Path Following Robo Car

8/8/2019 Path Following Robo Car

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PATHFOLLOWING ROBOTIC CAR

ABSTRACT

The graphical user interface of the MATLAB

provides a way for the user to input the path that he

wants the robotic car to follow. MATLAB processes the

path by using the program written on MATLAB and

produces four signals for left, right ,forward and for

stopping the car. This is communicated to themicrocontroller on the vehicle part by using a serial

communication port and the microcontroller generates

the signal to drive the stepper motors and the robotic car

runs in the path drawn.

College of Engineering, Trivandrum



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INTRODUCTION

In a world where everything robotic is trying to

become more human-like, there is a need for making a robotic car which

follows any path the user defines for it. It will be better to have the user

predefine the path instead of always having to monitor the path.

The RC car is designed to follow a path drawn by

the user. The Control signals are transmitted according to a user defined

path with the help of MATLAB and Microcontroller. The robotic car can be

controlled from the MATLAB environment. The MATLAB signals are

serially transmitted to the Microcontroller using a serial interfacing

wireless module. Control of the wheels is done by Microcontroller. Thus the

car follows the path drawn by the user.

MATLAB is a numerical computing environment and

programming language. Maintained by The Math Works, MATLAB allows

easy matrix manipulation, plotting of functions and data, implementation ofalgorithms, creation of user interfaces, and interfacing with programs in

other languages.

The MATLAB sent the signals to the microcontroller and

proper controlling of the car was done so that it followed the path that was

drawn. . There are 2 control signals from the microcontroller was

transmitted to the receiver and then given to the motor driving circuit.The

Web Camera placed in front of the vehicle instantly catches all the images

in front of it .The final result acquired was an RC car that follows the userdefined path.



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DESIGN APPROACH

The Project was executed in 4 stages:-

1) MATLAB: - The path drawn by the user is read using MATLAB and

programming is done to generate the signals accordingly. Path is drawn using a

drawing tool (GIMP, Paint) which is read by MATLAB using its inbuilt functionimread.

2) Serial Communication: - The signals generate by the MATLAB is serially

communicated to the Microcontroller using RS 232 cable. Output signals from

MATLAB is sent in 8 bit frame format and a baud rate of 9600 based on serial

communication protocol.

3) Microcontroller: - Microcontroller programming is done to generate the control

signals provided to the motor driving circuit. RS232 serial communication portand Microcontroller 18F452 is interfaced using a MAX 232 for logic

conversion from CMOS to TTL.

4) Driving Circuit: - The stepper motor in the motor driving circuit picks up the

control signals and drives the wheels. Microcontroller output is three controlling

signals that are taken up by the interfacing module made up of TIP 122 and sent to the

motor driving circuit for driving the wheels.



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BLOCK DIAGRAM

TRANSMITTER PART



PCSerial port

Communic-

ation

module


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MOBILE PART



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CIRCUIT DIAGRAM

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Figure shows the block diagram of the

transmitter unit and mobile unit. In the Transmitter

unit consist of Pc, serial port and communication

module. In the mobile unit consists of Receiver part

of the communication module, Microcontroller and the

Interface unit. The block diagram also consists of web

camera and usb port.

This GUI file with the program to be

executed is opened by calling Pc used in the Transmitter

unit used for the creation of GUI file.the MATLAB file

car.m at the command prompt. Load loads the image on

the GUI window. Run command is used to execute the

program.The input at the GUI level is the filename The

graphical user interface of the MATLAB provides a way for

the user to input the path that he wants the robotic car to

follow of the path that the user has drawn. MATLAB

processes the path and produces four signals for left, right,forward and for stopping the car.The serial port interface forconnecting two devices is specified by the TIA/EIA-232C

Software serial port monitor, Com Rs232 sniffer with


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transmitted.

For an asynchronous system, the number of bits

transmitted per second must be known by the receiver. Since

the clock signal is not transmitted, the receiver needs to know

what clock frequency the transmitter is using so that it can use

the same.

The receiver also needs to know how many bits per word

the transmitter is using (in most cases we deal with 8-bit

words, but we will see cases where nine bits are transmitted

per word). And the receiver needs to know where the data

begins and where the data stops.Bluetooth wirelesstechnology is a short-range communications technology

intended to replace the cable connecting portable and/or fixed

devices while maintaining high levels of security.

The mobile unit consists of Receiver part of the

communication module and the it is followed by

microcontroller part. The Microcontroller part will gives signals

to the motor driving circuit. And it is also followed by the web

camera and then the signals from the camera will transmit to the

Pc for showing the pathe that the robotic car gone.


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Microcontroller programming is done to generate the control

signals provided to the motor driving circuit. RS232 serial

communication port and Microcontroller 18F452 is interfaced

using a MAX 232 for logic conversion from CMOS to TTL

The stepper motor in the motor driving circuit picks up the

control signals and drives the wheels. Microcontroller output is

three controlling signals that are taken up by the interfacing

module made up of TIP 122 and sent to the motor driving circuit for

driving the wheels. The Web camera placed infront of the

moving part takes up instantaneous images &the user can check

the images instantaneously. If any obstacle comes in the

designed path he can see the image and can redraw a new path

for the destination

The Circuit diagram of mobile part will be shown in

figure. It will consists of Voltage Regulated Ic LM7805 is used

for voltage for the power supply. 10MHz crystal oscillator will

be used for the frequency generation for the microcontroller Ic.

RS232 is used for transmission and reception of the signals.

The collector of TIP122 is connected to the coils of the motor

for giving signals to the transmitter.

College of engineering,Trivandrum



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PIC MICROCONTROLLERS

PIC is a family of Harvard architecture microcontrollers

made by Microchip Technology, derived from the PIC1640

originally developed by General InstrumentsMicroelectronics division. The name PIC initially referred to

Programmable Interface Controller, but shortly thereafter

was renamed Programmable Intelligent Computer.

PICs are popular with developers and hobbyists alike dueto their low cost, wide availability, large user base, extensive

collection of application notes, availability of low cost or free

development tools, and serial programming (and re-

programming with flash memory) capability.

Core Architecture

The PIC architecture is distinctively minimalist. It is

characterized by the following features:

Separate code and data spaces (Harvard architecture)

A small number of fixed length instructions


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Most instructions are single cycle execution (4 clock cycles),

with single delay cycles upon branches and skips

A single accumulator (w), the use of which (as source

operand) is implied (ie is not encoded in the opcode)

All RAM locations function as registers as both source and/or

destination of math and other functions.

A hardware stack for storing return addresses

A fairly small amount of addressable data space (typically 256

bytes), extended through banking

Data space mapped CPU, port, and peripheral registers

The program counter is also mapped into the data space and

writable (this is used to implement indirect jumps)

Unlike most other CPUs, there is no distinction between

memory and register space because the RAM serves the

job of both memory and registers, and the RAM is usually just

referred to as the register file or simply as the registers.

Data Space (RAM)

PIC have a set of registers that function as general

purpose RAM. Special purpose control registers for on-chip

hardware resources are also mapped into the data space. The


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addressability of memory varies depending on device series,

and all PIC devices have some banking mechanism to extend

the addressing to additional memory. Later series of devices

feature move instructions which can cover the whole

addressable space, independent of the selected bank. In earlier

devices (i.e., the baseline and mid-range cores), any register

move has to be achieved via the accumulator.

To implement indirect addressing, a file select register (FSR)

and indirect register (INDF) are used: A register number is

written to the FSR, after which reads from or writes to INDF will

actually be to or from the register pointed to by FSR. Later

devices extended this concept with post-and pre-

increment/decrement for greater efficiency in accessing

sequentially stored data. This also allows FSR to be treated

almost like a stack pointer.

External data memory is not directly addressable except in some

high pin count PIC18 devices.


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Code Space

All PICs feature Hardvard architecture, so the code space and

the data space are separate. PIC code space is generally

implemented as EPROM,ROM, or flash ROM.

In general, external code memory is not directly addressable due

to the lack of an external memory interface. The exceptions are

PIC17 and select high pin count PIC18 devices.

Word Size

The Word size of PICs can be a source of confusion. All PICs

handle (and address) data in 8-bit chunks, so they should be

called 8-bit microcontrollers. However, the unit of addressability

of the code space is nit generally the same as the data space. For

example, PICs in the baseline and mid-range families have

program memory addressable in the same wordsize as the

instruction width, ie. 12 or 14 bits respectively. In contrast, in the

PIC18 series, the program memory is addressed in 8-bit


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increments (bytes), which differs from the instruction width of 16

bits.

In order to be clear, the program memory capacity is usually

stated in number of (single word) instructions, rather than in

bytes.

Stacks

PICs have a hardware call stack, which is used to save return

addresses. The hardware stack is not software accessible on

earlier devices, but this cganged with the 18 series devices.

Hardware support for a general purpose parameter stack was

lacking in early series, but this greatly improved in the 18 series,

making the 18 series architecture more friendly to high level

language compilers.

Instruction Set

A PICs instructions vary in number from about 35 instructions

for the low-end PICs to over 80 instructions for the high-end

PICs. The instruction set includes instructions to perform a


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variety of operations on registers directly, the accumulator and a

literal constant or the accumulator and a register, as well as for

conditional execution, and program branching.

Some operations, such as bit setting and testing, can be

performed on any numbered register, but bi-operand arithmetic

operations always involve W; writing the result back to either W

or the other operand register. To load a constant, it is necessary

to load it into W before it can be moved into another register. On

the older cores, all register moves needed to pass through W, but

this changed on the high end cores.

PIC cores have skip instructions which are used for conditional

execution and branching. The skip instructions are: skip if bit

set, and, skip if bit not set. Because cores before PIC18 had

only unconditional branch instructions, conditional jumps are

implemented by a conditional skip (with the opposite condition)

followed by an unconditional branch. Skips are also of utility for

conditional execution of any immediate single following

instruction.

The PIC architecture has no (or very meager) hardware support

for automatically saving processor state when servicing


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interrupts. The 18 series improved this situation by

implementing shadow registers which save several important

registers during an interrupt.

In general, PIC instructions fall into 5 classes:

1. Operation on W with 8-bit immediate (literal) operand. E.g.

movlw (move literal to W), andlw (And literal with W). One

instruction peculiar to the PIC is retlw, load immediate into W and

return, which is used with computed branches to produce lookup

tables.

2. Operation with W and indexed register. The result can be

written to either the W register (e.g. addwf reg, w). or the selected

register (e.g.addwf reg,w).

3. Bit operations. These take a register number and a bit

number, and perform one of 4 actions: set or clear a bit, and

test and skip on set/clear. The latter are used to perform

conditional branches. The usual ALU status flags are

available in a numbered register so operation

3. Control transfers. Other than the skip instructions

previously mentioned, there are only two: goto and call.


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4. A few miscellaneous zero-operand instructions, such as

return from subroutine, and sleep to enter low-power mode.

Limitations

The PIC architecture have several limitations:

Only a single accumulator

A small instruction set

Operations and registers are not orthogonal; some instructionscan address RAM and / or immediate constants, while others

can only use the accumulator

Memory must be directly referenced in arithmetic and logic

operations, although indirect addressing is available via 2

additional registers

Register-bank switching is required to access the entire RAM

of many devices, making position-independent code complex

and inefficient

Cnditional skip instructions are used of conditional branch

instructions used by most other architectures

The following limitations have been addressed in the PIC18,

but still apply to earlier cores:


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Indexed addressing mode is very rudimentary.

Stack:

The hardware call stack is so small that program structure

must often be flattened

The hardware call stack is not addressable, so pre-emptive

task switching cannot be implemented

Software-implemented stacks are not efficient, so it is

difficult to generate reentrant code and support local variables

Program memory is not directly addressable, and thus space-

inefficient and / or time-consuming to access. (Thus is true ofmost Harvard architecture microcontrollers.)

With paged program memory, there are two page sizes to

worry about: one for CALL and GOTO and another for

computed GOTO (typically used for table lookups). For

example, on PIC16, CALL and GOTO have 11 bits of

addressing, so the page size is 2KB. For computed GOTOs,

where you add to PCL, the page size is 256 bytes. In both


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cases, the upper address bits are provided by the PCLATH

register. This register must be changed every time control

transfers between pages. PCLATH must also be preserved by

any interrupt handler.

PIC18 High End Core Devices

Microchip introduced the PIC18 architecture in 2002.

Unlike the 17 series, it has proven to be very popular, with a

large number of device variants presently in manufacture. In

contrast to earlier devices, which were more often than not

programmed in assembly, C has become the predominant

development language.

The 18 series inherits most of the features and

instructions of the 17 series, while adding a number of

important new features:

Much deeper call stack (31 levels deep)

The call stack may be read and written

Conditional branch instructions

Indexed addressing mode (PLUSW)


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Extending the FSR registers to 12 bits, allowing them to

linearly address the entire data address space

The aqddition of another FSR register (bringing the number

up to 3)

The auto increment/decrement feature was improved by

removing the control bits and adding four new indirect

registers per FSR. Depending on which indirect file register

is being accessed it is possible to postdecrement,

postincrement, or preincrement FSR; or from the effective

address by adding W to FSR.

In more advanced PIC18 devices, an extended mode

is available which makes the addressing even more favorable

to compiled code:

A new offset addressing mode; some addresses which were

relative to the access bank are now interpreted relative to the

FSR2 register The addition of several new instructions,notable for

manipulating the FSR registers.


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These changes were primarily aimed at improving the

efficiency of a data stack implementation. If FSR2 is used

either as the stack popinter or frame pointer, stack items may

be easily indexedallowing more efficient re-entrant code.

Microchip C18 chooses to use FSR2 as a frame pointer.

Device Variants and Hardware Features

PIC devices generally feature:

Sleep mode (power saving).

Watchdig timer.

Various crystal or RC oscillator configurations, or an

external clock.

Variants

Within a series, there are still many device variants

depending on what hardware resources the chip features.

General purpose I/O pins.

Internal clock oscillators.

8/16 Bit Timers.


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Internal EEPROM Memory.

Synchronous/Asynchronous Serial Interface USART.

MSSP Peripheral for I2C and SPI Communications.

Capture/compare and PWM modules.

Analog-to-digital converters (up to 1.0 MHz).

USB, Ethernet, CAN interfacing support.

External memory interface.

Integrated analog RF front ends (PIC16F639, and rfPIC).

KEELOQ Rolling code encryption peripheral

(encode/decode)

Fig:D-subconnectors. Fig:Left: DE9M Right: DB25F

Path Following Robo Car

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