Non-mchanical Auto Steering

[teroenza]

Hello all,
With all-electric car designs becoming more popular, I was wondering if it was really necessary to have all that mechanical linkage in the front of an automobile to steer. Assuming independent electric motors for each wheel, and drive-by-wire technology, a simple alteration in wheel speed for the wheels on one side of the car could steer it (like tanks and their treads). Wheel speed, steering wheel input, and other data could easily be processed and made into a steering system. Has anyone seen any concept cars like this, or designs promising such a system? Can anyone think of major drawbacks?

Thank you

::: I'm not sure if this should be in Elec. or Mech. engineering forums, I apologize if it is incorrectly labeled.

 

[sophiecentaur]

I'm sure that electronic control would take care of a lot of the problems but, when you get down to it, deflecting the wheels on one axle (usually the front) has just got to be a good way to produce a lateral force to turn the car with minimal scuffing of the tyres. Your suggestion is rather like steering a tank, which works fine at low speed and, I'm sure, has some advantages but I don't think you could complete a Formula One course quickly in a vehicle with 'tank' steering.

 

[mheslep]

I suppose reliability is the concern, though that may be hype when compared to mechanical linkages. I don't know that a mechanical linkage is necessarily more reliable.

From the Wiki:
http://en.wikipedia.org/wiki/Drive_by_wire

Steer by Wire

This is currently used in electric forklifts and stockpickers and some tractors[1]. Its implementation in road vehicles is limited by concerns over reliability although it has been demonstrated in several concept vehicles such as ThyssenKrupp Presta Steering's Mercedes-Benz Unimog, General Motors' Hy-wire and Sequel and the Mazda Ryuga. A rear wheel SbW system by Delphi called Quadrasteer is used on some pickup trucks but has had limited commercial success.
Competitors in the DARPA Grand Challenge, an automated driving competition, relied on 100% DbW systems, in some cases including a SbW system provided by the manufacturer [2].
This is not to be confused with Electric Power Steering.

The Wiki is misleading regarding the DARPA contest. Most, if not all, of those vehicles used an electric servo motor attached to the stock mechanical steering linkage. Only one of the DARPA vehicles in the final had real drive by wire (Stanford, the winner), and that was limited to only the throttle.

One of the major advantages of drive by wire steering is the elimination of the steering wheel. No more: body - steering wheel impacts in a crash, steering wheel adjustment for the driver, visual impairment of the instrument panel, etc.https://www.youtube.com/watch?v=-iiCrFp89hU

 

[Ranger Mike]

with enuff time and money anything is possible..don't forget that the " power steering" we now have will work even if the fluid is completely gone..safety concern..if you went total electric you need a back up system...Toyota just got severe head aches with electric throttle control
..now you want t o make steering electric??
production costs and after market service is a factor..what alignment shop will have software to properly align the wheels if you ding a control arm on a curb? take it back to a dealership?
we just cut out 50 percent of the dealerships in the country last year..
keep it simple..

 

[mheslep]

keep it simple..

Like this?

[PLAIN]http://www.rootsweb.ancestry.com/~gamadis2/images/horse_and_buggy.jpe

 

[teroenza]

Thank you all for your relies. I love the James May clip.

 

[mgb_phys]

Like this?

[PLAIN]http://www.rootsweb.ancestry.com/~gamadis2/images/horse_and_buggy.jpe[/QUOTE]

Not sure that would pass emissions tests

 

[mheslep]

Not sure that would pass emissions tests

Emissions from passengers or the horse?

 

[mgb_phys]

Emissions from passengers or the horse?

I don't think the horse's tailpipe emissions would pass 'aircare'

 

[Ranger Mike]

close to perfection..now i can get home on auto pilot when i enjoy too many adult beverages at local watering hole...head for the barn, Ned..giddiapp

 

[mgb_phys]

close to perfection..now i can get home on auto pilot when i enjoy too many adult beverages at local watering hole...head for the barn, Ned..giddiapp

http://news.bbc.co.uk/2/hi/uk_news/england/tyne/7861406.stm

 

[Ranger Mike]

government will get you one way or another!

 

[xxChrisxx]

Not even remotely a chance that i'd be driving a car without a mechanical linkage, it's not just the point of the electric connection failing (as you can have multiple redundancies), what if your altenator fails and you run out of battery. At least you can still steer with a mechanical linkage.

Also there is every chance that people will kill themselves at any sort of speed by not having any feel for the steering what so ever. You may not think it, but you'd be so surprised at just how much information you receive subconsiously through the little vibrations and weighting of the steering wheel. The tyre let's you know when it's about to break free and lose it's grip, you can't have that with no physical connection between the steering wheel and road wheels.EDIT: It's cartainly possible though. If you were so inclined you could drive a car with a playstation controller. The actual physics of it are pretty simple.

 

[Janus]

Not even remotely a chance that i'd be driving a car without a mechanical linkage, it's not just the point of the electric connection failing (as you can have multiple redundancies), what if your altenator fails and you run out of battery. At least you can still steer with a mechanical linkage.

Also there is every chance that people will kill themselves at any sort of speed by not having any feel for the steering what so ever. You may not think it, but you'd be so surprised at just how much information you receive subconsiously through the little vibrations and weighting of the steering wheel. The tyre let's you know when it's about to break free and lose it's grip, you can't have that with no physical connection between the steering wheel and road wheels.


EDIT: It's cartainly possible though. If you were so inclined you could drive a car with a playstation controller. The actual physics of it are pretty simple.

Several years ago I read an article about the future car design. One of the concepts brought up was active suspension. The suspension system could detect variations in the road surface and actively move the wheels to compensate. The idea was that you could "dial in" your ride.

During test drives, when the system was put in full active mode as to give the smoothest possible ride, the drivers complained that they lost a feel for the road, which they found disconcerting.

 

[mheslep]

Not even remotely a chance that i'd be driving a car without a mechanical linkage, it's not just the point of the electric connection failing (as you can have multiple redundancies), what if your altenator fails and you run out of battery. At least you can still steer with a mechanical linkage.

Oh no! Someone tell this guy to eject!

http://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting_Falcon#Flight_controls

Seriously, we're already past the point of direct mechanical control for many car drivers. If the power steering fails then many females or the frail are unable to control the vehicle in all conditions.

I agree with you on the importance of steering feedback, but some of that comes back to the driver through the chassis outside of the steering column. That is, even a passenger receives some feel for the road. Also, artificial feedback can flow to electric steering controls, just as it is now in aircraft stalls. Not that these points mean the problem is solved, but seems to indicate is solvable.

Some current mech steering http://www.cbsnews.com/stories/2010/07/29/business/main6724183.shtml":

The Avalons recalled in the U.S. range from the 2000 model year through to 2004 and have improper casting of the steering lock bar - the component that locks the steering wheel when the vehicle is shut off - that can cause a crack to form on the surface.

Over time, the crack can expand, which can cause the steering wheel to become difficult to unlock when stationary. In some circumstances, the problem can cause the steering wheel to lock up during driving, Toyota said.

Three unconfirmed accidents with no injuries have been reported because of the problem, Toyota said.

 

[mgb_phys]

During test drives, when the system was put in full active mode as to give the smoothest possible ride, the drivers complained that they lost a feel for the road, which they found disconcerting.

Probably because they tested it with enthusiasts or track drivers - not suburban minivan drivers.
By the same standard nobody would have introduced automatic transmissions.

 

[xxChrisxx]

Oh no! Someone tell this guy to eject!

Very droll, point is if the **** hits the fan he CAN eject.

Seriously, we're already past the point of direct mechanical control for many car drivers. If the power steering fails then many females or the frail are unable to control the vehicle in all conditions.

You can build massive factors of safety into the mehanical components, just like you can can build backups and redundancies into the electrical system. Either way being a car nut and a mechanical engineer, I like large lumps of metal and not electrickary.

EDIT: I'd also like to comment on power steering. I find that tends to deaden the feedback,. Especially in Puntos with the girly steering button on, the wheel just feels dead (im fairly sure you aren't suposed to drive above 15mph with it on, as it gives lolwobble moments). Give me no power steering on a quick rack any day, just don't ask me to parallel park!

I agree with you on the importance of steering feedback, but some of that comes back to the driver through the chassis outside of the steering column.

Chassis = rear wheels, steering wheel = front wheels. That's how I can tell what's doing what. I can gaurantee you in a front wheel drive car having a wheel that is like driving in the arcades will be scary as hell when you push on.

There's also no way to replicate the direct transimssion of what the wheel is doing. If you are driving on low profile tyres, that will tend to 'snap' rather than give up their grip gradually then no atrificial feedback will let you know that.

That is, even a passenger receives some feel for the road. Also, artificial feedback can flow to electric steering controls, just as it is now in aircraft stalls. Not that these points mean the problem is solved, but seems to indicate is solvable.

They have a system on the playstation, logitech G25 iirc. It's the closest thing to real life driving with GT5, the steering wheel weights up as you turn it, it also has pedal feel. As close as it is, it's just not the same as wheel - metal link - tyre - road.

 

[mheslep]

You can build massive factors of safety into the mehanical components, just like you can can build backups and redundancies into the electrical system.

No, not like electrical systems. In mechanical systems you generally get cascading mass and damping multipliers when you add either strength or redundancy safety factors, which in turn increases cost and impacts the performance of the overall system. For example, and grossly oversimplifying: stronger (or redundant) mechanical tie rods add mass to the steering assembly which requires stronger mechanical tie rods which ...

Either way being a car nut and a mechanical engineer, I like large lumps of metal and not electrickary.

Fair enough