Homework 6 for Analytical Methods | EEL 3105, Study notes of Electrical and Electronics Engineering

HW 6 Material Type: Notes; Professor: Khargonekar; Class: ANALYTICAL METHODS; Subject: ENGINEERING: ELECTRICAL; University: University of Florida; Term: Fall 2011;

Typology: Study notes

2010/2011

Uploaded on 12/30/2011

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EEL3105Fall2011
Homework6
Note:Problem4willbegradedseparatelyforassessingthatoneofthecourseobjectivesis
met.PleasesubmitsolutiontoProblem4asaseparatedocument.
Considermatrices
12
123
13
4
01
010
001
Ak
Bbb
C
ccc
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1. ForA,choosek=3.Findtheeigenvaluesoftheresultingmatrix.Aretheyreal?Why?
2. FindaformulaforeigenvaluesofAasafunctionofk.Supposekisadesignparameter
whichrangesfrom‐100to+100.UsetheformulatoplottheeigenvaluesofAasafunction
ofkinthecomplexplane.UseMATLABtoverifyyouranswer.Suchaplotiscalledroot
locus.Commentonyourresults.
3. FindcharacteristicpolynomialsofBandCintermsofb1,b2,c1,c2,andc2.Doyouseeany
patterninyouranswer?Canyouthinkofawaytogeneralizethistoannxnmatrix?
4. Fixb2=1.Supposeb1beadesignparameterthatrangesfrom0to100.Itmayrepresentthe
valueofaphysicalcomponent(e.g.,massorresistance).FindtheeigenvaluesofBasa
functionofb1andplottheminthecomplexplane.Commentonyouranswer.Supposefor
certaindesignconsiderations(havingtodowithtransientresponse),wewanttheangleof
theeigenvaluestobe3/4.
Choosethevalueofthedesignparameterb1tosatisfythis
constraint.
5. LetAbeannxnmatrix.ShowthateigenvaluesofAarethesameasthoseofAT.
6. Considermatrices
12
45
31
369
248
A
B
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EEL 3105 Fall 2011

Homework 6

Note: Problem 4 will be graded separately for assessing that one of the course objectives is

met. Please submit solution to Problem 4 as a separate document.

Consider matrices

1 2 1 2 3

A

k

B

b b

C

c c c

  1. For A, choose k = 3. Find the eigenvalues of the resulting matrix. Are they real? Why?
  2. Find a formula for eigenvalues of A as a function of k. Suppose k is a design parameter which ranges from ‐ 100 to +100. Use the formula to plot the eigenvalues of A as a function of k in the complex plane. Use MATLAB to verify your answer. Such a plot is called root locus. Comment on your results.
  3. Find characteristic polynomials of B and C in terms of b 1 , b 2 , c 1 , c 2 , and c 2. Do you see any pattern in your answer? Can you think of a way to generalize this to an nxn matrix?
  4. Fix b 2 =1. Suppose b 1 be a design parameter that ranges from 0 to 100. It may represent the value of a physical component ( e.g., mass or resistance ). Find the eigenvalues of B as a function of b 1 and plot them in the complex plane. Comment on your answer. Suppose for certain design considerations (having to do with transient response), we want the angle of

the eigenvalues to be  3  / 4.Choose the value of the design parameter b 1 to satisfy this

constraint.

  1. Let A be an nxn matrix. Show that eigenvalues of A are the same as those of A T^.
  2. Consider matrices

A

B

Calculate eigenvalues of AB and those of BA. You can use MATLAB to compute these answers. Please comment on your answers.

  1. Now suppose A and B are two matrices (not necessarily square) such that AB and BA are both well defined. Suppose is a non‐zero eigenvalue of AB. Show that it is also an eigenvalue of BA. Not for grading [hard problem for exploration and challenge]:
  2. Let us return to Problem 3. Recall I told you in class that in order to ensure stability, all eigenvalues should have negative real parts. If we have numerical values for the parameters b 1 , b 2 , (or c 1 , c 2 , and c 2 ), then we can use MATLAB to compute the eigenvalues and see if the real parts of eigenvalues are negative. But if they are unknown parameters, then this task is harder. This is especially so as the matrix size gets larger. How could you check if all eigenvalues have negative real parts in terms of the parameters? Explore the web resources to find an answer to this question.