> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Alan B. Pearce
> Sent: 18 April 2008 11:48
> To: Microcontroller discussion list - Public.
> Subject: Re: [OT] Anyone using C Compiler for critical applications
> 
> >> My Vauxhall / GM  Astra has an electrical power steering pump, lose
> >> that
> >> and I can't turn the wheel.... Is that counted as drive by wire?
> >
> >You CAN turn the steering if the pump fails, it just takes a lot of
> >effort.  The same with servo assisted brakes, you need good leg
muscles
> >to stop the car without the engine running, but it is possible.
> 
> Yes, it is an interesting experience to have your foot on the brake,
and
> turn the engine off, while the car is on a slight slope. You feel the
> brake
> pedal get steadily harder to push as the vacuum bleeds away, and you
try
> to
> stop the car rolling.
> 
> Typically when driving at highway speed the loss of power steering
will be
> barely noticeable, it will really only effect the amount of effort you
> need
> to put into the steering at low speed. Does act as a form of 'fail
safe'
> by
> making you rather nervous about starting off again after it fails.
> 
> I hadn't heard of using electric pumps for PS before, I guess it
> simplifies
> the factory installation of a heap of engine options that smaller cars
> seem
> to have these days, by not requiring the pump to be mounted on the
engine.

Electric pumps have been around for a while, my 1993 MR2 Turbo used one.
Apart from giving more flexibility in locating the pump, the pump motor
speed can be varied according to the cars speed to provide variable
assistance.

Just FYI, a some of the newer super-mini's (e.g. Corsa) have a "power
column" rather than a "power rack".  The steering column has the motor
mounted on it under the dash board and directly provides assistance
through a torque sensor built into the column.

Regards

Mike

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