Electric Drive Safety

[69nova]

Regarding cars with steering and braking by wire, what happens if you're going down the road and the car conks out? With a car that has the mechanical steering and braking, these features still remain operative (yes, you lose power steering but you can still horse the wheel and guide the vehicle).

[RoGuE]

I don't know of any vehicles that have braking by wire. As far as the steering goes, it is my understanding it will respond the same as a hydraulic unit that loses power, just very hard to steer.

[coaster.n3rd]

Originally Posted by RoGuE

I don't know of any vehicles that have braking by wire. As far as the steering goes, it is my understanding it will respond the same as a hydraulic unit that loses power, just very hard to steer.

correct. I used to kill the motor in my old Cobalt with EPS to save gas when pulling into a parking spot. Just difficult to steer at low speeds and very easy to control at high speeds.

[Triple-X08]

its pretty reliable, say a TAC system fails, you can still get home, it goes into a safe mode when it detects a fault, never heard of it failing and taking off yet.

the electronic power steering system on todays vehicles still use a mechanical link to the rack, but uses a electric motor to provide assist, like a power steering pump would.

systems that will superceed the electronic power steering systems, such as a steer by wire system, which i dont beleive is out yet, i would assume would fall under the same circumstances as a throttle by wire system.

brake by wire is already out, volvo i know has it, not sure if its in production, but i have heard they have the system, and that was 2 years ago. basically just uses electric motor for the caliper piston, no hydraulic lines at all. which is a good system, because it would be more responsive, ABS systems would be more accurate, stability control would be better, gas mileage would increase as you dont have drag like you would with a hydraulic system.

sooner or later, when they go to individual wheel motors, they will use the individual motors to slow the vehicle and propel it, but that all wont happen until battery technology is good. by that time, series hybrids will be in play such as the volt, and technology will be derived from vehicles such as it, which will start the electric revolution.

its already being used, i believe the equinox fuel cell vehicle has it, because it uses hydrogen to run it, so it would have to use some sort of electric motor assembly to drive it, and by doing so you could easily incorporate a electronic braking system into the vehicle with the same motors to drive it.
could all be done with pulse modulation, or opposing motor on times, and off.

[69nova]

I am sorry that I truncated my thread. Let us look at the accelerator pedal that controls the engine speed via a po on the pedal---it sends an electric signal to a servo that does what a cable does. What happens when the electricity is lost? The same goes for braking by wire--no juice means no signal for the calipers to stop. With cables and hydraulics, the source of power is independent of the motor turning the alternator. Steering via wire is nothing more than a sensing device on the steering wheel that sends a signal to the assembly under the hood which, in turn, turns the mechanical drive to the wheels. When the motor conks out, the alternator stops whcih leads to the battery being the only source of power to these control features. I know the safety committees have looked at these situations and the vehicle must be driveable for some short distance. But it still seems iffy.

[F14CRAZY]

Does a brake by wire system still have a mechanical E/parking/hand brake?

[Triple-X08]

the safety behind the drive by wire systems will get better as technology becomes more abundant, as well as it has been tried and proven over the years, no one knows the reliability of the systems 10 years down the road,
but they are reliable at the moment. i would assume the other systems like brake by wire and steer by wire would have some sort of a fail safe, just like a TAC system, or drive by wire. what will be the really cool thing is when they make items wireless. such as a throttle body with an actuator that has a wireless module running it. if you get everything running wirelessly, like a ethernet system, such as with a wireless router, and network all the systems, its going to be some cool stuff.

yes i would assume that the brake by wire systems would use a mechanical link like a traditional e-brake system. thats what its there for, incase of a catostrophic failure of the hydraulic system, you can still use the mechanical e-brake to slow the vehicle safely.

if your throttle actuated control system fails, it still lets you get home, it uses a failsafe. when the system sees a event where the accelerator pedal position sensor didnt correlate with the throttle body, it goes into limp home mode. so i assume with other systems, they would use the same type of deal

[boston boy]

what are brakes for???

[Elk]

Originally Posted by 69nova

Regarding cars with steering and braking by wire, what happens if you're going down the road and the car conks out? With a car that has the mechanical steering and braking, these features still remain operative (yes, you lose power steering but you can still horse the wheel and guide the vehicle).

Cars (at least all the ones I can think of) don’t have steering and/or braking by wire. They have electronic things that assist steering and braking, but are not dependent on them to work.

All losing power means is you lose stuff like power steering and ABS. The brakes and steering still work.

[RoGuE]

Originally Posted by Elk

Cars (at least all the ones I can think of) don’t have steering and/or braking by wire. They have electronic things that assist steering and braking, but are not dependent on them to work.

All losing power means is you lose stuff like power steering and ABS. The brakes and steering still work.

To expand: Steering via physical connection to the steering rack and brakes via hydraulic pressure on the caliper. Although with the brakes you will only have 2 or 3 good braking pumps before you really have to stand on the pedal.

[Triple-X08]

there are vehicles that have complete drive by wire, just not in production, but vehicles like the equinox fuel cell vehicle will have to have some way of propulsion so i assume they use wheel motors, which would incorporate a electronic braking system into it.

[Elk]

Originally Posted by Triple-X08

there are vehicles that have complete drive by wire, just not in production, but vehicles like the equinox fuel cell vehicle will have to have some way of propulsion so i assume they use wheel motors, which would incorporate a electronic braking system into it.

I'm pretty sure the Equinox still uses the normal motor setup. I mean I’m sure it’s got some kind of regenerative braking but it’s on top of normal brakes.

[Canyonaro]

Originally Posted by Triple-X08

there are vehicles that have complete drive by wire, just not in production, but vehicles like the equinox fuel cell vehicle will have to have some way of propulsion so i assume they use wheel motors, which would incorporate a electronic braking system into it.

The GM Hywire for instance.

http://en.wikipedia.org/wiki/General_Motors_Hy-wire

EDIT: I read the Times Magazine 2002 "best invention". Although it wasn't horribly long ago I had to laugh at this, "Paris Auto Show last September: the Hy-wire, a politically correct, fully functional prototype that General Motors claims could be road ready by 2010." I guess GM was way off on that.

[Elk]

Originally Posted by Canyonaro

The GM Hywire for instance.

http://en.wikipedia.org/wiki/General_Motors_Hy-wire

EDIT: I read the Times Magazine 2002 "best invention". Although it wasn't horribly long ago I had to laugh at this, "Paris Auto Show last September: the Hy-wire, a politically correct, fully functional prototype that General Motors claims could be road ready by 2010." I guess GM was way off on that.

What’s funny about that story is anyone that knows anything about cars knew the Hywire was never going to be a production car. It doesn’t take an automotive engineer to realize a car that’s a glass bubble isn’t going to meet crash test standards.

[Canyonaro]

Originally Posted by Elk

What’s funny about that story is anyone that knows anything about cars knew the Hywire was never going to be a production car. It doesn’t take an automotive engineer to realize a car that’s a glass bubble isn’t going to meet crash test standards.

Thats so very true..