30
Curtis 1212S Manual,
Rev. B
7
Adjusting IR compensation
The IR Comp parameter is used to set the percentage of the maximum motor
resistance that will be applied, i.e., (IR Comp)
×
(System Resistance), to com-
pensate for increased load caused by uneven terrain.
The trade-off in setting this parameter is that as ability to overcome load
disturbances increases, operating smoothness decreases. A high IR Comp value
will allow the vehicle to continue creeping at a low speed, even though it has
just contacted a bump in the threshold of a doorway. But if IR Comp is set too
high, it may make the vehicle “jumpy” during normal driving. Small throttle
movements in this case may no longer provide gentle linear acceleration, but
instead initiate accelerations with a sharp jerk. Therefore, the tuning goal is a
balance between adequate load disturbance response and normal acceleration/
deceleration response.
The normal range for IR Comp is approximately 50–80%. Larger numbers
provide stiffer, stronger response. If the value needs to be much larger or smaller
than this range to achieve acceptable performance, the System Resistance has
probably not been set up correctly and should be checked. Note: Largely different
settings for IR Comp will affect the maximum speeds that were set in Step 5.
Therefore, if you make large changes to IR Comp, you should repeat Step 5.
Just before stopping, when the throttle is in neutral, IR Comp is replaced
by Anti-Rollback Comp. Typically Anti-Rollback Comp is set about 20%
higher than IR Comp.
Assuming that System Resistance is set correctly (within 10–20%), some
general rules of thumb apply:
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-a. If the vehicle is extremely “jumpy” (i.e., responds abruptly to small
throttle changes, IR Comp could be set too high.
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-b. If the vehicle speed varies dramatically when cresting a hill, IR Comp
is most likely set too low.
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-c. If the vehicle rolls the other direction near the end of a stop on flat
ground, Anti-Rollback Comp is set too high.
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-d. If the vehicle is still moving on a modest ramp when the brake gets
set, Anti-Rollback Comp is set too low.
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-e. If the vehicle seems to decelerate to a stop in a nonlinear fashion,
Anti-Rollback Comp could be set too high.
6 — VEHICLE PERFORMANCE ADJUSTMENT
