AGV Resources
Terminology Guide
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Access Sensors
Through beam type photo-eyes or ultrasonic sensors that are used on lift/lower drop stands to ensure that loaded AGVs do not attempt enter an already-loaded stand.
Accurate Stop
A method of stopping an AGV within a repeatable margin, without undue shaking or rocking of the load. This requires placing the AGV into a reduced speed prior to sensing the stop position. Typical tolerance is +/- 1.0 inch.
Accurate Stop Target
What the AGV "looks" for to determine where to stop at an Accurate Stop station. Three different types of targets are currently in use. Accurate stop activators may be in-floor magnets, above floor optical targets or virtual locations stored in the AGV’s memory.
Action Code
Action Codes are floor codes (either physically installed or virtual in the AGV’s memory) that cause the AGV to perform a specific function, have no location number, and may be placed anywhere in the system (within code-placement limitations as defined elsewhere in this manual). Typical Action Code functions include Horn Beep, Change Path, and Change Speed. Action Codes are non-conditional in that they will cause the same action in all AGVs independent of collision-avoidance and routing decisions.
AGV
Automatic Guided Vehicle.
AGVS
Automatic Guided Vehicle System.
AGV System Controller
In some AGV systems, a system controller is used to coordinate traffic control (blocking), route the AGVs to destination or to manage the overall operation of the system. System management generally entails providing a means of remoter calling for AGV service.
AGV Vehicle or System Manager
Another term for an AGV System Controller
Alternate Destination
An Alternate Destination can be thought of as a 2nd (or 3rd) location to be used as an alternate to the programmed destination. Alternates are most-often used in conjunction with Bypass to service either of two (or more) spurs having different station numbers (and thus individually programmable), but sharing a common material handling function. Alternates are also used commonly to improve throughput; when the AGV bypasses its programmed Destination and then reads the appropriate Alternate Destination Floor Code, it stops and performs its Station Cycle. This allows the AGV to be returned to active service quickly, as opposed to waiting or re-circulating for an occupied or otherwise out-of-service destination. See also Bypass.
Automatic Charge
The process by which an AGV’s battery is recharged without removal from the vehicle. The AGV is equipped with a mechanism that contacts a copper plate placed in the floor or on a stantion. This plate is wired to a battery charger that automatically turns on when an AGV is present. When an AGV stops at an automatic charge location, its battery is recharged until it departs.
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Blocking
Blocking refers to the anti-collision features of the AGV as it relates to traffic control/separation between the AGVs.
Blocking Hold
Refers to an AGV state of no motion, when the AGV is not able to enter an intersection or proceed forward due to other AGV traffic interference.
Bypass
The ability of an AGV to over-ride the normal routing instructions to its programmed destination based on whether there is other AGV traffic congestion. The Bypass function is used most-often to keep mainline AGV traffic flowing while a spur or P & D Stand is not ready for another AGV.
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Call Aging
Refers to the capability of the system controller to prioritize (by time waiting, or importance, etc.) calls that are received. The AGV system controller can be configured such that specific stations have a higher priority than other calls.
Call Box
Refers to an enclosure assembly that is used by an operator to call an AGV. There are many different forms of call boxes including ones with lights, pushbuttons, graphical interfaces, etc.
Call Station
The name given to the function and the station involved in calling an AGV. If the AGV, upon sensing the Call, is in an operational mode to service calls at the dispatch station and has the proper load/deck status; it will route itself to the Call Station.
Code
A piece of information conveyed to the AGV as it travels along the path. Typically, this information is contained in a device embedded in the floor along the path or it is a virtual entity that does not physically exist, but performs the same function along the path (contained in the virtual map of the system in the vehicle’s memory).
Convergence
A Convergence is where two or more paths enter an intersection and share the same outbound path. Only one AGV may enter a Convergence at a time.
Crossing
A Crossing is an intersection where two or more paths cross but do not share a common outbound path. A Crossing may be physical or logical.
Current Destination
Refers to the Station that the AGV is heading to.
Current Location
The location number associated with the last unique floor code (physical or virtual) recognized.
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Decision Point
Any location where the path segments diverge is a decision point. The AGV or system controller must make a decision which path branch to follow.
Decision Point Code
An attribute given to a Physical or Virtual Code that causes the AGV to decide on a path to follow based on its Current Destination.
Default Destination
Pre-determined stations to which an AGV will go in the event that no other destinations are programmed when the start switch on the AGV is depressed.
Destination
See Current Destination, Default Destination
Door Limit Switches
Switches attached to doors through which AGVs travel. Doors included are fire doors, automatic doors, and manually operated doors. The switches must be installed to detect when the doors are fully opened. The switches are wired to fixed mounted transceiver inputs, preventing AGVs from trying to go through a closed (or partially closed) door.
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Entry Optic
See Access Optic.
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Floor Code
A Floor Code is a generic description of a virtual or physical code to convey information to an AGV. In wireless systems Floor Codes do not physically exist and are embedded in the AGV’s onboard system map.
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Grid Navigation
A form of wireless AGV navigation that depends on the use of an infloor grid pattern. This pattern can consist of infloor magnets, wires, tiles, etc. The AGV uses the grid patterns to dead-reckon to a prescribed path in its memory using the grids to update any positional errors.
Gyro Navigation
A form of wireless AGV navigation that depends on the use of an electronic gyroscope onboard the AGV. This device can detect when the AGV is deviating to the left or right of the true path and cause the AGV to make the necessary course correction.
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Handshake Optics
A set of optical transceivers used to facilitate and control automatic load-transfer between an AGV and a P&D stand. Consists of a transmitter and receiver on the AGV, and a transmitter and receiver on the P&D stand.
Horn Beep
A short blast (~2 seconds) of the AGV's horn, triggered by a Floor Code or AGV station-cycle software.
Horn on Programmed Stop
A Horn Beep when the AGV arrives at its programmed destination.
Horn on Start
A Horn Beep before or upon the start of AGV travel.
Horn on Stop
A Horn Beep when the AGV is about to cease travel due to a Blocking Hold, bumper contact with an obstruction, depression of a stop switch, object detection, or any other means of causing the AGV to stop.
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Inertial Navigation
See Gyro Navigation
Intermittent Horn
An on/off cycling of the AGV's horn, the duration of which is typically one second on, one second off, etc. Intermittent Horn is typically used as an "overdue" alarm (where the AGV is waiting for an operator to transfer a load) or in situations where the AGV is in need of operator assistance (battery-change area, AGV malfunction, etc.)
Initialization Point
These are the locations in the AGV system where the AGV may be introduced in the system from a "cold start" condition (i.e. without knowledge of its current location, such as after a power loss, guidance system failure, or driving the vehicle manually for an extended length).
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Laser Navigation
A form of wireless AGV navigation that depends on the use of an a rotating laser beam onboard the AGV and facility mounted targets. The laser beam is reflected off the targets to allow the AGV to determine its location along the prescribed route. Any deviations are corrected by the AGV taking the appropriate steering actions. The reflective targets are typically mounted about 7 feet above floor level approximately 25 feet apart on either side of the wireless path.
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Managed Charge
A process for controlling the charging of AGVs equipped with automatic charging equipment. This process is managed by a central AGVS controller, which dispatches AGVs to automatic charge locations, based on defined criteria.
Mobile Magnetic Transmitter
A large permanent magnet mounted under the AGV, used to actuate in-floor reed switches. This feature, used by the AGV to signal fixed equipment (door controls, lights, etc.) of its presence.
Mode
The term used to describe the type of control under which the AGV is operating. There are usually 4 modes "Remote", "Onboard", "Re-circulate", and "Diagnostic".
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Navigation Marker
A small device positioned at pre-defined intervals along a Virtual Path. Navigation markers can be a small infloor magnet, infloor electronic transponder or an above floor target. These markers are used as reference points, which allow the wireless AGV to correct errors in its position/course.
Non-wire
A form of AGV navigation that uses something other than an infloor wire for guidance. Typically, non-wire navigation is achieved by inertial (gyro), laser or grid based controls on the AGV.
No Passing
An area of guide path where because of physical limitations, only one AGV is allowed to travel at a time. Typically used in a narrow doorway that allows two-way AGV traffic, but is wide enough for only one AGV at a time.
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Object Detection Optic
An optical or sonic transceiver used by the AGV to sense obstructions in its path. Typically causes the AGV to slow to a reduced speed upon detection of an obstruction, but can be configured to cause the AGV to stop upon detection. The Dual-Range Object Detector is usually configured to slow the AGV upon long-range detection, and then to stop the AGV upon short-range detection.
Offset Curve
Offset curves are aberrations intentionally added to the guidepath in many tow vehicle/trailer systems to achieve proper trailing clearances between fixed objects and trailers pulled by the AGV.
Opportunity Charge
Refers to automatic battery re-charging of the AGV battery when the AGV is not doing any work and has the opportunity to charge. The vehicle will automatically connect the battery to an off board charger. The vehicle does this by accurately locating itself over the recharging plates installed in the facility floor. This method will require maintenance free batteries.
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P & D Stand
Pick and Drop Stand. Refers to the fixed stand that the AGV uses to provide loads to and/or receive loads from the facility. Depending on the model of AGV used, a P & D Stand might be a powered roller conveyor, a gravity conveyor, or simply a static (non-powered) fixture.
Pick Conveyor / Stand
An AGV picks-up a load at a Pick Conveyor or a Pick Stand.
Plug Braking
On AGVs using series-wound drive motors, Plug Braking ("plugging") is the term used to describe the method of electrically-braking the AGV. This is done by electrically reversing the current flowing through the motor's field, achieving roughly the same effect (but without the damage!) as putting an automobile's transmission in REVERSE while the automobile is moving forward. Plug Braking is often confused with Dynamic Braking, which refers to the method of electrically-braking an AGV using a shunt-wound drive motor.
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Radio Frequency (RF) Communication System
Refers to the communication system that is utilized to allow communications from the AGV to AGV and from fixed mounted transceiver radios to the AGVs.
Routing
Refers to the process by which a vehicle is directed to its programmed destination. This is accomplished by specific path selection logic, which the vehicle executes at locations in the system, referred to as decision points. Any location where the path segments diverge is a decision point.
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Smart Vehicle
An AGV is termed a ‘smart’ vehicle when it can perform its own routing and traffic control without the need of a central AGV controller.
Speed Changes
One should not assume that an AGV makes the transition from one speed to another in zero amounts of time or distance. An AGV arriving at its destination in full speed will take four to five feet to decelerate to creep speed or stop (depending on the Station Cycle). Acceleration, and especially deceleration distances, must be considered when laying-out the AGVS Blocking sub-system and when making throughput calculations.
Station Code
Generally a Virtual Code that the AGV can be programmed to stop at.
Station Cycle
Refers to the sequence of pre-determined events that an AGV performs upon arriving at its Destination.
Station Stop
A location in the facility where the AGV will stop, usually where material is required to be picked up or dropped off.
Stopping Distance
The amount of distance traveled after the AGV initiates one of its stopping modes. Stopping Distance is a function of AGV speed, load weight, braking adjustments, communications delays, and the event that caused the stopping action (normal stop switch, E-Stop switch, arrival at Destination, Blocking Hold, etc.).
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Target
Used in laser navigation type wireless AGV systems. See Laser Navigation.
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Virtual Code
An attribute placed on the wireless AGV path layout map in the AGV/s memory. It may signify an AGV station, action location or other parameter of the system operation.
Virtual Path
AGV guide path that is created for wireless AGV systems.
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Wireless
Can refer to either of two areas. Wireless AGV navigation is a form of AGV operation that does not require a wire imbedded in the floor. Typically, gyro/inertial, laser or grid navigation AGV technologies are referred to as wireless AGVs.
Also can refer to RF communications in an AGV system.
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Zero Speed
This term refers to the condition of an AGV when it is stopped, or very-nearly stopped. In most cases, load transfers will not begin until the AGV has sensed that it has reached Zero Speed.
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