Infiniti goes steer by wire
PH investigates Infiniti's move to be the first with entirely 'digital' steering
It calls the system Direct Adaptive Steering. The initial research phase began some 15 years ago, according to chassis engineer Takeshi Kimura. “DAS replaces the mechanical linkage with an electronic linkage,” he says. “We have a steering rack with two motors, which we call steering angle actuators. There is a steering column with one motor, called the steering force actuator.
Mechanical fail-safe is only link to front wheels
The benefits, reckons Kimura, are manifold, but it’s speed of response that is most significant. “On a conventional system the torsional compliance of the steering shaft and of the steering gear mounts means there is a delay between turning the steering wheel and the front wheels actually turning,” he explains. “The DAS system doesn’t have that compliance, so the response is much faster.”
Beyond speed of response, the system also has the same fuel efficiency benefits as ePAS compared to hydraulically-assisted power steering and it can reduce steering input in a similar manner to a rear-wheel steering system. It also filters out unwanted noise and kickback from rough road surfaces, which is reckoned to improve refinement, and additionally it facilitates such functions as lane departure warning.
Although it’s technically possible to engineer an autonomous counter steering – or opposite lock – function alongside DAS, modern electronic stability programmes effectively negate the need.
As yet there isn’t a weight saving. In fact, there is a weight penalty because a mechanical rack and pinion system, actuated by a clutch, is still fitted as a failsafe. Kimura hopes to be able to eliminate the back-up system in time, however, which would bring significant benefits in terms of packaging and safety; there’d no longer be a large pin pointing as your chest, as he points out.
The main drawback, however – and it’s one that keen drivers may never accept –is that the steering just feels bizarre. The weighting seems inconsistent and changes mid-corner, and you never really trust that the artificial feedback is accurate or reliable.
The relentless move towards ePAS shows that manufacturers have greater concerns than the tactile preferences of a core group of motoring enthusiasts, so is steer-by-wire a reality that we’ll just have to accept? Infiniti will be charging ahead with it; “We believe DAS is the future,” says Fintan Knight, regional Vice President of Infiniti.
“As engineers we want to use the system on all of our cars. We are discussing the implementation of DAS right now,” confirms Kimura.
“Other manufacturers have looked at steer-by-wire, but they gave up because of the difficulties. After driving our car I think it is possible they will be encouraged to develop their own systems.”
The benefits of DAS are genuine and once the mechanical failsafe can be eliminated they’ll be greater still. As it is now, however, steer-by-wire isn’t close to replicating the tactile pleasure of a good hydraulic setup.
What's next, xbox style rumble feature built in?
Seems car makers are continuing to refine vehicles then artificially add 'charachter' back in
Steering feel should improve no end, if simulators can manage it I see no reason why a digital system being fed real data can't. But it still doesn't get around the ultimate question here which is why bother?
Odd, very odd.
Electrical steering is happening, and we have to accept that. However, if we reward manufacturers who put an emphasis on making electrical steering work well, by buying their products instead of just giving up and settling for whatever's out there, then it will improve more quickly.
At least it's not like manual vs paddles - it's not an either/or. We can demand both faster/more economical steering, and, hopefully with a bit of development, still keep the feel.
k knows how bad this would be though.
Steering feel should improve no end, if simulators can manage it I see no reason why a digital system being fed real data can't. But it still doesn't get around the ultimate question here which is why bother?
Odd, very odd.
The 'why bother' is answered upon that point being reached:
- Weight - obvious removed componentry aside, I imagine the bulkhead would require a lot lees bracing/stiffening for an electic system
- Occupant safety - again, pretty obvious
- Packaging - freed from having to work round an immovable metal spear in the middle of the vehicle, interiors should become cheaper and easier to be made in more flexible arrangements
- Regionalisation - LHD to/from RHD becomes a lot easier
- Cost - commoditisation of steering parts, easier and quicker development
This is a step too far IMPO
Cheers
MC
The results of a failure at high speed don't bear thinking about.
The results of a failure at high speed don't bear thinking about.
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