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How Do Robots Use Sensors to Understand Their Surroundings?

  • Starter
  • Article
  • Ages 10+
  • 4 min read
A mobile robot with cameras and a scanning sensor observing objects on a laboratory floor.

A robot uses sensors to sense its surroundings. A sensor is a part that picks up something from the world, such as light, sound or touch, and turns it into information the robot can use. Cameras, microphones, laser distance sensors and touch sensors each give a robot a different kind of sense.

Contents
A sensor sits between the surroundings and the robot.
  • The surroundings
  • A sensor
  • The robot

What you will learn

  • Name the main kinds of sensors a robot can have.
  • Explain how cameras help a robot choose where to go.
  • Describe how a laser sensor and a touch sensor measure the world.

Before you start

Knowing what a robot is helps, and the first article on robots in this topic covers it.

What senses can a robot have?

A robot can have sensors that work like human senses. Cameras capture images, microphones capture sound, and some grippers have tactile sensors to detect contact.

Hearing is possible too. The Perseverance rover has two microphones, so it can hear sounds on Mars.

Cameras, microphones and tactile sensors can provide different kinds of information.
  • A camera
  • A microphone
  • A gripper with a tactile sensor

How do cameras help a robot find its way?

Cameras act as the robot's eyes for driving. On Perseverance, hazard cameras (HazCams) detect hazards on the paths in front of and behind the rover, such as large rocks, trenches and sand dunes.

When driving, the rover stops frequently to take new stereo images of the path ahead. Stereo images come from two cameras, so they show depth. The robot then evaluates potential hazards.

The 3D views let the rover make its own decisions about where to drive. It does not need to ask the team on Earth about every move.

Two cameras look at the same obstacle, then the robot picks a path around it.
  • Two cameras
  • An obstacle
  • The path the robot chooses
An illustration of a rover using two cameras to see an obstacle and choose a path around it.

How does a robot measure distance with light?

A robot can measure distance with lidar. One form of lidar (Light Detection and Ranging) uses laser pulses to measure distances.

The beam is reflected by the surface it meets. A sensor records the reflected light to measure the distance.

NOAA describes airborne lidar: range measurements are combined with position, orientation, scan-angle and calibration data to create a dense group of elevation points called a point cloud. This is an example of airborne lidar surveying Earth, not a description of every lidar system.

A laser beam travels to a surface, reflected light returns and gives the distance; many measured points together form a cloud of points.
  • Laser emitter and sensor
  • The surface hit
  • Measured points (a point cloud)
The robot sends out laser beams, they reflect from the walls and an obstacle, and many measured points together build up the shape of the room.

How can a robot feel what it touches and where its body is?

A robot can feel by pressing a soft sensor against an object. MIT's GelSight sensor is a block of transparent rubber with one face coated in metallic paint. When that face is pressed against an object, it conforms to the object's shape.

On the opposite side of the rubber block sit three colored lights and a single camera. A group at MIT uses data from GelSight to enable a robot to judge the hardness of surfaces it touches.

A gripper needs two abilities: to feel what it is touching (tactile sensing) and to sense the positions of its fingers (proprioception). Perseverance shows another way to know about its own motion. In blind-drive mode, its computer calculates distance from wheel rotations, without looking or checking for wheel slippage.

A gripper finger with a soft pad and a camera behind it lets the robot feel the shape of what it touches.
  • A finger with a camera behind a soft pad
  • The object held
  • The contact area pressed in

Real-world example

While sitting still, you can touch a few familiar materials and notice what each surface tells you about shape or softness. This is only an analogy for tactile sensing: cameras and touch sensors provide different kinds of information, and a robot does not sense them in the same way a person does.

Common misunderstandings

A robot sees the world as we do. A camera gives a robot pictures. A computer on the robot then has to work out what to do with them, such as choosing where to drive.

One sensor is enough. NASA’s Perseverance has cameras and microphones; in blind-drive mode it also calculates distance from wheel rotations. Each provides different information.

Frequently asked questions

What is a sensor in a robot?

A sensor is a part that picks up something from the world, such as light, sound or touch, and turns it into information. Cameras, microphones and touch sensors are examples.

Do robots have eyes?

Some robots have cameras that work like eyes. NASA says that on Mars, cameras give robots sight.

What is lidar?

One form of lidar uses laser pulses to measure distances.

Can a robot feel touch?

Yes, with tactile sensors. MIT's GelSight sensor lets a robot judge the hardness of surfaces it touches.

Summary

  • Robots can use cameras, microphones and touch sensors to gather different kinds of information.
  • Cameras help a rover detect hazards and decide for itself where to drive, and lidar can measure distance with laser pulses.
  • Touch sensors such as GelSight let a robot judge hardness, and a gripper also needs to sense the positions of its fingers.

Terms in this article

English and Vietnamese terms, with the meanings used here. Hover, tap or Tab to a term with a dotted underline for an explanation as you read.

SensorCảm biến
A component gathering information about a robot’s surroundings or its own state.
Camera
A component capturing images to provide visual information to a robot.
Light Detection and RangingLidar
A method of measuring distance with light; one form uses laser pulses and their reflections.
Point cloudĐám điểm
A collection of measured points describing surfaces, built from distance, position and orientation data.
Tactile sensingCảm nhận xúc giác
The ability to sense an object that a robot is touching.
ProprioceptionCảm nhận vị trí cơ thể
Sensing the positions of a robot’s own body parts, such as a gripper’s fingers.
Stereo imagesẢnh lập thể
Images from different viewpoints that help a system perceive depth.
Hazard cameraCamera tránh nguy hiểm
A camera used to detect obstacles or hazards along a robot’s route.

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Sources

These sources are written for older readers. If they feel hard, read them with an adult.