State Space Canonical Forms - Dr. Imtiaz Hussain

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Feedback Control Systems (FCS)

Lecture-26-27-28-29

State Space Canonical forms

Dr. Imtiaz Hussain email: imtiaz.hussain@faculty.muet.edu.pk

URL : http://imtiazhussainkalwar.weebly.com/

Lecture Outline

– Canonical forms of State Space Models

• Phase Variable Canonical Form

• Controllable Canonical form

• Observable Canonical form

– Similarity Transformations

• Transformation of coordinates

– Transformation to CCF

– Transformation OCF

Canonical Forms

• Canonical forms are the standard forms of state space models.

• Each of these canonical form has specific advantages which makes it convenient for use in particular design technique.

• There are four canonical forms of state space models

– Phase variable canonical form

– Controllable Canonical form

– Observable Canonical form

– Diagonal Canonical form

– Jordan Canonical Form

Companion forms

Modal forms

• It is interesting to note that the dynamics properties of system remain unchanged whichever the type of representation is used.

Phase Variable Canonical form

• The method of phase variables possess mathematical advantage over other representations.

• This type of representation can be obtained directly from differential equations.

• Decomposition of transfer function also yields Phase variable form.

Phase Variable Canonical form

• Consider an n th order linear plant model described by the differential equation 𝑑 𝑛 𝑦 𝑑𝑑 𝑛

+ π‘Ž

1 𝑑 𝑛−1 𝑦 𝑑𝑑 𝑛−1

+ β‹― + π‘Ž 𝑛−1 𝑑𝑦 𝑑𝑑

+ π‘Ž 𝑛 𝑦 = 𝑒(𝑑)

• Where y(t) is the plant output and u(t) is the plant input.

• A state model for this system is not unique but depends on the choice of a set of state variables.

• A useful set of state variables, referred to as phase variables , is defined as: π‘₯

1

= 𝑦, π‘₯

2

= 𝑦, π‘₯

3

= β‹― , π‘₯ 𝑛

= 𝑑 𝑛−1 𝑦 𝑑𝑑 𝑛−1

Phase Variable Canonical form π‘₯

1

= 𝑦, π‘₯

2

= 𝑦, π‘₯

3

= β‹― , π‘₯ 𝑛

= 𝑑 𝑛−1 𝑦 𝑑𝑑 𝑛−1

• Taking derivatives of the first n-1 state variables, we have

π‘₯

1

= π‘₯

2

, π‘₯

2

= π‘₯

3

, π‘₯

3

= π‘₯

4

β‹― , π‘₯ 𝑛−1

= π‘₯ 𝑛

π‘₯ 𝑛

= −π‘Ž 𝑛 π‘₯

1

− π‘Ž 𝑛−1 π‘₯

2

− β‹― − π‘Ž

1 π‘₯ 𝑛

+ 𝑒(𝑑)



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

1

2 x  n

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1 x 

 n

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0

0

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0 a n

1

0

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0

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1

0

1

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3

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0

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1

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1 x x



1

2 n

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οƒͺ

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0

1

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

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Phase Variable Canonical form π‘₯

1

= 𝑦, π‘₯

2

= 𝑦, π‘₯

3

= β‹― , π‘₯ 𝑛

= 𝑑 𝑛−1 𝑦 𝑑𝑑 𝑛−1

• Output equation is simply y

ο€½



1 0  0 0





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οƒͺ

οƒͺ

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 x

1 x

2

 x n

ο€­

1 x n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

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

Phase Variable Canonical form

u ( t )

οΌ‹ y

( n

ο€­

1 ) ο€½ x n y

( n )

οΌ‹

ο€­ a

1

ο€­ a

2

∫ y ( n

ο€­

2 )

ο€½ x n

ο€­

1



ο€­ a n

… y

ο‚’ ο€½ x

2

∫ y

ο€½ x

1

8

Phase Variable Canonical form

u 1 x  n

1  n

ο€­

1 s

1 s x  n

ο€­

2

1 s

ο€­ 

1

ο€­ 

2

ο€­ 

3



ο€­  n

ο€­

1





1

ο€½ x

2

1 s

ο€­  n x

1

1 y

9

Phase Variable Canonical form (Example-1)

• Obtain the state equation in phase variable form for the following differential equation, where u(t) is input and y(t) is output.

2 𝑑 3 𝑦 𝑑𝑑 3

+ 4 𝑑 2 𝑦 𝑑𝑑 2

+ 6 𝑑𝑦 𝑑𝑑

+ 8𝑦 = 10𝑒(𝑑)

• The differential equation is third order, thus there are three state variables: π‘₯

1

= 𝑦 π‘₯

2

= 𝑦 π‘₯

3

= 𝑦

• And their derivatives are (i.e state equations)

π‘₯

1

= π‘₯

2

π‘₯

2

= π‘₯

3

π‘₯

3

= −4π‘₯

1

− 3π‘₯

2

− 2π‘₯

3

+ 5𝑒(𝑑)

Phase Variable Canonical form (Example-1)

π‘₯

1

= π‘₯

2

π‘₯

2

= π‘₯

3

π‘₯

3

= −4π‘₯

1

− 3π‘₯

2

− 2π‘₯

3

+ 5𝑒(𝑑)

• In vector matrix form π‘₯

1

= 𝑦 π‘₯

2

= 𝑦 π‘₯

3

= 𝑦

οƒͺ





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2 x

3

1

οƒΊ



οƒΉ

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ο€½

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

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οƒͺ

ο€­

0

0

4 y ( t )

ο€½



1 0

1

0

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3

0

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1 x

2 x

3

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1

2

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1

3

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0

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0

5

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Home Work: Draw Sate diagram

Phase Variable Canonical form (Example-2)

• Consider the transfer function of a third-order system where the numerator degree is lower than that of the denominator.

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑏 π‘œ 𝑠 2 + 𝑏

1 𝑠 + 𝑏

2 𝑠 3 + π‘Ž

1 𝑠 2 + π‘Ž

2 𝑠 + π‘Ž

3

• Transfer function can be decomposed into cascade form

π‘Š(𝑠)

π‘ˆ(𝑠) 1 𝑠 3 + π‘Ž

1 𝑠 2 + π‘Ž

2 𝑠 + π‘Ž

3 𝑏 π‘œ 𝑠 2 + 𝑏

1 𝑠 + 𝑏

2

π‘Œ(𝑠)

• Denoting the output of the first block as W(s) , we have the following input/output relationships:

π‘Š(𝑠)

=

π‘ˆ(𝑠)

1 𝑠 3 + π‘Ž

1 𝑠 2 + π‘Ž

2 𝑠 + π‘Ž

3

π‘Œ(𝑠)

π‘Š(𝑠)

= 𝑏 π‘œ 𝑠 2 + 𝑏

1 𝑠 + 𝑏

2

Phase Variable Canonical form (Example-2)

π‘Š(𝑠)

=

π‘ˆ(𝑠)

1 𝑠 3 + π‘Ž

1 𝑠 2 + π‘Ž

2 𝑠 + π‘Ž

3

π‘Œ(𝑠)

π‘Š(𝑠)

= 𝑏 π‘œ 𝑠 2 + 𝑏

1 𝑠 + 𝑏

2

• Re-arranging above equation yields 𝑠 3 π‘Š 𝑠 = −π‘Ž

1 𝑠 2 π‘Š 𝑠 − π‘Ž

2 π‘ π‘Š 𝑠 − π‘Ž

3

π‘Š(𝑠) + π‘ˆ(𝑠)

π‘Œ(𝑠) = 𝑏 π‘œ 𝑠 2 π‘Š(𝑠) + 𝑏

1 π‘ π‘Š(𝑠) + 𝑏

2

π‘Š(𝑠)

• Taking inverse Laplace transform of above equations.

𝑀 𝑑 = −π‘Ž

1 𝑀 𝑑 − π‘Ž

2 𝑀 𝑑 − π‘Ž

3 𝑀(𝑑) + u(𝑑) 𝑦(𝑑) = 𝑏 π‘œ 𝑀 𝑑 + 𝑏

1 𝑀 𝑑 + 𝑏

2 𝑀(𝑑)

• Choosing the state variables in phase variable form π‘₯

1

= 𝑀 π‘₯

2

= π‘₯

3

Phase Variable Canonical form (Example-1)

• State Equations are given as

π‘₯

1

= π‘₯

2

π‘₯

2

= π‘₯

3

π‘₯

3

= −π‘Ž

3 π‘₯

1

− π‘Ž

2 π‘₯

2

− π‘Ž

1 π‘₯

3

+ 𝑒(𝑑)

• And the output equation is 𝑦(𝑑) = 𝑏

2 π‘₯

1

+ 𝑏

1 π‘₯

2

+ 𝑏 π‘œ π‘₯

3 𝑏 π‘œ 𝑏

1 𝑏

2 π‘Ž

1 π‘Ž

2 π‘Ž

3

Phase Variable Canonical form (Example-1)

• State Equations are given as

π‘₯

1

= π‘₯

2

π‘₯

2

= π‘₯

3

π‘₯

3

= −π‘Ž

3 π‘₯

1

− π‘Ž

2 π‘₯

2

− π‘Ž

1 π‘₯

3

+ 𝑒(𝑑)

• And the output equation is 𝑦(𝑑) = 𝑏

2 π‘₯

1

+ 𝑏

1 π‘₯

2

+ 𝑏 π‘œ π‘₯

3

−π‘Ž

1

−π‘Ž

2

−π‘Ž

3 𝑏 π‘œ 𝑏

1 𝑏

2

Phase Variable Canonical form (Example-1)

• State Equations are given as

π‘₯

1

= π‘₯

2

π‘₯

2

= π‘₯

3

π‘₯

3

= −π‘Ž

3 π‘₯

1

− π‘Ž

2 π‘₯

2

− π‘Ž

1 π‘₯

3

+ 𝑒(𝑑)

• And the output equation is 𝑦(𝑑) = 𝑏

2 π‘₯

1

+ 𝑏

1 π‘₯

2

+ 𝑏 π‘œ π‘₯

3

• In vector matrix form

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



οƒͺ x x

2 x

1

3

οƒΊ



οƒΉ

οƒΊ

ο€½

οƒͺ





οƒͺ

ο€­

0

0 a

3 y ( t )

ο€½

 b

2 b

1

1

0

ο€­ a

2 b o



οƒͺ





οƒͺ x

1 x

2 x

3

οƒΊ



οƒΉ

οƒΊ

ο€­

0

1 a

1

οƒΊ



οƒΉ

οƒΊ

οƒͺ





οƒͺ x x

2 x

1

3

οƒΊ



οƒΉ

οƒΊ





οƒͺ

οƒͺ

 1

0

0

οƒΉ

οƒΊ

οƒΊ

 u ( t )

Companion Forms

• Consider a system defined by n y

 a

1 n y

ο€­

1

   a n

ο€­

1 y   a n y

ο€½ b o n u

 b

1 n u

ο€­

1

   b n

ο€­

1 u   b n u

• where u is the input and y is the output.

• This equation can also be written as

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑏 π‘œ 𝑠 𝑛 + 𝑏

1 𝑠 𝑛−1 + β‹― + 𝑏 𝑛−1 𝑠 + 𝑏 𝑛 𝑠 𝑛 + π‘Ž

1 𝑠 𝑛−1 + β‹― + π‘Ž 𝑛−1 𝑠 + π‘Ž 𝑛

• We will present state-space representations of the system defined by above equations in controllable canonical form and observable canonical form.

Controllable Canonical Form

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑏 π‘œ 𝑠 𝑛 + 𝑏

1 𝑠 𝑛−1 + β‹― + 𝑏 𝑛−1 𝑠 + 𝑏 𝑛 𝑠 𝑛 + π‘Ž

1 𝑠 𝑛−1 + β‹― + π‘Ž 𝑛−1 𝑠 + π‘Ž 𝑛

• The following state-space representation is called a controllable canonical form:



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οƒͺ

οƒͺ

οƒͺ

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 x 

2 x  n

ο€­

1 x  x 



1 n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



ο€½



οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ



ο€­

0

0



0 a n

1

0



0

ο€­ a n

ο€­

1

0

1



0

ο€­ a n

ο€­

2









 ο€­

0

0



1 a

1

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οƒΊ

οƒΊ

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

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οƒͺ

οƒͺ

οƒͺ

οƒͺ

 x x

1

2 x n

ο€­

1 x

 n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



 οƒͺ

οƒͺ

οƒͺ

 1



0

οƒΉ

οƒͺ

οƒͺ 0

οƒΊ

οƒΊ



0

οƒΊ

οƒΊ

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 u

Controllable Canonical Form

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑏 π‘œ 𝑠 𝑛 + 𝑏

1 𝑠 𝑛−1 + β‹― + 𝑏 𝑛−1 𝑠 + 𝑏 𝑛 𝑠 𝑛 + π‘Ž

1 𝑠 𝑛−1 + β‹― + π‘Ž 𝑛−1 𝑠 + π‘Ž 𝑛 y

ο€½

 b n

ο€­ a n b o b n

ο€­

1

ο€­ a n

ο€­

1 b o

 b

2

ο€­ a

2 b o b

1

ο€­ a

1 b o





οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ

 x

1 x

2

 x n

ο€­

1 x n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



 b o u

Controllable Canonical Form u ( t )

οΌ‹ v

( n )

οΌ‹

ο€­ 

1

∫ ∫

ο€­ 

2



ο€­  n

… v

ο‚’ ο€½ x

2

∫ v

ο€½ x

1 d dt

 d dt d dt

 n

 n

ο€­

1



1

οΌ‹

Controllable Canonical Form (Example)

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑠 + 3 𝑠 2 + 3𝑠 + 2

• Let us Rewrite the given transfer function in following form

π‘Œ(𝑠)

π‘ˆ(𝑠)

=

0𝑠 2 + 𝑠 + 3 𝑠 2 + 3𝑠 + 2 a

2

ο€½

2 a

1

ο€½

3 b

2

ο€½

3 b

1

ο€½

1 b o

ο€½

0



οƒͺ x  x 

2

1

οƒΉ

οƒΊ

ο€½



οƒͺ

ο€­

0 a

2

ο€­

1 a

1

οƒΉ

οƒΊ



οƒͺ x x

2

1

οƒΉ

οƒΊ





οƒͺ

0

1

οƒΉ

οƒΊ u



οƒͺ x  x 

2

1

οƒΉ

οƒΊ

ο€½



οƒͺ

ο€­

0

2

ο€­

1

3

οƒΉ

οƒΊ



οƒͺ x x

2

1

οƒΉ

οƒΊ





οƒͺ

1

0

οƒΉ

οƒΊ u

Controllable Canonical Form (Example)

π‘Œ(𝑠)

π‘ˆ(𝑠)

=

0𝑠 2 + 𝑠 + 3 𝑠 2 + 3𝑠 + 2 a

2

ο€½

2 a

1

ο€½

3 b

2

ο€½

3 b

1

ο€½

1 b o

ο€½

0 y

ο€½

 b

2

ο€­ a

2 b o b

1

ο€­ a

1 b o





οƒͺ x x

1

2

οƒΉ

οƒΊ

 b o u y

ο€½



οƒͺ x x

2

1

οƒΉ

οƒΊ

Controllable Canonical Form (Example)

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑠 + 3 𝑠 2 + 3𝑠 + 2

• By direct decomposition of transfer function

Y

U

( s

( s

)

)

ο€½ s

2 s





3 s

3



2

οƒ— s

ο€­

2

P ( s ) s

ο€­

2

P ( s )

Y ( s )

U ( s )

ο€½

P ( s ) s

ο€­

1



P ( s )



3

3 s

ο€­

1

P ( s ) s

ο€­

2



P ( s )

2 s

ο€­

2

P ( s )

• Equating Y(s) with numerator on the right hand side and U(s) with denominator on right hand side.

Y ( s )

ο€½ s

ο€­

1

P ( s )



3 s

ο€­

2

P ( s ).........

.......( 1 )

U ( s )

ο€½

P ( s )



3 s

ο€­

1

P ( s )



2 s

ο€­

2

P ( s ).........

.......( 2 )

Controllable Canonical Form (Example)

• Rearranging equation-2 yields

P ( s )

ο€½

U ( s )

ο€­

3 s

ο€­

1

P ( s )

ο€­

2 s

ο€­

2

P ( s ).........

.......( 3 )

• Draw a simulation diagram using equations (1) and (3)

P ( s )

ο€½

U ( s )

ο€­

3 s

ο€­

1

P ( s )

ο€­

2 s

ο€­

2

P ( s ) Y ( s )

ο€½ s

ο€­

1

P ( s )



3 s

ο€­

2

P ( s )

U(s)

-2

P(s)



2

-3

1/s x

2

ο€½ x 

1

1/s

1 x

1

3

Y(s)

Controllable Canonical Form (Example)

-2

U(s)

P(s)



2

-3

1/s x

2

ο€½  x

1

1/s x

1

3

Y(s)

1

• State equations and output equation are obtained from simulation diagram.

x 

1

ο€½ x

2



2

ο€½

U ( s )

ο€­

3 x

2

ο€­

2 x

1

Y ( s )

ο€½

3 x

1

 x

2

Controllable Canonical Form (Example) x 

1

ο€½ x

2



2

ο€½

U ( s )

ο€­

3 x

2

ο€­

2 x

1

Y ( s )

ο€½

3 x

1

 x

2

• In vector Matrix form



οƒͺ x  x 

2

1

οƒΉ

οƒΊ

ο€½



οƒͺ

ο€­

0

2

ο€­

1

3

οƒΉ





οƒͺ x x

2

1

οƒΉ

οƒΊ







0

1

οƒΉ

 f ( t ) y

ο€½



3 1





οƒͺ x

1 x

2

οƒΉ

οƒΊ

Observable Canonical Form

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑏 π‘œ 𝑠 𝑛 + 𝑏

1 𝑠 𝑛−1 + β‹― + 𝑏 𝑛−1 𝑠 + 𝑏 𝑛 𝑠 𝑛 + π‘Ž

1 𝑠 𝑛−1 + β‹― + π‘Ž 𝑛−1 𝑠 + π‘Ž 𝑛

• The following state-space representation is called an observable canonical form:



οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ

 x x  n

ο€­

1 x 

 x 



1

2 n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



ο€½



0

οƒͺ

οƒͺ

οƒͺ

οƒͺ

1



οƒͺ



0

0

0

0



0

0











0

0



0

1

ο€­

ο€­

ο€­

ο€­ n a n

ο€­

1

 a a a

2

1

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ





οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ

 x x

1

2 x n

ο€­

1 x

 n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ





οƒͺ





οƒͺ

οƒͺ

οƒͺ

οƒͺ b n b n

ο€­

1 b

2 b

1

ο€­

ο€­

ο€­

ο€­

 a n b o a n

ο€­

1 b o a a

2

1 b b o o

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

 u

Observable Canonical Form

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑏 π‘œ 𝑠 𝑛 + 𝑏

1 𝑠 𝑛−1 + β‹― + 𝑏 𝑛−1 𝑠 + 𝑏 𝑛 𝑠 𝑛 + π‘Ž

1 𝑠 𝑛−1 + β‹― + π‘Ž 𝑛−1 𝑠 + π‘Ž 𝑛 y

ο€½



0 0  0 1





οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ

 x

1 x

2

 x n

ο€­

1 x n

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



 b o u

Observable Canonical Form (Example)

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑠 + 3 𝑠 2 + 3𝑠 + 2

• Let us Rewrite the given transfer function in following form

π‘Œ(𝑠)

π‘ˆ(𝑠)

=

0𝑠 2 + 𝑠 + 3 𝑠 2 + 3𝑠 + 2 a

2

ο€½

2 a

1

ο€½

3 b

2

ο€½

3 b

1

ο€½

1 b o

ο€½

0



οƒͺ x  x 

2

1

οƒΉ

οƒΊ

ο€½



οƒͺ

0

1



οƒͺ x  x 

2

1

οƒΉ

οƒΊ

ο€½



οƒͺ

0

1

ο€­

ο€­ a

2 a

1

οƒΉ

οƒΊ



οƒͺ x x

2

1

οƒΉ

οƒΊ





 b b

2

1

ο€­

ο€­ a

2 b o a

1 b o

οƒΉ

οƒΊ u

ο€­

ο€­

2

3

οƒΉ

οƒΊ



οƒͺ x x

2

1

οƒΉ

οƒΊ





οƒͺ

3

οƒΉ

1

οƒΊ u

Observable Canonical Form (Example)

π‘Œ(𝑠)

π‘ˆ(𝑠)

=

0𝑠 2 + 𝑠 + 3 𝑠 2 + 3𝑠 + 2 a

2

ο€½

2 a

1

ο€½

3 b

2

ο€½

3 b

1

ο€½

1 b o

ο€½

0 y

ο€½



0 1





οƒͺ x

1 x

2

οƒΉ

οƒΊ

 b o u y

ο€½



0 1





οƒͺ x

1 x

2

οƒΉ

οƒΊ

Similarity Transformations

• It is desirable to have a means of transforming one state-space representation into another.

• This is achieved using so-called similarity transformations.

• Consider state space model x  ( t )

ο€½

Ax ( t )



Bu ( t ) y ( t )

ο€½

Cx ( t )



Du ( t )

• Along with this, consider another state space model of the same plant x



( t )

ο€½

A x ( t )



B u ( t ) y ( t )

ο€½

C x ( t )



D u ( t )

• Here the state vector π‘₯ , say, represents the physical state relative to some other reference, or even a mathematical coordinate vector.

Similarity Transformations

• When one set of coordinates are transformed into another set of coordinates of the same dimension using an algebraic coordinate transformation, such transformation is known as similarity transformation.

• In mathematical form the change of variables is written as, x ( t )

ο€½

T x ( t )

• Where T is a nonsingular nxn transformation matrix.

• The transformed state π‘₯(𝑑) is written as x ( t )

ο€½

T

ο€­

1 x ( t )

Similarity Transformations

• The transformed state π‘₯(𝑑) is written as x ( t )

ο€½

T

ο€­

1 x ( t )

• Taking time derivative of above equation x



( t )

ο€½

T

ο€­

1 x  (t) x



( t )

ο€½

T

ο€­

1



Ax ( t )



Bu ( t )



( t )

ο€½

T

ο€­

1



AT x ( t )



Bu ( t )

 x  ( t )

ο€½

Ax ( t )



Bu ( t ) x ( t )

ο€½

T x ( t )

( t )

ο€½

T

ο€­

1

AT x ( t )



T

ο€­

1

Bu ( t )

( t )

ο€½

A x ( t )



B u ( t )

A

ο€½

T

ο€­

1

AT B

ο€½

T

ο€­

1

B

Similarity Transformations

• Consider transformed output equation y ( t )

ο€½

C x ( t )



D u ( t )

• Substituting π‘₯ 𝑑 = 𝑇 −1 π‘₯(𝑑) in above equation y ( t )

ο€½

C T

ο€­

1 x ( t )



D u ( t )

• Since output of the system remain unchanged [i.e.

𝑦 𝑑 = 𝑦(𝑑) ] therefore above equation is compared with 𝑦 𝑑 =

𝐢π‘₯ 𝑑 + 𝐷𝑒(𝑑) that yields

C

ο€½

CT D

ο€½

D

Similarity Transformations

• Following relations are used to preform transformation of coordinates algebraically

A

ο€½

T

ο€­

1

AT B

ο€½

T

ο€­

1

B

C

ο€½

CT D

ο€½

D

Similarity Transformations

• Invariance of Eigen Values sI

ο€­

A

ο€½ sI

ο€­

T

ο€­

1

AT

ο€½ sT

ο€­

1

T

ο€­

T

ο€­

1

AT



T

ο€­

1

T

ο€½

I

ο€½

T

ο€­

1 sI

ο€­

A T

ο€½ sI

ο€­

A sI

ο€­

A

ο€½ sI

ο€­

A

Transformation to CCF

• Transformation to CCf is done by means of transformation matrix

P .

P

ο€½

CM

ο‚΄

W

• Where CM is controllability Matrix and is given as

𝐢𝑀 = 𝐡 𝐴𝐡 β‹― 𝐴 𝑛−1 𝐡 and W is coefficient matrix

W

ο€½



οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ

 a a n

ο€­

1 n

ο€­

2

 a

1

1 a n

ο€­

2 a n

ο€­

3



1

0









 a

1

1



0

0

1

0



0

0

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



Where the a i

’s are coefficients of the characteristic polynomial 𝑠𝐼 − 𝐴 = 𝑠 𝑛

+ π‘Ž

1 𝑠 𝑛−1

+ π‘Ž

2 𝑠 𝑛−2

+ β‹― + π‘Ž 𝑛−1 s+ π‘Ž 𝑛

Transformation to CCF

• Once the transformation matrix P is computed following relations are used to calculate transformed matrices.

A

ο€½

P

ο€­

1

AP B

ο€½

P

ο€­

1

B C

ο€½

CP D

ο€½

D

Transformation to CCF ( Example )

• Consider the state space system given below.

π‘₯

1 π‘₯

2 π‘₯

3

=

1 2 1

0 1 3

1 1 1 π‘₯

1 π‘₯

2 π‘₯

3

+

1

0

1 𝑒(𝑑)

• Transform the given system in CCF.

Transformation to CCF ( Example ) π‘₯

1 π‘₯

2 π‘₯

3

=

1 2 1

0 1 3

1 1 1 π‘₯

1 π‘₯

2 π‘₯

3

+

1

0

1

• The characteristic equation of the system is 𝑒(𝑑) 𝑠𝐼 − 𝐴 = 𝑠 − 1 −2 −1

0 𝑠 − 1 −3

−1 −1 𝑠 − 1

= 𝑠 3 − 3𝑠 2 − 𝑠 − 3 π‘Ž

1

= −3,

W

ο€½

οƒͺ





οƒͺ a

2 a

1

1 a

1

1

0 π‘Ž

2

= −1,

1

0

0

οƒΊ



οƒΉ

οƒΊ

ο€½

οƒͺ





οƒͺ

ο€­

ο€­

1

1

3 π‘Ž

3

= −1

ο€­

3

1

0

1

0

0

οƒΊ



οƒΉ

οƒΊ

Transformation to CCF ( Example ) π‘₯

1 π‘₯

2 π‘₯

3

=

1 2 1

0 1 3

1 1 1 π‘₯

1 π‘₯

2 π‘₯

3

+

1

0

1 𝑒(𝑑)

• Now the controllability matrix CM is calculated as

𝐢𝑀 = 𝐡 𝐴𝐡 𝐴 2 𝐡

𝐢𝑀 =

1 2 10

0 3 9

1 2 7

• Transformation matrix P is now obtained as

𝑃 = 𝐢𝑀 × π‘Š =

1 2 10

0 3 9

1 2 7

−1 −3 1

−3 1 0

1 0 0

𝑃 =

3 −1 1

0 3 0

0 −1 1

Transformation to CCF ( Example )

• Using the following relationships given state space representation is transformed into CCf as

A

ο€½

P

ο€­

1

AP B

ο€½

P

ο€­

1

B

A

ο€½

P

ο€­

1

AP

ο€½



οƒͺ

0

οƒͺ



0

3

1

0

1

B

ο€½

P

ο€­

1

B

ο€½



οƒͺ

οƒͺ



0

0

1

οƒΉ

οƒΊ

οƒΊ



0

1

3

οƒΉ

οƒΊ

οƒΊ

 𝑠𝐼 − 𝐴 = 𝑠 3 − 3𝑠 2 − 𝑠 − 3

Transformation to OCF

• Transformation to CCf is done by means of transformation matrix

Q .

Q

ο€½

( W

ο‚΄

OM )

ο€­

1

• Where OM is observability Matrix and is given as

𝑂𝑀 = 𝐢 𝐢𝐴 β‹― 𝐢𝐴 𝑛−1 𝑇 and W is coefficient matrix

W

ο€½



οƒͺ

οƒͺ

οƒͺ

οƒͺ

οƒͺ

 a a n

ο€­

1 n

ο€­

2

 a

1

1 a n

ο€­

2 a n

ο€­

3



1

0









 a

1

1



0

0

1

0



0

0

οƒΉ

οƒΊ

οƒΊ

οƒΊ

οƒΊ

οƒΊ



Where the a i

’s are coefficients of the characteristic polynomial 𝑠𝐼 − 𝐴 = 𝑠 𝑛

+ π‘Ž

1 𝑠 𝑛−1

+ π‘Ž

2 𝑠 𝑛−2

+ β‹― + π‘Ž 𝑛−1 s+ π‘Ž 𝑛

Transformation to OCF

• Once the transformation matrix Q is computed following relations are used to calculate transformed matrices.

A

ο€½

Q

ο€­

1

AQ B

ο€½

Q

ο€­

1

B C

ο€½

CQ D

ο€½

D

Transformation to OCF ( Example )

• Consider the state space system given below.

π‘₯

1 π‘₯

2 π‘₯

3

=

1 2 1

0 1 3

1 1 1 π‘₯

1 π‘₯

2 π‘₯

3

+ 𝑦(𝑑) = 1 1 0

• Transform the given system in OCF.

π‘₯

1 π‘₯

2 π‘₯

3

1

0

1 𝑒(𝑑)

Transformation to OCF ( Example ) π‘₯

1 π‘₯

2 π‘₯

3

=

1 2 1

0 1 3

1 1 1 π‘₯

1 π‘₯

2 π‘₯

3

+

1

0

1

• The characteristic equation of the system is 𝑒(𝑑) 𝑠𝐼 − 𝐴 = 𝑠 − 1 −2 −1

0 𝑠 − 1 −3

−1 −1 𝑠 − 1

= 𝑠 3 − 3𝑠 2 − 𝑠 − 3 π‘Ž

1

= −3,

W

ο€½

οƒͺ





οƒͺ a

2 a

1

1 a

1

1

0 π‘Ž

2

= −1,

1

0

0

οƒΊ



οƒΉ

οƒΊ

ο€½

οƒͺ





οƒͺ

ο€­

ο€­

1

1

3 π‘Ž

3

= −1

ο€­

3

1

0

1

0

0

οƒΊ



οƒΉ

οƒΊ

Transformation to OCF ( Example ) π‘₯

1 π‘₯

2 π‘₯

3

=

1 2 1

0 1 3

1 1 1 π‘₯

1 π‘₯

2 π‘₯

3

+

1

0

1 𝑒(𝑑) 𝑦(𝑑) = 1 1 0

• Now the observability matrix OM is calculated as π‘₯

1 π‘₯

2 π‘₯

3

𝑂𝑀 = 𝐢 𝐢𝐴 𝐢𝐴 2 𝑇

𝑂𝑀 =

1 1 0

1 3 4

5 6 10

• Transformation matrix Q is now obtained as

𝑄 = π‘Š × π‘‚π‘€ −1 =

0.333

−0.166

0.333

−0.333

0.166

0.666

0.166

0.166

0.166

Transformation to CCF ( Example )

• Using the following relationships given state space representation is transformed into CCf as

A

ο€½

Q

ο€­

1

AQ B

ο€½

Q

ο€­

1

B C

ο€½

CQ D

ο€½

D

A

ο€½

Q

ο€­

1

AQ

ο€½



οƒͺ

0

οƒͺ



1

0

0

0

1

3

οƒΉ

οƒΊ

1

3

οƒΊ



B

ο€½

Q

ο€­

1

B

ο€½

οƒͺ





οƒͺ

3

2

1

οƒΊ



οƒΉ

οƒΊ

C

ο€½

CQ

ο€½



0 0 1



Home Work

• Obtain state space representation of following transfer function in Phase variable canonical form, OCF and CCF by

– Direct Decomposition of Transfer Function

– Similarity Transformation

– Direct Approach

π‘Œ(𝑠)

π‘ˆ(𝑠)

= 𝑠 2 + 2𝑠 + 3 𝑠 3 + 5𝑠 2 + 3𝑠 + 2

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END OF LECTURES-26-27-28-29

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