Outdoor AGV - Rain? Fog? Who cares?

When is it suitable to deploy a mobile robot (AGV or AMR) system? Self-driving robotic systems are best deployed when they perform low value-added tasks. Outdoor transportation sometimes requires long distances needing extended periods of time for performing missions.

AGV Robots or Autonomous Mobile Robots  are a great option for outdoor applications but they must overcome specific challenges such weather conditions, floor wear or manned vehicles traffic.

Outdoor autonomous robots WANTED ⚠ .  

My name is Alfredo Pastor, I have installed many outdoor agvs. Outdoor mobile robots are becoming more popular as technology makes them more efficient and reliable. I'm here to explain you my experience with them. 

 

Can Outdoor AGV Systems work?

Of course, yes they can. An Outdoor Autonomous Mobile Robot System must drive safely and independently considering all types of weather conditions.

  

It seems obvious, but it isn’t. In fact, not all the outdoor projects are feasible or worthy. 

  

The WEATHER is clearly the biggest problem that the outdoor automated guided vehicle has to deal with.

         

  

    

These are the key elements to consider that I'll discuss in this article:

    

✅ Types of outdoor robots and their applications.

✅How do they "Drive"?:  What are the best navigation technologies for outdoor applications?

✅ Are them Safe?: Regardless the type of navigation or vehicle, the outdoor agv system must avoid running into things or people.

 

 

Table of Contents    Types of Outdoor driverless mobile robots Safety of outdoor autonomous robots Outdoor mobile robots Navigation Magnetic Tape Navigation SLAM and LiDAR Navigation GPS Navigation Combination of different types of navigation Mobile Robot Management System for outdoor operations

Before keep on reading, I suggest to watch agvnetwork's FREE recorded webinar about outdoor agvs/amrs.

   

Do not miss the webinar because it provides additional info to this article. For example: Prices and Manufacturers for each type of vehicle.       

    

 

     

Click here to watch the webinar

   

Let's go ahead. 

  

Types of Outdoor agv systems

       

There are four main types of mobile robots for outdoor applications: forklifts, tugger tractors, platforms and service robots (security robots, las-mile delivery, etc). 

     

Automated Outdoor Forklifts

       

There aren’t many suppliers right now, but there are some outdoor automatic forklifts  working out there.

 

In fact, there isn't reason why an automated forklift should not work outdoor. Of course, in most of cases the outdoor forklift should be modified with special IP Protection and rubber wheels. 

 

For example, in the following video you can see some different types of forklifts (reach truck, stacker, etc) working in outdoor conditions. 

     

 

Click here to learn more about SMARLOGY 

     

Autonomous Tow Tractors

       

There are several suppliers converting manual tow tractors into driverless tow tractors.

    

 

     

A manual Tow Tractor able to work in outdoor conditions could also be able to work in Automatic mode.

    

Tow tractors are already equipped for outdoor conditions  with rubber wheels and cabins where electronic cabinets can be installed. Moreover, tow tractors are widely used to transport convoys up to 44.000 lbs (near 20 Ton).

      

Unit Load Robots or Platforms

     

There are several Unit Load mobile robots in Outdoor applications already existing. In general, these vehicles are “custom made” and transport material with roll conveyors or other transfer devices.

    

 

            

Outdoor Service AMRs

    

Autonomous Navigation enables many new applications requiring outdoor robots:

• Security Robots

• Las Mile Delivery Robots

• Military Robots

etc...

        

Safety of the Outdoor Automatic Guided Vehicle

       

Safety is the BIG BOSS for whatever autonomous system. Safety is essential. 

  

Mobile Robots must comply with the most exigent safety rules regardless the weather conditions or other area considerations for the application. 

         

Basically, there are two main types of  Safety Sensors:

✅Sensors that avoid contact (safety laser scanners)

✅ Contact Sensors (bumpers, safety edges, etc)

    

I will not discuss the second type at length, because even if bumpers are considered safety certified, the robot must travel very slow to avoid harming someone in case of contact.

     

Let’s focus on the Safety Laser Scanners.

   

Nowadays, almost every AGV or AMR  counts on Safety Laser Scanners to avoid any or all contact between the robot and the surrounding people or structures.

    

The Safety Laser Scanner must detect an obstacle and stop the vehicle to avoid any contact.

  

The detection field dimension and shape must be coordinated with and match the vehicle speed nad inertia.

 

So, if the Outdoor Driverless AGV is running fast, protection field must be longer than a protection field at low speed.

   

Obviously, Safety Laser Scanners must be reliable and sensible.  Similar to other Safety Sensors, they must comply with Standard 62998-1:2019 (Safety of machinery – Safety-related sensors used for the protection of persons).

  

So, here it comes the first problem related to weather: “The Sensibility” of the Safety Laser.

     

⛈ ⛈ If it rains, the Safety Laser could detect raindrops and identify them as obstacles. We have the same problem with fog, snow or even natural sunlight or due to dust or particles in the air. 

      

A Safety Laser must be sensible and smart enough to identify real obstacles but it must be able to filter environmental influences that are not a real risk.

       

 

 

      

Luckily, SICK has developed the outdoorScan3 safety laser scanner that protects people in a wide range of mobile and stationary outdoor applications in harsh weather conditions.

   

The outdoorScan3 is rated PLd accordingly with ISO 13849-1 (Safety-related parts of control systems)  and with IEC 62998 (Safety of machinery - Safety-related sensors used for the protection of persons) specially for outdoor areas.

    

If you want to buy a mobile robot for outdoors.... make sure it is rated PLd

     

Ok, let’s imagine that we have a Safety Laser like the indicated outdoorScan3 able to filter those external influences.

      

The first question would be: Your AGV filters rain... but: How much rain? ????

     

Some Outdoor Safety Scanners ensure 10 mm/hour rain. Great! But how much is that?

Check this video... I love it: 

 

 

      

I have only found this explanation (check this link for more details).

  

✅ Moderate rain: Greater than 0.5 mm per hour, but less than 4.0 mm per hour.

✅ Heavy rain: Greater than 4 mm per hour, but less than 8 mm per hour.

✅ Very heavy rain: Greater than 8 mm per hour.

    

If you are managing a factory, you probably won’t have time to discuss with your autonomous outdoor robotic system supplier situations in which the vehicles stop because of rain… it was raining 10 or maybe 20 mm/hour? Who knows?... and Who cares? 

       

If possible, you should define with your  supplier from the very beginning of the project  what are the possible and acceptable weather limitations and if there are some backup solutions in place. 

     

We're talking about rain, but the external weather influence happens the same with fog or sunlight.

  

How “dense” is fog? How to measure lumens?

 

Safety standards for Outdoor Automatic Guided Vehicles

These are the main safety standards applied in the mobile robot industry. I warmly suggest you to buy and study them to be sure that your outdoor robot complies with latest regulations.

   

   

In the following link, you can find the article where I explain the Safety Rules and Standards applied in the AGV Industry. 

      

Do not forget to download the agvnetwork whitepaper about Safety for AGVs: 

  

  

Click here to download the whitepaper

   

 

What is the best Navigation technology for an Outdoor Automated Guided Vehicle?

     

Here you have my opinion... natural navigation. But let's go ahead... 

     This picture is taken from the slides of the Outdoor Mobile Robots webinar: Click here to Watch it now.

  

We already have a Safe Mobile Robot . Now we need a self-driving robot so ... able to “drive”. In the mobile robot world, “drive” means “localize and navigate”.

      

There are several Mobile Robot Navigation Technologies available for Outdoor applications. Each of these technologies use a set of different sensors for mobile robots. 

  

✅ Magnetic

✅ Vision

✅ LiDAR (also called SLAM or Natural)

✅ GPS

✅ Combination of different technologies

     

 Before explaining them, let me tell you something:

  

"There is not a best navigation technology, there is a best navigation supplier"

       

  

LiDAR, SLAM, Natural for Outdoor Navigation

   

The term SLAM is the acronym for Simultaneous Localization And Mapping. A SLAM AGV is able to map the environment and localize itself in that map without using fixed navigation elements such magnetic tapes or laser reflectors.

 

Typically, mobile robots performing this type of navigation are called Autonomous Mobile Robots. 

     

SLAM is a calculation technique that considers inputs arriving from navigation sensors.

    

Many Outdoor Autonomous Mobile Robots utilize 2d or 3D LiDAR sensors.

     

The main problem with LiDAR sensros in outdoor conditions are wide open spaces with  far walls or contours that could be difficult to reach with laser.

 

In this case, you'd probably need other natural navigation such GPS or a combination of LiDAR and GPS. (see below). 

       

One of the most important advantages of this Navigation Technique is that the associated commissioning is relatively easy and not too expensive. It is possible to track several miles in one day.

    

Another important advantage is that it is easy to modify the robot paths or the robot can even decide its own path.

   

The capacity to decide autonomously its path is a must feature in applications like: 

    

• Outdoor Security Robots (for example in parkings)
• Last Mile Delivery Robots

    

One of the main drawbacks of the LiDAR/SLAM Navigation is its reliability in chaotic indoor applications. If you keep the mobile robot outdoor with well defined contours, everything should work.

  

The problem is if you wish to use the robot also indoors in an extremely variable environment. In general, the algorithms for outdoor and indoor navigation are different and not all the suppliers are able to manage both. 

    

If the indoor application is complex and chaotic, the robot could have navigation problems.

      

Outdoor AGV with Magnetic Navigation

      

Magnetic Navigation is really reliable. It simply works well and works consistently. 

    

 

       

The AGV has a magnetic sensor and follows a magnetic tape embedded in the floor.

   

If you have an AGV with magnetic navigation you can be sure that you will not have any kind of problems related to navigation. Magnetic navigation does not care about weather… rain, fog… it does not matter.  It simply and efficiently works.

    

Nevertheless, there are several disadvantages.

    

The main drawback is the installation cost. Because of the necessity to embed the magnetic tape in the ground there is a high cost for installation, particularly related to longer tracks.

   

Another drawback is that it is not flexible, I mean, it’s hard to modify after installation.

   

It is necessary to mill the floor and replace the magnetic tape in its new location.

   

      

Outdoor mobile robot with GPS Navigation

   

GPS systems provides accurate position and speed in all weather conditions anywhere when at least four satellites are available.

    

Galileo is the European Global Navigation Satellite System. There are currently three other systems: from the US (#GPS), Russia (#GLONASS), and China (#BEIDOU).

    

However, GPS could have problems in urban and indoor areas where satellite signals are unreliable or unavailable.

       

Combination of different Navigation Systems

    

Mobile Robot Suppliers use to work on multi-sensor integrated navigation systems for both outdoor and indoor environments that uses GPS or LiDAR as aiding systems to alternatively provide periodic corrections to Inertial Measurements.

      

It is also possible to switch from LiDAR or GPS to magnetic navigation when passing from outdoor to indoor.

    

Summary about Outdoor Navigation Systems

   

This picture is taken from the slides of the Outdoor Mobile Robots webinar: Click here to Watch it now.

   

 

Management System for Outdoor Mobile Robots

  

 I have to say that this is a pain point.  

  

✅ How do you send orders to a mobile robot that is working outdoor?

✅ In case you have multiple agv vehicles, how do you manage traffic?

    

Whatever the type of robot or navigation technology, you need a “brain” that manages the mobile robot system.

   

In general, the indoor robots are connected to a Management System that assigns missions, manages traffic, and interfaces the robotic System with other Local Systems such PLCs, ERPs, WMS, etc.

 

Typically, these Management Systems are connected via WiFi.

 

So, What happens if you are outdoors?

 

There are three options:

 

• You can install an outdoor wifi net… of course it is a complex and expensive solution if you have to cover a large working area.

    

• You could use a cloud-based management system. This solution is more and more reliable and it can deliver high security connections together with top technical features.  The problem is that there’s still some reluctancy to have an “external” or “cloud” management system.

   

•  You simply could have stand-alone robots without central server or Management System, but in this case, you will have limited management options.

  

  

    

Conclusions

  

Summing up, while mobile robotics is improving and becoming user friendly, some new applications are rising.

  

Outdoor mobile robotics is already here… there are many challenges to overcome… but there are tons of applications where mobile robotics can support outdoor activities.

   

Do not hesitate to contact me here: This email address is being protected from spambots. You need JavaScript enabled to view it. if you wish to know more about Outdoor AGVs and AMRs

    

Related Articles Autonomous Mobile Robots Applications Where are Automated Guided Vehicles Used? What is an Autonomous Security Robot? Automated Tugger AGV Last Mile Autonomous Delivery Robots

---