microcontroller based control of bldc motor

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Journal of Engineering Research and Studies E-ISSN0976-7916

JERS/Vol. II/ Issue IV/October-December, 2011/

Research Article

MICROCONTROLLER BASED CONTROL OF THREE

PHASE BLDC MOTOR P. Devendra

1*,

2Madhavi TVVS*,

3K Alice Mary,

4Ch. Saibabu

Address for Correspondence1Associate Professor, EEE dept, GMR Institute of Technology, Rajam, Andhrapradesh, India

2PG Student, EEE dept, GMR Institute of Technology, Rajam, Andhrapradesh, India

3Professor & Head, Electrical and Electronics Engineering Department, Vignan’s Institute of Information

Technology, Vishakhapatnam, India4Professor, Electrical and Electronics Engineering Department, Jawaharlal Nehru Technological University,

Kakinada, India

ABSTRACT

This paper introduces a novel method which is intended to assist in the design and control of cost effective, efficient

Brushless Direct Current (BLDC) motors with additional features like auto restart and auto power down while maintainingconstant speed. Speed Control of BLDC motor using 8051 micro controller requires more hardware, and with the

availability of PIC microcontrollers with versatile features motivated to develop a cost effective and reliable control withvariable speed range. In the present paper, an algorithm which uses the Hall sensor signals acquired from the motor is

developed and the program has been written using MPLABIDE v 7.52. This program generates the firing pulses required to

drive the MOSFETs of three phase fully controlled bridge converter driven by IR2101 FET drivers. Later the program has been dumped on the PIC16F series device and tested on the 24V, 80 W, 1500 rpm BLDC motor which can make the motor

run at constant speed ranging from 6 to 1500 rpm. The proposed hardware and the program are found to be efficient and the

results are promising.

KEYWORDS Brushless Direct Current motor, PIC16Fseries, MPLABIDE, Hall sensor, IR2101 FET driver.

I. INTRODUCTION

PERMANENT magnet brushless dc (BLDC) motors

have used wide application due to their power

density and ease of control. Moreover, the machines

have high efficiency over a wide speed range. The

highly efficient conventional DC motors are suitable

for various applications because of their

characteristics. They require commutator and brushes, for conversion of dc to ac which are subject

to wear and require maintenance. This only

drawback of conventional DC motors makes us to

shift to BLDC motors which are electronically

commutated by using solid state .Recent legislation

imposing efficiency standards in appliances, has

forced appliance manufacturers to migrate to BLDC

motors in their applications. In view of these

enormous applications, researchers started

developing methods for efficient use of these motors

in diversified fields. To mention a few: Jianwen

Shao Nolan et.al [1] has developed a novelmicrocontroller-based Sensorless brushless DC

(BLDC) motor drive for automotive fuel pumps in

2003. Also, they have developed an Improved

Microcontroller-Based Sensorless Brushless DC

(BLDC) Motor Drive for Automotive Applications,

in 2006[2]. Nikolay Samoylenko [3] studied the

Dynamic performance of Brushless DC motors with

unbalanced Hall sensors.

To the extent the authors have surveyed not much

work has been reported on micro controller driven

sensor based BLDC motors. Hence in this paper, an

algorithm for sensor based micro controller driven

BLDC motors with additional features like auto

restart and auto power down is presented and

effectiveness of the work is shown through

hardware realization.

II. R EVIEW OF BLDC MOTOR CONTROL

SCHEMES

The control schemes of BLDC motor are mainly

classified in following two ways

• Sensor based control

•

Sensor less controlIn sensor based control, a Hall sensor is used which

detects the position of the rotor magnet and gives a

signal which is used to give appropriate excitation to

the stator winding. Hall sensor works on Hall effect

which states that when a current carrying conductor

is placed in magnetic field, it exerts a transverse

force on the conductor. The sensor based control

scheme is shown in Fig.2.

Fig.2 Sensor based control

Micro controller based control using Hall sensors

gives effective control on BLDC motors.

The sensor less drive principle is based on the

detection of the rotor position using varioustechniques one of which is the EMF detection.

There are various methods for position and velocity

estimation based on the induced Back EMF





detection. Various micro controllers and DSP

controllers are available for sensor less control.

III. MICROCONTROLLER BASED

CONTROL SCHEME

The proposed control for BLDC motor control using

PIC microcontrollers of MICROCHIP with device

name PIC16F690 is shown in the figure (3).

Fig.3 Micro Controller based Control

The base drive to the MOSFETS in the Inverter

circuit is given by the PIC16F690 micro-controller.

The Hall signals from the motor are fed as inputs tothe PIC16Fseries device and based on the Hall

position and the direction of rotation of the motor

specified by the manufacturer the corresponding

gate drive is made active by the microcontroller and

fed to the stator of the BLDC motor.

The commutation sequence for rotating the motor in

clock wise direction when viewed from the non

driving end is given in the Table (1).

Table (1): Sequence for rotating motor in

clockwise direction

Based on the Hall sensor input to the

microcontroller, the corresponding transistors are

made active and current flows through two windings

and the other winding is inactive and hence

commutation is done electronically with the use of a

microcontroller.

The commutation sequence for rotating the motor in

counter clock wise direction when viewed from the

non driving end is given in the Table (2).

Thus by properly exciting the correspondingwinding based on the hall signal, the motor is

commutated and is made to run at the desired speed.

Initially irrespective of the rotor position, the

windings are excited in the given sequence and once

the motor starts rotating, rotor position is sensed by

the Hall sensor and then the motor is excited based

on the Hall signal and according to the direction of

rotation of the motor.

The speed can be controlled in a closed loop by

measuring the actual speed of the motor. If the

speed is greater than the desired rated speed, then all

the transistors are turned off for a short duration and

then again excited based on the Hall position and

accordingly speed can be adjusted to get constant

speed. The ADC of the microcontroller is used to

convert the analog signal corresponding to the speed

of the motor to a digital value and comparison is

done with the calculated digital value which is

proportional to the rated speed

A. PIC16Fseries Micro controller

PIC16Fseires microcontroller which is used for this

project is a 40-pin device, 8 bit CMOSMicrocontroller which belongs to the MICROCHIP

family of microcontrollers. It has 10-bit Analog to

Digital converter (ADC) and we have used only 8

bits for our control so that the speed can be

controlled in 255 steps ranging from 6 to 1500 rpm.

The various features of this device make this device

to be selected for the proposed control. Timer1 is

operated in external oscillator mode with an external

crystal oscillator of 20 MHz connected to the micro

controller device. An external Potentiometer is

connected to the ADC pin which provides the

required speed range. B. Algorithm for Assembly language code written

using MPLAB IDE v7.52tool

MPLAB IDE v7.52tool of MICROCHIP has been

used to write the code in assembly language using

PIC16F690 data sheets provided by MICROCHIP.

The algorithm to run and maintain constant speed of

a BLDC motor is

• Set PORTE as digital hall input.

• Set PORTC as Outputs to transistors.

• Generate interrupt on timer1 over flow and

also on completion of ADC conversion by

setting the appropriate registers.

• Enable Global interrupt.

• Give excitation to the motor windings

irrespective of the Hall signal according to

the direction of rotation of the motor (clock

wise or counter clock wise).

• Start TIMER1 which is operated with

external crystal oscillator at 20 MHz

frequency

• Generate LOOK-UP Table for clock wise

rotation of the motor irrespective of the

Hall signal.• At the timer overflow interrupt service

routing (ISR), generate LOOK-UP Table





for clock wise rotation of the motor based

on Hall signal.

• Set the motor speed using external

potentiometer connected to the ADC pin.

• Enable ADC to convert the analog voltage

into digital.

• Compare this digital value with the counter

value equivalent to the motor speed (rated).

• If motor speed is higher than the rated

speed then turn off all the transistors for

short duration in ADC conversion complete

ISR and return back from the ISR.

• Then repeat the excitation process based on

Hall signal.

• This program drives the BLDC motor at

constant speed and by varying the external

potentiometer value we can change the

motor speed and according make the motor

run at that constant speed.This algorithm is used to write a program in

MPLAB IDE and is dumped on to the PIC16F690

device and tested on the 24 V, 80 W, and 1500 rpm

BLDC motor shown in the figure (4).

Fig (4) 24 V, 80 W, 1500 rpm BLDC motor

IV. PROPOSED HARDWARE FOR BLDC

MOTOR

Proposed hardware consisting of mainly following

basic circuits

a) Microcontroller circuit

Fig (5) Microcontroller circuit

b) FET driver circuit:

Fig (6) FET driver circuit

The complete hardware set up for the motor control

is shown in Fig (7).

Fig (7) The complete Hardware set up

V RESULTS & DISCUSSIONS

The pulses generated from the microcontroller

control circuit are

Fig.7 Pulses to drive the MOSFETs

The pulses shown in the figure (7) are fed to the

24V, 80 W, 1500 rpm BLDC motor and the motor

voltage equivalent to 1500 rpm speed is shown infigure (8).

Fig.8 BLDC motor voltage waveform equivalent

to 1500 rpm speed





V. CONCLUSION

The proposed algorithm has been programmed in

MPLABIDE v 7.52. and it generates the firing

pulses required to drive the MOSFETs of three

phase fully controlled bridge converter. The

program has been dumped on to the PIC16Fseries

device and fed to the MOSFETs of three phase fully

controlled bridge converter driven by IR2101 driver

circuit. The output from the converter is fed to the

three phase stator winding of 24V, 80 W, 1500 rpm

BLDC motor and the motor is found to run at

constant speed which is set by the external

potentiometer connected to the microcontroller

circuit. The program is found to be efficient and the

results with the designed hardware are promising.

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microcontroller based control of bldc motor

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