Doesn’t the change in open-loop gain alters the phase of closed-loop transfer function? How can we say that decreasing the gain makes it nearer to the phase cross over frequency point, if it affects the phase as well? Eg: 1/(s+1) → open-loop TF, Considering a unity feedback system( closed loop TF --> 1/(S+2) ) and now by increasing the open loop gain by factor of let's say 2. Closed loop TF will be 2/(S+3). Phase cross over frequency changes right? Please correct me, If I am missing any thing here. I feel like in only open loop phase doesn't change with altering gain. Could you please explain this. Btw great video this!
Hi Viru, I will make a couple of points and I hope it will help you understand the concept better: 1. Changing the gain will change the cross-over frequency of open loop tf as well. That is because the 0dB cross-over will happen at a different frequency. (Phase plot will not change but the cross-over frequency will change) 2. The idea of approximating closed loop tf - T/(1+T) will work only when T>>1 and T
This is one of the best videos in control system that I´ve seen so far. Thanks a lot!
Great one! looking forward to more.
really awesome video..
Doesn’t the change in open-loop gain alters the phase of closed-loop transfer function? How can we say that decreasing the gain makes it nearer to the phase cross over frequency point, if it affects the phase as well?
Eg: 1/(s+1) → open-loop TF, Considering a unity feedback system( closed loop TF --> 1/(S+2) ) and now by increasing the open loop gain by factor of let's say 2. Closed loop TF will be 2/(S+3). Phase cross over frequency changes right? Please correct me, If I am missing any thing here. I feel like in only open loop phase doesn't change with altering gain.
Could you please explain this.
Btw great video this!
Hi Viru,
I will make a couple of points and I hope it will help you understand the concept better:
1. Changing the gain will change the cross-over frequency of open loop tf as well. That is because the 0dB cross-over will happen at a different frequency. (Phase plot will not change but the cross-over frequency will change)
2. The idea of approximating closed loop tf - T/(1+T) will work only when T>>1 and T
Thank you
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