Throttle attenuator for an EV

[quince]

Removed.

[moffy]

Is the accelerator position proportional to speed or say motor current/power? I'm not sure how that works in an EV.

[SeanB]

There are throttle pedal adjusters, specific for a vehicle type, that act to change the law the sensor provides to the ECU. They read the 2 signals, and then use a small MCU to read the 2 pedal position voltages, one rising from 0V to Vref (typically 5V) as the pedal goes from released to flat to the floor, while the other is the exact opposite, so that the ECU can do sanity checking and prevent the runaway accelerator thing. They normally are going to do the opposite, providing a higher presented position according to some curve, but are quite capable of also limiting the max pedal position shown to the ECU instead, acting as power limiter.

[SteveThackery]

Is the accelerator position proportional to speed or say motor current/power? I'm not sure how that works in an EV.

Neither, almost certainly. It will just be one more input to the ECU, which will no doubt have sophisticated algorithms determining the motor current at that instance. I imagine all sorts of variables will be assessed: throttle pedal position, direction of movement and speed of movement; battery charge level; battery temperature; motor temperature; road speed; driving mode (sport, economy, etc); traction control setting; etc, etc.

[SteveThackery]

There's no chance that I would mess with such a safety critical sub-system. Also, it surely will invalidate your insurance.

[BrokenYugo]

Thinner sole shoes? Eco mode? An electronic throttle pedal is not something I'd mess with.

[langwadt]

Is the accelerator position proportional to speed or say motor current/power? I'm not sure how that works in an EV.

Neither, almost certainly. It will just be one more input to the ECU, which will no doubt have sophisticated algorithms determining the motor current at that instance. I imagine all sorts of variables will be assessed: throttle pedal position, direction of movement and speed of movement; battery charge level; battery temperature; motor temperature; road speed; driving mode (sport, economy, etc); traction control setting; etc, etc.

https://www.reddit.com/r/teslamotors/comments/inzuhz/model_3_factfinding_accelerator_pedal_position_vs/

[SteveThackery]

Is the accelerator position proportional to speed or say motor current/power? I'm not sure how that works in an EV.

Neither, almost certainly. It will just be one more input to the ECU, which will no doubt have sophisticated algorithms determining the motor current at that instance. I imagine all sorts of variables will be assessed: throttle pedal position, direction of movement and speed of movement; battery charge level; battery temperature; motor temperature; road speed; driving mode (sport, economy, etc); traction control setting; etc, etc.

This is technically true, but most of those variables are ignored beyond 20-30% throttle position. The throttle maps nearly linearly to torque with some smoothing near zero for reduced jerk. Below 20-30%, the computer does have to consider those variables to figure out what current to feed the battery in regeneration.

Seriously? The ECU ignores battery temperature and charge level? And the driving mode?? It's beyond 20-30% throttle when these really start to matter, surely!

Do you have a good reference book or online source where I can learn more about it?  I hope you aren't offended by my scepticism - it's just that I cannot conceive of any electric vehicle that doesn't monitor, and manage, the temperature of its batteries. This is burn-like-a-bastard lithium we're talking about.

[SteveThackery]

This site says it's legal:
https://issautomotive.com/blogs/throttle-response-controller/are-throttle-controllers-safe-learn-more

Legal doesn't mean it won't invalidate your insurance! These are completely different issues. At the very least you WILL be required to tell the insurance company.  They are so uptight these days you basically have to tell them about everything.

[inse]

“I will slow down the acceleration of my car“ - maybe this gives you a bonus…

[SteveThackery]

At the very least you WILL be required to tell the insurance company.  They are so uptight these days you basically have to tell them about everything.

They'll be notified, obviously!

It isn't obvious, although I'm pleased we are of like mind. Time on various car and motorcycle forums has shown me that lots of people don't notify their insurance company when making modifications.

[mikeselectricstuff]

  I hope you aren't offended by my scepticism - it's just that I cannot conceive of any electric vehicle that doesn't monitor, and manage, the temperature of its batteries. This is burn-like-a-bastard lithium we're talking about.

It isn't that it doesn't monitor these and apply limits where needed, just that they are not factored in when determining throttle response in normal conditions. I'm sure that once you're in turtle mode at 1% SoC, some limits will be coming in  to play, but I'd expect these would just be limits applied at the end of he control chain.

[langwadt]

do you fly out the window every time you hit the brakes? if not then apply the same finesse to the throttle pedal

[SteveThackery]

It isn't that it doesn't monitor these and apply limits where needed, just that they are not factored in when determining throttle response in normal conditions. I'm sure that once you're in turtle mode at 1% SoC, some limits will be coming in  to play, but I'd expect these would just be limits applied at the end of he control chain.

Do you have a source for the above information? So far it's just an assertion. I want to learn more. 

Also, it is surely going to include the driving mode in its calculation, because that is the driver's primary control over the throttle response.

[Andy Chee]

My solution is to cut the voltage increase (relative to zero throttle) by half as the throttle is applied. I've attached the OEM reference schematic, and a rough LTSpice simulation of my board.

Surely there is an existing software setting for this? rather than relying on hardware sensor trickery.

[robert.rozee]

i doubt that a driver would be much aware of the position of a foot throttle, but instead be more sensitive to the increasing pressure required as the throttle is pressed further down.

as such, my first approach would be to add a simple pullup spring, so that far more force is required once the throttle gets closer to the floor. you could even go so far as multiple springs with linkages so that as you get closer to the full throttle additional springs come into play, although i doubt this will prove necessary.


cheers,
rob   :-)

[SteveThackery]

That is the best suggestion yet. Nice one.

[SteveThackery]

My solution is to cut the voltage increase (relative to zero throttle) by half as the throttle is applied. I've attached the OEM reference schematic, and a rough LTSpice simulation of my board.

Surely there is an existing software setting for this? rather than relying on hardware sensor trickery.

Exactly! On my motorcycles it's called the "riding mode" and it alters the mapping between the twistgrip position and the throttle butterfly opening. It also alters the maximum rate of change of the butterfly's opening.

Do EVs not have such a thing?

[Monkeh]

My car has an especially peppy throttle. If I stomp it at a stop light it'll easily break the tires from the pavement.

So will my car, and it's not an EV, it's just a small diesel.

Stop stomping. Precise control of both (.. all three, in my case) pedals is a basic requirement of driving.

[BrokenYugo]

i doubt that a driver would be much aware of the position of a foot throttle, but instead be more sensitive to the increasing pressure required as the throttle is pressed further down.

as such, my first approach would be to add a simple pullup spring, so that far more force is required once the throttle gets closer to the floor. you could even go so far as multiple springs with linkages so that as you get closer to the full throttle additional springs come into play, although i doubt this will prove necessary.


cheers,
rob   :-)

I considered that suggestion,but this not being the old steel lever style I worry about wear, binding, outright failure, etc. adding springs to a pedal assembly I assume is made of a minimal amount of nylon.

[Andy Chee]

Surely there is an existing software setting for this? rather than relying on hardware sensor trickery.

...
Do EVs not have such a thing?

Not on my economy car! Gotta pay at least twice as much for a premium EV with the "non-hairtrigger throttle" setting.

Just to clarify, is this a homebrew DIY EV build?  Or is this an EV from a global manufacturer?

[tggzzz]

Can I check my understanding...

• cars are lethal pieces of machinery, that have killed and injured many people
• hence the cars and their operator and their operation are controlled by many laws, and those laws are enforced
• insurance is a legal requirement, and that requires clear statements that the cars are (or are not) roadworthy and unmodified
• you have a Chevrolet BOLT EV ?2023?
• it is difficult to control, either because you cannot control it or because the control setup is too aggressive
• you can pay more to have the car be more controllable. That implies Chevrolet is shipping a car that is, by default, too aggressive
• your solution is to add extra homebrew hardware to the car, directly between the throttle and the rest of the car
• your hardware will be temporarily connected using the existing connectors
• your hardware will modify the car's behaviour
• your hardware could equally easily make the car's control setup more aggressive rather than less aggressive

Point 6 is difficult to believe.
People are more likely to pay extra to have the option of making their car more fun to drive.
I believe there is a "hot-rodding" community that makes cars more aggressive and "fun" to drive. See point 10.
Such hot-rodding probably invalidates insurance and manufacturer's warranties.
If such hot-rodding is detected (e.g. after warranty claim or accident) then the owner has a Big Problem.
Being able to remove the evidence of hot-rodding, e.g. using a temporary removable fitting would be advantageous in that respect.

Comments?

[uer166]

Comments?

I used to work for a major EV manufacturer in engineering, this entire thread and an assertion that adding a mod board to a pedal control loop is somehow "safe" is absolutely ridiculous. OP: either replace car or get used to the pedal response, the chance of you killing or maiming someone else is way too high.

[tggzzz]

Comments?

I used to work for a major EV manufacturer in engineering, this entire thread and an assertion that adding a mod board to a pedal control loop is somehow "safe" is absolutely ridiculous. OP: either replace car or get used to the pedal response, the chance of you killing or maiming someone else is way too high.

Just so.

I wonder if "quince" has somewhat, ahem, different objectives to the ones he has stated, hence his preference that he doesn't want "Chevrolet BOLT EV" to be searchable viz:

It's the EV named in the pedal pinout PDF in the first post. Given that this hardware is untested, I would rather it not be searchable yet.

[tggzzz]

Thanks for continuing to participate in the thread, folks.

you can pay more to have the car be more controllable. That implies Chevrolet is shipping a car that is, by default, too aggressive

The OEM acceleration is too aggressive. You should try one. In the EU/UK they're known as the Opel Ampera-E.

OP: either replace car or get used to the pedal response

If I had $40,000 laying around to buy a car with the Chill Mode feature, maybe I would.

You mean you didn't test drive a car before buying it? Strange, and not what I would expect from an engineer.

your solution is to add extra homebrew hardware to the car, directly between the throttle and the rest of the car

It does exactly what Tesla's well-known and celebrated "chill mode" feature does. It imitates part of "snow mode" in an Ioniq.

your hardware could equally easily make the car's control setup more aggressive rather than less aggressive

Only if you expect me to solder the resistors in backwards and also fail to do any verification & validation.

Conclusion: either you are someone that doesn't have the first clue about how components and circuits work, or you are a troll, or both.

People are more likely to pay extra to have the option of making their car more fun to drive.
I believe there is a "hot-rodding" community that makes cars more aggressive and "fun" to drive. See point 10.
...
Being able to remove the evidence of hot-rodding, e.g. using a temporary removable fitting would be advantageous in that respect.

Comments?

The only way to make a Bolt faster is to sell it and buy a Tesla. Steepening the throttle curve genuinely would achieve nothing. I love the conspiratorial tone, but I use my car for transportation and have no interest in making it more "fun."

Millions of cars have their speeds and throttles limited by aftermarket kits. I could probably buy one of those... perhaps I will!

https://www.rostra.com/how-to-add-speed-limiter-to-a-vehicle.php

https://www.avsgemini.com/speed-limiters.html

They're even all over Amazon: https://www.amazon.com/rev-limiter/s?k=rev+limiter

There are all sorts of dangerous and illegal things "all over Amazon".

In the UK there are many things which are legal to sell but illegal to operate. I learned that in 1972 w.r.t. some types of radios.

I now see such things every day on the roads, and they kill/injure hundreds of innocent passers by every year.

Such hot-rodding probably invalidates ... manufacturer's warranties.

Warranty expired already, mate.

Is the insurance also expired? The insurance is almost certainly invalidated, so when you hit someone they will suffer the health consequences and financial consequences of not getting a financial settlement.

That's selfish in the extreme.

This is correct:

Comments?

I used to work for a major EV manufacturer in engineering, this entire thread and an assertion that adding a mod board to a pedal control loop is somehow "safe" is absolutely ridiculous. OP: either replace car or get used to the pedal response, the chance of you killing or maiming someone else is way too high.