View Single Post
Old 05-29-2009, 11:52 PM   #93 (permalink)
Master EcoModder
JasonG's Avatar
Join Date: May 2009
Location: Charlotte NC / York SC
Posts: 728

05 DMax - '05 Chevrolet 2500HD
90 day: 18.48 mpg (US)
Thanks: 120
Thanked 55 Times in 51 Posts
Having a steady throttle setpoint may not be so good of an idea.
Removing the feedback loop from an analog circuit often causes undesirable results.
The very little part throttle needed to cruise on level ground can cause the vehicle to slow severely up a hill. While this can be corrected by a bit of right pedal, what happens when the reverse is true?
The vehicle will continue to accelerate downhill, possibly to a dangerous level.
A control circuits logic needs 3 parameters, a setpoint, a reference input and an analog output.
When watched on a graph, they get real funny when the input doesn't respond to the output. The PID gets more aggressive trying to make them match.
Given a reference that "behaves", as with the Ford MAP sensor, they will modulate correctly and "settle in" as tests show.

Readers Digest version: Controllers need real feedback not a faked signal or thay doan work so good.
  Reply With Quote