Hey bro I am not able to understand how closed loop stability is related to open loop transfer function what are the conditions of open loop transfer function to make CLTF stable .
There are no explicit conditions other than your closed-loop poles need to be in the left half plane (on in the unit circle in discrete systems). As he said, take your open loop system (G*H) and plot the root locus to see what value of gains k could make your system stable.
That is a good question, but well beyond the level of this video. From a basic level, you can model your plant as a linear system and then use the classical control methods discussed here to design a linear controller to bring the unstable poles back to the left half plane. Unfortunately implementation on PLCs isn't something I have much experience with, so you'll have to look elsewhere to find how to do that. Good luck!
