SlideShare a Scribd company logo
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
AENSI Journals
Advances in Natural and Applied Sciences
ISSN:1995-0772 EISSN: 1998-1090
Journal home page: www.aensiweb.com/ANAS
Corresponding Author: Suryakala, S., Assistant Professor, ICE Department, Sri Manakula Vinayagar Engineering College,
Pondicherry, India, 605107.
Self Tuning Regulators for a Liquid Level Process
1
S. Suryakala and 2
Dr. D. Rathikarani
1
Assistant Professor, ICE Department, Sri Manakula Vinayagar Engineering College, Pondicherry, India,605107.
2
Associate Professor, E&I Department, Annamalai University. Chidambaram, India, 608001.
ARTICLE INFO ABSTRACT
Article history:
Received 3 September 2014
Received in revised form 30 October
2014
Accepted 4 November 2014
Keywords:
Level control, Recursive least square,
Self tuning regulator, Pole placement,
model following.
Liquid level control is highly important in industrial applications. Liquid level control
using Self tuning regulator and self tuning pole placement controller is presented in this
paper. As a first step modelling of the process is highly essential for accurate control of
the process. In this paper to estimate the process parameters recursive least square
algorithm is used. Two different self tuning control algorithms using pole placement
technology are designed and implemented to control the process. The objective of this
work also includes a comparative analysis of performances of the chosen system when
implementing these two strategies under different operating regions. The design and
simulation studies are carried out in MATLAB/SIMULINK platform.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: S. Suryakala and Dr. D. Rathikarani., Self Tuning Regulators for a Liquid Level Process, Aust. J. Basic & Appl. Sci.,
8(22): 19-27, 2014
INTRODUCTION
In many industrial processes, control of liquid level is required. It was reported that about 25% of
emergency shutdowns in the nuclear power plant are caused by poor control of the steam generator water level.
Such shutdowns greatly decrease the plant availability and must be minimized. Liquid level control system is a
very complex system, because of the nonlinearities and uncertainties present in oil refinery plant, overflow of
oil can be hazardous, dangerous and costly. Empty vessels lead to pumps or drain stream processes dry.
Inaccurate measurements in mixtures processes can lead to product defects and higher costs (E.P.Gatzke 2012).
Accurate liquid level is vital in the process industries where inventories, batching and process efficiency are
critical measurements. The majority of processes met in industrial practice have stochastic character.
Traditional controllers with fixed parameters are often unsuited to such processes because their change in
parameters. Parameter changes are caused by changes in the manufacturing process, in the nature of the input
materials, fuel, machinery use (wear) etc. Fixed controllers cannot deal with this.
Adaptive control is a specific type of control, applicable to processes with changing dynamics in normal
operating conditions subjected to stochastic disturbances. Adaptive control is a specific type of control where
the process is controlled in closed loop, and where knowledge about the system characteristics are obtained on-
line while the system is operating (K.Barriljawatha 2012). The self-tuning regulator attempts to automate the
tasks involved in the adaptive control scheme namely modeling, design of a control law, implementation and
validation (Shi Jingzhuo 2011).
I. Process Description:
The piping and instrumentation diagram of real time experimental level process setup is shown in Fig. 1
Pump(P) discharges the water from the Reservoir Tank(RT) to Over Head Tank(OHT). The Process Tank(PT)
receives the water from the OHT. Flow rate is measured with Rotameter (R) at the inlet. An RF capacitance
Level Transmitter(LT) is used to measure the level in the tank (0-20cm). The output current signal (4-20 mA)
from LT is converted to corresponding digital value using a VUDAS100, USB based Data Acquisition card
(DAQ) card which is interfaced with PC as shown in Fig. 4. The digital control algorithm is developed and
configured in the controller which gives appropriate control signal. The controller output is given to digital to
analog converter(DAC) in DAQ card is used to actuate motorized control valve (MCV). The inlet flow is
manipulated by varying the stem position of the control valve in order to maintain the level of water in the
process tank.
20 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
Fig. 1: Piping and Instrumentation diagram.
HV-Hand valve; H-Heater; FT-Flow Transmitter; TT-Temperature Transmitter; S-Stirrer; TPC-Thyristor
power control; OHT-Over head tank; R-Rotameter; PT-Process tank; MCV-Motorized control valve; LT-Level
transmitter; RT-Reservoir tank.
Estimation Algorithm:
It is important to estimate the process parameters on-line in adaptive control. When operating regions
changes, the model parameters are to be estimated, so that the controller parameters are tuned accordingly.
A. Process Model:
It is assumed that the process is described by the single-input, single output (SISO) system
)
(
)
(
)
(
)
(
)
( 0
0
1
1
d
k
v
d
k
u
q
B
k
y
q
A 


 

(1)
Where
n
nq
a
q
a
q
A 





 ...
1
)
( 1
1
1
m
mq
b
q
b
q
B 





 ...
1
)
( 1
1
1
with 0
d
n
m 
 . In equation (1) y is the output, u is the input of the system, and v is the disturbance. Here
)
(
),
( 1
1 

q
B
q
A
are the polynomials in the variable
1

q
. For the process taken in this work the structure of the
process is given by
2
2
1
1
2
1
1
0
1
1
)
( 








q
a
q
a
q
b
q
b
q
H
where 0
b , 1
b are the numerator polynomial coefficients and 1
a , 2
a are the denominator polynomial
coefficients.
)
( 1

q
H
is the pulse transfer operator.
B. Least-squares Estimation Algorithm:
The least-square method is commonly used in system identification. (Deepak M.Sajnekar 2013,
M.Chidambaram 2002, Yoan D.Landau 1998). In adaptive control system the observations are obtained
sequentially in real time. Recursive estimation algorithm is desirable. It saves the computation time by using the
results obtained at time k-1 to get the estimates at time k . Hence, the recursive least-square (RLS) estimation
method is implemented. The process model which is given in equation (1) can be rewritten as
)
(
...
)
(
)
(
...
)
2
(
)
1
(
)
( 0
0
0
2
1 m
d
k
u
b
d
k
u
b
n
k
y
a
k
y
a
k
y
a
k
y m
n 












(2)
The model is linear in the parameters and can be written in the vector form as

 )
(
)
( k
k
y T

(3)
where
T
n
m a
a
a
b
b
b ]
,....,
,
,
,..
,
[ 2
1
1
0


 T
n
k
y
k
y
m
d
k
u
d
k
u
k )
(
),..
1
(
),
(
),...,
(
)
( 0
0 








The recursive least-square estimator is given by
)]
1
(
ˆ
)
(
)
(
)[
(
)
1
(
ˆ
)
(
ˆ 



 k
k
k
y
k
K
k
k T




(4)
OHT
Pump
To
R.T
H3
H2
FT
HV4
RT
HV5
HV7
PT
HV6
H1
MCV
HV1
R
HV2
HV3
TPC
LT
TT
S
1
21 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
1
))
(
)
1
(
)
(
)(
(
)
1
(
)
( 



 k
k
P
k
I
k
k
P
k
K T


 (5)
)
1
(
)
(
)]
(
)
1
(
)
(
)[
(
)
1
(
)
1
(
)
( 1






 
k
P
k
k
k
P
k
I
k
k
P
k
P
k
P T
T



 (6)
where P(k) is covariance matrix, K(k) is the Gain matrix and
)
(
ˆ k
 is the estimated parameter vector.
II. Self Tuning Regulator:
Self-tuning regulator (c1) is a well-known technique in adaptive control systems. The block diagram of self
tuning regulator is shown in fig. 2. For an adaptive controller the process parameters are to estimated for every
second and the estimated process parameters are 1
0
2
1
ˆ
,
ˆ
,
ˆ
,
ˆ b
b
a
a
and t
r
s
s ˆ
,
ˆ
,
ˆ
,
ˆ 1
1
0 are the adapted controller
parameters for every value of process parameters.
Fig. 2: Block diagram of Self tuning regulator.
A. Control Algorithm:
Linear Controller of General Structure:
The process model is described in equation (1) as
)
(
)
(
)
(
)
(
)
( 0
0
1
1
d
k
v
d
k
u
q
B
k
y
q
A 


 

(7)
Assume that the polynomials
)
( 1

q
A
and
)
( 1

q
B
are co-prime, i.e. they do not have any common factors.
Furthermore,
)
( 1

q
A
is monic. That is, that the coefficient of the highest power is unity.
A general linear controller can be described by
)
(
)
(
)
(
)
(
)
(
)
( 1
1
1
k
y
q
S
k
u
q
T
k
u
q
R c





(8)
where
)
( 1

q
R
,
)
( 1

q
S
and
)
( 1

q
T
are polynomials in the backward shift operator
1

q
. This controller
consists of a feedforward transfer operator
)
(
/
)
( 1
1 

q
R
q
T
and a feedback with the transfer operator
)
(
/
)
( 1
1 

q
R
q
S
. It thus has two degrees of freedom.[Ioan D.Ladue, 2002]
From equations (2) and (8), the following equations for the closed loop system are obtained.
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
( 1
1
1
1
1
1
1
1
1
1
1
1
k
v
q
S
q
B
q
R
q
A
q
R
q
B
k
u
q
S
q
B
q
R
q
A
q
T
q
B
k
y c 















(9)
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
( 1
1
1
1
1
1
1
1
1
1
1
1
k
v
q
S
q
B
q
R
q
A
q
S
q
B
k
u
q
S
q
B
q
R
q
A
q
T
q
A
k
u c 















(10)
Thus, the closed loop characteristic polynomial is (for simplicity, the operator
1

q
is omitted)
BS
AR
Ac 
 (11)
In equation (9)
)
(k
uc is the command signal. The key idea of the controller design is to specify the desired
closed loop characteristic polynomial Ac as a design parameter. By solving the Diophantine equation (11), the
polynomials R and S can be obtained. The closed-loop characteristic polynomial Ac determines the property
and the performance of the closed system. The Diophantine equation (11) always has solutions if the
polynomial A and B are co-prime as required and the solution may be poorly conditioned if the polynomials
have factors that are very close.
t
r
s
s ˆ
,
ˆ
,
ˆ
,
ˆ 1
1
0
Reference
Input Output
Self Tuning Regulator
Process parameters
1
0
2
1
ˆ
,
ˆ
,
ˆ
,
ˆ b
b
a
a
Specification
Controller
Design
Estimator (Recursive least
square Algorithm)
Controller
Process
22 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
B. Model Following:
The Diophantine equation (11) determines only the polynomials R and S. Other conditions must be
introduced to calculate the polynomial T in the controller equation (8). To do this, the response from the
command signal to the output follow the model which is represented by equation (12) (Karl Astrom 1998).
)
(
)
( k
u
B
k
y
A c
m
m
m  (12)
From equation (9), the following condition must hold.
m
m
c A
B
A
BT
BS
AR
BT


 (13)
It then follows from the model-following condition represented by equation (13) that the response of the
closed-loop system to command signal is specified by the model equation (12). Equation (13) implies that there
are cancellations of factors of BT and Ac. Factorize the polynomial B as


 B
B
B (14)
where

B is a monic polynomial whose zeros are stable and so well damped that they can be canceled by the
controller and

B corresponds to the unstable or poorly damped factors that cannot be canceled. Since

B
remains unchanged, it thus holds that

B must be a factor of equation (15).
'
m
m B
B
B 

(15)
Since

B is canceled, it must be a factor of c
A . Furthermore, it follows from equation (13) that, m
A is also
a factor of c
A . The closed-loop characteristic polynomial c
A thus can be rewritten as
0
A
A
B
A m
c


(16)
Since c
A and B have the common factor

B , it follows from equation (11) that it must also be a factor
of R . Hence
'
R
B
R 
 (17)
The Diophantine equation (11) then can be simplified as
c
m A
A
A
S
B
AR 

 
0
'
(18)
Substituting equations (14), (15) and (16) into equation (13), equation (19) is obtained.
0
'
A
B
T m

(19)
C. Compatibility Condition:
To have a control law that is causal in the discrete-time case, the following conditions are imposed upon the
polynomials in the control law given by equation (8).
R
S deg
deg  (20)
R
T deg
deg  (21)
In the case of no constraints on the degree of the polynomial, the Diophantine equation (11) can have
many solutions if
*
R and
*
S are two specific solutions, then so are
MB
R
R 
 *
(22)
MA
S
S 
 *
(23)
where M is an arbitrary polynomial with any degree. Since there are so many solutions, it is desirable to seek
the solution that gives a controller with the lowest degree, i.e. the minimum-degree controller. Given deg A>deg
B, it then follows from equation (11) that
A
A
R c deg
deg
deg 
 (24)
From equation (21), the degree of S is at most
1
deg 
A . This is defined as the minimum-degree solution
to the Diophantine equation (11). The condition R
S deg
deg  thus implies that
1
deg
2
deg 
 A
Ac (25)
From equation (19), the condition
R
T deg
deg  implies that
0
deg
deg
deg
deg d
B
A
B
A m
m 


 (26)
It implies that the time delay of the model must be at least as large as the time delay of the process. It is
natural that to get a solution in which the controller has the lowest possible degree. Meanwhile it is reasonable
23 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
to require that there is no extra delay in the controller. It means that the polynomials R , S and T have the same
degrees. Then, the following algorithm is implemented.
The RLS estimator computes the model parameters for various operating regions and are tabulated(Table
III). These parameters are used in the design of controllers (Self Tuning Regulator c1 and Self Tuning pole
placement controller c2).
Minimum-degreee Pole Placement (MDPP):
Data: Polynomials A and B .
Specification: Polynomials m
A , m
B and 0
A
.
Compatibility Conditions:
A
Am deg
deg  ;
B
Bm deg
deg 
1
deg
deg
deg 0 

 
B
A
A
'
m
m B
B
B 

Step 1: Decompose B as


 B
B
B
Step 2: Solve the diophantine equation below to get R' and S with
A
S deg
deg  ; m
A
A
S
B
AR 0

 
using R'and Bm', the polynomials R and T are computed
R=B+
R'
T=A0Bm'
using R,S and T polynomials the command signal is computed.
Step 3: From
'
R
B
R 
 and
'
0 m
B
A
T 
, and compute the control signal from the control law
Sy
Tu
Ru c 

D. Model following without zero cancellation:
Let the desired closed loop reference model be
2
2
1
1
1
1
0
1
1
1
1
)
(
)
(
)
( 










q
a
q
a
q
b
b
q
A
q
B
q
H
m
m
m
m
m
m
m
In this work, the self tuning regulator with no zero cancellation is designed and implemented. Since no
process zeros are cancelled,
1


B (27)
1
1
0




 q
b
b
B
B
B
Bm 
 ,where
)
1
(
/
)
1
( B
Am

 , 1
deg
deg 
 A
A and T =βA. Furthermore,
1
deg
deg
deg 0 

 B
A
A
and 0
A
T 
 . The closed loop characteristics polynomial is m
c A
A
A 0

and the Diophantine equation in Step
2 becomes
m
c A
A
A
BS
AR 0


 (28)
It also follows from the compatibility conditions that the model must have the same zero as the process.
The discrete closed loop transfer operator is
2
2
1
1
1
1
0
2
2
1
1
1
1
0
1
1
)
( 













q
a
q
a
q
b
b
q
a
q
a
q
b
b
q
H
m
m
m
m
m
m
m 
(29)
where 0
0 b
bm 
 and
1
0
2
1
1
b
b
a
a m
m





which gives unit steady state gain. Here 0
m
b , 1
m
b , 1
m
a , 2
m
a are the refence model parameters. The
Diophantine equation becomes
)
1
)(
1
(
)
)(
(
)
1
)(
1
( 1
0
2
2
1
1
1
1
0
1
1
0
1
1
2
2
1
1

















 q
a
q
a
q
a
q
s
s
q
b
b
q
r
q
a
q
a m
m (30)
Replacing 0
1 /b
b
q 
 and solving for 1
r
2
0
2
1
0
1
2
1
2
1
1
1
0
1
0
1
0
2
2
2
0
2
0
1
1
)
(
)
(
b
a
b
b
a
b
b
a
a
a
b
b
a
a
a
a
b
a
a
r m
m
m
m
c









(31)
24 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
Equating coefficients of terms
2
q
and
0
q
in equation
2
0
2
1
0
1
2
1
2
1
2
0
2
1
2
1
0
2
0
2
1
0
1
2
1
0
1
2
2
1
1
1
2
1
0
1
1
0
)
(
)
(
b
a
b
b
a
b
a
a
a
a
a
a
a
a
b
b
a
b
b
a
b
a
a
a
a
a
a
a
a
a
b
s m
m
m
m
m
c














(32)
2
0
2
1
0
1
2
1
1
2
0
1
2
0
2
2
2
2
0
2
0
2
1
0
1
2
1
2
0
2
0
2
1
2
1
1
1
1
)
(
(
b
a
b
b
a
b
a
a
a
a
a
a
a
a
a
b
b
a
b
b
a
b
a
a
a
a
a
a
a
a
b
s m
m
m
m
m
c












(33)
and
)
1
(
)
(
)
( 1
0
1
1 




 q
a
q
A
q
T c 
 (34)
III. Self Tuning Pole Placement Controller:
Self tuning pole placement controller (c2) is a discrete single input single output controller that can be used
to control systems of second and third order processes. Self tuning pole placement controller is designed for the
process with the structure shown below
2
2
1
1
2
1
1
0
1
1
)
( 








q
a
q
a
q
b
q
b
q
H
Controller specific parameters are damping factor ξ and natural frequency ω.
Control law is given by
2
1
2
2
1
1
0 )
1
( 


 




 k
k
k
k
k
k u
u
e
g
e
g
e
g
u 

The controller parameters 2
2
2
1
2
0 ,
, c
c
c g
g
g and 2
c
 are calculated by solving following diophantine equation
)
(
)
(
)
(
)
(
)
( 1
1
1
1
1 





 q
D
q
Q
q
B
q
P
q
A
where polynomials are as follows
2
2
1
1
1
ˆ
ˆ
1
)
( 




 q
a
q
a
q
A
2
1
1
0
1 ˆ
ˆ
)
( 



 q
b
q
b
q
B
)
1
)(
1
(
)
( 1
1
1 




 q
q
q
P 
2
2
2
1
2
1
2
0
1
)
( 




 q
g
q
g
g
q
Q c
c
c
2
2
1
1
1
1
)
( 




 q
d
q
d
q
D
1
for
1
cos
)
exp(
2 2
0
0
1 





 


 


 T
T
d
1
for
1
cosh
)
exp(
2 2
0
0
1 





 


 


 T
T
d
 
0
2 2
exp T
d 


Solving the diophantine equation leads to following relations for controller parameters
2
2
2
2
2
ˆ
ˆ
a
b
g c
c 

; 1
1
2
2
r
s
g c 











 1
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
2
1
1
0
2
2
1
2
2
1
a
a
b
b
g
b
a
g c
c
)
ˆ
1
(
ˆ
1
1
1
1
2
0 



 a
d
b
g c
Where
  
2
0
2
1
0
1
1
0
1
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ b
a
b
b
a
b
b
r 


    
 
1
1
1
2
0
1
0
2
1
1
1
0
2
1
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ b
d
b
d
b
b
b
a
b
a
b
b
a
s 





IV. Simulation Responses:
In this section Self Tuning Regulator(c1) and self tuning pole placement controller(c2) is implemented in
order to obtain the closed loop response of the process. The simulation of the above controllers are performed
using MATLAB/SIMULINK. In this work 0-5cm(R1), 5-10cm(R2), 10-15cm(R3) and 15-20 cm(R4) are the
various operating regions (ORs) considered for the level control. The operating regions are 0-5cm is R1, 5-
10cm is R2, 10-15cm is R3, 15-20cm is R4. R1, R2, R3, R4 are the Region1, Region2, Region3 and Region4
Respectively.
25 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
A. Process output and controller output:
The closed loop response of the process with c1 and c2 for various operating regions are shown in Fig. 3. A
disturbance of -1 cm is given at 250 sec at second operating region(R2) and 2 cm is given at 350 sec at third
region(R3).
Fig. 3: Closed loop response of the process with c1 and c2.
For the R3 and R4 ORs, The closed loop servo and regulatory response have lesser overshoot and under
shoot compared to the lower operating regions (R1,R2) and the responses which are presented in fig 3. The
closed loop response of the process with Self Tuning pole placement controller(c2) for various operating
regions have no overshoot and undershoot.
The self tuning regulator(c1) rejects disturbance faster but the self tuning pole placement controller(c2)
takes long time to reject the disturbance. The controller output for c1 and c2 for various operating regions are
shown in fig.4.
Fig. 4: Controller Output of the Self Tuning Regulator.
B. Adaptation of controller parameters:
The adaptation of controller parameters r1c1, s0c1, r1C1, s1c1, tc1 for self tuning regulator and 2
c
 , g0c2, g1c2, g2c2
for self tuning pole placement regulator for various operating regions are listed in table I. Initially at 0 second
the controller parameters are at zero and for every second the controller parameters are updated with the change
in process parameters.
Table I: Adaptation of Controller Parameters For Self Tuning Pole Placement Controller.
Region Self tuning Regulator(c1) Self tuning pole placement controller(c2)
r1c1 s0c1 s1c1 tc1
2
c
 g0c2 g1c2 g2c2
R1 -3.354 -2.405 -0.1607 -2.354 2.999 -3.118 0.6786 0.5478
R2 -3.247 -2.274 -0.1516 -2.247 2.355 -2.372 0.4961 0.01797
R3 -3.156 -2.176 -0.1475 -2.158 2.055 -1.782 0.19 0.1225
R4 -3.123 -2.128 -0.154 -2.123 2.339 -2.266 0.4083 0.2113
The adapted controller parameters r1c1, s0c1, r1C1, s1c1, tc1 for self tuninig regulator(c1) and 2
c
 , g0c2, g1c2, g2c2
for self tuning pole placement regulator(c2) the various operating regions are shown in Fig.5.
C. Estimation of model parameters:
The model parameters are a1c1, a2c1, b0c1, b1c1 for self tuning tuning regulators and a1c2, a2c2, b0c2, b1c2 for self
tuning pole placement controller for various operating regions are listed in table II. The process parameters are
updated using least square algorithm. In adaptive control for every second the process parameters are to be
26 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
estimated in order to adapt the controller parameters. Initially at 0 sec the process parameters are at zero and for
every second the process parameters are estimated and for every iteration process parameters are updated. For
0-150 sec(R1), 150-300 sec(R2), 300-400 sec(R3) and 400-500 sec (R4) are tabulated in Table II.
Fig. 5: Adaptation of the controller parameters.
Table II: Estimation Of Process Parameters For Self Tuning Pole Placement Controller.
Regio
n
Self tuning Regulator Self tuning pole placement controller
a1c1 a2c1 b0c1 b1c1 a1c2 a2c2 b0c2 b1c2
R1 -0.084 -1.305 0.159 0.3093 -1.226 0.0081 0.2398 0.7054
R2 -0.082 -1.293 0.164 0.295 -1.251 0.2292 0.2557 0.6052
R3 -0.080 -1.123 0.169 0.1246 -1.266 0.1291 0.269 0.7303
R4 -0.079 -1.237 0.172 0.2378 -1.279 0.1238 0.2821 0.7056
The adaptation of estimated model parameters a1c1, a2c1, b0c1, b1c1 for c1 and a1c2, a2c2, b0c2, b1c2 for the
various operating regions are shown in Fig. 6.
Fig. 6: Estimated Process Parameters.
V.Time Integral Criteria and simple Criteria Values:
The time integral criteria values are obtained for various operating regions. The ISE and IAE values are
obtained and the values are tabulated in Table III.
Table III: Time Integral Criteria Values For Self Tuning Regulator And Self TuningPole Placement Controller.
Region Self tuning regulator(c1) Self tuning pole placement controller(c2)
ISE IAE ITAE ISE IAE ITAE
R1 364 103.9 2240 105.8 33.04 234.5
R2 386.5 136.9 9159 168.5 57.96 4510
R3 417.2 171.4 2.08*104
247.8 105.2 2.035*104
R4 440 203.8 3.5*104
300.9 122.2 2.721*104
The simple criteria values are obtained for various operating regions and tabulated in Table IV.
Table IV: Simple Criteria Values For For Self Tuning Regulator And Self Tuning Pole Placement Controller.
Region
Self tuning regulator(c1) Self tuning pole placement controller(c2)
ts tp %Mp ts tp %Mp
R1 73 10 100 50 8 6
R2 32 7 15.73 28 12 2
R3 30 7 11.7 21 12 1.153
R4 35 7 9.5 16 12 0.294
27 S. Suryakala and Dr. D. Rathikarani, 2014
Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27
Conclusion:
This paper has dealt with the design and implementation of Self tuning regulator and self tuning pole
placement controller. The comparison of the present two controllers reveals that when comparing the time
integral criteria values for two controllers self tuning pole placement controller(c2) gives lesser ISE, IAE and
ITAE values than Self tuning regulator(c1). From the servo response it can be found that the process with
controller c2 settles faster and have no offset when comparing with c1and also it has less settling time.From the
regulatory response it can be found that c1 rejects disturbance faster than c2.
REFERENCES
Andriamalala, R.N., H. Razik and F.M. Sargos, 2008. Indirect-Rotor-Field-Oriented-Control of a Double-
Star Induction Machine using the RST controller, in the proceedings of .34th
Annual Conference on IEEE,
IECON.
Barriljawatha, K., 2012. Adaptive control technique for two tanks conical interacting system, in the
proceedings of International conference on computing and control engineering, vol. 4.
Bobal, V, J. Bohm, J. Prokop and J. Fessl, 1999. Practical Aspects of Self-Tuning Controllers: Algorithms
and Implementation. VUTIUM Press, Brno University of Technology, Brno(in Czech),.
Cuencaa, A., J. Salt, 2012. RST controller design for a non-uniform multi-rate control system. Journal of
Process Control, 22: 1865-1877.
Chidambaram, M., 2002. Computer Control of Processes. Narosa Publishing House, New Delhi,
Danijel Pavkovic, Josko Deur, Martin Jansz, Nedjeljko Peric, 2006. Adaptive control of automotive
electronic throttle. Control Engineering Practice, 14: 121-136.
Deepak M. Sajnekar, S.B. Deshpande, R.M. Mohril, 2013. Comparison of Pole Placement and Pole Zero
Cancellation Method for Tuning PID Controller of a Digital Excitation Control System, International Journal of
Scientific and Research Publications, 3(4).
Gatzke, E.P., E.S. Meadows, C. Wang and F.J. Doyle, 2000. Model based control of a four tank system.
international journal of Computer and control engineering, 24: 1503-1509.
Landau, I.D., 1998. The R-S-T digital controller design and applications. International journal of Control
Engineering Practice, 6: 155-165.
Ioan, D. Landau and Gianluca Zito, 2002. Digital Control Systems, Design, Identification and
Implementation. Springer, London.
Khanchoul, M. and M. Hilairet, 2011. “Design and comparison of different RST controllers for PMSM
control”, in the proceedings of 37th
Annual Conference on IEEE Industrial Electronics Society, IECON.
Lacroix, S., M. Hilairet and E. Laboure, 2011. Design of a battery-charger controller for electric vehicle
based on RST controller. in the proceedigs of Vehicle Power and Propulsion Conference on IEEE (VPPC).
Ming Zhou, Fuzhu Han, 2009. Adaptive control for EDM process with a self-tuning regulator.
International Journal of Machine Tools & Manufacture, 49: 462-469.
Poitiers, F., T. Bouaouiche, M. Machmoum, 2009. Advanced control of a doubly-fed induction generator
for wind energy conversion.International journal of Electric Power Systems Research, 79: 1085-1096.
Karl Astrom, Bjorn Wittenmark, 1998. Adaptive Control. Pearson Education, Second edition.
Reza Nasiri, Ahmad Radan, 2011. Adaptive decoupled control of 4-leg voltage-source inverters for
standalone photovoltaic systems: Adjusting transient state response. international journal of Renewable Energy
36,2733e2741.
Shi Jingzhuo, Liu Bo, Zhang Yu, 2011. Study on self-tuning pole assignment speed control of an ultrasonic
motor. ISA Transactions, 50: 581-587.
Yoan D. Landau, Ioan Dore Landau, 1998. Adaptive Control. Springer Verlog.

More Related Content

PDF
A Study on Performance of Different Open Loop PID Tunning Technique for a Liq...
IJITCA Journal
 
PDF
Design and Control of a Hydraulic Servo System and Simulation Analysis
IJMREMJournal
 
PPTX
Process dynamics
Shivaji Thube
 
PDF
MODEL BASED ANALYSIS OF TEMPERATURE PROCESS UNDER VARIOUS CONTROL STRATEGIES ...
Journal For Research
 
PDF
An optimal PID controller via LQR for standard second order plus time delay s...
ISA Interchange
 
PPTX
Automated process control systems
Shine Thenu
 
PPTX
Ratio controller in two conical tank interacting level system
Akhil K J
 
PDF
EHR ATTRIBUTE-BASED ACCESS CONTROL (ABAC) FOR FOG COMPUTING ENVIRONMENT
csandit
 
A Study on Performance of Different Open Loop PID Tunning Technique for a Liq...
IJITCA Journal
 
Design and Control of a Hydraulic Servo System and Simulation Analysis
IJMREMJournal
 
Process dynamics
Shivaji Thube
 
MODEL BASED ANALYSIS OF TEMPERATURE PROCESS UNDER VARIOUS CONTROL STRATEGIES ...
Journal For Research
 
An optimal PID controller via LQR for standard second order plus time delay s...
ISA Interchange
 
Automated process control systems
Shine Thenu
 
Ratio controller in two conical tank interacting level system
Akhil K J
 
EHR ATTRIBUTE-BASED ACCESS CONTROL (ABAC) FOR FOG COMPUTING ENVIRONMENT
csandit
 

What's hot (18)

PPT
Instrumentation tech 1
heinzawwin
 
PDF
C045051318
IJERA Editor
 
DOCX
Process Control and instrumentation
Paul O Gorman
 
PDF
IJRTER_KSK
senthil0888
 
PDF
comparative analysis of pid and narma l2 controllers for shell and tube heat...
INFOGAIN PUBLICATION
 
PDF
PSO based NNIMC for a Conical Tank Level Process
IRJET Journal
 
PDF
10.1.1.193.2962
aboma2hawi
 
PPTX
Comparative analysis of P/PI/PID controllers for pH neutralization process
Chandra Shekhar
 
PPT
How to Setup and Adjust the Dynamic Compensation of Feedforward Signals
Jim Cahill
 
PPTX
Process Design and control
Rami Bechara
 
PPT
Control Loop Foundation for Batch and Continuous Control
Jim Cahill
 
PDF
Disturbance Rejection with a Highly Oscillating Second-Order Process, Part I...
Scientific Review SR
 
PPT
PID Control of Runaway Processes - Greg McMillan Deminar
Jim Cahill
 
PDF
An Adaptive Liquid Level Controller Using Multi Sensor Data Fusion
TELKOMNIKA JOURNAL
 
PDF
D04954148
IOSR-JEN
 
PPT
PID Tuning for Near Integrating Processes - Greg McMillan Deminar
Jim Cahill
 
PPTX
Bioreactor control system
nandhujaan
 
PPTX
pH Control Solutions - Greg McMillan
Jim Cahill
 
Instrumentation tech 1
heinzawwin
 
C045051318
IJERA Editor
 
Process Control and instrumentation
Paul O Gorman
 
IJRTER_KSK
senthil0888
 
comparative analysis of pid and narma l2 controllers for shell and tube heat...
INFOGAIN PUBLICATION
 
PSO based NNIMC for a Conical Tank Level Process
IRJET Journal
 
10.1.1.193.2962
aboma2hawi
 
Comparative analysis of P/PI/PID controllers for pH neutralization process
Chandra Shekhar
 
How to Setup and Adjust the Dynamic Compensation of Feedforward Signals
Jim Cahill
 
Process Design and control
Rami Bechara
 
Control Loop Foundation for Batch and Continuous Control
Jim Cahill
 
Disturbance Rejection with a Highly Oscillating Second-Order Process, Part I...
Scientific Review SR
 
PID Control of Runaway Processes - Greg McMillan Deminar
Jim Cahill
 
An Adaptive Liquid Level Controller Using Multi Sensor Data Fusion
TELKOMNIKA JOURNAL
 
D04954148
IOSR-JEN
 
PID Tuning for Near Integrating Processes - Greg McMillan Deminar
Jim Cahill
 
Bioreactor control system
nandhujaan
 
pH Control Solutions - Greg McMillan
Jim Cahill
 
Ad

Similar to 10.1.1.1039.4745 (20)

PPTX
1. Process Dynamics.pptx
AravindanMohan4
 
PDF
A New Adaptive PID Controller
HAKAN CELEP
 
DOCX
Process control examples and applications
Amr Seif
 
PPTX
PDC NOTES (JAN 2021).pptx
RITIKA161174
 
PDF
Process Dynamics and Control
CHINTTANPUBLICATIONS
 
PDF
PlC and automation 2015 table of contents
CHINTTANPUBLICATIONS
 
PDF
Control of an unstable batch chemical reactor
DayromGMiranda
 
PPTX
THE CONTROL SYSTEM
Sunny Chauhan
 
PDF
Pid controlbook
Phiêu Lãng Giang Hồ
 
DOCX
--Liquid level in a tank.docx ddd dddddds
uaizaz70
 
PDF
Top Read Articles in Information & Technology : July 2021
IJITCA Journal
 
PDF
Control engineering a guide for beginners
thuanvq
 
PDF
UROP MPC Report
Sebastian Gonzato
 
PDF
Nonlinear batch reactor temperature control based on adaptive feedback based ilc
ijics
 
PDF
NONLINEAR BATCH REACTOR TEMPERATURE CONTROL BASED ON ADAPTIVE FEEDBACK-BASED ILC
ijcisjournal
 
PDF
A STUDY ON PERFORMANCE OF DIFFERENT OPEN LOOP PID TUNNING TECHNIQUE FOR A LIQ...
IJITCA Journal
 
PDF
A STUDY ON PERFORMANCE OF DIFFERENT OPEN LOOP PID TUNNING TECHNIQUE FOR A LI...
IJITCA Journal
 
PDF
Design and control of steam flow in cement production process using neural ne...
Mustefa Jibril
 
PDF
TOC I&ECPDD Oct67
Pierre Latour
 
PPTX
Process Control in Chemical Engineering by MATLAB
priyachemical
 
1. Process Dynamics.pptx
AravindanMohan4
 
A New Adaptive PID Controller
HAKAN CELEP
 
Process control examples and applications
Amr Seif
 
PDC NOTES (JAN 2021).pptx
RITIKA161174
 
Process Dynamics and Control
CHINTTANPUBLICATIONS
 
PlC and automation 2015 table of contents
CHINTTANPUBLICATIONS
 
Control of an unstable batch chemical reactor
DayromGMiranda
 
THE CONTROL SYSTEM
Sunny Chauhan
 
Pid controlbook
Phiêu Lãng Giang Hồ
 
--Liquid level in a tank.docx ddd dddddds
uaizaz70
 
Top Read Articles in Information & Technology : July 2021
IJITCA Journal
 
Control engineering a guide for beginners
thuanvq
 
UROP MPC Report
Sebastian Gonzato
 
Nonlinear batch reactor temperature control based on adaptive feedback based ilc
ijics
 
NONLINEAR BATCH REACTOR TEMPERATURE CONTROL BASED ON ADAPTIVE FEEDBACK-BASED ILC
ijcisjournal
 
A STUDY ON PERFORMANCE OF DIFFERENT OPEN LOOP PID TUNNING TECHNIQUE FOR A LIQ...
IJITCA Journal
 
A STUDY ON PERFORMANCE OF DIFFERENT OPEN LOOP PID TUNNING TECHNIQUE FOR A LI...
IJITCA Journal
 
Design and control of steam flow in cement production process using neural ne...
Mustefa Jibril
 
TOC I&ECPDD Oct67
Pierre Latour
 
Process Control in Chemical Engineering by MATLAB
priyachemical
 
Ad

More from aboma2hawi (13)

PPT
MATLAB_CIS601-03.ppt
aboma2hawi
 
PPTX
Introduction_to_Matlab_lecture.pptx
aboma2hawi
 
PPTX
programming_tutorial_course_ lesson_1.pptx
aboma2hawi
 
PPTX
Matlab-3.pptx
aboma2hawi
 
PPT
matlab_tutorial.ppt
aboma2hawi
 
PPTX
Matlab-1.pptx
aboma2hawi
 
PPTX
HDP Module One (1).pptx
aboma2hawi
 
PPT
5_2019_01_12!09_25_57_AM.ppt
aboma2hawi
 
PDF
08822428
aboma2hawi
 
PDF
08764396
aboma2hawi
 
PDF
109 me0422
aboma2hawi
 
PDF
Step response plot of dynamic system; step response data matlab step
aboma2hawi
 
PDF
Lab 4 matlab for controls state space analysis
aboma2hawi
 
MATLAB_CIS601-03.ppt
aboma2hawi
 
Introduction_to_Matlab_lecture.pptx
aboma2hawi
 
programming_tutorial_course_ lesson_1.pptx
aboma2hawi
 
Matlab-3.pptx
aboma2hawi
 
matlab_tutorial.ppt
aboma2hawi
 
Matlab-1.pptx
aboma2hawi
 
HDP Module One (1).pptx
aboma2hawi
 
5_2019_01_12!09_25_57_AM.ppt
aboma2hawi
 
08822428
aboma2hawi
 
08764396
aboma2hawi
 
109 me0422
aboma2hawi
 
Step response plot of dynamic system; step response data matlab step
aboma2hawi
 
Lab 4 matlab for controls state space analysis
aboma2hawi
 

Recently uploaded (20)

PDF
settlement FOR FOUNDATION ENGINEERS.pdf
Endalkazene
 
PPTX
IoT_Smart_Agriculture_Presentations.pptx
poojakumari696707
 
PPTX
database slide on modern techniques for optimizing database queries.pptx
aky52024
 
PDF
Cryptography and Information :Security Fundamentals
Dr. Madhuri Jawale
 
PPTX
Civil Engineering Practices_BY Sh.JP Mishra 23.09.pptx
bineetmishra1990
 
PDF
2010_Book_EnvironmentalBioengineering (1).pdf
EmilianoRodriguezTll
 
PDF
dse_final_merit_2025_26 gtgfffffcjjjuuyy
rushabhjain127
 
PDF
top-5-use-cases-for-splunk-security-analytics.pdf
yaghutialireza
 
PPTX
Module2 Data Base Design- ER and NF.pptx
gomathisankariv2
 
PPTX
Inventory management chapter in automation and robotics.
atisht0104
 
PDF
Unit I Part II.pdf : Security Fundamentals
Dr. Madhuri Jawale
 
PDF
2025 Laurence Sigler - Advancing Decision Support. Content Management Ecommer...
Francisco Javier Mora Serrano
 
PDF
EVS+PRESENTATIONS EVS+PRESENTATIONS like
saiyedaqib429
 
PPTX
business incubation centre aaaaaaaaaaaaaa
hodeeesite4
 
PDF
Introduction to Ship Engine Room Systems.pdf
Mahmoud Moghtaderi
 
PDF
July 2025: Top 10 Read Articles Advanced Information Technology
ijait
 
PDF
FLEX-LNG-Company-Presentation-Nov-2017.pdf
jbloggzs
 
PDF
67243-Cooling and Heating & Calculation.pdf
DHAKA POLYTECHNIC
 
PDF
Zero Carbon Building Performance standard
BassemOsman1
 
PPT
1. SYSTEMS, ROLES, AND DEVELOPMENT METHODOLOGIES.ppt
zilow058
 
settlement FOR FOUNDATION ENGINEERS.pdf
Endalkazene
 
IoT_Smart_Agriculture_Presentations.pptx
poojakumari696707
 
database slide on modern techniques for optimizing database queries.pptx
aky52024
 
Cryptography and Information :Security Fundamentals
Dr. Madhuri Jawale
 
Civil Engineering Practices_BY Sh.JP Mishra 23.09.pptx
bineetmishra1990
 
2010_Book_EnvironmentalBioengineering (1).pdf
EmilianoRodriguezTll
 
dse_final_merit_2025_26 gtgfffffcjjjuuyy
rushabhjain127
 
top-5-use-cases-for-splunk-security-analytics.pdf
yaghutialireza
 
Module2 Data Base Design- ER and NF.pptx
gomathisankariv2
 
Inventory management chapter in automation and robotics.
atisht0104
 
Unit I Part II.pdf : Security Fundamentals
Dr. Madhuri Jawale
 
2025 Laurence Sigler - Advancing Decision Support. Content Management Ecommer...
Francisco Javier Mora Serrano
 
EVS+PRESENTATIONS EVS+PRESENTATIONS like
saiyedaqib429
 
business incubation centre aaaaaaaaaaaaaa
hodeeesite4
 
Introduction to Ship Engine Room Systems.pdf
Mahmoud Moghtaderi
 
July 2025: Top 10 Read Articles Advanced Information Technology
ijait
 
FLEX-LNG-Company-Presentation-Nov-2017.pdf
jbloggzs
 
67243-Cooling and Heating & Calculation.pdf
DHAKA POLYTECHNIC
 
Zero Carbon Building Performance standard
BassemOsman1
 
1. SYSTEMS, ROLES, AND DEVELOPMENT METHODOLOGIES.ppt
zilow058
 

10.1.1.1039.4745

  • 1. Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 AENSI Journals Advances in Natural and Applied Sciences ISSN:1995-0772 EISSN: 1998-1090 Journal home page: www.aensiweb.com/ANAS Corresponding Author: Suryakala, S., Assistant Professor, ICE Department, Sri Manakula Vinayagar Engineering College, Pondicherry, India, 605107. Self Tuning Regulators for a Liquid Level Process 1 S. Suryakala and 2 Dr. D. Rathikarani 1 Assistant Professor, ICE Department, Sri Manakula Vinayagar Engineering College, Pondicherry, India,605107. 2 Associate Professor, E&I Department, Annamalai University. Chidambaram, India, 608001. ARTICLE INFO ABSTRACT Article history: Received 3 September 2014 Received in revised form 30 October 2014 Accepted 4 November 2014 Keywords: Level control, Recursive least square, Self tuning regulator, Pole placement, model following. Liquid level control is highly important in industrial applications. Liquid level control using Self tuning regulator and self tuning pole placement controller is presented in this paper. As a first step modelling of the process is highly essential for accurate control of the process. In this paper to estimate the process parameters recursive least square algorithm is used. Two different self tuning control algorithms using pole placement technology are designed and implemented to control the process. The objective of this work also includes a comparative analysis of performances of the chosen system when implementing these two strategies under different operating regions. The design and simulation studies are carried out in MATLAB/SIMULINK platform. © 2014 AENSI Publisher All rights reserved. To Cite This Article: S. Suryakala and Dr. D. Rathikarani., Self Tuning Regulators for a Liquid Level Process, Aust. J. Basic & Appl. Sci., 8(22): 19-27, 2014 INTRODUCTION In many industrial processes, control of liquid level is required. It was reported that about 25% of emergency shutdowns in the nuclear power plant are caused by poor control of the steam generator water level. Such shutdowns greatly decrease the plant availability and must be minimized. Liquid level control system is a very complex system, because of the nonlinearities and uncertainties present in oil refinery plant, overflow of oil can be hazardous, dangerous and costly. Empty vessels lead to pumps or drain stream processes dry. Inaccurate measurements in mixtures processes can lead to product defects and higher costs (E.P.Gatzke 2012). Accurate liquid level is vital in the process industries where inventories, batching and process efficiency are critical measurements. The majority of processes met in industrial practice have stochastic character. Traditional controllers with fixed parameters are often unsuited to such processes because their change in parameters. Parameter changes are caused by changes in the manufacturing process, in the nature of the input materials, fuel, machinery use (wear) etc. Fixed controllers cannot deal with this. Adaptive control is a specific type of control, applicable to processes with changing dynamics in normal operating conditions subjected to stochastic disturbances. Adaptive control is a specific type of control where the process is controlled in closed loop, and where knowledge about the system characteristics are obtained on- line while the system is operating (K.Barriljawatha 2012). The self-tuning regulator attempts to automate the tasks involved in the adaptive control scheme namely modeling, design of a control law, implementation and validation (Shi Jingzhuo 2011). I. Process Description: The piping and instrumentation diagram of real time experimental level process setup is shown in Fig. 1 Pump(P) discharges the water from the Reservoir Tank(RT) to Over Head Tank(OHT). The Process Tank(PT) receives the water from the OHT. Flow rate is measured with Rotameter (R) at the inlet. An RF capacitance Level Transmitter(LT) is used to measure the level in the tank (0-20cm). The output current signal (4-20 mA) from LT is converted to corresponding digital value using a VUDAS100, USB based Data Acquisition card (DAQ) card which is interfaced with PC as shown in Fig. 4. The digital control algorithm is developed and configured in the controller which gives appropriate control signal. The controller output is given to digital to analog converter(DAC) in DAQ card is used to actuate motorized control valve (MCV). The inlet flow is manipulated by varying the stem position of the control valve in order to maintain the level of water in the process tank.
  • 2. 20 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 Fig. 1: Piping and Instrumentation diagram. HV-Hand valve; H-Heater; FT-Flow Transmitter; TT-Temperature Transmitter; S-Stirrer; TPC-Thyristor power control; OHT-Over head tank; R-Rotameter; PT-Process tank; MCV-Motorized control valve; LT-Level transmitter; RT-Reservoir tank. Estimation Algorithm: It is important to estimate the process parameters on-line in adaptive control. When operating regions changes, the model parameters are to be estimated, so that the controller parameters are tuned accordingly. A. Process Model: It is assumed that the process is described by the single-input, single output (SISO) system ) ( ) ( ) ( ) ( ) ( 0 0 1 1 d k v d k u q B k y q A       (1) Where n nq a q a q A        ... 1 ) ( 1 1 1 m mq b q b q B        ... 1 ) ( 1 1 1 with 0 d n m   . In equation (1) y is the output, u is the input of the system, and v is the disturbance. Here ) ( ), ( 1 1   q B q A are the polynomials in the variable 1  q . For the process taken in this work the structure of the process is given by 2 2 1 1 2 1 1 0 1 1 ) (          q a q a q b q b q H where 0 b , 1 b are the numerator polynomial coefficients and 1 a , 2 a are the denominator polynomial coefficients. ) ( 1  q H is the pulse transfer operator. B. Least-squares Estimation Algorithm: The least-square method is commonly used in system identification. (Deepak M.Sajnekar 2013, M.Chidambaram 2002, Yoan D.Landau 1998). In adaptive control system the observations are obtained sequentially in real time. Recursive estimation algorithm is desirable. It saves the computation time by using the results obtained at time k-1 to get the estimates at time k . Hence, the recursive least-square (RLS) estimation method is implemented. The process model which is given in equation (1) can be rewritten as ) ( ... ) ( ) ( ... ) 2 ( ) 1 ( ) ( 0 0 0 2 1 m d k u b d k u b n k y a k y a k y a k y m n              (2) The model is linear in the parameters and can be written in the vector form as   ) ( ) ( k k y T  (3) where T n m a a a b b b ] ,...., , , ,.. , [ 2 1 1 0    T n k y k y m d k u d k u k ) ( ),.. 1 ( ), ( ),..., ( ) ( 0 0          The recursive least-square estimator is given by )] 1 ( ˆ ) ( ) ( )[ ( ) 1 ( ˆ ) ( ˆ      k k k y k K k k T     (4) OHT Pump To R.T H3 H2 FT HV4 RT HV5 HV7 PT HV6 H1 MCV HV1 R HV2 HV3 TPC LT TT S 1
  • 3. 21 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 1 )) ( ) 1 ( ) ( )( ( ) 1 ( ) (      k k P k I k k P k K T    (5) ) 1 ( ) ( )] ( ) 1 ( ) ( )[ ( ) 1 ( ) 1 ( ) ( 1         k P k k k P k I k k P k P k P T T     (6) where P(k) is covariance matrix, K(k) is the Gain matrix and ) ( ˆ k  is the estimated parameter vector. II. Self Tuning Regulator: Self-tuning regulator (c1) is a well-known technique in adaptive control systems. The block diagram of self tuning regulator is shown in fig. 2. For an adaptive controller the process parameters are to estimated for every second and the estimated process parameters are 1 0 2 1 ˆ , ˆ , ˆ , ˆ b b a a and t r s s ˆ , ˆ , ˆ , ˆ 1 1 0 are the adapted controller parameters for every value of process parameters. Fig. 2: Block diagram of Self tuning regulator. A. Control Algorithm: Linear Controller of General Structure: The process model is described in equation (1) as ) ( ) ( ) ( ) ( ) ( 0 0 1 1 d k v d k u q B k y q A       (7) Assume that the polynomials ) ( 1  q A and ) ( 1  q B are co-prime, i.e. they do not have any common factors. Furthermore, ) ( 1  q A is monic. That is, that the coefficient of the highest power is unity. A general linear controller can be described by ) ( ) ( ) ( ) ( ) ( ) ( 1 1 1 k y q S k u q T k u q R c      (8) where ) ( 1  q R , ) ( 1  q S and ) ( 1  q T are polynomials in the backward shift operator 1  q . This controller consists of a feedforward transfer operator ) ( / ) ( 1 1   q R q T and a feedback with the transfer operator ) ( / ) ( 1 1   q R q S . It thus has two degrees of freedom.[Ioan D.Ladue, 2002] From equations (2) and (8), the following equations for the closed loop system are obtained. ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( 1 1 1 1 1 1 1 1 1 1 1 1 k v q S q B q R q A q R q B k u q S q B q R q A q T q B k y c                 (9) ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( 1 1 1 1 1 1 1 1 1 1 1 1 k v q S q B q R q A q S q B k u q S q B q R q A q T q A k u c                 (10) Thus, the closed loop characteristic polynomial is (for simplicity, the operator 1  q is omitted) BS AR Ac   (11) In equation (9) ) (k uc is the command signal. The key idea of the controller design is to specify the desired closed loop characteristic polynomial Ac as a design parameter. By solving the Diophantine equation (11), the polynomials R and S can be obtained. The closed-loop characteristic polynomial Ac determines the property and the performance of the closed system. The Diophantine equation (11) always has solutions if the polynomial A and B are co-prime as required and the solution may be poorly conditioned if the polynomials have factors that are very close. t r s s ˆ , ˆ , ˆ , ˆ 1 1 0 Reference Input Output Self Tuning Regulator Process parameters 1 0 2 1 ˆ , ˆ , ˆ , ˆ b b a a Specification Controller Design Estimator (Recursive least square Algorithm) Controller Process
  • 4. 22 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 B. Model Following: The Diophantine equation (11) determines only the polynomials R and S. Other conditions must be introduced to calculate the polynomial T in the controller equation (8). To do this, the response from the command signal to the output follow the model which is represented by equation (12) (Karl Astrom 1998). ) ( ) ( k u B k y A c m m m  (12) From equation (9), the following condition must hold. m m c A B A BT BS AR BT    (13) It then follows from the model-following condition represented by equation (13) that the response of the closed-loop system to command signal is specified by the model equation (12). Equation (13) implies that there are cancellations of factors of BT and Ac. Factorize the polynomial B as    B B B (14) where  B is a monic polynomial whose zeros are stable and so well damped that they can be canceled by the controller and  B corresponds to the unstable or poorly damped factors that cannot be canceled. Since  B remains unchanged, it thus holds that  B must be a factor of equation (15). ' m m B B B   (15) Since  B is canceled, it must be a factor of c A . Furthermore, it follows from equation (13) that, m A is also a factor of c A . The closed-loop characteristic polynomial c A thus can be rewritten as 0 A A B A m c   (16) Since c A and B have the common factor  B , it follows from equation (11) that it must also be a factor of R . Hence ' R B R   (17) The Diophantine equation (11) then can be simplified as c m A A A S B AR     0 ' (18) Substituting equations (14), (15) and (16) into equation (13), equation (19) is obtained. 0 ' A B T m  (19) C. Compatibility Condition: To have a control law that is causal in the discrete-time case, the following conditions are imposed upon the polynomials in the control law given by equation (8). R S deg deg  (20) R T deg deg  (21) In the case of no constraints on the degree of the polynomial, the Diophantine equation (11) can have many solutions if * R and * S are two specific solutions, then so are MB R R   * (22) MA S S   * (23) where M is an arbitrary polynomial with any degree. Since there are so many solutions, it is desirable to seek the solution that gives a controller with the lowest degree, i.e. the minimum-degree controller. Given deg A>deg B, it then follows from equation (11) that A A R c deg deg deg   (24) From equation (21), the degree of S is at most 1 deg  A . This is defined as the minimum-degree solution to the Diophantine equation (11). The condition R S deg deg  thus implies that 1 deg 2 deg   A Ac (25) From equation (19), the condition R T deg deg  implies that 0 deg deg deg deg d B A B A m m     (26) It implies that the time delay of the model must be at least as large as the time delay of the process. It is natural that to get a solution in which the controller has the lowest possible degree. Meanwhile it is reasonable
  • 5. 23 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 to require that there is no extra delay in the controller. It means that the polynomials R , S and T have the same degrees. Then, the following algorithm is implemented. The RLS estimator computes the model parameters for various operating regions and are tabulated(Table III). These parameters are used in the design of controllers (Self Tuning Regulator c1 and Self Tuning pole placement controller c2). Minimum-degreee Pole Placement (MDPP): Data: Polynomials A and B . Specification: Polynomials m A , m B and 0 A . Compatibility Conditions: A Am deg deg  ; B Bm deg deg  1 deg deg deg 0     B A A ' m m B B B   Step 1: Decompose B as    B B B Step 2: Solve the diophantine equation below to get R' and S with A S deg deg  ; m A A S B AR 0    using R'and Bm', the polynomials R and T are computed R=B+ R' T=A0Bm' using R,S and T polynomials the command signal is computed. Step 3: From ' R B R   and ' 0 m B A T  , and compute the control signal from the control law Sy Tu Ru c   D. Model following without zero cancellation: Let the desired closed loop reference model be 2 2 1 1 1 1 0 1 1 1 1 ) ( ) ( ) (            q a q a q b b q A q B q H m m m m m m m In this work, the self tuning regulator with no zero cancellation is designed and implemented. Since no process zeros are cancelled, 1   B (27) 1 1 0      q b b B B B Bm   ,where ) 1 ( / ) 1 ( B Am   , 1 deg deg   A A and T =βA. Furthermore, 1 deg deg deg 0    B A A and 0 A T   . The closed loop characteristics polynomial is m c A A A 0  and the Diophantine equation in Step 2 becomes m c A A A BS AR 0    (28) It also follows from the compatibility conditions that the model must have the same zero as the process. The discrete closed loop transfer operator is 2 2 1 1 1 1 0 2 2 1 1 1 1 0 1 1 ) (               q a q a q b b q a q a q b b q H m m m m m m m  (29) where 0 0 b bm   and 1 0 2 1 1 b b a a m m      which gives unit steady state gain. Here 0 m b , 1 m b , 1 m a , 2 m a are the refence model parameters. The Diophantine equation becomes ) 1 )( 1 ( ) )( ( ) 1 )( 1 ( 1 0 2 2 1 1 1 1 0 1 1 0 1 1 2 2 1 1                   q a q a q a q s s q b b q r q a q a m m (30) Replacing 0 1 /b b q   and solving for 1 r 2 0 2 1 0 1 2 1 2 1 1 1 0 1 0 1 0 2 2 2 0 2 0 1 1 ) ( ) ( b a b b a b b a a a b b a a a a b a a r m m m m c          (31)
  • 6. 24 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 Equating coefficients of terms 2 q and 0 q in equation 2 0 2 1 0 1 2 1 2 1 2 0 2 1 2 1 0 2 0 2 1 0 1 2 1 0 1 2 2 1 1 1 2 1 0 1 1 0 ) ( ) ( b a b b a b a a a a a a a a b b a b b a b a a a a a a a a a b s m m m m m c               (32) 2 0 2 1 0 1 2 1 1 2 0 1 2 0 2 2 2 2 0 2 0 2 1 0 1 2 1 2 0 2 0 2 1 2 1 1 1 1 ) ( ( b a b b a b a a a a a a a a a b b a b b a b a a a a a a a a b s m m m m m c             (33) and ) 1 ( ) ( ) ( 1 0 1 1       q a q A q T c   (34) III. Self Tuning Pole Placement Controller: Self tuning pole placement controller (c2) is a discrete single input single output controller that can be used to control systems of second and third order processes. Self tuning pole placement controller is designed for the process with the structure shown below 2 2 1 1 2 1 1 0 1 1 ) (          q a q a q b q b q H Controller specific parameters are damping factor ξ and natural frequency ω. Control law is given by 2 1 2 2 1 1 0 ) 1 (           k k k k k k u u e g e g e g u   The controller parameters 2 2 2 1 2 0 , , c c c g g g and 2 c  are calculated by solving following diophantine equation ) ( ) ( ) ( ) ( ) ( 1 1 1 1 1        q D q Q q B q P q A where polynomials are as follows 2 2 1 1 1 ˆ ˆ 1 ) (       q a q a q A 2 1 1 0 1 ˆ ˆ ) (      q b q b q B ) 1 )( 1 ( ) ( 1 1 1       q q q P  2 2 2 1 2 1 2 0 1 ) (       q g q g g q Q c c c 2 2 1 1 1 1 ) (       q d q d q D 1 for 1 cos ) exp( 2 2 0 0 1                T T d 1 for 1 cosh ) exp( 2 2 0 0 1                T T d   0 2 2 exp T d    Solving the diophantine equation leads to following relations for controller parameters 2 2 2 2 2 ˆ ˆ a b g c c   ; 1 1 2 2 r s g c              1 ˆ ˆ ˆ ˆ ˆ ˆ 2 1 1 0 2 2 1 2 2 1 a a b b g b a g c c ) ˆ 1 ( ˆ 1 1 1 1 2 0      a d b g c Where    2 0 2 1 0 1 1 0 1 ˆ ˆ ˆ ˆ ˆ ˆ ˆ b a b b a b b r           1 1 1 2 0 1 0 2 1 1 1 0 2 1 ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ b d b d b b b a b a b b a s       IV. Simulation Responses: In this section Self Tuning Regulator(c1) and self tuning pole placement controller(c2) is implemented in order to obtain the closed loop response of the process. The simulation of the above controllers are performed using MATLAB/SIMULINK. In this work 0-5cm(R1), 5-10cm(R2), 10-15cm(R3) and 15-20 cm(R4) are the various operating regions (ORs) considered for the level control. The operating regions are 0-5cm is R1, 5- 10cm is R2, 10-15cm is R3, 15-20cm is R4. R1, R2, R3, R4 are the Region1, Region2, Region3 and Region4 Respectively.
  • 7. 25 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 A. Process output and controller output: The closed loop response of the process with c1 and c2 for various operating regions are shown in Fig. 3. A disturbance of -1 cm is given at 250 sec at second operating region(R2) and 2 cm is given at 350 sec at third region(R3). Fig. 3: Closed loop response of the process with c1 and c2. For the R3 and R4 ORs, The closed loop servo and regulatory response have lesser overshoot and under shoot compared to the lower operating regions (R1,R2) and the responses which are presented in fig 3. The closed loop response of the process with Self Tuning pole placement controller(c2) for various operating regions have no overshoot and undershoot. The self tuning regulator(c1) rejects disturbance faster but the self tuning pole placement controller(c2) takes long time to reject the disturbance. The controller output for c1 and c2 for various operating regions are shown in fig.4. Fig. 4: Controller Output of the Self Tuning Regulator. B. Adaptation of controller parameters: The adaptation of controller parameters r1c1, s0c1, r1C1, s1c1, tc1 for self tuning regulator and 2 c  , g0c2, g1c2, g2c2 for self tuning pole placement regulator for various operating regions are listed in table I. Initially at 0 second the controller parameters are at zero and for every second the controller parameters are updated with the change in process parameters. Table I: Adaptation of Controller Parameters For Self Tuning Pole Placement Controller. Region Self tuning Regulator(c1) Self tuning pole placement controller(c2) r1c1 s0c1 s1c1 tc1 2 c  g0c2 g1c2 g2c2 R1 -3.354 -2.405 -0.1607 -2.354 2.999 -3.118 0.6786 0.5478 R2 -3.247 -2.274 -0.1516 -2.247 2.355 -2.372 0.4961 0.01797 R3 -3.156 -2.176 -0.1475 -2.158 2.055 -1.782 0.19 0.1225 R4 -3.123 -2.128 -0.154 -2.123 2.339 -2.266 0.4083 0.2113 The adapted controller parameters r1c1, s0c1, r1C1, s1c1, tc1 for self tuninig regulator(c1) and 2 c  , g0c2, g1c2, g2c2 for self tuning pole placement regulator(c2) the various operating regions are shown in Fig.5. C. Estimation of model parameters: The model parameters are a1c1, a2c1, b0c1, b1c1 for self tuning tuning regulators and a1c2, a2c2, b0c2, b1c2 for self tuning pole placement controller for various operating regions are listed in table II. The process parameters are updated using least square algorithm. In adaptive control for every second the process parameters are to be
  • 8. 26 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 estimated in order to adapt the controller parameters. Initially at 0 sec the process parameters are at zero and for every second the process parameters are estimated and for every iteration process parameters are updated. For 0-150 sec(R1), 150-300 sec(R2), 300-400 sec(R3) and 400-500 sec (R4) are tabulated in Table II. Fig. 5: Adaptation of the controller parameters. Table II: Estimation Of Process Parameters For Self Tuning Pole Placement Controller. Regio n Self tuning Regulator Self tuning pole placement controller a1c1 a2c1 b0c1 b1c1 a1c2 a2c2 b0c2 b1c2 R1 -0.084 -1.305 0.159 0.3093 -1.226 0.0081 0.2398 0.7054 R2 -0.082 -1.293 0.164 0.295 -1.251 0.2292 0.2557 0.6052 R3 -0.080 -1.123 0.169 0.1246 -1.266 0.1291 0.269 0.7303 R4 -0.079 -1.237 0.172 0.2378 -1.279 0.1238 0.2821 0.7056 The adaptation of estimated model parameters a1c1, a2c1, b0c1, b1c1 for c1 and a1c2, a2c2, b0c2, b1c2 for the various operating regions are shown in Fig. 6. Fig. 6: Estimated Process Parameters. V.Time Integral Criteria and simple Criteria Values: The time integral criteria values are obtained for various operating regions. The ISE and IAE values are obtained and the values are tabulated in Table III. Table III: Time Integral Criteria Values For Self Tuning Regulator And Self TuningPole Placement Controller. Region Self tuning regulator(c1) Self tuning pole placement controller(c2) ISE IAE ITAE ISE IAE ITAE R1 364 103.9 2240 105.8 33.04 234.5 R2 386.5 136.9 9159 168.5 57.96 4510 R3 417.2 171.4 2.08*104 247.8 105.2 2.035*104 R4 440 203.8 3.5*104 300.9 122.2 2.721*104 The simple criteria values are obtained for various operating regions and tabulated in Table IV. Table IV: Simple Criteria Values For For Self Tuning Regulator And Self Tuning Pole Placement Controller. Region Self tuning regulator(c1) Self tuning pole placement controller(c2) ts tp %Mp ts tp %Mp R1 73 10 100 50 8 6 R2 32 7 15.73 28 12 2 R3 30 7 11.7 21 12 1.153 R4 35 7 9.5 16 12 0.294
  • 9. 27 S. Suryakala and Dr. D. Rathikarani, 2014 Advances in Natural and Applied Sciences, 8(22) Special 2014, Pages: 19-27 Conclusion: This paper has dealt with the design and implementation of Self tuning regulator and self tuning pole placement controller. The comparison of the present two controllers reveals that when comparing the time integral criteria values for two controllers self tuning pole placement controller(c2) gives lesser ISE, IAE and ITAE values than Self tuning regulator(c1). From the servo response it can be found that the process with controller c2 settles faster and have no offset when comparing with c1and also it has less settling time.From the regulatory response it can be found that c1 rejects disturbance faster than c2. REFERENCES Andriamalala, R.N., H. Razik and F.M. Sargos, 2008. Indirect-Rotor-Field-Oriented-Control of a Double- Star Induction Machine using the RST controller, in the proceedings of .34th Annual Conference on IEEE, IECON. Barriljawatha, K., 2012. Adaptive control technique for two tanks conical interacting system, in the proceedings of International conference on computing and control engineering, vol. 4. Bobal, V, J. Bohm, J. Prokop and J. Fessl, 1999. Practical Aspects of Self-Tuning Controllers: Algorithms and Implementation. VUTIUM Press, Brno University of Technology, Brno(in Czech),. Cuencaa, A., J. Salt, 2012. RST controller design for a non-uniform multi-rate control system. Journal of Process Control, 22: 1865-1877. Chidambaram, M., 2002. Computer Control of Processes. Narosa Publishing House, New Delhi, Danijel Pavkovic, Josko Deur, Martin Jansz, Nedjeljko Peric, 2006. Adaptive control of automotive electronic throttle. Control Engineering Practice, 14: 121-136. Deepak M. Sajnekar, S.B. Deshpande, R.M. Mohril, 2013. Comparison of Pole Placement and Pole Zero Cancellation Method for Tuning PID Controller of a Digital Excitation Control System, International Journal of Scientific and Research Publications, 3(4). Gatzke, E.P., E.S. Meadows, C. Wang and F.J. Doyle, 2000. Model based control of a four tank system. international journal of Computer and control engineering, 24: 1503-1509. Landau, I.D., 1998. The R-S-T digital controller design and applications. International journal of Control Engineering Practice, 6: 155-165. Ioan, D. Landau and Gianluca Zito, 2002. Digital Control Systems, Design, Identification and Implementation. Springer, London. Khanchoul, M. and M. Hilairet, 2011. “Design and comparison of different RST controllers for PMSM control”, in the proceedings of 37th Annual Conference on IEEE Industrial Electronics Society, IECON. Lacroix, S., M. Hilairet and E. Laboure, 2011. Design of a battery-charger controller for electric vehicle based on RST controller. in the proceedigs of Vehicle Power and Propulsion Conference on IEEE (VPPC). Ming Zhou, Fuzhu Han, 2009. Adaptive control for EDM process with a self-tuning regulator. International Journal of Machine Tools & Manufacture, 49: 462-469. Poitiers, F., T. Bouaouiche, M. Machmoum, 2009. Advanced control of a doubly-fed induction generator for wind energy conversion.International journal of Electric Power Systems Research, 79: 1085-1096. Karl Astrom, Bjorn Wittenmark, 1998. Adaptive Control. Pearson Education, Second edition. Reza Nasiri, Ahmad Radan, 2011. Adaptive decoupled control of 4-leg voltage-source inverters for standalone photovoltaic systems: Adjusting transient state response. international journal of Renewable Energy 36,2733e2741. Shi Jingzhuo, Liu Bo, Zhang Yu, 2011. Study on self-tuning pole assignment speed control of an ultrasonic motor. ISA Transactions, 50: 581-587. Yoan D. Landau, Ioan Dore Landau, 1998. Adaptive Control. Springer Verlog.