Quadcopter in Pakistan

quadcopter in pakistan

 

 

Quadcopter in Pakistan

The  helicopter  is  one  of  the  most  complex  flying  machines  due  to  its  versatility  and
maneuverability  to  perform  many  types  of  tasks.  Classical  helicopters  are  usually
equipped with a main rotor and a tail rotor. However, other types exist which use a twin
rotor.  Our  specific  project  is  concerned  with  the  design  and  control  of  a  miniature
rotorcraft, known as a quad-rotor helicopter [1]
. Quad  rotors  are  symmetrical  vehicles  with  four  equally  sized  rotors  at  the  end  of  four
equal  length  rods.  Unlike  their  counter  parts,  quad  rotors  make  use  of  multiple  rotors
allowing  for  a  greater  amount  of  thrust  and  consequently  a  greater  amount  of
maneuverability.
Fixed-wing  vehicles  have  long-range  since  they  are  energy  efficient,  but  they  lack  the
maneuverability required for many UAV tasks. For example, Blimps are easy to control
when there are fewer disturbances like wind, and lift comes from  natural  buoyancy, but
their  maneuverability  is  limited.  The  helicopters  have  advantages  over  conventional
fixed-wing aircraft and blimps on surveillance and inspection tasks, since they can take-off  and  land  in  limited  space  and  can  easily  hover  above  targets.  Moreover,  helicopters
have the  advantage of  maneuverability. Unfortunately, this  advantage makes helicopters
very hard to control, requiring sophisticated sensors and fast on-board computation [2]
.
Unmanned  aerial  vehicles  are  aircrafts  capable  of  flight  without  an  on-board  operator.
Such vehicles can be controlled remotely by an operator on the ground, or autonomously
via  a  pre-programmed  flight  path.    Today,  unmanned  aerial  vehicles  (UAVs)  are  an
important  part  of  scientific  study  both  in  military  and  space  studies.  As  a  substitute  for
human piloted vehicles they are advantageous to protect human life in multiple dangerous
environments.  Their  reliabilities  in  tough  circumstances  are  much  higher  than  their
counter parts.
UAVs  can  be  classified  into  two  major  groups:  heavier-than-air  and  lighter-than-air.
These  two  groups  self  divide  in  many  other  that  classify  aircrafts  according  to
motorization,  type  of  liftoff  and  many  other  parameters.  Vertical  Take-Off  and  Landing
(VTOL) UAVs like quadrotors have several advantages over fixed-wing airplanes. They
can move in any direction and are capable of hovering and fly at low speeds. In addition,
the  VTOL  capability  allows  deployment  in  almost  any  terrain  while  fixed-wing  aircraft
require a prepared airstrip for takeoff and landing. Given these characteristics, quadrotors
can  be  used  in  search  and  rescue  missions,  meteorology,  penetration  of  hazardous
environments (e.g. exploration of other planets) and other applications suited for such an
aircraft.  Also,  they  are  playing  an  important  role  in  research  areas  like  control
engineering, where they serve as prototypes for real life applications.
The design of unmanned aerial vehicles involves the integration of various steps such as
design,  selection  of  sensors  and  developing  controllers.  These  steps  can  not  be  treated
separately.  For  example,  one  can  not  design  a  vehicle  without  considering  the  sensory
input or the controllers that will be implemented, as these steps are closely related to each
other  [2]
.  Stabilizing  and  guidance  of  these  hovering  platforms  are  common  and  basic
tasks that have to be accomplished before assigning a mission to the vehicle.

Because of the ambitious nature of project goals, development of the UAV can be easily 
divided into five major stages:  

•  Vehicle conceptual design  
•  Analysis and component-level design and selection  
•  Fabrication, assembly, hardware testing, and re-design  
•  Simulation development and verification  
•  Control and estimation development for future implementation 

Though  these  five  stages  occasionally  overlapped  and  sometimes  interfered  with  one
another, they can be discussed independently.
Among  the specific significant engineering challenges  that  researchers are focusing on
for  the  development  of  successful  UAV  are: it should be  ultra-compact, lightweight,
high-power    and    high-energy-density    propulsion    and    power    sources;  untraditional
concepts    for    lift    generation;    flight    stabilization    and    control    for  aerodynamic
environments    with    very    low    Reynolds    numbers;    secure,    low-power  onboard
electronic    processing    and    communications    with    sufficient    bandwidth    for  real-time
imaging;    micro-gyroscopes    and    inertial    measurement    units    (IMU)    and  very    small
onboard  guidance,  navigation,  and  geo-location  systems.  To be really useful, a UAV
needs  to  carry  a  short-range  day/night  area  imaging  system  with  a  sufficient  resolution.
The  system  must  feature  an  accurate  geo-location  capability.  A  sufficient  vehicle  range
and real-time communications are also desired.
With  the  advent  of  new  technologies  ranging  from  global  positioning  systems  to  faster,
smaller,  and  lighter  computer  processors,  there  has  been  a  surge  in  development  of
unmanned  vehicles.    Unmanned  and  autonomous  vehicles  are  currently  in  development
for use in air, over land, and in the water by both private and government agencies.

Definition and Basic Concepts OF QUADCOPTER

A  quadrotor,  or  quadrotor  helicopter,  is  an  aircraft  that  becomes  airborne  due  to  the  lift
force provided by four rotors usually mounted in cross configuration, hence its name. It is
an  entirely  different  vehicle  when  compared  with  a  helicopter,  mainly  due  to  the  way
both  are  controlled.  Helicopters  are  able  to  change  the  angle  of  attack  of  its  blades,
quadrotors cannot.
The  first  question  one  is  asked  about  the  quadrotor  is  how  it  stands  out  from  the
traditional one. Hence a short introduction about the quadrotor construction and steering
principle  is  necessary.  The  quadrotor  is  a  mechatronic  system  with  four  rotors  that
provide the lift and control. With respect to hover, the main difference is best explained
by  considering  how  the  helicopters  compensate  from  gyroscopic  torques.  Traditional
helicopters basically compensate from the torque generated by the main rotor through the
tail rotor. However the tail rotor compensation conducts a sideways displacement of the
helicopter, thus counter steering by tilting the main rotor blades is necessary. In this way
hover  is  an  ongoing  and  complex  process.  The  quadrotor  has  four  propellers  driven  by
four motors in a cross configuration which are fixed to a certain spin axis. The spinning
directions  of  the  rotors  are  set  in  pairs  to  balance  the  torques,  therefore  eliminating  the
need for a tail rotor. While the front and the rear motor rotate counter-clockwise, the left
and  the  right  motor  rotate  clockwise,  as  long  as  the  rotors  rotate  at  the  same  speed  the
gyroscopic  effects  are  nearly  eliminated  and  the  quad  rotor  essentially  hovers,  this
proving  to  be  a  less  complex  maneuver  to  retain.  With  regard  to  application  and
functionality  the  quad  rotor  helicopter  has  the  same  immediate  advantages  as  the
traditional  helicopter.  One  additional  advantage  of  the  quad  rotor  compared  to  a
traditional  helicopter  is  the  simplified  rotor  mechanics.    By  varying  the  speed  of  the
single  motors,  the  lift  force  can  be  changed  and  vertical  and/or  lateral  motion  can  be
created.  However  a  number  of  issues  especially  regarding  the  mechanical  construction
prove  to  be  interesting  from  a  control  perspective  point  of  view.  The  first  and  foremost
issue  concerns  the  modeling  of  the  quad  rotor  as  this  proves  to  be  a  different  and  more
feasible task.

Quad Rotor Operation

Quadrotor is an under-actuated, dynamic vehicle with four input forces and six degrees of
freedom.  Unlike  regular  helicopters  that  have  variable  pitch  angle  rotors,  a  quadrotor
helicopter  has  four  fixed-pitch  angle  rotors.  The  quadrotor  is  very  well  modeled  with  a
four rotors in a cross configuration. This cross structure is quite thin and light, however it
shows  robustness  by  linking  mechanically  the  motors  (which  are  heavier  than  the
structure).  Each  propeller  is  connected  to  the  motor  through  the  electronic  speed
controller. All the propellers axes of rotation are fixed and parallel. Furthermore, their air
flow  points  downwards  (to  get  an  upward  lift).  These  considerations  point  out  that  the
structure is quite rigid and the only things that can vary are the propeller speeds.

Each rotor in a quad rotor is responsible for a certain amount of thrust and torque about
its  center of  rotation, as  well as  for  a  drag force  opposite  to  the rotorcraft’s  direction of
flight.  These  props  would  provide  the  thrust  necessary  to  counter  gravity  while  also
providing sufficient residual thrust for control of roll and pitch (and subsequently forward
and lateral velocity),  yaw, and vertical velocity.   The basic  motions of a  Quad rotor are
generated by varying the rotor speeds of all four rotors, thereby changing the lift forces.
The  helicopter  tilts  towards  the  direction  of  the  slow  spinning  rotor,  which  enables
acceleration  along  that  direction.  Therefore,  control  of  the  tilt  angles  and  the  motion  of
the helicopter are closely related and estimation of orientation (roll and pitch) is critical.
As spinning directions of the rotors are set to balance the moments. This principle is used
to  produce  the  desired  yaw  motions.  In  order  to  define  an  aircraft’s  orientation  (or
attitude)  around  its  center  of  mass,  aerospace  engineers  usually  define  three  dynamic
parameters, the angles of yaw, pitch and roll. This is very useful because the forces used
to control the  aircraft act around its center of mass, causing it  to  pitch, roll or  yaw. The
generalized coordinates for a rotorcraft are:
q=(x, y, z, θ, φ, ψ)                (1.1)
Where (x, y, z) denote the position of the center of mass of the rotorcraft relative to the
frame, and (θ, φ, ψ) are the three Euler angles which represent the orientation of the craft
[3]
. Figure  shows the yaw, pitch and roll rotations of a quadrotor.

 

 

 

 

Quadcopter in Pakistan

 

 

 

 

After successful implementation of various stages we reached the last and final stage it is//
hardware implementation. It is further divided in two categories.
1.  Mechanical work
2.  Electronic work

Mechanical work OF QUADCOPTER

After the airframe was designed and the components were purchased, we needed to place
the  components  appropriately  on  the  airframe.  First  of  all,  the  circuit  board,  which
consists of the microcontroller and other circuit elements, was placed on top at the center
of  the  circular  cage  like  structure.  The  battery  pack  was  placed  underneath  the  circuit
board  inside  the  circular  cage  like  structure.  Each  of  the  4  Electronic  Speed  Controllers
(ESCs)  were  placed  on  each  of  the  arms  of  the  airframe,  with  their  inputs  commonly
connected to the battery pack, and their 3 outputs are connected to the 3 input poles of the
motor. Each of the four motors are placed at the ends of each of the arms, with their shaft
directly inline with the center of the circular space designed for the circular motor mount.
As for the propellers, the tractor propellers  were placed on the shafts  of  the motors that
operated  in  the  clockwise  direction.  Similarly,  the  pusher  propellers  were  placed  on  the
shafts of the motors that operated in the counterclockwise direction. Attention should be
given to assembling of parts;  there should be no loose components as they  will  produce
vibrations making quadrotor unstable. Some important points are given below in detail as
they need special attention. After assembling of parts the figure of our quadrotor is shown
below.

Motor Alignment  OF QUUADCOPTER

The act of assembling the motor to the frame is extremely difficult due to the fact that the
holes  needed  to  be  drilled  to  within  +/-  .1o
  of  each  other.  Any  successful  flying  device
must be perfectly balanced, and this is very prevalent when dealing with a quad rotor. In
order to achieve a balanced vertical flight, the group needed to be certain that the motors
were  perfectly  straight.  If  the  motors  were  not  perfectly  aligned,  achieving  a  balanced,
smooth flight would be nearly impossible. With this in mind, we devised a way to be sure
that all the motor were aligned correctly. By setting the frame of the quad rotor on a flat
surface, we used a T-square held against the motor. If the motors were directly against the
edge of the square, then the motor would be aligned in a 90 degree angle.

Propeller Balancing

Due  to  the  fact  that  the  propellers  are  operating  at  such  a  high  RPM,  it  is  crucial  to  the
quad  rotors  performance  that  the  propellers  are  balanced.  Although  theoretically  the
propellers are designed to have symmetric blades, in reality there are slight imperfections.
These imperfections cause the propellers to vibrate uncontrollably, making smooth flight
almost  impossible.  By  balancing  the  propellers,  vibrations  can  be  significantly  reduced.
The  group balanced  the propellers by  examining  the relative weight distribution of each
propeller. There are several types of commercially available propeller balancing devices,
but  a  similarly  effective  device  was  made.  The  method  used  consisted  of  attaching  the
propeller to a spindle held up between two blocks, allowing the propellers to rotate freely.
If  one  of  the  blades  is  heavier  than  the  other,  then  the  propeller  will  rotate  towards  the
heavier blade. In such a case, the blades trailing edge was sanded down to compensate for
the  mass  difference.  Once  the  blades  weights  were  evenly  distributed,  the  propeller
balanced horizontally.

Quad Rotor Balancing

The  quad  rotor,  which  includes  air  frame,  dc  motor,  electronic  speed  controller,
propellers,  batteries  and  electronic  circuits,  was  carefully  designed  and  assembled  with
the  idea  of  having  a  helicopter  which  is  as  close  to  perfect  in  terms  of  its  weight
distribution  throughout  the  entire  aircraft.  Achieving  a  steady  and  controllable  flight  is
almost  impossible  to  achieve  unless  the  aircraft  is  as  close  to  perfect  balance.    The
addition of the electronic components and battery onto the frame of the quad rotor leaves
its  weight  distribution  inconsistent  throughout.  As  a  result,  we  devised  a  way  to  make
sure that the frame is as balanced as possible.
The way to do this is by attaching a piece of string to the center of the hub and allowing
the quad rotor to float freely. If the weight is not evenly distributed, then the quad rotor
will lean towards the heaviest part. The battery packs, which are mounted in the centre of
air frame in cage like structure, were then adjusted to ensure the quadrotor was balanced
in the x and y axes.

 Electronics work OF QUADCOPTER

After describing the parts used in the construction of the quadrotor and their assembling,
it is important to mention how the electronic components are made to work. This section
describes  the  electronic  circuit;  a  block  diagram  of  the  electronic  design  is  shown  in
Figure  below.

 

 

 

 

 

One thought on “Quadcopter in Pakistan

  1. Kashif Bhi,
    Asslam-o-Aalikum,
    I need Quarcopter……….Pls. advise availability & price with its working life time also help in Solar Tracker “slew drive with DC motor” in single angle availability in Pakistan for machenical along with your “Tracking Electronic System” price as well.
    Jazak Allah
    +923037771900
    Faisalabad

Leave a Reply

Your email address will not be published. Required fields are marked *