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How Do Robot Vacuum Cleaners Work?

Your robot vacuum scoots around your house, sucking up dirt, dust, and crumbs. Every few hours, it parks itself on the charging dock. The only time you really interact with the robot is to empty its dirt bin, replace the filter or remove hair from the brushroll.

How Do Robot Vacuum Cleaners Work

Have you ever wondered why your robovac knows not to get too close to the stairs? How about that map on your smartphone? How is it drawn? We’re here to answer those questions and make robot vacuums less mysterious by taking a detailed look at all the components in a typical robotic vacuum cleaner.

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Battery Recharging and Robot Docking

Whether it has a nickel-metal hydride or a lithium-ion battery, today’s robot vacuums are designed to recharge the batteries themselves. This is called self-charging or auto-docking, and virtually every robot vacuum offers this feature.

For self-charging to work, the accompanying dock must be placed where the robot can find it. This means there should be no clutter within several feet to the sides or the front of the dock because the dock emits a signal beacon the robot uses when it needs to locate the dock.

A dedicated sensor determines when the battery level is too low for the robot to continue vacuuming. When this occurs, the robot’s software tells it to search for the dock’s infrared signal beacon. Once the robot finds the beacon, it drives itself to the dock where it sits until the battery is recharged. Certain models are programmed to automatically start cleaning where they were when they left for the dock – This function is called auto-resume.

Robot Vacuum Cleaners

Wheels – A Sensor, Motors and Assembly Housings

Robotic vacuum cleaners are equipped with two main wheels that allow the robot to move forward and backward. They also have a caster, which lets the robot turn directions. The wheels and the caster are housed in a separate assembly.

Each wheel is powered by its own motor while the caster mechanically rotates. Although the two wheels are motor-driven, some robot vacuum wheels are connected to a sensor. A wheel sensor’s job is to calculate the distance the robot travels by counting the number of wheel rotations. Therefore, while a wheel sensor is part of a robot vacuum’s mobility system, it also serves a navigational purpose.

Spinning and Rotating Brushes

Like the wheels, the brushes are controlled by a motor. Usually, the side brushes have their own motor, and the brushroll has its own motor. These motors spin the side brushes and rotate the brushroll at high RPMs to sweep debris toward the suction inlet and lift debris from the floor, respectively.

To date, the only robot vacuum manufacturer that puts a sensor with the side brush is Samsung. These robot vacuums actually have a rubber edge-brush. When the robot gets close enough to the edge of a wall, the sensor tells the robot to drop the edger, which pulls dirt and dust toward the suction inlet.

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Suction Power

What determines a robot vacuum’s suction strength? While the wattage of motor certainly plays a role, it’s mostly the size and capacity of the battery that determines the power of the suction. Manufacturers usually measure a robot vacuum’s suction in pascals, and the pascals can range from 400 to 2,000.

Due to the size difference, a full-size vacuum produces more powerful suction. However, the brushroll and side brushes help supplement a robotic vacuum’s suction strength. For robots, like several Roombas, that have a self-adjusting floor plate, a sensor raises and lowers the plate, so the inlet is close to the floor’s surface, enhancing the suction.

Automatic Suction Increase

Several robot vacuum brands have an automatic suction-increase function. You may see this function termed as dirt-detect or max-mode. As with many of the features on a robot vacuum, auto suction-increase is sensor-based.

The suction sensors are positioned underneath the brushroll assembly, and they are of the acoustic variety. The sensors rely on vibrations that come from concentrated areas of dirt. These vibrations set off the sensors, prompting the robot to kick up the suction a notch and continually vacuum over the extra-dirty areas. When all the dirt is gone, the suction returns to its normal level.

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Collision and Fall Prevention

Over time, robot vacuums have become less accident-prone and more sophisticated at detecting and avoiding obstacles and drops. Infrared sensors help the robot dodge furniture, people and other obstacles in its path. The sensors send signals. If the signals return to the sensor, the robot keeps moving. If not, the robots change direction, so they won’t hit Fido while he’s napping or fall down the stairs.

Some robot vacuums will slow their speed when the sensors detect objects. Others are equipped with a bumper. The bumper not only cushions the robot from the shock of a collision but also tells the robot to travel in a different direction via sensor technology. The most advanced robot vacuums know whether to turn right or left according to the part of the bumper that makes contact with an object.

Mapping and Navigating

The anti-collision and anti-fall sensors are just two parts of a robotic vacuum’s navigation system. There are also infrared sensors that pinpoint the location of walls, so the robot can vacuum along the edges without making scuff marks. Walls sensors may also give the robot an idea of the size of a room and the location of doorways, depending on whether the robot has mapping capabilities.

Robot vacuums that map a room rely on the sensors to send information to the robot’s microprocessor. Using software and algorithms, the robot will learn exactly where and where not to vacuum. Some mapping-capable robotic vacuums have GPS software too. Distance-calculating lasers are another type of technology manufacturers use for room mapping.

Those that are Wi-Fi enabled have an onboard camera, which transmits images to a smartphone with the associated app installed. From the app, the user can see a floor plan of their house, With high-end Wi-Fi models, the user can control the cleaning zones by simply touching the rooms on the map.

Basic robot vacuums aren’t able to map. Instead, infrared sensors are their sole means of navigation. These robotic vacuums move in a straight line, randomly bouncing from one end of the room to the other until all the exposed floor is clean, which is different than the side-to-side-up-and-down movements of mapping-capable robot vacuums.

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Virtual Barriers

Virtual barriers come in several forms – barrier strips, virtual walls, halos, and lighthouses. Barrier strips are magnetic. When laid on the floor, the robot vacuum senses their presence, and it avoids them like it would with obstacles and drops. Barrier strips don’t require batteries, and they can be cut to size. Since they aren’t adhesive, the strips can be reused.

Another type of barrier is called a virtual wall. A virtual wall is a battery-powered device that’s placed on the floor. When turned on, the device emits an infrared beam in a straight line. A sensor on the robot vacuum detects the beam, and it will change its course instead of crossing that line. Halos work like virtual walls except halo barriers create a circular no-cross zone around the barrier. Some barriers can create either a wall or a halo.

Finally, there are lighthouses. The purpose of a lighthouse is to keep the robot vacuum contained to a single room. A lighthouse creates an infrared beam of light as well as radio frequencies to control where the robot goes.

Scheduled Cleaning

User-programmed scheduling is perhaps one of the most convenient features offered on robotic vacuum cleaners. Some robots can be scheduled to vacuum at different times on different days while others can only be scheduled to vacuum at the same time each day.

Whether the schedule is set with a standard remote control from across the room or a smartphone when the user is across town, the process works the same way. The manufacturer uses software so that the robot can remember the cleaning schedule. Once the user sets the schedule, the robot leaves the dock and starts cleaning at the pre-set time.

Depending on the size of the area to be vacuumed, the robot vacuum may self-dock during the cleaning session. If the robot does not have an auto-resume function, the user will need to start another session. If the robot does auto-dock and auto-resume, it will continue vacuuming when it’s done charging. When the job is finished, the robot re-docks itself until the next scheduled vacuuming time.

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Self-Emptying Bin

Dumping dirt out of the robotic vacuum’s bin is typically a manual task left to the owner. However, certain robot vacuums have a self-emptying feature that partially automates this task. A self-emptying dirt bin has a sensor that lets the robot know its bin is full.

When the bin needs to be emptied, the robot makes its way to the dock, which has a larger bin attached to it. The dock suctions out the contents of the robot vacuum’s bin into the dock’s concealed vacuum bags. The dock that comes with one of these self-emptying robots can hold over two dozen loads before the user has to remove and replace the vacuum bag.

Recommended Robot Vacuums

Affordable Option The iRobot Roomba 694 is a basic robot vacuum. It feels well-built, offers fantastic battery performance, and can adjust its suction power and brushroll height automatically depending on the surface that it's on.

Best of the Best The Roborock S7+ can vacuum and mop, and does an excellent job at both. It's also the company's most powerful vacuum yet, with 2,500Pa of suction.

Popular Option The Shark AV911S EZ is one of the least expensive robot vacuum with self-empty base. The bagless, self-emptying base holds up to 30 days of dirt and debris.

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About the author

Hi I’m Alex, founder of HouseholdMe.com and I’d like to say thank you for dropping by. Like most of you, the first thing I look at before buying something online is reviews or buying guides. By reading what other people say will help me gauge whether or not a product is good or not.  I am trying to help people find answers, solve problems, and get inspired.

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