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Using goods-to-person fulfilment for grocery picking

Using goods-to-person fulfilment for grocery picking

At Ocado, we often buck the norm. We have a habit of testing limits, and not only thinking outside the box, but not bothering with the box in the first place. This is exhibited in our use of automation and robotics, our highly advanced routing system and our general reputation as a disruptive technology company. We strive to embrace the latest technologies and incorporate them into our retail business, and the way we pick groceries is no different.

When it comes to delivery-based online grocery, there are essentially two ways to pick customer orders.

In a traditional environment, personal shoppers have to walk through long aisles in stores or warehouses and manually fill trolleys with items needed for delivery. This process is slow, inefficient and requires employees to walk long distances. Such a scenario makes it perfectly possible that a picker would spend 60 percent of their time travelling and less than 40 percent of their time picking.

Pick aisles inside a dark store

Most supermarkets pick online grocery orders in store

While most supermarkets still use this outdated process for grocery picking today, Ocado took a very different approach early on with the help of automation. One of our first ideas was the implementation of zone pick aisles; these are 100 metre long aisles where delivery totes (these are the crates that get delivered to Ocado customers) are routed using conveyor belts to specific pick stations. Once a delivery tote arrives at a pick station, a personal shoppers simply transfers the goods from the shelves or pallets that are closest to the station into customer bags. The picture below shows one of these automated aisles in our Customer Fulfilment Centre (CFC).

Dordon pick aisle

Ocado uses zone pick aisles in its first generation warehouses in Hatfield and Dordon

This design is still fundamentally based around aisles, but provides a definite improvement upon traditional warehouses, massively increasing productivity and eliminating the need for long days of walking back and forth between aisles.

Several years later, we decided to try out a different approach and implemented the first generation of our Order Storage and Retrieval system (OSR1). OSR1 represented a proof of concept project for using goods-to-person automated systems for grocery picking.

The reasoning behind the goods-to-person concept is simple: rather than make the person walk to find an item, you use automation to bring the item to the person – a win-win for the personal shopper as well as for overall business efficiency.

But while the concept might sound simple, it actually requires highly complex software in order to ensure the smooth flow of thousands of totes on the move. One of the biggest challenges for the system is to create a perfect choreography between customer and storage totes as they meet at the pick station. At any point in time, there are about 3000 customer totes at various locations on the outbound conveyor and several thousand of storage totes in the storage tower so the challenge is to ensure that one from each set arrives at the selected pick station within the shortest possible time window.

A bird’s eye view of OSR2 inside the Hatfield CFC

Developing the software for the goods-to-person systems (and all others in the warehouse) is the CFC Systems department, part of the Ocado Technology division – have a look at some of the vacancies available. The CFC Systems developers have to create the algorithms and software which enable the automation hardware to fulfill hundreds of thousands of orders a week.

Once the CFC Systems team put the OSR1 system in place, it achieved a 30% increase in per person pick rate compared to the first zone aisle pick model. However, the team immediately started thinking about how they could build something bigger, better and faster.

First off, they considered the technology they were working with.

“OSR1 was written using Oracle PL/SQL, which, while serving its initial purpose, was not an industry standard for building large scale, real time systems. The system was managed by Oracle using scheduled executions and worked reasonably well, but didn’t allow for the flexibility that a real time solution would give us,” said Krunal Thakkar, head of CFC Systems for our Hatfield and Dordon CFCs.

Therefore, when the CFC Systems team began designing and building the second generation of OSR – OSR2 -, they adopted the Java platform.

“Java is an industry standard with a excellent reputation for reliability and performance at scale. With Java we were able to build a complex, multi-threaded real-time system in a way that kept it maintainable and allows us to easily respond to changing business demands,” said Andrew Wilkinson, team leader for CFC ASOPS systems.

OSR2 at work in our first generation warehouse

In addition to choosing Java as their standard platform, they simplified the design of the pick station and the routing systems from the storage towers to the pick station. This decreased the overall tote journey time significantly and reduced congestion on conveyors, therefore increasing the efficiency of our outbound system. Alongside these features, they also redesigned the storage towers and built the OSR2 storage with a much higher capacity in mind, meaning the Ocado retail team was able to expand the range of different products available on Ocado.com to more than 50,000 items.

OSR2 has also made a huge difference for personal shoppers who can now work faster with less likelihood of errors. From a business perspective, the system has massively increased per-person picking speed by 250% compared to OSR1.

After the implementation stage, the team began focusing on making OSR2 more resilient than either of its predecessors. To minimise the risk of congestion, the OSR2 storage system was designed so that SKUs were spread out between different storage towers. This way, if one tower suffers a hardware fault, the system can continue to pick product and fulfill all customer orders at the usual rate, without negatively impacting capacity.

Picking at an OSR station

Personal shoppers using OSR2 to assemble customer orders in the Dordon CFC

Since introducing OSR2, we have increased our weekly orders from 140,000 to 160,000 in Hatfield, and 180,000 to 190,000 in Dordon; a result we have been very happy with indeed.

Between our various first-generation CFCs, we still use a combination of all three models, because each has its own role to play, and can help us learn and improve upon our own designs. Our original picking solution – zone aisle pick – designed more than a  decade ago now, is a significantly more efficient model than many supermarkets use today.

In our second generation CFCs (also called Ocado Smart Platform CFCs) we are using a completely different approach – and you can read more about it here.

If you’re interested in the career opportunities available in the CFC Systems team, have a look at the roles below:

Holly Godwin, Technology PR and Communications Assistant

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