Feedback controller parameter generation with stability monitoring

1. A method of confirming stability of a control system for a materials testing system using specified filter parameters, the method comprising:

inputting to the control system a test signal having a predetermined waveform;

automatically monitoring an output of the materials testing system;

automatically comparing the output to a threshold;

if the output exceeds the threshold, taking a first action to avoid unintended damage to one or more of a sample to be tested and the materials testing system; and

if the output does not exceed the threshold, taking a second action in the form of permitting input to the control system of a command signal.

2. The method of claim 1 wherein the test signal comprises two square waves.

3. The method of claim 2 wherein the square waves have a frequency of 1 Hz.

4. The method of claim 1 wherein the test signal comprises an amplitude attenuated version of the command signal.

5. The method of claim 1 wherein the test signal comprises a waveform matching a waveform of the command signal and having an amplitude of 95 percent of an amplitude of the command signal.

6. The method of claim 1 wherein the threshold varies with the test signal.

7. The method of claim 1 wherein taking the first action comprises stopping operation of the control system.

8. The method of claim 1 wherein taking the first action comprises:

determining a transfer function of the materials testing system, the method of claim 1 further including:

computing parameters for filters of the control system;

loading the computed parameters in the filters; and

repeating the steps of claim 1 .

9. The method of claim 8 wherein computing the parameters comprises convolving the transfer function with the filters to produce the parameters.

10. A method of determining filter parameters for a control system, the method comprising:

generating a random noise signal;

applying a low-pass filter to the random noise signal to produce a first filtered signal;

applying a high-pass filter to the first filtered signal to produce a second filtered signal;

superimposing the second filtered signal on a sinusoidal waveform to produce a reference test waveform;

applying the reference test waveform to a system under test;

measuring an output of the system under test;

determining a transfer function of the system under test; and

convolving the transfer function with the low-pass and high-pass filters to produce the filter parameters, whereby use of the filter parameters in the control system avoids unintended damage to one or more of a sample to be tested and the system under test.