Several of the important dynamic systems in a rolling mill can be tested by what the controls field terminology calls the “step input” test. The output of this test is called the frequency response of the system where it reveals how fast the system responses to disturbances. In this test usually a square wave is used to simulate disturbances that may happen during the production. The square wave is injected into the system and the system’s response time will be measured. Observation is also made whether the form of the transient response is appropriate. Step input testing is an excellent way of characterizing the speed and tension controls (slow or fast) and it can be used in PID tuning. Therefore, the two common mill systems (among many) to be checked this way are:

 

• Drives and the mill speed controls
• Thread tension controls
• PID tuning

For a summary of our control analysis capabilities please see our  Modeling/Analysis of Control Systems section.