Innovation makes Exotec robotic system even more flexible and scalable

After two years of field tests, Exotec has launched a new version of its storage and order picking system in front of dozens of customers. The main innovation is that the improved and more compact Skypod robots are used not only to transport storage bins, but also to feed, discharge, buffer and sort shipping boxes. In doing so, the French warehouse operator adds to the flexibility and scalability of the new generation of robot-driven storage and order picking systems.

By Marcel te Lindert

Companies increasingly prefer robotic storage and order picking systems such as those from AutoStore and Exotec. The reason is the flexibility and scalability of these systems, which is a lot greater than that of traditional miniload and shuttle systems. Anyone wanting to increase their storage or order-picking capacity simply needs to place additional racking or deploy robots, without having to invest in additional roller conveyors, lifts and cranes and without having to make major changes to the control system.

With the new Skypod system, Exotec boosts flexibility and scalability by using the storage system not only as storage for storage bins but also as a buffer for shipping boxes. Because the new robots can knock out shipping boxes at the right time in the right order – ‘perfect sequencing’ is what Exotec calls it – a traditional inflexible sorting system has become redundant, according to the French warehouse operator. In the new Exotec system, adding additional robots is often enough to increase sorting capacity.

Robot-to-robot picking

Storage systems for storage bins do occasionally get used for buffering and sorting shipping boxes. The fact that Exotec is now marketing this as a standard concept is unique. Central to this concept are the workstations that enable robot-to-robot picking. For each pick, two robots arrive at the workstation simultaneously, one with a storage bin and one with a shipping box. The operator has to do nothing more than pick the right number of items from the storage bin and place them in the shipping box, after which the robots leave again. According to Exotec, operator productivity is up to 50 per cent higher than before.

This concept also offers advantages beyond the four walls of the warehouse. Customers can extend their order until the very last moment. To this end, an additional shipping box can be set up, filled and added to the other shipping boxes that have already been prepared earlier within 5 minutes. Because the robots can knock out these shipping boxes in any order, it is possible to match the stacking pattern on pallets or roll containers exactly to the shelf plan in a shop, for example. This saves time when clearing shelves.

More room to manoeuvre

To make the new concept possible, Exotec had to modify both the robots and the racking. The new robots are more compact than their predecessor, allowing them to drive underneath rather than around the racks. To this end, the bottom half-metre of the racks is no longer used for storage. ‘Perfect sequencing is only possible because the robots now have more manoeuvring space. Several simulations have shown that performance would be inadequate without these modifications. The robots would only get in each other’s way,’ head of R&D Louis Esquerre-Pourtere told the launch in Paris.

In addition, the robots now have a different navigation system. The first generation of robots used LiDAR, a kind of radar system that used laser light to scan the surroundings. ‘Because the robots now drive between the uprights of the racks, the margins are smaller and we need a navigation system with greater accuracy. That’s why we now use a grid of lines,’ Esquerre-Pourtere explains. ‘An additional advantage is that we need fewer aisles to reach all storage locations. Moreover, because the robots are more compact, the remaining aisles are much narrower. As a result, storage density is up to 30 per cent higher than before.’

Not so autonomous

Exotec’s mobile robots are not as autonomous as the much-hyped term autonomous mobile robot (AMR) suggests. The promise of AMRs is that they autonomously make their way through the warehouse and sooner or later arrive at the right destination. However, robot-to-robot picking and perfect sequencing require tight, centralised control of the robots. Only then can it be guaranteed that the robots with storage bins and shipping boxes arrive at the right place at the right time. ‘We already had that central control in the previous system. To handle an order efficiently and correctly, that system also required the supply of the storage bins at the right time in the right order,’ says Esquerre-Pourtere.

Exotec uses a fleet management system that tracks and controls the entire fleet of robots in real time. This system meticulously determines the route each robot travels. ‘This is necessary to prevent robots from colliding with each other and to ensure that stock bins and shipping boxes arrive at the right place at the right time,’ explains Esquerre-Pourtere. ‘We are exploring whether using artificial intelligence can help improve the control of the robots, but so far without success. The advantage of the classical algorithms we currently use is their predictability. In the same situation, they always lead to the same outcome, which makes it easier to analyse and fix problems.’

Black box

For the overarching Warehouse Management System (WMS) that companies use, the Exotec system acts as a black box. At most, the WMS knows which stock bin or shipping box is in which location, but has no influence on the inbound, storage and outbound procedures used. Exotec keeps the system closed, and Esquerre-Pourtere does not see that changing any time soon. ‘The system is designed to minimise the total number of movements. A WMS might suggest putting fast runners close to the workstations, but that would mean putting that stock bin back in the same location as well. In our system, a robot puts that stock bin in a free location as close as possible to the next stock bin so that the robot drives around empty as little as possible. With the added advantage that robot traffic is also distributed throughout the system.’

Exotec’s head of R&D does not believe his company is missing opportunities by keeping the system closed. ‘Our system is now running in 130 warehouses with around 10,000 robots in total. We use the same software everywhere to control the robots. And we have optimised our algorithms for each application. This means that all warehouses benefit from all the optimisations we have made over the years. As a result, we are convinced that we have the best control system for our robots.’

Microfiltration centre

Exotec has been careful to introduce the new concept. The new system is already operational in 20 warehouses around the world. One of these is E. Leclerc’s microfulfilment centre in Seclin, a stone’s throw from Exotec’s headquarters in Lille. This French food retailer has been using the system for two years to collect online orders and buffer them until customers come to pick them up. Previously, customers sometimes had to wait 15 minutes before they could load their groceries, now it is 5 minutes at most.

E. Leclerc is able to process some 1,200 orders a day with the new system, 50 per cent more than before. The micro-fulfilment centre has twelve pick-up stations, where groceries are now delivered via roller conveyors. This not only reduces the physical strain on employees, but also gives them more time to assist customers. Partly due to shorter waiting times, this has resulted in a six-fold increase in the number of new customers.

Watch Exotec’s YouTube video here.