I have a few Control System questions: I'm looking for a simple explanation of when each of these are used... whenever I read about them, I just can't remember which is used for what; this is probably because the book I'm using explains it in hard to understand terms. 1) When do you use a Phase-Lead Compensator? 2) When do you use a Phase-Lag Compensator? I understand each is used to shift the frequency responses in a certain direction, but I can't seen to figure out a good way to remember which does what. Maybe I'm missing the idea behind the terms "Lead" and "Lag"? In fact, what are the reasonings behind the Lag and Lead terms? What exactly is being lagged or lead? PS - I know these questions are painfully obvious, but I'm so burdened by work that I can barely think. I just can't seem to get the concepts right. Thank you.