Mach-DSP User’s Manual
Document Number: MACH-DSP-9021
Page 81
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P.
Continue to increase Servo Gain, Low Frequency Damping and High Frequency
Damping, each one a little bit at a time, while keeping overshoot to a minimum and
also while watching the Error signal (Oscilloscope Blue Trace C). The point at which
the Error signal goes to zero (i.e. meets the middle of the vertical display) indicates
the step response time of the system. Increase Servo Gain if you want to decrease
the step time of the system; then increase the damping controls to eliminate
overshoot. This is an iterative process.
9.3
Position Offset and Position Scale
Q.
Set the Test Signal Generator to generate a sine-wave instead of a squarewave.
This will change the projected image to a circle. Then change the amplitude of the
Test Signal Generator to 0.01 degrees. This will produce an incredibly small scan,
while still eliminating the Command Input signal.
R.
Position the scanners in the X-Y mount such that they are projecting as closely as
possible to the center of the projection surface. (It may be impossible to achieve a
true center with simple mechanical adjustments of the scanner. Fine-tuning will be
done in the next step.)
S.
Click on the Advanced tab, then click on the X or Y button. This selects an individual
axis to be adjusted instead of adjusting both axes together. Adjust the Position
Offset control on the Advanced tab to center the projection on both the X and Y axis.
T.
Set the amplitude of the Test Signal Generator to produce the desired maximum-
sized projection. For example, if you are trying to ultimately accomplish a 40-degree-
optical projection angle, set the Test Signal Generator amplitude to 20 degrees.
(Remember, the Test Signal Generator and all other angles specified in the Mach-
DSP program use mechanical degrees, and the optical angle is twice the
mechanical angle.)
U.
Adjust the Position Sensor Scale on the Advanced tab, to increase or decrease the
size of the projected circle, as needed to accomplish the desired projection angle,
according to the scale on the projection surface.
