Control L6234, Olimexino 1.INTRODUCTION Brushless DC electric

            Control of Brushless DC Motor

 

Sunilkumar Raghuraman,
Nandhini Santhanam, Varun Srinivasan                    Department of High
Integrity System                                                                
Frankfurt University of Applied Sciences                                                               
Nibelungenpl. 1, 60318 Frankfurt am Main, Hessen, Germany

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Abstract:  This
paper aims at implementing a way to control the speed of Brushless DC Motor
through Arduino controller. The speed of the motor is increased or decreased
whenever the corresponding switches are pressed. The direction of the motor is
changed by

Keywords: BLDC motor, L6234, Olimexino

 

1.INTRODUCTION

Brushless DC electric motor (BLDC motors are synchronous motors powered
by DC electricity via
an inverter or switching
power supply which produces an AC electric
current to drive each phase of the motor via a closed loop controller. The
controller provides pulses of
current to the motor windings that
control the speed and torque of
the motor.

Unlike
conventional brushed type DC motor, wherein the brushes make the mechanical
contact with commutator on the rotor to form an electric path between a DC
electric source and rotor armature windings, BLDC motor uses electrical
commutation with permanent magnet rotor and a stator with a sequence of coils.
In this motor, permanent magnet (or field poles) rotates and current carrying
conductors are fixed. This electronic commutation arrangement
eliminates the commutator arrangement and brushes in a DC motor and hence more
reliable and less noisy operation is achieved. Due to the absence of brushes
BLDC motors are capable to run at high speeds

A BLDC motor
accomplishes commutation electronically using rotor position feedback to
determine when to switch the current. The stator windings work in conjunction
with permanent magnets on the rotor to generate a nearly uniform flux density
in the air gap. This permits the stator coils to be driven by a constant DC
voltage, which simply switches from one stator coil to the next to generate an
AC voltage waveform

The BLDC Motor
which we are using in this project is Brushless Motor Roxxy Outrunner C28-24-34
1100kv which operates in 7 to 12 volts.

28mm means the
diameter of the motor

24mm means the
high of the motor

34 means the no of
the wire turn that goes around each poles inside the motor

Small the number
the faster the motor will typical turn but with less torque

Higher the number
stronger the magnetic field is and the more torque the motor has but that
magnetic field takes a little bit longer to set up so we tend to sacrifice a
bit of speed.

1100 kv is the
revolutions per min per volt

BLDC Construction

Any BLDC motor has two primary parts; the rotor, the rotating part, and
the stator, the stationary part. Other important parts of the motor are the
stator windings and the rotor magnets.

 

 

Rotor

Depending upon the application requirements, the number of poles in the
rotor may vary. Increasing the number of poles does give better torque but at
the cost of reducing the maximum possible speed.

Another rotor parameter that impacts the maximum torque is the material
used for the construction of permanent magnet; the higher the flux density of
the material, the higher the torque.

Stator

The BLDC motor stator is made out of laminated steel stacked up to carry
the windings. Windings in a stator can be arranged in two patterns; i.e. a star
pattern (Y) or delta pattern (?). The major difference between the two patterns
is that the Y pattern gives high torque at low RPM and the ? pattern gives low
torque at low RPM. This is because in the ? configuration, half of the voltage
is applied across the winding that is not driven, thus increasing losses and,
in turn, efficiency and torque.

There are two basic BLDC motor designs: inner rotor and outer
rotor design.

add picture

.

Hall Sensors: Hall sensor
provides the information to synchronize stator armature excitation with rotor
position. Since the commutation of BLDC motor is controlled electronically, the
stator windings should be energized in sequence in order to rotate the motor.
Before energizing a particular stator winding, acknowledgment of rotor position
is necessary. So the Hall Effect sensor embedded in stator senses the rotor
position.

Whenever the rotor
magnetic poles pass near the Hall sensors, they give a high or low signal,
indicating the N or S pole is passing near the sensors. Based on the combination
of these three Hall sensor signals, the exact sequence of commutation can be
determined.

Working Principle
and Operation of BLDC Motor

The rotor of the bldc magnet is the Permanent magnet and the stator is
the electromagnet which is achieved by the coil arrangement of the windings.
There will be three phases(poles) inside the stator to which the direct current
is applied.

Each commutation sequence has one of the windings energized to positive
power (current enters into the winding), the second winding is negative
(current exits the winding) and the third is in a non-energized condition. Torque
is produced because of the interaction between the magnetic field generated by
the stator coils and the permanent magnets. The peak torque occurs when these
two fields are at 90° to each other and falls off as the fields move together.
In order to keep the motor running, the magnetic field produced by the windings
should shift position, as the rotor moves to catch up with the stator field and
is known as “Six-Step Commutation” defines the sequence of energizing the
windings

When the stator
coils are electrically switched by a supply source, it becomes electromagnet
and starts producing the uniform field in the air gap. Though the source of
supply is DC, switching makes to generate an AC voltage waveform with
trapezoidal or sinusoidal shape. Due to the force of interaction between
electromagnet stator and permanent magnet rotor, the rotor continues to rotate.

 

Commutation Sequence:

Every 60
electrical degrees of rotation, one of the poles changes the state. So, it
takes six steps to complete an electrical cycle. In synchronous, with every 60
electrical degrees, the phase current switching should be updated. But one
electrical cycle may not correspond to a complete mechanical revolution of the
rotor. The number of electrical cycles to be repeated to complete a mechanical
rotation is determined by the rotor pole pairs. For each rotor pole pairs, one
electrical cycle is completed. Add Image

A motor with n pole pairs can be controlled the same
way as a motor with one pole pair. ‘Rotating’ through one electrical period
will turn the motor by 1/n mechanical periods Add Image

 

We can use the
hall sensor output to vary the voltage given to different phases of the motor. In
this project, We did not use the hall sensor. But we varied the potential of
the phases of the motor by following the below mentioned commuting sequence Add image.

Clockwise direction:

Sequence

Voltage at A

Voltage at B

Voltage at C

1

DC+

Off

DC-

2

DC+

DC-

Off

3

Off

DC-

DC+

4

DC-

Off

DC+

5

DC-

DC+

Off

6

Off

DC+

DC-

 

Counter Clockwise Direction

Sequence

Voltage at A

Voltage at B

Voltage at C

1

Off

DC-

DC+

2

DC+

DC-

Off

3

DC+

Off

DC-

4

Off

DC+

DC-

5

DC-

DC+

Off

6

DC-

Off

DC+

 

Advantages of BLDC
Motor

BLDC motor has
several advantages over conventional DC motors and some of these are

It has no mechanical commutator and
associated problems
High efficiency due to the use of
permanent magnet rotor
High speed of operation even in
loaded and unloaded conditions due to the absence of brushes that limits
the speed
Smaller motor geometry and lighter in
weight than both brushed type DC and induction AC motors
Long life as no inspection and
maintenance is required for commutator system
Higher dynamic response due to low
inertia and carrying windings in the stator
Less electromagnetic interference
Quite operation (or low noise) due to
absence of brushes

Disadvantages of
BLDC Motor

These motors are costly
Electronic controller required
control this motor is expensive
Not much availability of many
integrated electronic control solutions, especially for tiny BLDC motors
Requires complex drive circuitry
Need of additional sensors

Applications of
BLDC Motors

Brushless DC
motors (BLDC) are
used for a wide variety of application requirements such as varying loads,
constant loads and positioning applications in the fields of industrial
control, automotive, aviation, automation systems, health care equipments, etc.
Some specific applications of BLDC motors are

Computer hard drives and DVD/CD
players
Electric vehicles, hybrid vehicles,
and electric bicycles
Industrial robots, CNC machine tools,
and simple belt driven systems
Washing machines, compressors and
dryers
Fans, pumps and blowers

 

 

 

 

 

 

2.METHODOLOGY

In this project,
we are going to control the speed of BLDC motor through Arduino leonardo
controller. The motor speed will be increased and decreased by the
corresponding buttons as an input. The direction can also be changed by
decreasing the speed in one direction to minimum and then changing the
direction of the motor to the other side.

In order to
control the speed of the BLDC motor through Arduino, motor driver IC is needed
in order to amplify the output voltage from the Arduino which should be given to
the motor. L6234 motor driver is used for this purpose. The L6234 is a DMOSs
triple half-bridge driver with input supply voltage up 52V and output current
of 5A.

The following pin
configuration is used for the connection, since the IC used is of type DIP
configuration.

 

 

 

 

 

 

 

 

 

 

PIN Description:

OUT1, OUT2, OUT3: These are the
output pins that correspond to the midpoint of each half bridge inside the IC
and this three will be connected to the U, V, W phases of the motor
respectively.

IN1, IN2, IN3: These are the input pins for the Motor
driver IC. The output from the Arduino is connected as an input to the motor
driver IC.

EN1, EN2, EN3: These are the enable pins of the Motor
driver IC. The output from the Arduino is connected as the enable input for the
motor driver IC

Vref (Voltage
Reference): This
is the internal 10V voltage reference pin to bias the logic and the low voltage
circuitry of the device. A 1mF electrolytic capacitor connected from this pin
to GND ensures the stability of the DMOS drive circuit.

 

Vcp (Charge Pump):
This
is the internal oscillator output pin for the charge pump. The oscillator
supplied by the 10V Voltage Reference switches from GND to 10V with a typical
frequency of 1.2MHz.
When
the oscillator output is at ground, C3 is charged by Vs through D1. When it rises
to 10V, D1 is reverse biased and the charge flows from C3 to C4 through D2, so
the Vboot pin after a few cycles reaches the maximum voltage of Vs + 10V – VD1-
VD2.

 

Vboot (Bootstrap):
This
is the input bootstrap pin which gives the overvoltage necessary to drive all
the upper DMOS of the three half bridges.

Vs (Input Supply
Voltage Pins): These are the two input supply voltage pins. The
unregulated input DC voltage can range from 7V to 52V.

SENSE1, SENSE2: SENSE1
is the common source of the lower DMOS of the half bridge 1 and 2. SENSE2 is
the source of the lower DMOS of the half bridge 3. Each of these pins can
handle a current of 5A. A resistance, Rsense, connected to these pins provides
feedback for motor current control.

OLIMEXINO-32U4 development board

Arduino
is an open-source electronics prototyping platform, designed to make the
process of using electronics in multidisciplinary projects easily accessible.
The hardware consists of a simple open hardware design for the Arduino board
with an Atmel AVR processor and on-board I/O support. The software consists of
a standard programming language and the boot loader that runs on the board.

Arduino
hardware is programmed using a Wiring-based language (syntax + libraries),
similar to C++ with some simplifications and modifications, and a
Processing-based Integrated Development Environment (IDE).

 

Microcontroller
characteristics in Olimexino:

These
are the main characteristics of the olimexino microcontroller.


High Performance, Low Power AVR® 8-Bit Microcontroller


Advanced RISC Architecture


135 Powerful Instructions – Most Single Clock Cycle Execution


32×8 General Purpose Working Registers


Non-volatile Program and Data Memories


32K Bytes of In-System Self-Programmable Flash


2.5K Bytes Internal SRAM


1K Bytes Internal EEPROM


Four 8-bit PWM Channels


Four PWM Channels with Programmable Resolution from 2 to 16 Bits


Six PWM Channels for High Speed Operation, with Programmable Resolution from 2
to 11    Bits.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.IMPLEMENTATION

 

The flowchart for the control of the
bldc motor in Arduino