Sooooo...
I am trying to get ideas for this personal project, I don't know exactly what it would entail, but I know it would be a large undertaking.
I wanted to get some opinions on how this could be done.
I will detail as much as possible, for those who might be unfamiliar, and also to show the extent of my knowledge also.

The idea/project, is to design an electronics module that will drive modern piezo injectors on a diesel engine.
There are a few different systems used by vehicle manufacturers, and even a few after market ones showing up.
Why not buy one?
I have a vision. My vision is to program the vehicle using an actual programming language, rather than software to map fuel tables, etc.
In other words, I want to run a truck on qbasic.
haha. ( and the ability to use and processor / programming language. )

So, in my head I have the project in 2 parts. (Or 2 sets of processing/ electronics.)
1. A module that runs at high speed, and does nothing but decipher timing signals and run injectors. I imagine this would be some types of RISC processors with PWM generators, and power amplifiers.
2. A module that runs at a much less reliable speed, and does absolutely everything else. This would be the one running the actual code. It would plug into the vehicles harness, and read all the temperature sensors, air flow sensors, talk to transmission controller, etc.

What I'm really interested in talking about, is module "1", the high speed timing / injector driver hardware.

Basically, it would be connected to 2 hall effect sensors; one is on the camshaft of the engine, and the system would need to count pulses to determine the engines position. There is an extra pulse I believe to get an absolute position on the wheel.
The 2nd hall effect sensor is on the crankshaft, and is just used to increase accuracy, I believe.

So this unit would need to read those 2 signals and determine what position the rotation is in, and also have some type of timer, so that it can calculate RPM.

Also, this module, would drive the injectors.
They are driven by PWM signals, up to around 80 volts I think, so a max of 100 anyways.
They are not just single pulses though, they are multiple pulses, up to 5 per injection.
So there needs to be some type of very fast PWM generator IC's there.
( and from the IC's, power amps?)

 

...

To clarify, the unit I'm talking about, would read 2 hall effect sensors, and drive 6 - 8 injectors, and also talk to the main unit over something simple like serial.
Let's call this the injector driver assembly. (IDM)
Let's call the other (main) unit the PCM (powertrain control module)
This is pretty much what it is in standard format from car companies haha.

So the IDM will know when to inject the fuel. It will have the hardware to inject the fuel, but thats it. ( yeah right, "thats it", huge project).

The PCM, will send over serial, little pieces of data to the IDM.
The pieces of data will include volume of fuel, etc.
Also, a good idea would be that if the communication fails for more than a second or so, the IDM would just turn itself off.


How do PWM chips work exactly?
I remember a few months ago thinking about this, and thinking of tiny chips that play back a sound from memory on the chip. I remember thinking...

"What I need is a chip like that for each injector, so when it's triggered to inject, it would play back it's sound (or injector driving PWM data), and drive the amplifier, driving the injector. "
Of course it would need to run at a much higher frequency than a chip meant for sound or music playing, but is similar technology possibly viable for this?



If the IDM was configured to not even adjust timing or anything, but just determine engine position, each injector driver circuit could have the above idea imlemented, and an amp, and the timing could just be changed by changing the data that gets "played back".
I will try to explain that better.
Let's think "like" the IDM for a second, controlling a single injector.

-We just got a signal from the hall sensor on the cam, this is the exhaust stroke.
-OK, another hall cam signal, this will be an injection, wait...
-Now signal detected from crankshaft, time to start injection data.
-Start playing PWM data from memory chip, voltages go to amplifier, and drive injector.

And the data on that chip, would be sent from the PCM, so the IDM could be a fairly dumb machine.
From the seat of the PCM,

-keep sending data over the serial to the IDM : "RPM", and it would send a number back.
-Then, we would send it injection pattern data constantly as the fuel demand changes.

I don't know the exact speed or bitrate etc that this might be, but for simplicity sakes, lets pretend that 30 degrees before top dead center, to 30 degrees after, is represented by something like this:
"0000000000000000000000000000000000000000000011111000000000000"

So when you send a serial message to the IDM, it would be something like:
"inject=0000000000000000000000000000000000000000000011111000000000000"
And that would be the data that the IDM "plays" to generate the PWM signals to the amplifiers, and then to the injectors.

So lets's pretend some more, rpm's are 2000, and throttle position is at 0 ( foot off gas pedal), the PCM would send this to the IDM:
"inject=0000000000000000000000000000000000000000000000000000000000000"

Then when the engine slowed down, the PCM would configure the injection pattern for idling, something like this:
"inject=0000000000001100000110000011000001100000011000000000000000000"
( That is 5 little shots of fuel.)

Harder fueling might look like this:
"inject=0000001111110001111110001111111110000011111100000111111000000"

And really hard fueling might not have enough time for 5 injections any more, so it could be 4 injections, 3, 2, 1, whatever.

The point is that the PCM can generate the injection pulse timing in with the injecion pattern, and the IDM will just keep putting out the signals it's told to, at the right time.

 

So thats what I'm really interested in as far as opinions, the IDM module.
A design that could accomplish the above theory, would allow a pile of possible processors to run the actual truck, but take a huge burden off of any such project.
It would create an easy platform for getting started.

The PCM would connect to the IDM via serial, or something similar and simple.
The PCM would connect to the truck through a connector pin-out coupler, and it would do things like adjust turbocharger position servo, change fuel rail pressures, etc etc, things that do not require the speed and accuracy of the injection system.

I'm thinking the PCM could be a processor board like a rasberri pi, or maybe an android style box, with a USB data acquisition board, and other various I/O expansions to drive servo's, run relay's, etc.


Sooooooooo

Think I'm insane yet?

 

Possibly parts of this product might contain some of this?

http://www.technobotsonline.com/scanalogic-2-20mhz-logic-analyzer-and-signal-generator.html

 

Now that was a lot of work for nothing

http://forum.allaboutcircuits.com/showthread.php?t=53904

 

Wow, sorry.

Where would one go to discuss this?

Most automotive forums aren't really geared towards this type of topic.

 

Hello,

I am closing this thread as it violates AAC policy and/or safety issues.

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