.

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
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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