Transcript AEROBOTICS AEROBOTICS

AEROBOTICS
Tutorial
Introduction
AEROBOTICS is an event which adds a vertical
dimension to Robotics, making it all the more
adventurous and challenging.
The event aims to merge principles of aviation
with those of robotics.
AERO + robotics= Aerobotics
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TUTORIAL
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Arena
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Arena – various zones
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Hover-Craft
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HOVERCRAFT
MATERIAL
THRUST AND AIR CUSHION
TORQUE & WEIGHT BALANCE
DRIFTING & ROTATION
NAVIGATION
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Another possible way by using a rudder……
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Material
• Considering the fact that the vehicle should be air
borne it has to be light
• Material should have good resistance to bending
moments
• The Material that can be considered to build the
chassis could be
-High/Medium Density Foam, depron
-Balsa Wood
• Cost of the material under consideration
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Thrust and Air cushion
• The thrust to be provided depends on the weight of
the Aerobot.
• The static thrust of the motor can be lesser than the
weight of the Aerobot. Primary importance is
maintaining a good air-cushion to make the vehicle
float.
• This thrust can be provided by
-Standard RC Brushless Motors
-Duct-fans
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Duct Fan
• Control by PWM
• Simple DC Motor
• High Power Requirements
• Requires Large Current rating IC to
control it. Relays can also be used.
• Cost
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Torque & Weight balance
Weight Distribution
THRUST
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Placement
• Placement of the components decides CG of the
vehicle
• The CG should be perfectly aligned with the Thrust
line
• Since the system is afloat it will experience some
rogue torque caused by this misalignment of
components
• Too many actuators may also provide torque and add
to the instability
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Placement
Instability
Moment
Imbalance
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Drifting & Rotation
• The system has an inherent property of drifting
• This can only be controlled effectively by a good
mechanical design of the system
• Not all defects in the design can be countered by a
electronic system
• Rotation can however be regulated by an effective
Control system
• Rotation is due to the principle of Conservation of
angular momentum
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Navigation
• Horizontal thrust providers with control surfaces .
 Thrust provider can be fans or propellers
 For control surfaces we need to implement
aerodynamically effective solutions which would
be rudders
• Rotatable horizontal thrust providers.
• Can be implemented in either pusher or puller form
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Pusher
• The horizontal thrust is being provided by a
propeller placed at the rear end of the system
• This means the bot is being pushed horizontally
• There might be mismatch between the horizontal
thrust line and the bot’s horizontal symmetry axis
causing rotation and hence needs to be
implemented carefully.
CG
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Puller
• The horizontal thrust is being provided by a
propeller placed at the front end of the system
• This means the bot is being pulled horizontally
• The advantage in doing so is: in the case of
mismatch the bot will still continue moving forward
without rotation.
CG
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Li-Poly
POWER
ESC
SPECs
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Lithium Polymer Batteries
• This is the most preferred Power pack used
in RC Planes because of high power rating
and duration longing.
• Provides high current
• One pack of Lipo Battery contains a group
of cells in series, each cell can provide 3.7 V
• Standard Specifications are
3 cell pack : 11.2 V
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Battery Specifications
Factors to be considered before buying a
battery:
• Voltage
• Ampere Hour Rating
• No . Of Cells
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Electronics
Sensors
• IR sensor
• LDR (Light Dependent
Resistor)
• Ultrasound Sensor
(optional)
Processor
• Atmega
• Arduino
• PIC
Actuator
• Fans
• Control
Surfaces
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Sensors
• Sensors are necessary to sense the lines on the
arena and the side barricades.
• The ideal sensors for this purpose will be IR sensors
though a variety of sensors can be used.
• IR sensors are cheap and decently reliable.
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Sensors
• Light Dependent Resistor (LDR) has a property
of changing its resistance when illuminated
with light.
• When placed in dark it has a very high
resistance. Resistance drops dramatically
when light falls on it.
• It can be used to detect if the bulb is ON or
OFF.
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LDR Sensor Circuit
• In poor light conditions, Resistance of LDR is large and
hence more potential drop. This increases the voltage at 3
more than that at 2.
• Output voltage of the op-amp is HIGH and LED across 1 and 4
glows.
• In bright light conditions due to lesser potential drop across
LDR, output of op-amp would be LOW. LED across 8 and 1
glows.
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LDR Sensor Circuit
•The circuit switches LED on in the dark
•The LED remains off as long as LDR is illuminated
•The 10K potentiometer shown can be used to adjust
the sensitivity(calibration) of the sensor circuit
•Transistor can be replaced with an op-amp as a
comparator which was shown in the previous slide.
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Sensors
• Ultra Sound Sensors can also be used to detect the
walls on the sides.
These are costlier than IR but more reliable.
• The major challenge lies in placing the Optimal
number of sensors in the right position
• In the case when IR sensors are affected by the
ambient light interference then TSOP sensors can be
used.
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RF Communication
• RF Communication can be used for controlling the
hovercraft wirelessly.
Methods to
employ RF
Communication
RF Module
Hacking open a
RF toy car
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RF Module
Transmitter
Receiver
• It consists of two parts
• Transmitter
• Receiver
• The transmitter should be given serial data as input,
which is received by the receiver
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RF Module
We strongly recommend that you go through the
following links:http://extremeelectronics.co.in/rf/rf-communicationbetween-microcontrollers-part-i/
http://extremeelectronics.co.in/avr-tutorials/rfcommunication-between-microcontrollers-part-ii/
http://extremeelectronics.co.in/avr-tutorials/rfcommunication-between-microcontrollers-%e2%80%93part-iii/
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Hacking open a toy car
• A cheap 4 channel RF controlled car maybe
hacked open and used
• The channels are independent so all the four
channels can be directly used for controlling four
movements of the hovercraft.
•Since the channels are independent, upto 16
unique controls can be generated using various
combinations of the channels if required.
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Processors
• For onboard processing several processors are
available in the market like
 microcontroller
 Arduino board
 Any other development board
• An important specification of microcontroller is that it
should have many PWM channels.
• Development boards like Arduino Board provide an
user friendly interface but it’s costlier than spare
microcontroller.
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Brushless Motors
Out runners
High RPM
Power Requirement
ESC (Electronic Speed Controller)
Control is via PWM (Pulse Width Modulation),
following certain specifications
 Time Period = 20ms
 On time = 1 ms – 2 ms
• Cost
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Interfacing motor with microcontroller
Processor
ESC
Motor
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Pulse Width Modulation
• PWM is used to control the speed of the
motor
• This is done by controlling the ON time of
the rectangular Voltage signal given to the
motor
Processor
ESC
Motor Driver
Motor
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Motor Drivers
• The current required to drive any motor is very high
• Hence an appropriate motor driver is required
For example
 L293D : max rating 1 amp
 L298 : max rating 2 amp
 Relays for high current duct fan.
• The current by them may not be sufficient hence in
such a case high Power Transistors can also be
used.
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Problems that might surface
Please keep the following aspects in mind :-
• Hovercraft may drift outward at curves.
• Natural tendency of the hovercraft to drift and rotate
• Sufficient momentum might be required to climb the
ramp
• At the Y junction the hovercraft may tend to turn in one
direction preferentially because of the angular
momentum of the lift fan.
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Safety Issues
• Consider your own safety.
• Work carefully with propellers and brushless
motors. Fix the motors properly on the chassis.
• Be careful with LiPo, both while charging and
working. Use according to specification by the
manufacturer.
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Video links
The following are some videos of RC hovercrafts
that may be useful for you in building your own
hovercraft:-
• http://www.youtube.com/watch?v=y_tuFKtRSbs
• http://www.youtube.com/watch?v=75xR_UgpUk&feature=related
• http://www.youtube.com/watch?v=s1R4G9rwiP0
&NR=1
• http://www.youtube.com/watch?v=AFFXfjWW0F
k&feature=related
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