Walmart is to install 3,900 new robots across its US stores, taking over from human employees in various areas of the retail business.

In a bid to help store workers spend more of their time dealing directly with visiting customers, Walmart will install four different types of robot. These will be used to clean floors, scan items to check inventory, unload boxes of stock delivered to the store, and give customers a more convenient way to pick up items they've bought online for in-store collection.

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Speeding up its retail stores with robots is a bid by Walmart to stay competitive with fellow retail giant Amazon, which also employs a number of robots in its warehouses, enabling next-day and even-same day delivery. The robots news comes just days after Walmart announced Voice Order, a way to shop by speaking to the Google Assistant - and a clear counter strike against Amazon's voice-shopping system with Alexa.

Walmart will be installing 1,500 new autonomous floor cleaners, called the Auto-C. Once a worker has prepared the area to be cleaned, the machine gets to work, travelling around the sector of the store which needs its floor scrubbing. This, Walmart says, gives the employee more time to serve customers and answer their questions.

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Next up is the Auto-S, a shelf-scanning robot. Walmart is to install 300 more of these in its stores, automatically scanning products on shelves to check stock levels, correct location, and pricy accuracy.

These will be joined by 1,200 more 'FAST Unloaders', a conveyor belt robot which automatically scans and sorts items as they are unloaded from delivery trucks. Items are sorted based on priority and the department they should be sent to. Walmart says this robot means staff can spend less time in the stock room and more time dealing with customers on the shop floor.

Three thousand new robots will be rolled out to Walmart storesWalmart

Finally, 900 new robots called the Pickup Tower will be installed. These work in tandem with Walmart's in-store collection service, where buyers can purchase items online and opt to collect them at their local store. When an item has been purchased, it is loaded into the Pickup Tower by a store worker; visiting customers can then use the robot like a vending machine to receive their items.

Elizabeth Walker, from Walmart Corporate Affairs, said: "Smart assistants have huge potential to make busy stores run more smoothly, so Walmart has been pioneering new technologies to minimize the time an associate spends on the more mundane and repetitive tasks like cleaning floors or checking inventory on a shelf. This gives associates more of an opportunity to do what they're uniquely qualified for: serve customers face-to-face on the sales floor."

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The focus here is on giving store workers the time to focus on other tasks, which robots are not as good at - like speaking with customers. But the move to expand its robotic workforce will surely seen by many as a sign that Walmart is looking to kerb its labor costs with machines which can work longer hours and do not require breaks, holiday or pay.

John Crecelius, senior vice president of Central Operations at Walmart US, looked to reassure staff: "Our associates immediately understood the opportunity for the new technology to free them up from focusing on tasks that are repeatable, predictable and manual. It allows them to focus more on selling merchandise and serving customers, which they tell us have always been the most exciting parts of working in retail."