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.
