Winco DPG-2145-001 - Manual (Page 21)

Manual 36526F DPG-21XX-00X Digital Controllers
Woodward 13
by Decel Rate to decrease the engine speed from Set Speed A to Set Speed B in 1.5
seconds.
[(Set Speed A)
– (Set Speed B)] / (N seconds) = decel_rate_value in Hertz per second
[4170 – 3475] / 1.5 = 463 Hertz per second
3.16 Startup Rate (optional)
This parameter is used to achieve a smooth controlled engine start. On diesel engines,
this feature is also useful for minimizing exhaust smoke at startup. When used in
combination with the Idle Speed and Idle Hold Time, a brief warm-up cycle can be
programmed.
The startup rate specifies how fast the controller should increase the engine speed
when the engine is started. The rate value indicates Hertz per second. The formula to
use for determining a precise Startup Rate is shown below.
[(final_target_speed_in_Hertz) – (crank_speed_in_Hertz)] / (ramp_time_in_seconds) =
startup_rate_value
The ramp up will pause at the STARTUP SPEED until the controller senses an MPU
signal greater than the STARTUP SPEED. This prevents the startup ramp from
reaching completion before the engine has even started. The controller considers MPU
frequencies below the STARTUP SPEED as indicating that the engine is cranking but
has not yet started. MPU frequencies above the STARTUP SPEED are taken to
indicate that the engine has started and the controller will increase the engine speed
until the selected set speed is reached.
Exception: In cases where the target speed is less the STARTUP SPEED, the startup
ramp sequence ends when the target speed is reached.
When the NO. of FLYWHEEL TEETH parameter is used, the
ACCEL RATE, DECEL RATE, and STARTUP RATE
parameters are displayed as a RPM quantity per second
instead of Hz/sec values. The given rate formulas can be
used to compute rates in terms of RPM values by
substituting the Hertz speed values with RPM speed values.
3.17 Integral Low Limit (optional)
The integral low limit prevents "integral windup" in the negative direction. In other
words, the integral low limit parameter is used to reduce under speed duration after a
long or sustained over speed condition was present. The low limit helps reduce the
duration and amount of engine under speed by maintaining a minimum actuator
position.
When smaller pulse width modulated (PWM) duty cycle values do not reduce the
engine speed any further but an off speed (measured speed greater than the target
speed) remains, letting the Integral term grow more negative is not beneficial. Unused
negative integration would cause a slower recovery from an under speed condition.
The integral low limit specifies the PWM duty cycle where the integrator’s influence on
lowering PID output must stop. The default value is 0%. The value can be adjusted
from 0% to 90% in 1% increments.