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Unformatted text preview: ECE 3085 Spring 2008 Exam 3 ClosedBook, ClosedNotes, 4 Problems. Name: 1. A control system has the following structure, where L ( s ) is a ratio of two polynomials; L ( s ) has more poles than zeros, and all its poles are located in the open left half plane. Let H ( s ) denote the overall transfer function satisfying Y ( s ) = H ( s ) R ( s ). L y r + (a) The loop transfer function L ( s ) is characterized in the diagram to the left and the overall transfer function H ( s ) is characterized in the diagram to the right; the labeling of these diagrams establishes a unique correspondence between them. Precisely mark the diagram to the right with an asterisk corresponding to the asterisk found on the diagram to the left.1.510.5 0.5 1 1.51.510.5 0.5 1 1.5 Re{L(j ω )} Im{L(j ω )}10.5 0.5 110.5 0.5 1 Re{H(j ω )} Im{H(j ω )} L ( jω ) = j ⇒ H ( jω ) = L ( jω ) 1 + L ( jω ) = j 1 j = j 1 j · 1 + j 1 + j = 1 j 2 (b) Prove that this system is internally stable. The given plot of L ( jω ) is at least a portion of the Nyquist plot of L ( s ). Since L ( s ) is strictly proper, the point L ( jω ) = 0 corresponds to ω = ±∞ . Since the coefficients of L ( s ) are real, the point L ( jω ) = 1 corresponds to ω = 0. As further confirmation that the entire jω...
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This test prep was uploaded on 04/17/2008 for the course ECE 3085 taught by Professor Taylor during the Spring '08 term at Georgia Tech.
 Spring '08
 Taylor

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