Elmo SSA Series - Velocity Response Optimization

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SSA - Rev 6/98
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In most applications optimum response is achieved by adjusting the compensation
(COMP) trimmer. Adjustment procedure is as follows:
- Provide the amplifier with a low frequency, bi-directional square wave velocity
command (A 0.5Hz, ±2V waveform is often employed).
- Apply power to the amplifier, and while monitoring the tachometer signal,
gradually adjust the COMP trimmer from the CCW toward the CW position.
Optimum response (critically-damped) should be achieved at some position
before reaching full CW on T1. Fig 8.1 illustrates the types of waveforms
observed for various setting of T1.
In some applications, especially those where the load inertia is much smaller
or larger than normally encountered, the standard compensation components values
of 0.033µF for C3 and 470Kohm for R12 may not allow an optimum setting of the
COMP trimmer T1. In fact, the velocity loop may be unstable for any setting of
T1.
In these cases different values for C3 and R12 must be chosen. The following
procedure can be used to select these values:
- Short circuit C3 with a short jumper wire.
- Replace R12 with a decade resistance box. Initially set the box resistance at
20Kohm.
- Set T1, the COMP trimmer to approximately midrange.
- Input a 0.5Hz, 2V bi-directional square wave velocity command signal to the
amplifier.
- Apply power, and while monitoring the tachometer signal, gradually increase the
value of the box resistance until optimum response as depicted in Fig 8.1 is
achieved.
- Substitute the closest standard value discrete resistor for R12 and remove the
decade resistance box.
- Remove the shorting jumper across C3, and again check the response using the
squarewave test signal. If near optimum results are obtained, trim the
response using the COMP trimmer T1 for the optimum.