# The "Oh Scheisse! Bar" round deux



## Woodsmith (Jun 5, 2008)

There is already a system that shuts off an ICE when it senses the decelleration due to an impact.

I can imagine that a similar thing could be made to react to sudden acceleration.
However!
What would you set it to?
If you were driving at 70mph and the controller failed on then the rate of accelleration would be minimal.
But if you were stopped and then the controller failed on the rate of accelleration would be large.

Also what would prevent it from being activated when you are at that traffic light grand prix proving to the petrol head next to you that and EV isn't slow to move off? Full power is full power whether by a failed controller or foot to the floor.

In practice the forces of accelleration due to the sudden application of full power is less then that caused by hitting a pot hole or bouncing off the kerb when parking badly. The difference being that these accidental accellerations are momentary where as full power is over a longer duration.
So the sesor has to be able to tell the lower continuous accelleration from the momentary bumps and impacts from day to day driving.


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## dexion (Aug 22, 2009)

Not quite the same thing you are looking for but very simple and not too expensive. Easy to mount as well. Perhaps it will help you.

I tied a string to the lever (mine has a small bar with a large paddle lever so its perfect for this) used a couple of eye hooks and a pull string. I mounted it so down is off. It takes very little to drop it down its hard to pull up. Keeps pack voltage out of the cabin (its in the trunk in a pvc enclosure.) See link below.

http://www.evparts.com/products/str.../circuit-breakers---street-vehicle/cb2410.htm

It trips at 310 or so battery amps sustained but will allow peaks of 1000 amps. Ive never tripped it. So really it depends on your application. I use about 200 amps accelerating but my car is only about 2000 lbs.


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## notailpipe (May 25, 2010)

Thanks Woodsmith for all the helpful comments! I really appreciate the feedback.



Woodsmith said:


> If you were driving at 70mph and the controller failed on then the rate of accelleration would be minimal.
> But if you were stopped and then the controller failed on the rate of accelleration would be large.


Good point. As you can tell, I have not fully fleshed out the idea.  That is definitely something to think about.



Woodsmith said:


> Full power is full power whether by a failed controller or foot to the floor.


Is this true? I would guess for 90% of the DC systems out there, they are not using a Zilla2K and their real limiter is the controller rating. I highly doubt that a Curtis controller, when set to 100% throttle, is giving 100% PWM (and therefore like a direct connect to Vbat). It is going to be limited by the max current of the controller before the safety limiter. So let' say your battery pack can put out 1000A peak but your controller limits it to 500A continuous at 100% throttle - then if the controller is fried, you're dumping all 1000A and thus full_battery_pack != pedal_to_floor.



Woodsmith said:


> So the sesor has to be able to tell the lower continuous accelleration from the momentary bumps and impacts from day to day driving.


You're right, filtering out noise would be a part of the system design to avoid false breaks. This is easily done with a microcontroller and still quick enough of an average than human delay. MEMS-based accelerometers these days have very high "quality" factors in differentiating the different X, Y, and Z axes of movement. If mounted properly in the car, potholes should mostly affect Z, side acceleration (sharp turns) affect X, and Y should be your main axis of interest, for forward acceleration and deceleration (also easy to filter out negative acceleration for braking).

My current thoughts are that the device would have a "train mode" in which you set it at a few different points along your velocity. So, when it beeps to train it at 0mph, you floor it and it measures the max acceleration your controller can deliver. Now, cruising at say 35mph, you again floor it when it tells you to, and repeat for a final data point at 70mph highway cruising. Can do as many speeds as you want, and only do this once on a fresh charge, lightest load.

Once your in "use" mode, the microcontroller interpolates these measurements and only trips the system after a preset percentage above that. For example, at an acceleration of 20% over the recorded g's for that speed, it trips the breaker. Shock/bump/noise/time filtering all implemented through software.

I am going to try to build a prototype and see how it works. I can just hook it to my netbook and plot the g waves for all axes and see if it's working properly while riding in a regular ICE vehicle. 

*One last thing is nagging me about the idea: why is a manual killswitch needed at all?* Why isn't it enough to use a fuse/circuit breaker with a trip point of just over what your controller is rated for? For example, if your Curtis is rated at 500A for 100% throttle position, then a 700A breaker means controller breakdown at ANY speed, right?

Thanks everyone.


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## jackbauer (Jan 12, 2008)

Very simple solution to all of this which i have partly working in my car. Controller looks at motor current and throttle position and brake light switch. 

Scenario 1: The failed controller.
Cruising at say 50mph. Power section fails full on. Driver thinks "hmm we got a problem here" , lifts foot off go pedal. Controller sees massive motor current but throttle at zero and opens main contactor. Game over.

Scenario 2: The stuck accelerator.
Cruising at say 50mph. Accelerator sticks. Driver thinks "hmm we got a problem here" , lifts foot off go pedal. Applies brake pedal. Controller sees conflicting accelerator and brake inputs and opens main contactor. Game over.

I have the first scenario up and running in my car and i can simulate it with a jump lead across the controller. the second scenario will be hardware and software.

If you must have a manual disconnect then use an industrial mushroom head e-stop button linked to a kilovac contactor.


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## notailpipe (May 25, 2010)

jackbauer said:


> Scenario 1: The failed controller.
> Cruising at say 50mph. Power section fails full on. Driver thinks "hmm we got a problem here" , lifts foot off go pedal. Controller sees massive motor current but throttle at zero and opens main contactor. Game over.


What are you using to measure the current and do the comparison? A digital ammeter over your shunt working in tandem with a microcontroller? 



jackbauer said:


> Scenario 2: The stuck accelerator.
> Cruising at say 50mph. Accelerator sticks. Driver thinks "hmm we got a problem here" , lifts foot off go pedal. Applies brake pedal. Controller sees conflicting accelerator and brake inputs and opens main contactor. Game over.


Reminds me of the fixes Toyota is starting to put into their computer systems. If you were to accidentally hit both pedals at the same time (has happened to me), would you really want your car to die in the middle of the road? I guess "dying" is a loose meaning since you can just reset the killswitch and continue without having to start any engine.

That sounds like a pretty nice setup though. I guess the only thing I wanted different was I really want to eliminate all human parts of the equation, like driver realizing anything at all. If you're at an intersection and your controller fails, by the time you react you may already have been T-boned. Although if I'm understanding you correctly, it sounds like yours already takes care of this situation since throttle position is already at 0% when the controller fails, and kills it instantly.

Any ideas still on why you can't just set the current limit of your circuit-breaker to just over your full-throttle current? Am I missing something?


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## piotrsko (Dec 9, 2007)

notailpipe said:


> *One last thing is nagging me about the idea: why is a manual killswitch needed at all?* Why isn't it enough to use a fuse/circuit breaker with a trip point of just over what your controller is rated for? For example, if your Curtis is rated at 500A for 100% throttle position, then a 700A breaker means controller breakdown at ANY speed, right?
> Thanks everyone.


because sometimes you need to have a big sledgehammer powered thing to dead stop EVERYTHING, right now, no ifs, ands, or, buts. when everything else is operating within parameters and a runaway is occurring for some unknown reason, it is rather comforting to make it stop.


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## jackbauer (Jan 12, 2008)

notailpipe , the problem with using a breaker that trips out at over current seems fine in theory. In practice a 500amp breaker could pass say 700amps for several miniutes before tripping. 

I'm using a custom version of the open revolt controller programmed to do the safety checks listed above.

Worst case if you hit both pedals by mistake motor power is cut so just say "oops" and cycle the ignition and drive on.


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## Guest (May 28, 2010)

Jackbauer, Your modifications sound really great. Seeing as how you are working with an open revolt controller are you going to share you designs? I just spent some $s on new batteries for my car and some more $s on a motor and controller for another project so as soon as my accountant/wife stops fussing and tells me the bank account has stabled out I plan on purchasing an open revolt.


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## jackbauer (Jan 12, 2008)

Yeh any mods i do will be made available. I have quite a few so just need to clean up all the little pieces of stripboard onto a nice pcb. You can have a look at some of the videos on my website to see the basics.


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