AGV Navigation: Methods, Comparison, Pros and Cons - Illustrated Guide (2023)

What is the best navigation system for an AGV?Laser, natural, or magnetic?None.It depends on your project and your needs.

What are the main AGV and AMR Robots navigation systems?In this article I explain how do AGV and AMR Robots navigate, and the advantages and disadvantages of each navigation method.

Types of AGV Navigation Systems

Regardless the typeof automated guided vehicle(forklift, tow tractor, cart, etc), theself-driving robotrequires an Automated Guidance System that drives the AGV and informs the AGV Management System about therobot positioning.

Navigation systems are improving day after day and are contributing toboost the AGV Market worldwidewhich is incredibly growing atCAGR of12.45% from 2021 to 2030.

This outstanding development is also possible thanks to accurate, reliable and cost-effectiveagv navigation sensorsand software.Depending on the application, AGVs and AMRs navigate thanks to 2D or 3D LiDAR, magnetic sensors, ultrasonic sensors, cameras, etc.

What are the most popular AGV Navigation Methods?

The main AGV NavigationTechnologies are Laser Guided Navigation, Magnetic Navigation, Magnetic spot navigation, inductive wire navigation, optical navigation, optic navigation. If we talk about Autonomous Mobile Robots, they use to navigate thanks to Natural Feature or Free navigation, including SLAM Navigation with LiDAR Sensors or camera based visual navigation systems.

As you can see, there are severalNavigation Methods for Automated Guided Vehicles and Autonomous Mobile Robots.

This Kollmorgen'sone-minute video provides a concise summary of various technologies. However, I recommend reading further to gain a better knowledge of the available possibilities.

Let's have a first pros and cons summary of each technology that I'll explain into detail in the following lines.

Summary: Advantages and disadvantages of mobile robots navigation systems? -AGV NavigationmethodsPros and Cons

Choosing the rightdriverless guidance technology is essential because it will influence the overall performance of theAutomated Guided Vehicle System.

Choose the technique of navigation that best matches your needs rather than the most cutting-edge technology available.I have seen several initiatives fail due of a bad navigation choice.

What do you need?

Accuracy?

Reliability?

Flexibility?

Low cost solution?

This table summarizes the benefits and drawbacks of each self-driving navigation technology.

Navigation Tech	Advantages	Disadvantages
	Easy to install. No invasive installation. Accurate positioning. High speed No costs due installation maintenance	Modifications require supplier intervention AGVs with this technology are expensive
	Easy to install. Easy to modify No invasive installation Accurate positioning. Reliable navigation AGVs with this technology are less expensive	Magnetic tape maintenance. Magnetic tape cost Not suitable for complex paths
	Easy to install Flexibility: Easy to add new paths or modify existing ones Low cost of installation No invasive installation. No costs due to implementation maintenance	Lower reliability in chaotic and variable environments Highly effective and efficientfree navigation is still very expensive. Lower positioning accuracy compared with other navigation methods
	Free environment Accurate positioning. No costs due to implementation maintenance	Installation is easy but it still is more complex than magnetic tape Magnetic tape installation is faster and easier to modify

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In my opinion, there is not a "best" navigation system. It depends on your specific requirements.

So let's discover out how does an Automated Guided Vehicle navigate!

How do Automated Guided Vehicles Navigate?

Laser Guided Navigation (LGV).

A LGV or Laser Guided Vehicleis an AGV that utilizes a laser positioning technology for navigation. Laser Navigation is one of the most popular navigation systems widely used in automated forklifts due to its realiability and accuracy.

What is the difference between AGV and LGV?

There is no difference because a LGV is an AGV with Laser Navigation. Thus, LGVs are a specific type of AGV.

What Types of AGV perform Laser Guided Navigation?

Laser navigation is widely used byAutomatic Forklift trucks,used in warehouse and stocking applications thanks to its tight accuracy and reliability.

How does Laser Guided AGV work?

Each Laser Guided Vehicle is equipped with a Navigation Laser (simply called a Navigation Device) positioned on top of a pole that interacts with targets positioned in the AGV working area.

LGV vehicle by Wellwit Robotics. Click here to discover more

The Navigation Device sends rotating laser arraysin a360 degree pattern.

These arraysreach several reflector targets (tapes or cylinders).

Reflectors send the laser array signal back to the AGV Laser Navigation Device.

LGVs mustacquireat least three of these array feedbacks to allow positioning calculation (triangulation) thanks tovery complex algorithms.

Depending on the AGV manufacturer, LGVs calculate and correct their positioning between 30 and 40 times per second. These devices are incredibly accurate.

Flat and cylindrical reflectors. Which one is better? Discover more here.

When is it useful to choose a Vehicle with Laser-Guided Navigation?

Quick conclusion: When you need a fast vehicle with tight stop tolerance and you have multiple destinations and tracks.

Laser-Guided Navigation is easy to install. The AGV supplier will install all the reflectors and simulate the AGV path on the AGV Management System to define your needed AGV routes.

Everything is “virtual” and there are no fixed infrastructures such tapes on the floor or wire beneath the surface. In the same corridor, you can have as many virtual routes as you wish.

So, if your project requires avery big and complex route system,it would be efficient and effective to haveLaser-Navigation Vehicles.

What are some advantages to LGVs?

✅LGV technology is easy to deploy.Installation is relatively fast. A big part of the job is done in an office by the supplier engineers.

✅No intrusive installation. LGVs only require placing reflectors around the facility. These reflectors are easy to place, they can be adeshive tapes or just two bolts fixing. They are places at around 8 ft (2,5 m) height so once installed they will not interfere with the operations of the premises.

✅Accurate tolerance positioning.Positioning algorithms are very sophisticated allowing a position accuracy close to ± 0,2’’ (5 mm). Laser Guided technology is the main option for stacking or racking operations in high warehouses.

✅The vehicles performing laser navigation (so LGVs) are veryefficient achieving up to 2 m/sec (6,5 ft/sec).

✅No costs due to installation maintenance. The reflectors needed for navigating are passive, they do suffer wear and unless you do not break them they will not have any problem. It is only necessary to keep them clean and verify that they have not move for some reason.

What are some disadvantages of Laser Guided Navigation?

❌The AGV paths are easy to modify… but only by the supplier engineers. Any time you wish to update a path, to add new missions, to modify picking and droppingpositions... you have to call your supplier.

❌LGV Vehiclestend to be expensive. The vehicles including this technology have complex board controls and efficient navigation devices that make the average price of LGVs quite expensive.

❌Due to the fact that a vehicle's laser is typically situated on top to maximize the number of wall-based targets it can 'see', laser triangulation is not suitable for undercart or platform robots.

Magnetic Tape Navigation AGVs

In this case, automated guided vehicles are equipped with magnetic sensors and follow a defined track made by a magnetic tape track.

Watch the following video to understand how do magnetic guided vehicles work:

The guided route is made by a magnetic tape that is placed on the floor surface.

The AGV magnetic sensor detects the magnetic field from the tape and drives the AGV following the path.

Magnetic Tapeis easy to install. High-bond adhesive is used for laying the magnetic tracks. Standard dimensions are 1 mm thick and 5 cm wide, so the tape isn’t invasive at all.

The AGV management system can indicate to the AGVS how and where to drive using tags (rfids) or magnetic indicators placed on the floor.

At these predetermined positions, the AGV can decide what to do: turn left, stop, engage a trolley, etc.

When is useful to choose an Automated Vehicle with Magnetic Navigation?

Magnetic navigation is primary preferred for Automatic Guided Carts (AGC). Magnetic Navigation accurary allows low-profile AGVS to engage trolleys from below.

Something like this:

Image from SEAT Martorell (Spain)

Magnetic Navigation is mainly suited for well-defined routes without lots of routing options.

What are some advantages to Magnetic Tape Navigation?

✅Easy to install:Installation is easy, it doesn't require any high skill professionals. Low cost workforce. I know that AMR suppliers and Natural Navigation technology suppliers state that installing magnetic tape is time consuming... well, I have installed hundreds of magentic AGVs and you can install more than 500 m in just one shift.

✅Easy to modify:The end user can modify routes simply by placing or removing the adhesive magnetic tape from the floor.

✅No invasive installation:The installation of the magnetic tape doesn’t require any infrastructure changes or modification either before or after the placement of the tape. Magnetic tape can be installed without stopping customer operations.

✅AGVs havehighly accurate positioning:Positioning tolerance is very precise allowing accuracy close to ± 2 mm (0.07 inch).

✅Reliable navigation:Strong and reliable navigation that does not suffer from dust, noise, or dirtiness. It does not depend on the surrounding environment.

✅Well-established technology : AGVs with this navigation technology are less expensive and highly effective.

What are some disadvantages to Magnetic Tape Navigation?

❌Magnetic tape maintenance: Magnetic tape, paint, and tags/codes are all susceptible to deterioration over time, which can lead to "broken" routes and vehicle faults. It could be necessary to embed the tape on the floor or cover it with an epoxy resin or dedicated protective tapes that would increase the installation cost.

❌Magnetic tape cost:For big installations with alongtracks , magnetic tape costs will increase installation costs.

❌Installinglong tracks and and crosses on the flooris time consuming (so expensive) andcomplicates AGV traffic management.

NaturalNavigation AGV - Free Navigation

There are several technologies included in what’s called “Natural Navigation”.

The most importanttechnology is the SLAM Navigation, or Simultaneous Localization and Mapping (SLAM).It means that an AGV with SLAM Navigation is able to map its environment and localize where it is thanks to the information received from the surrounding environment.

The AGVs are able to map the environment with different agv sensors such vision cameras, lidar sensors or even with the same lasers used for safety purposes.... all of this info is combined with internal inertial measurement unit (IMU) to define and recalculate the real AGV positioning.

All of these calculations are made by a highly complex algorithm called SLAM... So, SLAM is more of a concept than a real technology.

How do AGVs with SLAM Navigation work?

Let’s make it simple, mobile robots performing natural navigation (also known as contour based navigation) are called Autonomous Mobile Robots (AMRs).

Thanks to the Natural Navigation, AMRmaps the area and is able to move and orient itself just by "viewing" the environment without needing tapes or reflector, just "watching" the environment.

Aditionally AMRs are capable of redefining routes and avoiding obstructions. An AMR does not require specific pathways to be predefined. It can alter its course on the fly.

If an obstruction is detected, the AMR modifies its course to avoid it.

When is it useful to choose AGVs withnatural navigation?

SLAM Natural Navigationis improving and will substitutefor other kinds of navigation such magnetic navigation, optical navigation ,etc.

It’s a good solution for Automated Pallet Jacks,AGCs and Tugger AGVs. Many of the mainTop AGV Manufacturers are developing and including this technology on their AGVs.

The main concernabout Natural (SLAM, LIDAR, etc) technology is its reliability in variable environments such as production lines where there’s continuously moving of people, items, boxes, pallets, etc.

In these conditions the AGV might not be able toLOCALIZEwhere it is.

For this reason,SLAM with LiDAR is a great solution for AGVswhere you have well defined profiles and environments with fixed structures such as walls and columns.

Natural Navigation is typically used for warehouse robots and hospital robots… in general, in any environment with a low or limited level of “confusion”.

This said, it is important to understand that natural navigation systems are improving and are able to work in more and more complex environments.

If you wisht to have more in-depth technical details about SLAM technology and Natural Navigation AGVs,check out this article:Natural Navigation Automated Guided Vehicleswith more details infor mation about the natural navigation topic.

What are the benefits ofNatural FeatureNavigation?

✅It’s the future:More and more companies are investing, developing and improving Natural Navigation Technology.

✅Easy to install: Just draw a line in your pc or drive your robot to teach the track. It will map and localize it by itself and it will do the rest of the job.

✅Easy to modify.Same as the installation, just add, remove, modify the tracks or destinations effortless.

✅Low installation costs. Installation is fast and easy.

✅No invasive installation.Natural Navigation AGVs do not require any kind of external infrastructure that could interfere with plant operations.

✅No costs due toimplementation maintenance. There is nothing installed for the navigation, so there is nothing to maintain.

What are thedrawbacksofNatural FeatureNavigation?

❌Navigation Reliability.Autonomous Mobile Robots with Natural Navigation could have “orientating” problems in industrial and/or confusing areas due to the variable environment. In other words, if the environment is too chaotic, the robot could not find itself.

❌Vehicles with good and reliable natural navigationare still more expensiveif compared to other technologies.

❌Lower positioning accuracy compared with other navigation methods.

Magnetic SpotsNavigation

What is AGV magnetic spot navigation?

AGVs can navigate following small cylindrical magnetic spots embedded on the floor. Magnetic spots are commonly cylindrical magnets with dimensions close 20x10 mm (0,8x04 inch).

Magnetic spots and AGV sensor. Image from AMERDEN AGVs

Magnetic spots are installed every 250-500 mm (near 15 feet) creating a virtual path.

The AGVs goes from one spot to the next using sensors and controls such hall-effect sensors, encoders, counters, gyro sensor and other kinds of encoders to calibrate against steering angle errors.

Image from AMERDEN AGVs

AGVs follow a CAD drawing previously loaded on the AGV Management System while the magnetic spots provide a reference in accordance with the map.

Positioning tolerances are relatively good achieving near 2,5 mm (1’’). This tolerance is better than tolerances obtained by other “free” navigation systems such SLAM, LiDAR, etc.

Installation is quite easy. A small hole on floor is required where the magnet is positioned. After that installation, hole is covered by epoxy resin.

What are the pros ofMagnetic Spots Navigation?

✅Once installed, therearen't any structures on the floor.It seems to be “free.”

✅Accurate positioning.Positioning algorithms are very sophisticated, allowing an accuracy position close to ± 2,5 mm (0.1 inch).

✅ No maintenance costs.Once installed, there is no need for any kind of maintenance because there is no path wear.

What are the consofMagnetic SpotsNavigation?

❌Installation is not so complicated but it still is more complex than magnetic tape.

❌Installation is quite invasivebeacuse it is necessary to make holes. There will be noise and dust,

❌It iscomplicated to modify paths, add new destinations, etc.

AGV Robots Navigation Benchmark Comparison

The following table ranks different AGV Navigation technology based on different variables:

Installation complexity:Is it easy to install? Is this technology intrusive? Does it require civil works? Is it necessary to stop user operations while installing the mobile robots?

Flexibility:Is it easy to modify the mobile robot paths? Can the user add new picking or dropping positions? Is it easy to add new destinations or routes?

Installation cost:Is the installation phase expensive?

Vehicle cost:How does navigation technology influence AGVs or AMRs vehicle cost?

Reliability:Is this navigation reliable? Does the vehicle lose the track?

Accuracy:What is stopping tolerance? Is this technology accurate?

Installation Maintenance:Once the system is intalled. Is it necessary to maintain the hardeware needed to navigate? Does wear or dust influence navigation performance?