Automatic Fast Charging of Automated Guided Vehicles (AGVs)

Automated Guided Vehicles (AGVs) are becoming increasingly common in industry following technology advancements and reductions in cost. The use of AGVs to transport materials in warehouses and manufacturing spaces produces significant improvements in efficiency and environmental impact in comparison to other transport methods, such as manually operated forklifts and diesel-powered trucks.¹

Image Credit: Chesky/Shutterstock.com

However, a major limitation of using AGVs is that, because they are battery-operated, charging them either requires automated charging which is very slow, or manual battery replacement which uses up warehouse space.²

This article will discuss the use of AGVs in current industrial practice and considers how robotic charging systems and high-current connectors may offer a solution to the AGV charging problem.

The Benefits of AGVs in Warehouses

On the North coast of Belgium, the logistics and transport company 2XL have employed several unusual members of staff to work in their warehouse. Performing highly demanding manual labor for long hours on end, they work meticulously to make sure that goods are loaded and unloaded correctly. On no occasion do they show up late, nor do they ever take a day off, and each one is capable of lifting over three times the Olympic world record weight to a height of 1.3 m.^3,4

Of course, these employees aren’t human. This warehouse is just one of many now utilizing Automated Guided Vehicles (AGVs) to transport items floor-to-floor.

AGV is an umbrella term used to encapsulate a diverse range of different automated machines varying in size, functions, and guiding systems. A.M Barret Kr. produced the first AGV in 1953 when he enabled a towing tractor to pull a trailer around a grocery store by following an overhead wire.⁵ After this triumph, Barrett Electronics of Illinois offered a simple AGV to market: a tow truck that could follow a wire embedded into the floor of a warehouse.

In 1973, car manufacturer Volvo revolutionized this industry by producing a non-synchronous manufacture line using AGVs, which cultivated to use 280 computer-controlled vehicles. This line was so successful that, eventually, Volvo even began selling their AGVs to other car companies.

Modern-day AGVs have changed since the 1970 models. While early AGVs used wires or magnetic tapes to guide them, current systems now rely on GPS, identification of targets with lasers or cameras, or even intelligent recognition of environments to direct across bustling factory floors. AGV technology has now advanced such that, in addition to factories and warehouses, other applications like hospital waste disposing, nuclear reactor facilities, and even theme park rides are utilizing these systems.^6,7,8

The use of AGVs in industry is enormously beneficial. Lifting and handling are highly laborious processes which, despite our adaptability, can be difficult for humans. Delegating these tasks to a strong, rapid, and proficient team of AGVs ensures a decrease in labor costs and an increase in efficiency.

One example of a highly successful business that has utilized AGVs is Amazon. In 2012, Amazon acquired robotics company Kiva Systems and provided its fulfillment center in California with more than 3,000 small AGVs to redistribute goods for delivery. Following this, productivity was reported to increase by 20%.⁹ Since then, the size of Amazons “robot army” has significantly grown, with over 45,000 AGVs working for them in 2016.¹⁰

In addition to increases in productivity, AGVs are also making factories greener. This is because use of electric AGVs generally means companies are less reliant on traditional diesel-powered transport systems, such as forklifts, which are considerably less sustainable and environmentally friendly.

Smart factory equip with AGVs, 3D printers, and robotic arm (Image Credit: Chesky/Shutterstock.com/)

AGV Limitations

There are, however, some problems that arise when using AGV systems. AGVs must be mobile and autonomous; clearly, they cannot be plugged into a wall socket. This means that the majority of AGVs are battery-powered. Such systems are generally used for highly intensive and continuous work, ultimately, they consume copious amounts of energy and thus require recurrent charging.

AGVs can be charged either by manually replacing the battery with an identical fully charged one or by charging the existing battery using an automatic charging system. However, both methods have their limitations. Additional fully charged batteries are needed for manual battery replacement; these batteries must be stored somewhere, taking up valuable industrial space. Automated charging, on the other hand, can be considerably slow and therefore reduces the amount of potential operational time of each vehicle per day. Both methods pose logistical problems and undermine the basic principles of automation; what good is a robot worker if it doesn’t ensure superior efficiencies?

Solving the AGV Charging Problem

Swiss mechatronics company Stäubli strives to tackle the problem of efficiently replenishing AGV energy reserves with two fronts: robotic charging systems and high-current connectors.

Stäubli’s electrical connectors use innovative MULTILAM technology to enable electrical energy transfer at rapid rates, and contain individually spring-loaded conducting elements which create a very high area of contact when plugged in.

This high surface area permits exceptionally high current densities, allowing transmission of high currents - up to 1000 A / 1000 V - through the removable connector. Custom connectors at higher current capacities are additionally available.^11,12 Significant reductions in charging time, and undesirable downtime of AGVs, can be achieved using these connectors.

Incorporated into robotic charging systems, these connectors are able to charge AGVs so rapidly that their existing schedules need not be interrupted. Specially designed by Staubli, the guiding systems can function under high positional and angular misalignment and are even self-cleaning, ensuring a fast and precise charge.¹³

By coupling high-current connectors and intricately designed robotic guidance systems, Stäubli provides a complete charging solution for AGVs that is safe, flexible, and efficient. Ultimately, this technology removes the need for human supervision and paves the way for total automation of labor-intensive processes.

References and Further Reading

1. Storage & retrieval in warehouses with automated guided vehicles (AGV). Available at https://www.dematic.com/en-au/
2. Scheduling electric vehicles and locating charging stations on a path. Boysen, N., Briskorn, D. & Emde, S. J. Sched. 21, 1–16 (2017).
3. MOTUM Product Brochure. 
4. Automated Guided Vehicles, Storage and Retrieval Machines, 2XL N.V., Warehouse Automation - YouTube. Available at: https://www.youtube.com/watch?v=S8zDRu72HD0. (Accessed: 21st February 2018)
5. History of Automated Guided Vehicles. Available at: https://www.forkliftaccessories.com/. (Accessed: 21st February 2018)
6. Automated Guided Vehicles for Hospitals - Quirepace Ltd. Available at: https://www.quirepace.co.uk/. (Accessed: 21st February 2018)
7. Automated Guided Vehicles (AGVs) for Nuclear Power Plant Refurbishment – Fori Automation, Inc. Available at: https://foriauto.wordpress.com/2017/01/18/fori-automated-guided-vehicles-agvs-for-nuclear-power-plant-refurbishment/. (Accessed: 21st February 2018)
8. RoboCoaster | Automated Guided Vehicles. Available at: http://www.robocoaster.com. (Accessed: 21st February 2018)
9. CNET News - Meet the robots making Amazon even faster - YouTube. Available at: https://www.youtube.com/watch?v=UtBa9yVZBJM. (Accessed: 21st February 2018)
10. Amazon’s robot army has grown by 50% - Business Insider. Available at: http://uk.businessinsider.com/amazons-robot-army-has-grown-by-50-2017-1. (Accessed: 21st February 2018)
11. The MULTILAM Concept. Available at: http://direct.dksh.com.au
12. Staubli single-pole industrial connectors. Available at: https://www.staubli.com/en-gb/connectors/electrical-connectors/single-pole/
13. Automatic Fast Charging Bus and AGV – YouTube. Available at: https://www.youtube.com/watch?v=OcBWqrQpJvs

This information has been sourced, reviewed and adapted from materials provided by Stäubli Electrical Connectors.

For more information on this source, please visit Stäubli Electrical Connectors.