SuperFlow AutoDyn, Руководство оператора

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Control Modes
11-12 AutoDyn Chassis Dynamometer Operator Manual
seconds. Since the I-term is an integrated value, integrator wind-up can occur if the I-term is
“turned on” over too wide a bandwidth. The I-Threshold parameter is used to adjust this
bandwidth and prevent the integration from creating too much gain due to a large error
signal. The I-Time parameter allows the system to integrate the error signal over a longer
period of time to create a smoother gain signal. You could use this parameter to force the
system to smooth through a random, erratic change in the error signal.
Usually it is easiest to start the PID adjustment with the integrator turned off (value = 0). After
refining the P- and D-Term, the system should respond properly and stabilize properly.
However, it may not actually reach the desired set point.
11.5.6 I-Threshold
Allowed values:
Any floating point value
This value is associated with the control channel, i.e., rpm or mph.
Determines bandwidth for integration of the error signal.
Suggested Value Range
• At least large enough to capture the control channel offset due to the P-Term for engine
dynos (usually around 1000 rpm or less)
• At least large enough to capture the control channel offset due to the P-Term for chassis
dynos controlling to vehicle speed (usually 5-10 mph)
• Suggested setup prior to adjustment: must be some value other than zero, as a zero will turn
off the integrator completely.
What it Does
The I-Threshold parameter specifies the range from the set point where the I-Gain will
function. For example, with an I-Threshold of 300 rpm and a set point of 1500 rpm, the I-Gain
would be active from 1200 to 1800 rpm (the magnitude of the error must be 300). Further, if
the P-Gain does not bring the speed within this range, the I-Gain will not become active and
the speed will never reach the set point. In other words, the Integrator Threshold determines
the window within which the Integrator takes effect. This means the I-Term will only become
operational when the actual value enters a window of “set point ± I-Threshold.”
The integrator should take effect when the P-term and the D-term lower the error term as
much as possible. This is very useful for limiting the integrator output while the control
system is in a major transitional phase, i.e., a transition from no load to the first set point.
Furthermore, if the I-Threshold were set to zero, then in essence, the integrator would always
be turned off.
The integrator term tends to slow down the system response by stabilizing the control
algorithm as the set point approaches. On systems with lots of system inertia (slower
response) such as a chassis dynamometer, the integrator should only become active when the
control channel value is relatively close to the desired set point.
Suggested Adjustment Technique
To set the I-Threshold, observe the difference between set point and engine/vehicle speed
during the above P-Gain adjustment. Double this rpm (or mph) value and enter it as the
I-Threshold. This is not a critical adjustment; if this number is too small, all that happens is the
engine does not load down the final portion of the way to the desired rpm, and the system
will never reach its set point.