AUTONOMUS_MOBILE_ROBOT

AUTONOMOUS MOBILE ROBOT

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ABSTRACT

The paper namely “Autonomous mobile Robot” deals the automation of dust cleaning by

using programmed mobile robots. Here the mobile robot is constrained to move in pre-specified

network of roads. The pre-specified path of mobile robot can be previously calculated or it may

be identified through sensors like infrared or ultrasonic. Almost all vacuum cleaners are handled

by human beings through hands or it may be mounted on a vehicle where the vehicle can be

guided by controller. Our autonomous mobile robot is designed for service oriented application

and plays a vital role for cleaning the dust or cotton in an industry to make the working

environment as green. Autonomous mobile robots can access minimum work from the human.

This is due to the supervisory control of microcontroller and sensors used.

It has an ultrasonic sensor for collision detection and infrared rangers for position

determination. Drive unit is fitted in the vehicle to drive the mobile platform. The driving unit

works according to the signal form the controller unit. Then the vehicle moves left or right based

on the obstacle detected by the sensor. Based on the vehicle movement, the vacuum cleaner fitted

with a custom nozzle allows it to pick up debris in its path. A dust bag is fitted with the vacuum

cleaner to collect the waste cottons or dust. Power sources is got from the battery unit.

Thus an autonomous vacuum cleaner robot can navigate and vacuum through a room or a

house with the minimum human assistance

INTRODUCTION


Robots are becoming essential and integral intelligent devices that are used to

perform a variety of tasks, which sometimes are beyond the scope of human beings.

They find extensive use in areas like industrial automation, nuclear installation,

pharmaceutical and medical fields, space research etc

The development of an autonomous mobile robot able to vacuum a room or

even an entire firm is not a trivial challenge. Probably the decision that the most affects

the robot complexity is the ability of mapping the environment so that it would exhibit a

much better efficiency when compared with the minimalist approach as the one

followed (random navigation).With the aim of keeping our robot as simple as possible,

while able to perform the initial goals, i.e. an autonomous vacuum cleaner robot able to

randomly navigate through a room or a house with the minimum human assistance, the

following specifications were found:

• Obstacle avoidance

• Collision detection

• Autonomous battery charging

• Autonomous dust bag dump

These specifications correspond to some of the expected behaviors that will be

programmed into the robot. Other behaviors that will increase the overall performance

of the robot, such as self calibration of the sensors and navigation with some memory

(not completely random) were also considered.

During robot moving, the obstacle is detected by the two sensors, one is

ultrasonic sensor and another one is infrared sensor. Here these sensors give input signal

to the controlling unit (i.e., 89C51 microcontroller). According to the input signal

coming from these sensors, the controller unit interrupts the drive unit. Drive unit is

fitted in the vehicle to drive the mobile platform. The driving unit works according to

the signal form the controller unit. Then the vehicle moves left or right based on the

obstacle detected by the sensor. Here the vacuum cleaning used by a hand vacuum

cleaner, placed over a mobile platform Based on the vehicle movement dust are cleaned.

LITERATURE SURVEY


Industrial robots have been in use many industrial applications. The level of

development in industrial production is already well advanced; the service area is just

now emerging as the future field of application. The number of service robots currently

in operation is small, but the number of people working in the service shows a constant

growth rate.

DEFINITION OF ROBOT:

A robot is a reprogrammable, multifunctional manipulator designed to move

material, parts, tools or specialized devices through variable programmed motions for

the performance of a variety of tasks

STUDY OF SERVICE ROBOT:

Definition of service robot is a freely programmable kinematics device which

performs services semi or fully automatically services are tasks which do not contribute

to the industrial manufacturing of goods but are the execution of useful work for

humans and equipment.Robots in the service sector will differ from industrial robots

because they will be individually designed for the execution of a given task taking place

in a specific environment following a predefined organizational scheme. Some example

of already produced service robots are Aircraft cleaning Robot, cleaning Robot for

sewers.

DESCRIPTIONBLOCK DIAGRAM OF AUTONOMOUS MOBILE ROBOT:

The block diagram consists of a microcontroller, power supply unit, PC interface

unit, LCD display and keyboard control unit, stepper motor driving unit and sensors and

signal conditioning unit.


DESCRIPTION OF THE BLOCK DIAGRAM:

The major units in the block diagram are

1. Sensing Unit

2. Controlling Unit

3. Driving Unit

4. Power Supply Unit

SENSING UNIT:

The sensing unit has the infrared sensor and ultrasonic sensor. The infrared

sensor is employed for path detection. It senses for the presence of obstacle in its path.

If any obstacle is detected, the receiver gets a signal and sends it to microcontroller. The

robot waits until the obstacle is cleared. Here the sensing range is lesser.

The ultrasonic sensor is mounted over a programmable servo turret. Initially the

ultrasonic sensor is kept at middle position, when the sensor senses any obstacle, the

microcontroller receives the data from the sensor and it will rotate the base plate of the

stepper motor. Thus the ultrasonic sensor can sense the dimension of the obstacle. As a

result the microcontroller instructs the stepper motor to deviate its path.

CONTROLLING UNIT:

The microcontroller used here is ATMEL 89C51, which is coded in Assembly

language. Depending upon the signals from the infrared sensor and ultrasonic sensor,

the microcontroller controls the movement of the stepper motor. The stepper motor is

connected to the controller through drive circuit.

DRIVING UNIT:

The stepper motor is a permanent magnet type whose shaft is connected to the

wheels of the robot. Here we use three stepper motors. The motor at the front is used for

forward movement and the left right movement. The top motor is used to rotate the


sensor. The pulse signals from the controller unit energize the coils of the stepper motor

for driving it.

POWER SUPPLY UNIT:

The power supply unit consists of battery, DC to DC converter, regulator

circuit. The power supply unit gives enough supply to the microcontroller, sensing unit,

stepper motor drive and to the vacuum cleaner. The battery low is indicated by alarm

and when microcontroller senses it, moves the robot towards charging unit

POWER SUPPLY CIRCUIT

CONTROLLING CIRCUIT:

CONTROLLING CIRCUIT OF AUTONOMOUS MOBILE ROBOT


STEPPER MOTOR DRIVING CIRCUIT:

SENSORS AND SIGNAL CONDITIONING UNIT

ULTRASONIC SENSORS

A sonar range finder works by generating a short burst of sound – a “ping” – then

listening for the echo of the sound when it bounces off the nearest object.

(a) (b)

By accurately measuring the time from the start of the ping until the echo returns

back to the sensor, the distance to the nearest object can be determined. Sound travels at

1116.4 feet/second (340.29 meters/second) at sea level. The sound travels to the object

and back, so the distance to the object can be calculated by dividing the elapsed time by

twice the speed of sound.

OPERATION:http://www.eforu.page.tl/ 8

As shown in above figure (b), a sonar range finder is operated by generating a

pulse of greater than 10 microseconds on its trigger input signal. This causes the range

finder to issue a ping. The range finder enables its receiver 100 microseconds after the

ping and raises the sensor’s echo output signal. The delay in enabling the receiver

prevents the receiver from hearing the transmission of the ping. When the receiver hears

the echo it drops the output signal. The elapsed time between the ping and the echo can

be determined by measuring the pulse duration on the echo line and adding 100

microseconds.

INFRARED SENSORS:

Infrared sensors consist of infrared transmitter and infrared receiver. The

transmitter transmits beam of infrared rays. The receiver works on the principle of

phototransistor that when light image falls on the exposed base of transistor, then the

collector will allow current through base.

Here the detection is done by two methods. In the first method the beam of

light rays are passed towards the receiver and the receiver will give continuous current

until the obstacle disturbs the light ray.


THE OBJECT DEACTIVATES THE RECEIVER

THE OBJECT ACTIVATES THE RECEIVER

INFRARED SENSORS

In another method, the beam of light rays are passed, if any obstacle disturbs the

light rays, then the infrared rays gets reflected towards the receiver and thus the receiver

will give voltage output.

CONTROLLING UNIT:

The micro controller used in this project is ATMEL version of micro controller

8051, the IC 89C51.The advantages of this is that it has a built in E-PROM, which

facilitates in the reduction of the space consumed in the PCB, cost of fabrication, ease

of programming and increased speed of accessing data from the E-PROM.

Microcontroller

89C51, an 8 bit chip micro controller has got a powerful CPU optimized for

control application. It has 64k program memory address space,64K data memory

address space,4k bytes of on-chip ROM( read only memory),128 bytes of chip

RAM(Read/Write memory),4 8-bit bi-directional parallel ports, one full-duplex serial

port,2 16- bit timer/counter and extensive interrupt structure. This is best suited as it

incorporates a special set of instruction which is capable of bit addressing the on chip I/

O features of 8951.

STEPPER MOTOR:

INTRODUCTION


User interface

High level commands Step Pluses

Motor Current

Indexer Driver Motor

Motion Control means to accurately control the movement of an object based on

speed, distance, load, inertia or a combination of all these factors. There are numerous

types of motion control systems, including; Stepper Motor, Linear Step Motor, DC

Brush, Brushless, Servo, Brushless Servo and more. A Stepper motor is a marvel in

simplicity. It has no brushes, or contacts. Basically it's a synchronous motor with the

magnetic field electronically switched to rotate the armature magnet around.

A Stepping Motor System consists of three basic elements, often

combined with some type of user interface (Host Computer, PLC or Dumb Terminal):

STEPPER MOTOR CONTROL DIAGRAM

The Indexer (or Controller) is a microprocessor capable of generating step

pulses and direction signals for the driver. The Driver (or Amplifier) converts the

indexer command signals into the power necessary to energize the motor windings.

There are numerous types of drivers, with different current/amperage ratings and

construction technology.

The Step Motor is an electromagnetic device that converts digital pulses into

mechanical shaft rotation. Advantages of step motors are low cost, high reliability, high

torque at low speeds and a simple, rugged construction that operates in almost any

environment. The main disadvantages in using a step motor is the resonance effect often

exhibited at low speeds and decreasing torque with increasing speed.

STEPPER MOTOR SPECIFICATIONS

Voltage - 12v DC

Current - 0.67A/ phase


Step angle - 1.8Deg/step

Torque - 7 Kg-cm

Type - STM 901S

MOTOR STIFFNESS

By design, stepping motors tend to run stiff. Reducing the current flow to the

motor by a small percentage will smooth the rotation. Likewise, increasing the motor

current will increase the stiffness but will also provide more torque. Trade-offs between

speed, torque and resolution are a main consideration in designing a step motor system.

VACUUM CLEANERS

Vacuum cleaner is the device used to clean the surface by vacuuming action

over the dusts. The vacuum pump, vacuum motor, dust bag are the parts in conventional

vacuum cleaner. The high power vacuum motor rotates the vacuum pump in high speed

and the high speed pump generates vacuum in the suction area which makes high

pressure air to move through the inlet port. This high pressure air carries the dust

through the inlet port and the dusts are collected in the dust bag.

WORKING OF VACUUM CLEANERS

The main accessories of vacuum cleaner is the intake port, which may include a

variety of cleaning accessories, the exhaust port, the electric motor, the fan, the porous

bag and the housing, which contains all the other components. The motor is attached to

the fan, which has angled blades as like propeller blades. As the fan blades turn, they

force air forward, towards the exhaust port. When air particles are driven forward, the

density of particles and the air pressure increases in front of the fan and decreases

behind the fan. The pressure level in the area behind the fan drops below the ambient air

pressure level outside the vacuum cleaner. This creates suction, a partial vacuum, inside

the vacuum cleaner. The ambient air pushes itself into the vacuum cleaner through the

intake port because of the air pressure inside the vacuum cleaner is lower than the

pressure outside and carries in the dust particles and the debris.

WORKING OF VACUUM CLEANERS


PATH PLANNING AND NAVIGATION

In the mobile robots the path detection and path planning is much important

factor for accurate mobility. The path detection can be done in various methods

depending upon the accuracy required and the work space environment.

INFRARED REFLECTION TYPE PATH DETECTION

INFRARED REFLECTION TYPE PATH DETECTION


In the infra red reflection type, two infrared transceiver modules are used.

Output from one side of the module is used to control the other side motor and vice

versa. Here if the path used is a reflective type and the sensor is made to follow the edge

of the path. When the path takes deviation, then the outer side sensor will not get the

signal so that the inner motor will be stopped. This makes the path deviation easier.

Here the path detection is of closed loop type but less accurate.

INDUCTIVE COIL TYPE PATH DETECTION

Here two inductive coils are made to move over the work space. The

floor consists of inductive lines in a linear arrangement. The inductive coil in the robot

is made to follow the lines in the floor. The two coils show different current output

depending upon the position of the coil over base coil.

XY COORDINATES TYPE PATH PLANNING

With the help of microcontroller the x, y coordinates are plotted and the

motors are made to move in a programmed path. Here the map of the floor is designed

with cad software by considering the obstacles and the coordinates are then loaded in

the controller.

IMAGE SENSOR TYPE PATH PLANNING


To eliminate the problem of poor accuracy, image sensors are used. Different

types of image sensors are available according to the accuracy, sensing, cost and pixel

color and resolution. The image is captured by the cameras and the image captured is

analyzed with stored data and the microcontroller will generate command to drive the

motor in specified route.

PATH DETECTION AND OBSTACLE AVOIDANCE

The below diagram shows the deviation of pre-programmed path of mobile

robot, when it encounters a obstacle in its path. The flow chart describes the working of

the robot by sensing the obstacle and moving in programmed path. Here the robot uses

three sensors to sense the obstacle. It has two infrared sensors fitted at the left and right

corner. The ultrasonic sensor is fitted in the programmable rotary table in the middle.

When the robot control is switched on in the autonomous mode, the controller

commands the robot to move in a straight

path, in the programmed manner

When the robot moves in a programmed path, the sensor senses for the obstacle.

As the infrared sensor is for low range sensing, the ultrasonic sensor is used further to

locate the size, shape of the obstacle. If any one of the infrared sensors is sensed, then it

gives the analog voltage to the ADC where it gives the digital pulse to the controller.


Now the controller rotates the base of ultrasonic sensor as per the angle and from the

received data, the controller can locate the size and shape of the obstacle.

If the location of obstacle in right is more, the controller orders the robot to turn

left and move forward. If the obstacle is cleared from the path, the robot turns right and

moves forward. If the robot moved outside the obstacle, then it returns to its path. This

procedure can be continued for the presence of obstacle in the left. If the obstacle is in

the centre, then the robot can take right path. The loop will be followed continuously to

detect the obstacle and makes the system to move in right path.


FLOW CHART FOR OBSTACLE DETECTION


CONCLUSION AND FUTURE ENHANCEMENTS:

This project “Autonomous Mobile Robot” eliminates the drawbacks of various

robotics manufacturers. The benefits of autonomous mobile robot couldn’t have an

observer, due to the sufficient sensor provided. The sequence of predefined path can be

modified. It uses battery, provides an on-board power supply and weightless mobile

platform comparing to other robots. It eliminates the human labor for cleaning the

cotton in the room. This robot is compact in size and also economical one. The benefit

of Autonomous Mobile Robot is the path navigation due to sufficient sensor provided

and hence there is no need for camera, personal computer and observer. Actually, the

cotton debris is cleaned by the human labor and it may cause more cost. The above

problem can overcome by implementing “Autonomous Mobile Robot” in the shop floor.

In the sensor unit instead of ultrasonic sensor, image sensor of black and white

(For low cost and less accuracy) or the color sensor (For high cost and high accuracy).

This also requires powerful processors with high memory compatibility for image

sensing and image processing. This eliminates the poor accuracy of infra red sensor and

the ultrasonic sensor.

The low power battery is eliminated by adding a light weight high power

battery. Also for this increased weight, stepper motor of required torque is used. Here

the problem is that the weight of whole system affects the driving system and the

driving system affects the battery used. A trial and error method is implemented to

maintain the system stability. Though the system may get complicated, once the work

area is configured, and then the whole system can work with more accuracy and

eliminates manual work.

BIBLIOGRAPHY

Andrew Blake, Gabriel Hamid, and Lionel Tarassenko, “A Design for a Visual

Motion Transducer”, IEEE Transactions on Robotics and Automation, Vol. 11,

NO.5, October 1995

Fabrice R. Noreils and Raja G. Chatila, “Plan Execution Monitoring and

Control Architecture for Mobile Robots”, IEEE Transactions on Robotics and

Automation, Vol. 11, NO. 2, April 1995


I.Ulrich, F. Mondada and J.D.Nicoud,” Autonomous Vacuum Cleaner”,

Robotics and autonomous Systems 19, 1997

www.mekatronix./com

www.poly.edu

www.robotstore.com


http://www.robotstore.com/

AUTONOMUS_MOBILE_ROBOT

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