Model 3: steering by wire?

[Cobbler]

Just an idea for the Model 3, steering by wire:

With autopilot, your car is able to do the steering by itself. Why bother having a steering axis installed when everything could be done electronically?
Just like in modern airplanes.

Benefits:
- Less weight, more range
- Less mechanical parts that could fail
- Faster build process of the car during production
- You could have the vibrations of a bad road filtered out, more comfortable ride
- Increase steering handling for maneuvering in the city, adjust response for the highway
- left/right steering wheel setup is easier, cheaper
- With a double redundant system, the steering wheel will be more reliable
- Overall cost savings
- The technology is out there, it exists in a reliable form. So the implementation would be low-risk

What do you guys think?

 

[ratsbew]

It is a legal requirement to have a mechanical link to the steering rack. At least in America it is.

 

[jerry33]

We can't even get energy saving camera type side mirrors (and they would save a lot of energy). There is no way government would allow steering by wire if they won't allow camera rear view mirrors.

 

[aronth5]

It is a legal requirement to have a mechanical link to the steering rack. At least in America it is.

Would be great if you could post a link to the source. Does anyone know if other countries have the same legal requirement?
Even if this was not a legal requirement I cannot imagine Tesla taking this on for Model 3.

 

[tga]

- You could have the vibrations of a bad road filtered out, more comfortable ride

Great for Grandpa's luxo-barge, horrible idea for a sports car/sports sedan

- Increase steering handling for maneuvering in the city, adjust response for the highway

Variable assist power steering systems already do this (at least to some extent. Unless you are talking about changing steering ratio?).

One issue I see getting something like this through regulators - what's the failsafe mode? Steer straight? Right?

Electronic throttle makes sense for gas cars, since it improves efficiency and emissions. The pedal becomes a torque-request pedal, and it's up to the ECU to determine how to satisfy the request (open the throttle, change spark timing, boost pressure, etc). I'm not sure the logic extends to steering.

 

[Jeff N]

Just an idea for the Model 3, steering by wire:

With autopilot, your car is able to do the steering by itself. Why bother having a steering axis installed when everything could be done electronically?
Just like in modern airplanes.

Is that how modern airplanes actually work? My impression is that planes are actually similar in concept to what you see in newer cars in that there is "by-wire" braking and assisted steering but ultimately there are still mechanical linkages in case the assistive systems fail. In a plane, the hydraulic controls can fail and the pilot can still pull back on the yoke and control the flaps but it takes a lot of physical effort on a large jet.

 

[Mad Hungarian]

Infiniti has already done this, and there is a mechanical link that engages if the DBW fails: http://www.caranddriver.com/feature...itizes-steering-but-the-wheel-remains-feature
However it was a less than resounding success with critics, and presumably enthusiasts as well as it appears the option is being yanked from the Q50S sport model: http://www.autoblog.com/2014/08/31/infiniti-q50s-getting-g37-hydraulic-steering/
I for one hope the M3 has the same excellent electrically assisted but mechanically linked system as the MS.

 

[tga]

Is that how modern airplanes actually work? My impression is that planes are actually similar in concept to what you see in newer cars in that there is "by-wire" braking and assisted steering but ultimately there are still mechanical linkages in case the assistive systems fail. In a plane, the hydraulic controls can fail and the pilot can still pull back on the yoke and control the flaps but it takes a lot of physical effort on a large jet.

The side-stick Airbus and the Boeing 777 are definitely full fly-by-wire. I believe the pre-777 Boeings are mechanical/hydraulic (not cables/pulleys), but I'll verify with a Boeing pilot I know.

 

[aronth5]

The side-stick Airbus and the Boeing 777 are definitely full fly-by-wire. I believe the pre-777 Boeings are mechanical/hydraulic (not cables/pulleys), but I'll verify with a Boeing pilot I know.

And how many redundant systems does Airbus and Boeing have which adds costs. Remember this is a thread for the Model 3 where a key objective is low cost so expecting Tesla to implement this type of system makes zero sense and that is assuming they could even get the government to ok it.

 

[agloutney]

Airbus has three independent hydraulic systems, mechanical and backup electric pumps, a power transfer unit in case a hydraulic pump (engine) stops working. There is also a ram air turbine that supplies limited bare minimum hydraulics in case of total power loss. Overkill for a car though.

 

[JER]

No mechanical feedback would certainly put me in the nope category for any car that featured it.

 

[MassModel3]

There have been multiple reports of Model S owners having all power just cease. I think this was related to the 12-volt battery and bad contacts, but I can't remember the details. But the point is that if you suddenly lose all power, you need to be able to safely steer the vehicle to the side of the road or similar safe location as you coast to a stop.

The only way to not have the mechanical linkage (that I can think of) would be if the mechanical components were detached by an electromagnet that released if power was lost, thereby reengaging the physical linkages.

As for planes, I can't really speak for jumbo jets, but fighter jets historically have had mechanical linkages and dual hydraulic systems that augment the controls for the pilot. Even if one hydraulic system fails, the pilot still has the second. If both fail, the direct linkages still work. Newer fighters with full fly-by-wire typically have triple redundancy for flight computers to make up for the fact that there are no direct linkages.

That being said, since computers do occasionally fail, there would have to be redundancy in a car with drive-by-wire to ensure occupant safety, and that means more parts and more cost. So no, I don't see this as a viable design for the Model 3. The idea is to reduce complexity with existing technologies, not try new designs that for the most part have never been done before.

 

[Mad Hungarian]

There have been multiple reports of Model S owners having all power just cease. I think this was related to the 12-volt battery and bad contacts, but I can't remember the details. But the point is that if you suddenly lose all power, you need to be able to safely steer the vehicle to the side of the road or similar safe location as you coast to a stop.

The only way to not have the mechanical linkage (that I can think of) would be if the mechanical components were detached by an electromagnet that released if power was lost, thereby reengaging the physical linkages.

As for planes, I can't really speak for jumbo jets, but fighter jets historically have had mechanical linkages and dual hydraulic systems that augment the controls for the pilot. Even if one hydraulic system fails, the pilot still has the second. If both fail, the direct linkages still work. Newer fighters with full fly-by-wire typically have triple redundancy for flight computers to make up for the fact that there are no direct linkages.

That being said, since computers do occasionally fail, there would have to be redundancy in a car with drive-by-wire to ensure occupant safety, and that means more parts and more cost. So no, I don't see this as a viable design for the Model 3. The idea is to reduce complexity with existing technologies, not try new designs that for the most part have never been done before.

If you have a look at my links posted in my earlier reply you'll see that what you're describing - including the failsafe electromagnetic clutch - not only exists but Infiniti has had it in production for the last two years on a car that starts out not far off the Model 3's target base price.
However the reason I think this makes no sense for a BEV is that it requires TWO electric motors, one to do the actual steering down at the rack and another back up near the steering wheel to provide "simulated" feedback to the driver. Why waste that extra battery juice when you can get real feedback and resistance from the actual road for free?

 

[MassModel3]

If you have a look at my links posted in my earlier reply you'll see that what you're describing - including the failsafe electromagnetic clutch - not only exists but Infiniti has had it in production for the last two years on a car that starts out not far off the Model 3's target base price.

Clutch fails closed... Triple redundant control modules... Yeah, I guess I should have actually read that before posting. :redface:

 

[Ludus]

Critiques of full drive by wire are missing the point that Model 3 is designed to be safe full L5 self driving with no humans even in the drivers seat. Mechanical linkages are meaningless if there is no hand on the wheel.

I'm convinced this is a major part of what's planned with design for manufacturability. No more right and left hand drive versions for different markets, lower weight, lower parts count, most importantly the entire drive train and control fit in the skateboard and the body is plug and play entirely separate so they're both big modules that just pop together near the end of the production line. Want van or Urban bus or convertible sports car on the same skateboard? Design and make the body separately and it will be plug and play with the existing skateboard platform. The promise of this is too important to let trivia get in the way.

 

[alseTrick]

I've never used drive by wire, but on the surface, I think I'd be fine with it.

 

[timk225]

Steer by wire is a very bad idea. It is not needed and removes a crucial safety link. Do not put too much faith in electronics. There is ZERO benefit to it.

 

[bxr140]

Steer by wire is a very bad idea. It is not needed and removes a crucial safety link. Do not put too much faith in electronics. There is ZERO benefit to it.

FUD

Most things in our life, and certainly most things on a car are managed by electronics. There are many cases where unlikely failure could lead to catastrophe, like that airbag suddenly deploying, those abs brakes suddenly failing, those headlights suddenly turing off, etc.

Steer by wire is natural technological progress, not to mention an inevitability.

 

[JER]

Reliability aside, there's one thing steer by wire doesn't do well that is intrinsic to mechanical steering: Feedback.

I can see this becoming less important as people with actual driving skill become less commonplace, but for now it's going to be an unwelcome change for many.

 

[22522]

Teslas sell (to me) because they are visceral. BMW sales have tanked, and lack of steering feel is one reason.

The 3 uses the same electronic power steering supplier as the X does. The X steering gets good reviews.

I think right now there is bimodal distribution of people interested in the model 3.

A) Those who wish they could buy a google car with no steering wheel, and are accepting the 3 as a poor substitute because it is (will be) too engaging.

And B) People who care about their immediate environment and want to maintain some connection to and dexterity with it. Visceral people. They are alive.

If the 3 is a doorway to death, in that it has no steering feedback so that all the nerves in your arms and hands atrophy away, surgeons will not drive it. Lack of product placement will kill it and kill Tesla.

Tesla is run by a guy who rolled... a McLaren (?). His engagement in the definition of what the vehicle actually is, is the reason I have a deposit down on the Model 3. If that is not important to the OP,... just buy a Google car as a commodity on cost.

Bimodal customer distributions are scary as they can destroy the essence of the product. Large car companies confuse the distribution network (dealers) with end customers. That bimodal focus makes most modern cars have no real essence. Maybe some styling or perfume. They are choosing to be commodities.