Week 16
Controllability
and
Observability
Prof Charlton S. Inao
Defence University
College of Engineering
16/3/2016
Instructional Objectives
6/3/2016 2
CONTROLLABILITY
6/3/2016 3
6/3/2016 4
6/3/2016 5
6/3/2016 6
76/3/2016
State Controllability
• Controllability Matrix CM
• System is said to be state controllable if
 BABAABBCM n 12 
 
)( nCMrank 
State Controllability (Example)
• Consider the system given below
• State diagram of the system is
 xy
uxx
21
0
1
30
01
















1
1
)(sU
)(sY
1
-1
s
3
-1
s
2
1x
2x
State Controllability (Example)
 ABBCM 





 

00
11
CM







0
1
B 






0
1
AB
System order(state
variable) is 2 but rank is
1, therefore not
controllable
116/3/2016
6/3/2016 12
136/3/2016
Workout Exercise
146/3/2016
OBSERVABILITY
156/3/2016
166/3/2016
176/3/2016
186/3/2016
State Observability
• Observable Matrix (OM)
• The system is said to be completely state observable if

















1
2
MMatrixityObservabil
n
CA
CA
CA
C
O

nOMrank )(
n= system order ,based on
the number of state
variable
State Observability (Example)
• Consider the system given below
• OM is obtained as
• Where
 xy
uxx
40
1
0
20
10






















CA
C
OM
 40C
   120
20
10
40 






CA
State Observability (Example)








120
40
MO
1)(sU -1
s
-1
s 1x2x
2
4
)(sY
Rank =1
n=system order =2
Output Controllability
• Output controllability describes the ability of an external
input to move the output from any initial condition to any
final condition in a finite time interval.
• Output controllability matrix (OCM) is given as
 BCABCACABCBCM n 12
O 
 
Work Out Exercise
• Check the state controllability, state observability
and output controllability of the following system
 10,
1
0
,
01
10












 CBA
256/3/2016
6/3/2016 26
Reference/Basis
6/3/2016 27
6/3/2016 28
Reference/Basis
296/3/2016
If determinant is zero , i.e singular… the system is non
observable
N=rank=3
System order=full
rank, there fore it
is observable
Finding the determinant
6/3/2016 30
Down (+)
UP (-)
Unobservability via Observability Mtrix
316/3/2016
If determinant of the observability
matrix is zero , the system is
unobservable
Calculation of Determinant
6/3/2016 32
If determinant of the observability
matrix is zero , the system is
unobservable
6/3/2016 33
346/3/2016
356/3/2016
366/3/2016
376/3/2016
386/3/2016
396/3/2016
406/3/2016
416/3/2016
All zero
column
System order =2
Rank=1
Not equal , therfore
UNOBSERVABLE
426/3/2016
436/3/2016
Identical but
negated(opposite
sign)
Identical but
negated(opposite
sign)
Controllability and Observability
Using Matlab
Prof Charlton S. Inao
• % State Space Representation % x' = Ax + Bu % y = Cx + Du % %
Problem 1 --------------------------------------------------------------- %
• Check Controllability and Observability of a 2nd order System %
• Given ------------------------------------------------------------------- MatrixA =
[0 1;-2 -3]; MatrixB = [0;1]; MatrixC = [1 -1]; MatrixD = 0; %
• Objective --------------------------------------------------------------- %
• 1) To Find Controllable Matrix Qc, its rank and check controllability
• % 2) To Find Observable Matrix Qb, its rank and check observability
%------
• --- % Controllable Matrix -----------------------------------------------------
Qc = ctrb(MatrixA,MatrixB); rankQc = rank(Qc); disp('Controllable
Matrix is Qc = '); disp(Qc); if(rankQc == rank(MatrixA)) disp('Given
System is Controllable.'); else disp('Given System is Uncontrollable');
end % Observable Matrix -------------------------------------------------------
Qb = obsv(MatrixA, MatrixC); rankQb = rank(Qb); disp('Observable
Matrix is Qb = '); disp(Qb); if(rankQb == rank(MatrixA)) disp('Given
System is Observable.'); else disp('Given System is Unobservable');
end % End of Program ----------------
Week 16 controllability and observability june 1 final
Week 16 controllability and observability june 1 final
Week 16 controllability and observability june 1 final
Week 16 controllability and observability june 1 final

Week 16 controllability and observability june 1 final