Automotive electronic throttle control

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Mhm
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Automotive electronic throttle control

Post by Mhm » Thu Feb 16, 2012 4:08 am

Could anyone help me with some code to control a drive-by-wire throttlebody.

It has a DC motor so I assume PWM would be used to control it.
It also has an potentiometer connected to the butterfly that can be used for feedback.

I'm new to programming, so would appreciate some help on this.

fll-freak
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Re: Automotive electronic throttle control

Post by fll-freak » Thu Feb 16, 2012 5:22 am

You may find it tough to find someone. With the liability issues of writing software that could end up killing someone, I would not be keen to help. Just look at poor Toyota and it was 'proven' latter the sudden acceleration was not even real.

skimask
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Re: Automotive electronic throttle control

Post by skimask » Thu Feb 16, 2012 6:33 am

DBW throttle body using PWM?
I don't think so...

Ya, I'll write some software for you...and put a nasty "bug" in there that'll activate itself in case I don't get paid.

Sounds like the beginnings of a movie...
I ignore "one post wonders".

Mhm
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Re: Automotive electronic throttle control

Post by Mhm » Thu Feb 16, 2012 7:23 am

skimask wrote:DBW throttle body using PWM?
I don't think so...
If PWM is not used how is the DC motor controlled then?

It's definately got a DC motor, I have tested it!

When you apply DC power to the motor terminals on the TB the butterfly opens.

Mhm
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Re: Automotive electronic throttle control

Post by Mhm » Thu Feb 16, 2012 7:33 am

fll-freak wrote:You may find it tough to find someone. With the liability issues of writing software that could end up killing someone, I would not be keen to help.
What I want to do is control the idling and eventually control the revs to the to match the gearbox speed when changing gears.

The TB that I have is not a 100% drive-by-wire. The butterfly is still operated by cable, but it also has a motor to operate the butterfly to about 40% opening for idle control.

fll-freak
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Re: Automotive electronic throttle control

Post by fll-freak » Thu Feb 16, 2012 7:53 am

I would guess than the first step is figuring out exactly how the motor on this thing works. If you remove power to the motor, does it return to some start state or does it just stay were it last was? You have any spec sheets on this? Anyone else do something like this that you might be able to leverage? And websites devoted to this activity? Not suggesting I would directly help, but rather asking you questions that might get you the information and help you need.

Mhm
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Re: Automotive electronic throttle control

Post by Mhm » Thu Feb 16, 2012 8:10 am

Don't have any spec's or anyone that I could ask for help. That's why I'm asking here.

As stated, I've tested the motor and it does return to the osed position when power is removed.

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Re: Automotive electronic throttle control

Post by fll-freak » Thu Feb 16, 2012 8:28 am

Do you have a manufacturer and or a part number?
Since I know nothing about cars other than they normally have four wheels, is a motor controlled butterfly a normal thing?
If not, where did you get it?

When you apply power, does it snap or slowly open?

Edit: After Goggling a bit, I found several patents and an IEEE document on an optimal way to control said device. Also lots of procedures for calibrating a replacement and even spare parts from AutoZone. All that was on the first two pages of the search "throttlebody motorized"

skimask
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Re: Automotive electronic throttle control

Post by skimask » Thu Feb 16, 2012 3:23 pm

fll-freak wrote:Since I know nothing about cars other than they normally have four wheels, is a motor controlled butterfly a normal thing?
It's getting to be a "normal" thing these days.

Quick, short, not all inclusive explanation...
In an old school engine, the throttle plates were controlled by your foot. Case closed. No matter what the valves were doing. A lot of energy is wasted in an internal combustion engine by sucking in air past the intake valves...called "pumping losses".

With today's engine have variable valve timing, the valves can open and close at different times during their cycles. For example, the intake valves can open up a bit earlier or later and if you've got the throttle plates open a bit more, there would be less work expended as the piston goes down and sucks in air.

So, with a drive-by-wire throttle, the computer can set the valve timing so the intake valves close a bit early so each cylinder doesn't try to suck in as much air (or they can close a bit late and pump some of that air back into the intake), and at the same time, open the throttle plates a bit more to make sucking in that bit of air a tad easier.
In effect, this action makes the engine act as if it's a smaller displacement engine, because it's using less air per stroke as compared to an engine with none of these enhancements.

If you want to check it out further, google "atkinson cycle" and "miller cycle" and "otto cycle". The wiki articles aren't too bad.
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Re: Automotive electronic throttle control

Post by Mee_n_Mac » Thu Feb 16, 2012 6:28 pm

Mhm wrote:What I want to do is control the idling and eventually control the revs to the to match the gearbox speed when changing gears.

The TB that I have is not a 100% drive-by-wire. The butterfly is still operated by cable, but it also has a motor to operate the butterfly to about 40% opening for idle control.

...

As stated, I've tested the motor and it does return to the osed position when power is removed.
So if a spring closes the valve when power is removed from the "motor" then it's not so much what I'd call a motor but rather an actuator. That is the motor doesn't spin but the device exterts a force on the valve, against a spring, until the valve opens enough to achieve the desired idle RPMs. It might not be controlled via a PWM method but rather through some current control like a normal feedback loop. If it is then it may or may not respond well to a PWM type signal. Hard to tell w/o trying so I think you'll need to do some experimentation if you can't find the documentation specific to your TB.

FWIW I don't see you achieving rev matching using this. If it can only open the TB some 40%, is that going to be enough to get the RPMs needed on a downshift that's likely to be near redline ? Granted the engine isn't under load but ?? Don't unlearn heel'n'toe just yet. :mrgreen:

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Re: Automotive electronic throttle control

Post by fll-freak » Thu Feb 16, 2012 7:50 pm

After looking at the patents that are in place,these are indeed small electric motors that wind up a return spring as they open the valve. Killing power puts the valve in a safe mode. So on a small scale they are motors, but on the bigger picture they are like actuators. How they are control is a bit of a mystery although I did see a reference to an H-Bridge on one website devoted to Ford systems.

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Re: Automotive electronic throttle control

Post by Mee_n_Mac » Thu Feb 16, 2012 8:47 pm

I would ask how the motor is geared to the butterfly valve. If the gearing is 100 revs of motor to get 1 deg of valve motion then I'd expect the control loop to be some type of bang-bang system, like your home heating is. The motor is acting like a motor (has back EMF) and turned on full blast. It winds the valve into position and then turned off. The valve tends back towards closure and at some point the motor is turned on again to restore the valve to the desired position. The result is the valve flutters ... and perhas your idle does too. I guess if this all happens quickly enough, it averages out so you don't notice it (and/or your engines inertia filters it out).

If the gearing is substantially less then I'll opine the motor is always on but effectively stalled (which to me is actuator-like), with the torque needed to offset the spring controlled either by the instantaneous current or perhaps by PWM'ing the motor so the average current is right.

Use of an H-bridge would suggest a more motor-like system and that the spring is relatively weak. Closure upon removal of power would be "slow".

I wonder which way would be less $$s ?

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Re: Automotive electronic throttle control

Post by skimask » Fri Feb 17, 2012 8:33 am

fll-freak wrote:After looking at the patents that are in place,these are indeed small electric motors that wind up a return spring as they open the valve. Killing power puts the valve in a safe mode. So on a small scale they are motors, but on the bigger picture they are like actuators. How they are control is a bit of a mystery although I did see a reference to an H-Bridge on one website devoted to Ford systems.
Good call. I didn't realize that's how some of those are made.
The only Drive-By-Wire TB actuators I've seen are direct drive stepper motor types and they also have a 'return spring' on them. If they lose power on the coils of the actuator, the motor becomes limp and the plates drop back to closed.
I ignore "one post wonders".

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