seminar on agv
TRANSCRIPT
Emergency stop
Status indicator
Obstacle sensor
Protective bar
Flasher
Protective bar
Photobarrier
Audible signal
Side protectionrails
Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CHAPTER 1
INTRODUCTION
An automated guided vehicle system is a material handling system that
uses independently operated , self propelled vehicle that are guided along defined
pathways on the floor. The vehicles are powered by means of on board batteries
that allow operation for several hours (8-16 hrs.) between recharging. Guidance is
achieved by using sensors on the vehicles that follow the guide wires. The vehicle
is controlled by an off board controller or a micro- processor. This controller
sends commands to the vehicle such as identification of load, its destination and
other special instructions. An AGV system provides a material handling system
i.e. both flexible and readily adaptable to either production or production changes.
Figure 1.1
Basic Diagram of Automated Guided Vehicle
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
AGV systems are originally developed for the distribution of material in
warehouse environments although this is an imp. use, two major growth areas
have been evolved the movement of material to and from production areas in
manufacturing facilities, reflecting manufacturing work lifts and use of carriers of
work in progress in assembly plants, replacing serial type asynchronous or fixed
index assembly conveyor system and small packages, in hospitals to deliver
meals, and for material handling. (Miller, 1987).
AGV system were first introduced in 1950 in USA and later in Europe in
early 1960, the technology caught on much faster in Europe.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CHAPTER 2
TYPES OF VEHICLES
2.1 Towing Vehicles:
These vehicles consist of an AGV with no load carrying facility but
with a hitch or tow bar that can pull trailers, carts pallets jacks and wheeled racks.
They are used where large volume of product to be moved or in retro fit
applications where product in historically been moved by trailers. These vehicles
can move loads up to 50,000 pounds.
Figure 2.1
Towing type Automated Guided Vehicle
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
2.2 Unit load Transporters:
These vehicles are designed to carry individual loads. Unit load
transporter can have an extremely versatile deck design, which permits them to be
equipped with rollers, belt conveyors, power lifts, special fixtures, or on board
robot arm, These AGV can be either bi-directional or unidirectional and are used
in house as well as on factory flowers. Unit load transporter scan lift loads
ranging between 12,000 to 60,000 pounds.
Figure 2.2
Unit Load Transporter Type Automated Guided Vehicle
2.3 Standard Automatic Guided pallet Trucks:
These vehicles are designed to service palletized loads to and from
floor level positions. The shadow fork region has limited fork travel and is
designed to move pallets to and from floor positions exclusively. The fork truck
version has travel up to 20 feet and can move pallets both at floor level and on
stands or racks.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
2.4 Assembly Line Vehicles:
These vehicles have a fixture on board that accept the frame initial
parts of the product that is to be assembled. The vehicle is routed through the
various manufacturing stations of the factory where parts and assembly are added
to the product. these AVG can provide total automatic transfer of material these
are known as material handling system on automated assembly line. They can
skip assembly section if required in particular section breaks down.
2.5 Light Load Transporters:
These vehicles are design to carry boxes, baskets, small parts, etc.
with any other unitized container. It generally has a footprint allowing its use in
tight spaces and narrow aisles. These vehicles are used for a wide range of
functions from mailrooms to clean rooms in every type of manufacturing and
office environments.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CHAPTER 3
AGV SYSTEM COMPONENTS
Although all AGV system are different, in general they consist of
following components:
3.1 Vehicles:
The component of an AGV system that is most readily identified is
vehicle itself. The vehicle consists of a frame, batteries on board charging
unit, electrical system drive unit, steering, precision stop unit, on board
controller, communication unit, safety system and work platform.
3.1.1 Frame :
The frame is usually constructed of welded steel member with
aluminum cover Plate.
3.1.2 Batteries and charging :
AGV systems are typically powered by 24 or 48v D.C. industrial
batteries. Battery charging is accomplished by one of two techniques viz.
Opportunity charging or full cycle charging.
3.1.3 Drive unit :
The main components of motor speed controller and drive
mechanism. The driver speed controller mechanism is usually a pulse width
modulated four-quadrant servo drive unit. The carrier drive commands are
generated either through the microprocessor or at the hand control unit.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
3.1.4 Steering:
Vehicles are designed to maneuver in three different ways forward
only, forward and reverse, four directional. The major components of
power steering system are the steering antenna, the steering motors and
their controllers, steering linkage and steering limit switches.
3.1.5 Precision stop controller :
A precision stop controller is used to stop AGV with close location
accuracy at workstation and charge station. At some point before an up
coming precision stop location, the vehicle will receive a precision stop
command from off board controller or by code bar on board on the floor.
AS it approaches stop point the vehicle’s metal detector is activated and
AGV slows to the end of the plate.
3.1.6 On board controller :
The vehicle controller is used to monitor vehicle performance
through encoder data to determine position and velocity discrete digital
input, monitor functions as controls, activation of safety devices, battery
conditions, steering limit, break release, running light drive controller
status.
3.1.7 Communication Unit :
Instructions to the vehicle microprocessor are usually
generated by the Area controller and then relayed to the vehicle. The
communication System may be either continuous or discrete.
3.1.8 Safety :
Safety systems may be divided in to three specific categories,
vehicle to Vehicle, vehicle to object, and vehicle to people. The first
system uses photo cells mounted on AGVs leading edge and reflecting
material on trailing edge to avoid collision of vehicles. Vehicle to object
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
system uses bumpers , toe born limit switches, proximity sensors to
protect both vehicle and any object in AGV path generally vehicle have
warning light buzzers or toner which flashes or sounds to indicate
automatic mode.
3.2 GUIDE PATH AND GUIDENCE SYSTEM;
Generally most AGV s need guide path to follow. The guide path
techniques used are known as passive or active tracking. Passive tracking depends
upon either optical or metal detection principles where as active tracking involves
inductive principle’s.( (Taghaboni and Tanchoco, 1988; Gaskins et al., 1989))
3.2.1 Passive Tracking :
The optical method may be simply involved a light sensitive
photocell mounted on the vehicle, which follows the tape on floor. It depends
upon contrasting floor surface so that variation in reflecting light that is sensed
by photocell can be detect ed when the vehicle begins to stray from them guide
path. If guide path becomes dirty, faded, or damaged or if the ambient light
distorts the light level sensed, the vehicle may stray from guide path.
A variation of optical method is lightening patented optical system. It
is based on bonding fluorescent particles to the floor surface and stimulating
these particles with ultra violet light and causing them to omit a generated light
in the sensing head an oscillation mirror scans the guide path and reflect the
generated light in to photo reflector, which intern relays signal to
microprocessor.
The other passive tracking techniques involve vehicle with metal detecting
sensor s following a stainless steel ribbon. Tran scar patterned guidance system
consists of two sensors packs each containing five sensors and located at each
end of AGV. The three central sensors allow the vehicle to center itself on the
guide path. The two remaining sensors assist the vehicle in transverse curve.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
The sensor locates the presence of guide tape and transmit this information to
the onboard microprocessor.
3.2.2 Active Tracking :
Active tracking involves use of guide wire and most commonly
used Technique in industry. A low voltage ( less than 40 v), low current (less
than 400 ma), low frequency (Ñ to 15 kHz.) and signal is conducted through a
wire buried in a slot in the floor. A small electromagnetic field is radiated
from the wire and two inductive type sensors are compared and as long as
they are equal, the vehicle is centered on the guide path if vehicle begins to
stray, signal magnitudes sensed are no longer equal and sensor difference is
used to steer the vehicle back on the guide path.
3.3 Floor and system controls:
The controller is the brain of the whole system, trying the vehicle
to the guide path and integrating the system. Not only does it control the AGV
system but it also integrates with automatic assembly facility. The AGV
system itself will usually contain three levels of controller architecture,
vehicle control system, floor control system and vehicle on board processor.
3.3.1 vehicle control system :
The top level of vehicle control system often
communicates with and under the control the facility’s host computer. Most of
the decision making takes place at this level as it oversees the system
operation. The vehicle system stores in memory exact vehicle location at all
the times and provides network access.
3.3.2 Floor control Unit :
This level is referred to as the data concentrator and acts as
traffic manager and communicating directly with the vehicles and providing
them with formatted detailed commands.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
3.4 Vehicle processor :
. Generally the vehicle processor knows the vehicle location, and it
can interpret commands received from floor control unit and can monitor on
board safety devices. The two type of vehicle control processors are intelligent
type and non-intelligent type
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CHAPTER 4
AGV GUIDENCE & CONTROLES
INTRIDUCTION
Some AGV system use vehicles, which have sophisticated
microprocessor on board and are known as smart or intelligent vehicles. Other
systems have minimal vehicle computing ability and use a central computer
for all process. In such systems central computer decides location, direction,
proper rout and path of the vehicle. This is accomplished by turning on and
off the path at decision points or by commanding vehicle to follow a particular
frequency. All decision is making is made by central computer in smart
vehicles. The central computer dispatches the vehicle to next location, though
it’s on board microprocessor, the vehicle it self makes decision as to which
path it takes.
(et al. (1990) and Smith et al. (1992))
Figure 4.1
Controlling Of Automated Guided VehiclePage 11 of 20
AUTOMATED GUIDED VEHICLE
Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
4.1 method of Programming
the smallest system uses manual programming to direct the vehicle
to specific destination and to dispatch the vehicle. These system ranges from
basic toggle switches, thumbwheel switches or push button numeric pad for
programming the vehicle to go to specific station. The advantage of manual
system is that it is the least expensive and simplest system. The disadvantages
of manual system are that its efficiency depends upon operators. Finally these
types of systems controller cannot determine vehicle location while it is in
transits.( (Ozden, 1988; Bartholdi and Platzman, 1989).)
The second level of sophistication in control system is referred to as
remote dispatch. In such systems operator intersects with the local controller
who in turn transmit information such as destination , rout and automatic load/
unload commands to the vehicle this control system allows the vehicle to
circulate on guide path looking for work. this system does not allowed
tracking capabilities. The third level is more complex and expensive and is
referred to as the central computer controlled system.( (Egbelu and Tanchoco,
1984; Russell and Tanchoco, 1984))
4.2 Guide Path Techniques:
a. passive techniques:
It involves the use of chemical, paint and adhesive strips or tape
where by the AGV focuses a beam of light on the reflective tape and tracks
the path by measuring the amplitude of reflected beam. Another passive
method involves vehicles with metal detecting sensors following stainless
steel tape. Communication of commands and positional information to the
vehicle may be accomplished by placing guide path codes along the guide
path.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
Active Techniques :
By for most commonly used method in industry is the wire guide path.
This method involves cutting a slot in the floor (1/8 to ¾ inch wide ) and (1/2
to 1.5 inch deep), in to which one or more wires are placed and grouted and
epoxyed. There are two different wire guide path techniques, one using either
one wire in the slot operating on one frequency or one multiple overlaid
frequencies and other using several wires in the slot each operating at a
different frequency. With multiple wire method a path is selected at decision
points according to the assigned frequency. The vehicle can be programmed
by system controller at decision points to follow the appropriate frequencies
and thus the vehicle is directed on the desired path.
4.3 Communication Technique :
Irrespective of guidance technique used it is essential for
individual vehicle to be able to communicate with the system controller. The
vehicle must be able to receive such commands as work assignments,
destinations, route frequency, speed, blocking instruction, when to start and
stop and auxiliary equipment commands used similarly vehicle must be able
to transmit it’s status to the system controller by sending such informations as
vehicle identification, location, direction of travel speed of travel & battery
status. There are two AGV systems viz. continuous & discrete. Continuous
indicates that the area controller always communicates with any vehicle where
as discrete means that area controller can only communicate with a particular
vehicle at times.
Radio frequency communication is widely used from in an
continuous communication. Each AGV is equipped with transmit / receive
antenna. Each AGV may be on a different frequency.
The optical method involves stopping the AGV at set stations
along the guide path where information is passed to the vehicle using infrared
light.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CHAPTER 5
APPLICATION OF AGVS
Introduction :
AGV is used in various growing number and a variety of
applications.
5.1 Driverless train operation :
These applications involved the movement of large quantities of
material over large distances. e.g. the moves within a large factory building or
buildings in large storage depot. For the movement of trains consisting of ¹ to
10 trailers, this become an efficient handling method.
Figure 5.1
AGV Used In Driverless Train
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
5.2 Storage / Distribution system :
Unit load carriers and pallet trucks are particularly used in these
applications. In these storage or distribution operation, the movement of
material is in unit load form. The application often interfaces the AGV with
some other automated handling or storage system this type of storage /
distribution can also be used in light manufacturing and Assembly operation
in which work in process is stored in a central storage area and distributed to
different work station for assembly or processing.
Figure 5.2
AGV Used in ASRS
5.3 Assembly line operation :
AGV system is being used in a growing number of assembly line
applications. In these applications rate is relatively low and there are variety
of different models made on production line.
5.4 Miscellaneous Applications :
Other applications of AGV system including non-manufacturing and
non-warehouse applications such as mail delivery in office building and
hospital material handling applications between different floors of the
hospital.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CHAPTER 6
FUTURE TRENDS
Although it is difficult to predict the future with absolute certainty, it can be
concluded from the trends that seem to indicate future status of AGV systems.
6.1 Guidance :
The research is being accomplished to expand capability and
even to eliminate the need for guidance using guide path on board controller.
On board controller is becoming more sophisticated and at same time they are
becoming smaller and less expensive the vehicle controllers are exhibiting
such features as expanding diagnostics. Although vehicle cannot repair
themselves, they can at least indicate their problems to maintenance and repair
person. Controller sophistification will also allow the vehicle to operator more
intelligently in complex handling situation and will increase the system
integrity in the event of host computer failure.
6.2 Vehicle communication:
The trend is towards continuous as opposed to discrete
communication
So that vehicle will be able to communicate and receive updated instruction
at any time.
6.3 system controller:
System will be designed to have capability to track material and
store this information. They will be able to follow and control material flow to
support just in time concepts. The system controller will also be able to be
integrated with network allowing it to communicate with any other facility
controller.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
6.4 Vehicle :
Vehicle will become more standard requiring less engineering to
adapt the vehicle to a particulate task, thus lowering the coast of vehicle to a
particular task, thus lowering the coast of vehicle to a great extent this will
make them easier to justify for many users.
6.5 Improved Graphical Display :
There will be probability the increased use of color graphical
display showing entire guide path, every vehicle location, the vehicle
identification, the vehicle status and vehicle load.
6.6 Safety:
New safety sensors for proximity detection will be developed
and coupled with computing power of on board controller to produce on even
vehicle that readily negotiate pedestrian clogged aisle.
Figure 6.1
Safety Features of Automated Guided Vehicle
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
7. Advantages and Disadvantages
7.1 Advantages of AGV
Following are the advantages of AGV
1. Reduction in labor force.
2. Improved productivity and quality.
3. Job enrichment and worker satisfaction.
4. Reduction in space requirement
5. Reduction in product damage.
6. Improvement in house keeping.
7. Ease of removal and relocation.
8. Integration with other type of automations.
9. System adaptability and flexibility.
7.2 Disadvantages of AGV
Following are the disadvantages of AGV
1. Expensive
2. Requirement of specially designed floor space.
3. Performance is affected if guide path bed is not stable.
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Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
CONCLUSION
This paper presents a classification scheme for automated guided vehicle
systems. This scheme is developed from a system control perspective. The
paper provides a discussion of the functionalities required of a generic AGVS
controller. The classification scheme is then developed based on the impact
the AGVS design alternatives have on the control system.
The scheme is useful as a structured method for understanding the impact of
design decisions on the control system. It provides a mechanism for
organizing the academic literature on AGVS and comparing the application
domains of different techniques. It also provides helpful information to the
system designer about the impact of design decisions on the required
controller functionality and resulting complexity. The ultimate goal is to use
the classification scheme as a design aid.
The classification scheme presented in this paper provides an organization
mechanism for AGVS from a control perspective. More importantly, it
provides the foundation for the long-term development of an automated
guided vehicle system design aid.
REFRANCESPage 19 of 20
AUTOMATED GUIDED VEHICLE
Department of Mechanical Engineering RCPIT, Shirpur (2010-11)
1. Bakkalbasi, O. and McGinnis, L.F., 1988, “ABC’s of Preliminary In-House Planning and Analysis of AGVS Applications,” Proceedings of AGVS’88, MHI, Cincinnati, OH, September 27-28.
2. Baumgartner, E.T. and Skaar, S.B., 1994, “An Autonomous Vision-based Mobile Robot,” IEEE Transactions on Automatic Control, vol. 39, pp. 493-502.
3. Christensen, J.H., Struger, O.J., Norrie, D. and Schaeffer, C., 1994, “Material Handling Requirements in Holonic Manufacturing Systems,” Proceedings of the 1994 International Material Handling Research Colloquium, Grand Rapids, Michigan, June.
4. M. P. Groover “Automation, Production Systems and Computer integrated Manufacturing “ TATA McGraw Hills Publications,”Second Edition,1995.
5. Flexible Manufacturing Systems: Recent Developments (Manufacturing Research and Technology) by A. Raouf and M. Ben-Daya (Hardcover - 9 Feb 1995)
6. Flexible Manufacturing Systems: Design, Analysis and Simulation (Manufacturing Engineering and Materials Processing) by Joseph Talavage (Hardcover - 18 Dec 1987)
7. J.H. Fuchs “Advanced Manufacturing Methods”, Tata McGraw Hills Publications, First Edition,1992
8. Journal paper of Flexible Manufacturing System with AGV based material handling by FUHONG DAI, BASc northest university of technology of P.R. Chaina 1982.
9. Modeling, Simulation, and Control of Flexible Manufacturing Systems: A Petri Net Approach (Series in Intelligent Control and Intelligent Automation) by MengChu Zhou and Kurapati Venkatesh (Hardcover - 1 May 1999)
10. A controle classification of Automobile vehicle system by Brett A. Peters, Department of Industrial Engineering, Texas A&M University
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