Microcontroller Based Electrical Machines Training Set

Ramazan Bayındır1, Ersan Kabalcı2, Orhan Kaplan1, Yunus Emre Öz3

(GEMEC) Gazi Electrical Machines and Energy Control Group 1Gazi University, Faculty of Technology, Ankara, Turkey, bayindir@gazi.edu.tr, okaplan@gazi.edu.tr

2 Nevsehir University, Faculty of Engineering and Architecture, Nevsehir, Turkey, kabalci@nevsehir.edu.tr 3Gazi University, Technical Education Faculty, Ankara, Turkey, ozyunusemre@gmail.com

Abstract — In this study, a multi-purpose training set has been designed and implemented as an auxiliary learning tool to teach the main concepts of electrical motors for students who attend the vocational and technical education. The system deals with three types of electrical motors as direct current (DC) motor, stepper motor and servo motor, which are controlled by a microcontroller. Although most of the systems in classical laboratories are focused on experimental activities without theoretical substructure, the system presented integrates the hands-on activities with the theoretical information. For this purpose, the theoretical information related to each electrical motor in the system has been given to the students firstly. Then, proficiency of the students has been evaluated using test questions related to the topic. Finally, if the students are reached to the desired level, they can perform the experimental studies using the system in order to efficiently reinforce the theoretical courses they have already learned. Combining the theoretical information with the application studies can be shown as an advantage of this study.

Keywords — Electrical machines training set, DC motor, stepper motor, servo motor.

I. INTRODUCTION The information to be transferred to students in

vocational and technical education is realized in two basic levels [1]. One of these is the theoretical part where the comprehending the concepts and mathematical analyses. It is aimed to get the students to solve various problems and analyzing the results that are related to novel subjects learned at the theoretical part. The second part of the education involves practical applications done in the laboratory. The applications realized in this part simplify to produce solutions to problems met in the professional work by reinforcing the education stage. The knowledge and problem solutions that are obtained in the first part of education are supported by the experimental studies done in the second stage, and an effective and permanent education stage is obtained. However, the lack of laboratory and auxiliary equipment cause to hitches on experimental studies [2].

Electric machines are one of the most important subjects in the electrical education. Due to technological developments, motor control and drive systems are rapidly improved and widely used in industrial applications [3]. Pure theoretical education in electric machines lecture is not enough to get students comprehend the required knowledge. Even though the

modelling and simulation studies support the education period, these will not stand for experimental studies performed in the laboratory in terms of knowledge and experience. In addition to this, several assumptions done by the software may affect the expected results comparing to experimental real-time studies. The literature surveys show that various experimental education sets are developed in order to support the laboratory studies in vocational and technical education institutes. These sets are classified in two ways such as settled training sets and internet controlled real-time and remotely accessed training sets. The first training set group can be exemplified with DC-DC Buck, Boost, and Buck-Boost converter training set and application given in [4], power electronics set implemented and utilized in [5], position and speed control of a servo motor with microcontroller [6], or microcontroller programming sets [7,8]. In addition to these, real-time and remote accessed internet based training systems are also widely used in vocational education [9-13].

In this study, a multi-purpose education and training set is designed and implemented to comprehend operation principles of electric machines to students that are in vocational and technical education level. The implemented training set can be used in direct current motor, stepper motor, and servo motor trainings owing to its PIC18F452 microcontroller. Initially the theoretical knowledge about the desired electric motor is taught. Afterwards, the learning level of student is surveyed with test questions and he/she is permitted to realize the experimental study in case of he/she has reached the desired knowledge level. The developed training set allows students to perform applications safely.

II. DESIGN AND APPLICATION In this study, the training set consisting of experiments

of electrical machines, which are DC motor, stepper and DC servo motor, is designed and implemented. Block diagram of the training set is shown in Fig. 1.

The DC motor used in the training set has permanent magnet structure with an encoder located on the shaft of the motor. Proportional–integral (PI) controller is used in order to control the speed of the motor.

The pulse width modulation (PWM) signals are generated the control unit by comparing the analogue value acquired from the encoder with the reference speed value of the motor to accomplish the speed value desired. The PI controller cited is indicated in Fig. 2.

15th International Power Electronics and Motion Control Conference, EPE-PEMC 2012 ECCE Europe, Novi Sad, Serbia

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Fig. 1. Block diagram of the training set

Fig. 2. Block diagram of the DC motor closed loop speed control with PI controller

The other motor used in the training set is a stepper

motor with the step angle at 1.8 degree. The stepper motors are brushless, synchronous electric motors whose full cycle can be divided into small steps. The design of the stepper motor determines the degree value per step. The motor control can be realized by pulsed signals applied to input of the motor without any feedback. Also the speed and rotation direction of stepper motor can be altered by changing frequency and order of the input pulse respectively.

Finally a servo motor is used in the training set developed. Drivers of synchronous motor receive signals, which are required to control, from microcontrollers or computers. The feedback signal can be acquired through various sensors or position potentiometers by connecting to the rotor of servo motor. These signals are real position data of the rotor for control unit. Servo motors, which are widely used in control applications in industry, are different from stepper motors with respect to closed loop control. Closed loop control cannot be used in the stepper motors owing to step angles known, otherwise any step-jump event may occur and the position data of stepper motor may be lost.

On the other hand, a servo motor whose control algorithm and environmental units are designed correctly can be realized without step-jump event. The training set designed is put in transparent box as shown in Fig. 3, so that it can easily be carried and students can observe the operations performed.

Fig. 3. The training set designed

III. SOFTWARE

The software of microcontroller is prepared with C programming language. The control software consists of three stages. In the first stage, the desired the theoretical information is given to students about the related motor type, and thus students’ knowledge level can be increased. In the second stage, level of proficiency of students is briefly measured by testing on the information given. If the test questions are answered correctly, students can pass experiments menu and operate the motor desired by changing parameters such as speed, direction of rotation, step number, step-angle in the last stage. Furthermore motor parameters are shown through graphical liquid crystal display (LCD). The software flowchart is given in Fig. 4.

Fig. 4. Flowchart of the set designed

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IV. EXPERIMENTAL STUDY

In this section, the stepper motor experiment that is one of the experiments in the training set designed has been performed. The screenshot that users can select what to desire the motor and is given in as Fig. 5 is monitored when the training set is started. Motor selection is made by using with the keypad.

Fig. 5. The view of motor selection menu

After the motor selection is performed by users, theoretical information which is operation principle, structure, types etc. about the motor selected is shown on the display. In Fig. 6, some theoretical information is indicated about the stepper motor.

Fig. 6. The theoretical information menu After theoretical information is transferred to users, the

student's proficiency level is tested by using the exam which is prepared with in the form of true/false questions. A few screen appearances are shown in Fig. 7. If users answer correctly the exam about the motor preferred, the training set designed allows for the experimental study of the motor. Otherwise users do not implemented the experimental study because of lack of their proficiency level. Then students are backwards directed to the theoretical information stage and the information about the motor is presented again.

Fig. 7. The exam menu to test student's proficiency level

The users achieving the exam go forward the final stage consisting of the experimental study related to the desired motor. In this stage, users can determine motor parameters such as speed, step number, direction of rotation etc. by using the keypad and run the motor under the desired condition. The parameters selection stage is shown as given Fig. 8.

Fig. 8. The parameters selection menu

While motor is running, users can observe

instantaneous value of the motor operation on the display as shown in Fig. 9. Therefore, users can follow response of the motor numerically. Users can implement another experiment pressing the reset button become on the set designed.

Fig. 9. The view of instantaneous value of the motor operation

V. CONCLUSION

In this study, an education set has been designed and implemented, so that learning can be more affective. The training of three different electrical motors which are DA motor, stepper motor and servo motor are implemented in the designed education set. The designed set is placed in a transparent box that provides users to observe easily. The main superiority of the system is that measurement, evaluation and practice are presented to students together. Each student can easily use the education set thanks to ease of software developed. Also, the designed system is as small as an A4 paper dimensions, thereby it can easily be carried. Due to the education set implemented, experience gained students can install, develop and repair similar system in industry.

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