January 2012 6.16 The Control Loop 921
If the path traversed deviates at the reversal point from the nominal path,
first toward the outside and then toward the inside, the compensation is
performed too late. In this case, you must decrease the value in
MP_compTimeOffset.
With the following formula you can estimate the magnitude of useful values
for the MP_compTimeOffset parameter:
It is easier to adjust the MP_compWidth and MP_compTimeOffset
parameters at low feed rates. HEIDENHAIN recommends:
First roughly adjust MP_compStrength.
Then select a low feed rate.
Then set MP_compWidth and MP_compTimeOffset.
Return to the original feed rate and optimize the value for
MP_compStrength.
You use these three parameters (MP_compStrength, MP_compWidth,
MP_compTimeOffset) to adjust the compensation of reversal peaks for a
specific feed rate and radius. Under certain circumstances, however, it can be
necessary to correct the compensation strength based on the feed rate.
Proceed as follows:
Switch to the Oscilloscope mode of operation.
Set the following value in the oscilloscope by pressing the SELECTION soft
key:
Display mode: YT
Sampling time: IPO clock
Channel 1: A nom
Trigger: Free run
Press the OSCI soft key to switch to the curve representation.
Now get the nominal acceleration for the axis (A nom) at the reversal point
for the feed rate that you have selected for the adjustment up to now.
Press the START soft key to start recording.
Press the axis-direction key of each axis.
Press the STOP soft key to stop recording.
Enter the determined acceleration in the parameter MP_compRefAcc.
Now use the parameter MP_compFFAdjust to correct the compensation
strength for lower or higher feed rates.
compTimeOffset 2accleration[]compWidth⋅⋅ 6⋅=
The oscilloscope shows mm/s
2
, but the unit of the parameter is m/s
2
. This
means that you must divide the value by 1000.
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