How does a roomba work?

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Taylor Covington

Content Researcher

As a qualitative researcher for The Zebra, Taylor collected, organized, and analyzed data to shine a light on trends in the insurance industry and be…

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For nearly 20 years, Roombas have been working hard to make our homes tidy. Made by iRobot, these robotic vacuum cleaners use sensors to detect walls and items in a room, becoming smarter the more frequently they clean. And as Parks and Rec taught us, they make for great DJs, too.

You’re likely familiar with an iRobot Roomba and may even own one already. But how does a Roomba actually work? Here’s an overview of the robot vacuum.



How does a Roomba work?

Just as humans have values we live by, there are set rules of Roomba. These rules determine how the Roomba functions. For example, the robot vacuum might start in the middle of a room, vacuuming in an outward spiral pattern to clean a concentrated area, rather than moving in a straight line. It then heads to the walls of a room.

Additionally, Roomba will adopt patterns as it cleans. The two main patterns: wall following vs random bounce. As its name suggests, the wall following pattern cleans the perimeter of a room. Roomba will navigate around or under furniture as it cleans. Roomba can also use a random bounce pattern, where it will move around the room until it hits an object. When it does, it changes directions and moves elsewhere, ensuring the entire room gets cleaned.

As CNET notes: “Roboticists call these rules “behaviors,” and they are simple things like if you hit a wall, turn away from it.”



There are four main parts to Roomba: sensors, bump, wheels, and brushes. These parts work in tandem to tackle tile, hardwood floors, carpet, and anything in between. Here’s a quick overview of each part:

  • While we use our eyes to see, a Roomba uses infrared and photocell sensors to navigate around a room. These sensors each serve a different purpose: cliff sensors let the vacuum know when it’s near a “cliff,” such as stairs or a balcony. If it senses this, the vacuum will back away from the ledge. Similarly, wall sensors let the vacuum know a wall is nearby, but Roomba will follow the path of the wall instead of retreating. 
  • B2K may be all about that “bump, bump, bump,” but a Roomba only needs one bump to get the message. If the robot bumps into something, the force of impact causes the sensor to trigger, sending the robot in a different direction. This impact has to be from an immovable object, such as a table leg, a kitchen island, or even a wall itself.
  • The wheels of a Roomba contain optical encoders, which use a light sensor to determine how far the Roomba has traveled. 
  • Roomba vacuum cleaners use two multi-surface brushes. The first brush loosens, lifts, and pulls in debris, while the second accelerates it into the vacuum’s suction channel. 


Robot vacuums can thank ants for their creation – the initial patent iRobot filed in 2002 references ants as an inspiration for Roomba. Though ants don’t have much brain capacity, they have a similar set of behaviors that help dictate their actions.

Diving into Roomba Sensors

Roomba’s most innovative features are its sensors, which help as it navigates around a house. How do all of these sensors work to let Roomba operate smoothly and efficiently?

Infrared waves, also known as infrared (IR) light, are a part of the electromagnetic spectrum. Though humans can’t see IR light, we can sense it as heatCommon uses of infrared include night vision (the ability to detect objects in dark environments), as a tool for predicting weather patterns, and as tracking technology.

IR (1).jpg


A photoelectric cell (or photocell) emits a visible or infrared light beam from its light-emitting element. A reflective-type photoelectric sensor can then detect the light beam that the target reflects. Another sensor measures the change in light quality.

A Roomba contains both infrared sensors and photocell sensors, which work in combination to clean a room. The infrared sensor at the very front of the Roomba allows the vacuum to bounce light off an object to detect its presence, even if it’s cleaning after dark and there’s limited natural light. A Roomba measures how long it takes for an emitted infrared beam to bounce back to the photocell sensors, which provides more precise object detection. In essence, the photocells measure changes in light levels, while the infrared sensors can detect changes in motion.

Finally, a Roomba also has a piezoelectric sensor, which is easily the most fun of its sensors to pronounce. As Explain That Stuff explains, piezoelectricity is “the appearance of an electrical potential (a voltage, in other words) across the sides of a crystal when you subject it to mechanical stress (by squeezing it).”

While it might sound like something out of a weird science textbook, we regularly use piezoelectricity. It occurs in watches and clocks, microphones, and printers. A Roomba uses its piezoelectric sensor as a dirt detector. When bits of dirt hit the sensor, the Roomba receives tiny electric impulses. Enough impulses will prompt Roomba’s dirt detect to kick into gear – a second, more thorough cleaning of the area.

Features of newer Roomba models

After nearly two decades on the market, Roombas have seen upgrades over the years. Newer models offer several advantages over older ones.

Roomba 980 and later models (including the Roomba i7) use Vision Simultaneous Localization and Mapping (VSLAM) to dynamically build a map while maintaining a bearing on its surroundings. With the Roomba 980, there’s a forward-facing camera angled up at about 45 degrees. That camera takes a picture of the room’s floor plan, and the robot’s software seeks out patterns in the picture’s pixels. This navigation system helps Roomba clean in straight lines in one pass, rather than needing to go over the same part of a room multiple times.

Battery life/power is also more efficient with newer Roombas. iRobot products are powered by rechargeable ion or NiHM batteries (with newer models adopting ion batteries), which can usually last for about 90 minutes before recharging. However, as they are entirely self-charging, Roombas are smart enough to head towards a charging station when their battery life is running low, and will dock as they regain a charge.

Though newer Roombas can function without WiFi, the iRobot Home app available on the iPhone and Android app stores adds extra convenience for newer models. After connecting to your home network, you can program a cleaning schedule through your smartphone, as well as learn more info and set up behavioral rules for your Roomba, such as actions to take when the dustbin is full.

It’s not only our vacuums that are getting smarter. Connect your Roomba to the same network as your Google Home and you can delegate scheduling a cleaning session to your smart home. Also available to Amazon’s Alexa, you can tell Google Assistant to “start”, “continue”, and “stop” cleaning and your Roomba will resume those functions and return to home base when it’s done.



Having a pet is wonderful, but constant shedding is certainly a downside to pet ownership. While dog/pet hair could clog up brushes of older Roombas and sometimes spread the hair around a room, newer models are more adept at vacuuming pet/dog hair from carpet. What’s more, the i7+ model can empty itself. That means pet owners don’t have to worry about the unsightly remnants they might find in a dustbin. The virtual walls in newer models present a way for Roomba to avoid things you keep on the floor but don’t necessarily want moved around, like a pet’s bowl. 

Roombas helped revolutionize the robot vacuum industry. iRobot and other companies are continuing to innovate and grow our robot helpers. And vacuums aren’t the only innovation worth watching. We’ll continue seeing automation and technology developing in new ways to improve our lives at home