A feedback control system has the following characteristics: system type: 0 posi
ID: 2250273 • Letter: A
Question
A feedback control system has the following characteristics:
system type: 0
position error constant: 34 dB
gain crossover frequency: 25 Hz
phase crossover frequency: 85 Hz
phase margin: 60 degrees
gain margin: 23 dB
It is desired to improve the steady-state accuracy by a factor of 5. How would you recommend doing this? Explain why you chose that answer.
(a) Increase the gain by 6 dB making error constant 40 dB.
(b) Use PI control to make the system type 2 and keep the gain margin greater than 23 dB.
(c) Use PD control to keep the system type 0 and the gain margin 23 dB.
(d) Use lead control to improve phase margin and decrease daming which will improve error.
(e) None of the above.
Explanation / Answer
The above specification can be achived by option (b)
We can use PI control to make the syatem type 2 and keep the gain margin greater than 23 dB due to following reasons
1. Since PI controller is used to remove the steady state error occurs from P controller and in terms of speed and stability the system has negative impact
2. by using integral controller the order of the closed loop system can be increased