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5.12.4 Synthetic
Pre-Torque
Synthetic pre-torque is a feature of the drive which can be used to minimize, if not
totally eliminate, the roll back which normally occurs when the brake is lifted.
The function is turned on in parameter LF.30 and adjusted in parameters US.17 &
US.18 and P.LF.31 & P.LF.32. The following procedure will assist in the adjustment
of the pre-torque.
Adjust brake spring tension, brake voltage, and brake timing  rst. Note, that
it is often advantageous to use lower spring tension and lower brake pick
voltage to provide a softer lifting of the brake. This allows for a smoother
transition from brake to motor. It should be noted that any subsequent
changes to the brake could require readjustment of the synthetic pre-
torque.
1) Set the speed to zero in order to clearly see the rollback.
2) Run the car on inspection and note the roll back.
3) Turn on the synthetic pre-torque by setting LF.30 = 5. Also adjust US.17 = 0.2
sec. and US.18 = 0.2 sec.
4) Run the car on inspection. If there is any vibration or audible noise at the start,
lower the value of P.LF.32 by 2500 and try again.
5) Increase the value of US.17 by 0.05 sec. If the rollback is reduced proceed to
step 6, otherwise continue raising the value of US.17 again by 0.05 sec until a
difference in the rollback is perceived.
6) Note the value of US.17 and raise it again by 0.05 seconds. If the roll back gets
better try raising it again. Keep raising US.17 until it gets worse again. Then back
off the value by 0.05 sec. Note there may still be some rollback at this point.
7) Increase the value of P.LF.32 in steps of 2000 and run the car. Roll back should
be further reduced. Values as high as 20000 are normal. If there is vibration or
audible noise at start reduce P.LF.32. In some cases it may help to raise the value
of P.LF.31 to minimize vibration during the pre-torque phase. Adjust in steps of
1000. Finally reduce US.18 by 0.05 seconds.
8) Return the pattern gain or inspection speed to the previous values.
9) Run the car on automatic.
i
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