Ijetae 0312 24

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 3, March 2012)

146

Modeling, Simulation and Implementation of Speed

Control of DC Motor Using PIC 16F877A

Payal P.Raval1, Prof.C.R.mehta

2

1PG Student, Electrical Engg. Department, Nirma University, SG Highway, Ahmedabad, Gujarat, India. 2Asst. Prof. Electrical Engg. Department, Nirma University, SG Highway, Ahmedabad, Gujarat, India.

[email protected]

[email protected]

Abstract— The Microcontroller based adjustable closed-loop

DC motor speed controller systems has already become an

important drive configuration for many applications across a

wide range of powers and speeds . This is due to their simple

control, high reliability, low cost and fast response. Control

System Design and Analysis technologies are widely suppress

and very useful to be applied in real-time development. Some

can be solved by hardware technology and by the advance

used of software, control system are analyzed easily.

Fractional HP DC Motors can be used in various applications

and can be used as various sizes and rates. The designed

circuit is stimulated using Real peak and MP LAB. In this

paper, control techniques of PIC 16F877A microcontroller

and MOSFET, mechanism assignments of analyzed by mainly

focusing with the “Modeling and Simulation of DC Motor

using MATLAB”.

Keywords—DC Motor, MATLAB/ Simulink , PIC.

I. INTRODUCTION

Traditionally, the DC Motors and the associate close

loop control systems used to drive them have been

modeled using classic control theory techniques, based on

transfer functions. Control system design and analysis

technologies are widely suppress and very useful to be

applied in real-time development. Some can be solved by

hardware technology and by the advance used of software,

control system are analyzed easily and detail. DC Motors

can be used in various applications and can be used as

various sizes and rates. The microprocessor computes the

actual speed of the motor by sensing the terminal voltage. It

then compares the actual speed of the motor with the

reference speed and generates a suitable control signal

which is fed into the triggering unit. This unit drives a

Power MOSFET amplifier, which in turn supplies a PWM

voltage to the dc motor.

The objective of this paper is to explore the approach of

designing a microcontroller based closed loop controller.

The interface circuit and the software are all designed to

achieve a better performance.

The microcontroller system is equipped with an LCD

display and a keypad and software was written to monitor

the registers on the LCD and read commands from the

keypad. Thus, by using the User Interface Module (UIM)

the operator can view and/or change all the control and

monitoring variables of the controller program.

II. MODELING A DC MOTOR

For modeling and simulation of a DC Motor, simple circuit

of its electrical diagram as shown in Figure 1 is to be

considered.

A. Closed-Loop System Consideration

To perform the simulation of the system, an appropriate

model needs to be established. Therefore, a model based on

the motor specifications needs to be obtained. Figure-1

shows the DC motor circuit with Torque and Rotor Angle

consideration.

Fig.1.Schematic Diagram of a DC Motor



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B. System Equation

The motor torque T is related to the armature current, i , by

a torque constant K;

(1)

The generated voltage, ea, is relative to angular velocity by

(2)

(3)

From Fig. 1 we can write the following equations based on

the

Newton’s law com bined with the Kirchoff’s law:

+ b = Ki (4)

+RI =V - K (5)

C. Transfer Function

Using the Laplace transform, equations (3) and (4) can be

written as:

(6)

(7)

Where s denotes the Laplace operator. From (7) we can

express I(s):

(8)

and substitute it in (5) to obtain:

(9)

This equation for the DC motor is shown in the block

diagram in Fig. 2. From equation (8), the transfer function

from the input voltage, V(s), to the output angle θ, directly

follows:

(10)

From the block diagram in Fig. 2, it is easy to see that the

transfer function from the input voltage, V(s), to the

angular velocity is:

(11)

D. MATLAB Representation

To represent the model with m-file, we can perform the

Fig. 2 data as follows;

Power P = 0.37 kW

Speed N = 1500 rpm ,

Rotor Inertia J is assumed to be 0.01

Supply voltage = 220 volts.

Calculate the torque constant K;

(12)

K=1.4

By using equation (3) for

(13)

At the steady state (used as analyzed data), both I and ω are

stabilized;

And

(14)

(15)

Following value are assigned to be used for our desire

DC Motor Model:

Vt = 220v; J=0.01; b=0.02; k=1.4; Ra=13.5 Ω; La=132.5

mH. By calculating and assuming the require data as above.



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Figure.2 Closed loop system that Representing the DC motor

D. Analysis

We plot the step, impulse and frequency responses of the

given motor model:

Fig.3(a) Step response using simulink model.

Fig. 3(b) Impulse response using simulink model.

III . SIMULINK MODEL

The block diagram of Fig. 2 can be represented and

created as a model as shown in Fig. 4. The approaching to

construct this model can easily be done by using Simulink

Library. The M- file and Simulink model can be combined

by the following commands and these are commands used

in M-file which can be solve it.

Figure.4 Model created in SIMULINK Toolbox of MATLAB

Figure.5. Final results using simulink model (with Step response)



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IV. SYSTEM DESCRIPTION

The input from the stable power supply unit (230 V AC)

is converted into 12v AC by means of a step down

transformer, the output of this is used as input to bridge

rectifier circuit. Here in this system bridge rectifier will

generate 5 V DC with the help of regulator 7805. The

output of the 7805 regulator is used as an input to the PIC.

The PIC will generate pulses to drive the DC motor

according to the requirement. As the output voltage of the

PIC is in mV, driver circuits are used to drive the DC motor

An optical encoder is used to measure the speed of the

motor. The output of the encoder is a stream of pulses with

variable frequency according to the speed of the motor. The

optocouplers were used to isolate the high voltage circuits

from the low voltage controlling signals. The rating of the

motor should be chosen according to the rating of the

power circuit.

For this study a dc shunt motor with ratings 1500 rpm,

220 V, 2.3 A, 0.37 kW is used. The entire operation of the

blocks is explained briefly as follows with the diagram as

shown in figure.6 below.

Fig.6.Circuit diagram for DC Motor speed control.

A. Microcontroller PIC16F877A.

Peripheral Interface Controller (PIC) is a term

introduced by Microchip technology. PIC 16F877A is a

family of CMOS 8-bit Flash microcontrollers[3]. Power

consumption is very low. PIC16F877A is a 40/44-pin

device which can operate at up to 20 MHz clock speed.

It has 8K * 14 words flash program memory, 368*8

RAM data memory, 64bytes of EEPROM nonvolatile

data memory, 8-bit timer with pre-scalar, watchdog

timer, Only 35 single-word instructions to learn, external

and internal interrupt sources and large sink and source

capability. The architecture is shown in Fig.3[3]

Fig.7.Architecture of PIC16F877A Microcontroller

B. Driver Circuit

This driver circuit is designed based on the DC motor

current ratings, The current rating of the DC motor is 2.3

Amp So driver circuit is needed. It is the most popular

and cost effective drive circuits for driving MOSFETs. A

bipolar, non-inverting totem-pole driver as shown in Fig 4.

Transistors can be used to supply higher current to the

motor. This circuit handles the current spikes and power

losses making the operating conditions for the PWM

controller more favorable.

Fig.8 Driver Circuit



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V . SIMULATION RESULTS

The proposed control circuit is implemented using software

module like Real PIC Simulator as shown in Fig 9. For the

purpose of coding the software package used is MPLAB.

Fig.9(a) Output pulses of PIC16F877A through MPLAB IDE for

ω=500rpm

Fig.9 (b) Output pulses of PIC16F877A through MPLAB IDE for

ω=1500 rpm

VI. HARDWARE SETUP AND RESULTS

A. Minimum Hardware connections of PIC16F877A

The results shown are for the motor having parameters:

V = 220 V, ω=1500 rpm, P = 0.37 kW, I=2.3 A.

The minimum hardware connections circuit board is as

shown in Fig.10. Two pins are used to provide supply

voltage tochip. The stable power supply of +5 V is used.

If any suddenly jerk is coming our PIC IC will not

damage. Two pins are also used for ground. In chips with

40pins and more, it is common to have multiple pins for

Vcc and GND. This will help reduce the noise (ground

bounce) in high-frequency systems. The PIC 16F has many

options for the clock source. Most often a quartz crystal

oscillator is connected to input pins OSC1 & OSC2. PIC

16F877A microcontroller can have speed of 0 Hz to 20

MHz.

Figure.10 PIC 16F877A Hardware Connection with Power Supply,

Driver circuit and LCD Display

B. Bridge Rectifiers, Regulator and Driver circuit

The bridge rectifiers,Regulator and driver circuit used to

convert 230 V AC to 12 V DC and 5 V DC to give as input

to the PIC 16F877A controller is shown in Fig.11

Fig.11. Bridge rectifiers, Regulators and driver circuit

C. Optical Encoder and Rotating disk

The most popular type of encoder is the optical encoder,

which consists of a rotating disk, a light source, and a photo

detector (light sensor). The disk .which is mounted on the

rotating shaft, has coded patterns of opaque and transparent

sectors.

Bridge ckt Driver

circuit

LCD

PIC

Power

supply

s

Driver ckt



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As the disk rotates, these patterns interrupt the light

emitted onto the photo detector, generating a digital or

pulse signal output. It is shown in fig. 12 .

Figure.12.Optical Encoder and rotating disc (8 Number of Slots)

which is mounted on the rotating shaft

The corresponding output pulse of PIC is as shown in

Fig 13 on CRO and Fig 14 on LCD

Fig.13Practical output pulse of pic16F877A in CRO

Fig.14.Practically Actual & Ref. speed on LCD ω = 750 rpm

VII. CONCLUSION

The DC machine is considered to be basic electric

machines. The aim of this paper is to introduce Technicians

to the modeling of power components and to use computer

simulation as a tool for conducting transient and control

studies. The Microcontroller based adjustable closed-loop

DC motor speed controller system has been developed. .

The results showed that the microcontroller is a reliable

instrument to control the motor. This system is applicable

to different sizes of motors and capable of controlling the

speed of the motors with very high precision.

VIII. REFERENCES

[1] Wai Phyo Aung, “Analysis on Modeling and Simulink of DC Motor

and its Driving System Used for Wheeled Mobile Robot” , PWASET

VOLUME 26 DECEMBER 2007 ISSN 1307-6884.

[2] Gopal K. Dubey, Fundamentals of Electrical Drives, 2nd edition,

Narosa Publishing House, New Delhi-2007.

[3] Muhammad Ali Mazidi, PIC Microcontroller and Embedded systems

using Assembly and C for PIC16, Pearson Education, 2008.

[4]Ajay V. Deshmukh, “Microcontrollers: Theory and applications”, Tata

McGraw-Hill

[5] 7805 and 7812 Voltage Regulator ICs-Data sheets.

[6] “PIC16F877A” Data sheet from Microchip Corporation.

[7] MPLAB IDE Software-Microchip technology.

Optical

encoder

Rotating

disk

Ijetae 0312 24

Engineering

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