.

Next we need to somehow acquire high precision distance measurements (via interferometer, etc.) to the surface at each of the X-Y locations in the compensation area, and store the X and Y offset positions.

Once you've obtained these positions, they will need to be loaded into our previously configured compensation table (See Determining Required Compensator Table Size). Continuing with our original example let's assume that our measurements are as defined by the following table below (taken from the comp.c sample application):

 double compensatorTable[21][5] = { { 0, 0, 0, 0, 0, }, { 100, 200, -200, -100, 0, }, { 200, 400, -400, -200, 0 }, { 300, 600, -600, -300, 0 }, { 400, 800, -800, -400, 0 }, { 500, 1000, -1000, -500, 0 }, { 600, 1200, -1200, -600, 0 }, { 700, 1400, -1400, -700, 0 }, { 800, 1600, -1600, -800, 0 }, { 900, 1800, -1800, -900, 0 }, { 1000, 2000, -2000, -1000, 0 }, { 900, 1800, -1800, -900, 0 }, { 800, 1600, -1600, -800, 0 }, { 700, 1400, -1400, -700, 0 }, { 600, 1200, -1200, -600, 0 }, { 500, 1000, -1000, -500, 0 }, { 400, 800, -800, -400, 0 }, { 300, 600, -600, -300, 0 }, { 200, 400, -400, -200, 0 }, { 100, 200, -200, -100, 0 }, { 0, 0, 0, 0, 0 }, };

Interpreting compensator table above:

To compensate a Z (vertical) axis for X-Y surface irregularities, first define the X-Y area to be compensated (Xmin to Xmax, Ymin to Ymax).

Then define the spacing of the measuring points (delta) for the X and Y axes to determine the compensation table size.

For the X-Y table diagram below we have:
Xmin = 0, Xmax = 200000, Xdelta = 50000
Ymin = 25000, Ymax = 225000, Ydelta = 10000

 Y Values X Values 0 50000 100000 150000 200000 25000 0 0 0 0 0 35000 100 200 -200 -100 0 45000 200 400 -400 -200 0 55000 300 600 -600 -300 0 65000 400 800 -800 -400 0 75000 500 1000 -1000 -500 0 85000 600 1200 -1200 -600 0 95000 700 1400 -1400 -700 0 105000 800 1600 -1600 -800 0 115000 900 1800 -1800 -900 0 125000 1000 2000 -2000 -1000 0 135000 900 1800 -1800 -900 0 145000 800 1600 -1600 -800 0 155000 700 1400 -1400 -700 0 165000 600 1200 -1200 -600 0 175000 500 1000 -1000 -500 0 185000 400 800 -800 -400 0 195000 300 600 -600 -300 0 205000 200 400 -400 -200 0 215000 100 200 -200 -100 0 225000 0 0 0 0 0

To load the above compensation table, execute the following code:

 returnValue = mpiCompensatorTableSet(compensator, compensatorTable);

Once the compensation positions are loaded, the compensation will be applied to the Z-axis' position feedback loop every servo cycle.

NOTE: No more interpolated compensation of the Z-axis will occur outside of the defined compensation range. Therefore, the compensation of the Z-axis will remain fixed outside of this range.

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