Loading the Compensation Table

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
Y 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.