MATLAB: What is Root locus? How to plot it root locus The closed-loop system must always have n poles, where n is the number of poles of the open loop transfer function. Best Answer The root locus of an (open-loop) transfer function is a plot of the locations (locus) of all possible closed looppoles with proportional gain K and unity feedback.Independently from K, the closed-loop system must always have n poles, where n is the number of poles of theopen loop transfer function. The root locus must have n branches, each branch starts at a pole of the Open LoopTransfer Function (OLTF) and goes to zero of OLTF. If OLTF has more poles than zeros (as is often the case), m <n and we say that the OLTF has zeros at infinity. In this case, the limit of OLTF as s → infinity is zero. The numberof zeros at infinity is n-m, the number of poles minus the number of zeros, and is the number of branches ofthe root locus that go to infinity (asymptotes). Since the root locus is actually the locations of all possible closedloop poles, from the root locus we can select a gain such that our closed-loop system will perform the way wewant. If any of the selected poles are on the right half plane, the closed-loop system will be unstable. The polesthat are closest to the imaginary axis have the greatest influence on the closed-loop response, so even thoughthe system has three or four poles, it may still act like a second or even first order system depending on thelocation(s) of the dominant pole(s). Related SolutionsMATLAB: If i have poles and zeros of a transfer function, how to obtain this transfer function ?? transfer_function = tf( zpk(ListOfZeros, ListOfPoles, ListOfGains)) MATLAB: ‘Warning: closed loop system is unstable ‘ when getting Gain and Phase Margin using ‘[Gm,Pm] = margin(sys)’ The only thing I can think of is that your have a pole-zero cancellation at the origin. See if using the minreal function first helps. Related QuestionShow value on the root locus plot without using the Data CursorPlotting root locus with variables in transfer function
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