Design & Development of Real Time MATLAB-GUI Based Fuzzy Logic Controllers for DC Motor Speed Control System

Transcription

1 International Journal of Electronics Engineering, 3 (1), 2011, pp Serials Publications, ISSN : Design & Development of Real Time MATLAB-GUI Based Fuzzy Logic Controllers for DC Motor Speed Control System Immanuel J. *, Parvathi C.S., P. Bhaskar, and L. S. Sudheer * Department of Instrumentation Technology, Gulbarga University P.G Centre, Yeragera Raichur, KARNATAKA, INDIA, p_bhaskar68@yahoo.com, immanuel.j009@gmail.com Abstract: This paper presents the design and development of MATLAB based graphical user interface (GUI) for the DC motor speed control. This MATLAB-GUI is a program which acts as an interface tool between computer and user. MATLAB-GUI provides a user friendly interface to tune the fuzzy and integrated fuzzy logic controllers (IFLC) in real time environment. The performance of the motor can be observed on the axes component of the GUI. An AD-DA card has been designed and fabricated indigenously for the present study to acquire the speed and to generate control voltage to the DC motor. MATLAB-GUI is created for IFLC based DC motor speed control system using GUI components that enable an user to perform interactive tasks by programming the callback function of each component on the GUI. This GUI is used to acquire the data and to send the control action to the motor. MATLAB-GUI displays all the required parameters of the DC motor speed control system such as current speed, set point, time and controller parameter values. Also, this paper deals with the performance of controller under different standard test signals such as step, square, and set point variations. The performance of the GUI shows that tuning of various controllers is made simple and user friendly. The pop-menu on the GUI provides access to various standard step inputs. This makes the selection of standard inputs easier. The proposed MATLAB-GUI reduces the time which is consumed in tuning the controllers in other languages such as FORTRON, JAVA, C, C++ etc. The proposed MATLAB-GUI makes the system user friendly to study the performance of various real time control systems with less effort. As the other languages are little complex and are not user friendly. Keywords: MATLAB; GUI; integrated fuzzy logic controller; DC motor 1. INTRODUCTION MATLAB, which stands for matrix laboratory, is a very powerful technical language for mathematical programming. It has a very extensive library of predefined programs or functions designed to help engineers and scientists to solve their problems in a faster and less painful way, having over number of toolboxes for different subjects of study. A toolbox of a particular subject contains mainly the functions or programs required to solve problems related to the subject. The present day professional version of MATLAB is having graphical and GUI features. Writing programs in MATLAB is much easier compared to other programming languages like FORTRAN, C, C++ or Java. This is because when writing a program in MATLAB, we do not have to worry about the declaration of variables, types, sizes and memory requirements, which are the main sources of troubleshooters in other programming languages. A GUI program is a graphical based approach to execute the program in a more user friendly way. It contains components such as push buttons, text boxes, radio buttons, pop-up menus, slider etc. with proper labels for easy understanding to a less experienced user. These components help the user to easily understand how to execute or what to do to execute the program. When an user responds to a GUI s components by pressing a pushbutton or clicking a check box or radio button or by entering some text using text box, the program reads the necessary information for that particular event, hence GUI programs are also known as event driven programs. MATLAB provides a tool called GUIDE (GUI Development Environment) for developing GUI programs [1]. GUI approach is employed in various fields. In some systems GUI is built to facilitate users to apply the developed system and understand hierarchy. GUI that acts as an intermediate media creates a form of communication between users and the developed object detection system [2]. In an another application GUI is designed and developed for comparing the time specification performance between conventional controller and artificial intelligence controller in position control system of a DC motor for that GUI is developed by using Microsoft Visual Basic 6.0 for position control system [3]. The systematic procedure for construction of robustness region in the parameter plane is given in the general case of stable and unstable as well as irrational system with time delay. The developed method has implemented in MATLAB GUI for commonly used controller types PI, PID

2 134 International Journal of Electronics Engineering etc. It is believed that the developed tool may be very useful for design and tuning of industrial controller [4]. GUI based auto tuning PID controller is implemented to control oven temperature and the communication is established between DSP and a computer, where the computer hosts a GUI for the DSP card [5]. Direct current (DC) motors have been widely used in many industrial applications such as electric vehicles, steel rolling miles, electric cranes and robotics manipulators due to precise, wide, simple and continuous control characteristics [6]. The literature shows the use of GUI for measurement and control, which motivated the authors for the present work to design a GUI for DC motor speed control to the desired speed. 2. INSTRUMENTATION The experimental setup for MATLAB-GUI based DC motor speed control system is shown in Fig.1. It includes the following blocks, (i) DC Motor (ii) Tacho-generator (iii) Frequency to Voltage Converter (F/V Converter) (iv) AD-DA Board (v) PCI-1751 DIOT Card (vi) PC (vii) Buffer/Driver Fig. 1: Block Diagram of MATLAB/GUI Based DC Motor Speed Control System 2.1 DC Motor In the present study, a permanent magnet DC motor is used. The motor used has a maximum speed of rpm. The motor speed is controlled at 5000 rpm in the present study. The specifications of the motor are provided in Table 1. Parameter Size Table 1 Specifications of High Speed DC Motor Normal/rated voltage Power No load speed(max) No load current (max) Commutation Housing Weight Torque Unit 35.7mm outer diameter and 57.0mm length with 2.3mm shaft diameter 12V DC 46.7 W rpm (Rated Speed) 0.27 A Carbon brush Steel 205gms 83.0 gm.cm 2.2 Tacho-Generator It consists of slotted aluminum disc and an optical encoder. The slotted disc is made with 12 slots, which produces 12 pulses for each revolution. The disc is connected to the shaft of the DC motor. The slotted disc is made to rotate between photo-transistor and LED. When slot comes in between photo-transistor and LED, a high pulse is produced at the output of optical encoder and when the light falls on the photo transistor a low pulse is produced. The frequency of these pulses depends on the speed of the DC motor. This frequency is directly proportional to the speed of the DC motor. This measured frequency is applied to the frequency to voltage converter to get corresponding voltage. 2.3 Frequency to Voltage Converter (F/V Converter) The frequency of train of pulses from tacho-generator is converted in to corresponding voltage by using LM2907 frequency to voltage converter. LM2907 is monolithic integrated circuit F/V converter from National Semiconductor available on 14-pin DIP, to convert the frequency of pulses coming from the optical encoder into corresponding analog

3 Design & Development of Real Time MATLAB-GUI Based Fuzzy Logic Controllers for DC Motor Speed Control Systems 135 voltage. LM2907 provides an output voltage proportional to the input frequency with zero output at zero input frequency. The output voltage obtained is, V0 = Vcc*fin*C1*R1*K, where, K is the gain constant. Further the output of F/V converter is acquired through the A/D converter on AD-DA board. 2.4 AD-DA Board In the present work, for data acquisition, the AD-DA board is designed by the authors indigenously. This board contains Analog Devices make, 12-bit analog to digital converter and Burr-Brown make 12-bit digital to analog converter. Each has the following specifications [7, 8] Analog to Digital Converter Specifications Analog Devices AD1674 ADC Complete monolithic IC with 12-bit resolution and 10µsec sampling time Industry standard pin out 8 and 16-bit microprocessor interface AC and DC specified and tested unipolar and bipolar inputs ± 5V, ± 10V, 0V 10V, 0V 20V input ranges Commercial, industrial, and military temperature range grades followed by driver circuit consisting of an Op-Amp (LF356) and Darlington pair (CL100 & 2N3055) in closed loop is employed to provide enough current to drive the DC motor. The amplifier included in the closed loop will provide the compensation for voltage drop across the Darlington pair by providing biasing voltage. 3. DESIGN OF GRAPHICAL USER INTERFACE (GUI) MATLAB provides a facility to design a GUI. Fig. 2 shows integrated fuzzy logic controller GUI for DC motor speed control system. This GUI provides easy access to variable of interest i.e., DC motor speed in the present study. It has various controls on GUI such as start, exit, set point, time, scaling factor and PID constants for fuzzy PID controller etc., It allows user to set the desired set point for the DC motor speed through the edit box labeled as speed. It also displays the other parameters such as fuzzy values, and PID constants Digital to Analog Converter Specifications The Burr-Brown DAC7541A is a low cost 12-bit four quadrant multiplying digital to analog converter Single + 5V to + 15V supply Relative accuracy of ± 1LSB = ± 0.024% of FSR 2.5 PCI-1751 DIOT Card The PCI-1751 DIOT card, developed by ADVANTECH CO., LTD., is a PCI compatible card with 48 digital I/O lines and three 16-bit counter/timers. The card emulates two 8255 PPI chips to provide 48 digital I/O bits with buffered mode-0 operation and the output status can be read back. The dual interrupt capability provides user the flexibility to generate interrupts to a PC. A pin connector can output a digital signal simultaneously with the card generating an interrupt. This card uses high density small computer system interface (SCSI) 68 pin connector for easy and reliable connections to field devices [9]. 2.6 Personal Computer For the present work PC with the following specifications is used, OS Windows XP-SP3, Intel Core 2 Duo CPU with MATLAB 7 version has been used. 2.7 Buffer/Driver A driver circuit is built with the transistors to provide enough current to drive the motor. The control signal from the D/A converter can not drive the motor directly, hence a pre-amplifier Fig. 2: This GUI is used to tune the FLC, IFLC controllers. While tuning these values the results are observed on the axes provided on the MATLAB-GUI. By this GUI, user can test the performance of designed controllers under different standard test input commands such as step, sine, triangular, ramp, and set point variation etc. One of the standard test input commands are chosen through this GUI from combo box provided on the GUI. Each standard test input commands programmed in MATLAB-GUI facilitates the easy access to the different inputs. The FLC and IFLC are tuned through this GUI by clicking on Tune IFLC pushbutton. The previously tuned values of controller are retrieved by clicking on get tuned pushbutton. The new values can also be saved for future reference by clicking on save pushbutton. When all the required parameters are entered by the user; by clicking on start pushbutton the performance of the controller can be studied and DC motor speed is controlled at desired set point. By clicking on start pushbutton, GUI initializes the DIOT card and AD-DA card. GUI acquires the current speed of the DC motor and displays on the GUI. This GUI provides

4 136 International Journal of Electronics Engineering communication between DC motor and PC (hosts the GUI). MATLAB-GUI provides some user defined menu options such as file, analysis and help. Analysis menu option helps in storing the values for further analysis of the performance of the controller i.e., to get hard copy of plot or data. Help menu provides help about the GUI. 4. SOFTWARE DETAILS 4.1 Design of Fuzzy Logic Controller (FLC) Fuzzy logic controller has been used to provide solutions to control systems, which are ill defined, too complex to model etc. FLC is used to compute value of action variables from the observations of state variable of the process under control. A general fuzzy logic controller consists of four models, a fuzzification model, a fuzzy rule base, a fuzzy inference engine and a defuzzification model. In this study FLC is designed using triangular membership functions, because triangular membership functions are the best suitable for the process parameters and with centre of gravity method (COG) as defuzzification method. IF-THEN (49) rules are formed and is as shown in Table 2. i.e., IF error(e) is PL and change in error (ce) is PM THEN change in control action (ca) is PL [10]. In the present work, the fuzzy logic controller is designed in MATLAB by using fuzzy logic tool kit. This toolbox provides ease of designing FLC as it provides various GUI's. The membership functions of error, change in error, and control action is shown in Fig. 3 (a), (b) & (c) respectively. The surface view of the FLC is shown in Fig. 4. Fig. 3: (a) Triangular Membership Function Fig. 3: (b) Triangular Membership Function of Input Variable error of Input Variable Change in error Fig. 3: (c) Triangular Membership Function Fig. 4: Surface View of the Triangular of Output Variable ca Membership Function e Table 2 Fuzzy Logic Rules ce NL NM NS ZE PS PM PL NL NL NL NL NL N M NS ZE N M NL NL NL N M NS ZE PS NS NL NL N M NS ZE PS P M ZE NL N M NS ZE PS P M PL PS N M NS ZE PS P M PL PL P M NS ZE PS P M PL PL PL PL ZE PS P M PL PL PL PL

5 Design & Development of Real Time MATLAB-GUI Based Fuzzy Logic Controllers for DC Motor Speed Control Systems 137 A MATLAB GUI is created for designing the FLC and IFLC. Tune IFLC button on the GUI, the fuzzy GUI in MATLAB is opened, which allows user to tune the FLC and saves the file. Later on, this FLC is used as a controller in main GUI of the present system. The complete schematic diagram of MATLAB GUI based DC motor control system is shown in Fig. 5. The flow chart for the present system is shown in Fig. 6. Speed Control System Fig. 5: Schematic of MATLAB Based DC Motor Speed Control System

6 138 International Journal of Electronics Engineering START Initialization of variables & constants Initialization of hardware Stop the motor and open the Main MATLAB/GUI [Display current speed, set-point, PID & FLC parameters] Prompt use to enter the set-point [in the edit text box on the GUI for the speed of the motor] and scaling factor Measured speed is displayed on Main GUI Fig. 7: Step Input Response of FLC & IFLC Computation of error er & change in error ce [er=(set-point measured speed, )/5000 ce=present error-previous error Computation of IFLC (v n ) Scale the IFLC output V n to send to the motor Is 0<V n <4096? NO YES Send V n value to DAC If V n >4096 send 4096 else if V n <0 send 0 to the DAC Fig. 8: Square Input Response of the FLC and IFLC Update IFLC parameters Fig. 6: Flow Chart 5. EXPERIMENTAL RESULTS In the present study, speed of the given DC motor is controlled at 5000 rpm. Fig. 7 shows the step input comparison of FLC and IFLC. From the experimental results it is observed that IFLC gives the better performance over the FLC controller in terms of early rise time and settling time, less overshoot and undershoot. The values are tabulated as shown in Table 3. The standard square input of rpm is applied to the FLC and IFLC. FLC shows overshoot and undershoot at 4000 rpm and no overshoot and undershoot at 5000 rpm. But, IFLC shows neither overshot nor undershoot for both 5000 rpm and 4000 rpm. Fig. 9: Real Time Triangular Input Response of the FLC and IFLC The performance of controllers for step variation is shown in Fig. 9. The step variation is carried out at 1000 rpm up to 5000rpm. From the experimental results it is concluded that IFLC gives best performance over the FLC. As FLC below 1000 rpm gives considerable overshoot and undershoot but it gives better performance from 2000 rpm onwards.

7 Design & Development of Real Time MATLAB-GUI Based Fuzzy Logic Controllers for DC Motor Speed Control Systems 139 Table 3 Comparison of Step Input Response Controller FLC IFLC Parameter Present Earlier Present Earlier Study Study[12] Study Study[12] Rise time 0.84 sec 0.99 sec 0.75 sec 0.9 sec Settling time 1.03 sec 2.47 sec 0.84 sec 1.54 sec Overshoot 4.0 rpm 4.18 rpm 3.0 rpm 3.89 sec Undershoot 5.0 rpm 6.28 rpm 4.0 rpm 4.25 sec Steady state error 3.0 rpm 2.65 rpm 1.0 rpm 1.14 sec 6. CONCLUSION In the present paper an approach is made to provide a graphical user interface for the tuning of controllers and effectively running the control system. The FLC and IFLC controller are implemented in GUI. The AD-DA board is designed to facilitate the data acquisition to the GUI. The built in GUIDE tool box in MATLAB allows user to design a graphical user interface in MATLAB environment itself. i.e., for designing the GUI other software such as VB, C++ etc need not be used. MATLAB provides built in functions to program. By using built in function the callback functions of controls on the GUI are programmed. The AD-DA card provides easy access to the data to the PC. Implementation of MATLAB-GUI makes the system flexibility to the user in terms of easy operation, easy to tune controller etc. REFERENCES [1] Y. Kirani Singh, & B.B Chaudhury, MATLAB Programming, Prentice-Hall of India, New Delhi, [2] S. Sulaiman, A. Hussain, N. Md Tahir & S.A. Samad, Graphical user Interface (GUI) Developed for Object Tracking System in Video Sequences, World Applied Science Journal 4(2): pp , [3] Mohd Fuaad Rehmat & Mariam Md Ghazaly, Performance Comparison Between PID and Fuzzy Logic Controller in Position Control System of DC Servomotor, Journal Teknologi, 45(D), pp 1-17, [4] Milos Schlegel & Jiri Merit, Stability Regions for PI/PID Controller and MATLAB Program, Dept. of Cybernetics, University of West Bohemia in Pilsen. [5] Seda Postalcioglu, Emine Dogru Bolat & Kadir Erkan, Temperature Control Using Auto Tuning pid Controller for Control Education, Proce. of 5th WAEAS Int. Conf. on Signal Processing, Robotics and Automation, Madrid, Spain, February 15-17, 2006, pp [6] Moleykutty George, Speed Control of Separately Excited DC Motor, American Jour. of Applied Sciences 5(3): , [7] AD1674.pdf [8] [9] [10] Parvathi C.S, P, Bhaskar & A.B. Kulkarni, Effect of Sampling Rate on the Performance of Fuzzy Logic Controller for the Speed Control of DC Motor, IETE Technical Review, 21(4), pp , July-Aug [11] D. Driankov,H. Hellendroon & M, Reinfrank, An Introduction to Fuzzy Control, Narosa Publishing House, New Delhi, [12] Shivarajappa S. Patil, Design and Development of Multi-Input Multi-output [MIMO] Fuzzy System, Ph.D Thesis, Submitted to Gulbarga University, P. G, Centre, Raichur, 2010.