Question

2. How to obtain the necessary process data by step response testing?

Answer 1

A step response test can be conducted on a system to collect all the necesary data to model the system. The test can be conducted as follows:

• Let the system come at a steady state initially and note down the parameters and response of the system at the initial steady state.
• Introduce a step input in the form of heat, electrical signal or any other form that is appropriate for the system
• At regular intervals of time, note down the response of system. The response of the system can be observed through various instruments. If the response is in form of heat energy, thermometer can be used to observe the change in the response of the system as the system is deviated from the initial steady state using step input. Similarly, a voltmeter, a galvanometer, a flowmeter, etc. can also be used depending upon the type of system response.
• Collect the step response data until the system comes back to a steady state. In case, the system takes too long to come back to the steady state, the data collection can be stopped after the change in the response becomes very small.
• The [Response] vs [Time] data can then be plotted on a graph using Spreadsheet, MATLAB or PolyMath and a best-fitting mathematical model can be obtained using the same mathematical software. The mathematical model should represent the response data accurately and as closely as possible.
• To check whether the data fits in the model almost perfectly, different statistical indicators such as R² value, Mean Squared Error (S), etc. can be checked.