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6. As needed, adjust the Slew Rate Limiter Adjustment trimpot, R78, CW to slow the maximum

slew rate of this large angle square wave as needed to keep the +Motor voltage from

"squaring off' or saturating at the top of the first peak. Figure 16 shows this squaring off

phenomenon. Slowing down the input signal will increase the large-angle step response time.

However, the best setding performance will by achieved when the output amplifier is not

allowed to saturate. To ensure the output amplifier will not saturate even after the scanner

reaches its maximum operating temperature, use the following formula for setting the

maximum voltage on +Motor during the step:

+Motorpeak = (+|Drive-2V)/1.3 where: +Drive = Input power to the servo card

Note: In the example above, the +Drive = +28V, thus +Motor peak = 20V.

Depending upon motor impedance, load inertia, system tuning, power supply

voltages, etc., the max output amplifier current of +/- lOA may be reached prior

to voltage saturation.

Keep tuming R78 until the +Motor peak is at the desired level as given by the above

formula. See

figure

17.

Chi

•

10V'

CMlSmsExt/i6/ 1.58V

Figure 17.

FigurelS.

Iterate steps 5 and 6 until the maximum angle for the system configuration is reached. See

Figure 18.

If the Command Input Scale Factor is set so that the fieldsize ofthe system is less than the fiill

+/-20° mechanical, then the position output, Vp, will not tiavel the whole +/-I0volts. Since the

slew rate limiter sometimes affects the small angle response slightiy, go back to section

6.1.7.1.2. to check that it the system is still critically damped.

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Axis 670 Bedienerhandbuch Seite 41