Thread: Not a Ford but i thought i would share
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Old 31-05-2012, 10:35 AM
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purplecivicturbo
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Ive been so busy recently I havnt really been able to look at the civic, but I set a few hours aside the other day to finish the drive by wire..
Im not sure whether I mentioned it but I have moved away from my own throttle body design and decided to look for an OEM alternative.
I found an Audi RS4 throttle body in the same diameter as my own (76mm), cheap too.. I bought it. With some small modification of the hole sizes, I managed to get it to fit my intake manifold. Albeit needing allen head bolts for clearance..
I then modified my drive by wire controller to drive it directly. This is the result of the efforts;



As you can see, the throttle plate is unacceptably jittery.. This is because the motor is trying to seek the position at full speed (100% duty).
I decided to take the “chip enable” pin of the h-bridge IC, and connect it to the spare PWM pin of the PIC. This would work as a “chopper” circuit. I then designed an algorithm which would run the motor at full duty cycle but reduce the duty cycle the closer it got to the intended target position. By doing it like this there is no overshoot.
There is a scaling factor in the software which I can adjust to get the best balance between speed and jitter. In the video below it was set to 5, but afterwards I adjusted it to 10, and that was too far and the jitter came back.
Im going to have another fettle and try to bring it back tonight..
I can pretty much declare it finished now. And im rather happy, plus im using the dual pots in the Audi throttle to continuously perform self tests as to whether the system is working and whether both the sensors agree..

Last edited by purplecivicturbo; 31-05-2012 at 10:36 AM.
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