How Do Robot Vacuums Work? [Complete Guide]

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Ever since the first robot vacuum debuted in 1996, the technology has been evolving at a rapid and exponential pace. It was only in 2015 that they first moved from a remote control to using WiFi, and yet now they use artificial intelligence and can be controlled with your voice.

If you’re wondering how they work under the hood, this guide will break down, in layman’s terms, the basics of how robot vacuums perform their main functions.

What’s Inside a Robot Vacuum?

Here are the basics that make up a robot vacuum cleaner:

  • Wheels – Robot vacuum cleaners have three wheels. Two of these wheels are powered by independent rotors, this allows them to move forward or backwards, as well as change direction by varying the speed of each wheel. The third wheel at the front doesn’t have a rotor and is more for support. The clearance between the wheels and the ground will have an impact on how well the robot vacuum can go over rugs and thresholds.
  • Brushes – There are usually two types of brushes on a robot vacuum, the side brushes and the agitator brushes. The side brushes are located on the front two corners and spin inwards, their job is to push dirt and debris into the centre. Agitator brushes are similar to those on traditional vacuum cleaners, they have hard bristles which rotate into the carpet to loosen dirt in its path, whilst also collecting dirt from the side brushes.
  • Vacuum and dirt bin – The other key element for picking up dirt is the vacuum itself; this collects the dirt picked up by the agitator brushes and deposit it into the dirt bin. Robot vacuums use a bagless design as has become popular in traditional vacuum cleaners. The suction power is measured in either Air Watts (AW) or Pascals (p.a.). Most robot vacuums offer between 1500-2000 p.a.
  • Sensors – As you’d image, these devices are packed with sensors in order to manoeuvre around your home. The sensors on each device will vary depending upon the technology used, we’ll discuss this more later on. The main sensors include wall sensors, object sensors and cliff sensors.
  • Processor – The final key element inside a robot vacuum is the processor which brings all the information from the sensors together, makes sense of it and tells it what to do next. Robot vacuums are becoming more and more intelligent with some devices now using AI to understand their surroundings, this requires a lot of processing power, so the chips are becoming better. Many of the chips are similar to those found in smart phones with quad core processors now commonplace. Some of the best robot vacuum cleaners such as the Roborock S6 MaxV even have an octa-core processor.

This is not an exhaustive list as it is just designed to give an overview, there are many other elements inside such as batteries, charging contacts, WiFi components, etc.

How Do Robot Vacuums Know Where to Go?

There are a couple of different ways that robot vacuums can tell where to go, the most popular these days are random path, vSLAM or lidar navigation. Here is a breakdown of each system:

Random Path Navigation

With photoelectric sensors, the robot will send out a beam of infrared light, this will hit objects and bounce back, allowing the robot to understand where objects are. Most people will simply know this as infrared. Using this system allows the robot to detect obstacles in its path and chart a path, however, it doesn’t map your home as some of the more advanced methods do.

Robots that use photoelectric sensors tend to bounce around the room in no logical order until they deem that the room has been cleaned. As they do not have mapping capabilities, the cleaning coverage can be very patchy as they have no way of telling which areas have and haven’t been covered.


VSLAM stands for visual simultaneous localization and mapping (bit of a mouthful). This method involves camera’s mounted on top that uses both the ceiling and points of interest to map the shape of the room. Once it has determined points of interest, the cameras can triangulate a 3D map of the room and use the onboard motion sensors to track its movement.

This is more accurate than simple photoelectric sensors, but not as accurate as Lidar because the cameras can misinterpret how far away an object is which throws it off. However, the technology is much cheaper than lidar which is why it is currently more common.

Some VSLAM devices may struggle to work in the dark, Dyson’s 360 Eye was a key example of this so their follow up model, the Dyson Heurist, has LED lights built in to help.

Because VSLAM uses visual cameras, it has the most potential in future as these products become more intelligent, for example it might be able to distinguish pet poop from a toy and avoid it, whereas a laser wouldn’t be able to do this.


The more advanced robot vacuums with mapping will use Lidar technology. Lidar, which stands for light detection and ranging, has long been used in mapping the Earth and has most recently been applied to autonomous cars. So, you can imagine that it creates a pretty accurate and detailed map.

Lidar mapping allows for a much better clean as the robot can operate in straight lines and take a logical path ensuring it does not miss spots. It is also much quicker to create the initial map which can usually be done on the first cleaning mission. Robot vacuums that use Lidar include most Neato devices and the higher end Roombas such as the S9+.

All of the Above

Manufacturers are being very clever with their use of mapping technology and sensors in robot vacuum cleaners, so it’s rare that you’ll fine two that are exactly the same. Some are also starting to use hybrid systems that combine many of the above techniques to refine the robot’s capabilities.

Both Lidar and VSLAM have strengths and when combined can be make very intelligent and effective robot vacuums.

How Do Robot Vacuums Find their Base?

The technology employed in the base units of robot vacuums hasn’t really changed since before they were smart. The base units use infrared beacons to signal its position to the vacuum so that it can return when it needs to recharge.

As long as the robot or the base are not picked up and moved during cleaning, the robot should be able to return to the base, even if it is not in range of the base during the entire operation.

In most robot vacuums, the base itself doesn’t have WiFi connections, this is found within the vacuum itself and allows for app control or activating using Alexa or other voice assistants.

Related Post: Alexa Commands for Roomba

Image credit: Roomba

How Do Robot Vacuums Clean Corners and Edges?

The main body of a robot vacuum is usually a circle (or D-shaped in some newer models) which leads many people to incorrectly think that they cannot effectively clean walls and corners, but this is incorrect.

They manage this using spinning brushes on each side at the front of the device that reach out to the edges and corners. These usually have three brushes that spin inwards, pushing the dust and dirt into the centre of the robot to be picked up by the main brush and vacuum suction.

If you need to visualise this, think of the brushes on road sweepers that collect the rubbish from right in the kerbside. These brushes do need regularly replacing and is one of the maintenance tasks that you’ll need to perform to ensure it continues to operate to its best ability.

How Do Robot Vacuums Work with Stairs?

There isn’t yet a robot vacuum cleaner that has taken on the challenge of vacuuming stairs, although it’s probably only a matter of time. However, one of the glaringly obvious dangers is your robot vacuum falling down the stairs. Let’s be honest, you don’t want to spend hundreds of your hard-earned cash on a robot, only for it to launch itself down your stairs.

Luckily, most decent robot vacuums have learnt how to avoid stairs and any nasty accidents they could cause. They manage to do this via cliff sensors which are built into the base of the vacuum at the very front.

This is usually a basic infrared sensor that constantly bounces light off the floor and measures the response time, if the light takes longer to return then the vacuum knows the floor has disappeared and not to proceed. Sometimes cliff sensors may use other forms of light such as ultrasonic or optical.

These cliff sensors have been known to cause difficulties, especially for anyone with dark black carpets as the black can absorb the infrared light.

How Do Robot Vacuums Empty Themselves?

The latest generation of robot vacuums are able to empty themselves, allowing them to go longer without human intervention. This is ideal in larger homes or homes with pets that can quickly fill up the 500ml dirt bin typically found on the devices.

Robot vacuums are able to empty themselves thanks to a larger base unit that has a second suction motor. This sucks the dirt out of the bin on the vacuum itself in much the same way that a typical upright vacuum cleaner would.

Whilst none of the popular robot vacuums use vacuum bags, some self-emptying bases have gone back to this technology that seems to have been left behind in the traditional vacuuming world. The Roomba self-emptying bases use vacuum bags.


I have been building up my smart home since 2016 so I'm a bit of a smart home expert by now. On this blog, I share my favourite smart home devices that I've tested along with tips and tricks I learn by watching countless YouTube videos, scrolling through forums, and tinkering around with my own smart devices. I've always been a Google Home user but I'm starting to think Alexa might have the edge, what do you think?