In manufacturing plants and logistics sites, the process of “moving things” generates no direct added value, yet it has continued to consume large amounts of labor and time. In the manufacturing industry across Thailand and the wider ASEAN region in particular, structural challenges such as changes in the working-age population, rising labor costs and difficulty securing skilled operators are becoming more visible year by year. Against this background, attention is rapidly growing for automated guided vehicles (AGV: Automated Guided Vehicle) and autonomous mobile robots (AMR: Autonomous Mobile Robot) that take over transport work. Among these, the tugger AGV (cart towing) — which excels at high-volume transport, long-distance transport and inter-process transport — is positioned as an extremely cost-effective automation solution at sites handling heavy items, such as automotive parts plants and machine parts plants.
TOMAS TECH CO., LTD. is based in Thailand and provides end-to-end, shop-floor-driven IT integration to manufacturing and logistics customers, including Japanese-affiliated companies — from production management systems and energy management systems through to the automation of in-plant logistics. This article explains, from a practical standpoint, the mechanizm and characteristics of tugger AGVs, how they differ from other transport methods and how to choose between them, the specific challenges sites face, the benefits gained through deployment, typical application scenarios, the selection of guidance methods, the design of towed carts and fixtures, integration with host systems, the deployment process and timeline, the checkpoints to confirm before deployment, the maintenance and support structure, and finally frequently asked questions. We hope it will help you select a method and organize your requirements as you consider transport automation.
What is a tugger AGV — mechanizm and characteristics
As the name suggests, a tugger AGV is a type of AGV in which a self-propelled vehicle body “tows” multiple trailers or carts in order to transport goods. A tractor (tow vehicle) leads at the front, with carts loaded with goods (dollies, trailers, roll cages and so on) coupled behind it in a chain, allowing a large quantity of goods to be moved together in a single trip. It is easiest to picture it as the relationship between a manually driven tow tractor and its carts, made unmanned and automated exactly as it is. The tugger type tows multiple trailers or carts to move large volumes of goods efficiently, and it is widely used in plants handling heavy items such as automotive parts and machine parts. Its greatest characteristics are that carrying multiple loads at once dramatically improves work efficiency, that layout changes and additional carts can be accommodated flexibly, and that it is well suited to long-distance transport and specialized for use in large facilities.
Basic structure of the tractor and coupled carts
The components of a tugger AGV can be broadly divided into two parts: the tractor (the tow vehicle itself) and the towed carts (trailers and dollies). The tractor carries drive wheels, a steering mechanizm, a battery, various sensors, and the equipment required for guidance and position recognition. The carts, on the other hand, are simple structures for carrying goods, equipped with wheels and a towing coupling section (coupler, hitch, coupling pin, and so on). As the tractor pulls the carts, several carts move along in a single line. The design philosophy of giving the carts no power of their own and moving them purely by the tractive force of the tractor makes it possible to prepare carts inexpensively and in large numbers, and to flexibly increase or decrease the number of coupled carts according to the volume of goods to be transported. This is what underpins the rationality of the tugger type.
The number of carts to be coupled (the number of towed units) is determined by comprehensively considering the tractor’s driving and braking force, the curve radius of the travel route, the gradient of the floor surface, and the braking distance required to stop safely. Generally, the more carts are towed, the greater the volume of goods that can be moved in one trip; however, the overall length also increases, so the difference in turning radius between front and rear wheels on curves, the space required to turn, the behavior during acceleration and deceleration, and the risk of rear-end collision during emergency stops must all be designed with care. At TOMAS TECH, we place importance on optimizing this vehicle formation design in line with the site layout and transport requirements.
The mechanizm that enables automatic coupling and unmanned operation
The key to making tugger AGV operation truly “unmanned” is the mechanizm for automatic coupling and uncoupling between the tractor and the carts. In conventional manned towing work, operators coupled and uncoupled carts by hand; by automating this, people can be removed from the entire transport flow. Automatic coupling mechanizms come in various forms depending on how the site operates: a method in which the tractor approaches the cart’s coupling section and automatically engages a pin or hook, a lifting type that raises the cart from the floor to tow it, or a method in which the whole cart train is left at a designated position and only the tractor detaches and re-couples.
In operations built around automatic coupling, the tractor can continuously perform a whole cycle of movements unmanned: collecting an empty cart train, exchanging it for a fully loaded cart train at a loading station, transporting it to the destination, uncoupling the carts there and heading off to the next task. This makes it possible to build an extremely efficient logistics flow in which the utilization of the relatively expensive self-propelled tractor unit is maximized, while large numbers of inexpensive carts are positioned around the site and used as “mobile temporary storage”. The economic rationality of the tugger AGV is rooted precisely in this design philosophy of “separating the tractor from the carts”.
Differences from other transport methods and how to choose
AGV and AMR transport methods fall broadly into three types: the tugger type, the low-profile type (latent / lifting / conveyor types) and the forklift type. Each type has different strengths, so the key point when choosing a transport method is to select it based on the automation requirements you want to achieve, the process, the work content and the goods to be moved. Here we organize the characteristics of each method and then clarify what kind of site the tugger type suits.
Differences from the low-profile type (latent / lifting)
The low-profile, lifting type is designed to raise goods at a low position close to the ground, making it suitable for transporting heavy items and pallets. It has high transport capability and is widely used in distribution centers and on production lines, and it is sometimes used as a substitute for forklifts in plants and warehouses. Because the vehicle height is low, the latent type — which slips underneath a cart and lifts it — can transport smoothly even in narrow spaces with height restrictions. It can also be used in combination with conveyors to hand goods over. The low-profile type is fundamentally centred on “one-to-one” transport, in which one vehicle carries one load (or one cart), and it suits fine-grained transport over relatively short distances where the destination differs from load to load.
By contrast, the tugger type performs “one-to-many” transport, towing several carts at once, and it shows its true value in applications that move a consolidated volume in the same direction. If the low-profile type is strong in “small-lot, high-frequency, many-destination” transport, then the tugger type is strong in “high-volume, scheduled, specific-route” transport — that is the basic division of roles. When designing logistics for an entire plant, it is also effective to combine the two, with the tugger type handling high-volume trunk-line transport and the low-profile type handling fine-grained delivery at the end points.
Differences from the forklift type
The forklift type has the ability to automatically lift and transport pallets and heavy items. This removes the need for manual operation and greatly improves both the safety and the efficiency of the work. It can handle a wide variety of cargo and can be deployed or adjusted quickly as needed across various logistics and manufacturing processes. The greatest strength of the forklift type lies in “vertical transport”: it can pick up pallets from various heights — racks, the ground, the end of a conveyor — and store them at any height. For applications such as warehouse receiving and shipping, or storing and retrieving goods by the pallet, the forklift type is the most suitable choice.
The tugger type, on the other hand, fundamentally has no function for lifting goods vertically; it specializes in moving goods loaded on carts “horizontally”, in large volumes and over long distances. Accordingly, the practical criterion for choosing between them is a two-axis judgement based on the vector of transport (vertical or horizontal) and the volume (one-to-one or one-to-many): the forklift type if the main purpose is storing goods in racks, and the tugger type if the main purpose is high-volume horizontal movement between processes or between sites. At many sites, rather than choosing exclusively among these three methods, the optimal method is combined process by process to optimize logistics as a whole.
Comparison with single-load transport
In general, compared with “single-load transport”, in which one vehicle carries one load at a time, the “coupled transport” of the tugger type achieves dramatically higher transport efficiency when traveling back and forth over the same distance. For example, when moving ten carts’ worth of parts from one process to another, single-load transport would require ten round trips, whereas coupling five carts with a tugger reduces this to two round trips, and coupling ten carts to just one round trip. Fewer trips mean less traffic in the aisles and a lower risk of interference with other vehicles and workers. The longer the distance and the greater the transport volume, the more pronounced the advantage of coupled transport becomes. The reason tugger AGVs are chosen in heavy-item plants and large facilities lies precisely in this efficiency gained by “moving things together”.
Transport challenges faced on the shop floor
To understand the value of the tugger AGV correctly, it is essential first to grasp in concrete terms the transport challenges that sites actually face. Here we organize the typical challenges frequently seen at heavy-item manufacturing sites such as automotive parts plants and machine parts plants.
The burden of high-volume and long-distance transport
In large plants, an enormous quantity of goods moves around the premises every day: supplying parts from the raw material warehouse to each production line, moving work-in-progress between lines, transporting finished goods to the finished goods warehouse, and so on. Receiving, storage and shipping are each carried out in separate locations, and every time the process changes, another “transport operation” arises. When this transport is carried out by hand, by forklift or by a manned tow tractor, the longer the transport distance and the greater the volume, the more personnel, vehicles and time are required. At plants with large premises in particular, a single operator may walk or drive a considerable distance in a day just for transport, and because this time is not value-adding work in itself, it is recognized as an inefficiency with substantial room for reduction.
On-demand inter-process transport and idle waiting
At sites where processes are located apart from one another, transport must be designed to match the distance between processes and the required speed. “On-demand transport” — moving work-in-progress to the next process when it accumulates at the previous one, or supplying parts at the moment the next process needs them — leads to idle waiting or shortages when the timing slips. With manual transport, if the transport staff are occupied with other work, transport is delayed, which in turn can stop the production line or force the site to hold excessive work-in-process inventory. There are many cases in which the inability to stably control the timing and volume of transport adversely affects overall production lead time and inventory levels.
Labor shortages and human error
Transport work is simple work, yet it places a heavy physical burden on the body and requires a certain number of people to be permanently assigned to it, which makes it an area highly susceptible to chronic labor shortages. When employees are dissatisfied with their workload or conditions, it easily leads to turnover, and recruitment and training costs are incurred continuously. In addition, manned transport always carries the risk of human error, such as mistaking the destination or quantity, incomplete cart coupling, or contact accidents in the aisles. Automating transport reduces the burden on workers, improves job satisfaction, health and safety, and consequently contributes to employee retention. Even with AGVs and AMRs there are still opportunities for people to be involved, such as motion settings and maintenance, but even so, the frequency of human error can be reduced dramatically compared with manual logistics work.
Benefits of deploying a tugger AGV
What specific effects can a site expect from deploying a tugger AGV? Here we systematically organize the benefits from the perspectives of transport efficiency, labor saving and layout flexibility.
Overwhelming efficiency from transporting several loads at once
The greatest benefit of the tugger AGV is that it can couple multiple carts and carry a large volume of goods in one trip. Because several carts’ worth of goods can be transported together in a single run, the number of trips required to achieve the same transport volume falls significantly. This means high transport productivity per tractor, which translates into covering a large transport capacity with a small number of vehicles. The greater the transport volume and the more the destinations are consolidated, the greater this “batch transport” effect becomes, which directly shortens the payback period on the investment.
Labor saving and cost reduction
Introducing AGVs and AMRs contributes greatly to cost reduction in both the short and the long term. These robots automate the movement and transport of goods within the plant without depending on human workers. In particular, in regions where labor costs are trending upward, being able to replace work that is simple yet labor-intensive with AGVs makes it possible to hold operating costs down substantially. Because the tugger type moves many carts at once, personnel who were tied to transport work can be reassigned to higher value-added processes. This achieves a division of roles in which people concentrate on judgement, adjustment and improvement work that robots are not good at, while robots take on routine horizontal transport.
Higher productivity and stable quality
Compared with human workers, AGVs and AMRs do not tire and continue to maintain consistent performance, so they can significantly improve productivity. Because they recognize their environment using dedicated sensors and software and autonomously execute programmed tasks, transport work is carried out quickly and accurately. Stabilizing the timing and volume of transport levels out the supply of parts to production lines and suppresses disruption to production caused by idle waiting or shortages. In addition, reducing human errors such as mistaken destinations or quantities can be expected to lower quality problems originating in logistics. Making transport “predictable” also contributes to improved accuracy in production planning.
Suitability for long-distance transport and layout flexibility
The tugger type is also well suited to long-distance transport and is specialized for use in large facilities. Even on trunk-line transport that crosses extensive premises, it can carry large volumes of goods together, so efficiency is maintained however long the distance. Furthermore, a major advantage of the tugger type is that flexible layout changes and cart additions are possible. Even if the type or volume of goods to be transported changes, the site can respond by increasing or decreasing the number of carts, reviewing the coupling configuration or changing the travel route, so operations can continue flexibly without wasting capital investment even at sites with frequent product changeovers or fluctuating production volumes. The ability to adjust capacity simply by increasing or decreasing an inexpensive element — the carts — is a strength unique to the tugger type when compared with fixed equipment such as conveyors.
Application scenarios for tugger AGVs
Here we introduce, in concrete terms, typical scenarios in which tugger AGVs actually come into their own. Please use this as a reference when considering which processes at your own site might be suitable for application.
Inter-process transport
At sites where receiving, storage, shipping and other operations are carried out in separate locations, and where a transport operation arises each time the process changes, tugger AGVs can be applied to this inter-process transport. It is important to decide the number of robots according to the distance between processes and the required speed, and to precisely design the stop position, transport speed and timing of each robot. With the tugger type, work-in-progress generated at the previous process can be consolidated onto carts and transported to the next process in a single batch, so the flow of goods between processes can be consolidated on a large scale and made more efficient. To ensure that no problems occur at each process, stop positions and similar settings should be configured in coordination with each piece of equipment, and the speed and timing of the transport robots should be finely adjusted to match the required speed — these are the keys to smooth inter-process transport.
Parts supply to production lines
On assembly lines and similar operations, a wide variety of parts must be continuously supplied to each workstation. Because the tugger AGV can couple and move multiple parts bins or parts carts, it is well suited to “line-side supply”, delivering parts together to several stations along a line. By collecting empty parts bins and supplying full ones at the same time, line operators are freed from the task of going to fetch parts and can concentrate on assembly work itself. Circulating the supply of parts and the collection of empty bins makes it possible to keep line-side work-in-process inventory at an appropriate level while building a stable supply system that prevents shortages.
Milk-run circuit transport
The tugger AGV is a method that pairs extremely well with the concept generally known as the “milk run” — circuit collection and circuit delivery. The term milk run originates from milk delivery businesses that toured each farm to collect milk, and it refers to a transport method in which a predetermined route is toured on a fixed schedule, loading and unloading goods or exchanging carts at each point. As the tractor tours multiple stations within the plant in a single continuous loop, collecting empty carts and supplying loaded carts at each location, a single tractor can efficiently cover transport to a large number of points. Because it tours on a fixed schedule along a fixed route, the timing of transport is easy to predict and easy to synchronize with the production plan. The more numerous and dispersed the transport points, the more the efficiency of this circuit transport comes into play.
Coordination with receiving and shipping areas
Tugger AGVs also demonstrate their strength in transport that distributes newly received raw materials to the warehouse or to each process, or that consolidates finished goods from the production area to the shipping area or finished goods warehouse. Because they can move a large volume of goods in one batch, they can efficiently handle consolidated quantities in line with the timing of truck arrivals and departures. Receiving and shipping are processes with large fluctuations in volume, and the ability to flexibly secure peak transport capacity by adjusting the number of towed carts is another aptitude unique to the tugger type. By linking with a host inventory management system, transport instructions can be generated automatically based on receiving and shipping information, realizing logistics in which goods and information are kept consistent.
Types of guidance method and how to select them
The “guidance method” determines how a tugger AGV recognizes its travel route and moves along it. The three representative guidance methods are magnetic guidance / line tracing, the landmark method (images and QR codes), and laser guidance (SLAM). Each guidance method has different requirements at the site and different advantages and disadvantages after deployment. It is therefore important to check the environment and travel routes of the site where the system will be deployed and whether the necessary installation work is feasible, and then to decide the guidance method based on how frequently routes change and on the deployment cost.
Magnetic guidance / line tracing
This is a method in which magnetic tape or an optical line is laid on the floor and the vehicle travels along it. It is characterised by its simplicity and low deployment cost, and because the magnetic tape or optical line serves as a clear marker, the vehicle traces the route reliably, with a low risk of malfunction or deviation and excellent stability. On the other hand, while it suits fixed work processes such as those in mass-production plants, it is difficult to accommodate sudden layout changes or an increase in obstacles, and in terms of flexibility it does not match advanced guidance technologies such as SLAM. It pairs well with tugger applications that repeatedly move large volumes along a fixed trunk route, and at sites where the travel route is essentially fixed it is an option with an excellent balance of cost and stability.
Landmark method (images and QR codes)
This is a method in which the vehicle travels using specific points (landmarks) as references. Using physical markers, artificially installed tags, QR codes, digital signals and the like, the vehicle accurately grasps its own position while operating along the route. The landmark method offers a relatively high degree of freedom and flexible operation, and it is characterised by being more robust to changes such as complex route settings and the addition of new tasks than conventional fixed-route methods. Methods such as applying QR codes to the floor in a grid pattern to serve as position references make it easy to add or change routes in software, and they are adopted at many sites as an option that balances flexibility and cost midway between the magnetic tape method and the SLAM method.
Laser guidance (SLAM)
SLAM stands for Simultaneous Localization and Mapping. It is a technology that enables autonomous travel by having the moving body estimate its own position and create a map of the environment at the same time. Applying SLAM to AGVs eliminates the need for physical guides or markers and makes autonomous travel possible even in complex layouts and changing environments. Because there is no need to lay tape or markers on the floor, it suits sites where layout changes are frequent or where aisle conditions change dynamically. Creating the map and tuning the system in the initial deployment phase requires a corresponding amount of technical work, but once it has been built, the ability to change routes flexibly in software is a major attraction. For the tugger type as well, the SLAM method is chosen when freedom in the travel route is a priority, or when installing anything on the floor is to be avoided.
How to think about selecting a guidance method
When selecting a guidance method, the starting point is to determine how frequently the travel route will change. If the route is essentially fixed and will not change for a long time, magnetic guidance / line tracing is a strong candidate thanks to its cost and stability. If a certain degree of route change and task addition is expected, the landmark method offers an excellent balance of flexibility and cost. If frequent layout changes or complex, dynamic environments must be accommodated, the SLAM method is appropriate. In addition, it is essential to comprehensively consider the condition of the floor (whether tape can be laid), the initial deployment cost, future expandability and the required positioning accuracy, and to choose the method that best fits the actual conditions of the site. At TOMAS TECH, we propose the optimal guidance method based on a site survey and on these trade-offs.
Design of towed carts and fixtures
To maximize the effect of deploying a tugger AGV, the design of the towed carts (trailers and dollies) and of the fixtures that hold the goods is just as important as the tractor itself. Carts and fixtures must be designed to match the load form and transport requirements of the site, and how thoroughly this part is worked out has a major influence on the stability and efficiency of operation.
Design of the coupling mechanizm
The mechanizm that couples carts to one another, and the tractor to the carts, is the linchpin of safe and reliable towed transport. The coupling section requires strength to withstand the vibration and the acceleration and deceleration of travel, together with the mechanical precision needed for automatic coupling. Because each cart must follow appropriately when traveling around curves, the degree of freedom of the coupling section (the swivel angle) and the wheel arrangement of the carts (the combination of fixed and swivel castors) are designed to match the minimum curve radius assumed. Reliable coupling is indispensable for preventing rear-end collisions and cart deviation, and from the standpoint of safety design it is also important to build in sensors that detect the coupling state so that an uncoupled or disconnected condition can be identified.
Accommodating loads and load forms
The shape, weight and dimensions of the goods placed on the carts vary widely from site to site, so loading fixtures must be designed to match each load form. The optimal configuration is selected according to the goods: shelf-type carts on which parts bins are arranged neatly, flat carts on which pallets are placed as they are, roll cages, or dedicated fixtures matched to a specific part shape. The design points are to hold the goods securely so that the load does not collapse during transport, while at the same time ensuring that loading and unloading remain easy to perform. The load capacity of the carts is set with consideration for the balance with the tractor’s driving and braking force, so that the transportable weight can be carried while still traveling and stopping stably.
Measures for changeovers and high-mix production
At sites handling a wide variety of products, the type of goods to be transported may change with each product changeover. At such sites, making carts and fixtures too specific to individual product types can mean carts have to be swapped out at every changeover, which is counterproductive. For this reason, measures that minimize changeover effort are required — for example, versatile cart designs that can be used in common across several product types, or designs in which only the fixture section is exchanged while the cart body is shared. Designing for easy expansion and reconfiguration of carts, with an eye on future additions of product types and fluctuations in production volume, allows the investment to be used effectively over the long term. It is important to see the design of carts and fixtures not as the mere design of components, but as the design of the site’s operations themselves.
Integration with host systems
To operate multiple tugger AGVs efficiently and to keep the logistics and the information of the entire plant consistent, integration with a host system that supervises the vehicles is indispensable. By looking beyond simply moving individual vehicles to encompass fleet control, traffic management and integration with production and inventory management systems, the effect of transport automation is heightened still further.
Fleet control and traffic management with RCS
At sites operating multiple AGVs, the “robot control system” (RCS: Robot Control System), which assigns tasks to each vehicle, plans travel routes and coordinates vehicles so that they do not interfere with one another, plays the central role. The RCS uses various scheduling algorithms to allocate tasks optimally, and through multi-robot path planning and traffic management it enables robots to cooperate efficiently without interfering with one another. At sites where multiple long vehicles such as tuggers are running, traffic management — priority control at intersections, passing control in aisles and congestion avoidance — is especially important, and because the RCS supervises all of this centrally, transport efficiency can be maintained even as the number of vehicles increases. The RCS also supports transport between different scenes such as warehouses and production lines, controlling transport across the entire site in an integrated manner.
Integration with WMS, MES and ERP
To maximize the effect of transport automation, it is effective to link the AGV control system with host business systems such as the inventory management system (WMS), the manufacturing execution system (MES) and the core enterprise system (ERP). For example, if the RCS automatically generates transport tasks based on receiving and shipping instructions from the WMS or production instructions from the MES, logistics that deliver “the required goods, at the required time, to the required place” can be realized without human intervention. Seamlessly linking the control system with the WMS enables digital management of inventory information to work in concert with transport, achieving highly accurate plant operation in which the movement of goods and the movement of information are aligned. Drawing on our track record in deploying production management systems, TOMAS TECH provides end-to-end support for the integration that connects AGVs with host systems.
Deployment process and timeline
Deploying a tugger AGV is not complete simply by purchasing and installing vehicles; it requires progressing step by step through a series of stages, from analysis of the current situation to requirements definition, design, build and testing, deployment support and go-live. Here we introduce the flow of the deployment process that TOMAS TECH provides as standard.
1. Analysis of the current situation
First, we conduct interviews about current operations and the systems in use, confirm the requirements, and then analyze the customer’s current situation. We carefully understand the type, volume and frequency of the goods being transported, the transport routes and distances, the site layout and floor condition, and the relationship with existing equipment, and we clarify the issues that automation should resolve. Based on the results of this analysis, we set the direction for the optimal transport method and guidance method and prepare a quotation.
2. Requirements definition
Based on the results of the current-situation analysis, we carry out detailed requirements definition. So that the system can be realized in a form consistent with actual operation, we confirm detailed requirements such as the content of transport tasks, the number of vehicles, the cart configuration, stop positions, the scope of integration with host systems, and safety requirements. Making the operational scenarios concrete at this stage is extremely important for preventing rework in later stages.
3. Design
While holding progress meetings, we proceed with basic design, detailed design and migration preparation based on the requirements. From both the hardware and the software side — travel route design, design of towed carts and fixtures, design of the guidance infrastructure, and design of the RCS and host system integration — we build a form that fits the business.
4. Build and testing
We build the equipment and systems according to the design and then move into testing. We verify operation in line with actual transport scenarios and confirm travel stability, stopping accuracy, integration with host systems, and safety functions. For a smooth deployment, we also consider the method of migrating from existing operations.
5. Deployment support
While running in parallel with the systems and operations currently in use, we hold operator training sessions for the deployment, have the staff on site confirm how the system feels to use, and then ask you to carry out final acceptance inspection. We provide careful support so that the site can transition to the new way of working without strain.
6. Go-live
At last, operation begins. Even after go-live, we provide long-term support for safe and comfortable system operation through operational maintenance support, a help desk, information provision and the supply of revised versions. During the ramp-up period after deployment, we fine-tune transport timing and routes while reviewing actual operating data, guiding the system towards stable operation. Please note that the overall project duration varies depending on the scale, the requirements and the extent of customization. In general, a corresponding amount of time is required from the point at which requirements are fixed until go-live, so planning with sufficient margin is important. Specific timelines are presented individually after the current-situation analysis.
Checkpoints to confirm before deployment
To make in-plant logistics automation a success, it is important to identify the specification that suits your own plant or warehouse. First, confirm the process and work content you wish to automate, and decide the transport method that suits the goods being moved. Then decide the travel (guidance) method from the perspectives of the site environment, the goods to be transported, how frequently routes change, and cost. At the same time, it is necessary to recognize that a certain number of processes are difficult to automate. Here we organize the site-side checkpoints that should be confirmed in advance when considering the deployment of a tugger AGV.
Floor condition
Because AGVs travel on the floor, the flatness of the floor is a precondition for stable travel. Large unevenness, steps, grooves or gradients in the floor affect travel stability and stopping accuracy. In general, the travel surface for an AGV is required to be clean, free of particles and dirt, and not slippery. Permissible values for steps, grooves and gradients are defined for each model, and stricter conditions apply particularly at points where the vehicle must stop with precise positioning. With the tugger type, which tows a long train of carts loaded with heavy items, the floor condition has an even greater influence on travel behavior, so a prior floor survey is especially important. Where necessary, floor repair or refurbishment is incorporated into the deployment plan.
Aisle width and curve radius
Because the tugger type is long overall, securing the aisle width and curve radius required for travel is an important design point. On curves, a difference in turning radius arises between the tractor and each cart, so more turning space is needed than during straight-line travel. The more carts are coupled and the longer the carts are, the greater this effect becomes. For intersections, corners and locations where the vehicle passes other vehicles or workers, we confirm in advance whether sufficient width can be secured with a margin. If the aisle width is insufficient with the existing layout, measures such as reviewing the layout or adjusting the number of coupled carts are considered.
Communication environment
In operations where multiple AGVs are supervised by an RCS, the quality of the wireless network (Wi-Fi) connecting the vehicles to the host system determines the stability of operation. Sufficient signal strength and stable communication must be secured across every area in which the AGVs travel. In general, the areas where AGVs operate are required to have signal strength above a certain level, low communication latency, and a stable, assured communication speed. The placement of wireless access points should be planned taking into account signal attenuation caused by obstacles such as walls, so that coverage from adjacent access points overlaps appropriately. Considering an uninterruptible power supply (UPS) and redundant equipment configurations so that communication is not lost during a power failure is also an effective measure for stable operation. Before deployment, we measure the radio environment on site and, where necessary, upgrade the network environment.
Charging and operating plan
Because AGVs run on batteries, the charging plan is also an important element of operational design. The installation location and power capacity for charging stations must be secured, and the cycle of operation and charging must be planned so that it does not disrupt transport work. At sites with high transport volumes that require continuous operation, incorporating automatic charging — whereby the vehicle heads for charging automatically once the battery level falls below a certain threshold and returns to work once sufficiently charged — makes it possible to maintain a high utilization rate. Since charging stations require a corresponding power capacity, preparations on the electrical equipment side should also be confirmed.
Safety measures
In environments where people and AGVs coexist, safety measures are the top priority. AGVs are equipped with a mechanizm that stops the vehicle when a person or obstacle is detected on the travel route, but because the tugger type is long overall, safety design must take into account the behavior of the whole train including the carts at the rear. Multi-layered safety measures are put in place, including stopping via obstacle detection sensors, alerting people nearby with warning lights and buzzers, deceleration and temporary stops at intersections, and emergency stop functions. Stopping accuracy — reliably stopping at the designated position — is especially important when the vehicle is interlocked with other equipment or robots. We also establish operating rules and provide briefings and training for site workers, building an environment in which people and robots can coexist safely.
Maintenance and support structure
A tugger AGV does not deliver its return on investment simply by being deployed; it does so only by continuing to run stably over the long term. That requires a maintenance and support structure after deployment. At TOMAS TECH, we provide continuous support for our customers’ system operation from both the software maintenance and the hardware maintenance sides.
Operational support and recovery assistance
We set up a support desk and provide operational support by telephone and e-mail, as well as recovery assistance in the event of software failures. By putting in place a structure that can respond quickly to the questions and troubles that arise in day-to-day operation, we provide an environment in which the site can continue to use the system with confidence. We also respond to consultations on operational improvements based on observed operating conditions.
Version upgrades and long-term operation
When functional improvements are made to the software, we provide upgraded versions. By supplying software that supports the latest environments, the system does not become obsolete and stable operation can be continued over the long term. We also give consideration to reducing our customers’ lifecycle costs — for example, by eliminating the need to purchase software again when servers are replaced.
Hardware maintenance and re-setup
In the event of hardware failures such as server faults, our company or the hardware manufacturer carries out on-site repair including parts replacement. In addition, if software re-setup is required after the fault has been repaired, we perform the restoration work. For components such as the vehicles themselves, the carts, the guidance infrastructure and the charging equipment, we also prevent downtime caused by failures through regular inspection and preventive maintenance. Precisely because transport is the foundation that keeps production from stopping, a well-developed maintenance structure underpins the reliability of the entire system.
Frequently asked questions (FAQ)
Q1. How many carts can a tugger AGV couple?
The number of carts that can be coupled is determined by the tractor’s driving and braking force, the curve radius of the travel route, the gradient of the floor, the weight of the goods loaded, and the braking distance required to stop safely. In general, the more carts are towed, the greater the volume that can be moved at once; however, the increase in overall length also makes the requirements for turning space and safety more demanding. The number of coupled carts is therefore optimized individually, balancing “the volume you want to move” against “the physical constraints and safety requirements of the site”. We will first ask about the conditions at your site and then propose an appropriate formation.
Q2. Can we use our existing carts as they are?
There are cases in which existing carts can be used, but in many cases modifications such as adding a coupling mechanizm or revising the wheel configuration are needed in order to support automatic coupling and stable towed travel. After confirming the structure and strength of the existing carts and the arrangement of their wheels, we judge whether they can be used as they are, whether modification is required, or whether it would be better to design new carts. We propose the optimal approach with a view to making the most of the site’s existing assets wherever possible.
Q3. How should we choose between the tugger type, the low-profile type and the forklift type?
The transport method is selected based on the automation requirements you want to achieve, the process, the work content and the goods being moved. The tugger type suits moving a large volume of goods together over long distances along specific routes; the low-profile type suits fine-grained transport of small quantities to many destinations; and the forklift type suits cases where vertical transport is required, such as storing pallets in racks. At many sites, rather than choosing exclusively among these, the optimal method is combined process by process to optimize the whole. Through analysis of the current situation, we propose the combination of methods that best suits your site.
Q4. Can it be deployed at a site with frequent layout changes?
Yes, it can. What matters is selecting an appropriate guidance method according to how frequently the layout changes. If changes are frequent, the SLAM method — which requires nothing to be laid on the floor and allows routes to be changed in software — or the relatively flexible landmark method is suitable. In addition, because the tugger type can flexibly adjust its transport capacity by increasing or decreasing the number of carts and reviewing the coupling configuration, it is a method that adapts readily to sites with frequent changes in product type and production volume. Designing with future changes in mind allows the investment to be used effectively over the long term.
Q5. How long does deployment take?
The deployment period varies depending on the scale of the project, the complexity of the transport requirements, the extent of customization, and whether site infrastructure work is required. Because the process advances step by step through current-situation analysis, requirements definition, design, build and testing, deployment support and go-live, a corresponding amount of time is required from the point at which requirements are fixed until go-live. Planning with sufficient margin is the key to success. Specific timelines will be presented individually, in line with your situation, after the current-situation analysis.
Q6. Is it safe for people and AGVs to work in the same space?
AGVs are equipped with a safety function that stops the vehicle when a person or obstacle is detected on the travel route, and multi-layered safety measures are put in place, including alerts via warning lights and buzzers, deceleration at intersections, and emergency stop functions. Because the tugger type is long overall, safety design takes into account the behavior of the whole train including the carts at the rear. In parallel, by establishing operating rules and providing briefings and training for site workers, we build an environment in which people and robots can coexist safely. Safety is treated as the top priority in deployment design, and measures are taken in line with the conditions of each site.
Q7. Can all transport be automated?
Not every process can be automated, and it is necessary to recognize that a certain number of processes are difficult to automate. Processes in which the load form is irregular, or in which there are many exceptions requiring judgement, can become less efficient if they are forced into automation. What matters is identifying the processes where automation delivers the greatest effect and concentrating investment there. By dividing roles so that AGVs handle routine, high-volume transport while people handle work that requires judgement and adjustment, productivity across the whole site is maximized. Through analysis of the current situation, we identify the processes suited to automation and present our proposal.
Summary — making high-volume transport more efficient with tugger AGVs
The tugger AGV (cart towing) is a transport method that tows multiple trailers or carts to move large volumes of goods efficiently, and it is widely used in plants handling heavy items such as automotive parts and machine parts. Its greatest strengths are that carrying multiple loads at once dramatically improves work efficiency, that flexible layout changes and cart additions are possible, and that it is well suited to long-distance transport and specialized for use in large facilities. Across a wide range of situations — inter-process transport, parts supply to production lines, milk-run circuit transport and coordination with receiving and shipping areas — the tugger type delivers high efficiency by “moving things together”.
To make deployment a success, it is important to proceed carefully along a staged process: selecting the appropriate transport and guidance methods, working out the design of the towed carts and fixtures, integrating with the RCS and host systems, and confirming site-side conditions such as the floor, aisle width, curve radius, communications, charging and safety. Drawing on the knowledge gained from supporting shop-floor improvement for manufacturing and logistics customers from our base in Thailand, TOMAS TECH provides end-to-end support for transport automation with tugger AGVs — from current-situation analysis and requirements definition through design and deployment to long-term maintenance support. If you are struggling to make transport work more efficient or to reduce the labor it requires, please do get in touch with us. We will propose the optimal solution for the challenges at your site.
For inquiries and consultations regarding the deployment of tugger AGVs or the automation of in-plant logistics, please use the contact form below. We look forward to hearing from you. https://tomastc.com/en/contact/
