IE 447 - CIM Lecture Notes - Chapter 9 MHS Understanding AGVS History of AGVS IE 447 - CIM Lecture Notes - Chapter 9 MHS

History of AGVS 1953 First AGV The first AGV system was built and introduced in 1953( A modified towing tractor that was used to pull a trailer and follow an overhead wire in a grocery warehouse) Automatic Guided Vehicles have played a role in moving materials and products 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 50’s and early 60’s towing AGVs were in operation in many types of factories and warehouses. IE 447 - CIM Lecture Notes - Chapter 9 MHS

History of AGVS 1973 Volvo Assembly Plant In 1973, Volvo in Kalmar, Sweden set out to develop non-synchronous assembly equipment as an alternative to the conventional conveyor assembly line.  The result was 280 computer-controlled assembly AGVs. History of AGVS 1973 Volvo Assembly Plant In 1973, Volvo in Kalmar, Sweden set out to develop non-synchronous assembly equipment as an alternative to the conventional conveyor assembly line.  The result was 280 computer-controlled assembly AGVs. IE 447 - CIM Lecture Notes - Chapter 9 MHS

History of AGVS 1970s First Unit Load Introduction of a unit load vehicle They have the ability to serve several functions; a work platform, a transportation device, and a link in the control and information system History of AGVS 1970s First Unit Load The first big development for the AGV industry was the introduction of a unit load vehicle in the mid 1970s.  These 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.  Today there are several hundred systems using unit load vehicles in operation which were produced by a number of manufacturers.  These systems transport material in warehouses, factories, mills, hospitals, and other industrial and commercial settings. They transport material in warehouses, factories, mills, hospitals, and other industrial and commercial settings. IE 447 - CIM Lecture Notes - Chapter 9 MHS

History of AGVS Smart Floors and Dumb Vehicles In the 1970’s the principal guidance technology was to induce an electronic frequency through a wire that was buried in the floor. ‘floor controller’ History of AGVS Smart Floors and Dumb Vehicles In the 1970’s the principal guidance technology was to induce an electronic frequency through a wire that was buried in the floor.  A device called a ‘floor controller’ turned the frequency on the wires on and off and directed the AGV through its intended route.  The AGV was considered ‘dumb’ since the vehicle was just following signals in the floor. The intelligence for the routing of the vehicles was in the floor controllers.  So, the systems of this day were considered “smart floors” and “dumb vehicles”. An antenna on the AGV would seek out the frequency and guide the vehicle based on the strength of the signal.  This technology required embedding multiple wires in the floor in order to handle intersections or other decision points.  The system would energize the wire that would correspond to the intended direction of travel.  For example, at an intersection three separate wires might be required. These first generation navigation schemes were expensive to install. All floor cuts needed to follow the exact path of the AGV.  The cut for a turn had to follow the radius curve that the vehicle would make when turning.  Many systems had to embed four wires - three for guidance and one for communications.  Often, rebar or electronic signals would interfere with the guidance signals imposed on the wires. These first generation navigation schemes were expensive to install. All floor cuts needed to follow the exact path of the AGV. IE 447 - CIM Lecture Notes - Chapter 9 MHS

History of AGVS Dead Reckoning Capability As the vehicles became more intelligent, the path became less sophisticated Dead reckoning is a term that describes the ability of a vehicle to traverse steel expansion joints on the factory floor or to cross a steel grate History of AGVS Dead Reckoning Capability As electronics and microprocessors advanced, so did AGV applications. As the vehicles became more intelligent, the path became less sophisticated.  One of the first major breakthroughs was the development of dead reckoning capabilities.  Dead reckoning is a term that describes the ability of a vehicle to traverse steel expansion joints on the factory floor or to cross a steel grate.  The biggest advantage was that dead reckoning eliminated the need to make the cut radius turns at intersections.  The vehicles could leave the wire, turn at a programmed radius, and then pick-up the wire to continue its course of travel.  The path still required multiple wires in the floor, but the installation was greatly simplified. The biggest advantage was that dead reckoning eliminated the need to make the cut radius turns at intersections. (Installation was greatly simplified). IE 447 - CIM Lecture Notes - Chapter 9 MHS

History of AGVS 1980s Non-Wire Guidance   The introduction of laser and inertia guidance. Allow for increased system flexibility and accuracy No need for floor alterations or production interruption History of AGVS 1980s Non-Wire Guidance During the late 1980s, non-wire guidance for AGV systems was introduced.  Laser and inertia guidance are two examples of non-wire guidance which allow for increased system flexibility and accuracy. When changes to the original guidepath are needed, there is no need for floor alterations or production interruption.  These and other methods of navigation are explained more fully in the section on navigation. IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS AGV NAVIGATION The principles which make it possible for an AGV to navigate its way between any two locations are really quite simple. All navigation methods use a path. The vehicle is instructed to Follow a Fixed Path or Take an Open Path. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Fixed Path Navigation Following a Path The paths are well marked on the floor The paths are continuous The paths are fixed, but can be changed Fixed Path Navigation Following a Path Vehicles that FOLLOW a path use the earliest methods of AGVS navigation.  The general features of these methods are: The paths are well marked on the floor The paths are continuous The paths are fixed, but can be changed IE 447 - CIM Lecture Notes - Chapter 9 MHS

Fixed Path Navigation: Creating a Path The principle techniques for creating paths are to: Apply a narrow magnetic tape on the surface of the floor Apply a narrow photo sensitive chemical strip on the surface of the floor Apply a narrow photo reflective tape on the surface of the floor Bury a wire just below the surface of the floor Fixed Path Navigation: Creating a Path The principle techniques for creating paths are to: Apply a narrow magnetic tape on the surface of the floor Apply a narrow photo sensitive chemical strip on the surface of the floor Apply a narrow photo reflective tape on the surface of the floor Bury a wire just below the surface of the floor The first three methods require a sensor on the underside of the vehicle which can detect the presence of the surface mounted path.  The sensor’s mission is to keep the vehicle directly over the guide path.  If the path makes a turn the sensor detects the turn, provides feedback to the onboard vehicle controller, which in turn causes the vehicle to steer in the direction of the path.  The sensor’s role in connection with the onboard controller and steering mechanism is to cause the vehicle to FOLLOW the path. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Fixed Path Navigation: Buried Wire Path Bury a current-carrying wire just below the surface of the floor Buried Wire Path Bury a wire just below the surface of the floor When the fourth method of “path following” is employed using a current-carrying buried wire, the under vehicle sensor takes the form of a small antennae consisting of magnetic coils.  With current flowing, a magnetic field surrounds the buried wire.  The closer the buried wire is to the AGV antennae, the stronger the field. The magnetic field is completely symmetrical around the conductor or the buried wire.  At a given distance from the wire the field has the same strength on either side of the cable.  The field strength is detected by the antennae’s magnetic coil and induces voltage in the coil. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Fixed Path Navigation: Steering Correction Coils The vehicle steers itself to FOLLOW the magnetic field surrounding the buried wire. Fixed Path Navigation: Steering Correction Coils Like the three other path following methods, the vehicle steers itself to FOLLOW the magnetic field surrounding the buried wire.  To get a steering correction signal the vehicle’s sensing antennae consists of two coils.  When the vehicle is centered directly above the buried wires equal voltages are induced in the two coils.  If the vehicle moves a bit to one side of the wires, the induced voltages would be of different strength.  The difference in signal strength in the coils is proportional to side displacement of the coil.  This difference is amplified and fed back to control an onboard servo motor, which turns the guide wheel or wheels until both coils receive equal signals, and the course is corrected. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Fixed Path Navigation: Path Selection In this illustration, a vehicle at “A” has two choices on how to get to “B”.  A computer either on board the vehicle or at some central location selects a path based on established criteria. Criteria: The shortest distance The path with the least traffic at the present time All of the “PATH FOLLOWING” methods permit routing options that include guide path switching and merging. Fixed Path Navigation: Path Selection In this illustration, a vehicle at “A” has two choices on how to get to “B”.  A computer either on board the vehicle or at some central location selects a path based on established criteria.  That criteria may be the shortest distance or the path with the least traffic at the present time. Once selected the vehicle is dispatched and navigation begins.  All of the “PATH FOLLOWING” navigation methods permit routing options that include guide path switching and merging. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Open Path Navigation: Taking a Path Unlike “path following navigation,” where the guide paths are fixed, and more or less permanent, vehicles operating in the “Take a Path” category are actually offered more variation if not an infinite number of ways to navigate the open space between two points. Open Path Navigation: Taking a Path Navigation methods that direct a vehicle to “TAKE A PATH” employ developments that came into their own in the early to mid 90’s.  They utilize a different set of technologies. Unlike “path following navigation,” where the guide paths are fixed, and more or less permanent, vehicles operating in the “Take a Path” category are actually offered more variation if not an infinite number of ways to navigate the open space between two points. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Open Path Navigation: Navigation Methods The three most common open space navigation methods are: Laser Guidance Inertial Guidance Cartesian Guidance The choice of navigation method for a particular application is often a simple matter of preference. Open Path Navigation: Navigation Methods The three most common open space navigation methods are Laser Guidance, Inertial Guidance, and Cartesian Guidance.  The choice of navigation method for a particular application is often a simple matter of preference.   Each method offers different benefits and costs associated with system set up and operation which is application dependent. Unless there is a definite preference, users should work closely with suppliers to evaluate the options in relation to the intended application. Each method is backed by a rich history of its successful use in practice. Laser Guidance Inertial Guidance Cartesian Guidance IE 447 - CIM Lecture Notes - Chapter 9 MHS

Navigation Methods - Laser Guidance Reference points are strategically located targets A beacon on top of the vehicle emits a rotating laser beam which is reflected back to the vehicle when it strikes (sees) a target. Navigation Methods - Laser Guidance With laser guidance, the reference points are strategically located targets mounted to a vertical surface such as a wall or column.  A beacon on top of the vehicle emits a rotating laser beam which is reflected back to the vehicle when it strikes (sees) a target.  The targets are known (X,Y) locations.  A vehicle needs only two (but ideally three) targets in order to calculate a relative coordinate location and heading using simple geometry. When a destination is assigned to a vehicle, a known obstruction free path is chosen causing the vehicle to take a heading in the direction of the path.   The vehicle’s location and heading are continuously updated in relation to known targets, and adjustments in headings are made until the destination is reached. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Navigation Methods - Inertial Guidance With inertial guidance, an on board gyroscope establishes and maintains a vehicle’s heading.  Distance traveled is calculated by an on board encoder which counts wheel rotations. Precision in a vehicle location can be achieved by way of discrete targets or reference points spaced along the known routes that a vehicle can take.  A typical target is a thin, coin shaped magnet fastened to the floor surface.  A sensor located beneath the vehicle can detect the presence of the magnet.  The difference between when a vehicle expected to see a target and when it actually saw it is used to recalibrate the vehicle navigation controls and to correct the heading and speed if necessary.  Even though this is categorized as open-space navigation, the actual paths that can be taken are more limited than laser guidance due to the need for floor-mounted calibration targets. An on board gyroscope establishes and maintains a vehicle’s heading. Distance traveled is calculated by an on board encoder which counts wheel rotations. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Navigation Methods – Cartesian Guidance Location precision is accomplished by way of a fixed grid pattern that covers the entire floor area. The possible travel paths in a given, unrestricted operating area for a grid based system are infinite and most like that provided by laser guidance Navigation Methods - Cartesian Guidance For systems that use Cartesian X,Y coordinate navigation, location precision is accomplished by way of a fixed grid pattern that covers the entire floor area.  Every point on every line of the vehicle operating grid has a known Cartesian (X,Y) coordinate. Using appropriate underside sensors the vehicle “looks” for these lines. When it sees or detects one, it has a precise location reference relative to its assigned path and can correct its heading and speed. A grid based navigation system also utilizes odometer, distance and angle measurements by the vehicle.  In large vehicles this is achieved via an onboard gyroscope, in the same way as inertial guidance.  In smaller vehicles it is more common to use only encoders.   The possible travel paths in a given, unrestricted operating area for a grid based system are infinite and most like that provided by laser guidance IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS AGVS Dispatching Dispatching AGVS is much the same as dispatching taxi cabs. The dispatch function makes sure that all customers get timely services from the vehicle best able to service a request. Remote and local dispatch are most commonly described as offboard and onboard dispatchers respectively. AGVS Dispatching AGVS dispatching is essential to every AGVS, whether simple or complex.  Dispatching AGVS is much the same as dispatching taxi cabs. The dispatch function makes sure that all customers get timely services from the vehicle best able to service a request.  Without a dispatching function, nothing would move.  With inefficient dispatching, a system will not obtain maximum benefits.   The dispatch function maximizes the benefits of any AGVS and ensures that all customers get serviced in a timely manner.  Remote and local dispatch are most commonly described as offboard and onboard dispatchers respectively. IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS AGVS Communications Communications include  message commands such as: where to go, when to start, when to slow down, when to stop. Four types of basic communication media: Radio Communication Infrared Communication Guide Wire Data Communication Inductive Loops Communication AGVS Communications Communications include  message commands such as where to go, when to start, when to slow down and when to stop.  It may also include fault condition reporting.  Computer-controlled systems overseeing remote objects need a means of communicating commands, and in many cases confirming replies, between a supervisory computer and the objects being controlled.  Depending on the application, there are four types of basic communication media being used within AGV Systems. IE 447 - CIM Lecture Notes - Chapter 9 MHS

AGVS Communications Radio Communication Maximum flexibility in system control Vehicles can be programmed “on the fly” system speed of response to changing load movement demands is improved Radio Communication Radio provides maximum flexibility in system control.  Vehicles can be programmed “on the fly”, new routings or maps can be downloaded quickly, and system speed of response to changing load movement demands is improved.  It provides almost constant communication between the vehicles and the system and makes the AGVS system a very responsive tool that can react to the changing dynamics of the work environment. IE 447 - CIM Lecture Notes - Chapter 9 MHS

AGVS Communications Infrared Communication Optical infrared communication is highly reliable but has the disadvantage of not being continuous; it is point to point.   Vehicles may be stopped during this data exchange which usually occurs at load stations where the fixed and mobile units are aligned and in close proximity.   Infrared Communication Optical infrared communication is highly reliable but has the disadvantage of not being continuous; it is point to point.  Vehicles may be stopped during this data exchange which usually occurs at load stations where the fixed and mobile units are aligned and in close proximity.  Or, the vehicle communicates at fixed points along its guide path as the vehicle travels through a given zone. The picture shows optical sensors at a  conveyor pick-up/deposit stand.  One sensor is for transmitting and the other for receiving. Vehicles are usually not dispatched from a communication point unless the path to the next destination is free of traffic.  In large systems this could present a problem in meeting throughput.  Alarm conditions also cannot be reported as they occur.  As a result, infrared communication is best suited for small systems with few vehicles and load stations. Or, the vehicle communicates at fixed points along its guide path as the vehicle travels through a given zone. Infrared communication is best suited for small systems with few vehicles and load stations. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Remote Dispatching The Dispatcher The remote dispatch function generally resides in a computer (PC), Programmable Controller (PLC), or other microprocessor, known as the Dispatcher. The Dispatcher accepts input from the various system Components (generally transport requests) and directs the AGVS to fulfill the command in the most efficient manner. Remote Dispatching The Dispatcher The remote dispatch function generally resides in a computer (PC), Programmable Controller (PLC), or other microprocessor, known as the Dispatcher.  The Dispatcher accepts input from the various system components (generally transport requests) and directs the AGVS to fulfill the command in the most efficient manner.  This function directly compares to the taxi Dispatcher back at the terminal, receiving calls from many customers and then dispatching each driver via radio to the pickup station.  Remote dispatch can occur with vehicles at single or various dispatch points.  Remote dispatch can occur with vehicles at single or various dispatch points. IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS AGVS Monitoring Types of monitoring : System monitoring Vehicle monitoring The functions and reporting capabilities of each are important to the safe operation of the AGVs. AGVS Monitoring Two types of monitoring that provide necessary information on the vehicle status and the performance of the system include system monitoring and vehicle monitoring.  The functions and reporting capabilities of each are important to the safe operation of the AGVs. IE 447 - CIM Lecture Notes - Chapter 9 MHS

Material Handling Systems Automatic Storage Retrieve Systems AS/RS IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS

IE 447 - CIM Lecture Notes - Chapter 9 MHS