Steer-by-wire is the next big thing - and this is why we need it

I hate to break it to anybody already ruing the demise of throttle cables and hydraulic brake lines, but the steering column is the next bit of connective mechanical tissue up for the chop. I interrupted our recent road test of the invigorating new Toyota Aygo X to join some ZF engineers at MIRA. They were in a modified G30 5 Series (with rare cloth seats - how delicious). Fitted to the car was a new steer-by-wire system already serving in Nio's Chinese-market ET9 but due to appear in at least one senior Mercedes next year. It captures the driver's inputs with a steering wheel actuator, which then informs another mechatronic actuator on the front axle, turning the wheels the desired amount. In reciprocation, torque sensors on the axle send a signal back to the steering wheel module. There that signal is translated into force by two worm drives that work independently around a single worm wheel, recreating load and, yes, even granular feedback. It's simple but, as ever, stupidly clever. It's the second drive, which acts with or against its twin, that's especially neat. You may wonder why we need this technology. There are good reasons, according to ZF ride and handling specialist Duncan Church and his colleague Adam Heenan, an expert in active vehicle systems. Both engineers have worked in steering since the advent of electromechanical (EPAS) systems and insist that the by-wire approach isn't a fresh start but something that builds on more than a decade of EPAS learnings. They reckon that, because of the way in which these systems work, when it comes to what can loosely be defined as feel, there's actually a smaller difference between EPAS and by-wire than exists between fully hydraulic and EPAS. Crash safety is a big benefit. No intermediate shaft (as engineers call the column) waiting to be rammed back into the cabin in an accident is a good thing. With no physical connection between front axle and steering wheel, by-wire systems also remove the potential for thumb-snapping kickback. Equally, they can nullify undesirable kickback in normal driving. Massively adaptive ratios are another reason why car makers are courting steer-by-wire. Cars are getting bigger and cities busier. Having a quick ratio at low speeds and a more languid one on open roads is clearly useful. It could change with a car's drive modes too. Delicate calibration of this stuff will be essential, of course, but this kind of versatility isn't really possible with EPAS. Your SUV could serve up 180deg lock to lock. With by-wire you can also fold or even stow the steering wheel in the dash - useful for sleeping in a 4x4, or if your car is one day driving itself. The wheel won't whip this way and that during automated parking, too-instead neatly remaining 'dormant. Steering columns also transmit noise and vibration into the cabin; car makers have got good at mitigating this but the ability to totally nullify will undoubtedly please S-Class engineers. On a similar note, far fewer engineering compromises will need to be made to change the side of the steering wheel by market. Vehicle assembly is also simpler. And you can, of course, use the same hardware with a different state of tune for a vast variety of applications, so there are obvious economies for the modern manufacturer haemorrhaging cash. So what does it feel like? The G30? Beautifully balanced, as ever. And the steering? Actually, surprisingly intuitive. Church and Heenan allowed me to try a 'Comfort' map. I wouldn't want it on my weekend McLaren but, for the purposes of an everyday car, it was perfectly accurate and judiciously weighted. Nothing at all screamed 'video game controller'. Crucially, the initial response was intuitive and pretty natural. From his laptop, Heenan then summoned up a sportier map - one with similar weight to before but more road-surface feedback. The difference was subtle but subtle was all that was needed. The faintly thin two-dimensionality of the Comfort map was more or less addressed and there was enough information - gathered at ground level and conveyed faithfully yet digitally to my hands - for me to confidently carve through damp off-camber bends at pace and lean on the car. I'd say it was 90% convincing - which, given the beigeness of most EPAS, is all it needs to be.

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Steer-by-wire is the next big thing - and this is why we need it

ZF’s latest steer-by-wire prototype shows us how radical new tech improves safety and driveability

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