Common control parameters for Aspen dynamic simulation
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This post was last edited by bananaaspen on 2011-1-19 at 14:10. Could everyone list the approximate initial values for the PID control parameters? For example, parameters for controlling the temperature of the sensitive plate or the reactor temperature. The control parameter for regulating the feed flow rate – I think this is a really trivial issue. Put it another way: for example, if you want to create a control simulation of a tower, how do you determine these control parameters?
Statistics show that over 40% of process control is related to flow rate; therefore, flow rate control is of primary importance. When using a PID controller for flow rate control, a PI controller is usually employed, as flow rates respond relatively quickly, and differentiation can amplify noise. Pressure control is similar to flow rate control. Due to the significant delay associated with temperature control, it is generally suitable for PID controllers in order to reduce the response time; component control is similar to temperature control. Level control is generally simple; proportional controllers are sufficient for equipment that is not critical. For applications requiring more precise level control, such as in reactors, PI controllers can be used. As for how to set these parameters, initial values are generally determined based on experience, followed by online tuning. HYSYS comes equipped with an online tuning tool called Autotuner, which is available on the controller page; it uses a relay-based method for online tuning. As for the principle behind this? It can’t be explained in just one sentence; go and look up relevant information on your own – you’ll have a lot of fun doing that.
Reply to 2# lsrwan: Thank you, expert from floor 2. While working on dynamic simulations, I increasingly realize how important a set of appropriate parameters is for control! I also found that in systems using PID control, different integral step sizes (or calculation frequencies) have an impact on the results. What is the general situation in industry? How many times per minute can a PID controller or control valve respond to a signal?