Automated Guided Vehicles: Hardware By: Adam Aquino November 7,
2014
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Review An automated guided vehicle or automatic guided vehicle
(AGV) is a mobile robot that follows markers or wires in the floor,
or uses vision, magnets, or lasers for navigation. They are most
often used in industrial applications to move materials around a
manufacturing facility or warehouse. (Wikipedia) Used in every
industry (large factories and storage) Paper, metals, newspaper,
general manufacturing etc.
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Questions to Consider Why would certain types of AGVs be
preferable over others? What scenarios are the most appropriate for
certain types of AGVs?
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Overview: History and Current State First AGV invented by
Barrett Electronics in 1954. The term was not introduced until the
1980s, but was previously known as driverless vehicles. The first
model was a modified towing tractor that followed an imbedded wire
in the floor. Sensors on the bottom of the tow truck sensed and
responded to a magnetic field from the wires.
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Overview: History and Current State Today, the most advanced
AGVs are laser navigated (LGV), which are sophisticated and capable
of communicated with other robots. Many are navigated using machine
vision as well.
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Ways to Guide AGVs Between Stations Embedded wire in floor Good
for applications where paths are not going to change Magnetic Tape
on floor Requires sensors to detect tape path Less expensive and
can be modified Laser Target navigation Requires reflective tape on
walls and a laser transmitter on a rotating turret on the AGV. Good
for applications where AGV needs to adjust path by triangulating
position. Inertial navigation Requires transponders embedded in the
floor Extremely accurate (+/- 1 inch) Operates in tight aisles or
extreme temperatures. Vision Guidance Requires cameras (records
route and replays route) Good for applications where you cannot
modify the environment or infrastructure.
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Types and Uses of AGVs Towing Vehicles AGVS Unit Load Vehicles
AGVS Pallet Trucks AGVS Fork Truck AGVS Hybrid Vehicles Light Load
AGVS AGVS Assembly Line Vehicles
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Types and Uses: Towing Vehicles The oldest type of AGV Pulls a
trailer Good for heavy loads Range from 8,000 to 60,000 pounds Can
link multiple trailers Increased Safety
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Types and Uses: AGVS Unit Load Vehicles Load rests over the
majority of the vehicle Interfaces with stands and conveyors May be
loaded by cranes, forklift trucks, other AGVs etc. May communicate
between loading/unloading machine and AGV (handshake sensor) More
complex steering than towing AGVs and more expensive
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Unit Load Principle Principle Stored or moved as a single
entity at one time, regardless of the number of individual items
that make up the load. Less effort and work are required to collect
and move many individual items as a single load than to move many
items one at a time AGV Application AGV just needs a single flat
platform to transport a unit load, and unit loads can be stacked on
the platform. Does not need a basket (side barriers)
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Types and USES: AGVS Pallet Trucks Transport palletized loads
to and from floor level 2 general types Automatically reverse into
pallets Operators manually board vehicles and back them into
pallets Automatically reversing a guided pallet truck adds
considerable expense. Manually loading pallet trucks are more
common.
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Types and USES: AGVS Fork Trucks Used when the system requires
automatic pickup and drop off loads from floor or stand level and
where the heights of load transfer vary at stop locations.
Conveyers or load stands of different heights can all be serviced
Most expensive of AGVS types Harder to move large loads Requires
more precise movement.
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Types and Uses: AGVS Hybrid Vehicles Adapted from a standard
CAT-style man-aboard truck so that they can run fully automated or
be driven by a fork truck driver. These can be used for trailer
loading as well as moving materials around warehouses. (Wikipedia)
Customizable for most load types. 25 30% cheaper than standard AGVs
High Flexibility
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Types and USES: Light-load AGVS 500 pounds or less Transport
small parts to individual work locations Trays/baskets Good for
small and tight areas Applications include electronic fabrication,
small assembly manufacturing and parts kitting applications
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Types and Uses: AGVS Assembly Line Vehicles Similar to light
load AGVS Good for applications involving serial assembly processes
Cary subassemblies such as motors or transmissions Allow for
parallel operations Allow for individual tracking and measured work
rates Require extensive planning
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Level 1: Simple Manual Vehicle Dispatch, Load/Unload, No
Central Controller, No Host Interface. Level 2: Medium Automatic
Vehicle Dispatch, Load/Unload, Central Controller, Product
Tracking, Multiple Path Options. Level 3: More Automatic Vehicle
Dispatch, Load/Unload, automatic coupling/uncoupling (applies to
tuggers only), Central Controller, Complex Host Interface, Ethernet
Link, Product Tracking, Multiple Path Options Multiple Transfer
Heights, etc. COSTS
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Primary Vendors Savant Automation, Inc. America in Motion Ward
Systems, Inc. Egemin JBT Corporation TecnoFerrari/Prella
Technologies
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Supporting Technologies
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Technical Paper: Modelling battery constraints in discrete
event automated guided vehicle simulations Author: R. McHANEY
Purpose: AGV battery usage is frequently omitted in simulation
because battery constraints are mistakingly believed to have
minimal impact on throughout and the number of vehicles required to
operate a system, many simulation analysts do not have a full
understanding of how batteries are used to power AGVs, and battery
analysis requires additional input information and varies from
vendor to vendor. Main Takeaway Do not ignore battery
considerations. They are important.
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Video https://www.youtube.com/watch?v=33XpgfppjtE
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Standards ANSI/ITSDF B56.5-2012 - Safety standard for
Driverless, Automatic Guided Industrial Vehicles and Automated
Functions of Manned Industrial Vehicles - Applies to system
suppliers, manufacturers, purchasers and users for the design,
construction, application, operation and maintenance of UGVs
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Example The AGVs in the figure include load station 1 where raw
parts enter the system for delivery to any of three production
stations 2,3, and 4. Unload station 5 receives finished parts from
the production stations. Load and unload times at stations 1 and 5
are each 0.5 min. Production rates for each workstation are
indicated by the delivery requirements in Table 10.5. A
complicating factor is that some parts must be transshipped between
stations 3 and 4. Vehicles move in the direction indicated by the
arrow in the figure. Determine the average delivery distance, L
.
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Example
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Summary: Main Takeaways The type of AGV you use is highly
dependent on the layout of the workspace AGVs are highly dependent
on specific types of sensors, which depend on the application and
type of navigation that the AGV uses.