Ok i'm doing this for a final in my auto mechanics class and i've found a lot of information on the actual steering systems. The only problem is we have to have a fail-safe system that comes into play if the system fails. My friend came up with the idea of an electro magnet and when there's no power to the magnet the column falls down and locks into place.

I can't use the same idea so i searched for more information on other fail-safe systems and found one with a clutch system but can't find out how it works. If anyone on here could explain this to me or give me a great article on it i would definetly appreciate it. I'm not asking you to do my work i just need some major help on the fail-safe system so i don't fail this final. Thanks guys.

Edit: If this post is in the wrong forum, sorry and Mods if you could move it to the right one. Thanks a lot guys.


Modified by 94CivicDx5spd at 11:33 AM 12/7/2004

 

Why does the column ever have to be disconnected in the first place? In the normal hydraulic PS systems the column is always there, the spool valve just directs hydraulic pressure to 'help push' the rack. I suppose the new Civic's electic system is sorta the same - I bet the column is never really disconnected.

 

Well there is to be no connection from the steering wheel to the wheels. And it has to have a fail safe system. And i just need some help on the fail safe system so far. I guess the column can be hooked on still but the actual steering wheel can't. But my friends idea was to have the column disconnected until the system fails and then locks into place like a regular system. If anyone else can help me please do.

 

bump

 

Why can't you do the clutch thing? That sounds simple. The clutch is disengaged by means of a servo type system until the system loses power in which case the clutch engages therefore connecting the column and the wheel. You just have to come up with anything where the default is safe mode and it requires power to not be in safe mode. A clutch's natural state is to be engaged by means of the springs. If an electrical servo or similar disengaged the clutch, when power died, it would return to engaged and you'd be all set.


The only other thing I could think of is some sort of pin that could be held back by electrical or magnect or hydrolic or vacume means, that drops in to place "connecting" the columns? They'd have to be in the same postion when it failed for that to work though I suppose.

I'm not good at this stuff, just trying to help.

 

First, the term fail-safe usually refers to failing in one position - valves can be fail-open or fail-closed. Depending on the process involved, One condition is generally "safer" so that would be chosen.

In this situation, failing in one position is not an option - you still need full control. I suppose you could live with increased effort, or slightly reduced range, but anything else would not be safe.


I dont know if completly disengaging the steering mechanism would ever be Totally safe - (What if those parts rusted or corroded, not allowing it to engage in manual?)

Your active system will have to compress a spring which keeps the steering wheel disengaged and operating off the steering wheel postion sensor only. When that system fails, the spring releases and forces the assembly together - through a splined shaft or something like that...


Your best bet for keeping the spring compressed when the system is operating is probably a diaphram and a compressed fluid (air or oil) maybe that compressed fluid could be used run the steering system too.

 

I just dont understand the point of a "drive-by-wire" steering wheel. If there are no mechanical parts involved directly, then how is that safe if the electronic system fails? And if there ARE mechanical parts connecting the two, whats the point of the "drive by wire"?

 

i agree with the clutch option. that sounds like a good idea to me.

basically have the electric steering control the steering, when the fails, have a clutch engage and "reconnect" you to manual steering.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDM_Ej &raquo;</TD></TR><TR><TD CLASS="quote">I just dont understand the point of a "drive-by-wire" steering wheel. If there are no mechanical parts involved directly, then how is that safe if the electronic system fails? And if there ARE mechanical parts connecting the two, whats the point of the "drive by wire"?</TD></TR></TABLE>

i do remember one of the supposed "benefits" are that there would be no vibrations or pulsations in the steering wheel since it was not connected mechanically, rather just an electronic device.

i agree its not safe at all, and makes it hard to get a "feel" for the road and conditions as well as flat tire, bad suspension.

 

For the benefits of steering by wire;

-Efficiency- depending on the system used, it may be more efficent. This wouldn't be a big factor, but it may have some significance.

-Like the TSX throttle, you can (more easily) have a non-linear relationship between input and output. (TSX's throttle tip in is electronically suppressed)

-Packaging - this more relates to electic motors in place direct drive off the motor - The electric motor can be placed wherever it fits, you are not tied to a belt drive off the motor

-When the systems are reliable enough (way down the road) mechanical linkages may be eliminated entirely. Although not feasable now, it could happen and you have to start somewhere

 

Well the "drive by wire" system right now isn't safe. This is just a final to get us thinking and using our knowledge of basic electronics. The new cobalt has the drive by wire system but they are having some trouble with it. It tends to want to go to the right. Partly because the positions sensors are on the inner of the rack and pinion, instead of having it out where the wheels are.

As far as the problem of not being able to feel the road. Our other objective is to keep the road feel so you know if there is a problem. I am going to use a system like a PS2 controller. I will have a sensor at the bottom of the control arm, so that everytime you hit a bump or any kind of vibration from the sensor it will be sent straight to the steering wheel.

Another benefit of the sytem is to save weight and space. It will also get rid of all the hydralic lines and the power steering pump. I think it would be a good system as long as all of the cons were fixed. I really like the clutch idea and the spring idea i believe would work also. The clutch idea i think would work better just because the system would always be in movement and wouldn't just sit there like the spring and have a good chance of rusting and corroding.

I like the idea of everyone's input. If someone could explain a little more about the clutch system it would help. I'm a noob to a lot of this, and i really don't understand the clutch sytem. I have a basic knowledge of it but the details are what i need help with. I appreciate everyones input, if there is anymore then please add on to this.

 

A clutch on the steering shaft would be like a miniature version of the clutch in a tranny. When you push on the release-bearing, it disconnects the upper & lower parts of the shaft from each other. They're still right there, maybe only a few thousandths of an inch apart. But they can spin free, just like when you hold down your clutch pedal.

Say that's energized by your drive-by-wire system. When it fails, that lets the clutch engage, just like you let your foot off the clutch pedal.

My Saab has a drive-by-wire throttle, but there's a throttle cable & drum, looks just like a normal throttle. But when you look in the bore, the cable drum doesn't actually open the throttle plate. When something screws up, it goes into 'limp-home' mode where the cable drum clamps itself to the throttle shaft, & then it works like a mechanical TB until you reset it.

 

I see what your talking about now. Could i use a spring of some sort to hold the release bearing up keeping the clutch from touching the other side and engaging? I still need to figure out a way for the spring to release the bearing when the system fails. So i need to use some kind of a electrical magnet. Guess i'm going to do some more research until i find this out cuz the outline is due tomorrow. So if you could help on that, that would be great but you have done a lot already. Thanks guys. Btw JimBlake your sig. is true you are a wizard lol.