Sensors for Robotics - 5 Common Types

2022 January 19

 

 

 

 

Sensors for Robotics

 

From low to high-complexity applications, robots depend on robotic sensors for efficiency, safety, and performance.

 

 

 

 

 

 

 

From low to high-complexity applications, robots depend on robotic sensors for efficiency, safety, and performance.

What is a robotic sensor?

Robotic sensors allow systems (fully-automated and remote-controlled) to measure properties of the physical world.

The sensors used in robots are typically based on electromechanical circuitry and can be of two general types–digital or analog. Both can be routed to a microcontroller.

An easy comparison is that of digital and analog watches. An analog watch tells you what the hands are doing and you interpret the time based on the universal measurement (watch face). A digital watch is tracking the time and tells you what time it is on its readout.

Just like the example of watches, analog sensors are–as a general rule–fairly simple to incorporate into a system. Digital sensors, while more capable of performing interpretive processes while sensing, are typically more complex.

Thanks to advances in engineering technology, you don’t have to worry as much about digital versus analog sensors. Take a look at our full suite of high-quality sensors ready to take your automated system application to the next level.

Why do robots use sensors?

Robots use sensors to evaluate their surroundings so they can respond to and manipulate their environment.

Robots are, in a sense, extensions and magnifications of human capacity. Thus, robotic sensors can be viewed as mirrors of the human senses.

In the same way that humans become less efficient when a sense is removed or diminished (think, closing one eye and playing catch), robotics depend supremely on their sensors for efficiency, safety, and correct performance.

Let’s consider the five human senses we all know and love,

  • Hearing
  • Sight
  • Smell
  • Taste
  • Touch

There are robotic sensors that easily accommodate for these senses, like:

  • Audio and ultrasonic sensors
  • Object detection and proximity/range sensors (LiDAR, radar, etc)
  • Gas sensors (smell and taste accounted for with this one)
  • Contact sensors

Well, that does it. All engineers have to do is incorporate these five senses into a robotics system. There aren’t that many senses after all, right?

Wrong.

If you have any experience in robotics or life sciences you know this is obviously not the case. Not only is the incorporation of merely five senses more difficult than it seems at surface level, there are many more senses recognized by your brain and body.

Now, here’s a short list of of some of the other sensors in our bodies for which our brains compute:

  • Proprioception (where the body, and each joint individually, is in relation to the rest)
  • Stereognosis (relative weight, ability to sense object properties through touch)
  • Stretch and tension sensors (muscle spindle fibers and golgi tendon organs detect when a muscle is stretched too far or a load is too great for a given joint)
  • Thermoreceptors (temperature sense)
  • Nociception (processing and determining “pain” or danger to the body)
  • Vestibular sense (ability to tell if you’re upright, which direction you’re turning)
  • Depth perception (how far away an object is)

 

The human brain processes all of these and more and coordinates them together to perform the functions of life and living.

It’s no wonder we named our hardware to software integration technology “Brainstem” as a nod to the original supercomputer.

Now that we’ve briefly covered the need for sensors in robotics systems, let’s explore how robots practically use them.

How does a robot sensor work?

 

It depends on the type of sensor, but most rely on emitting an output, receiving input, and using the differences in signals to make observations and assessments.

A number of sensor types are used to allow automated systems to assess and interact with their environments.

If you want to get a full understanding of sensor functions and use cases, check out our sensor breakdown page.

Sonar is a good example to explain how sensors work because there are active and passive sonar sensors. Passive sonar sensors use a microphone to receive sound waves. The intensity of the sound waves can be used to determine certain qualities of the “thing” being sensed. Through the use of multiple passive sonar sensors you can triangulate position and distance of an object.

Active sonar sensors exemplify a sort of “new era” of sensors that work more efficiently. An active sonar sensor not only receives sound waves but emits them, too. By emitting sound waves and receiving the echo or return sound waves, a single active sonar sensor can perform location and rangefinding tasks.

Of course, sensors are useless without a processing unit. Information is meaningless unless it’s interpreted.

In robotics applications, the types of sensors used are specific to the tasks the robot performs. Robotic vacuums involve contact sensors in the form of bumpers that tell the computer it’s found a wall. The computer takes that information and tells the wheels to turn the vacuum on an axis and try moving another direction.

Industrial robotics sensors can be used to accurately and quickly measure the fill of products for packaging using time of flight (ToF). Thermal sensors can provide visual information in safety capacities–information that would often be dangerous for humans to assess through touch.

What types of sensors are used in robots?

First things first, you’ll be hard-pressed to find analog sensors in an autonomous system. So, digital sensors are used in robots unless the robot has a function of telling you some information that can be expressed in analog.

Let’s imagine you have a robotic dog (man’s best friend?) to go through 5 of the different types of sensors used in robots.

1. Cameras in robots

Cameras have become increasingly used in automated and autonomous systems. Like self-driving cars, a camera feed from your robot dog’s “eyes” can be interpreted by a recognition program that tells it when to shake its tail when it sees anything resembling a bone.

Say you want to keep your canine from interacting with things that would injure it’s surface. You could have thermal cameras in place which would relay color-coded temperature information to the processor and tell the dog to avoid objects above a certain temperature in its environment.

Thermal sensors (like the Terrabee EVO Theraml 33) combined with cameras can also be found in applications for human detection and counting in addition to being used for safety checks in or around oil rigs.

2. Rangefinding sensors

Sensors used to measure distances apply a principle known as time of flight. Simply put, this principle compares the time it takes for an emitted wave particle to leave and return to the sensor. That time is solved for distance with the inclusion of the medium through which the light, sound, or radiofrequency wave has travelled.

With the use of range finding sensors, your robot dog can determine the distance between itself and the couch it intends to jump to and produce the right amount of force to not over or under-shoot the target.

Similarly to drone applications, the ToF sensor could be used to find the distance from the ground and maintain, or properly accommodate for, that distance.

In industrial applications, ToF sensors have been used for intricate details of filling automation and for wide-scope measuring of ground surface coverage in agricultural industries.

3. Sonar sensors in robots

As common knowledge describes, sonar is often used in marine or oceanic functions because sound waves travel faster in water than other types of particle waves do.

However, as touched on above, ultrasonic sonar sensors can be used for ToF in above-water applications (we carry quality, affordable Devantech sonar rangefinder, like the SRF05). Because they don’t travel as fast or far in air as they do in water–but are quite lightweight and compact–you might want to put these in your robot dog for near-field ranging and object avoidance.

You could also affix a microphone to your robotic pup so it can, with the right programming, “hear” and recognize your voice and/or commands.

In manufacturing and safety, sonar sensors are a great choice because they aren’t as limited by conditions as light sensors might be. For example, in poor weather a LiDAR sensor might have trouble locating something through the raindrops. An ultrasonic sensor would be less likely to be “distracted” by the conditions in this case and better suited for finding its target through rain.

That said, if sonar is not working for you in poor conditions, you might give radar a try.

4. Robotics applications using radar

Because radiofrequency waves have a longer wavelength than light, the resolution of radar compared to LiDAR can be poor (though there are short-wave applications available, called mm-wave radar).

This makes radar excellent at long-range object detection in any condition. Because it may not detect finer details of an environment, radar imaging is the least likely to “miss” its target through haze or dust. Agricultural and aerospace applications can especially rely on radar.

Your robot dog could use radar if it had hunting-dog programming, being able to locate objects at range through distractions. It would be helpful to position the sensor on the dog's swivelling head, as radar has a relatively narrow field.

5. LiDAR sensors in robotics

LiDAR uses light waves to detect objects and acquire ranges. Because light waves have such short wavelengths and high frequency, LiDAR sensors can detect superfine details at greater degrees of field.

If your robot dog was involved in rescue operations or building safety it might benefit from, or require, LiDAR. Thanks to its high resolution, LiDAR sensors can “notice” and therefore respond to more discrete information.

LiDAR is often chosen for 3D imaging applications through the use of “point-cloud.” By finding the distance to multiple objects at high resolution quickly, an autonomous system can develop high quality pictures for AI use or comparative analysis.

Which sensor should you choose for your robot?

 

The type of sensor you choose should be compatible with the intended purpose of your automated system and suited for the environment in which it will function. With such varied applications of sensors available, it might be challenging to come to a decision. We’re eager to offer our expertise and help you decide, contact us for help!

For example, even though LiDAR provides the highest resolution object imaging and detection, it might be too heavy for your bot. Thankfully, there are a number of ways to integrate different sensors and accommodate for their differences.

Shop our line of top-quality sensors for smooth integration and operation of your autonomous system.

 

 

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