Need an AGV Tugger? All the Types/Specs/Prices. The right selection
Automated tugger trains or towing AGVs are easy to install reducing non-value added costs thanks to their exceptional transport capacity.
Self-driving tow tractors or Autonomous Mobile Towing Robots (if they are AMRs) are a great option to make a step further in your intralogistics optimization.
Be careful! Even tough a tugger AGV has many advantages, there are several drawbacks to be understood.
What is an Autonomous Tugger train? Featuring the Tug Robot
A Tugger AGV or AMR is a type of self-driving locomotive designed to tow carts. Basically, it is a robotic tow tractor.
This is an AGV tugger train
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Table of Contents
What are agv tugger trains navigation methods? What kind of batteries mount towing agvs? What is main tuger agv application? Tugger Automated Guided Vehicles Advantages |
Types of Towing AGVs
There is not any official classification for these robots. We could distinguish them based on their towing capacity.
- Tugger AGVs up to 1,5-2 Ton capacity (3.300-4.400 lbs) are compact and can be only used in autonomous operation mode.
- AGVs from 2 Ton to 5 Ton capacity (4.400-11.000 lbs) can be designed in two different ways.
In the first case, we have a manual vehicle that has been modified to become an AGV. This kind of vehicle has is able to be operated manually or autonomously. They are powerful and fast but are more expensive.
The second option is to have an AGV designed to be used only in autonomous mode
In the following link you can learn more about agv tugger prices: How much does AGV cost?
- AGVs able to tow more than 5 Ton and up to 20 Ton (11.000-40.000 lbs) are typically produced from bigger tow tractors. These tractors can also be used in outdoor applications.
This kind of towing mobile robot trucks are widely used as Outdoor Automated Guided Vehicles.
Tugger AGVs Technical Specifications
What is maximum load capacity of a tugger AGV?
Tugger AGVs typically have around 1,5 ton capacity (near 3.300 lbs). This capacity covers 85% of the Tugger AGVs' applications.
Nevertheless, there are AGVs covering towing needs up to 20 ton (44.000 lbs).
What is maximum Tugger AGV speed?
In standard Tugger AGVs' with magnetic navigation the maximum speed is around 60 m/min (195 ft/min – 1570 inch/min).
Towing AGVs based on manual tow tractors with Natural or Laser Navigation can drive up to 240 m/min (12 km/h - 780 ft/min).
Take into consideration that vehicle speed, vehicle weight, floor surface, and the load weight will determine the time needed to stop an AGV before it makes contact with an obstacle. It is very important that the vehicle speed and the safety laser are combined to avoid any kind of contact with obstacles on the way.
Safety is tricky business... do not miss this article about AGV safety rules.
How do Robotic tow tractors navigate?
Before going ahead, if you wish to know more about navigation methods, do not forget to read this article: AGV Guidance Systems
Tugger Robots could adopt different navigation methods:
Magnetic Navigation
The magnetic navigation (tape or spots) is widely used for tuggers, specially for low cost tractors.
The AGV Tugger trains must drive only forward, so they do not have to perform complex maneuvers and sometimes circuits are just loops.
Magnetic navigation is reliable and easy to install and modify, but it could be costly if circuits are very long. On the other hand, magnetic navigation is simple and its implementation in AGVs is not expensive, so vehicles with magnetic navigation are cheaper.
Laser Navigation (LGV) tugger
LGV Navigation is a good solution for Tugger trains. The AGV chassis allows the placing of a high mast where it is possible to install a navigation sensor.
Laser navigation is not invasive because it only requires some reflectors in the working area for position triangulation.
It is worth it to have laser navigation if circuits are long and/or complex. The cost of the vehicle will increase but you will save the magnetic tape and time for installatin.
Free Navigation
Free or Natural AGV Navigation means no need for rigid infrastructure such as wires, tape, or laser reflectors. The robot maps the environment and navigates using this environment as a reference.
Under this category we can find several technologies such as vision guided (VGVs), SLAM, LiDAR, etc.
Robotic tow tractors with natural navigation are Autonomous Mobile Robots, so they can be called Autonomous Tractors.
Autonomous Tractors perform Natural Navigation using the Safety Laser Scanners or other types of scanners such as Lidar Scanners positioned on a mast. If the Scanner is positioned on a mast, it avoids environmental “noise” that could cause navigation problems
What kind of batteries use AGV tugger trains?
There is no one single answer. The type of battery depends on the whole project rather than the vehicle itself. The project performance and feasibility will determine the recharging strategy and consequently will define the battery type.
Battery management is a complex matter, this article explains what are the different types of batteries for automated vehicles.
For what regards the Tugger Robots, the most common battery type is a sealed GEL battery with no emissions and no maintenance. Small Tuggers are 24V and big ones use 48V.
AGV Tugger trains can also perform agv opportunity charging. In this case it is advisable to have a battery that is able to support short and intensive battery recharging, for example with Pure-Lead batteries or lithium batteries.
Battery manufacturers offer good quality lithium batteries for big vehicles such as forklifts or tow tractors uggers based on manual tractors.
It is necessary to analyse the project in order to identify what is the best and most convenient type of battery.
What are Robotic Tow Tractors used for?
The main application of robotic tractors is the supply of components to assembly/production lines and finished good removal from the end of the line.
Tugger AGVs or AMRs trains count on a huge transport capacity compared to Under Ride Robots or Forklift AGVs.
Each Robotic Towing convoy can be composed by three, four, five, or more trolleys.
Robotic Tow Tractor drawbacks
Even tough the transport capacity is very high, there are some drawbacks to be taken into consideration.
Tugger AGVs cannot hook trolleys autonomously
Well, let’s say that they cannot hook or at least it’s very complicated to hook them. In order to hook trolleys autonomously, the robot must perform very complicated maneuvers and it is mandatory that the trolley drawbar is always in the right hooking position.
It is easier to perform autonomous hooking with laser or natural navigation than with magnetic navigation.
Moreover, the Safety Laser Scanner is positioned on the front side of the vehicle, so while performing the backward movement for hooking, there would be no safety sensor activated.
There are two options to solve the safety problem:
Very slow movement (see speed safety regulation in this link: Understanding AGV Safety Systems)
Bumper or Safety Laser on the back (what would increase vehicle price).
Complex hooking-unhooking operation in the production line
Tugger robots substitute manual tow tractors.
The problem is that with manual tow tractors, the driver performs the hooking/unhooking operations. If you install a Tugger AGV there is no driver (as you are aware), so these operations must be done by the assembly line worker. In many cases, the assembly line worker has no time at all to hook and unhook trolleys.
Check this situation:
We have a Tugger AGV with 2 trolleys with parts for working stations. The AGV goes to the first working station, stops, and waits the operator to exchange the full for the empty.
Once the exchange in position 1 is done, the AGV continues with its mission and goes to position 2. In this case, the operator in position 2 is obliged to:
- Unhook the empty trolley from position 1 from the full trolley from position 2
- Unhook the full trolley from position 1 from the AGV
- Perform the empty vs full
- Hook the empty trolley from position 2 to the AGV
- Hook the empty trolley from position 1 to the empty trolley from position 2 (new convoy with empties)
Imagine what would happen if there were four or five trolleys.
Safety concerns regarding Tugger AGVs
Automated Tow Tractors are more dangerous than other types of driverless robots such as Forklifts or AGCs.
An automated train is composed of several trolleys that are continuously hooked and unhooked. These trolleys are independent of the locomotive, so there is no electrical connection between them and there is no common safety system.
The safety laser is positioned on the front side of the AGV. If the safety laser detects some obstacle, the safety system immediately stops the vehicle: GREAT!
But what happens between two trolleys? There is no safety system at all. If someone gets between two trolleys while the robot is running… it hurts.
If someone is stuck between two trolleys, he can shout as much as he can, but the robot will not listen at all and will keep on running.
There are some solutions:
- We could include a safety dynamometer in the locomotive towing hook so in case there’s an abnormal tension the vehicle stops. My experience is that these systems do not work very well because locomotives are continuously stopping and starting. Forces while restarting are high, and we risk that the AGV is always in safety mode because it requires some extra effort to restart after a stop.
- We could connect all trolleys to the robot and create a unique safety circuit. We could install bumpers in the trolleys or stop buttons that would stop the locomotive if needed. It would be great, but it is very expensive, and it would be very annoying connecting and disconnecting all the safety joints whenever we must change a trolley.
At the end of the day, risk remains. It is necessary to provide adequate training to operators and identify self-driving robot running areas as “Risky Areas” in your safety assessment.
What are the Automated Tow Tractor advantages?
- Fast;
- Easy to install;
- Easy to adopt because they substitute manned tow tractors, and;
- Able to transport several unit loads in one single mission, so, high transport capacity.
What are the Towing AGV disadvantages?
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Need manual operation for hooking.
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Risky compared with other types of moile robots.
Tugger AGVs Manufacturers
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