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AXIS COLLEGE OF ENGINEERING & TECHNOLOGY Murikkingal P.O, Thrissur (Affiliated to University of Calicut)
DEPARTMENT OF MECHANICAL ENGINEERING
MINI PROJECT REPORT
FABRICATION OF AUTOMATIC GUIDED VEHICLE AJITH ARAVIND JESBIN JOHNSON VINOD.K.J VISHNU.T.SAJEEVAN
AXIS COLLEGE OF ENGINEERING & TECHNOLOGY P.O.MURIKKINGAL, THRISSUR
DEPARTMENT OF MECHANICAL ENGINEERING
CERTIFICATE This is to certify that this Project Report Titled FABRICATION OF AUTOMATIC GUIDED VEHICLE was carried out by the sixth semester students of Mechanical engineering in partial fulfilment of the requirement for the award of Bachelor in Technology in mechanical engineering Under University of Calicut during the year 2012-2013,of Axis College of Engineering & Technology, Thrissur
AJITH ARAVIND, JESBIN JOHNSON, VINOD.K.J, VISHNU.T.SAJEEVAN are members of the batch Project Guide Joffin Jose P
S.Krishnanunni
Project Coordinator
H.O.D Mechanical Engg
Place: Thrissur Date:
Fabrication of Automatic Guided Vehicle
ACKNOWLEDGEMENT We express our deep sense of gratitude and indebtedness to Asst Prof. S.Krishnanunni, Head, Department of Mechanical Engineering for his valuable advice, constant encouragement and constructive criticism during the course of the project and also during the preparation of this manuscript, We place on record the valuable suggestions and numerous constructive comments rendered by Asst Prof. Joffin Jose.P, Lecturer, Department of Mechanical Engineering and for being our internal guide in the design and implementation of our project. We are highly indebted to the staff members of Mechanical Department, especially Asst.Professors Clint.K.S, Krishnakiran.T.T, Jineesh.V.V, Sankar Raj, Renjith for their wholehearted support and co-operation. We also express our sincere thanks to all the classmates for their support and cooperation in completing the project work. Above all, we should express our supreme gratitude to almighty God.
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Fabrication of Automatic Guided Vehicle
ABSTRACT The Automatic Guided Vehicle refers a type of system that can be used in production as well as in other industries etc. This system includes a battery operated remote sensing locomotive (carrier) on which a small lift is provided, specific path over which it moves, sensors for sensing the the obstructions on the path of the carrier. Also sensors for sensing exact positions from where load wants to carry and to where. The remote sensing carrier moves using the electric power from the battery. It moves with a low and constant speed on the prescribed path. The path has a specific color. The bottom of the carrier have sensor which is always coupled with the path. From the remote station we send only information for moving the carrier, not for steering it. The steering is done by the path. The front side of carrier vehicle contains sensors for sensing the obstructions on the path. As it reaches the collecting station, its top floor lift to a small distance and lift the stand which contains the parts wants to assemble, supply. And the carrier moves through the path and reaches the supply station. The sensor provided on the carrier detected the station and unload the stand contains assembly parts at that station. And move to collecting stations again. Continues working cycles for making this project a reality.
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Fabrication of Automatic Guided Vehicle
TABLE OF CONTENT
CHAPTER
TITLE
PAGE
CHAPTER I: INTRODUCTION 1.1
Automatic Guided Vehicle
1
1.2
Background
3
1.3
Problem Statement
3
1.4
Project and It’s Scope
5
1.5
Market Survey
6
CHAPTER II: LITERATURE REVIEW
7
2.1
AGV Built Worldwide Used
10
2.2
Mobile Post Distribution System (MOPS)
11
2.3
The Parkshuttle AGVs of Amsterdam’s Schiphol Airport
12
2.4
Line Following Robot
13
2.5
The Kerwin’s Line Following Robot
13
CHAPTER III: COMPONENTS SELECTION AND DESCRIPTION
14
3.1
Design Objectives
14
3.2
Design Considerations
15
3.3
Components of AGV
17
3.4
Mechanical Part
19
3.4.1
Chassis
19
3.4.2
Steering System
20
3.4.3
Lifting Mechanism
22
3.5
3.6
Electrical Components
24
3.5.1
DC Motor
24
3.5.2
Battery
25
Electronics Components
26
3.6.1
Microcontroller
26
3.6.2
Motor Driver
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Fabrication of Automatic Guided Vehicle 3.6.3
Regulators
33
3.6.3.1 7805 Regulator
33
3.6.3.2 LM317 Regulator
34
3.6.4
IR Sensor
35
3.6.5
Magnetic Sensor
38
3.6.6
Display Unit
40
3.7
Software Components
42
3.8
Program Source Code
43
CHAPTER IV: DEVELOPED PROTOTYPE
50
4.1
Structure
50
4.2
Sensors Positions
52
4.3
Flow Chart
54
4.4
Block Diagram
55
4.5
Circuit Diagram
56
4.6
Theoretical and Logical Calculations
58
4.7
Billing
61
CHAPTER V: CONCLUSION
62
REFERENCES
64
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Fabrication of Automatic Guided Vehicle
LIST OF TABLES Table Number
Title
Page
2.1
Line Following Methods
13
3.1
Technical Data for Chassis
19
3.2
Steering Specifications
21
3.3
Motor Specifications
24
3.4
Battery Specifications
25
3.5
Specifications of ATmega 328
27
3.6
Important Connections
27
3.7
Technical Specifications of L293D
32
3.8
Maximum Rating of 7805
33
3.9
Technical Specifications of 7805
34
3.10
Technical Specifications of LM 317
34
3.11
Technical Specifications of IR Pair
37
3.12
Technical Specifications of Magnetic Sensors
39
3.13
Technical Specifications of Display Unit
40
3.14
Pin Configuration
40
4.1
Billing Table
61
LIST OF FIGURES Figure Number
Title
Page
2.1
The Mobile Post System
11
2.2
The Parkshuttle AGV’s of Amsterdam
12
2.3
The Kerwin’s Line Following Robot
13
3.1
Chassis of AGV
19
3.2
Differential Steering
20
3.3
Small Radius Turning
21
3.4
Lifting Using Threaded Shaft
22
3.5
Structure of Lift
23
3.6
DC Motor with Gearbox
24
3.7
Battery
25
3.8
ATmega 328 Microcontroller
28
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Fabrication of Automatic Guided Vehicle
Figure Number
Title
Page
3.9
Motor Driver (L293D)
29
3.10
L293D Connected with Two Motors
30
3.11
L293D Connected with One Motor
30
3.12
Circuit Connection of Driving Motor
31
3.13
Connection of Lifting Motor
31
3.14
PWM
32
3.15
7805 Regulator
33
3.16
LM 317 Circuit
34
3.17
IR for Path Detection
35
3.18
IR Pair Circuit
36
3.19
Magnetic Sensor
39
3.20
Application Circuit of Display Unit
41
4.1
Front View of AGV
50
4.2
Top View of AGV
51
4.3
IR Sensor Positions of AGV
52
4.4
Magnetic Sensor Positions
53
4.5
Flow Chart
54
4.6
Block Diagram
55
4.7
Circuit Diagram
56
4.8
Fully Developed Prototype
57
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Fabrication of Automatic Guided Vehicle
CHAPTER I INTRODUCTION 1.1 AUTOMATED GUIDED VEHICLE An automated guided vehicle or automatic guided vehicle (AGV) is a mobile robot that follows markers or wires in the floor, or uses vision or lasers. They are most often used in industrial applications to move materials around a manufacturing facility or a warehouse Automated guided vehicles increase efficiency and reduce costs by helping to automate a manufacturing facility or warehouse. The AGV can tow objects behind them in trailers to which they can autonomously attach. The trailers can be used to move raw materials or finished product. The AGV can also store objects on a bed. The objects can be placed on a set of conveyor and then pushed off by reversing them. Some AGVs use forklifts to lift objects for storage. AGVs are employed in nearly every industry, including, pulp, paper, metals, newspaper, and general manufacturing. Transporting materials such as food, linen or medicine in hospitals is also done. An AGV can also be called a laser guided vehicle (LGV) or self-guided vehicle (SGV). Lower cost versions of AGVs are often called Automated Guided Carts (AGCs) and are usually guided by specific lines magnetic tape. AGCs are available in a variety of models and can be used to move products on an assembly line, transport goods throughout a plant or warehouse, and deliver loads to and from stretch wrappers and roller conveyors.AGV applications are seemingly endless as capacities can range from just a few kgs to hundreds of tons. The Aim of the project is to design and fabricate such a AGV There are many definitions of AGVs, different according to points of view. Wikipedia, the free encyclopedia, defines AGVs as: “A robot that been used highly in industrial applications to move materials from point to point”
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Fabrication of Automatic Guided Vehicle
The American Society of Safety Engineers (ASSE) defined AGVs as: a. Machines without drivers that can move along pre-programmed routes, or use sensory and navigation devices to find their own way around. b. Vehicles that are equipped with automatic guidance systems and are capable of following prescribed paths. Or Driverless vehicles that are programmed to follow guide path
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Fabrication of Automatic Guided Vehicle
1.2 BACKGROUND The creations of Automated Guided Vehicle (AGV) have been around since the 1950’s and the technology was first developed by Barret Electronics from Grand Rapids, Michigan. It was then developed by the Europeans in the 1970’s and nowadays AGVs can be found in any countries. One of the first AGVs was a towing vehicle that pulled a series of trailers between two points, and today’s there are many task given to AGVs and they also have their own name and potentials. Considering the full potentials and advantages of the Automated Guided Vehicle (AGV) in our livings, it is valuable to do this project, as it also will be the first step towards the creation of more intelligent technology or system. The simplest AGV model may use just a sensor to provide its navigation and can be the complex one with more sensors and advance systems to do the task. They can work or do the task everywhere needed but the safety for the AGV as well as the people and environment surround it must be provided. The AGVs is just the same as mobile robot, which can moves from one place to another to do their task, but mostly the mobile robot is used for difficult task with dangerous environment such as bomb defusing. Furthermore, the mobile robot can be categorized into wheeled, tracked, or legged robot. Although the AGVs may not be glamorous of robots, but their work, which usually menial, are often be essential to the smooth running of factories, offices, hospitals, and even houses. They can work without any complaint around many workplaces all over the world.
1.3 PROBLEM STATEMENT There are many reasons which yield to the creation of Automated Guided Vehicle (AGV) around the world. Mostly the reason is to overcome the logistic problems that often occurred in the workplaces and to make improvement to the facilities provided in the workplaces. Usually the AGVs are implemented in factories, hospitals, offices, houses, and even can be found anywhere outdoors without the people surround realized it.
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Fabrication of Automatic Guided Vehicle In the industries or factories, the AGVs can ease the physical strain on human workers by performing tiring tasks, such as lifting and carrying heavy materials, more efficiently with no signs of fatigue creeping in. They can carry far more than human workers, and their movements can be tracked electronically at all times. Their movements can be timed to feed or collect products or materials from the work cells in the factories. Besides that, in the hospitals thousands of staff spends a portion of their day moving medical supplies, bedding, medicines and other equipment around large hospitals. By using the AGVs, the strain on the workers can be ease as well as the hospital’s system would be more smart and systematic without any bad complaint from the patients and people. AGVs also capable of both cutting cost and releasing more staff hours to tend and care for patients. Therefore it is very significant that the valuable knowledge on AGV construction is studied and be further implemented from the result of this project. It is due to its advantages to our own living and technology. We have pleasure in introducing our project AGV, which is equipped by microcontroller, motor driving mechanism, lift mechanism and battery. The power stored in the battery is used to drive the DC motor that causes the movement as well as lifting power to AGV. Battery assembled on the AGV is easily replaceable and detachable, used for recharging the battery, while the AGV is under roof.
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Fabrication of Automatic Guided Vehicle 1.4 PROJECT AND ITS SCOPE The objective and scope of this project is to create an AGV model that can follow a trail of line on a flat surface horizontally. This AGV model is using microcontroller to control all navigation and lifting functions during its operation. In other words, the microcontroller acts just like the brain for the model that controls all operation of the system. The model is a three-wheeled mobile robot that has the ability to follow line on floor. There are three wheels including two driving wheels controlled by two motors and a free wheel in front that is able to rotate 360°. With three wheels, both driving wheels are always in contact with the surface, because of the robot’s steering relies on both its driven wheels being in contact with the surface at all times. This project consists of four main stages, which are theoretical design, mechanical fabrication, electronic hardware design and as well as algorithm design in assembly language. The matter to be considered is how the robot can follow the trail of line continuously. It is also important to choose the most suitable microcontroller, actuators, and sensors to achieve the project objectives. .
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Fabrication of Automatic Guided Vehicle 1.5 MARKET SURVEY A market survey is an important requirement for initiating any successful business. The objective of a market survey is to collect information on various aspects of the business. This survey is a tool through which we can minimize risk. After the market survey, the results must be analyzed in order to finalize a business plan.
We are implementing automatic guided vehicle, which replaces the normal transporting methods. So that we wants to consider all the sections related to this works such as problems arising while installing. So we conducted a market survey by personnel interview techniques was used with the measure emphasis on personal interview method. Interviews were conducted through the structure questionnaire, Also we go through people who work in large industries such as production plant, supply station etc. The following questions are mainly taken for questionnaire: Area of applications? i.e. inside/outside/both Types surface of flooring? Weights of loads max? Distance to transportation? From the data which we got from the market survey we are well know about the things what the market needed, and what modifications should be taken to the system. And we analysis the data and make objectives want to goal.
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Fabrication of Automatic Guided Vehicle
CHAPTER II LITERATURE REVIEW
Automatic Guided Vehicles (AGVs) have played a vital role in moving material and product for more than 50 years. The first AGV system was built and introduced in 1953. It was a modified towing tractor that was used to pull a trailer and follow an overhead wire in a grocery warehouse. By the late 1950's and early 1960's, towing AGVs were in operation in many types of factories and warehouses. The first big development for the AGV industry was the introduction of a unit load vehicle in the mid 1970s. This unit load AGVs gained widespread acceptance in the material handling marketplace because of their ability to serve several functions; a work platform, a transportation device and a link in the control and information system for the factory. Since then, AGVs have evolved into complex material handling transport vehicles ranging from mail handling AGVs to highly automated automatic trailer loading AGVs using laser and natural target navigation technologies. In fact the improvement of AGVs over the last decade is deeply indebted to development of Scheduling, Algorithm and Steering methods. The problem of scheduling of AGVs and the other supporting equipments has been extensively studied by Basnet and Mize and Rachamadugu and Stecke currently providing the most up-to-date and comprehensive reviews in this area. Han and McGinnis have developed a real time algorithm in which material handling transporters are considered. Schriber and Stecke have shown how the additional consideration of the material handling system and limited buffers degrades the system performance. Sabuncuoglu and Hommertzheim have highlighted the importance of material handling and they compared several AGV dispatching rules. They have also shown how the buffer capacity can affect the performance of the system. Flexibility, which is a distinguishing feature of FMSs, has received an extensive amount of attention. Routing flexibility (i.e., alternative machines and processing routes) has been considered by Wilhelm and Shin, Chen and Chung, and Khoshnevis and Chen . These studies have indicated that dynamic routing (i.e., a path determined dynamically during schedule generation) performs better than a preplanned routing.
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Fabrication of Automatic Guided Vehicle Rachamadugu et al. Have proposed a quantitative measure of sequence flexibility and have shown that perfect sequence Flexibility improves system performance. Similar observations have been made by Lin and Solberg. In most work to date, tools, pallets/fixtures and their availability are not modeled adequately. A static allocation of tools is usually assumed in these studies. However, some researchers have considered a limited tool magazine capacity and the changing of tools from central tool storage. One purpose of this thesis is to develop an algorithm that can be used to investigate the research issues discussed above. This algorithm should not only consider the major elements of FMSs but also generate high quality schedules in a reasonable amount of time. In this thesis, the basic structure and characteristics of such an algorithm is described.
Kim et al. Proposed a deadlock detection and prevention algorithms for AGVs. It was assumed that vehicles reserve grid blocks in advance to prevent collisions and deadlocks among AGVs. A graphic representation method, called the "reservation graph," was proposed to express a reservation schedule in such a form that the possibility of a deadlock can be easily detected. A method to detect possible deadlocks by using the reservation graph was suggested. Maxwell and Muckstadt first introduced the problem of AGV flow system design. While their main concern is vehicle routing, they also address material flow path and station location design issues. The flow network they used, known as conventional configuration, is composed of unidirectional arcs. Gaskin and Tanchoco developed the first integer programming model for material flow path design. Given a fixed network of aisles and fixed pickup and delivery stations, the model assigns direction to arcs to minimize the total trip distances of loaded vehicles. Goetz and Egbelu developed an alternative model, where the station locations no longer are fixed but restricted to the nodes on the boundary of the cells. Sun and Tchernev provide a comprehensive review on the models developed for conventional configuration. Afentakis states the advantages of the loop layout as simplicity and efficiency, lowinitial and expansion costs, and product and processing flexibility. Loop layout has been studied by many researchers including Bartholdi and Platzman , Sharp and Liu ,Kouvelis and 8
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Fabrication of Automatic Guided Vehicle Kim , Egbelu , Banerjee and Zhou , and Chang and Egbelu. Bozer and Srinivasan initiate the concept of tandem configuration as a set of no overlapping, bidirectional loops, each with a single vehicle. Another problem in steering issues is to schedule several AGVs in a non-conflicting manner which is a complicated real-time problem, especially when the AGV system is bidirectional. In fact, many conflicting situations may arise such as head-on and catching-up conflicts when the AGVs or the guide-paths are bidirectional and if no efficient control policy is used to prevent them. Several conflict-free routing strategies have been proposed and can be classified into two categories:
Predictive methods: Aim to find an optimal path for AGVs. The conflicts are predicted off-line, and an AGV’s route is planned to avoid collisions and deadlocks. Reactive methods: the AGVs are not planned and the decisions are taken in a realtime manner according to the system state. These methods are based on a zone division of the guide-path and consider them as non sharable resources. Predictive methods give good performance, but are not very robust since they do not take into account real time problems. However, reactive methods are very robust but the resulting performances can be poor because the decisions are taken by considering a very short-term time horizon. In this report due to specification of the whole plan (presence of only one AGV) a kind of predictive method is proposed. In early 1990s Fuzzy logic came through to control and manipulate whole of the material flow in manufacturing floors. The main indication of employing this system on AGVs was the ability of controlling multiple AGV in a same time without collision.However, only simulation results are presented. Senoo et al used experimental results of a three wheeled mobile robot to discuss the stability of a fuzzy controller. It is also stated that fuzzy control was implemented in order to achieve reduction of steer energy, while maintaining better steer angle when compared with PI control. Fuzzy logic has found useful applications in control among other areas. One useful characteristic of a fuzzy controller is its applicability to systems with model uncertainty and/or unknown models. Another useful characteristic of a fuzzy logic controller is that it provides a framework for the incorporation of domain knowledge in terms of heuristic rules. 9
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Fabrication of Automatic Guided Vehicle Wuwei et al. They presented the new navigation method for AGV with fuzzy neural network controller when in the presence of obstacles. Their AGV can avoid the dynamic and static obstacle and reach the target safely and reliably. Wu et al. used fuzzy logic control and artificial potential field (APF) for AGV navigation. The APF method is used to calculate the repulsive force between the vehicle and the closest obstacle and the attractive force generated by the goal. A fuzzy logic controller is used to modify the direction of the AGV in a way to avoid the obstacle. Lin and Wang proposed a fuzzy logic controller for collision avoidance for AGV. They combined fuzzy logic with crisp reasoning to guide an AGV to get out of trap since memories of path and crisp sequence flows are handled by non-fuzzy processing. Their designed AGV was able to avoid collision with unknown obstacle. Alves and Junior used a step motor to turn the direction of the ultra-sonic sensors, so that each sensor can substitute two or more sensors in mobile robot navigation. Perhaps Sugeno has done one of the pioneering researches in mobile robot navigation using fuzzy logic control. The fuzzy control rules, which he defines for the controller, were derived by modeling an expert driving action. He made a computer model of a car in microcomputer to find fuzzy rules. The speed of the designed car was constant; then, the control input to the car is only the angle of the steering angle Mehdi Yahyaei has design a AGV using fuzzy logic system and a rotational ultra sonic sensor to steer the AGV to avoid collisions and obstacles. He also employed a programmable logic control (PLC) as the processor which makes the AGV to be ultimately fit to the industrial environments.
2.1 AUTOMATED GUIDED VEHICLE BUILT WORLDWIDE Some of the Automated Guided Vehicles (AGVs) that are well known are discussed in brief.
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Fabrication of Automatic Guided Vehicle 2.2 MOBILE POST DISTRIBUTION SYSTEM (MOPS) MoPS or Mobile Post Distribution System (Tschichold, Vestli, Schweitzer, 1999) is a research AGV developed at the Institute of Robotics in Zurich, Switzerland. It is used to transport mail around the Swiss Federal Institute of Technology in Zurich. MoPS is powered up by rechargeable batteries which give it a 4-hour active life, weighs around 90kg and can carry up to 50 kg of postal payload. It is also capable of hot-swapping its own batteries pack, thus ensuring 24h availability. The MOPS provide services of picking up boxes with incoming mail at the ground floor of the five floor building, which is sorted by human first, delivering them to the secretaries' offices, subsequently bringing back the outgoing mail to the ground floor station. It is also capable of switching floors by sending an infrared signal to the building’s lifts. As the building is open to the public, protection against theft of the mail is provided by motorized blinds over the pigeon-hole mail points, which can be opened by the robot and by authorized staff.
Fig 2.1 The Mobile Post System MOPS
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Fabrication of Automatic Guided Vehicle 2.3 PARKSHUTTLE AGVS OF AMSTERDAM’S SCHIPHOL AIRPORT
Fig 2.2 The ParkShuttle AGVs of Amsterdam’s Schiphol Airport.
The ParkShuttle (FROG Navigation Systems) is an automatic navigating vehicle which provides transportation for passengers. It is a people mover system. There is no driver onboard, instead a computer and an electronic navigation system do the driving. This ParkShuttle has a safety system of sensitive and intelligent sensors. The sensors scan the area in front of the vehicle and will decelerate or stop the vehicle when an unknown obstacle is detected. An additional safety feature is provided by the bumper system that brings the vehicle to an immediate halt when it is impressed. In addition, the vehicle has emergency stop buttons (both inside and outside) that can be operated by the passengers. The speed is limited to 40 km/h obtain a good ride quality. 8 The ParkShuttle vehicle runs on four rubber tires. Traction is provided by an electric motor powered by a rechargeable battery. Up to 100 km can be covered on one battery-load. It has a capacity of 10 passengers, 6 seated and 4 standees. It is easy to get into and out of the vehicle (wheelchair accessible) and provides good all-round visibility. Inside the vehicle is a console on which the passengers can indicate their destination. Each vehicle is also fitted with an information display that announces the stop at which the vehicle has arrived. The maximum load is 800 kg. The maximum vehicle weight is monitored by means of weight sensor.
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Fabrication of Automatic Guided Vehicle
2.4 LINE FOLLOWING ROBOT Line following robot is generally a wheeled mobile robot. The method of line following varied depending on the number of sensors available and the type of line to be followed. There are four methods identified including edge following, line search, line trap, and crossover. These four methods are different in number of sensors that used and also the results that will be obtained are different. With only one light sensor, the robot will have to know where the line is, or spends time searching to find it. Whereas with two light sensors, the robot is possible to remember which direction the line went. With more sensors, the result that will be obtained would be more excellent and the robot will be more intelligent. Table 2.1 Line Following Method Method
Characteristics
Edge following
Stay on the edge of the line
Line search
Stay on the line
Line trap
Keep the line between the sensors
Cross over
Move back and forth over the line
2.5 KERWIN’S LINE FOLLOWING ROBOT
Fig 2.3 The Kerwin’s line following robot using three matched IR transmit/receive pairs The Kerwin’s line following robot (ranchbots) is a design with Futaba S-148 servo motors mounted to the bottom of the plexiglass. It has three wheels with the front wheel is the omni-directional wheel. The sensor system consists of an array of three matched IR transmit/receive pairs mounted on a circuit board that can be raised or lowered to fine tune the sensitivity. It uses the Atmel microcontroller as the controller part. The microcontroller takes input from sensor array and drives the servo motors in response. 13
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Fabrication of Automatic Guided Vehicle
CHAPTER III COMPONENTS SELECTION & DESCRIPTION 3.1 DESIGN OBJECTIVES In nowadays AGV has a greater influence in the production field. Why we prefer this system is mainly because of its accuracy to transport goods, avoiding accidents at industrial zone, decreasing production overall cost etc.
In our project the important factor is that, we give an additional functions to AGV, i.e. we provide a lifting mechanism to take loads from station to station. The lift will actuate at those particular stations using sensors. Also we provide a sensor which detects the objects in the paths to avoid collision with those objects, by stopping the vehicle and moves after the when object leaves the path.
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Fabrication of Automatic Guided Vehicle 3.2 DESIGN CONSIDERATIONS In design problems many decision variables arise. The impact of decisions on mutual interactions and performance might be difficult to predict. It might be hard to decide on one thing without considering other decision variables. At least the following tactical and operational issues have to be addressed in designing an AGV system • Flow path layout • Traffic management: prediction and avoidance of collisions and deadlocks • Number and location of pick-up and delivery points • Vehicle requirements • Vehicle routing • Vehicle scheduling • Battery management
A flow path layout compromises the fixed guided paths on which vehicles can travel to the various pick-up and delivery points of loads. Traffic management is required to avoid collisions and deadlock situations in which two or more vehicles are blocked completely. To ensure that loads are transported in time, sufficient vehicles should be available and the right vehicle should be dispatched to the right load.
This layout is usually represented by a directed network in which aisles intersections and pickup and delivery locations can be considered as nodes. The arcs represent the guide path the AGVs can travel on. Directed arcs indicate the direction of travel of vehicles in the system. The layout of this flow path directly influences the performance of the system. In our project we just mark two stations only. One loading and one unloading station. The carrier moves in the loop which connects these two stations.
In controlling and designing AGV systems the problem of prevention of AGV collisions and deadlocks should be addressed. By attaching sensors on AGVs, physical collisions can be avoided. An AGV should have the ability to avoid obstacles and the ability to return to its original path without any collisions. We had fabricated only one AGV. So the traffic management has only less important in our case. But while using more than one carrier we should take care about them. 15
Department of Mechanical Engineering
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Fabrication of Automatic Guided Vehicle
To determine an optimal AGV’s system, capable of meeting all requirements, many factors have to be taken into account. Several of these factors are: • Number of units to be transported • Points in time at which units can be or need to be transported • Capacity of the vehicle • Speed of the vehicle • Costs of the system • Layout of the system and guide path • Traffic congestion • Vehicle dispatching strategies • Number and location of pick-up and delivery points
If AGVs use batteries, frequent battery changing might be required. McHaney (1995) presents an overview of AGV battery technology. The time required for replacing or charging batteries can impact the number of vehicles required. Simulation results from McHaney (1995) indicate a significant increase in the number of AGVs required while incorporating battery management issues in the simulation study compared to neglecting these issues in the studies. Furthermore, the time required for charging batteries impacts throughput, congestion and costs.
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Fabrication of Automatic Guided Vehicle 3.3 COMPONENTS OF AGV
1. MECHANICAL PARTS The Mechanical components includes, 1. Chassis 2. Steering system 3. Lift mechanism Chassis
Act as a frame for attaching other components
Carry the load of other components and the payload.
Act as sacrificial component to prevent damage of expensive payload in case of accidents
Steering System Steering system is for steering the AGV. The two individual motors are directly attached with the wheel for steering Lifting Mechanism Lifting mechanism is one of the main part of AGV, the lifting surface moves upward and downward at specified stations. And carry the load during load transfer.
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Fabrication of Automatic Guided Vehicle 2. ELECTRICAL COMPONENTS Electrical components include the motor and the power supply unit for the motor, sensoring unit
3. ELECTRONIC COMPONENTS Electronic components provide sensing, logical decision and control of the vehicle. It includes microcontroller, which is the brain of the vehicle for the decision logic, the motor driver as both sensing and control of motor, regulator ICs, LCD Display unit, sensors for sensing the path, position of loading and unloading stations, detect object in the path etc.
4. SOFTWARE COMPONENTS Computer is used for making and implementing program for the microcontroller, using embedded computer programming language.
For this project we use Arduino Uno
microcontroller board based on the ATmega328 .The Arduino Uno can be programmed with the Arduino software.
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Fabrication of Automatic Guided Vehicle 3.4 MECHANICAL PART 3.4.1 CHASSIS The chassis is fabricated from Acrylic sheet. This is done for ease of fabrication, and to reduce the overall weight. It was designed in Catia; part of fabrication was outsourced due to unavailability of precision cutting tools. The chassis was designed to take a static load of 3kg. The Top part of chassis has lots of drilled holes which serves as holes for bolting other parts and reduce the weight of the chassis. The Holes are arranged in a zigzag linear arrangement so that the decrease in strength of chassis is not considerable. The flange which holds the motor was designed using Aluminium and is bolted to the chassis. So that the driving motors can easily accommodate below the chassis. The chassis incorporates hole for attaching front globe wheel, and also for attaching the lift structure
Fig 3.1 Chassis of AGV Table 3.1 Technical Data of Chassis Features Length Breadth Height Material Maximum load Mounting Holes
Data 300mm 160mm 62mm Colored Acrylic sheet, Aluminum 14×3mm ø Holes for general mounts 2×8mm ø Holes for motor 1×10mm ø Hole for switch
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Fabrication of Automatic Guided Vehicle 3.4.2 STEERING SYSTEM The steering system used in the model is of differential type. A differential wheeled vehicle is a vehicle whose movement is based on two separately driven wheels placed on either side of the body. It can thus change its direction by varying the relative rate of rotation of its wheels and hence does not require an additional steering motion. It allows the turning center to be on the vehicle body thus the ability to rotate on the point
Fig3.2 Differential Steering
If both wheels rotate at the same speed and in the same direction, the robot will move in a straight line.
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Fig 3.3 Small radius turning
If one of the wheels is stopped, while the other continues to rotate, the robot will pivot around a point centred approximately at the mid-point of the stopped wheel.
Table 3.2 Steering Specifications Feature Wheel Base Wheel Diameter Track Distance Material Turning radius
Data 180mm 70mm 170mm Rubber and plastic 190mm
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Fabrication of Automatic Guided Vehicle 3.4.3 LIFTING MECHANISM The lift is the main component of this AGV. The lift takes and gives loads at specific stations. The vehicle under stands the stations using sensors. Lift is attached in the front portion of the chassis. The power for lift is transmitted from a motor using a threaded shaft. The lift consists of mainly two plates. One is centrally drilled and tapped. Second plate is attached with the lower one, using bolts, at a distance. The shaft of the motor drilled axially and made internal threads using tap. Both the plates moves in between two guide ways. The threaded shaft is passed through the centrally tapped hole of lower plate. During the rotation of shaft the lower plate moves up or down. And the upper plate moves according to it. The time for the rotation is limited for few seconds. It can be adjusted by making changes in the microcontroller program. A magnet is attached above the upper plate, which helps to hold the items to be lift, which have magnetic behavior.
Fig 3.4 Lifting using threaded shaft
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Fabrication of Automatic Guided Vehicle In order to reduce the overall cost and weight of the AGV, we used acrylic sheets for the manufacturing of lifting surfaces, Aluminum C channels for the guide ways in between the plates moves are used for the fabrication.
4
1
2 3
Fig 3.5 Structure of lift 1. Guide ways 2. Threaded shaft 3. Lower plate 4. Upper plate
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Fabrication of Automatic Guided Vehicle 3.5 ELECTRICAL COMPONENTS 3.5.1 DC MOTOR 100 RPM DC Motor with Gearbox generally used for robotic application are used for the driving mechanism, steering mechanism and lifting mechanism. We can adjust it to desired RPM using gear box. Very easy to use. It is excellent for line tracking robotic application.
Fig 3.6 DC Motor with Gear box
Table 3.3 Motor Specifications Feature Supply voltage Speed Shaft Diameter Weight Torque No-load current Load current
Data 12V DC 100 RPM with gear box 6mm 125gm 12Kgcm 60mA(Max) 250ma(Max)
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Fabrication of Automatic Guided Vehicle 3.5.2 BATTERY The power required for the entire working process is given by a Rechargeable valve regulated Lead-Acid battery. The power from the battery is split it into two and one part is given to microcontroller, display unit, driving unit and other part is given to lifting motor.
Fig 3.7 Battery
Table 3.4 Battery Specification Features Speed Voltage Torque No load current Load current
Data 100rpm 12V DC 12Kg-cm 60mA 250mA
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3.6 ELECTRONICS COMPONENTS
3.6.1 MICROCONTROLLER A microcontroller (µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications. We use ATmega 328 in our AGV.The Atmel®AVR® ATmega 328 is a low-power CMOS 8-bit microcontroller based on the AVR RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega8 achieves throughputs approaching 1MIPS per MHz, allowing the system designed to optimize power consumption versus processing speed.
The reasons for using ATmega 328 are:
Low cost
Easy to program
High-performance, Low-power
Fully Static Operation
High Endurance Non-volatile Memory segments
Power-on Reset and Programmable Brown-out Detection
Internal Calibrated RC Oscillator
External and Internal Interrupt Sources
High stress value
Five Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, and Standby
I/O and Packages
23 Programmable I/O Lines
28-lead PDIP, 32-lead TQFP, and 32-pad QFN/MLF
Operating Voltages 2.7V - 5.5v to 4.5V - 5.5V 26
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Fabrication of Automatic Guided Vehicle The Microcontroller is programmed with the required program to accept the data from the sensing unit, interpret it, and give responses to the driving and lifting mechanism in very small time interval.
Table 3.5 Specification of ATmega 328 Type: Flash I/O pins Minimum/Maximum Voltage: Maximum current: Number of PORTS No of channels Bus width Oscillation Speed PWM
28Pin DIP Package 32K Bytes 23 Pins 1.8/5.5V 20mA 4 6 10Bit 20Mhz 6
Table 3.6 Important Connections PIN Name
Pin No
Vcc
7
GND
8,22
XTAL1
9
XTAL2
10
RXD/PD0
2
PB4
16
PB5
19
PB6
9
PB7
10
Reset
1
Rxd
2
Txd
3
AVCC
20
AREF
21
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Fig 3.8 ATmega 328 microcontroller
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Fabrication of Automatic Guided Vehicle 3.6.2 MOTOR DRIVER It is an electronic circuit which enables a voltage to be applied across a load in either direction. It allows a circuit full control over a standard electric DC motor. That is, with an Hbridge, a microcontroller, logic chip, or remote control can electronically command the motor to go forward, reverse, brake, and coast. A "double pole double throw" relay can generally achieve the same electrical functionality as an H-bridge, but an H-bridge would be preferable where a smaller physical size is needed, high speed switching, low driving voltage, or where the wearing out of mechanical parts is undesirable. The term "H-bridge" is derived from the typical graphical representation of such a circuit, which is built with four switches, either solid-state (e.g., L293/ L298) or mechanical (e.g., relays). In our AGV we use the driver IC L293d. There are two driver ICs are provided in the design, because three motor are in the AGV. One driver circuit is connected to the two motors of driving mechanism. And second one is used for the motor which is incorporated with the lift.
Fig 3.9 Motor Driver (L293D) 29
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Fabrication of Automatic Guided Vehicle The following figure shows the connection of the driving mechanism.
Fig 3.10 L293D connected with two motors To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage. This device is suitable for use in switching applications at frequencies up to 5 kHz.
In the lifting section one motor is utilized. So the one side of the driver circuit is not connected.
Fig 3.11 L293D connected with one motor
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Fabrication of Automatic Guided Vehicle In the both end of a motor voltage is always 5v. So there no potential difference between the two terminals of the motor. Therefore there is no current flow between terminals, and motor will not work. During the operation at one terminal the voltage becomes zero volts. And thus the current flows through the motor and it works. We can rotate the motor in two directions.
In the driving mechanism, in our design one direction of rotation of motor is needed. Because the AGV doesn’t wants to moves in reverse. But the connection is made in such a way that both two motors rotate in opposite direction. i.e., the motor which rotates the right wheel in clockwise direction and that of left wheel rotates in counter clockwise direction.
But the lifting motor wants to rotate in the both directions. For the clock wise rotation lift move up and for counter clockwise it moves down. The movement of the lift surface depends on the internal thread of the lower plate also.
Fig 3.12 Circuit connection of driving motor
Fig 3.13 Connection of lifting motor for clock wise and counter clock wise rotation 31
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Fabrication of Automatic Guided Vehicle To control motor speed we can use pulse width modulation (PWM), applied to the enable pins of L293d driver. PWM is the scheme in which the duty cycle of a square wave output from the microcontroller is varied to provide a varying average DC output.
Fig 3.14 PWM
Table 3.7 Technical Specification of L293D Symbol Vs Vss Vi Ven Io Ptot Tstg,Tj
Parameter Supply Voltage Logic Supply Voltage Input Voltage Enable Voltage Peak Output Current Total Power Dissipation at Tpins=90ᵒc Storage and Junction Temperature
Data 36V 36V 7V 7V 1.2A 4W -40 to 150 ᵒc
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Fabrication of Automatic Guided Vehicle 3.6.3 REGULATORS Mainly two types of voltage regulators are used in the design. One is variable and the next is not. The non variable belongs to 78 series. And variable is LM series. The main supply is 12V. But we need only 5V. It is made possible using these regulators 3.6.3.1 7805 Regulator It is the one of the important electronic part. The motor, driving IC, microcontroller etc need only 5V for their operations. Before the supply is given to these circuits it is given to the 7805 voltage regulator. It reduces the voltage from 12V to 5V.
Fig 3.15 7805 REGULATOR
The main features of these regulators are:
Internal Thermal Overload Protection.
Internal Short Circuit Current Limiting.
Output Current up to 1.5A.
Satisfies IEC-65 Specification.
Table 3.8 Maximum Ratings of 7805 Characteristic Input Voltage Operating Junction Temperature Storage Temperature Max. junction Temperature
Symbol Vin Tj
Rating 35V -40 to 150 ᵒc
Tstg Tj(max)
-55 to 150 ᵒc 150 ᵒc 33
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Table 3.9 Technical Specifications of 7805 ELECTRICAL CHARACTERISTICS (VIN=10V, IOUT=500mA, 0ᵒc≤ Tj≤ 125ᵒc) Characteristic Data Output Voltage 4.8 to 5.2 V Input Regulation 100 mV Output Noise Voltage 50 microVrms Ripple Rejection Ratio 78dB Drop Out Voltage 2.0V
3.6.3.2 LM317 VARIABLE REGULATOR There are five variable regulators are used in our design. Its used for reduce the voltage to the motor and to sensors. It will helps to reduce the speed of rotation of the motor and thus we can adjust the speed of the vehicle.
Fig 3.16 LM317 circuit
Table 3.10 Technical Specificationsof LM 317 Parameter Line Regulation Load Regulation Thermal Regulation Current Limit Ripple Rejection Ratio Long term stability RMS Output Noise
Data 0.01 %/V 0.1%/V 0.04%/W 2.2A 65dB 0.3% 0.003% 34
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3.6.4 INFRARED SENSORS IR Sensor is one of the important parts. Path detection and obstrucle detection is done with the help of IR Sensors. There are five IR Sensors are in our AGV. Out of them four are used for the path detection and rest of one is used for obstrucle detection. IR sensor have a transmitter and a receiver port.
The strength of signal reached at the receiver port after the reflection of light is used to detect the path. Path is marked in the black background by white lines. Sensor detect the white line by the strength of IR wave. The reflected wave from white line has high strength than that of from black. TSOP1730 are used in the design.
Fig 3.17 IR for Path Detection
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Fabrication of Automatic Guided Vehicle The IR pair circuits are shown in the figure give below:
Fig 3.18 IR pair Circuit
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Fabrication of Automatic Guided Vehicle The main features of this IR pair are:
Photo detector and preamplifier in one package
Internal filter for PCM frequency
Improved shielding against electrical field disturbance
TTL and CMOS compatibility
Output active low
Low power consumption
High immunity against ambient light
Continuous data transmission possible (up to 2400 bps)
Table 3.11 Technical Specifications of IR pair Characteristics Supply Voltage Output Voltage Junction Temperature Operating Temperature Power Consumption Irradiance Directivity
Data -0.3 to 6.0V -0.3 to 6.0V 100 ᵒc -2.5 to 85ᵒc 50mW 30W/m² ±45º
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Fabrication of Automatic Guided Vehicle 3.6.5 MAGNETIC SENSOR Magnetic sensors or magnetic switches are electronic switches that close under the magnetic field. In this AGV there are two magnetic sensors. XEN-1210 is the sensor used in this design.
The XEN-1210is a CMOS linear magnetic field sensor with a very low offset. It uses Xensor's patented high performance spinning-current Hall-plate technology, a precision amplifier and a sigma delta AD converter, and offers full digital control and communication through a SPI serial bus. The device does not need calibration and in contrast to low-offset AMR sensors does not use a set/reset method. It has no hysteresis and is indestructible by high magnetic fields. It does not need any external components and is truly a one-chip solution.
These sensors are used for the purpose of position detection. It is used for detect the loading and unloading station. The sensor is attached with the vehicle at two different positions. Magnets are placed in such a way that one sensor close when the vehicle comes to the loading station. And when that switch close lift operates and moves up. After loading the vehicle moves along the path. When it reach the unloading station the next sensor close and lift operates to move down. The main features of this sensor are
Single axis magnetic measurement One chip solution 15nT resolution Wide magnetic field range (±63mT) No magnetic hysteresis Low voltage operation (2.5V to 3.3V) Single supply -40°C to 125°C Temperature Range
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Fig 3.19 Magnetic sensor
It’s a glass capsule, inside the tube there are two reed blades, which is connected to the voltage terminal. Reed blades are placed over lapped, but not connected. There is a contact gap between the blades. And the tube is filled with inert gas. Table 3.12 Technical Specifications of Magnetic sensors Specifications Data VDD 3.3V Field Range ±63mT Resolution(24 bits) 7.5nT/LSB Hysteresis 10nT Noise 55nT/Hz^½ Temperature range -40 to 125 ºC
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Fabrication of Automatic Guided Vehicle 3.6.6 DISPLAY UNIT It’s just to display the inputs and outputs of the system. It mainly displays the inputs of path sensing IR sensors and working of the vehicle. Inputs are displayed using numbers. JHD162A SERIES is the display unit used in the AGV.
Characteristics: Char. Dots 5 x 8 Display content 16 CHAR x 2ROW Driving mode 1/16d Available types: TN STN (yellow green) Reflective with El or Led Backlight EL/100VAC 400HZ LED/4.2VDC
Table 3.13 Technical Specifications of Display unit Parameter Supply Voltage Input High Voltage Output High Voltage Operating Voltage
Data 5.0V 2.2V 2.4V 1.5mA
Table 3.14 Pin Configurations Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Connection Vss Vcc VEE RS R/W E DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 LED+ LED-
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Fig 3.20 Application Circuit of display unit
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Fabrication of Automatic Guided Vehicle 3.7 SOFTWARE COMPONENTS We use ATmega328 microcontroller in this AGV. The microcontroller is the brain of the vehicle. So the programming of the microcontroller has great imporantance in the working. Arduino software is used to program the microcontroller. Program is burned using special microcontroller board. For this ATmega328 microcontroller Arduino Uno board is used.
The Arduino Uno is a microcontroller board based on the ATmega328 . It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.
Arduino is an open-source electronics prototyping platform based on flexible, easy-touse hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.
The program is written in the Arduino software using special commands. The main feature of this software is that we can run the program before burning in to the microcontroller. And we can check the function. It will helps to make changes in the program, in easy way.
The program is written in such a way that when the vehicle is in on condition, the four line detecting sensors works and detect the line. If the middle sensors close, the two driving motor rotates. If left sensors close right motor works, if right sensors close left motor works. If the object detector sensor closes, all the two motors stops whatever may be the line detecting conditions. When the right magnetic switch closes the third motor rotates in clockwise, when left switch closes it rotates in anti clockwise direction. All the input signals for the line detection and position detection are shown in the LCD display. Also the working status is shown in the display
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3.8 PROGRAM SOURCE CODE #include
int a = 0; int b = 0; int c = 0; int d = 0; int e = 0; int f = 0;
LiquidCrystal lcd(8, 9, 10, 11, 12, 13); void setup() { Serial.begin(9600);
pinMode(A0, INPUT); pinMode(A1, INPUT);
pinMode(A2, INPUT); pinMode(A3, INPUT); pinMode(A4, INPUT); pinMode(A5, INPUT);
pinMode(7, OUTPUT); pinMode(6, OUTPUT); pinMode(5, OUTPUT); 43
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Fabrication of Automatic Guided Vehicle pinMode(4, OUTPUT); pinMode(2, OUTPUT); pinMode(3, OUTPUT);
lcd.begin(16, 2); lcd.clear(); lcd.setCursor(0, 0); lcd.print("L F Robot"); delay(1000); }
void loop() { a = digitalRead(A5); b = digitalRead(A4); c = digitalRead(A3); d = digitalRead(A2); e = digitalRead(A1); f = digitalRead(A0);
lcd.setCursor(0, 0); lcd.print("A:"); lcd.setCursor(2, 0); lcd.print(a); lcd.setCursor(4, 0); lcd.print("B:"); lcd.setCursor(6, 0); 44
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Fabrication of Automatic Guided Vehicle lcd.print(b); lcd.setCursor(8, 0); lcd.print("C:"); lcd.setCursor(10, 0); lcd.print(c); lcd.setCursor(12, 0); lcd.print("D:"); lcd.setCursor(14, 0); lcd.print(d); delay(100);
if((a==LOW && b==HIGH && c==HIGH && d==LOW) || (a==HIGH && b==LOW && c==LOW && d==HIGH)) { lcd.clear(); lcd.setCursor(0, 1); lcd.print("Forward"); Serial.print("Forward\t");
digitalWrite(3, HIGH); digitalWrite(2, HIGH);
digitalWrite(7, HIGH); digitalWrite(6, LOW ); digitalWrite(5, HIGH); digitalWrite(4, LOW ); delay(200);
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else if((a==LOW && b==LOW && c==HIGH && d== LOW ) || (a==HIGH && b==HIGH && c==LOW && d== HIGH )) { lcd.clear(); lcd.setCursor(0, 1); lcd.print("Left"); Serial.print("Left\t");
digitalWrite(3, HIGH); digitalWrite(2, HIGH);
digitalWrite(7, HIGH); digitalWrite(6, HIGH); digitalWrite(5, HIGH); digitalWrite(4, LOW ); delay(200); }
else if((a==LOW && b== HIGH && c==LOW && d==LOW) ||(a==HIGH && b==LOW && c==HIGH && d==HIGH)) { lcd.clear(); lcd.setCursor(0, 1); lcd.print("Rihgt"); Serial.print("Rihgt\t");
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Fabrication of Automatic Guided Vehicle digitalWrite(3, HIGH); digitalWrite(2, HIGH);
digitalWrite(7, HIGH); digitalWrite(6, LOW ); digitalWrite(5, HIGH); digitalWrite(4, HIGH); delay(200); }
else if((a==HIGH && b==HIGH && c==HIGH && d==HIGH )|| (a==LOW && b==LOW && c==LOW && d==LOW) ) { lcd.clear(); lcd.setCursor(0, 1); lcd.print("Stop"); Serial.print("Stop\t");
digitalWrite(3, HIGH); digitalWrite(2, HIGH);
digitalWrite(7, HIGH); digitalWrite(6, HIGH); digitalWrite(5, HIGH); digitalWrite(4, HIGH); delay(200); }
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Fabrication of Automatic Guided Vehicle if(f==HIGH) { while(1) { lcd.clear(); lcd.setCursor(0, 1); lcd.print("arm up");
digitalWrite(7, HIGH); digitalWrite(6, HIGH); digitalWrite(5, HIGH); digitalWrite(4, HIGH);
digitalWrite(3, LOW); digitalWrite(2, HIGH); delay(18000);
digitalWrite(7, HIGH); digitalWrite(6, LOW ); digitalWrite(5, HIGH); digitalWrite(4, LOW ); delay(200);
break; }} if(e==HIGH) 48
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Fabrication of Automatic Guided Vehicle { while(1) { lcd.clear(); lcd.setCursor(0, 1); lcd.print("arm down");
digitalWrite(7, HIGH); digitalWrite(6, HIGH); digitalWrite(5, HIGH); digitalWrite(4, HIGH);
digitalWrite(3, HIGH); digitalWrite(2, LOW); delay(18000);
digitalWrite(7, HIGH); digitalWrite(6, LOW ); digitalWrite(5, HIGH); digitalWrite(4, LOW ); delay(200); break; }} delay(100); }
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CHAPTER IV
DEVELOPED PROTOTYPE
4.1 STRUCTURE The vehicle is designed in such a way that, have stability during loading and working. The lifting parts are provided in the front position. It comes above the front globe tyre. The electronic and electrical parts are situated the rest of surface. Motor for driving are provided in the rear region. Hence during dynamic loading the vehicle will be stable. The structure of the vehicle is shown in the figure,
Fig 4.1 Front view of AGV 50
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Fig 4.2 Top view of AGV
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4.2 SENSORS POSITIONS The positions of sensors are important factor to detect the position. The sensors for detecting the path are situated after the front wheel. But the obstruction detection sensor is placed below the chassis, and in front of the front tyre. There are four IR sensors used to detect the path. They are along a line parallel to the breadth. And side sensors are placed at an equal distances from middle sensors.
The width of the white line is little more than the distance between two sensors. All the four sensors were give different movements during different combination. The combination means closing of IR sensors. According to it the working of the driving motors change. Initially the AGV is placed above the line, in such a way that the two middle sensor comes above the white line.
During the straight path the middle sensors close, the two motors run in forward direction with equal speed. Thus the vehicle moves in the straight line. When two of the left side close left motor stops and right works. Then the AGV takes a left turn depending upon the curvature. And when two right side sensors close,right side motor stops and the left works. Thus the AGV takes a right turn.
Fig 4.3 IR Sensors positions of AGV 52
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The design of path is very important for an AGV. The magnetic sensors are placed below the driving motors. Two magnets are used to detect the loading and unloading station. There is a particular distance between those sensors and the lift. The loading stand should be placed about at that distance from the magnet. Lifting up sensor is placed below the right motor. So one of the magnet is placed in the right side of the path. Lifting stand is placed about a distance from that magnet. The magnets are placed in such a way that any one of its poles comes to top. Only then the magnetic switch works.
Fig 4.4 Magnetic sensors positions
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Fabrication of Automatic Guided Vehicle 4.3 FLOW CHART
Not Detect
Detect
Off
On
Fig 4.5 Flow chart
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4.4 BLOCK DIAGRAM
LCD POWER SUPPLY
OBJECT DETECTOR SENSOR
MOTOR
MOTOR 1
DRIVER MOTOR 2 LINE DETECTOR SENSOR
MICROCONTROLLER MOTOR DRIVER
MOTOR 3
MAGNETC REED SENSOR
Fig 4.6 Block Diagram
Block diagram is a diagram of a system, in which the principal parts or functions are represented by blocks connected by lines that show the relationships of the blocks. They are heavily used in the engineering world in hardware design, electronic design, software design, and process flow diagrams. In this diagram direction of all arrows are either from or to the microcontroller.
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4.5 CIRCUIT DIAGRAM
Fig 4.7 Circuit Diagram
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Fabrication of Automatic Guided Vehicle The fully fabricated prototype of Automatic Guided Vehicle has possessed the intelligences such as following a particular line, loading and unloading at particular stations and collision avoidance etc.
Fig 4.8 Fully Developed Prototype
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Fabrication of Automatic Guided Vehicle 4.6 THEORETICAL AND LOGICAL CALCULATIONS
Torque of DC motor used, T
= 12Kg-cm = 1.1772 N-m
Speed of motor, N
= 100 RPM
Angular Velocity, ω
= 2ΠN/60 = (2*Π*100)/60 = 10.47 rad/sec
Physically Power is the rate of doing work. For linear motion, power is the product of force multiplied by the distance per unit time. In the case rotational motion, the analogous calculation for power is the product of Torque multiplied by the rotational distance per unit time
=T*ω
Rotational Power, P
= 1.1772*10.42 =12.33 W No. of motors available for driving mechanism = 2 motors So total power available for driving = 2* 12.33 = 24.66 W There is only one motor is used for the lifting purposes, So maximum power available at lifting mechanism
= 12.33 W
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Fabrication of Automatic Guided Vehicle We have relation, v = r*ω Where, v= Linear velocity R= Radius ω= Angular velocity
Diameter of shaft, d= 0.6cm Radius of shaft, r= 0.3cm =0.3*10^ (-2) ∴ Linear velocity, v = (0.3*10^ (-2)) * 10.47 = 0.03141 m/s = 3.14 cm/s
Weight of carrier = 1.495 Kg Width of line marking= 4.3cm
For Lifting section, Shaft Torque, Tsh = output/2ΠN = 1.1772/ (2Π*100) = 1.8735* 10^ (-3) N-m
Force * Distance = Torque Distance to be lifted, l= 5mm Force * (5*10^ (-3)) = 1.8735*10^ (-3) Force, F = 3.75 N
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Fabrication of Automatic Guided Vehicle Force, F= Load * g Acceleration due to gravity, g= 9.81m/ Load = 3.75/9.81 = 0.383 Kg ≈400 gms
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4.7 BILLING
NO
ITEM
1
DC Motor
2
Micro Controller
3
NO. ITEM
3
COST/ITEM
TOTAL COST,(R.S)
200
600
1
350
350
Driver IC
2
100
200
4
LCD Display
1
350
350
5
IR Sensors
5
175
875
6
Magnetic Switch
2
80
160
7
Acrylic Sheet
1
160
160
8
Aluminum channel
1
30
30
9
Battery
1
400
400
10
Fasteners
25
25
11
Magnets
3
25
75
12
Sticking Glues
2
30
60
13
Electronic Components
14
Arduino board
250
1
1350
Total
1350 4885
Table 4.1 Billing Table
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Fabrication of Automatic Guided Vehicle
CHAPTER V CONCLUSION The AGV is a productivity increasing feature in a factory. During the manufacturing of this AGV we had found many of intelligence that can be given to it. We provide the basic functions like line following and collision avoiding. And the main function, transportation of goods from station to station. The followings are the main features of the prototype which we fabricated. 1. Speed of delivery 2. Adjustment of vehicle speed 3. Flexibility of path 4. Adaptive to changes in factory layouts 5. Avoid collision with other objects 6. Reduction in labour cost 7. Reduction in running cost compared to conveyer systems 8. Ability to add sensors to detect the payload conditions 9. Ability to adjust the lifting time 10. Continues cycle of working 11. Conditions for line following can be change easily
Automatic Guided Vehicle can be used in a wide variety of applications to transport many different types of material including pallets, rolls, racks, carts, and containers. AGVs excel in applications with the following characteristics: Repetitive movement of material over a distance Regular delivery of stable loads Medium throughput/volume When on time delivery is critical and late deliveries are causing inefficiencies Operation with at least two shifts Archive Systems Cross Docking Distribution High Density Storage 62
Department of Mechanical Engineering
ACET
Fabrication of Automatic Guided Vehicle High Speed Sortation Material Flow and Transport Production and Manufacturing Delivery Systems Production and Manufacturing Support Systems Warehouse Management and Control Work-In-Process Buffers
The fabricated models have following advantages while comparing with the existing models of this kind. The analyzing of advantages helps to motivate the fabrication of AGV in the manufacturing industries. The important advantages of the prototype are given below Reduce manpower Increase productivity Eliminate unwanted fork trucks Reduce product damages Maintain better control of material management Traffic control is not needed in this system because of single carrier Suitable to transfer frames
Each of the machines has their own merits and demerits. During the production we had faced many problems. Much of them were solved during the assembling. But still some of them stand here, which can’t have to remove. The followings are the limitations of the prototype fabricated:
Installation cost is very high.
AGVs are fragile and should be handled with care.
Regular care, inspection and maintenance needed
Should be recharged periodically
AGV will stop delivery when it is forced off the path.
Battery should be recharged during intervals.
Sun light affect the movement.
63
Department of Mechanical Engineering
ACET
Fabrication of Automatic Guided Vehicle
REFERENCES www.elsevier.com/locate/ejor/Survey of research in the design and control of automated guided vehicle systems
www.jbtcorporation.com/en/Solutions/Automatic-Guided-Vehicles
http://www.arduino.cc/
www.atmel.com/devices/atmega328
www.sunroms.com
Automation, Production Systems, And Computer Integrated Manufacturing, By Groover, Mikell.P, ISBN 8120334183
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Department of Mechanical Engineering
ACET
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