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Introduction
This Article takes an In-depth look at Automated Guided Vehicles
You will learn more about topics such as:
History of "Driverless" Vehicles
Types of AGVs
Benefits of Going Automated
Common AGV Components
AGV Guidance and Navigation Systems
AGV Safety and Compliance Standards
The Beginning of "Driverless" Vehicles
In 1954, when Arthur "Mac" Barrett, of Barrett Electronics Corporation, unveiled the first AGV, he named it Guide-o-Matic and described it as a driverless vehicle. Guide-O-Matic was a towing machine that followed a signal given from a wire in the ceiling, which was later replaced by a wire buried in the floor. It had the simple function of pulling trailers in a warehouse.
Arthur Barrett spent his life exploring and investigating different ways of using automation to open doors, move materials, and develop other work saving devices. His radio controlled industrial vehicles were called Radox, which allowed operators to program it to pick up pallets, tow vehicles, or index a pallet truck.
The advancements of Barrett inspired engineers and designers to develop the modern systems of AGVs that use cameras, lasers, electrically charged tape, and other means to maneuver automated vehicles in various environments. The discovery of automatic guided vehicles has revolutionized raw and finished material transport.
What is an AGV?
AGVs are guided computerized vehicles that use computer software to determine their positioning, movement, and location. Powered by a battery or electric motor, they are able to complete manufacturing, warehousing, loading, and other operations without human interference. Self-powered AGVs can do load transfers, move and stack pallets, complete assemblies, and tow heavy loads, functions previously performed by people. They have improved production efficiency, removed humans from unsafe and potentially dangerous conditions and overcome possible human errors.
Though the term AGV, or automatic guided vehicle, may seem to be self defining, in actuality, there are multiple ways that AGVs receive their instructions and programming, which include wires implanted in the floor, cameras, radio waves, lasers, or other forms of technology.
AGVs began as a method of towing trailers to speed up production. At the time, they were considered nice conveniences that saved time. During the latter part of the twentieth century, designers explored other ways to use the technology to improve factory conditions, which has led to a wide array of capabilities, uses, and functions for AGV technology.
Leading Manufacturers and Suppliers
Types of AGVs
Three types of AGVs are towing, fork trucks, and heavy load carriers. Each is designed to perform repetitive actions such as delivering raw materials, keep loads stable, and complete simple tasks. Unlike human workers, AGVs operate continuously only needing to stop to be recharged or repaired.
Towing AGV:
Towing AGVs, or tugs (otherwise known as a warehouse tugger), pull loads of several tons, reducing the hazards associated with using large heavy equipment. They are capable of moving loads of 10,000 to 50,000 pounds. Heavy-duty towing AGVs can pull sub-assemblies, machine components, equipment, and other materials that are unsafe for manual labor.
Fork AGV:
Fork AGVs are mechanized forklifts that can retrieve stock, place materials, and move and stack pallets. They supply automated machines and take finished products to storage or place them for shipment. Forklift AGVs can prove to be economical and cost savings since they replace lift trucks and Hi-Lo operators that require licensing and training. Heavy-duty forklift AGVs can move large paper rolls, steel coils, engines, and vehicles over any distance depending on their programming
Heavy Load AGV:
Though towing and fork AGVs are capable of handling large loads, certain industries such as aviation, large construction vehicle manufacturers, and shipbuilders require AGVs able to handle huge loads of up to 250,000 pounds. For these processes, AGV producers have created machines with large bases, solid wheels, and wide platforms. In many cases, this form of AGV has to be custom designed to exactly fit the requirements of the customer‘s industry.
Unit load AGVs have one specialized function, which is transporting totes, pallets, goods, and racks that are too heavy to be moved by other means. They are designed to move goods and heavy materials in a warehouse or storage facility. Unlike fork and towing AGV‘s, unit load, or unit load decks, are flat tables that can carry one or several individual units to and from conveyors, stands, automated storage, and various types of retrieval systems. Very similar to a flatbed, they usually move along one path in two directions, repetitively, and without variations.
Light duty AGVs are usually found outside of production facilities in hospitals, offices, or commercial locations. They are able to move very small loads of under 500 pounds. Small AGVs are especially useful in places requiring cleanliness where human presence may contaminate the environment. For example, in hospitals, they deliver patient charts and daily medications.
AGV Robots
AGV robots are automatic guided vehicles equipped with robotic limbs. AGV robots are more adept at picking up and moving items than regular AGVS, which are must less dexterous. In short, they combine the intuitiveness of a human and their ability to adjust to their surroundings, and combine them with the brute force of a lifting machine like a palletizer.
AGV robots offer their users many benefits. First, using AGV robots, manufacturers can save time and money. During auto parts assembly, for example, AGV robots can put together large parts much more efficiently than humans. They can even make tooling switches without assistance. Not only that, but they have no learning curve. Once programmed, they will perform their duties perfectly. Also, their programming tends to make them more precise and eliminates human error. Their operation also takes people out of harm‘s way. For loading and unloading applications, AGV robots offer greater mobility and high strength. Plus, once again, they eliminate the need to people in high stress or high risk situations. Another advantage of AGV robots is the fact that they are easier to set up that regular AGVs, as they require fewer physical markers and guides.
AGV Systems
The term "AGV systems" refers to automated, or automatic, guided vehicles. AGV systems run on industrial batteries or electricity to perform movement solutions within warehouses and facilities. Solutions include material handling, transportation, assembly, delivery and storage; these solutions have applications within most industries, including: greenhouse, general manufacturing, plastics and metal, newspaper and mail, automotive, aerospace, food and beverage processing and packaging.
To ensure smooth operations, AGV systems usually require monitoring. Especially in large factories or warehouses and/or where multiple AGV systems are in use, a traffic operating systems and controller are very important components. Generally, traffic operating systems consist of locator panels, CRT display and a central logging and report center. With the help of this technology, staff can successfully monitor and track the location and movement of in-house AGV systems and gauge their efficiency, thus avoiding collisions and traffic congestion.
Automated Guided Vehicles
Automated guided vehicles, also known as automatic guided vehicles or AGVs, are computer operated, self-powered transportation equipment used for applications within the material handling and moving industry. Though they were originally designed to serve only industrial market transportation and lifting, their use is now more widespread. Fields within which they are now used also include: general manufacturing, food and beverage processing, automotive, aerospace, packaging, greenhouse/industrial horticulture, metals and plastics and mail and newspaper.
These systems either operate with fixed guidance systems or free range systems. Fixed guidance makes use of magnetic tape, colored paint or embedded wire to guide vehicles that respond to antennae, signal emissions and frequencies on simple paths. Fixed guidance systems are reliable and they work well, but they are inflexible and limit the capabilities of their AGVs and they simply may not be well suited to some environments and applications. Fortunately, most automated guided vehicles are not limited by fixed guidance systems. Instead, most contemporary AGV systems are free range. Free range systems are computer-controlled, with onboard microprocessors and supervisory control systems.
Guided Vehicles
Guided vehicles are computer-controlled transportation units that perform applications without any sort of human direction or control. They are used for material handling and transportation applications and can be designed for sorting, storage, delivery or product assembly use. Guided vehicles, or automatic guided vehicles, reduce labor costs in manufacturing processes by providing high volumes of repetitive and tedious movements and actions with around the clock capabilities.
Vehicles can be equipped with an infrared detection system, or a bumper system, which helps to reduce the damage potential of collisions. Free range AVG systems which are controlled by computer software and international navigation capabilities are able to adjust a vehicle's route according to flow of traffic and possible obstructions, therefore making the factory floor a safer place to work.
Laser Guided Vehicles
Laser guided vehicles are capable of moving independently and managing and improving logistical operations. They navigate using a laser positioning system with an on board computer for correct speed and location. The laser scans three reflectors to calculate its position and angles, a process that occurs eight times per second. LGV vehicles have 2 dimensional laser emitters that emit a continuous beam of modulated laser light in a 360o pattern. The beam that comes back from the reflector is used to determine the X and Y coordinates of the reflector and the LGV.
As with other positioning systems, the three points determine the exact location of the LGV. The accuracy of the system is measured at ±10 mm (±0.394 inch) using four reflectors in a radius of 8 m (26 ft). Asymmetrical placement of the reflectors or targets is necessary to achieve specific positioning of the LGV, which is calculated 30 or 40 times a second. The location of the reflectors makes it possible to automatically switch from automatic mode to manual mode as the LGV travels its route. Complex routes are divided into fixed areas or layers with as many as 200 layers being used to layout a track or route.
The types of reflectors used for LGVs are flat and cylindrical with flat reflectors being the least expensive since they are reflective tape. Since flat reflectors have a contact adhesive side, they can be easily installed and repositioned when necessary. The installation of cylindrical reflectors requires the calculation of its fixed center point, which makes them difficult to install, fix, and makes them susceptible to damage. The main benefit of the reflector system is accurate positioning of the LGV. Additionally, LGVs can operate at speeds of 2 m per second (6 ft per second) for increased efficiency and exceptional performance.
The four main types of laser guided vehicles are high reach lift LGVs, fork LGVs, conveyor-bed LGVS and reel LGVs. High reach lift LGVs can carry up to 1200 kg (2645 lbs) and are used for pallet handling and pallet stacking up to 9 m (29 ft) high. Forklift LGVs are used for pallet handling of one to four pallets and stable load delivery. Conveyor bed LGVs can carry several products simultaneously and are used for high speed sortation, material flow and transport, distribution, and raw material handling.
Self Guided Vehicles
Self guided vehicles are computer-controlled transportation units that perform applications without any sort of human direction or control. Used increasingly in place of forklifts, conveyor systems and manual push-carts, automatic guided vehicles provide high volumes of movement, especially for repetitive and continuous processes. Industries such as aerospace, automotive assembly, food and beverage processing, mail service, assembly, newspaper, pharmaceutical, plastic manufacturing and storage use AGVs for sorting, delivering, transporting and assembling operations.
Depending on the specific application for which a vehicle is to be used, self guided vehicles range significantly in construction and shape. They may have a towing mechanism, room for unit or pallet loading, fork lifts, space for light loads or components needed in assembly lines like robotic arms.
Light load vehicles can be used for small parts distribution and assembly, while much larger vehicles such as towing vehicles can be used for moving heavy and cumbersome loads. Other self-guided vehicles are designed for use in specific environments such as those used in clean room processes and operations. These electric battery powered vehicles are useful in indoor applications where no sudden or essential decisions are made that cannot be done by automated machinery.
Self Propelled Vehicles
Self propelled vehicles, also known as automatic guided vehicles, are able to perform applications without any sort of human direction or control, thus allowing operational processes and tasks to be achieved more efficiently and more often. AGV systems provide high volumes of repetitive movement and can be designed with the capacity for far greater loads and weights than manual labor provides. They also reduce the factor of human negligence in the movement of vehicles and loads, thereby reducing the risk of bumping, crashes and collisions on the manufacturing floor. Self propelled vehicles are typically powered by industrial strength batteries or electricity. Required power capacity will depend on the intended application and load of the vehicle, and can be adjusted to fit custom specifications. Automated guided vehicles were originally designed for use in industrial activities, but have become popular alternatives to manual cart transports, conveyors and forklift trucks in many types of applications.
Towing Vehicles
Towing vehicles, also known as tuggers, are unmanned, computer controlled transport vehicles that are capable of pulling the heavy loads of one or more unpowered, wheeled trolleys. They are one of the most effective types of automatic guided vehicles. Loaded carts, trailers, or trolleys are attached to the AGV and pulled to a location for loading or unloading.
There are various types of guidance systems for AGVs with fixed and free range being the most common. Fixed path guidance systems have sensors placed in the floor, tape, navigation wires, laser target sensors, or ultraviolet light that detects obstacles in the path of the AGV. Free range AGV guidance systems have an on board computer that has been programmed with a map of the facility. Initially, the AGV uses the map to determine its path. In many ways, free range AGVs are like robots and operate independently.
The load capacity of an AGV is determined by its size and its motor. Each type of AGV has a different type of motor and pulling capacity. Typical capacity for an average towing vehicle is one and half tons or 3300 pounds (1496 kg) with large models being capable of towing 20 tons (18143 kg). Magnetic guided towing vehicles travel at 195 ft per min (60 m per min) while ones with laser navigation systems can travel at 780 ft per min (240 m per min).
The most common type of battery for towing vehicles are 24V and 48V GEL batteries. Smaller lighter towing vehicles use 24V batteries while larger more robust towing vehicles use 48V batteries. Specially designed towing vehicles can have multiple batteries for longer operational times before needing a charge. With a full charge, towing vehicles can operate ten hours. Multiple battery towing vehicles can run for 24 hours before needing a charge.
Towing vehicles are often used in conjunction with other AGVs such as transfer cars or material handling robots. They allow workers to move large numbers of carts efficiently without the need for manual labor. Towing vehicles create a safe work environment and significantly increase productivity. They are used by the metal processing industry, warehouses, the automotive industry, food processing, agriculture, aerospace, construction, communications and the military.
Autonomous Mobile Robots (AMRs)
Autonomous mobile robots are capable of performing tasks and completing applications without human interference. They are programmed to gather information about their environment such that they are capable of avoiding harmful situations and adapting to their surroundings.
Simple forms of autonomous mobile robots have infrared or ultrasound sensors that allow them to navigate facilities without the need of human control. More advanced forms of autonomous mobile robots are able to see their environment using stereo vision, cameras with depth perception, and location software that classifies obstacles and objects in real time.
Autonomous mobile robots alleviate humans from doing mundane tasks such as delivering reports, distributing mail, and picking up items. The basic difference between autonomous mobile robots and factory robots is the mobility of autonomous mobile robots and their decision making programming. They are not fixed or set in a single location but are capable of traveling the full expanse of their environment without the need of human control.
The four basic types of autonomous mobile robots are collaboration robots, inventory transportation robots, scalable storage picking robots, and automatically guided vehicles (AGVs).
Collaboration Robots - Collaboration robots are designed to put away, pick, count, replenish, and sort materials. They receive orders for a task to go to a pick location where there is an operator waiting to place a product on the robot or remove a product to be placed on a shelf.
Inventory Transportation Robot - Inventory transportation robots are designed to deliver goods to a person and be part of the picking system of a warehouse.
Scalable Storage Picking Robots - Scalable storage picking robots are another form of robot that delivers goods to people. They are capable of climbing racks to pull or pick coded and numbered cartons. Scalable storage picking robots require specially designed racks with the correct dimensions.
Automatically Guided Vehicles (AGVs) - AGVs are heavy duty robots that are designed to move pallets and carry large bulky materials. There is a wide assortment of AGV models with ones that follow a track while others are guided by sensors.
AGV Forklifts
An AGV forklift, also known as an ALT, is a computer controlled self driven forklift that is capable of lifting loads, moving equipment, and doing all of the activities of a manned forklift. They are programmed with a series of instructions or commands that tells them what tasks they are to perform. AGV forklifts are designed using the same parameters as human driven forklifts with the elimination of the driver.
As with all forms of forklifts, AGV forklifts are capable of horizontal and vertical movement and lifting. They can do stacking, remove pallets from assembly operations, and load trucks. AGV forklifts are a part of a highly complex control system made of several types of robot and computerized devices. When a task is to be completed, an AGV forklift receives its instructions from the central control of the system. The instructions are written in code and involve the completion of simple tasks such as moving an item from one location to another location.
Communication between the AGV forklift and the control system is via wifi. Once commands are delivered, the AGV forklift navigates to the location given by the instructions using its navigation system. Sensors and other components of the navigation system keep the AGV forklift from running into obstacles, walls, or people. The system is similar to the one used in EV automobiles, which tells the driver they are out of their lane and stops the vehicle if it gets too close to another vehicle. When the AGV forklift has completed its task, it notifies the central control system.
The cost of an AGV forklift varies according to its load capacity, lifting height, and type of battery. Prices can vary from around $50,000 up to close to $200,000. As the price of an AGV forklift goes up, the number of features and capabilities increases. Small pallet mover AGVs can cost between $50,000 and $70,000. AGV forklifts that can pick items from a storage rack that is several feet high can cost close to $200,000 but have exceptionally robust capabilities.
The types of AGV forklifts include pallet movers or pallet jacks, pallet stackers, counterbalanced fork trucks, staddle vehicles, very narrow aisle (VNA) AGVs, and reach trucks. Of the various types, counterbalanced fork trucks are designed for the highest load capacity with average reach. VNAs do not have the load capacity of counterbalanced trucks but can be used in narrow aisles with high racking.
Heavy Burden AGVs
Heavy burden AGVs or heavy AGVs are customized AGVs that are designed to move exceptionally heavy loads such as printing press paper rolls, steel coils, production engines, and large vehicles. They perform the requirements of unique applications with specialized lifting and load capacities but have nearly the same maneuverability as smaller AGVs. During their assembly, they are put through punishing cycles and tests to ensure their effectiveness and safety.
The structural design of heavy AGVs makes it possible for them to lift 165 tons (150 metric tons) and carry tools. They have communication systems that are similar to small AGVs that help them coordinate their movements. Heavy AGVs have several servo lift arbors and suspended wheel assemblies and caster assemblies. As with smaller AGVs, heavy AGVs provide precision control with a location error factor of +/- 0.06 inch (+/- 1.5 mm) at pick locations. Due to their size and the weight of their loads, heavy AGVs move at a slower speed per feet or meter than smaller AGVs.
Common types of heavy AGVs are:
Heavy Towing Carriers - Heavy towing carriers move loads over long distances using variance guidance systems.
Tugger AGVs - Tugger AGVs pull loads using trailers and can be programmed to stop along their route to unload products or parts.
Unit Load AGVs - Unit load AGVs are cargo delivery systems capable of traveling long distances in a warehouse. They are transport AGVs for industrial goods, heavy materials, and equipment.
Underride AGVs - Underride AGVs are the most common type of heavy AGVs. They position themselves under carts, trollies, and other payloads. They connect to their loads using tow pins or lift modules and can perform several functions depending on their design.
Conveyor Replacement - Conveyor replacement heavy AGVs perform as conveyors for the assembly and transport of heavy bulky material that do not fit on a conveyor or is beyond the capacity of a conveyor. They move using various navigation methods including magnetic tape and wires.
Top AGV Manufacturers
Red Viking
Red Viking, a Michigan based company, manufactures a wide variety of industrial production equipment including heavy AGVs for truck and equipment assembly. Many of their products are engineered, designed, and built to meet the unique needs of industrial assemblies and include manufacturing solutions, test systems, operational intelligence systems, and assembly solutions, especially for heavy equipment. Red Viking AGV solutions include tugger AGVs, conveyor AGVs, heavy AGVs, and part delivery AGVs.
DEMATIC
DEMATIC is a rapidly growing manufacturer of material handling AGVs and AGV and AMR software that was founded in Germany over two hundred years ago as Mechanische Werkstätten Harkort & Co. They produce AGVs for automatic storage, retrieval, and picking in warehouses. Using their proprietary software, DEMATIC AGVs assist in enhancing warehouse management systems by helping maintain consistent fluid material flow. They manufacture staddle AGVs, high reach AGVs, narrow aisle AGVs, tugger AGVs, and work with customers to develop custom solutions for unusual material handling problems.
International Data Corporation (IDC)
IDC, a Michigan based company, specializes in automated guided carts, tonnage monitors, and industrial control systems. The main emphasis of IDC is various types of controllers and PLCs. IDC’s carts use magnetic tape as their guidance system. The different models support operations including simple delivery routes and multiple destination deliveries. IDC’s AGC vehicles can have automatic charging stations with PLC controllers that interface with a company’s information system.
Daifuku
Daifuku manufactures AGVs for automated retrieval and storage (AS/RS) operations for factories and distribution centers. Their AGVs operate using a wireless communication laser guided system that allows the AGV to autonomously move through a facility. Daifuku also has wired, inertial, and magnetic tape options in various sizes for a wide range of transport loads. They offer AGVs to replace conveyor lines, forklifts, and handcarts.
Transbotics
Transbotics designs, engineers, and installs heavy load AGVs, forklift AGVs, and tugger AGVs and provides customers with specialized custom designs for unique and unusual applications. Their AGVs have lithium batteries with blue LED directional spotlights, laser bumpers, and touch screen panels for vehicle assessment and status. Transbotic forklift AGVs have a load capacity of 1800 kg (2 tons) and have a counter weight for handling heavy payloads. Tugger AGVs manufactured by Transbotics have a towing capacity of 29000 kg (32 tons) and are designed to meet the needs of any industrial operation or warehousing application.
Common AGV Components
Every AGV manufacturer has their version of the configuration of their vehicles to ensure quality performance, efficiency, and productivity. Engineers work to improve the various components to differentiate their equipment from their competition and to provide customers with a unique experience. Regardless of how the various parts of an AGV are assembled, all AGVs necessitate the use of the same basic components that may be configured differently for each brand.
The core components of AGVs are a set of individual systems that include safety systems, navigation systems, control systems, motion systems, power systems, user interface systems, and connectivity systems. Every AGV will have all of these systems with different orientations and placement.
AGV Safety Systems
The purpose of AGVs is to alleviate personnel of mundane and repetitive tasks to increase and improve productivity. When an AGV is activated to complete a task or routinely moves about a facility, it must perform in such a way that prevents damage to people, objects, and its environment. AGV safety features, such as lasers, help to detect and avoid obstructions.
Safety systems use sensors such as LiDAR, cameras, and ultrasonic sensors to identify, avoid, and circumvent potential hazards. When an AGV identifies a hazard, it may wait for the obstacle to be removed or go around it. A drive monitor, that is essential to the system, combines all safety scanners into a single solution. The travel guide is monitored using the safety encoder and the drive monitor. The steering position is compared and evaluated against other parameters.
Like an EV automobile, AGVs have warning fields that indicate how close it is to an obstruction. If the safety controller detects an obstruction in one of the levels of its warning fields, it instructs the control system to reduce speed. The drive monitor detects the change in speed and adjusts the warning and protective fields. When placing a load, changing direction, or moving along a path, a breach in the warning field immediately causes a reduction in speed. If the red field, closest to the AGV, is breached, the AGV immediately stops.
Although the safety system is closely monitored and reacts immediately to obstacles, there may be occasions when an AGV may have to be stopped faster than the system can react. On those occasions, an emergency stop button is available that can be manually activated to avoid major threats and potential harm to others and the AGV.
AGV Navigation Systems
The main system of an AGV is its guidance system that helps it navigate through its tasks and positions it correctly. There are several forms of navigation systems with new ones being introduced that include innovations and new technologies to improve accuracy and performance. Regardless of the type of system, the navigation system localizes and navigates an AGV through its surroundings.
None of the systems on an AGV operates independently. Each of them communicates with each other to ensure the optimum performance of the AGV, which includes the navigation system that communicates with the safety system and vehicle control system. The fundamental part of a navigation system is sensors that are positioned on the exterior of the AGV.
The two types of navigation systems are fixed path and free range. Fixed path systems are guided by wires, tape, or wall sensors. Their path is marked so vehicles or people cannot interfere with the operation of the AGV. Unlike fixed path vehicles, free range systems have a programmed path that does not require any external devices as guidance. They are programmed to make adjustments to avoid collisions and hazards that may interfere with their programmed task. Installation is easy and does not require any major changes to the work environment.
The types of sensors include:
Magnetic Sensors: Magnetic sensors are one of the oldest forms of AGV sensors. The AGV follows magnetic tape placed on the floor. Magnetic sensors can be adjusted by changing the placement of the tape.
LiDAR Sensors: LiDAR sensors are more sophisticated navigational sensors and allow an AGV to move freely. They are able to recognize obstacles and localize an AGV.
Optical Sensors: Optical sensors are the eyes of an AGV. They use vision recognition systems to detect landmarks and the environment of the AGV using sophisticated software to determine an AGVs location and position.
Inertial Measurement Units (IMU) Sensors: An IMU measures angular force and velocity using an accelerometer and gyroscope. The accelerometer measures speed while the gyroscope measures angular velocity. Together, they provide a six dimensional time series stream measurement. The data collected by the IMU assists in the calculation of position and trajectory of an AGV.
AGV Vehicle Control System
AGV’s vehicle control system regulates its speed and actuators such as motors, brakes, and steering. The adjustment of speed is necessary when going around curves, passing through controlled areas, and avoiding contact with other vehicles and people. The AGV vehicle control system is responsible for coordinating the vehicle's motion such that it performs accurately with precision.
AGV Batteries
An AGV battery provides power and energy for the operation for an AGV. They store energy that is supplied to the other systems. The best type of battery is determined by its charging system since the battery and charging system work in unison to provide optimal performance. The three types of charging systems are opportunity, battery swap, and automatic.
Opportunity charging refers to charging the battery of an AGV when time permits. It is unlike parking an AGV in a charging station for it to receive a complete charge. The charging process lasts for a short period until the AGV receives instructions for its next task. Charging takes place at various times during the work day such as breaks, shift changes, pauses in activities, or other opportune moments. Opportunity charging allows a battery to be used continuously without being swapped out.
Battery swapping is changing one battery for another battery with the first battery having used up its charge and needing to be charged. It is a manual or automatic process that requires the use of multiple batteries. With the manual process, an operator makes the determination that the battery needs to be replaced. Automated systems have a machine capable of removing the old battery and replacing it without assistance.
The types of AGV batteries are GEL batteries, AGM lead batteries, lithium batteries, and flooded lead acid.
GEL Batteries - GEL batteries use sulfuric acid mixed with fumed silica to produce a gel like substance. The gel material holds the lead plates and active materials in their position. It combines the electrolyte and plates into a single unit. During discharge, the negative plate absorbs the oxygen from the positive plate, which causes the negative plate to produce water to help the batter maintain its water content. GEL batteries are known to be maintenance free and spill and leak proof but should not be used for opportunity charging.
Absorbent Glass Mat (AGM) Batteries - With an AGM battery, the electrolyte is held in place by separating membranes, which gives them the name of membrane batteries. The membrane is made of fiberglass mat that functions like a sponge. The thin plates of an AGM battery allows for the placement of more positive plates for maximum surface area exposure to provide greater energy density. Electrolyte absorption happens very slowly, which increases battery life.
GEL and AGM batteries are sealed lead acid (SLA) and valve regulated lead acid (VRLA) batteries with similar attributes. Both are non-spill, maintenance free, have deep cycles, low rates of discharge, have no gas emissions, and do not require any special handling. These characteristics make them ideal for use in AGVs. GEL batteries can last for 12 to 16 hours before needing a recharge while an AGM battery can last 40 hours before needing a charge.
Lithium Batteries - Lithium batteries have recharging cycles of 5000 cycles compared to 1500 cycles to 1800 cycles for GEL and AGM batteries. With lithium batteries, lithium ions move between the cathode and anode internally while they move in the opposite direction externally. The movement is the factor that creates electrical current. During discharge, the anode releases lithium ions to power an AGV. When the battery is charging, lithium ions are released to the cathode to later be received by the anode.
Flooded Lead Acid Batteries - When a flooded lead acid battery is charged, the battery acid and lead plates store electricity. The bonding of the acid with the lead plates creates electric current that is sent through an electric circuit. Water has to be added to the battery such that it can maintain its liquid level. For many years, flooded lead acid batteries were used in cars and were the stand for batteries. Flooded lead acid batteries require regular monitoring and examination to ensure proper performance.
AMR or AGV robots vs AGV – Robots vs Guided Vehicles
For over fifty years, AGVs have been an important addition to the movement of materials and the improvement of production methods. Their ability to save time and increase efficiency has made them one of the most popular innovations in modern warehousing and production. In the last few years, as robotic technology has advanced, AGVs have had their abilities enhanced with the development of the AMR, autonomous mobile robot.
The biggest difference between AGVs and AMRs is how much faster, smarter, and more efficient AMRs can be. AGVs follow a guided pre-programmed route and can only obey simple instructions. When there is an obstruction in their path, they are unable to adjust and change. Expanding their applications requires time consuming programming.
An AMR has an onboard computer with sensors to evaluate its operating environment. They can navigate a complicated set of restrictions using an uploaded map that allows them to select the most efficient route to their destination. They can react to people, vehicles, and unplanned obstructions while successfully and safely completing their job. The chaos and confusion of the surrounding environment does not interfere with the completion of their tasks.
AMRs do not require any adjustments to their work environment with the exception of adding a map to their programming. There isn‘t any need for laser sensors, guiding tape, or installing special pathways. Instead of adapting the working conditions to the AMR, it adapts to fit the situations and can be easily adjusted. These two factors make an AMR less expensive than an AGV.
A properly programmed AMR can quickly and efficiently complete an assembly process, make tooling changes, and finish complex tasks more precisely than humanly possible. Using robotic technology has the advantage of freeing people from dangerous and hazardous tasks since an AMR can enter any environment without a concern for its health or safety.
AGV Guidance and Navigation Systems
One of the main things to consider when shopping for an AGV system is the type of computerized navigation it uses. Every industry and user has a different set of requirements for how to implement AGV‘s, which dictates the type of navigation system. In general, the guidance system determines the route and functions of the AGV. The performance of the AGV is very dependent on the quality of the system and the way it is installed.
There are a wide variety of guidance systems that manufacturers use for AGV vehicles. They vary depending on whether they are fixed path or free ranging and include laser guided navigation (LGV), magnetic navigation, LiDAR NAVIGATION, magnetic spot navigation, wired navigation, optical navigation, or vision navigation. Each of the different types has benefits and are designed for specific purposes. Below is a short description of each. A more technical description can be found at the individual manufacturers‘ websites.
LGV – Laser Navigation:
The LGV system uses a laser positioning device mounted on the top of the vehicle. Targets, located in its workspace, guide it. The navigation system sends laser signals to the targets, which sends signals back to the AGV navigation device. Three targets are required for the AGV to find its position. Corrections are made every 30 to 40 seconds. By industry standards, LGV‘s are incredibly accurate and easy to install.
Magnetic Tape:
Magnetic tape AGVs are equipped with magnetic sensors and follow a clearly defined path that is marked by magnetic tape. The tape induction system can be modified to account for line changes. The sensor measures the distance from the center of the tape and sends the information to the controller to adjust steering and path so that the AGV is always centered on the tape.
LiDAR Navigation:
LiDAR navigation is also referred to as natural navigation. This system maps the environment with an assortment of sensors such as cameras, lidar, and lasers that are used for safety purposes. All of the data is combined with an internal inertial measurement unit (IMU) to help the AGV define and calculate its position. The array of calculations are made by a complex algorithm called SLAM (simultaneous localization and mapping).
Magnetic Spot Navigation:
For magnetic spot navigation, magnets are embedded in the floor for the AGV to follow at approximately 15 feet apart. The AGV moves from one spot to the next using sensors and controls such as half effect sensors, encoders, counters, gyros, and other such encoders to steer and guide the vehicle. A CAD drawing of the workspace is loaded in the system to serve as a reference. As with magnetic tape, installation is easy and quick.
Wired Navigation:
When Mr. Barrett invented the first AGV, he hung a wire from the ceiling to guide the tug. As he worked on his device, he changed the position of the wire in the ceiling and embedded it in the floor. Though technology has advanced, his original wire design is still used by some manufacturers. All that is required is burying a wire guide about one inch in the floor. It transmits signals to the AGV giving it its location to regulate steering.
Optical Navigation:
Paint or colored tape is placed on the floor of the workspace. A built in sensor detects the path. There are systems that use ultraviolet light to light up the paint or tape. Highly sensitive cameras are able to recognize the AGVs path and position.
Vision Navigation:
Vision activated systems use cameras that record the main features of the AGVs programmed route. Using vision sensors, the AGV system gets image information regarding its workspace. The system requires a camera, light, and hood to measure the ground texture. When navigating its workspace, the onboard system compares the recorded ground to its map to determine its position. The system is very accurate and has low hardware costs.
Automatic Guided Carts
Automatic guided carts are a flexible and a less expensive alternative to an AGV system. Since they are smaller and more maneuverable, they have more versatility and can be easily adjusted. Their capacity varies depending on the manufacturer and model. Most can carry up to 2000 lbs. and tow loads heavier than they can carry. As with AGV‘s, each type has a different form of navigation.
Carts are an excellent alternative to conveyors or forklifts since they are cleaner, quieter, and easier to modify. They provide a fast and safe stream of products to and from selected areas and can be modified for non-production jobs such as warehouse organization.
The immediate benefit of a cart system is its low cost compared to labor costs. Materials flow easily and are quickly and readily available for operators. It only takes a few hours to upgrade a production environment with a cart system. Additional carts can be purchased and easily integrated into the existing system. The number of carts can be adjusted with variances in production. Since material handling removes the human factor, the installation of a cart system results in a significant decrease in accidents and other potential hazards.
The Benefits of Going Automated
Manufacturers have found that by using automation, they can significantly reduce errors and costs while raising quality and improving machine performance. Implementation of computer driven mechanisms increases production and efficiency approaching the point of perfection. Jobs that seemed to be impossible can be completed with ease in little time.
Initially, investing in an AGV system can be expensive requiring significant adjustments to manufacturing operations as well as the cost of the equipment. Once the system is in full operation, there is a noticeable reduction in labor costs with an increase in efficiency to balance the costs of implementation. Related additional savings can be seen in the reduction of labor.
Production environments have unsafe and hazardous conditions that include dangerous materials and substances. AGVs are perfect for those circumstances, which may endanger workers. The aircraft industry has huge engine components and parts that workers are unable to lift and can be lethal if they fall. AGVs are used to avoid damage to the materials and keep workers safe. In some cases, AGVs are equipped with robotic limbs to perform functions that require superior dexterity and strength, such as tooling changes.
The decision of what AGV system is best for your operation should be based on the needs of your facility. Every industry has their unique and specialized conditions. A close examination of each step of a process assists in determining where to place an AGV unit. As with all business decisions, the cost of a system can be a primary determining factor. AGV manufacturers have data that provides guidance to help in making a purchase choice. They are more than happy to assist with implementation and offer details on their system works.
AGV Safety and Compliance Standards
The American National Standards Institute (ANSI) has approved the standards proposed by the Material Handling Industry of America (MHIA), which has developed standards and guidelines regarding the implementation and use of Automatic Guided Vehicle Systems. The MHIA standards are safety requirements for system suppliers, manufacturers, users, construction, application, operation, and maintenance.
The Material Handling Industry of America (MHIA), in 2012, set forth the safety standards for driverless, automatic guided industrial vehicles and other automatic industrial vehicles. The standards cover every aspect of AGV equipment from the bumpers to the types of required emergency controls. The requirements also have guidelines regarding manned vehicles that have been converted to unmanned.
To be able to market an AGV vehicle, a manufacturer should be certified by the MHIA in several categories. The first category is a set of general requirements for AGV and other industrial equipment. The other categories are more specific to AGVs such as the type of permitted wireless components and includes a section on types of permitted batteries, chargers, motors, and other electrical components.
When making the choice to purchase an AGV system, it is wise to research manufacturers regarding their compliance with the MHIA regulations. In many ways, it is a protective umbrella to help avoid a bad investment.
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