If both fast response time and good steady-state accuracy are nee
![If both fast response time and good steady-state accuracy are nee](http://storage.googleapis.com/tb-img/production/20/07/F1_T.S_15.7.20_Pallavi_D5.png)
A. Fast
B. Lead
C. Lag
D. lag-lead
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
Analysis:
Lag Compensator:
\(\frac{{{V_0}\left( s \right)}}{{{V_1}\left( s \right)}} = \frac{{1 + ST}}{{1 + \beta ST}}\)
Where,
\(\beta = \frac{{{R_1} + {R_2}}}{{{R_2}}},\;\beta > 1\)
In Lag Compensator, the steady-state error is reduced So, steady-state Response is increased.
In lag compensator, Transient response decreases.
Lead Compensator:
\(\frac{{{V_0}\left( s \right)}}{{{V_i}\left( s \right)}} = \frac{{\alpha \left( {1 + ST} \right)}}{{1 + \alpha ST}}\)
\(\alpha = \frac{{{R_2}}}{{{R_1} + {R_2}}}\;;\alpha < 1\)
In lead comp. steady-state error increased So, the steady-state response is decreased.
In lead comp. Transient response Improves.
Lag-lead Compensator:
Lag lead Compensator is a combined form of a lead compensator and lag comp compensator.
\(\frac{{{V_0}\left( s \right)}}{{{V_i}\left( s \right)}} = \frac{{\left( {S + {Z_1}} \right)\left( {S + {Z_2}} \right)}}{{\left( {S + {P_1}} \right)\left( {S + {P_2}} \right)}}\)
\(\beta = \underbrace {\frac{{{Z_1}}}{{{P_1}}} > 1}_{Lag}\alpha = \underbrace {\frac{{{Z_2}}}{{{P_2}}} < 1}_{Lead}\)
So, lag-lead compensator improves both steady-state accuracy and fast response time.