fractional order pid
TRANSCRIPT
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Journal Title Proceedings Third International Conference on Emerging Trends in Engineering and Technology ICETET 2010 19-21 November 2010 Goa India I
Volume Issue MonthlYear nov 19-21 2010 Pages 422-425
Article Author
Article Title Mehra V Srivastava S Varshney P Fractional-Order PID Controller Design for Speed Control of DC Motor
ISSN OCLC 762162077
Lending String UMC WAU GATAZU
In Process 0521
Special Instructions
NotesAlternate Delivery ILL allowed Print fax or secure electronic only
o Paged to SZ o Paged to HS o Emailed Loc
This article was supplied by
Interlibrary Loan and Document Delivery Services University of Washington Libraries
Box 352900 - Seattle WA 98195-2900
(206) 543-1878 or Toll Free (800) 324-5351 OCLC WAU - DOCLlNE WAUWAS
interlibuwashingtonedu
Odyssey 52112012 1238 PM
PDF Copyright Noticedoc ndash 0709
University Libraries
University of Washington
Interlibrary Loan Box 352900
Seattle WA 98195-2900 interlibuwashingtonedu
(206) 543-1878 (800) 324-5351
NOTICE ON COPYRIGHT
This document is being supplied to you in accordance with United States copyright law (Title 17 US Code) It is intended only for your personal research or instructional use The document may not be copied or emailed to multiple sites Nor may it be posted to a mailing list or on the web without the express written consent of the copyright owner and payment of royalties Infringement of copyright law may subject the violator to civil fine andor criminal prosecution or both
Fractional-Order PID Controller Design for Speed Control of DC Motor
Abstractmdash This paper deals speed control of a DC motor using fractional-order control Fractional calculus provides novel and higher performance extensions for fractional order proportional integral and derivative (FOPID) controller In this paper the parameters of the FOPID controller are optimally learned by using Genetic Algorithm (GA) and the optimization performance target is chosen as the integral of the absolute error (IAE) Simulation results show that the FOPID controller performs better than the integer order PID controller
Keywords-Fractional calculus fractional-order controller genetic algorithm DC motor speed control
I INTRODUCTION DC motor is a power actuator which converts electrical
energy into rotational mechanical energy DC motors are widely used in industry and commercial application such as tape motor disk drive robotic manipulators and in numerous control applications Therefore its control is very important For the control of dc motor traditional controllers such as PI and PID controller have been used widely in literature [1] In this paper DC motor is controlled by a non-conventional control technique known as a fractional-order PID (FOPID) control This technique was developed during the last few decades and it has various practical applications viz flexible spacecraft attitude control Car suspension control temperature control motor control etc This idea of the fractional calculus application to control theory has been described in many other works ([2 4 11]) and its advantages are proved as well
This paper has following sections Sections 2 explains briefly about Fraction calculus and fractional-order controller Section 3 discusses the optimization technique using genetic algorithm Sections 4 and 5 show parameter optimization design process and simulation results Section 6 concludes the paper
II FRACTIONAL- ORDER CONTROLLER Fractional-order control systems are described by
fractional-order differential equations The FOPID controller is the expansion of the conventional PID controller based on fractional calculus FOPID has five parameters which are
responsible for adding more flexibility and robustness to the system
A Fractional calculus and Fractional-order controller Fractional calculus is a generalization of integration and
differentiation to non-integer (fractional) order fundamental
operator rD a t where a and t are the limits and (r ɛ R) is the
order of the operation The two definitions used for the
fractional differintegral rD a t are the Gruumlnwald-Letnikov
(GL) definition and the Riemann-Liouville (RL) definition [8 12] Further it has been mentioned in literature that for a wide class of functions these two definitions are equivalent [12] GL definition
t ah
jr r r ra t hh 0 h 0j 0
rD f(t) limh ( 1) f(t jh) limh f(t)
j
(1)
where [middot] means the integer part and rf(t)th is the
generalized finite difference of order r with step h RL definition
tnr
a t n r n 1a
1 d f( )D f(t) d(n a) dt (t )
(2)
for ((n-1)ltrltn) and Г() is the Eulerrsquos gamma function The Laplace transforms of the GL and RL fractional
derivativeintegral of signal f(t) at t=0 for order r is given by r r r
a tL D f(t) s L f(t) s F(s) (3) Using Laplace transformation
s F(s) I f(t) and ds F(s) f(t)dt
(4)
Then the fractional PID controller is written as P I DC(s) K K s K s 0 (5)
Selection of λ δ gives the classical controllers viz PD controller (λ =0) PI controller (δ =0) and PID controller (λ δ=1)
All the above-mentioned controllers are special case of the fractional PIλDδ controller Some advantages of PIλDδ controller include better control of dynamical systems (they are described by fractional-order mathematical models) and that they are less sensitive to parameter variations of a controlled plant
B Continuous-time Approximation of Fractional Differentiator Integrator Several approximation methods and techniques for
obtaining continuous-time and discrete-time fractional-order models in the form of IIR and FIR filters are developed in [9]
Vishal Mehra Smriti Srivastava and Pragya Varshney Department Of Instrumentation and Control Engg
Netaji Subhas Institute Of Technology New Delhi India 110078 vishalmehransitonlinein ssmritiyahoocom pragyavarediffmailcom
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
In this paper the Oustalouprsquos approximation [8] algorithm is used for simulation purposes This method is based on the approximation of a function
rH(s) s r R r 11
For the frequency range (ωl ωh) nk
k n k
sH(s) Ks
Using the following set of synthesis formulae the approximation for poles zeros and gain are obtained as follows k n 05 05r 2n 1
k l h lk n 05 05r 2n 1
k l h l
r n 2K k kh l k n
(6)
where ωh and ωl are the high and low transitional frequencies
This algorithm is implemented in MATLAB as a Function script lsquoora_focrsquo given in [7]
III GENETIC ALGORITHMS Genetic Algorithm (GA) is a stochastic global search
method that mimics the process of natural evolution The algorithm starts with no knowledge of the correct solution and depends entirely on responses from its environment and evolution operators to arrive at the best solution By starting at several independent points and searching in parallel the algorithm avoids local minima and converges to sub optimal solutions In this way GA has been shown to be capable of locating high performance areas in complex domains without experiencing the difficulties associated with high dimensionality
GA consists of three fundamental operators reproduction crossover and mutation These operators work with a number of artificial creatures called a generation By exchanging information from each individual in a population GA preserves a better individual and yields higher fitness generation such that the performance can be improved Given an optimization problem GA encodes the parameter designed into a finite bit string and then runs iteratively using the three operators in a random way but based on the fitness function evolution It performs the basic tasks of copying strings exchanging portions of string and changing some bits of strings Finally it finds and decodes the solution to the problem from the last pool of mature strings
IV DESIGN OF PID AND FOPID CONTROLLER USING GA FOR SPEED CONTROL OF DC MOTOR
According to control objective for a PID controller three parameters viz KP KI KD have to be approximated and for a FOPID controller five parameters KP KI KD λ and δ need to be approximated
The parameters that are used for the designing the controllers are listed in Table I
TABLE I PARAMETERS FOR DESIGN
1 Population size n 100
2 Crossover probability 065
3 Crossover function Arithmetic Crossover
4 Selection Function Stochastic uniform
5 Creation Function Uniform
6 Generation number 50
TABLE I
Fitness Function in this paper the fitness function minimized is the Integral of Absolute Error (IAE)
0
J e(t)dt (7)
Since it is not practical to integrate up to infinity we choose a value of T such that e (t) for t gt T is negligible
V SIMULATION AND EXPERIMENTAL RESULTS In this section a comparison of integer order PID and
FOPID is done using SIMULINK and by practical experimentation
A MS 15 DC motor module The LJ Technical Systems MS 15 DC motor module is
used for the experiment (Fig1) The angular velocity ω(t) of the motor is controlled by applied voltage Va A constant voltage applied to the DC motor produces a constant torque The motor runs at a constant speed This applied voltage is the plant input The motor speed is measured using a tachogenerator mounted on the same shaft as the motor A tachogenerator generates a voltage proportional to the motor speed The voltage from the tachogenerator is used as the plant output in this experiment The output voltage of tachogenerator is feedback to the plant The transfer function of the system has the following form
dcm0833G (s)
0267s 1 (8)
Figure 1 MS 15 DC motor module
B Real time control amp Hardware-in-loop experiment platform Schematic of the real-time hardware-in-loop
configuration is shown in Fig 2 A Data Acquisition and Control Board (DACB) is used to acquire the data from the plant PCI 1710 HG is used to provide feedback to the digital controller (computer) from the plant in the appropriate format
423423423
SIMULINK MATLAB Real-time windows target
ADVANTECH PCI 1710 HG
DAQ Card
DA Converter AD Converter
Plant HW loop
Figure 2 Schematic of the real-time hardware-in-loop experiment
platform
The Advantech PCI 1710 HG board has 8 analog inputs 2 analog outputs and 96 digital IO lines This is interfaced with computer and is realized in SIMULINK using the Real-time windows target tool of MATLAB The design consists of SIMULINK blocks Analog Input Analog Output and Digital InputOutput block Signals from the plant are given to the feedback using Analog input block and the control signal generated by the controller is inputted to the plant using Analog output block
Next the integer order PI PID and FOPID controllers are designed using GA for feedback control of MS 15 DC motor (i) For integer order PI with the following limits
P IK 010 K 030 By running GA for 50 generations the following results
were obtained P IK 00875 K 299820 Best value
IAE 1302 (Fig 3)
0 10 20 30 40 500
10
20
30
40
50
60
Generation
Fitn
ess
valu
e
Best 1302 Mean 13101
Best f itnessMean fitness
Figure 3 Fitness value Vs Generations for PI tuning
(ii) For integer order PID with the following limits P I DK 010 K 030 K 001
By running GA for 50 generations the following results were obtained
P I DK 79447 K 298703K 00498 Best value IAE 77082(Fig 4) (iii) For FO PID with the following limits
P I DK 010 K 030 K 001 01 and = 01 By running GA for 50 generations the following results
were obtained P I DK 57017 K 203722K 00487
09898 and =08324
And the best value of IAE is 10552 (Fig 5)
C Comparison in Simulation Fig1 shows the SIMULINK model for the feedback
control of DC motor where fractional-order controller is realized via lsquoNIPIDrsquo block proposed by D Valerio [9]
0 10 20 30 40 500
20
40
60
80
100
120
140
Generation
Fitn
ess
valu
e
Best 77082 Mean 78184
Best f itnessMean fitness
Figure 4 Fitness value Vs Generations for PID tuning
0 10 20 30 40 500
10
20
30
40
50
60
70
Generation
Fitn
ess
valu
e
Best 10552 Mean 12389
Best f itnessMean fitness
Figure 5 Fitness value Vs Generations for FOPID tuning
Figure 6 SIMULINK model feed back control of DC motor
Fig 6 shows the closed loop response of the DC motor for the square wave input with Integer order PI PID and FOPID controller The simulation results obtained from Fig 6 are tabulated in Table II
TABLE II SIMULATION RESULTS OF SIMULINK BASED SPEED CONTROL OF DC MOTOR
Parameters Integer order PI controlled process
Integer order PID controlled process
FOPID controlled process
Maximum overshot
50 9 4
Rise time 021s 0175s 02065s Settling time approx 15 s 053 s approx 03s Steady state error
0002 0003 0001
The closed loop response of the system for the different
types of control schemes is shown in Fig 7
D Experimental Verification in real time In any control system the final step in the design process
is the real time control experiment As can be observed from Figs 8-10 the performances of the controllers are in confirmation with the simulation results based on the identified model
424424424
0 2 4 6 8 10
0
05
1
15
2
25
3
35
TIME
OP
Refrence signalUncontrolled systemPI controllerPID controllerFOPID controller
Figure 7 Close loop response of system
0 5 10 150
05
1
15
2
25
3
35
4
TIME
Volta
ge
Real time closed loop response of PI controller
data1
data2
Refrence signal
OP signal
Figure 8 Real time closed loop response of PI controller
VI CONCLUSION In this paper a scheme for feedback speed control of DC
motor using a fractional-order PID controller using GA is presented The parameters of integer order PIPID and FOPID are optimally searched by genetic algorithm The results of both controllers are compared in simulation and verified in real time It is observed that the FOPID controller reduces the maximum over shoot settling time and steady state error as compared to the integer order PID controller and provides more robustness in parameter variation than conventional PID due to two extra degree of freedom
REFERENCES [1] I Griffin ldquoOn-line PID Controller Tuning using Genetic Algorithms
rdquo Masterrsquos Thesis DCU August 22 2003 [2] I Podlubny ldquoFractional-order systems and PIλDδ controllersrdquo IEEE
Trans On Automatic Control vol44 no 1 pp 208-213 1999 [3] I Petras L Dorcak and I Kostial ldquocontrol quality enhancement by
fractional order controllers rsquorsquoActa Montanistica Slovaca KosiceVol 3 No 2PP143-1481998
[4] I Petras ldquoThe fractional order controllers methods for their synthesis and application rsquorsquoJ Electrical Engineering Vol 50 No910 pp284-2881999
[5] Y Q Chen and K L Moore ldquoDiscretization Schemes for fractional-order differentiators and integratorsrdquo IEEE Trans On Circuits and Systems vol49 no 3 pp363-367 March 2002
[6] J Y Cao and BG Cao ldquoOptimization of fractional order controllers based on genetic algorithm rdquo Proceedings of the fourth International conference onmachine learning and cyber netics Guanghou18-21 august 2005
[7] Y Q Chen ldquoOustaloup - Recursive Approximation for Fractional Order Differentiators rdquoMath Works Inc August 2003
[8] httpwwwmathworkscommatlabcentralfileexchange3802 [9] Oustaloup A Levron F-Mathieu ldquoFrequency-Band Complex
Noninteger Differentiator Characterization and Synthesisrdquo IEEE Trans on Circuits and Systems I Fundamental Theory and Applications I 47 No 1(2000) 25ndash39
[10] B M Vinagre I Podlubny A Hernrsquoandez A Feliu ldquoSome Approximations of Fractional Order Operators used in Control Theory and Applicationsrdquo Fractional Calculus and Applied Analysis 3 No 3 (2000) 231ndash248
[11] DValerio Toolbox ninteger for Matlab v 23 (September2005) httpwebistutlptduartevalerionintegernintegerhtm [12] D Xue C Zhao Y Q ChenldquoFractional Order PID Control of a DC-
Motor with Elastic Shaft A Case Studyrdquo Procof the 2006 American Control Conference Minneapolis MinnesotaUSA June 14-16 2006 pp 3182ndash3187
[13] I Podlubny ldquoFractional Differential Equationsrdquo Academic Press San Diego 1999
[14] Matlab Genetic Algorithm Tool box
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real Time Closed loop response of PID controller
data1
data2OP signal
Refrence signal
Figure 9 Real time closed loop response of PID controller
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real time closed loop response of FOPID controller
data1
data2
Refrence signal
OP signal
Figure 10 Real time closed loop response of FOPID controller
425425425
PDF Copyright Noticedoc ndash 0709
University Libraries
University of Washington
Interlibrary Loan Box 352900
Seattle WA 98195-2900 interlibuwashingtonedu
(206) 543-1878 (800) 324-5351
NOTICE ON COPYRIGHT
This document is being supplied to you in accordance with United States copyright law (Title 17 US Code) It is intended only for your personal research or instructional use The document may not be copied or emailed to multiple sites Nor may it be posted to a mailing list or on the web without the express written consent of the copyright owner and payment of royalties Infringement of copyright law may subject the violator to civil fine andor criminal prosecution or both
Fractional-Order PID Controller Design for Speed Control of DC Motor
Abstractmdash This paper deals speed control of a DC motor using fractional-order control Fractional calculus provides novel and higher performance extensions for fractional order proportional integral and derivative (FOPID) controller In this paper the parameters of the FOPID controller are optimally learned by using Genetic Algorithm (GA) and the optimization performance target is chosen as the integral of the absolute error (IAE) Simulation results show that the FOPID controller performs better than the integer order PID controller
Keywords-Fractional calculus fractional-order controller genetic algorithm DC motor speed control
I INTRODUCTION DC motor is a power actuator which converts electrical
energy into rotational mechanical energy DC motors are widely used in industry and commercial application such as tape motor disk drive robotic manipulators and in numerous control applications Therefore its control is very important For the control of dc motor traditional controllers such as PI and PID controller have been used widely in literature [1] In this paper DC motor is controlled by a non-conventional control technique known as a fractional-order PID (FOPID) control This technique was developed during the last few decades and it has various practical applications viz flexible spacecraft attitude control Car suspension control temperature control motor control etc This idea of the fractional calculus application to control theory has been described in many other works ([2 4 11]) and its advantages are proved as well
This paper has following sections Sections 2 explains briefly about Fraction calculus and fractional-order controller Section 3 discusses the optimization technique using genetic algorithm Sections 4 and 5 show parameter optimization design process and simulation results Section 6 concludes the paper
II FRACTIONAL- ORDER CONTROLLER Fractional-order control systems are described by
fractional-order differential equations The FOPID controller is the expansion of the conventional PID controller based on fractional calculus FOPID has five parameters which are
responsible for adding more flexibility and robustness to the system
A Fractional calculus and Fractional-order controller Fractional calculus is a generalization of integration and
differentiation to non-integer (fractional) order fundamental
operator rD a t where a and t are the limits and (r ɛ R) is the
order of the operation The two definitions used for the
fractional differintegral rD a t are the Gruumlnwald-Letnikov
(GL) definition and the Riemann-Liouville (RL) definition [8 12] Further it has been mentioned in literature that for a wide class of functions these two definitions are equivalent [12] GL definition
t ah
jr r r ra t hh 0 h 0j 0
rD f(t) limh ( 1) f(t jh) limh f(t)
j
(1)
where [middot] means the integer part and rf(t)th is the
generalized finite difference of order r with step h RL definition
tnr
a t n r n 1a
1 d f( )D f(t) d(n a) dt (t )
(2)
for ((n-1)ltrltn) and Г() is the Eulerrsquos gamma function The Laplace transforms of the GL and RL fractional
derivativeintegral of signal f(t) at t=0 for order r is given by r r r
a tL D f(t) s L f(t) s F(s) (3) Using Laplace transformation
s F(s) I f(t) and ds F(s) f(t)dt
(4)
Then the fractional PID controller is written as P I DC(s) K K s K s 0 (5)
Selection of λ δ gives the classical controllers viz PD controller (λ =0) PI controller (δ =0) and PID controller (λ δ=1)
All the above-mentioned controllers are special case of the fractional PIλDδ controller Some advantages of PIλDδ controller include better control of dynamical systems (they are described by fractional-order mathematical models) and that they are less sensitive to parameter variations of a controlled plant
B Continuous-time Approximation of Fractional Differentiator Integrator Several approximation methods and techniques for
obtaining continuous-time and discrete-time fractional-order models in the form of IIR and FIR filters are developed in [9]
Vishal Mehra Smriti Srivastava and Pragya Varshney Department Of Instrumentation and Control Engg
Netaji Subhas Institute Of Technology New Delhi India 110078 vishalmehransitonlinein ssmritiyahoocom pragyavarediffmailcom
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
In this paper the Oustalouprsquos approximation [8] algorithm is used for simulation purposes This method is based on the approximation of a function
rH(s) s r R r 11
For the frequency range (ωl ωh) nk
k n k
sH(s) Ks
Using the following set of synthesis formulae the approximation for poles zeros and gain are obtained as follows k n 05 05r 2n 1
k l h lk n 05 05r 2n 1
k l h l
r n 2K k kh l k n
(6)
where ωh and ωl are the high and low transitional frequencies
This algorithm is implemented in MATLAB as a Function script lsquoora_focrsquo given in [7]
III GENETIC ALGORITHMS Genetic Algorithm (GA) is a stochastic global search
method that mimics the process of natural evolution The algorithm starts with no knowledge of the correct solution and depends entirely on responses from its environment and evolution operators to arrive at the best solution By starting at several independent points and searching in parallel the algorithm avoids local minima and converges to sub optimal solutions In this way GA has been shown to be capable of locating high performance areas in complex domains without experiencing the difficulties associated with high dimensionality
GA consists of three fundamental operators reproduction crossover and mutation These operators work with a number of artificial creatures called a generation By exchanging information from each individual in a population GA preserves a better individual and yields higher fitness generation such that the performance can be improved Given an optimization problem GA encodes the parameter designed into a finite bit string and then runs iteratively using the three operators in a random way but based on the fitness function evolution It performs the basic tasks of copying strings exchanging portions of string and changing some bits of strings Finally it finds and decodes the solution to the problem from the last pool of mature strings
IV DESIGN OF PID AND FOPID CONTROLLER USING GA FOR SPEED CONTROL OF DC MOTOR
According to control objective for a PID controller three parameters viz KP KI KD have to be approximated and for a FOPID controller five parameters KP KI KD λ and δ need to be approximated
The parameters that are used for the designing the controllers are listed in Table I
TABLE I PARAMETERS FOR DESIGN
1 Population size n 100
2 Crossover probability 065
3 Crossover function Arithmetic Crossover
4 Selection Function Stochastic uniform
5 Creation Function Uniform
6 Generation number 50
TABLE I
Fitness Function in this paper the fitness function minimized is the Integral of Absolute Error (IAE)
0
J e(t)dt (7)
Since it is not practical to integrate up to infinity we choose a value of T such that e (t) for t gt T is negligible
V SIMULATION AND EXPERIMENTAL RESULTS In this section a comparison of integer order PID and
FOPID is done using SIMULINK and by practical experimentation
A MS 15 DC motor module The LJ Technical Systems MS 15 DC motor module is
used for the experiment (Fig1) The angular velocity ω(t) of the motor is controlled by applied voltage Va A constant voltage applied to the DC motor produces a constant torque The motor runs at a constant speed This applied voltage is the plant input The motor speed is measured using a tachogenerator mounted on the same shaft as the motor A tachogenerator generates a voltage proportional to the motor speed The voltage from the tachogenerator is used as the plant output in this experiment The output voltage of tachogenerator is feedback to the plant The transfer function of the system has the following form
dcm0833G (s)
0267s 1 (8)
Figure 1 MS 15 DC motor module
B Real time control amp Hardware-in-loop experiment platform Schematic of the real-time hardware-in-loop
configuration is shown in Fig 2 A Data Acquisition and Control Board (DACB) is used to acquire the data from the plant PCI 1710 HG is used to provide feedback to the digital controller (computer) from the plant in the appropriate format
423423423
SIMULINK MATLAB Real-time windows target
ADVANTECH PCI 1710 HG
DAQ Card
DA Converter AD Converter
Plant HW loop
Figure 2 Schematic of the real-time hardware-in-loop experiment
platform
The Advantech PCI 1710 HG board has 8 analog inputs 2 analog outputs and 96 digital IO lines This is interfaced with computer and is realized in SIMULINK using the Real-time windows target tool of MATLAB The design consists of SIMULINK blocks Analog Input Analog Output and Digital InputOutput block Signals from the plant are given to the feedback using Analog input block and the control signal generated by the controller is inputted to the plant using Analog output block
Next the integer order PI PID and FOPID controllers are designed using GA for feedback control of MS 15 DC motor (i) For integer order PI with the following limits
P IK 010 K 030 By running GA for 50 generations the following results
were obtained P IK 00875 K 299820 Best value
IAE 1302 (Fig 3)
0 10 20 30 40 500
10
20
30
40
50
60
Generation
Fitn
ess
valu
e
Best 1302 Mean 13101
Best f itnessMean fitness
Figure 3 Fitness value Vs Generations for PI tuning
(ii) For integer order PID with the following limits P I DK 010 K 030 K 001
By running GA for 50 generations the following results were obtained
P I DK 79447 K 298703K 00498 Best value IAE 77082(Fig 4) (iii) For FO PID with the following limits
P I DK 010 K 030 K 001 01 and = 01 By running GA for 50 generations the following results
were obtained P I DK 57017 K 203722K 00487
09898 and =08324
And the best value of IAE is 10552 (Fig 5)
C Comparison in Simulation Fig1 shows the SIMULINK model for the feedback
control of DC motor where fractional-order controller is realized via lsquoNIPIDrsquo block proposed by D Valerio [9]
0 10 20 30 40 500
20
40
60
80
100
120
140
Generation
Fitn
ess
valu
e
Best 77082 Mean 78184
Best f itnessMean fitness
Figure 4 Fitness value Vs Generations for PID tuning
0 10 20 30 40 500
10
20
30
40
50
60
70
Generation
Fitn
ess
valu
e
Best 10552 Mean 12389
Best f itnessMean fitness
Figure 5 Fitness value Vs Generations for FOPID tuning
Figure 6 SIMULINK model feed back control of DC motor
Fig 6 shows the closed loop response of the DC motor for the square wave input with Integer order PI PID and FOPID controller The simulation results obtained from Fig 6 are tabulated in Table II
TABLE II SIMULATION RESULTS OF SIMULINK BASED SPEED CONTROL OF DC MOTOR
Parameters Integer order PI controlled process
Integer order PID controlled process
FOPID controlled process
Maximum overshot
50 9 4
Rise time 021s 0175s 02065s Settling time approx 15 s 053 s approx 03s Steady state error
0002 0003 0001
The closed loop response of the system for the different
types of control schemes is shown in Fig 7
D Experimental Verification in real time In any control system the final step in the design process
is the real time control experiment As can be observed from Figs 8-10 the performances of the controllers are in confirmation with the simulation results based on the identified model
424424424
0 2 4 6 8 10
0
05
1
15
2
25
3
35
TIME
OP
Refrence signalUncontrolled systemPI controllerPID controllerFOPID controller
Figure 7 Close loop response of system
0 5 10 150
05
1
15
2
25
3
35
4
TIME
Volta
ge
Real time closed loop response of PI controller
data1
data2
Refrence signal
OP signal
Figure 8 Real time closed loop response of PI controller
VI CONCLUSION In this paper a scheme for feedback speed control of DC
motor using a fractional-order PID controller using GA is presented The parameters of integer order PIPID and FOPID are optimally searched by genetic algorithm The results of both controllers are compared in simulation and verified in real time It is observed that the FOPID controller reduces the maximum over shoot settling time and steady state error as compared to the integer order PID controller and provides more robustness in parameter variation than conventional PID due to two extra degree of freedom
REFERENCES [1] I Griffin ldquoOn-line PID Controller Tuning using Genetic Algorithms
rdquo Masterrsquos Thesis DCU August 22 2003 [2] I Podlubny ldquoFractional-order systems and PIλDδ controllersrdquo IEEE
Trans On Automatic Control vol44 no 1 pp 208-213 1999 [3] I Petras L Dorcak and I Kostial ldquocontrol quality enhancement by
fractional order controllers rsquorsquoActa Montanistica Slovaca KosiceVol 3 No 2PP143-1481998
[4] I Petras ldquoThe fractional order controllers methods for their synthesis and application rsquorsquoJ Electrical Engineering Vol 50 No910 pp284-2881999
[5] Y Q Chen and K L Moore ldquoDiscretization Schemes for fractional-order differentiators and integratorsrdquo IEEE Trans On Circuits and Systems vol49 no 3 pp363-367 March 2002
[6] J Y Cao and BG Cao ldquoOptimization of fractional order controllers based on genetic algorithm rdquo Proceedings of the fourth International conference onmachine learning and cyber netics Guanghou18-21 august 2005
[7] Y Q Chen ldquoOustaloup - Recursive Approximation for Fractional Order Differentiators rdquoMath Works Inc August 2003
[8] httpwwwmathworkscommatlabcentralfileexchange3802 [9] Oustaloup A Levron F-Mathieu ldquoFrequency-Band Complex
Noninteger Differentiator Characterization and Synthesisrdquo IEEE Trans on Circuits and Systems I Fundamental Theory and Applications I 47 No 1(2000) 25ndash39
[10] B M Vinagre I Podlubny A Hernrsquoandez A Feliu ldquoSome Approximations of Fractional Order Operators used in Control Theory and Applicationsrdquo Fractional Calculus and Applied Analysis 3 No 3 (2000) 231ndash248
[11] DValerio Toolbox ninteger for Matlab v 23 (September2005) httpwebistutlptduartevalerionintegernintegerhtm [12] D Xue C Zhao Y Q ChenldquoFractional Order PID Control of a DC-
Motor with Elastic Shaft A Case Studyrdquo Procof the 2006 American Control Conference Minneapolis MinnesotaUSA June 14-16 2006 pp 3182ndash3187
[13] I Podlubny ldquoFractional Differential Equationsrdquo Academic Press San Diego 1999
[14] Matlab Genetic Algorithm Tool box
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real Time Closed loop response of PID controller
data1
data2OP signal
Refrence signal
Figure 9 Real time closed loop response of PID controller
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real time closed loop response of FOPID controller
data1
data2
Refrence signal
OP signal
Figure 10 Real time closed loop response of FOPID controller
425425425
Fractional-Order PID Controller Design for Speed Control of DC Motor
Abstractmdash This paper deals speed control of a DC motor using fractional-order control Fractional calculus provides novel and higher performance extensions for fractional order proportional integral and derivative (FOPID) controller In this paper the parameters of the FOPID controller are optimally learned by using Genetic Algorithm (GA) and the optimization performance target is chosen as the integral of the absolute error (IAE) Simulation results show that the FOPID controller performs better than the integer order PID controller
Keywords-Fractional calculus fractional-order controller genetic algorithm DC motor speed control
I INTRODUCTION DC motor is a power actuator which converts electrical
energy into rotational mechanical energy DC motors are widely used in industry and commercial application such as tape motor disk drive robotic manipulators and in numerous control applications Therefore its control is very important For the control of dc motor traditional controllers such as PI and PID controller have been used widely in literature [1] In this paper DC motor is controlled by a non-conventional control technique known as a fractional-order PID (FOPID) control This technique was developed during the last few decades and it has various practical applications viz flexible spacecraft attitude control Car suspension control temperature control motor control etc This idea of the fractional calculus application to control theory has been described in many other works ([2 4 11]) and its advantages are proved as well
This paper has following sections Sections 2 explains briefly about Fraction calculus and fractional-order controller Section 3 discusses the optimization technique using genetic algorithm Sections 4 and 5 show parameter optimization design process and simulation results Section 6 concludes the paper
II FRACTIONAL- ORDER CONTROLLER Fractional-order control systems are described by
fractional-order differential equations The FOPID controller is the expansion of the conventional PID controller based on fractional calculus FOPID has five parameters which are
responsible for adding more flexibility and robustness to the system
A Fractional calculus and Fractional-order controller Fractional calculus is a generalization of integration and
differentiation to non-integer (fractional) order fundamental
operator rD a t where a and t are the limits and (r ɛ R) is the
order of the operation The two definitions used for the
fractional differintegral rD a t are the Gruumlnwald-Letnikov
(GL) definition and the Riemann-Liouville (RL) definition [8 12] Further it has been mentioned in literature that for a wide class of functions these two definitions are equivalent [12] GL definition
t ah
jr r r ra t hh 0 h 0j 0
rD f(t) limh ( 1) f(t jh) limh f(t)
j
(1)
where [middot] means the integer part and rf(t)th is the
generalized finite difference of order r with step h RL definition
tnr
a t n r n 1a
1 d f( )D f(t) d(n a) dt (t )
(2)
for ((n-1)ltrltn) and Г() is the Eulerrsquos gamma function The Laplace transforms of the GL and RL fractional
derivativeintegral of signal f(t) at t=0 for order r is given by r r r
a tL D f(t) s L f(t) s F(s) (3) Using Laplace transformation
s F(s) I f(t) and ds F(s) f(t)dt
(4)
Then the fractional PID controller is written as P I DC(s) K K s K s 0 (5)
Selection of λ δ gives the classical controllers viz PD controller (λ =0) PI controller (δ =0) and PID controller (λ δ=1)
All the above-mentioned controllers are special case of the fractional PIλDδ controller Some advantages of PIλDδ controller include better control of dynamical systems (they are described by fractional-order mathematical models) and that they are less sensitive to parameter variations of a controlled plant
B Continuous-time Approximation of Fractional Differentiator Integrator Several approximation methods and techniques for
obtaining continuous-time and discrete-time fractional-order models in the form of IIR and FIR filters are developed in [9]
Vishal Mehra Smriti Srivastava and Pragya Varshney Department Of Instrumentation and Control Engg
Netaji Subhas Institute Of Technology New Delhi India 110078 vishalmehransitonlinein ssmritiyahoocom pragyavarediffmailcom
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
Third International Conference on Emerging Trends in Engineering and Technology
978-0-7695-4246-110 $2600 copy 2010 IEEE
DOI 101109ICETET2010123
422
In this paper the Oustalouprsquos approximation [8] algorithm is used for simulation purposes This method is based on the approximation of a function
rH(s) s r R r 11
For the frequency range (ωl ωh) nk
k n k
sH(s) Ks
Using the following set of synthesis formulae the approximation for poles zeros and gain are obtained as follows k n 05 05r 2n 1
k l h lk n 05 05r 2n 1
k l h l
r n 2K k kh l k n
(6)
where ωh and ωl are the high and low transitional frequencies
This algorithm is implemented in MATLAB as a Function script lsquoora_focrsquo given in [7]
III GENETIC ALGORITHMS Genetic Algorithm (GA) is a stochastic global search
method that mimics the process of natural evolution The algorithm starts with no knowledge of the correct solution and depends entirely on responses from its environment and evolution operators to arrive at the best solution By starting at several independent points and searching in parallel the algorithm avoids local minima and converges to sub optimal solutions In this way GA has been shown to be capable of locating high performance areas in complex domains without experiencing the difficulties associated with high dimensionality
GA consists of three fundamental operators reproduction crossover and mutation These operators work with a number of artificial creatures called a generation By exchanging information from each individual in a population GA preserves a better individual and yields higher fitness generation such that the performance can be improved Given an optimization problem GA encodes the parameter designed into a finite bit string and then runs iteratively using the three operators in a random way but based on the fitness function evolution It performs the basic tasks of copying strings exchanging portions of string and changing some bits of strings Finally it finds and decodes the solution to the problem from the last pool of mature strings
IV DESIGN OF PID AND FOPID CONTROLLER USING GA FOR SPEED CONTROL OF DC MOTOR
According to control objective for a PID controller three parameters viz KP KI KD have to be approximated and for a FOPID controller five parameters KP KI KD λ and δ need to be approximated
The parameters that are used for the designing the controllers are listed in Table I
TABLE I PARAMETERS FOR DESIGN
1 Population size n 100
2 Crossover probability 065
3 Crossover function Arithmetic Crossover
4 Selection Function Stochastic uniform
5 Creation Function Uniform
6 Generation number 50
TABLE I
Fitness Function in this paper the fitness function minimized is the Integral of Absolute Error (IAE)
0
J e(t)dt (7)
Since it is not practical to integrate up to infinity we choose a value of T such that e (t) for t gt T is negligible
V SIMULATION AND EXPERIMENTAL RESULTS In this section a comparison of integer order PID and
FOPID is done using SIMULINK and by practical experimentation
A MS 15 DC motor module The LJ Technical Systems MS 15 DC motor module is
used for the experiment (Fig1) The angular velocity ω(t) of the motor is controlled by applied voltage Va A constant voltage applied to the DC motor produces a constant torque The motor runs at a constant speed This applied voltage is the plant input The motor speed is measured using a tachogenerator mounted on the same shaft as the motor A tachogenerator generates a voltage proportional to the motor speed The voltage from the tachogenerator is used as the plant output in this experiment The output voltage of tachogenerator is feedback to the plant The transfer function of the system has the following form
dcm0833G (s)
0267s 1 (8)
Figure 1 MS 15 DC motor module
B Real time control amp Hardware-in-loop experiment platform Schematic of the real-time hardware-in-loop
configuration is shown in Fig 2 A Data Acquisition and Control Board (DACB) is used to acquire the data from the plant PCI 1710 HG is used to provide feedback to the digital controller (computer) from the plant in the appropriate format
423423423
SIMULINK MATLAB Real-time windows target
ADVANTECH PCI 1710 HG
DAQ Card
DA Converter AD Converter
Plant HW loop
Figure 2 Schematic of the real-time hardware-in-loop experiment
platform
The Advantech PCI 1710 HG board has 8 analog inputs 2 analog outputs and 96 digital IO lines This is interfaced with computer and is realized in SIMULINK using the Real-time windows target tool of MATLAB The design consists of SIMULINK blocks Analog Input Analog Output and Digital InputOutput block Signals from the plant are given to the feedback using Analog input block and the control signal generated by the controller is inputted to the plant using Analog output block
Next the integer order PI PID and FOPID controllers are designed using GA for feedback control of MS 15 DC motor (i) For integer order PI with the following limits
P IK 010 K 030 By running GA for 50 generations the following results
were obtained P IK 00875 K 299820 Best value
IAE 1302 (Fig 3)
0 10 20 30 40 500
10
20
30
40
50
60
Generation
Fitn
ess
valu
e
Best 1302 Mean 13101
Best f itnessMean fitness
Figure 3 Fitness value Vs Generations for PI tuning
(ii) For integer order PID with the following limits P I DK 010 K 030 K 001
By running GA for 50 generations the following results were obtained
P I DK 79447 K 298703K 00498 Best value IAE 77082(Fig 4) (iii) For FO PID with the following limits
P I DK 010 K 030 K 001 01 and = 01 By running GA for 50 generations the following results
were obtained P I DK 57017 K 203722K 00487
09898 and =08324
And the best value of IAE is 10552 (Fig 5)
C Comparison in Simulation Fig1 shows the SIMULINK model for the feedback
control of DC motor where fractional-order controller is realized via lsquoNIPIDrsquo block proposed by D Valerio [9]
0 10 20 30 40 500
20
40
60
80
100
120
140
Generation
Fitn
ess
valu
e
Best 77082 Mean 78184
Best f itnessMean fitness
Figure 4 Fitness value Vs Generations for PID tuning
0 10 20 30 40 500
10
20
30
40
50
60
70
Generation
Fitn
ess
valu
e
Best 10552 Mean 12389
Best f itnessMean fitness
Figure 5 Fitness value Vs Generations for FOPID tuning
Figure 6 SIMULINK model feed back control of DC motor
Fig 6 shows the closed loop response of the DC motor for the square wave input with Integer order PI PID and FOPID controller The simulation results obtained from Fig 6 are tabulated in Table II
TABLE II SIMULATION RESULTS OF SIMULINK BASED SPEED CONTROL OF DC MOTOR
Parameters Integer order PI controlled process
Integer order PID controlled process
FOPID controlled process
Maximum overshot
50 9 4
Rise time 021s 0175s 02065s Settling time approx 15 s 053 s approx 03s Steady state error
0002 0003 0001
The closed loop response of the system for the different
types of control schemes is shown in Fig 7
D Experimental Verification in real time In any control system the final step in the design process
is the real time control experiment As can be observed from Figs 8-10 the performances of the controllers are in confirmation with the simulation results based on the identified model
424424424
0 2 4 6 8 10
0
05
1
15
2
25
3
35
TIME
OP
Refrence signalUncontrolled systemPI controllerPID controllerFOPID controller
Figure 7 Close loop response of system
0 5 10 150
05
1
15
2
25
3
35
4
TIME
Volta
ge
Real time closed loop response of PI controller
data1
data2
Refrence signal
OP signal
Figure 8 Real time closed loop response of PI controller
VI CONCLUSION In this paper a scheme for feedback speed control of DC
motor using a fractional-order PID controller using GA is presented The parameters of integer order PIPID and FOPID are optimally searched by genetic algorithm The results of both controllers are compared in simulation and verified in real time It is observed that the FOPID controller reduces the maximum over shoot settling time and steady state error as compared to the integer order PID controller and provides more robustness in parameter variation than conventional PID due to two extra degree of freedom
REFERENCES [1] I Griffin ldquoOn-line PID Controller Tuning using Genetic Algorithms
rdquo Masterrsquos Thesis DCU August 22 2003 [2] I Podlubny ldquoFractional-order systems and PIλDδ controllersrdquo IEEE
Trans On Automatic Control vol44 no 1 pp 208-213 1999 [3] I Petras L Dorcak and I Kostial ldquocontrol quality enhancement by
fractional order controllers rsquorsquoActa Montanistica Slovaca KosiceVol 3 No 2PP143-1481998
[4] I Petras ldquoThe fractional order controllers methods for their synthesis and application rsquorsquoJ Electrical Engineering Vol 50 No910 pp284-2881999
[5] Y Q Chen and K L Moore ldquoDiscretization Schemes for fractional-order differentiators and integratorsrdquo IEEE Trans On Circuits and Systems vol49 no 3 pp363-367 March 2002
[6] J Y Cao and BG Cao ldquoOptimization of fractional order controllers based on genetic algorithm rdquo Proceedings of the fourth International conference onmachine learning and cyber netics Guanghou18-21 august 2005
[7] Y Q Chen ldquoOustaloup - Recursive Approximation for Fractional Order Differentiators rdquoMath Works Inc August 2003
[8] httpwwwmathworkscommatlabcentralfileexchange3802 [9] Oustaloup A Levron F-Mathieu ldquoFrequency-Band Complex
Noninteger Differentiator Characterization and Synthesisrdquo IEEE Trans on Circuits and Systems I Fundamental Theory and Applications I 47 No 1(2000) 25ndash39
[10] B M Vinagre I Podlubny A Hernrsquoandez A Feliu ldquoSome Approximations of Fractional Order Operators used in Control Theory and Applicationsrdquo Fractional Calculus and Applied Analysis 3 No 3 (2000) 231ndash248
[11] DValerio Toolbox ninteger for Matlab v 23 (September2005) httpwebistutlptduartevalerionintegernintegerhtm [12] D Xue C Zhao Y Q ChenldquoFractional Order PID Control of a DC-
Motor with Elastic Shaft A Case Studyrdquo Procof the 2006 American Control Conference Minneapolis MinnesotaUSA June 14-16 2006 pp 3182ndash3187
[13] I Podlubny ldquoFractional Differential Equationsrdquo Academic Press San Diego 1999
[14] Matlab Genetic Algorithm Tool box
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real Time Closed loop response of PID controller
data1
data2OP signal
Refrence signal
Figure 9 Real time closed loop response of PID controller
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real time closed loop response of FOPID controller
data1
data2
Refrence signal
OP signal
Figure 10 Real time closed loop response of FOPID controller
425425425
In this paper the Oustalouprsquos approximation [8] algorithm is used for simulation purposes This method is based on the approximation of a function
rH(s) s r R r 11
For the frequency range (ωl ωh) nk
k n k
sH(s) Ks
Using the following set of synthesis formulae the approximation for poles zeros and gain are obtained as follows k n 05 05r 2n 1
k l h lk n 05 05r 2n 1
k l h l
r n 2K k kh l k n
(6)
where ωh and ωl are the high and low transitional frequencies
This algorithm is implemented in MATLAB as a Function script lsquoora_focrsquo given in [7]
III GENETIC ALGORITHMS Genetic Algorithm (GA) is a stochastic global search
method that mimics the process of natural evolution The algorithm starts with no knowledge of the correct solution and depends entirely on responses from its environment and evolution operators to arrive at the best solution By starting at several independent points and searching in parallel the algorithm avoids local minima and converges to sub optimal solutions In this way GA has been shown to be capable of locating high performance areas in complex domains without experiencing the difficulties associated with high dimensionality
GA consists of three fundamental operators reproduction crossover and mutation These operators work with a number of artificial creatures called a generation By exchanging information from each individual in a population GA preserves a better individual and yields higher fitness generation such that the performance can be improved Given an optimization problem GA encodes the parameter designed into a finite bit string and then runs iteratively using the three operators in a random way but based on the fitness function evolution It performs the basic tasks of copying strings exchanging portions of string and changing some bits of strings Finally it finds and decodes the solution to the problem from the last pool of mature strings
IV DESIGN OF PID AND FOPID CONTROLLER USING GA FOR SPEED CONTROL OF DC MOTOR
According to control objective for a PID controller three parameters viz KP KI KD have to be approximated and for a FOPID controller five parameters KP KI KD λ and δ need to be approximated
The parameters that are used for the designing the controllers are listed in Table I
TABLE I PARAMETERS FOR DESIGN
1 Population size n 100
2 Crossover probability 065
3 Crossover function Arithmetic Crossover
4 Selection Function Stochastic uniform
5 Creation Function Uniform
6 Generation number 50
TABLE I
Fitness Function in this paper the fitness function minimized is the Integral of Absolute Error (IAE)
0
J e(t)dt (7)
Since it is not practical to integrate up to infinity we choose a value of T such that e (t) for t gt T is negligible
V SIMULATION AND EXPERIMENTAL RESULTS In this section a comparison of integer order PID and
FOPID is done using SIMULINK and by practical experimentation
A MS 15 DC motor module The LJ Technical Systems MS 15 DC motor module is
used for the experiment (Fig1) The angular velocity ω(t) of the motor is controlled by applied voltage Va A constant voltage applied to the DC motor produces a constant torque The motor runs at a constant speed This applied voltage is the plant input The motor speed is measured using a tachogenerator mounted on the same shaft as the motor A tachogenerator generates a voltage proportional to the motor speed The voltage from the tachogenerator is used as the plant output in this experiment The output voltage of tachogenerator is feedback to the plant The transfer function of the system has the following form
dcm0833G (s)
0267s 1 (8)
Figure 1 MS 15 DC motor module
B Real time control amp Hardware-in-loop experiment platform Schematic of the real-time hardware-in-loop
configuration is shown in Fig 2 A Data Acquisition and Control Board (DACB) is used to acquire the data from the plant PCI 1710 HG is used to provide feedback to the digital controller (computer) from the plant in the appropriate format
423423423
SIMULINK MATLAB Real-time windows target
ADVANTECH PCI 1710 HG
DAQ Card
DA Converter AD Converter
Plant HW loop
Figure 2 Schematic of the real-time hardware-in-loop experiment
platform
The Advantech PCI 1710 HG board has 8 analog inputs 2 analog outputs and 96 digital IO lines This is interfaced with computer and is realized in SIMULINK using the Real-time windows target tool of MATLAB The design consists of SIMULINK blocks Analog Input Analog Output and Digital InputOutput block Signals from the plant are given to the feedback using Analog input block and the control signal generated by the controller is inputted to the plant using Analog output block
Next the integer order PI PID and FOPID controllers are designed using GA for feedback control of MS 15 DC motor (i) For integer order PI with the following limits
P IK 010 K 030 By running GA for 50 generations the following results
were obtained P IK 00875 K 299820 Best value
IAE 1302 (Fig 3)
0 10 20 30 40 500
10
20
30
40
50
60
Generation
Fitn
ess
valu
e
Best 1302 Mean 13101
Best f itnessMean fitness
Figure 3 Fitness value Vs Generations for PI tuning
(ii) For integer order PID with the following limits P I DK 010 K 030 K 001
By running GA for 50 generations the following results were obtained
P I DK 79447 K 298703K 00498 Best value IAE 77082(Fig 4) (iii) For FO PID with the following limits
P I DK 010 K 030 K 001 01 and = 01 By running GA for 50 generations the following results
were obtained P I DK 57017 K 203722K 00487
09898 and =08324
And the best value of IAE is 10552 (Fig 5)
C Comparison in Simulation Fig1 shows the SIMULINK model for the feedback
control of DC motor where fractional-order controller is realized via lsquoNIPIDrsquo block proposed by D Valerio [9]
0 10 20 30 40 500
20
40
60
80
100
120
140
Generation
Fitn
ess
valu
e
Best 77082 Mean 78184
Best f itnessMean fitness
Figure 4 Fitness value Vs Generations for PID tuning
0 10 20 30 40 500
10
20
30
40
50
60
70
Generation
Fitn
ess
valu
e
Best 10552 Mean 12389
Best f itnessMean fitness
Figure 5 Fitness value Vs Generations for FOPID tuning
Figure 6 SIMULINK model feed back control of DC motor
Fig 6 shows the closed loop response of the DC motor for the square wave input with Integer order PI PID and FOPID controller The simulation results obtained from Fig 6 are tabulated in Table II
TABLE II SIMULATION RESULTS OF SIMULINK BASED SPEED CONTROL OF DC MOTOR
Parameters Integer order PI controlled process
Integer order PID controlled process
FOPID controlled process
Maximum overshot
50 9 4
Rise time 021s 0175s 02065s Settling time approx 15 s 053 s approx 03s Steady state error
0002 0003 0001
The closed loop response of the system for the different
types of control schemes is shown in Fig 7
D Experimental Verification in real time In any control system the final step in the design process
is the real time control experiment As can be observed from Figs 8-10 the performances of the controllers are in confirmation with the simulation results based on the identified model
424424424
0 2 4 6 8 10
0
05
1
15
2
25
3
35
TIME
OP
Refrence signalUncontrolled systemPI controllerPID controllerFOPID controller
Figure 7 Close loop response of system
0 5 10 150
05
1
15
2
25
3
35
4
TIME
Volta
ge
Real time closed loop response of PI controller
data1
data2
Refrence signal
OP signal
Figure 8 Real time closed loop response of PI controller
VI CONCLUSION In this paper a scheme for feedback speed control of DC
motor using a fractional-order PID controller using GA is presented The parameters of integer order PIPID and FOPID are optimally searched by genetic algorithm The results of both controllers are compared in simulation and verified in real time It is observed that the FOPID controller reduces the maximum over shoot settling time and steady state error as compared to the integer order PID controller and provides more robustness in parameter variation than conventional PID due to two extra degree of freedom
REFERENCES [1] I Griffin ldquoOn-line PID Controller Tuning using Genetic Algorithms
rdquo Masterrsquos Thesis DCU August 22 2003 [2] I Podlubny ldquoFractional-order systems and PIλDδ controllersrdquo IEEE
Trans On Automatic Control vol44 no 1 pp 208-213 1999 [3] I Petras L Dorcak and I Kostial ldquocontrol quality enhancement by
fractional order controllers rsquorsquoActa Montanistica Slovaca KosiceVol 3 No 2PP143-1481998
[4] I Petras ldquoThe fractional order controllers methods for their synthesis and application rsquorsquoJ Electrical Engineering Vol 50 No910 pp284-2881999
[5] Y Q Chen and K L Moore ldquoDiscretization Schemes for fractional-order differentiators and integratorsrdquo IEEE Trans On Circuits and Systems vol49 no 3 pp363-367 March 2002
[6] J Y Cao and BG Cao ldquoOptimization of fractional order controllers based on genetic algorithm rdquo Proceedings of the fourth International conference onmachine learning and cyber netics Guanghou18-21 august 2005
[7] Y Q Chen ldquoOustaloup - Recursive Approximation for Fractional Order Differentiators rdquoMath Works Inc August 2003
[8] httpwwwmathworkscommatlabcentralfileexchange3802 [9] Oustaloup A Levron F-Mathieu ldquoFrequency-Band Complex
Noninteger Differentiator Characterization and Synthesisrdquo IEEE Trans on Circuits and Systems I Fundamental Theory and Applications I 47 No 1(2000) 25ndash39
[10] B M Vinagre I Podlubny A Hernrsquoandez A Feliu ldquoSome Approximations of Fractional Order Operators used in Control Theory and Applicationsrdquo Fractional Calculus and Applied Analysis 3 No 3 (2000) 231ndash248
[11] DValerio Toolbox ninteger for Matlab v 23 (September2005) httpwebistutlptduartevalerionintegernintegerhtm [12] D Xue C Zhao Y Q ChenldquoFractional Order PID Control of a DC-
Motor with Elastic Shaft A Case Studyrdquo Procof the 2006 American Control Conference Minneapolis MinnesotaUSA June 14-16 2006 pp 3182ndash3187
[13] I Podlubny ldquoFractional Differential Equationsrdquo Academic Press San Diego 1999
[14] Matlab Genetic Algorithm Tool box
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real Time Closed loop response of PID controller
data1
data2OP signal
Refrence signal
Figure 9 Real time closed loop response of PID controller
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real time closed loop response of FOPID controller
data1
data2
Refrence signal
OP signal
Figure 10 Real time closed loop response of FOPID controller
425425425
SIMULINK MATLAB Real-time windows target
ADVANTECH PCI 1710 HG
DAQ Card
DA Converter AD Converter
Plant HW loop
Figure 2 Schematic of the real-time hardware-in-loop experiment
platform
The Advantech PCI 1710 HG board has 8 analog inputs 2 analog outputs and 96 digital IO lines This is interfaced with computer and is realized in SIMULINK using the Real-time windows target tool of MATLAB The design consists of SIMULINK blocks Analog Input Analog Output and Digital InputOutput block Signals from the plant are given to the feedback using Analog input block and the control signal generated by the controller is inputted to the plant using Analog output block
Next the integer order PI PID and FOPID controllers are designed using GA for feedback control of MS 15 DC motor (i) For integer order PI with the following limits
P IK 010 K 030 By running GA for 50 generations the following results
were obtained P IK 00875 K 299820 Best value
IAE 1302 (Fig 3)
0 10 20 30 40 500
10
20
30
40
50
60
Generation
Fitn
ess
valu
e
Best 1302 Mean 13101
Best f itnessMean fitness
Figure 3 Fitness value Vs Generations for PI tuning
(ii) For integer order PID with the following limits P I DK 010 K 030 K 001
By running GA for 50 generations the following results were obtained
P I DK 79447 K 298703K 00498 Best value IAE 77082(Fig 4) (iii) For FO PID with the following limits
P I DK 010 K 030 K 001 01 and = 01 By running GA for 50 generations the following results
were obtained P I DK 57017 K 203722K 00487
09898 and =08324
And the best value of IAE is 10552 (Fig 5)
C Comparison in Simulation Fig1 shows the SIMULINK model for the feedback
control of DC motor where fractional-order controller is realized via lsquoNIPIDrsquo block proposed by D Valerio [9]
0 10 20 30 40 500
20
40
60
80
100
120
140
Generation
Fitn
ess
valu
e
Best 77082 Mean 78184
Best f itnessMean fitness
Figure 4 Fitness value Vs Generations for PID tuning
0 10 20 30 40 500
10
20
30
40
50
60
70
Generation
Fitn
ess
valu
e
Best 10552 Mean 12389
Best f itnessMean fitness
Figure 5 Fitness value Vs Generations for FOPID tuning
Figure 6 SIMULINK model feed back control of DC motor
Fig 6 shows the closed loop response of the DC motor for the square wave input with Integer order PI PID and FOPID controller The simulation results obtained from Fig 6 are tabulated in Table II
TABLE II SIMULATION RESULTS OF SIMULINK BASED SPEED CONTROL OF DC MOTOR
Parameters Integer order PI controlled process
Integer order PID controlled process
FOPID controlled process
Maximum overshot
50 9 4
Rise time 021s 0175s 02065s Settling time approx 15 s 053 s approx 03s Steady state error
0002 0003 0001
The closed loop response of the system for the different
types of control schemes is shown in Fig 7
D Experimental Verification in real time In any control system the final step in the design process
is the real time control experiment As can be observed from Figs 8-10 the performances of the controllers are in confirmation with the simulation results based on the identified model
424424424
0 2 4 6 8 10
0
05
1
15
2
25
3
35
TIME
OP
Refrence signalUncontrolled systemPI controllerPID controllerFOPID controller
Figure 7 Close loop response of system
0 5 10 150
05
1
15
2
25
3
35
4
TIME
Volta
ge
Real time closed loop response of PI controller
data1
data2
Refrence signal
OP signal
Figure 8 Real time closed loop response of PI controller
VI CONCLUSION In this paper a scheme for feedback speed control of DC
motor using a fractional-order PID controller using GA is presented The parameters of integer order PIPID and FOPID are optimally searched by genetic algorithm The results of both controllers are compared in simulation and verified in real time It is observed that the FOPID controller reduces the maximum over shoot settling time and steady state error as compared to the integer order PID controller and provides more robustness in parameter variation than conventional PID due to two extra degree of freedom
REFERENCES [1] I Griffin ldquoOn-line PID Controller Tuning using Genetic Algorithms
rdquo Masterrsquos Thesis DCU August 22 2003 [2] I Podlubny ldquoFractional-order systems and PIλDδ controllersrdquo IEEE
Trans On Automatic Control vol44 no 1 pp 208-213 1999 [3] I Petras L Dorcak and I Kostial ldquocontrol quality enhancement by
fractional order controllers rsquorsquoActa Montanistica Slovaca KosiceVol 3 No 2PP143-1481998
[4] I Petras ldquoThe fractional order controllers methods for their synthesis and application rsquorsquoJ Electrical Engineering Vol 50 No910 pp284-2881999
[5] Y Q Chen and K L Moore ldquoDiscretization Schemes for fractional-order differentiators and integratorsrdquo IEEE Trans On Circuits and Systems vol49 no 3 pp363-367 March 2002
[6] J Y Cao and BG Cao ldquoOptimization of fractional order controllers based on genetic algorithm rdquo Proceedings of the fourth International conference onmachine learning and cyber netics Guanghou18-21 august 2005
[7] Y Q Chen ldquoOustaloup - Recursive Approximation for Fractional Order Differentiators rdquoMath Works Inc August 2003
[8] httpwwwmathworkscommatlabcentralfileexchange3802 [9] Oustaloup A Levron F-Mathieu ldquoFrequency-Band Complex
Noninteger Differentiator Characterization and Synthesisrdquo IEEE Trans on Circuits and Systems I Fundamental Theory and Applications I 47 No 1(2000) 25ndash39
[10] B M Vinagre I Podlubny A Hernrsquoandez A Feliu ldquoSome Approximations of Fractional Order Operators used in Control Theory and Applicationsrdquo Fractional Calculus and Applied Analysis 3 No 3 (2000) 231ndash248
[11] DValerio Toolbox ninteger for Matlab v 23 (September2005) httpwebistutlptduartevalerionintegernintegerhtm [12] D Xue C Zhao Y Q ChenldquoFractional Order PID Control of a DC-
Motor with Elastic Shaft A Case Studyrdquo Procof the 2006 American Control Conference Minneapolis MinnesotaUSA June 14-16 2006 pp 3182ndash3187
[13] I Podlubny ldquoFractional Differential Equationsrdquo Academic Press San Diego 1999
[14] Matlab Genetic Algorithm Tool box
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real Time Closed loop response of PID controller
data1
data2OP signal
Refrence signal
Figure 9 Real time closed loop response of PID controller
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real time closed loop response of FOPID controller
data1
data2
Refrence signal
OP signal
Figure 10 Real time closed loop response of FOPID controller
425425425
0 2 4 6 8 10
0
05
1
15
2
25
3
35
TIME
OP
Refrence signalUncontrolled systemPI controllerPID controllerFOPID controller
Figure 7 Close loop response of system
0 5 10 150
05
1
15
2
25
3
35
4
TIME
Volta
ge
Real time closed loop response of PI controller
data1
data2
Refrence signal
OP signal
Figure 8 Real time closed loop response of PI controller
VI CONCLUSION In this paper a scheme for feedback speed control of DC
motor using a fractional-order PID controller using GA is presented The parameters of integer order PIPID and FOPID are optimally searched by genetic algorithm The results of both controllers are compared in simulation and verified in real time It is observed that the FOPID controller reduces the maximum over shoot settling time and steady state error as compared to the integer order PID controller and provides more robustness in parameter variation than conventional PID due to two extra degree of freedom
REFERENCES [1] I Griffin ldquoOn-line PID Controller Tuning using Genetic Algorithms
rdquo Masterrsquos Thesis DCU August 22 2003 [2] I Podlubny ldquoFractional-order systems and PIλDδ controllersrdquo IEEE
Trans On Automatic Control vol44 no 1 pp 208-213 1999 [3] I Petras L Dorcak and I Kostial ldquocontrol quality enhancement by
fractional order controllers rsquorsquoActa Montanistica Slovaca KosiceVol 3 No 2PP143-1481998
[4] I Petras ldquoThe fractional order controllers methods for their synthesis and application rsquorsquoJ Electrical Engineering Vol 50 No910 pp284-2881999
[5] Y Q Chen and K L Moore ldquoDiscretization Schemes for fractional-order differentiators and integratorsrdquo IEEE Trans On Circuits and Systems vol49 no 3 pp363-367 March 2002
[6] J Y Cao and BG Cao ldquoOptimization of fractional order controllers based on genetic algorithm rdquo Proceedings of the fourth International conference onmachine learning and cyber netics Guanghou18-21 august 2005
[7] Y Q Chen ldquoOustaloup - Recursive Approximation for Fractional Order Differentiators rdquoMath Works Inc August 2003
[8] httpwwwmathworkscommatlabcentralfileexchange3802 [9] Oustaloup A Levron F-Mathieu ldquoFrequency-Band Complex
Noninteger Differentiator Characterization and Synthesisrdquo IEEE Trans on Circuits and Systems I Fundamental Theory and Applications I 47 No 1(2000) 25ndash39
[10] B M Vinagre I Podlubny A Hernrsquoandez A Feliu ldquoSome Approximations of Fractional Order Operators used in Control Theory and Applicationsrdquo Fractional Calculus and Applied Analysis 3 No 3 (2000) 231ndash248
[11] DValerio Toolbox ninteger for Matlab v 23 (September2005) httpwebistutlptduartevalerionintegernintegerhtm [12] D Xue C Zhao Y Q ChenldquoFractional Order PID Control of a DC-
Motor with Elastic Shaft A Case Studyrdquo Procof the 2006 American Control Conference Minneapolis MinnesotaUSA June 14-16 2006 pp 3182ndash3187
[13] I Podlubny ldquoFractional Differential Equationsrdquo Academic Press San Diego 1999
[14] Matlab Genetic Algorithm Tool box
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real Time Closed loop response of PID controller
data1
data2OP signal
Refrence signal
Figure 9 Real time closed loop response of PID controller
0 5 10 150
05
1
15
2
25
3
35
TIME
Volta
ge
Real time closed loop response of FOPID controller
data1
data2
Refrence signal
OP signal
Figure 10 Real time closed loop response of FOPID controller
425425425