MSD 7562 Programmable Launch Boost Controller Installation - Manual (Page 13)

INSTALLATION INSTRUCTIONS 13
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TEST EXAMPLE 3 - FIGURE 8
The following examples illustrate PID values that are not optimized. Figure 8 shows a PID setup that
has large swings of the PWM value resulting in saturation of the PWM. The saturation occurs when
the PWM swings from full closed, increasing boost at PWM=40, to full open, decreasing boost at
PWM=159. Also the time that was spent at the extreme PWM values of 40 show that this PID setup
had too much P term. The P term should be lowered until the PWM does not reach the saturation
levels for more than instant during any part of the run. Here the P term needs to be changed about
–10 to –20 lower and then retested. If the PWM stays out of saturation the valves are quicker
responding and the pressure regulation will have less ripple. Note that when the P term is lowered
the D term will appear larger and may cause the rising edge of the boost pressure curve to step up
or slow down. With this, it is always best to decrease D term along with decreasing the P term.
Once the boost pressure is near optimum work on making adjustments to optimize D after P
changes have been made. Do not add any I term until the P and D terms have been optimized.
Figure 8