Q&A with Jerry Hardcastle


VDI: Why has the decision been made to put Direct Adaptive Steering into production?

It gives you the opportunity to get even more capability from the steering system. The system has a motor in the steering wheel and two motors on the steering rack. They can communicate with each other incredibly quickly without a mechanical link so it gives us an opportunity to further enhance the performance of the steering system. When you’re driving extremely quickly on an autobahn, it can give you a really good on-center feel and a really good feeling of stability. Then when you get into the city, change the mode and then it goes very light and is easy to park. And using our other technologies like the active lane control, you can use the motors to steer the car. It gives you a platform for even further technology development in the future.

How do you feel about the argument that the more ‘artificial links’ you put between the steering wheel and the wheels, the worse the steering feels for the driver?

Well, you have to experience it. We’re trying to reproduce that kind of steering feel. Even when you’ve got mechanical feel, there are good mechanical feels and bad mechanical feels. With the electronics you can actually reproduce either/or, or even something better. So I think being able to adapt gives you something that you couldn’t get necessarily on the direct mechanical link.

I think there are two schools. One is the purist approach that says, “We’ve done it like this for 100 years so why on earth would you want to change it?” Then there’s the, “Well if we do change it, what could it offer us in the future?” You’ve got that crossover coming now, because this is a foundation towards autonomous behavior of the car. I’m not saying we’re there now – we’re far from it – but it’s very difficult to have very good autonomy when you’re still trying to go through the mechanical linkage. When you remove all that, you remove all the slack in the system. You can recreate that electronically or get rid of it altogether, so it’s a new opportunity – that is the way we see it.

Tell us about the development program to get the system to the point where it’s production ready.

The control system part of it started in our research center. Then it moved into our advanced technology center, where we created a mule to actually develop it before it was presented to the product planners – not just in Japan, but also in the USA, China and Europe – around five years ago, posing the question, “Is this a technology we could sell to the customer?” Then it was decided which car would get it first. I think that because the Q50 is a rather dynamic car, it’s the right one to launch it on. (Pictured below)

From there it went into the vehicle development. It was put onto a modified, wider G37 platform about four years ago to be driven on the proving grounds, on the public roads in Japan, Germany and in the USA. For the two years up to launch, the cars were driven on the Hokkaido proving ground, with our engineers from Europe, the USA and Japan tuning the system to get the correct ‘mechanical’ feel.

The Japanese preference is for a very light steering system. In Europe, we want good on-center feel, a bit heavier, but the risk is when we do that too much on a sports vehicle then we lose parking ability, we lose the ease around town. So we have been tuning these maps to make sure that it feels right in all situations.

From a European point of view, the car came over to IDIADA, where we did all of the safety tests, elk tests and avoidance maneuvers. From there it went onto our graduation course: we’ve got routes centered around the Bonn office – on the autobahn, on winding country roads, in the city and on cobblestones – to actually prove that the technology is working. All of that has been going on in the last three years.

Is the steering tuned the same for all markets?

It is at the moment, but clearly it can be customizable. Beyond introducing this system, we’ve been trying to define what an Infiniti should feel like. There are some differences between markets, but there are elements of security and comfort that apply everywhere – in China, Europe and in the USA and in Japan. The Sport mode is pretty much tuned for the European market and to some extent the USA, but I think it will be rather too sporty for the average Japanese or Chinese customer. So being able to have Snow/Eco/Standard/Sport means that we don’t need a different tuning in every market. ‘Standard’ can be used anywhere and Sport is really what we imagine the enthusiastic European driver will select.

Because you were trying to establish that feeling, does that mean that there was more subjective input to the steering this time than there might otherwise have been in a regular system?

I think there has always been a lot of input but not always a lot of opportunity to change things. When it’s mechanical, it’s developed once and then it’s pretty much fixed by the size of the pumps and the gears you’ve got. The engineers might all agree they want to change it but they can’t. With an electrical system, they can agree to change it and change it. I think there’s been more activity from that viewpoint.

Tell us about the failure modes and back-up.

There’s a mechanical clutch in the steering column. While the system is working perfectly, that clutch is open and you’ve got the electronic communication. But it’s being controlled by three ECUs. They are monitoring the motors and if any one of those three ECUs detects an issue, then it reverts to mechanical mode. It’s a triple layer of safety, so it’s incredibly safe. In the event of a problem, it will revert to a mechanical system and you will continue to drive – you don’t lose power steering, you just have a mechanical link between the two motors, rather than an electronic link.

What about the base rack?

There are two motors mounted in the rack, one at each end instead of a single one. The motor in the [steering]wheel talks to those two [rack]motors, giving feedback from what the driver wants but also receiving road-surface. Using the electronics we’ve dialed out the kickback you get from incredibly bumpy road surfaces.

Do you have any concerns around consumer perception of steer-by-wire? Are you worried about what happens in terms of a failure?

I think when you bring any new technology to the market, you’ve got to be conscious of what the customer thinks. I think we’ve got a job to do in terms of telling the story, introducing it, but also demonstrating how good it is. I think this triple layer of ECUs certainly gives us the confidence. We wouldn’t bring a technology to the market if we weren’t confident in it, for sure. I ride a motorcycle and I’m interested in motorcycle controls and the first time motorcycles introduced anti-lock braking and then traction control and things like that, everybody said, “Oh I don’t need that on a motorcycle.” Now you’ve got ride-by-wire, throttle-by-wire. I think once you experience it and see what it can do for you, certainly in terms of the kickback stuff, I’m sure that the customers will be convinced.

Why was the rear-wheel steer dropped from the new Q50?

I wouldn’t say it’s dropped forever, but it’s not introduced at this stage. There will be a decision as to whether we decide to introduce it on future performance models and things like that. It’s a technology that can be applied or not applied; it gives a different stability. We’ve tightened up the suspension on this car as well and the chassis is stiffer. When you improve the base stiffness then you don’t necessarily need all the technologies at a certain performance level. When you start to push the performance envelope again, then that technology is there, should we need it to further enhance [the product]and its capability.

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About Author


Graham Heeps is a regular contributor, and knows the dynamics industry well, having previously edited the title. Graham also writes regularly on automotive and motorsport subjects for other magazines from Vehicle Dynamics International’s publisher, UKi Media & Events (as well as editing Tire Technology International), and contributes to a range of online and print publications in the UK, USA and Canada.

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