How do Roomba Robot Vacuum Cleaners Work?

What is Robot Vacuum Cleaner?

Robot vacuums, sometimes referred to as robot cleaners or robovacs, are autonomous cleaning units that have somewhat intelligent programming coupled with a cleaning motor. Many of them are shaped like circular discs that float across the floor. Some models combine other cleaning features like mopping and ultraviolet sterilization with a basic vacuum. There are even some models on the market that can clean the bottoms of swimming pools and take on other specialized tasks.

Robotic vacuums have been around for quite some time, but we're still a far ways off from the kind of robotic housekeeping staff that were a staple of science fiction for so many years. That being said, even the more demure units we have today can get a lot of work done without any need for a person to pick up an upright or canister vacuum and go to town. While you might not be able to get Robby the Robot to do all your work for you, you can find affordable saucer-shaped robotic gadgets that do a good job of collecting pet hair.

The reasons people want robot vacuums are as varied as the customer base itself. Some people don't have time to vacuum while others put the time their robots save to better use. For instance, you could have a robot clean the floors while you're doing dishes. Nevertheless, few consumers are familiar with how a robotic vacuum works. Learning a bit more about these fun gadgets will make the prospect of acquiring one that much less daunting.

History Of The Robot Vacuum

The development of the earliest robotic vacuum cleaners can be traced back to an early robotic device designed for the education market in the late 1940s. Turtle robots initially developed by William Grey Walter were minor curiosities until Seymour Papert turned computer education on its ear with the Logo programming language. Engineers and students figured that these simple robots could get programmed to vacuum up messes, which gave birth to an industry.

Arguably, the first modern robot vacuum was the Electrolux Trilobite. While developed by a Swedish company, it made its world premier on a British television show in May 1996. At the time, robotic vacuums were more of a curiosity then genuine cleaning devices. Nevertheless, it featured many of the same features that users expect these days including sensors that prevented it from running into the furniture. 

Early reviews complained that the unit was far too expensive. A number of companies have entered into the market since that time, which have made prices drop considerably. Today you can find robot vacuum cleaners that start around $100-200 as well as extremely high-end models that boast price tags of nearly $2,000.

Of these brands, US-based iRobot Corporation is arguably the most popular in the industry with their Roomba line of robot vacuum cleaners. While they weren't making vacuums yet, they have a history stretching all the way back to 1990. The earliest Roomba models came out in 2002, and since that time other companies have joined the fray (picture below). The patent on this device is now almost 16 years old, and one even sits in the National Museum of American History.

First generation Roomba robot vacuum cleaner

First generation Roomba robot vacuum

Traditional vacuum cleaner manufacturers like Dyson have gotten into the swing of things as well as newer firms like Neato and SharkNinja. Competition has increased to the point where prices continue to fall as a result. The entry of other companies have been less expected. For instance, Chinese collective enterprise Haier Group has a long history of making various types of consumer goods. Few people expected them to start making autonomous vacuums, though.

How Does The Robot Vacuum Work?

Robot vacuum cleaners use a system of brushes generally coupled with suction motors to remove dirt from the floor in front of them. They usually work best on hard floors because these brushes are sometimes at odds with thick carpeting, but this is a problem that haunts some regular upright vacuum cleaners too. Support for carpeting has improved over time, but many robot vacuums still struggle to clean carpeted areas. Almost all units are powered by a chemical battery that receives periodic recharges from commercial power mains, though there are some unique solutions to the power problem as well. Here is the general video explaining how does the Roomba robot vacuum work:

Robotic vacuums clean the same way that traditional vacuum cleaners do. Airflow from an impeller motor causes dust and soil to get sucked up into a dust bin for removal. Brushes spin to remove hair and other matter that may be trapped in carpets. These can adapt to different surfaces to clean them better.  Here is quite comprehensive video if you would like to know more about how Roomba robot cleaner works:

For instance, the brushes might spin less vigorously when moving over hard floors than when sucking up dirt from carpet. Some models can also adjust the height of the brushes dynamically so that they can handle thicker carpets. A few higher-end designs feature additional circuitry to handle wet messes, but these are still fairly rare.

Navigation is a challenge, and many vacuums find their way around the floor by using a spiral pattern that constantly crosses over itself. Some use virtual walls that allow homeowners to block off certain areas with infrared or magnetic fields. Others navigate using an ultrasonic noise ping that humans can't hear.

Interface location on Roomba vacuum cleaner

Roomba vacuum cleaner interface

User interfaces are provided by a series of discrete buttons and a small display on most models. A number of them have little more than a few LED lamps that notify users about important conditions such as battery health. Others use wireless networking to communicate with the user through a sophisticated mobile app.

Main Parts Of A Robot Vacuum

Each part of a robot vacuum has a specific function. Due to their size, they're usually not capable of having too much unnecessary decoration. Take the following Roomba 880 teardown video for example:

You'll notice that the design is pretty minimalistic. Any mechanical fluff would add to the weight. That's why even the front bumper has a role to play in a robovac's operation.

Front Bumper

The front bumper is sensitive to the touch, and the slightest amount of pressure on it will cause a robovac to turn around. An overwhelming majority of systems use a spring-loaded switch that senses pressure to the front of the vacuum in order to prevent it from running into any walls or other hard objects. This is of vital importance to prevent damage to your furniture as well as the vacuum itself.

Front bumper location on Roomba vacuum cleaner

Front bumper location on Roomba vacuum cleaner

When the front bumper gets depressed, an electrical switch closes to create a circuit that tells the unit it has come into contact with something. Newer systems use rubber dome switches that are closer in design to those found in most quiet keyboards. This style has fewer moving parts, which means it could theoretically last longer than a physical discrete switch. Some engineers are reluctant to go to it, however, as there are some reliability concerns with this particular design.

Object & Cliff Sensors

Object sensor technology usually prevents robotic vacuums from ever coming into contact with furniture or walls in the first place. Infrared sensors emit a beam of light that's outside what humans can usually see, though you might be able to observe it with a digital camera lens.

Object sensor location on Roomba vacuum cleaner

Location of RCON Roomba sensor

When the beam gets disrupted, this activates an electrical switch. In the process, a circuit gets completed that indicates an object is in the immediate path of the robot vacuum. Depending on the model, it might have several ways to deal with this input. Many robotic vacuum cleaners will simply turn around a predetermined number of degrees in order to avoid it while more sophisticated models will attempt to chart a course around it. The more advanced Roomba models such as 800 series (pictured above) are equipped with RCON sensors. Roomba uses RCON sensors to sense presence of Virtual Walls, Lighthouses, also dock and embark on specific behaviors.

Cliff sensors aren't generally mounted in front of the robot. They're usually on the bottom, and tell the robot if it's approaching something like a staircase or another major drop-off that would cause it damage. When a circuit gets completed as a result of these sensors, the unit generally steers away from the drop.

Cliff sensors location on Roomba robot vacuum

Since these sensors aren't foolproof, most developers have come up with other ways to prevent robotic vacuums from falling down stairs and the like. Invisible walls either consist of infrared emitters or magnetic strips that complete a circuit in the onboard hardware anytime that the unit gets to close to them. A few designs use sophisticated RF transponders to do this while others simply use passive tape. Robotic vacuums won't go near anything marked off with these.

Wheel Drop Sensors

Main purpose of wheel drop sensors is to detect if the vacuum cleaner wheel has dropped off the surface (e.g. if robot vacuum drove over the cliff). Wheel drop sensors are generally wired a small micro-switches, which are located right next to the wheel motors. There is a small gap where the switch gets installed and then a technician needs to properly orient it in order to send an on/off indication to the rest of the unit.

Optical Encoders

Optical encoders are generally located nearby, which are sensors that are located physically on the wheel assembly in order to tell the robot how far it went. Light sensors detect how many rotations the wheels have been through, which provides input that the robot uses to figure out how far it travels.

Battery Pack

A battery produces electrical current by way of a chemical reaction between two different substances. Lithium batteries tend to last longer than other material, so expect to see most manufacturers phase out other designs. Some material, like those involving cadmium, are harmful to users if they're exposed to them. That's why most larger robot vacuum manufacturing companies have already made the change to less toxic designs. 

You may find nickel–metal hydride cells as well, which are made of environmentally friendly materials. These batteries also don't contain measurable quantities of toxic cadmium or lead. Here is the video demonstrating how to replace Roomba 980 battery pack:

Wheels

Most robots use passive wheels that are attached to a miniature axle turned by an electric motor. Hard plastic wheels tend to hold up the best, but they might have navigation problems over some types of carpeting so engineers have started to experiment with different designs. Regardless of what substance they're made from, wheels generally don't contain any electronic components. They're designed to simply move when power is applied to them from an outside source.

Wheels location on Roomba robot vacuum cleaner

Wheels location on Roomba robot vacuum cleaner

Electric Motor Drives

Electric motors use small permanent magnets along with wire windings to convert electrical energy into mechanical force. The conversion isn't perfect, so some current gets wasted as heat. Robot vacuum cleaner manufacturers have worked extensively to reduce the amount of electricity that gets wasted in the motor drive, which has helped to increase battery life over time.

There are two primary types of electric motors used in nearly any device that needs to generate mechanical torque, and both of these two designs are found in robovac equipment. Brushed motors date back to the 1800s, and these designs use a rotary switch called a commutator that's mounted on a shaft. Two soft conductors, referred to as motor brushes, press against this commutator to make electrical contact with it.

Brushless motors are usually considered superior because they don't feature any parts that wear out in a reasonable amount of time. These designs usually feature radial coils that are made from coated copper wire in order to provide torque based on a semiconductor model. These designs are much more expensive, but they offer higher power-to-weight ratios as well as higher top speeds.

Electric Vacuum Motor

Another DC motor provides the suction, which is independent from the motors used for tractive effort. This motor is connected to an impeller that sucks air into the unit. Dust particles small enough to get lifted by this airflow will get carried into the unit's bin for later removal. These motors could be of the brushed or brushless variety, but you'll never see an AC motor used as an impeller since robotic vacuums aren't tethered to a wall socket.

Main Brush Mechanism & Motor Assembly

Robotic vacuum cleaners that have movable cleaning bristles use an electric motor for these, though there are also designs that simply use a passive brush that moves when the unit does. Keep in mind that these brushes have nothing to do with the term brush as it applies to electric motors.

Main brush location on Roomba robot vacuum.png

Main brush and motor assembly location on Roomba robot vacuum

 The term motor brushes is simply an old piece of engineer's slang that we've gotten stuck with over the years. These things aren't literal brushes. Here in the video you can see how Roomba is using its main brushes to clean:

Main brush mechanisms as they apply to robotic vacuums, however, are very literally brushes that clean up hard floors and dig into carpets to get out stubborn dirt. Motor assemblies are generally kept inside of sealed metallic casks that prevent dirt from getting trapped in them.

Side Brushes & Motor Assembly

Some robotic vacuums have side brushes that simply snap in place and help to get dust off molding on the bottoms of walls. More sophisticated models ones have motor assemblies that are identical to the ones used on the full-sized main brushes. In either case, these brushes help to get at dirt that's stuck to areas that the main brushes could never hope to sweep up.

Side brush location on Roomba vacuum cleaner

Side brush location on Roomba vacuum cleaner

You may have seen some specific Roomba models that have toothbrush-shaped appendages sticking out the front. These are specialized side brushes that are attached to rotary motors. They're capable of converting rotary motion to linear motion in order to remove stubborn built-up dust.

How Does The Robot Vacuum Navigate?

Engineers find navigational challenges to be harder to work around than any other part of designing a robotic vacuum. This is because these devices don't have the innate sense of awareness that humans and pets do, so they're not able to simply go around a house based on visual input. They instead use a combination of educated guesses and electronic maps to find their way around.

Some units navigate completely randomly, going around a room for a predetermined period of time until they feel that they've been over every square inch of the floor at least twice. This method does work and it can be relatively easy to implement compared to more sophisticated navigational methods, but it can take a long time. These units turn around only when they sense something in front of them.

Roomba 900 series robot vacuum cleaning pattern

Roomba 900 series cleaning pattern

Active sensors help robotic vacuums to generate maps in more sophisticated models. They usually use an Advanced RISC Machine (ARM) microprocessor to make a series of calculations based on what objects the unit senses and how far it has traveled since the last time it was forced to turn around. You might have heard of ARM chips, because they're used in everything from smartphones to MP3 players. Most of these devices run at least partially open-source Linux software on them to preform the necessary navigational calculations.

Sensors on these models measure the size and density of an object so it can tell if it were furniture, walls or something else. Cliff sensors in particular help robotic vacuums to avoid falling down the stairs as you can see in this funny YouTube clip of someone who seems to want to send their poor little Roomba down for a tumble:

Virtual walls are either permanent magnets or some sort of transponder that send out a signal so that robotic vacuums will treat them as real walls and avoid them. Some units also find their charging station through a transmitted signal that allows the robot vacuum to triangulate the position of it back to where it using the same principle that police do when locating lost cell phones. Other units make a note of the coordinates of their charging dock so that they can go by and find it again later if they need to top off their batteries again.

How Do They Clean?

Robotic vacuums clean the same way that traditional vacuum cleaners do. Airflow fro an impeller motor causes dust and soil to get sucked up into a dust bin for removal. Brushes spin to remove hair and other matter that may be trapped in carpets. These can adapt to different surfaces to clean them better.

For instance, the brushes might spin less vigorously when moving over hard floors than when sucking up dirt from carpet. Some models can also adjust the height of the brushes dynamically so that they can handle thicker carpets. A few higher-end designs feature additional circuitry to handle wet messes, but these are still fairly rare.

Advantages Of Robot Vacuums

Remembering that they're that much like traditional vacuums, it can be fairly easy to consider the advantages and disadvantages of robotic vacuums compared to upright and canister models:

  • Seriously reduces the amount of time spent doing household chores.
  • Vacuums the house at times that would otherwise be inconvenient even when you're not there in some cases.
  • Most units are self-charging and automatically returns to charging station before the battery is empty.
  • Some models integrate with other devices so you can control them remotely.
  • Some models may use much less electricity than traditional vacuums.
  • Works on hard floors where traditional vacuums might struggle to clean.

Disadvantages Of Robot Vacuums

Here is a list of robot vacuum disadvantages to consider before getting one:

  • Robotic vacuums still can't climb stairs.
  • You have to prepare your home and organize it with your robot vacuum cleaner in mind.
  • You'll still need to occasionally use an upright vacuum or a carpet sweeper to get things your robot vacuum missed.
  • Robot vacuum cleaners can sometimes cause damage to walls if they continuously run into them.
  • They'll eventually need to have their battery packs replaced, and the charging station itself may wear out over time.
  • Most robotic vacuum cleaners can't operate beyond a 30-35° slope.

Some Advanced & Cool Features of Modern Robot Vacuums

New options are getting added all of the time when it comes to smart vacuum design. For instance, Sir James Dyson added a camera to a robotic vacuum that was compatible with Apple's popular iOS platform. Other manufacturers will surely catch on to this sort of a trend shortly in order to keep up. You might be able to see exactly what your robot is seeing at all times in the near future, which would help to better understand navigational problems it might be having. This kind of function would also be a great gimmick to bring out when trying to impress friends who share your love of unusual technology.

Voice & Mobile Application Control

Further connectivity with other smart home devices is quickly coming on the horizon too. Most new models coming out support at least some form of smart home integration through their own app while the most sophisticated support voice commands through systems like Alexa, Cortana and Siri. Expect to see more devices that feature their own voice control and possibly synthesis modules as well, since these pieces of equipment will be vital in permitting the units to accept voice commands without the need for a mobile device. They'll probably be able to talk to their owners, too.

Visual Mapping & Navigation

While navigation is likely to remain the biggest challenge for designers of robotic vacuums, there are several emerging technologies on the horizon that should be able to help. Predictive mapping coupled with better data organization through hashed trees can help robotic vacuum algorithms to calculate the right path through a room with a higher degree of certainty than the existing technologies.

Visual mapping sensors can provide video input that's not too different from the way that humans and pets see a room. This input, when plugged into data search software, can help robots to see and thus avoid obstacles. This should also open the door for higher top speeds since robotic vacuums won't have to worry about running into walls as much. Over time, they'll be able to produce maps of a house and won't have to rely on their sensors nearly as much.

Roomba virtual map

Roomba virtual map on the iRobot Home mobile application

Mapping technology has also lead to technologies that can help robots figure out which part of your home gets the dirtiest. One Roomba model maps houses and remembers where it cleans up the most. Over time, it figures out which path is best to take to reach these problem spots the fastest.

This sort of mapping software also lends itself to better cliff avoidance. Instead of using virtual walls, homeowners can tell some robot vacuums where not to clean. You might also wish to use this kind of a feature if you don't want your vacuum getting too close to guests while having dinner.

As you can see in this video, iRobot put these advances to good use when they designed the Roomba 980 to clean an entire level of a home without glitches:

Custom Modifications

Enthusiasts are starting to add their own features. While this can void the warranty of nearly any robotic vacuum on the market, modifying units for custom functionality is becoming very popular. Due to an episode of a sitcom in which a Roomba owner uses his floor cleaner to play music, many people have started to rock out to the sound of their own robot vacuums as the following video shows:

Other people have developed little Nerf launchers and even squirt guns for their robot vacuums. At least one person hacked one to produce marker art, which goes full-circle in a way because Turtle robots in the past made the same kind of art. These modifications aren't recommended, but they're pretty funny.

Privacy Concerns

Robotic vacuums need to collect data in order to perform their chores, which has lead to some criticisms over privacy. New visual input systems brought with them the question of whether or not robot vacuums sell floor plans of their owner's homes for advertising or demographic reasons.

Data That Smart Vacuums Collect

Robot vacuums from the Roomba 900 series, for example, create maps as they work. These allow them to pause mid-cleaning and recharge a battery without need for a transponder signal in the base. They also collect other data about floor coverage in order to do their job effectively. If you're connecting your unit to a wireless network, then it needs to interface with a remote server. This translates into that data being transmitted to a remote location.

How Vacuum Cleaners Use Data?

As well as map data, robotic vacuum cleaners that use voice control have to keep track of information regarding the commands that their users send them. Voice control algorithms by necessity have to learn a great deal about the person speaking to them so they can understand them. Those who integrate a smart robotic vacuum with something like Amazon's Alexa is also agreeing in the process to share this data with computer networks operated by the service they're integrated with.

Vision information also gets used for diagnostic purposes sometimes. Companies want to figure out ways to improve their mapping and navigational algorithms. To do so, they collect user data to preform tests.

What Manufacturers Are Saying?

So far, iRobot has been the most forthcoming regarding details about what it does with user data. The company announced in 2017 that they will not sell user data to outside interests. However, this doesn't mean that they don't plan to collect information. Their statements only regard the sale and distribution of information about their users. People should always make sure to read the full privacy policy of any product before they elect to use it.

While other companies haven't been flocking to discuss their polices with journalists, this doesn't mean that they're not open about what they're doing. The terms of service agreements that pop up whenever someone activates an app clearly spell out how the company uses data. Unfortunately, very few people every bother to read the text of these messages. 

How Consumers And Media Are Handling The Privacy Issue?

Some users are starting to take the time needed to read and understand the agreements they click on. If they don't necessarily agree with everything, then they either choose not to use the features that transmit user data to a remote source or exchange their robotic vacuum for a different model. Companies bend to consumer pressure, so many are now offering different types of devices that offer different levels of data collection.

Media outlets have long either ignored or sensationalized the issue, but this too is changing. A few news outlets have begun providing more information about different collection policies in ways that are more fair and balanced than they have in the past. Others have reminded users to always read software use agreements so they know what kind of information they're sharing with outside sources. This is a good idea when working with any kind of networked technology, and not just robotic vacuum cleaners.

Resources & Further Reading

What Are Robot Vacuums?

Robot Vacuum Parts

Robot Vacuum Navigation

Advantages Of Robotic Vacuums

Disadvantages Of Robotic Vacuums

Advanced Robot Vacuum Features

Robot Vacuum Privacy Concerns