Dynamic DX Power Module PMB Installation Manual page 46

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The following parameters are normally set up for a particular wheelchair type,
rather than for a particular wheelchair user.
Load compensation
Load Compensation is the name given to the Power Module's ability to
maintain a constant speed regardless of changing motor loads. This is
particularly useful for slope/kerb climbing, turning on certain surfaces, cross-
slope driving, and many other situations in which the motor load changes. It
also affects the PM's ability to prevent the wheelchair rolling down a slope
when starting or stopping.
The speed of a motor changes as a result of the combined resistance of its
windings/brushes and the wiring from the controller to the motor. The poorer
the quality of the motor and/or its associated wiring the more speed variation
with load, and the greater the need for load compensation by the controller.
The PM has a programmable Load Compensation parameter, expressed in
terms of milliohms of resistance that it has to compensate for. High quality
motors may require a Load Compensation value of 50 milliohms while a poor
quality motor may require as much as 300 milliohms. The default Load
Compensation value is zero as it is safer to err on the low side.
Warning : When programming this parameter, a value lower than deemed
necessary should be trialed before programming higher values.
It is extremely important to get the value of load compensation correct for the
motors used. Entering a lower than optimum value will give sluggish and load
dependent performance which will be tiring for the driver, while entering a
higher than optimum value will give a jerky performance which will be hard
to control and potentially dangerous. The Load Compensation should be
determined based on the motor manufacturer's data and appropriate motor
resistance testing.
For the PM-S, the actual Load Compensation at the drive motor is half of the
value of the Wizard Load Compensation parameter. (The HHP displays the
true value as seen at the motor).
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