autonomous flying object

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AUTONOMOUS FLYING OBJECT G.KARTHIK J.KARTHICK Mail id: [email protected] Ph: 9047888158, 9677151653 Abstract The purpose of this paper is to design an Autonomous Flying Quad copter, which will be capable of flying in a controlled manner. The principle behind the working of this Quad copter is the principle of quad-rotor flying objects. The motors used here is brushless dc motor which makes the propellers rotate. The Quad copter will lift itself off the ground and then use controlled flight mechanism to fly across definite path and after executing its task it will land. All this will be done by the copter itself without using any external remote control device i.e., it will be completely autonomous. Hence in this paper we have included a microcontroller which will control the copter. In the case of indoor usage of this robot it is not a matter, but when it comes to the outdoor usage of this quad copter there will be the wind which will affect the movement of the copter. So for this purpose a GPS based system will be used to give this plate form its navigation abilities. Including GPS will solve our problems in flight due to disturbance caused by winds as it has to reach our desired coordinates. It should be able to move around from one specified point to other in open environment up to the accuracy constrained by the GPS device. A GPS will be attached to the plate form which specifies the coordinates of location where it will move. So there is another job to program the GPS hardware such that it directs the quad copter in the right direction. Such robots are useful in a broad range of surveillance, security, and military applications. So basically we are going to design a microcontroller based embedded system application. I. INTRODUCTION In this paper we will be designing an autonomous flying quad copter, which will be capable of flying in a controlled manner. It will lift itself off the ground and then use controlled flight mechanism to fly across define path and after executing its task it will land. All this will be done by the copter itself without using any external remote control device i.e., it will be completely autonomous. So basically we are going to design a microcontroller based embedded system application. The quad copter will be capable of flying autonomously and will not require any human assistance. A. Innovative Aspects

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Page 1: AUTONOMOUS FLYING OBJECT

AUTONOMOUS FLYING OBJECTG.KARTHIKJ.KARTHICK

Mail id: [email protected]: 9047888158, 9677151653

Abstract

The purpose of this paper is to design an Autonomous Flying Quad copter, which will be capable of flying in a controlled manner. The principle behind the working of this Quad copter is the principle of quad-rotor flying objects. The motors used here is brushless dc motor which makes the propellers rotate. The Quad copter will lift itself off the ground and then use controlled flight mechanism to fly across definite path and after executing its task it will land. All this will be done by the copteritself without using any external remote control device i.e., it will be completely autonomous. Hence in this paper we have included a microcontroller which will control the copter. In the case of indoor usage of this robot it is not a matter, but when it comes to the outdoor usage of this quad copter there will be the wind which will affect the movement of the copter. So for this purpose a GPS based system will be used to give this plate form its navigation abilities. Including GPS will solve our problems in flight due to disturbance caused by winds as it has to reach our desired coordinates. It should be able to move around from one specified point to other in open environment up to the accuracy constrained by the GPS device. A GPS will be attached to the plate form which specifies the coordinates of location where it will move. So there is another job to program the GPS hardware such that it directs the quad copter in the right direction.Such robots are useful in a broad range of surveillance, security, and military applications. So basically we are going to design a microcontroller based embedded system application.

I. INTRODUCTIONIn this paper we will be designing an autonomous flying quad copter, which will be capable of flying in a controlled manner. It will lift itself off the ground and then use controlled flight mechanism to fly across define path and after executing its task it will land. All this will be done by

the copter itself without using any external remote control device i.e., it will be completely autonomous. So basically we are going to design a microcontroller based embedded system application. The quad copter will be capable of flying autonomously and will not require any human assistance.

A. Innovative Aspects It’s functionality will be completely controlled by theembedded system that is designed which will make use of GPS (global positioning system) to obtain the desired features.The innovation in this autonomous flight feature is thatmost of the currently designed and commercially available systems need a remote control or some such controlling mechanism and none is completely autonomous.

B. Controlled Flight Quad rotors are classified as rotorcraft because their lift is derived from four rotors. Each rotor produces both a thrust and torque about its center of rotation, as well as a drag force opposite to the vehicle's direction of flight. Control of vehicle motion can be achieved by varying the speed of each rotor to change the thrust and torque. If all rotors are spinning at the same angular velocity, with rotors one and three rotating clockwise and rotors two and four counter clockwise, the net aerodynamic torque, and hence the angular acceleration about the axis is exactly zero, which implies that the stabilizing rotor of conventional helicopters is not needed.

II. PRINCIPLE OF OPERATIONThe Quad-rotor Flying Object (QFO) is a flying platform that uses four rotors. Each of the four rotors delivers an individually controllable amount of thrust. The rotors are positioned at the corners of a square. Any two adjacent rotors are contra-rotating.The QFO in this case is small, electrically powered, and controls individual rotor thrusts by varying the speed oftheir electric motors, rather than blade-pitch. This allows for the use of fixed-pitch propellers.

A. The QFO As A Helicopter A QFO’s functionality is similar to that of a conventional helicopter. It can hover and exhibit the same basic motions. This QFO uses four simple fixed propellers in place of the more complicated main rotor of a conventional helicopter.

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According to the limits imposed by momentum theory, QFOs can achieve the same efficiency as normal helicopters. There may or may not be other limitations that prevent this.

Like a conventional helicopter, the effects of actuation on system outputs in the QFO are highly inter-coupled. Furthermore, if rotor thrust is controlled by varying rotor speed (as opposed to pitch), the rotational inertias of therotors introduce additional lag dynamics in pitch and roll. This makes the QFO more difficult to control than aconventional helicopter, necessitating more automatic assistance. The major components with which the AFO can be designed are as follows:Brushless D.C MotorMicrocontrollerGPS (Global Positioning System)

III. BRUSHLESS D.C MOTOR AND CONTROLLER:

Brushless dc servo motors resemble a dc shunt motor turned inside out. Dc servo motors feature permanent magnets, located on the rotor, or a wound rotor excited by dc voltage through slip rings, requires that the flux created by the current carrying conductors in the stator rotate around the inside of the stator in order to achieve servo motor action. The servo motor features a rotating field is obtained by placing three stator windings around the interior of the stator punching. The windings are then interconnected so that introducing a three-phase excitation voltage to the three stator windings (which are separated by 120 electrical degrees) produces a rotating magnetic field. Brushless dc servo motor construction speeds heat dissipation and reduces rotor inertia.

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Some of the benefits of using BL DC motor are:

Internal Permanent Magnet (IPM) rotor design to avoid the surface mount magnets disadvantaged.

Patented rotor structure to have super low cogging torque performance for IPM servomotor.

No skewed slot on stator and rotor, it can increase reliabilities and reduce product costs.

Energy efficiency motor adopts the high magnetic energy permanent magnet NdFeB to have high power and torque density, and small size structure.

Electrical commutation can perform low noise, low EMI and no brush maintenance.

Power and torque density are much higher than the conventional motors.

Without mechanical commutation, motor speed can be over 10,000 rpm.

The innovating structure has an excellent feature in energy saving during heavy-load operation, and high torque at low speed driving.

The high efficiency range is much widerthan conventional motors.

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The speed of the motors can be controlled by using H-bridge for all the 4 motors. Standard Servo motors are built with NTC thermistor for motor temperature feedback. The speed control of the BLDC motors can also be obtained by using PWM techniques and also by using the controllers.

BL DC Motor and Controller SelectionSo after understanding how BL DC motor works, we selected one of the available BL DC motors.The 10A controller we use with the motor generatesthe 3 phase sinusoidal signal required for the motor aftergetting an input pulse. We select 11.1volt mode for thecontroller by removing its 2/3 batteries connector. (Highervoltage means higher rpm and maximum lift) Controller needs to be started with a pulse of 1msec at 100Hz. It generates 5 tones to indicate its initiation. After the startup controller is ready to receive signal to start the motor. So a signal of 1msec to 2msec is given to the controller and motor starts rotating. 1msec pulse means the slowest rotation while 2msec pulse means maximum rotation. Current demand ofthe motor also increases with the speed of the motor if the propeller is attached to the motor. Without the propeller the motor only draws a fixed amount of 1A current. At maximum speed motor and the controller both operate at 10A. At this huge amount of current motor and the controller both start to heat up very fast and after about 10sec the controller automatically switches the motor off. Controller also switches the motor off if the motor tries to draw current larger than 10A. So controller provides the protection to the motor.

IV. MICROCONTROLLER

The PIC architecture has a number of new features

including:

The highest execution speed 80 MIPS

(90+ Dhrystone MIPS @ 80 MHz)

The largest flash memory: 512 kByte

One instruction per clock cycle execution

The first cached processor allows execution from

RAM

Full Speed Host/Dual Role and OTG USB

capabilities

Real-time trace

The microcontroller is programmed such that it rotates the rotor in the desired speed so as to attain the precision. If we use this AFO indoor then we don’t need a GPS system for tracking the direction. But for outdoor use direction is important because of the wind factor so we have to use a GPS module so as to get the copter in the correct direction. Furthermore high precision can also be obtained by interfacing the GPS module with the microcontroller.In the case of using a GPS module the programming of the microcontroller is to be done in such a way that the BLDC motors run as per the directions obtained by the GPS.This microcontroller is programmed to obtain the data from the GPS system and accordingly the motor speed is controlled for every motor separately. A UART is used to interface the GPS module with the microcontroller. Also the

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feedback from the four motors is obtained with which the

current position is calculated and accordingly the nextcommand is given. The block diagram of the PIC microcontroller is shown above.

V. GLOBAL POSITIONING SYSTEM (GPS): The Global Positioning System (GPS) is a U.S. space-based global navigation satellite system. It provides reliable positioning, navigation, and timing services to worldwideusers on a continuous basis in all weather, day and night, anywhere on or near the Earth which has an unobstructed view of four or more GPS satellites.GPS is made up of three segments: Space, Control and User.

The Space Segment is composed of 24 to 32 satellites in Medium Earth Orbit and also includes the boosters required to launch them into orbit. The Control Segment is composed of a Master Control Station, an Alternate Master Control Station, and a host of dedicated and shared Ground Antennas and Monitor Stations. The User Segment is composed of hundreds of thousands of U.S. and allied military users of the secure GPS Precise Positioning Service, and tens of millions of civil, commercial and scientific users of the Standard Positioning Service. GPS satellites broadcast signals from

space that GPS receivers use to provide three dimensional location (latitude, longitude, and altitude) plus precise time.

There are four basic functions of GPS.

Position and coordinates. The distance and direction between any two

waypoints, or a position and a waypoint. Travel progress reports. Accurate time measurement.

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A.

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Calculation Of Position:

The receiver utilizes the messages it receives to determine the transit time of each message and computes the distances to each satellite. These distances along with the satellites' locations are used with the possible aid of trilateration to compute the position of the receiver. This position is then displayed, perhaps with a moving map display or latitude and longitude; elevation information may be included.

1. Go to: A direct path to a selected destination (waypoint, city, address and etc.).

2. Track: A previous path of travel that has been stored (logged) in the eTrex Legend. A track allows you to repeat a path or return to our starting point on the same path using the GPS Track Back feature.

3. Route: A path to a destination consisting of intermediate stops along the way (waypoints, cities, highway exists, points of interest, intersection, etc.).

The defining of waypoints is necessary to save the points from which we want our Autonomous flying object to pass through. Route is basically collection of waypoints.The waypoint can be marked if we stay stick button of GPS pressed for 2 seconds while it is showing your current location. We marked four waypoints in each corner of ground near NBS, the next step is to arrange these waypoints in a order in which we want to perform the Navigation.

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N ow that the current heading of the airplane and the next waypoint are known, we can discern which way and how much the aircraft should turn in order to hit the next way point. For example, the figure below shows one scenario given the waypoint heading angle and the true course angle. Intuitively, it is obvious that the aircraft should turn right to head towards the next waypoint.

The easiest, but definitely least effective, way of coding this algorithm is to say that if the aircraft heading is less than the waypoint heading, turn right. Otherwise turn left. However, this can be very inefficient in certain instances. For example, if the waypoint is just to the left of the North direction and you are heading a little right of North, the plane should turn

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slightly left to hit the waypoint. However, with the above algorithm the plane will get to the waypoint, but not beforeflying in a complete circle (well almost). This scenario is demonstrated in the graphic below

B. A Basic GPS Navigation Exercise:

The next step is to navigate our self through the Route which we created. The navigation page shows the rotating compass ring that shows our current course over ground and abearing pointer indicates the direction in which we should move to reach the nearest waypoint. The navigation page of GPS is shown below.

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We move from first waypoint to last waypoint and the bearing pointer guided us in which direction we should go to reach the next way point and finally the destination.

C. GPS Interfacing With Microcontroller:

To interface GPS with microcontroller, we have to make RS-232 communication of GPS compatible with microcontroller for which we need a level shifter as well as inverter to convert the levels to TTL.Standard serial interfacing of microcontroller (TTL) with PC or any RS232C Standard device requires TTL to RS232 Level converter. A MAX232 is used for this purpose. It provides 2-channel RS232C port and requires external 10uF capacitors. The driver requires a single supply of +5V.

As we needed the serial port for both GPS as well as ISP, therefore we use one DB9 connector in parallel to ISP as well as microcontroller using four DIP switches.

D. Comparison Of Current And Waypoint Heading:

After decoding the RMB and RMC messages we have both true and next waypoint heading, hence the next step is to compare these two heading and then decide whether to turn right or left. We have to write a code for this purpose.

VI. SYSTEM ARCHITECTUREThe whole system can be given by means of architecture which will depict the components used. There is a controller board and a driver board. The driver board is connected to the BLDC motors, hence it controls the rotor movement. The controller will give the commands to the driver board and it will control the BLDC motors. The controller gets the data from the GPS receiver system and also the feedback from the motor and accordingly it will drive the driver circuit. The speed and position commands are fed to the driver board.

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The final model of the copter is as shown.

The schematic diagram is shown.

The copter as shown has four propellers. Each of these is connected to an individual brushless D.C motor with the shaft of the motor pointing upwards. The microcontroller board is placed on the mica which forms the body of the AFO.

Suppose if the copter is to be lifted then the controller will give the command to the driver and the driver board will make all the four rotors run in such a way that the opposite rotors rotate in the same direction. Thus equilibrium is achieved in this case and the copter will start to fly. Now if the copter has to be moved to the right then the thrust exerted by the propeller at the right should be less compared to that of the left. Hence the program is done in such a way that the speed of the motor in the right is less than that of the left. By this way we can achieve the right movement.

A. Achieving Balance And Motor Speed Control Sum of all forces and torques should be zero for balance. Centre of gravity below the aerodynamic centre of the craft (through placing the batteries below the intersection of the airframe), the inertia due to the mass of the batteries resists both pitch and roll.

This is the equation for lift.

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VII. APPLICATIONS

• Such aircrafts are useful in a broad range of surveillance, security, and military applications• They can carry out complex missions from take off to landing completely autonomously. Aerial filming and photography• Video (on board recording and wireless air to groundrecording)• Feature movies, documentaries, animal.

A. Engineering

Nuclear radiation areas Burn-off towers Railway Power lines filming Real estate sales, documenting development of

construction sites Pipelines Off shore maintenance related control Underneath bridges

B. Civil

Traffic control Forest fire detection & control Avalanche monitoring

C. Military And Law Enforcement

Border patrol, crowd and riot control, Infrared detection Mine sweeping, scouting and preventive triggering

and path finding, Carrying of tactical equipment

D. Rescue Operations

Dropping equipment: live vests, inflatable boats, rescue lines over water, buildings or on mountains

E. Aerial Transports

Bring loads to hard to reach places (behind enemy lines, on top of buildings, across a river etc.)

Geological and ecological surveys, treetops, forest control, agricultural, pollution detection.

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REFERENCES

http://www8.garmin.com/manuals/eTrexLegend_OwnersManual.pdf

http://www.gps-practice-and-fun.com/gps-exercises.html

http://www.pages.drexel.edu/~weg22/gpsMagpie/gpsFixedWing.html

http://knr.pb.edu.pl/index.php?option=com_content&view=article&id=51:qaudrotor&catid=28:projektywbudowie&Itemd=44

http://www.verhagenx2.com/solutionsinfligh.html

http://en.wikipedia.org/wiki/Global_Positioning_System

http://sodoityourself.com/max232-serial-level-converter/

http://www.gpsinformation.org/dale/nmea.htm#RMB

https://www.courses.psu.edu/aersp/aersp055_r81/satellites/gps_details.html

http://aprs.gids.nl/nmea/

http://extremeelectronics.co.in/avr-tutorials/rs232-communication-the-level-conversion/http://www.weethet.nl/english/gps_garmin_etrex_to_rs232.php

http://www.ikalogic.com/isp.php

http://www.freewebs.com/maheshwankhede/rs232.html

http://www.pages.drexel.edu/~weg22/gpsEmaxx/gpsEmaxx.html

http://www.kowoma.de/en/gps/positioning.htm

http://ufo.eterrorist.org/blog/ufo.got.net/blog/index.html#motoresc