Brake-Throttle override

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Brake-Throttle override

Jay Donnaway
I've noticed that the Soliton includes such programming, but Zilla does not.  Any ideas on a way to add a brake interlock to the Zilla, Curtis or other controllers without the problems of freqent main contactor cycling?  One way I've considered would be a microswitch in the pot signal wire that opens when you press the brake pedal (or a normally closed reed switch next to the brake light wire).  The microswitch wouldn't normally be opening under load, so once it's dialed in, the gradual addition of resistance over time should be miniscule...


Jay Donnaway
www.karmanneclectric.blogspot.com




NHTSA Proposes ‘Brake-Throttle Override’ Regulation to Prevent Unintended Acceleration Incidents
April 12, 2012
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WASHINGTON – The U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) has proposed new safety standards for vehicles would add a “brake-throttle override” to vehicles. This feature is designed to ensure a driver can stop a vehicle if he or she depresses the brake and accelerator pedal at the same time. The change is designed to reduce the risk of high-speed unintended acceleration and prevent crashes due to a stuck, or trapped, accelerator pedal.

“We learned as part of the comprehensive NASA and NHTSA studies of high-speed unintended acceleration that brake override systems could help drivers avoid crashes,” said NHTSA Administrator David Strickland. “While NHTSA’s defect investigation program will continue to monitor and consider consumer complaints of any potential vehicle safety issues, this proposal is one way the agency is helping keep drivers safe and continuing to work to reduce the risk of injury from sticky pedals or pedal entrapment issues.”

According to NHTSA, the proposed change would amend Federal Motor Vehicle Safety Standard (FMVSS) No. 124, Accelerator Control Systems. The change would update the throttle control disconnection test procedure for all passenger cars, multipurpose passenger vehicles, trucks and buses of any weight. For vehicles with Electronic Throttle Control (ETC), and a GVWR of 10,000 lbs. or less, the proposal would also require manufacturers include a Brake-Throttle Override (BTO) system.

The public comment period is now open. You can click here to view the proposal.














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Re: Brake-Throttle override

Roger Stockton
Jay Donnaway wrote:

> I've noticed that the Soliton includes such programming, but Zilla does
> not.  Any ideas on a way to add a brake interlock to the Zilla, Curtis or
> other controllers without the problems of freqent main contactor cycling?
> One way I've considered would be a microswitch in the pot signal wire that
> opens when you press the brake pedal (or a normally closed reed switch
> next to the brake light wire).  The microswitch wouldn't normally be
> opening under load, so once it's dialed in, the gradual addition of
> resistance over time should be miniscule...

For the Curtis, an approach discussed in the past has been to wire a brake switch and pot box switch such that the main contactor closes when the throttle is depressed, but instead of opening each time the throttle is released, it opens only when the brake is pressed (and then remains open until the throttle is depressed again).  With the Curtis, having the main contactor open each when motive power is not intended is a required safety feature.

For more sophisticated controllers, such as the Zilla, that have other safety logic that will drop out the main contactor for you when required, you could do as you propose.

I would suggest that instead of opening the throttle signal line when the brake is pressed, you instead use the brake switch to place a small value resistor in parallel with the throttle pot.  This will limit the maximum throttle command to a low value when the brake is depressed, but will avoid the possibility of causing a controller fault that might require a power-cycle to clear.  (Even the Curtis includes fault detection for an open or shorted throttle pot, and so opening the throttle signal might cause a fault condition that requires you to power cycle the controller to resume normal operation after each use of the brake.)

Cheers,

Roger.


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Re: Brake-Throttle override

EVDL Administrator
In reply to this post by Jay Donnaway
On 13 Apr 2012 at 13:15, Jay Donnaway wrote:

> Any ideas on a way to add a brake interlock to the Zilla, Curtis or other
> controllers without the problems of freqent main contactor cycling?

What are the problems of frequent main contactor cycling?

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: Brake-Throttle override

Roland Wiench
In reply to this post by Roger Stockton
The Zilla in its normal operation, does not cycle the main contactor every
time you let up on the accelerator.  When the accelerator resistance drops
below 50 ohms, the controller shuts down the motor, but the main contactor
is still close.

In startup, the main contactor must be open, main battery power on the input
side of the contactor, and the accelerator resistance at 0 ohms.  Pressing
on the accelerator until the resistance gets above 50 ohms, will turn on the
motor controller to the motor.

This procedures prevents the motor to run if the accelerator linkage does
not return to 0 ohms, in my case I had the floor mat laying on the
accelerator pedal which took me sometime to figure that one out.

Roland


----- Original Message -----
From: "Roger Stockton" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Friday, April 13, 2012 11:52 AM
Subject: Re: [EVDL] Brake-Throttle override


> Jay Donnaway wrote:
>
> > I've noticed that the Soliton includes such programming, but Zilla does
> > not.  Any ideas on a way to add a brake interlock to the Zilla, Curtis
> > or
> > other controllers without the problems of freqent main contactor
> > cycling?
> > One way I've considered would be a microswitch in the pot signal wire
> > that
> > opens when you press the brake pedal (or a normally closed reed switch
> > next to the brake light wire).  The microswitch wouldn't normally be
> > opening under load, so once it's dialed in, the gradual addition of
> > resistance over time should be miniscule...
>
> For the Curtis, an approach discussed in the past has been to wire a brake
> switch and pot box switch such that the main contactor closes when the
> throttle is depressed, but instead of opening each time the throttle is
> released, it opens only when the brake is pressed (and then remains open
> until the throttle is depressed again).  With the Curtis, having the main
> contactor open each when motive power is not intended is a required safety
> feature.
>
> For more sophisticated controllers, such as the Zilla, that have other
> safety logic that will drop out the main contactor for you when required,
> you could do as you propose.
>
> I would suggest that instead of opening the throttle signal line when the
> brake is pressed, you instead use the brake switch to place a small value
> resistor in parallel with the throttle pot.  This will limit the maximum
> throttle command to a low value when the brake is depressed, but will
> avoid the possibility of causing a controller fault that might require a
> power-cycle to clear.  (Even the Curtis includes fault detection for an
> open or shorted throttle pot, and so opening the throttle signal might
> cause a fault condition that requires you to power cycle the controller to
> resume normal operation after each use of the brake.)
>
> Cheers,
>
> Roger.
>
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
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>

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Re: Brake-Throttle override

Cruisin
In reply to this post by Jay Donnaway
Why dont you use the throttle pedal that has a 0-5k pot and 2 wire n/o switch in it. It will do all you are asking with quality and no cables or micky mouse connections from front to rear. Just like production cars, drive by wire. Simple as that.
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Re: Brake-Throttle override

Jay Summet
In reply to this post by EVDL Administrator
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On 04/13/2012 03:48 PM, EVDL Administrator wrote:
> On 13 Apr 2012 at 13:15, Jay Donnaway wrote:
>
>> Any ideas on a way to add a brake interlock to the Zilla, Curtis or other
>> controllers without the problems of freqent main contactor cycling?
>
> What are the problems of frequent main contactor cycling?

They wear out....or at least the manual for the EVA S-10 says to swap
the main/secondary contractor every year to even out the wear patterns.

Jay
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Re: Brake-Throttle override

Jay Summet
In reply to this post by Roger Stockton
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


> I would suggest that instead of opening the throttle signal line when
> the brake is pressed, you instead use the brake switch to place a
> small value resistor in parallel with the throttle pot.  This will
> limit the maximum throttle command to a low value when the brake is
> depressed...

This will work if the controller is working. However, if your controller
fails ON, adding resistance to the POT signal won't help anything, but
opening a main contractor will save the day...

Jay
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Re: Brake-Throttle override

Phil Marino-2
In reply to this post by Jay Donnaway
I've got my Curtis set up so that the main contactor relay latches closed
when you hit the throttle ( using the potbox microswitch) and stays closed
until you hit the brakes ( or, turn off the ignition switch)

.  So, the contactor does cycle open and closed, but not very often. I
don't see this contactor cycling as a problem.  Since there ( generally) no
current flowing, there is no contactor contact wear.  And, the noise is
barely noticeable.  it was easy to do it this way with a couple of relays.

With this setup, if there is a "controller full on" failure, using the
brakes will de-power the controller and let you stop safely.  And, if you
hit the brakes and throttle at the same time, the main contactor will stay
open.

Phil Marino

On Fri, Apr 13, 2012 at 1:15 PM, Jay Donnaway <[hidden email]> wrote:

> I've noticed that the Soliton includes such programming, but Zilla does
> not.  Any ideas on a way to add a brake interlock to the Zilla, Curtis or
> other controllers without the problems of freqent main contactor cycling?
>  One way I've considered would be a microswitch in the pot signal wire that
> opens when you press the brake pedal (or a normally closed reed switch next
> to the brake light wire).  The microswitch wouldn't normally be opening
> under load, so once it's dialed in, the gradual addition of resistance over
> time should be miniscule...
>
>
> Jay Donnaway
> www.karmanneclectric.blogspot.com
>
>
>
>
> NHTSA Proposes ‘Brake-Throttle Override’ Regulation to Prevent Unintended
> Acceleration Incidents
> April 12, 2012
> SHARING TOOLS        | Print Subscribe
> Share on google_plusone Share on facebookShare on twitterShare on
> linkedinMore Sharing Services
> ?
>
>
>
>
> WASHINGTON – The U.S. Department of Transportation’s National Highway
> Traffic Safety Administration (NHTSA) has proposed new safety standards for
> vehicles would add a “brake-throttle override” to vehicles. This feature is
> designed to ensure a driver can stop a vehicle if he or she depresses the
> brake and accelerator pedal at the same time. The change is designed to
> reduce the risk of high-speed unintended acceleration and prevent crashes
> due to a stuck, or trapped, accelerator pedal.
>
> “We learned as part of the comprehensive NASA and NHTSA studies of
> high-speed unintended acceleration that brake override systems could help
> drivers avoid crashes,” said NHTSA Administrator David Strickland. “While
> NHTSA’s defect investigation program will continue to monitor and consider
> consumer complaints of any potential vehicle safety issues, this proposal
> is one way the agency is helping keep drivers safe and continuing to work
> to reduce the risk of injury from sticky pedals or pedal entrapment issues.”
>
> According to NHTSA, the proposed change would amend Federal Motor Vehicle
> Safety Standard (FMVSS) No. 124, Accelerator Control Systems. The change
> would update the throttle control disconnection test procedure for all
> passenger cars, multipurpose passenger vehicles, trucks and buses of any
> weight. For vehicles with Electronic Throttle Control (ETC), and a GVWR of
> 10,000 lbs. or less, the proposal would also require manufacturers include
> a Brake-Throttle Override (BTO) system.
>
> The public comment period is now open. You can click here to view the
> proposal.
>
>
>
>
>
>
>
>
>
>
>
>
>
>
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Re: Brake-Throttle override

EVDL Administrator
In reply to this post by Jay Summet
On 13 Apr 2012 at 20:52, Jay Summet wrote:

> > What are the problems of frequent main contactor cycling?
>
> They wear out....

I wouldn't think this would be much of a problem, unless you're opening them
under load frequently - and if that's the case, you have bigger problems
than contactor wear.

IMO, even if it does result in some wear, with a DC controller - especially
a Curtis which has no real safeguards - the additional security you get from
opening a main contactor on pedal release is worth it.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: Brake-Throttle override

Lee Hart
In reply to this post by Jay Summet
>> What are the problems of frequent main contactor cycling?
> They wear out...

I suppose they might. But the rated life is a million cycles at no load
(which is how the contactor will operate if switched with the potbox
switch).

How long is that? Let's say you switch it once a minute. 1 million
minutes is 16,667 hours. Driving at an average of 30 mph, that's 500,000
miles! Seems pretty unlikely to wear out.

Now, if you don't have a precharge resistor, the main contactor would be
switching current when it closes. That would shorten its life considerably.
--
If we knew what we were doing, it wouldn't be called research, would it?
        -- Albert Einstein
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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Re: Brake-Throttle override

Roger Stockton
In reply to this post by Jay Summet
Jay Summet wrote:

> This will work if the controller is working. However, if your controller
> fails ON, adding resistance to the POT signal won't help anything, but
> opening a main contractor will save the day...

Yes, this is why I noted that it is an essential safety feature with a Curtis-type controller that the main contactor opens when you are not intending motive power.

I do not recommend using the brake switch to modify the throttle command, but if one is going to do so, then placing resistance in parallel (*reducing*, not adding to the throttle pot resistance) is preferable to opening the throttle pot signal.  Opening the throttle pot signal may trip a controller fault and require that the controller be power-cycled to reset it.  Using a parallel resistance to limit the maximum throttle command to a small value will not cause a fault.

Note that the original question was not about adding safety in the event of a controller failure, but how to protect against unintended acceleration with a working controller when the throttle is unintentionally pressed at the same time as the brake.

Having the main contactor pick up on the throttle being pressed and dropping out upon the brake being pressed is definitely a better approach.  The brake would have to override the throttle, and ideally the logic would not allow the contactor to close if the throttle and brake are both applied and then the brake is released while the throttle continues to be held on.  (i.e. if both are pressed at the same time, the contactor should open and should not close until *both* throttle and brake have been released, and then the throttle alone is pressed.)

Another idea floated here in the past was to use a reed switch to sense motor (controller output) current so that the main contactor would open if the motor current is ever above some threshold while the throttle is released.  I don't recall offhand if the idea was to have the contactor drop out upon application of the brake, or only have it drop out if motor current continued to flow.  The beauty of this scheme is that it only opens the contactor if significant motor current is observed when none is being commanded (i.e. throttle released and/or brake pressed) instead of every time the throttle is released or each time the brake is pressed.  I believe the original idea was John Wayland's.

Cheers,

Roger.


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