Nissan's next-generation steering employs a steering angle sensor at the steering wheel, three ECUs for control, electric motors to power the rack, and a steering force actuator near the driver to retain the vehicle's "steering feel."
Greg, the backup is absolutely required. While it is rare, I have been in a car where the power failed and the power steering stopped working. This was a hydralic system, and it was very hard to steer the car, but at least it could be done. Electrical systems are more likely to go out on a car, I would venture to guess, than the purely mechanical ones. Especially electrical systems that are digital.
So let me get this straight, we introduce steer by wire so we can remove the feel of rough roads etc. but we dial in the feel electronically because that wouldn't be good for the driver, and were saving weight even though we added 3 ECU's AND a clutch to re-engage the traditional steering column if all 3 ECU's die (which will happen every time an alternator dies)
I think some engineers in the automotive industry have lost the plot, They're putting complexity in for the sake of it.
Not necessarily. We build airplanes today that are completely dependent on fly-by-wire systems, and would fall right out of the air if those computers were to fail. And making those systems "fail safe" is essentially a solved problem.
On a normal car, the steering column is a major structural limiting factor, driving a large number of constraints for the surrounding vehicle. And it's a big, bulky, complex assembly. Electrically driven steering would make the steering system more modular, more flexible in physical layout, and allow things that are currently not practical, like swapable bodies on common frames, or handing the steering wheel to the passenger without having to pull over or swap seats (anyone remember the GM Hy-X?).
Over the past few decades, we've been steadily finding ways to move complexity from mechanicals to electronics, software, and firmware. It's been demonstrated that this can be done while also increasing reliability and decreasing cost. There's no reason to assume that automobiles are an exception to this.
That having been said, I don't think I'll be lining up to buy the first model year with drive-by-wire steering. :)
"Big, Bulky, and complex"? I think not. The complexity is in the electronics, not the mechanicals. And aircraft have multiple backup systems in their fly by wire systems. I don't see that happening in automobiles unless you want a price tag similar to a 747.
Soooo... You compare 2000 microscopic surface mount components some of which contain a million transistors with 100 mechanical components (guestimate) and say that the electronic version is simpler because the 2000 parts are in only THREE boxes.
I LOVE the Infinity styling but I think they have lost their minds in Tokyo.
Note to Nissan: Give the stylists a raise with the money saved by firing the guys that came up with this Idea.
Right, Rob. For now, the clutch is there, but Nissan told us that if the mechanicals were ever removed, its engineers would incorporate a fail-safe sub-system. At this point however, it's not clear how the fail-safe sub-system would work.
I think the only down side is the number of automobiles on the road. The chances of the system failing are far greater than with cars. You cannot guarantee that the car is professionally maintained. However, if this system is fool proof, I mean that with masses in mind, then it is the future.
I'm going to play teh antagonist here. When it comes to driving, feeling the road is much more important to me than a smooth ride. The feel actually helps me know that a tire has a problem before it is a real problem. I get the whole technology thing for the future, but nothing can replace a solid mechanical system. Removing that is like putting a rocket on the road with no breaks. There always seems to be delay in control system response, and that nanosecond of steering response has saved my life. I embrace technology, but I'm not confident that this is the right way to go.
The basic function of a vehicle is stop/go/turn. That's it! Everything else is bells and whistles. At 60 mph, two things I don't want failing; stop and turn. Survivability goes way down if those systems fail. 'Go' is a snug third. I had a Ford Escort and going through an intersection; there were dips on each side of the intersection as you crossed the intersecting road. The engine stopped running after going through the second dip. I was able to steer to the side of the road and stop; parking legally. The problem was traced to a pin in a connector; the pin broke off at the wire crimp. The whole incident was minor. But if the steering or brakes had been lost things could have been much worse. The car I have now is 'go'-by-wire. The jury is still out on that one but it appears to be hung at the moment.
The steer-by-wire might have a niche market such as applications where a steering wheel is difficult or impractical (example, handicap). When I read these announcements, I pause and give thought what they are saying. Example: Nissan states that '... the advantages are ...'. But they never mention the disadvantages. There are always disadvantages. Red flags: '... the clutch is disengaged 999,999 time out of a million.' If a system is disengaged for that long, what guaranties that it will work when needed? How will you know if the backup has failed? Is it ever tested?
The car is not an airplace and its maintanance does not fall under rigorous training and scrutiny.
When it comes to making it happen without a mechanical back-up, you can count me as one of those skeptical customers, ChasChas. Obviously, though, Nissan agrees with you, not me. Here's what they told me: "The mechanicals are there for driver confidence. In reality, it doesn't need to be there. But in the future, after consumer acceptance of this, the mechanicals could go away, saving us the extra weight." If I fully understood how the back-up system would work in the absence of the mechanicals, I might feel more confident. But they're not explaining that yet.
I can certainly agree that maintenance and proper repair must be concerns relative to this technology. The days of the shade-tree-mechanic are over forever with systems as sophisticated as this one. I think back-up systems are an absolute must until enough reliability data and "road experience" are available.
That's interesting, Chuck. If the redundant system is electronic, than it will have the same vulnerability if the electrical system goes out. I've experienced driving a car when the electricity goes out. The steering becomes more difficult, but you can still steer.
I would hope that the automakers would take into account when the vehicle might run out of fuel which unfortunately occurs quite a lot. At least with a vehicle with a current steering linkage, you can coast to the shoulder with some steering mobility. It would be terrible if your wheels locked in their current orientation and you could not nudge your vehicle out of traffic.
I wouldn't want it. I remember when several other vehicles had problems with the accelerator acting with a mind of it's own. Now we will have to worry about the car going left when you want to go right. Let alone maintenace, something else to break and have the dealer take your arm to pay for it.
You could look at going to a centerstick, side stick system like the X-15 used.
Have the center stick be the computer driven controller but you can reach over and yank on the side stick to get some steering inputs, and if it's over on the side it may package up nicely especially if it only needs a relatively small movement.
The article suggests that S-B-W needs a lot of electrical power. If the end goal is improved fuel economy, a comparison of power required by S-B-W verus hydraulically boosed power steering would be interesting, maybe HP imposed at the crankshaft output. The comparison could include effects of weight of the system components but I speculate that ends up being a minor effect.
From a FMEA perspective there are two requirements. The first is to get to the side of the road safely (high severity). The second is to be able to drive maybe an hour home, to a dealer, or to a town (low-high severity depending on the situation). If the vehicle charging system fails, it sounds like the battery can't support S-B-W for more than a few minutes. So the mechanical backup will always be necessary unless being stranded at the roadside is acceptable from a safety and marketing perspective.
Today I drive a car with mechanical linkage and electric power boost (by chance, also a Nissan). Nissan propose to give me the same, with an extra sensor and wire to the steering mechanism. The electrical signal will be the primary mechanism, but so what? It doesn't replace the existing linkage. Its extra - extra weight, extra power, extra complexity. What happened to "keep it simple" ? Keeping the mechanical linkage in place as a backup is Nissans' way of saying "we like the new system - but we don't fully trust it"
Anyone remember the accelerating Toyotas? I know GM has been working on this for over 20 years. I think it will ultimately come down to consumers and federal mandates (such as CAFE).
The new 787 Dreamliner is entirely electronic. The difference is the rundundant back-ups are not going to exist in the physical sense on cars (weight, weight, weight). So the development in the automobile has to be sensor/control failsafe that stops the vehicle. It is better to get out of the car that is on the side of the road than trying to parachute out of an airplane with type of failsafe!
That is 100% correct. In the aerospace industry there is a massive effort to test and qualify all fly by wire systems to prove that they are fully redundent and fail safe. To incorporate this into a car without a mechanical backup will cause a very complex and expesive system. This is why the aircraft that are relatively inexpesive (single engine puddle jumpers) are still cable and pulley. We may see a day when drive by wire is 100% but I beleive it will be in the high end cars where cost is less of an issue.
I don't get it. All I see is a riduculously complex and expensive system which the owner has to pay for but adds little or nothing useful to the operation of the vehicle.
In my view, you had redundancy and tactile feedback with a rod that connects to the gear that moves the wheels. How much more elegant, cost effective and reliable can you get than that? Seems the weight issue is a materials question, not motors and redundant computers.
I agree, the clutch would be electrical. But for fail-safe, the clutch would have to be held 'disengaged'. Meaning if a power fail occured the clutch releases, in theory. But, this does not cover failures other than power fail.
I agree. Where's the improvement in this? Aircraft control systems use double and triple levels of redundancy and go through years of testing to please the controlling agency (FAA) before they're allowed to go forward.
This almost crosses the line into the catagory "Technology in Desparate Search of a Use", like keyless ignition, voice commands, digital bathroom scales, etc. Maybe Design News can start a new blog of that title to go along with Sherlock Ohms and Made by Monkeys.
First we hear of throttle by wire systems that won't allow heel and toe downshifts and now steering systems that isolate direct steering effort feedback and recreate a subset of the available feel. Its clear during my commute that there are many people that are absolutely ready for the driverless car (cell phone in one hand, cigarrette in the other, what's on the steering wheel?) but for those of who find joy in driving there are dark times coming.
I have had nothing but bad experiences with computer control of everything from turn signals, headlights, antilock brakes and smog control systems in my Chryslers. Why anyone in their right mind would want to drive a car "by wire" is beyond me. It is just a bunch of "Microsoft moments" (blue screen of death) waiting to happen at the worst possible time. I prefer my vehicles have the least amount of "points of failure" as possible.
Add me to the "no" list. I know the system could perform wonderfully, but it could also fail spectacularly. The hydraulic assisted system in use today still operates, albeit with great effort, in the event of a complete hydraulic failure, and steer by wire would not be capable of that.
On most posts this bulletin board leans towards technology at the expense of increased risk. Autonomous vehicles don't frighten most Design News readers, so I'm a little surprised, and encouraged by the negative response to steering by wire.
The reasons in the article for switching to steer by wire are:
1. Elimination of mechanical components (what's the advantage of this, other than weight savings?)
2. Weight savings
3. Elimination of vibration from the road surface (no, you will still feel vibrations, and mechanical steering could be dsigned to "eliminate" vibration, too)
4. Minute adjustment of tire angle to compensate for wind and sloped roads (I suspect that the driver will still have to do at least some of this)
5. Enable drivers to feel the road (we can with a mechanical system)(this conflicts with 3, above)
6. Enable auto manufacturers to readily change the design/configuration of cars (e.g. change a left-hand drive car to a right-hand drive car)
There are other motivations for changing to steer by wire. These may include ease of implementation of driverless cars in the future, or cars that drive themsleves when necessary to avoid accidents, and the desire by manufacturers to add gimmicks that will inrease the prices of cars and increase manufacturers' revenues.
A simple mechanical system, even without power steering, is reliable, simple, and inexpensive. This is what I want in my car, not a lot of expensive-to-replace-when-it-fails electronics.
IMHO this is just another monumentally bad idea from carmakers, who seem to believe today that electronics make everything better. Wrong!
There already exists electric power steering systems in many cars at various price points, but it's for assist only (or for automated parallel parking). The low end cars I've driven with this ( a Saturn Coupe we used to own ) had practically zero steering feel and was miserable to drive. When it failed the steering was way over boosted to one side and not at all to the other, creating a very unsafe situation. BMW, according to a recent Car and Driver article, has produced a system that may be subjectively better than hydraulic assist, but it took years for them to get the algorithms right and they can charge what it costs to get good performance. I can only assume there is a similar failure mode.
Auto designers are forgetting that driving is inherently risky and should not be too comfortable, or too easy, or too much like riding your recliner while playing with your latest electronic gadget. I dread the day I have to replace my '04 RSX, because any new car available by then and in my budget will not be worth driving due to the excess electronic control interfaces.
Didn't Nissan also give us the one big button to both start the engine and to stop it? Or at least go along with those who started that fad? Since they demonstrated poor judgement by doing that, why should I believe that their drive by wire is any smarter? An electrically assisted power steering system would be different, and they have been around in various applications since around 1980, or thereabouts.
Don't compare this idea with aircraft fly-by-wire systems because there is no comparison. The number one directive for aviation systems is safety, followed by longevity of service, also called reliability. The number one directive in the automotive industry is PROFIT from initial sales, and next is cheapness to manufacture. We all know that it is true, at least those with any automotive engineering experience. Aside from that, only qualified people are legally allowed to service aircraft, while anybody who can grasp a wrench is allowed to service cars.
In addition, as pointed out already, how can we expect that a cheapo electronic controller in an environment nastier than the navy salt spray test, will be more reliable than the present power steering systems. Ask your self: "When was the last time that you heard about a power steering system failing"? And when the do fail it is usually the loss of assistance rather than a loss of steering control. While that failure mode may make driving difficult for the weak and feeble, it is merely quite inconvenient for most of us.
Don't compare this idea with aircraft fly-by-wire systems because there is no comparison.
Aircraft have air worthiness inspections every year and every 100 hours as well as being required to follow all recommended maintenance from the manufacturer and air worthiness directives from the FAA. Now, contrast that with how many times you've seen the Check Engine light glowing on a car that just whizzed past you 20MPH above the speed limit with a hood that hasn't been opened in the last two years.
The average motorist can't be bothered with oil changing let alone maintenance and inspection to a drive by wire system.
Why is it car makers do not understand that buyers don't want to eliminate the mechanical systems. They don't want the accelerator, steering, or brakes to be fly by wire. If you actually told customers the truth, they would refuse to buy any of the cars with these systems. Andt that is because we all know these systems are bound to fail eventually, so are unacceptible in a car.
You've got a point there, Rigby5. The thing with autos, rather than industrial vehicles is that test and maintenance practices will vary extremely widely. Commercial vehicles and aircraft have mandatory inspections, etc. The individual, on the other hand, might do only minimal inspection. What happens when there is a control failure in traffic? How do you safely get to a stop with no power?
Maybe it could serve to make the car lighter, or reduce costs, but statements such as "Enable drivers to feel" the road" or "Enhance driving" just don't make any sense! How can you disconnect the driver from the road and put him behind a simulated steering wheel and yet claim that this will help the driver feel the road? Doesn't this sound like pure marketing nonsense?
We have already tried fly-by-wire accelerators and they have proven failures. It is not just Toyota, but other cars as well that have accelerated far faster than the driver has wanted. Less well publicized is the fact fly-by-wire gas pedals also have numerous complaints for low idle as well. Cars simply are expensive or maintained well enough for these systems right now. Maybe in 30 years when the cost of the technoloy comes down, but I doubt, because there will still be far too many people who can't afford proper maintenance.
If you had a general failure, the mechanical steering linkage is expected to kick in. But if you had a general failure, what are the chances that the one thing to work would happen to be the clutch to re-engage the mechanical steering? If the electric clutch mechanism is never used, then it'll very possibly be corroded or stuck or whatever. I never used the power window switches for the rear windows in my old BMW for years at a time. When I finally did, corrosion had coated the contacts and they didnt work. Somehow I would not have a lot of confidence in the backup systems here. What would be the recommendation... hammer on the steering wheel to free it as the car veers off the road? Or just duck and pray?
It seems that all of those commenting don't like the concept of steer by wire for a number of different reasons. And all of the reasons presented do appear to be quite valid.
Of course the reason that Nissan wants to sell it is because it reduces the cost to build the vehicle, not because of any improvement that it offers. But that would never sell, so they need to make up some tale about how wonderful it would be.
I really don't like it at all when people or companies lie to me.
I could be wrong, but I believe one of the big advantages of steer-by-wire right now lies in the manufacturing differences between left-hand drive and right-hand drive. Right now, that's a big change, going from left to right to accommodate sale in other countries. If you take away the mechanicals, though, the manufacturing change is no big deal. For that matter, you could put the steering wheel in the back seat, or you could use a joystick to drive the car, and that wouldn't be a very big deal, either.
It won't be long and we can finally drive a car using the X-box remote. In all seriousness though, I wonder if this technology might open up the doors to a better way for drivers to control their vehicles.
I am not sure if there is a better way to steer a car than using the steering wheel. Consider that it never gets lost, and it is positioned so that it can be turned by either hand. Also, the motion is intuitive to almost everybody-turn the wheel right to turn right, about as easy to figure out as possible. If there were an electrical control for it, we might wind up like we are with seatbelt buckles, with a bunch of different kinds, and some of them are really TRASH, in that they are hard to connect and impossible to release wearing heavy gloves. Just think, they all started out just like the seatbelt buckles in airplanes.
Steering could wind up being a function on that same stupid big red button that is used for start and stop on some inferior brands of cars.
If you want to experience just how difficult anti-intuitive steering can be, try this experiment on a bicycle. After you get rolling along a straight clear path, grb the right-hand grip with your left hand and try to kep going straight. BUt be certain that your helmet is on correctly before doing this experiment.
Going to a non-intuitive steering method could be a real disaster.
Steer by wire allows getting rid of the engine driven hydraulic pump, but so does electrically assisted power steering. Totally removing the steering gear as it now exists gets rid of a bunch of fairly precision parts and allows the use of a much cheaper position servo system, since it does not need to be accurate because drivers go by what the car does, not where the wheel is. Completely blind drivers are a different case, though.
Drive by wire would also get rid of the strong supports for the steering wheel, since the driver is only sending a position command, probably to a computer. Would you want a computer deciding that a sharp swerve to avoid hitting someone was an unsafe move, and not make it?, or refuse to swerve around a broken bottle in the roadway? And WE KNOW that the programmers at Nissan are all "much smarter than we are". So drive by wire is still fine for planes and trains, although I understand that current Diesel engines do have a totally manual means of stopping and shutting down available.
Tell you what: I'll buy if I see it win a race in a major event. Any of the big ones: Indycar, NASCAR, F1, F2000, GT, Paris-Dakar, whatever. If you show me a race team using drive by wire for a season and winning, then I'll buy it.
If the technology is so great then show me. Any race team would love to shave weight, reduce parts and 'enhance' the driver's road feel. Also the drive-by-wire could deliver a lot of data to the race team computers. I can see how it would be a huge advantage.
Having experenced a failure of ABS the dealer told me could never happen, drive by wire scares the hell out of me. My ABS on a GM product would wait untill travling more than 32 mph before totaly disabling all brakes. I don't believe the automakers are willing to dedicate the necessary resources to developing the same safty protocals the aviation industry has. Besides, if anything goes wrong just pull over to the side of the road, oh! wait maybe that won't work.
I first saw an electric power steering system implemented in an advanced prototype my employer was asked to simulate in 1978 or 79. The design had a hollow armature servomotor driving a ballnut on a ballscrew rack that went thru the center of the motor to assist in steering and sensed the need for assist just as a hydraulic system does, by sensing the windup of a torsion rod at the pinion. It was an electric servo instead of a hydraulic servo. It seemed to work just fine, although if you turned the wheel rapidly you could feel the inertia of the servomotor.
My concern then was that the mechanical backup mode operation required backdriving the servomotor thru the ball screw-nut. That is fine when it is new, lubricated and smooth, but if the screw or nut has fatigue damage, corrosion and or contamination it would still probably work OK under power but it might not manually backdrive at all. To my knowledge, the hydraulic system doesn't have a failure mode that locks up the rack and pinion precluding manual operation.
That concept was a very compact affair, but it seemed to have a fatal flaw. I wouldn't want it in my life. How does this system deliver power assist from servomotor to the rack? Not much engineering detail given. Not in fashion.
We are reaching the point where when a car gets a few years on it, what is a relatively minor failure now, like a power steering rack or a brake booster, will be so expensive to repair it effectively makes the car a total loss. This will adversly affect resale value. As an example, take a common 2002 to 2005 Buick LeSabre. The Limited with all the bells and whistles, often can be had for the same or less than the much simpler custom trim version.
I think this a prellude to driverless cars. The more you disengage the driver from the mechanics, the easier this becomes. You have to get people used to the idea that the car will steer or do other things without the actual "feel" of the driver input. "Enhancing" the feel of the car, is rubbish. Take away the power steering, now that is "feel". Drive by wire is necessary for automated robotic driving. Personally? not for me.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.