Lead Lag Block

Purpose

The Lead Lag (LL) block allows you to simulate process dynamics by combining the advantages of lead and lag compensation strategies.

TIP: We suggest you use this block only if you are thoroughly familiar with lead lag theory. If you simply need a time delay, consider using the Dead Time block.

The Lead Lag formula is:

Output=C3[C1(Input-Prior Output)+(Input*Scan time)+C2(Prior Output)]

C1, C2, and the scan time (of the primary block) are in seconds. K is the constant defined in the block's Constant field.

Features

The Lead Lag block:

  • Is an optional control block.
  • Is a secondary block.
  • Lets the lead dominate if the lead time is greater than the lag time.
  • Lets the lag dominate if the lag time is greater than the lead time.

NOTE: Lead compensation tends to improve the rise time and overshoot of the system, but increases the dead band. Lag compensation improves the steady-state response, but results in a longer rise time since the dead band decreases.

 

Typical Uses

Example

Fields

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