which engages automatically above 43.5mph and, using cameras to monitor the car’s position, keeps it in the correct lane – say, on a motorway, – by taking control of DAS and steering the car. It’s a system that some road testers have found distinctly odd as the adjustments to the position within the lane happen without any movement of the steering wheel.

There’s no doubt that this a very advanced piece of technology, and one that’s yet to be offered by any other car-maker, but are drivers really ready to accept such a vital part of their car relying solely on electronics?

Well, by-wire systems have been used by aircraft for many years and, as with those, Infiniti employs multiple back-ups in the form of three ECUS, each monitoring the others and sharing data so that a failure of any one will see another take control. Plus there is a further back up that’s ready to be employed in the event of a complete power failure. Located in the steering column is an electromagnetic clutch that can instantly engage and provide a direct mechanical link to the wheels should the worst happen, thereby allowing the driver to take conventional control.

Aside from the negative response from the press, DAS has proved to be broadly reliable. However, there was a recall of the Q50 saloon in 2016, involving around 60,000 vehicles, to rectify a software glitch. And the UK’S Driver & Vehicle Standards Agency issued a recall in August 2016 for 164 Q50s built between December 2012 and December 2015 to reprogramme the control unit.

Infiniti is clearly convinced that DAS is the way forward, although this hi-tech development has struggled to gain acceptance and it remains to be seen whether it’s something that other car-makers will adopt in the future. A step too far right now? Maybe, but it’s certainly a bold approach, and one for which Infiniti should be applauded.