Department Of Aerospace Electronic And Electrical Engineering

Published Date: 02 Nov 2017

UAVs (Unmanned Aerial Vehicles) are becoming increasingly important in the field of aeronautics, they are able to fly by themselves with autonomous operation capabilities. UAVs are very important in military projects and increasingly in civil applications.

UAVs can advantage manned aircrafts; risks and costs can be minimized using UAVs since they need no crew and their construction, operation and maintenance costs are comparatively lower.

I think the use of UAV can be very useful for the society nowadays and in the next future, because do not require putting the pilot’s live in risk and are becoming cheap. The use of UAVs has received an increasing amount of popularity due the advances in telecommunications systems and avionics. The advances in nanotechnology, lighter materials, power efficiency, aerodynamics and performance permits to build micro/mini UAVs.

The main idea of this project is investigate how to make a successful connection to a UAV and send flight information to the ground station with certain levels of security, speed and integrity. This is known as UAS (Unmanned Aerial System).

Project Objectives

The objective of this project is to provide a solution to make a successful connection to a UAV and send information with certain levels of security, codification, speed and integrity.

Focus

I think this project focus on the users of UAVs. These users can be a normal person who likes the RC, a company, and even a government or an army. The project can solve the telemetry problem with little resources.

Requirements

The requirements of the project are the follow:

Integral information transfer

Secure connection

Certain levels of quality: distance connection, speed, materials, duration of the device

Economical

Methodology

Theory

Telemetry system

Definition

Telemetry systems are used to transfer information of the measurement and evaluation. This information is collected by others systems and the telemetry system task is to send it to the main station.

These systems are very common in the industry. They can be founded in several areas such as defence, aerospace, automotive, medicine or agriculture. In the case of UAV, the telemetry systems are used to monitoring the common flight information:

Temperature

Pressure

Vibration

Acceleration

Telemetry system structure

The structure of a telemetry system is composed by a collection system (measure the information), a multiplex system and transmitter system.

(figure 1)

In the picture we can see the structure of the UAV telemetry system (part A). The other parts are the sent signal and the structure (part B) of the in land receiver system (part C).

Data transfer method: Bluetooth

In this section, we want to give a global view of what is Bluetooth, making a small introduction to basic level of operation and which is then also able to understand the concepts at hand TFC.

History of Bluetooth

The Bluetooth name is in honour of a tenth-century Danish king called Harald Blaatand, was king of Denmark between the years 940-981 AD. This king had some great communication skills that made him famous and which began the process of Christianization of the Viking society.

The story is relatively short Bluetooth. The first investigations were made by Ericsson Mobile Communications in 1994. This company promoted an initiative to study the viability of a radio interface between mobile phones and accessories, with the characteristic and condition that had a small low cost and consumption. Until then, communication technologies based on the cable functioned efficiently, however, its installation and configuration was quite difficult.

As Ericsson project progressed it drew interest from other manufacturers and then saw the wide range of possibilities that offered this technology, so in early 1998 he created the SIG (special interest group) which was formed by Ericsson, Nokia, IBM, Toshiba and Intel. Currently they have been adding other group firms as 3Com Corporation, Lucent Technologies, Microsoft Corporation, Motorola Inc and many more coming today to be composed of more than 2000 companies in the sector of computer and telecommunications.

The main purpose of the SIG is to establish a standard for aerial interface with control software, its purpose is to ensure the interoperability of different equipment from different manufacturers.

Definition

Bluetooth is a technology oriented wireless connectivity between disparate devices such as PCs, PDAs, mobile phones, appliances, etc.. In general, we can say that the possibilities can be considered infinite.

The Bluetooth, besides being a new technology, is also an open specification for wireless communication of voice and data. It is based on a radio link low-cost, short-range, which provides instantaneous connection (adhoc) for both mobile communications environments as static.

This technology has revolutionized the connectivity market, as it is able to communicate any device that meets the specifications of Bluetooth wireless.

The Bluetooth technology including hardware, software and interoperability requirements, so that their development has required the participation of the leading manufacturers in the sectors of telecommunications and informatics.

Reasons to use Bluetooth in this project

The main advantage of this technology is the wireless connectivity for all devices, but more to replace the wires; this technology provides a bridge between existing data networks.

The Bluetooth, being an open standard, aims to connect a wide range of device regardless of brand. Its main features are:

- Robustness.

- Low cost.

- The need for low power.

- Low complexity.

- It is a global standard.

How Bluetooth works

The Bluetooth works in the ISM (industrial, scientific and medical), with ranks between 2.4 GHz and 2.5 GHz except in some countries like France, Spain and Japan where there are certain restrictions. The ISM band is a band open worldwide which is license.

The transmit power is up to 100mW. The nominal distance the link goes from 10cm up to 10m, being able to reach 100m if enough power is increased.

When a Bluetooth device is within the coverage radius of another, they can create a link between them. Up to eight Bluetooth units can communicate with each other and form what is called a Piconet. Several Piconet form a Scatternet. In all Piconet can be only one master unit which is usually who initiates the connection, the other Bluetooth units are called slaves.

Each unit of the Piconet master and uses his native clock identity to stay in the channel jump. When the connection is established, the clock adds an adjustment to one's native clock of the slave unit to synchronize with the master's native clock. The native clock frequency remains constant, however the adjustments for the slave units to synchronize with the master are only valid for the duration of the connection.

Bluetooth module used

The Bluetooth module used is a serial 4 Pin Bluetooth RF Transceiver Module RS232 bought in Amazon.co.uk by the University for this concrete project.

The Bluetooth module meet the requirements for this project:

Qualified for bluetooth version 1.1.

RF Output Class 2.

Approved by ETSI and FCC.

Maximum transmission speed of 460kb / s.

I2C Interface.

Internal crystal oscillator.

HCI firmware included.

Connect ptp (point to point).

Supports Computers and peripherals.

Handsfree devices and accessories.

Access points

(figure 2)

Microcontroller: PIC18

The evolution of the electronic from the appearance of the integrated circuit has been constant. Today we find more and more complex devices located in increasingly smaller encapsulated, an example of this are the microcontrollers.

Definition

A microcontroller is an electronic device encapsulated in a chip, capable of running a program. The microcontroller together into one integrated:

Microprocessor.

Program memory.

Data memory.

Input / output.

In addition, also often have other special features like: serial, comparators, analog-digital converters, etc.. In the market there are a variety of microcontrollers different brands and features that can be used depending on the application to perform.

A microcontroller executes instructions. The instruction set is what we call program. The instructions are read from the program memory to run one after the other. The program memory contains the instructions that we want the microcontroller run.

Program a microcontroller is to introduce the program in the microcontroller memory. The instructions are simple operations like addition, subtraction, write to a port, enable a data bit, etc.. Through these basic instructions can perform more complex operations and thus reach the goal of the application.

(figure 3: microchip.com)

PIC184520

The microcontroller used for this project is PIC184520. This PIC family have 8-bit microprocessor.

The technical specifications are the follow:

(figure 4: microchip.com)

These specifications meet the requirements for this project.

USART

It is a peripheral for data transmission in serial format, transmission techniques using synchronous or asynchronous.

This peripheral is often confused with some of the communication standards that use for interconnection between data terminal equipment (DTE) and data circuit equipment (DCE) within these standards the most popular is the EIA-232, known well as RS-232, is used for the interconnection with other standards such as RS-485 and RS-422.

Their outputs are usually the type TTL, but now can also be found logic levels within the range of values ​​accepted by the IEEE standard for digital systems. Different devices to communicate through connecting wires are required for use, for example a MAX232 or MAX485 to adapt the voltage levels to those used by RS-232 or RS-485.

RS-232

RS-232 is a telecommunications standard for binary data between data terminal equipment and data circuit-terminating equipment. It is also used in control signal between these two terminals. It defines the timing and meaning of signals and type of connectors (pins)

‘RS232 is serial interface that means that data is transferred BIT by BIT at a time. Since data is transferred BIT by BIT so we need only a single wire two send data and another one to receive data. One more common wire (called GND) is required between two separate circuit to enable current flow. So a total of three wire are required for communication.’ (Extreme Electronics, 2013)

In this project is very important because is used to connect the Bluetooth module to the microcontroller.

Analysis of Problem

Design

The design of the UAV Telemetry System is explained in the following picture:

Macintosh HD:Users:Reimon:Documents:uav.png

The UAV Telemetry System is composed by the Microcontroller (PIC18) and the Bluetooth module. The microcontroller collect the information from the sensors (altitude, pressure, speed, acceleration, etc.) and send it periodically to the Bluetooth Module.

The Bluetooth module is linked to the ground station (PC, tablet, or other devices with Bluetooth connection), establish a connection and start to transfer the information.

This information is sent each period of time selected by the PIC programmer.

This design allows a good performance with low consumption of energy and offers a cheap solution. The microcontroller should have a port to communicate with the Bluetooth module. This module depends of the range and quality of the signal, and there are several choices in the market.

The Bluetooth offers a wireless connectivity for all device and provides a bridge between existing data networks. It is also a open standard and permit to connect a wide range of device regardless of brand. Others advantages are the low cost, the low power consumption, low complexity and the robustness.

Implementation

MPLAB

MPLAB IDE is a free editor, for Microchip brand products. This editor is modular, it allows selecting the various supported microcontrollers, and allows recording of these ICs directly to the programmer.

It is a program runs under Windows presents the classic bar program, menu, tool condition, etc.. The MPLAB ® environment has text editor, compiler and simulation (not real time).

After the compilation the MPLAB ® generated a file extension ".hex" which is completely understandable to the PIC. That is, it only remains to record the PIC through an interface such as Picstart Plus microchip programmer. Once this is complete, is fed to it and the program is already running.

The possibility of code in C has been a important point to choose this program. MPLAB translate the C code to assembler.

Hi-TECH Compiler

This project uses the several libraries from third-party programmers that use Hi-TECH compiler.

HI-TECH C compiler for PIC10/12/16 MCUs implements the optimizations of Omniscient Code Generationâ„¢ (OCG) - a whole-program compilation technology - to provide denser code and better performance for development on PIC10/12/16 MCUs.

The compiler can be downloaded in the following link:

http://www.htsoft.com/downloads/

There is a PRO trial version for 30 days. The PRO version optimizes the code up to 400%, but for this project is not mandatory.

USART library

The following explanation of the USART library (Extreme Electronics) is extracted from the web: http://extremeelectronics.co.in/ and the use for education is allowed.

This keeps the USART code separate from the application code. The same library can be used in many other project that requires USART communication. The functions available in the library are discussed below.

void USARTInit()

This function initializes the internal USART of the PIC18F4520 microcontroller. This must be called before data can be sent or received. Call it at the program startup.

Return Value: None

Parameters: None

void USARTWriteByte(char ch)

Writes a byte of data to the USART.

Return Value: None

Parameters: data to be sent.

Example:

USARTWriteByte('a');

Will send character 'a' to the serial port.

void USARTWriteString(const char *str)

This function will send a string of character to the serial port.

Return Value: None

Parameters: C Style NULL terminated string.

Example

USARTWriteString("Hello World !");

Will send the string "Hello World !" to the serial port. If you have Terminal Program Monitoring that port the message "Hello World !" will be displayed there.

void USARTWriteLine(const char *ln)

Same as the above function but after sending the string it takes the cursor to the beginning of the next line. So next string you send will be printed on new line. If you are working on a Linux based terminal it may now work! In Windows a new line is a CR/LF pair but in Linux it is different.

Return Value: None

Parameters: C Style NULL terminated string.

void USARTWriteInt(int val,unsigned char field_length)

This function is used for sending integer values. The second parameter field_length is the lenght of field. Integer can be printed in two ways. One is fixed field length and other is variable field length. In fixed field width you specify the width of field by the parameter field_length. In this case integer will always have this much digits. Leading zeros may be added. Say if you call

USARTWriteInt(99,4)

Then the width of the field will be constant i.e. 4 as passed. So the number will be printed like this

0099

On the other hand variable width integer printing prints as much digit as their are in the original number. So a call like this

USARTWriteInt(99,255); //255 stands for variable width

will print

99

Return Value: None

Parameters: val = 16 bit signed integer, field_length= width of field required or 255 for variable width.

unsigned char USARTReadByte()

Wait until a byte is received from USART/Serial Port and return the value read from the USART.

Return Value: Byte read from USART

Parameters:None

Example

char data;

data=USARTReadByte();

Now the variable data has the byte received from the USART

Testing and Results

Project Management

In this chapter, the project Gantt chart and the project outline is showed.

Project Schedule

The project Gantt Chart:

The project outline:

Critical Appraisal

Conclusions

Achievements

Recommendations for Future Work

Student Reflections