15 Different Types of Robots | Explained

Artificial Intelligence (AI) and Robotics are undoubtedly two of the most promising fields of study right now. These two will certainly define the future of humanity.

At present, we have ultra-modern machines with sleek designs and agile and highly capable bodies, which can perform a wide range of tasks with efficiency. We also have machine intelligence, which is literally revolutionizing the way we do most of our work.

While AI is always an interesting subject to talk about, as we did countless times here on our website, let’s talk about robots today. As you might know, there are many different ways in which one could differentiate robots. I am sure that you know at least some of them, but there is always more.

Basically, robots can be divided into two broad categories: based on their applications and kinematics or locomotion.

Below, we have only classified robots based on kinematics. Why is it so? Well, the application of any subject, especially robots’, vaguely describes its characteristics. For instance, two different types of robots can perform the same job, yielding the same result.

We have only mentioned major robotic types, and they are further subdivided based on kinematics. 

Robotic Arms or Stationary Robots

1. Cartesian Robots

Cartesian robotImage Courtesy: Florian Schäffer/ An implementation of the cartesian robot

Cartesian robots are perhaps the most common type of robot used for both industrial and commercial purposes. Sometimes known as gantry robots, they have three linear axes (which means they can only move in straight lines) and are mounted at right angles. The mechanical arrangement of cartesian robots is far simpler than most other stationary robots.

2. Cylindrical Robot

 

cylindrical robot

Cylindrical robots are generally used for assembly purposes, spot welding, and machine die castings. Although these types of robots are relatively rare these days, they can still be useful. As the name suggests, it forms a cylindrical coordinate working system.

As you can see in the diagram above, a cylindrical robot has three axes of movement. On the Z axis, it rotates and moves vertically; and on the Y axis, it moves along in a linear motion. Sometimes these cylindrical robots are mistakenly regarded as SCARA robots or vice versa. Even though their work envelope is almost similar, both their structures and field of application are poles apart.

3. SCARA robots

 

SCARA rightGif Source: Wikimedia Commons

SCARA or Selective Compliance Assembly/Articulated Robot Arm is more commonly used for assembly purposes all over the world due to its easy and unobstructed mounting.

SCARA Robots generally have what we know as serial architecture, where one base motor has to carry all the other installed motors. One of the downsides of these types of robots is that they are extremely expensive compared to conventional Cartesian robots. Also, they need high-level and complex software to operate.

4. Parallel robots

Stewart's platform

Parallel robots are more commonly known as Parallel manipulator, in which a bunch of machine-controlled robotic chains supports the end effector (or simply the end platform). One of the best examples of this type of robot is flight simulators, which military and commercial pilots use to enhance their flight abilities by simulating real-life situations.

The word ‘parallel’ should not be misunderstood as it’s not implying a geometric setting but rather a unique characteristic of the robot type in computer science. Here parallel means that the endpoint of each individual linkage is completely different from others.

The parallel robot is specially designed to remain rigid and resist all unwanted disturbances and movements, which is contrary to serial manipulator robots. Even though each actuator works with a degree of freedom, its flexibility is eventually constrained by the other actuators. Its rigidity and stiffness separate parallel manipulators from serial chain robots.

5. Articulated robots

articulated robots

When someone talks about industrial robots, there is a good chance that they are referring to articulated robots. These robots are extremely versatile and well-suited for industrial work, unlike most other types of robots we showed above. This agility and versatility come from their extra axes, which are generally four to six but can also reach as high as 10. Their major applications are material handling, dispensing, and welding.

6. Spherical robots

spherical robotImage Courtesy: Seelio.com

Based on the level of sophistication, spherical robots stand somewhere between Cartesian or cylindrical robots and ultra-sophisticated articulated robots. Basically, a spherical robot is a mid-sized robot inside a spherical ball, which moves with the help of an IDU (Internal Driving Unit). These mobile spherical robots are extremely efficient in surveillance and monitoring missions and can also be used underwater.

Wheeled and Legged Robots

7. Single Wheel Robots

We all have ridden a bicycle or motorcycle at least once, but how many of you have actually ridden a unicycle? Well, I tried it once; I couldn’t even get seated properly. The problem is that unicycles are not stable like bicycles, so it’s difficult to balance, and one would fall instantly without proper support.

Making a single-wheeled robot poses a difficult challenge for engineers as they have to make it dynamically stable as well as efficient. One such example of a single-wheel robot is MURATA GIRL.

Murata girl, or Murata Seiko-chan, is a unicycle robot manufactured by the Japanese electronics company Murata. According to the company, she has advanced gyro sensors that allow her to maintain balance, a Bluetooth device for communication, and an ultrasonic sensor for target detection. These types of compact robots can come in handy in crowded areas.

8. Two-Wheel Robots

two wheeled robotImage Courtesy: David P. Anderson 

Do you want to make your own robots? If yes, then small two-wheel robots are perhaps the right way for you to start. Their simple and effective design is the reason why two-wheeled robots are prevalent nowadays. All you need is a couple of motors and two wheels to move around.

But like any other robot, they also have their own flaws. Two-wheeled robots have poor balance since they use just two wheels on either side, and they always have to be in motion to maintain an upright position. To make it more stable, batteries are mounted directly below their bodies.

9. Three Wheel Robots

three wheel robots

Three-wheel robots can be divided into two types based on the nature of steered wheels. In the first type, two wheels are separately powered while the third wheel rotates freely for balance (differentially steered). In the second type, two wheels are powered by one source, while the third wheel is powered by another source.

For differentially steered three-wheel robots, the direction in which the robot is going at a given time can be altered by changing the relative rate at which the two powered wheels are rotating. When two wheels have the same rate of rotation and the same direction, the robot continues to go straight.

10. Humanoid Robots

humainoid robotTOPIO, a humanoid robot, played T.T at IREX, Tokio

As the name suggests, a humanoid robot is a type of robot that replicates the human body. The design of Humanoid robots is what makes them fairly distinct from the other types of mobile robots. A typical humanoid robot consists of a head, two arms, a torso, and two legs, just like a human.

They are designed to perform specific jobs, such as inspection and disaster response at power plants, routine tasks for astronauts in space travel, and personal assistance and caregiving.

Read: 12 Advanced Robotic Animals That Are Transforming Scientific Research

One of the main components of a humanoid robot is sensors, which play a pivotal role in robotic paradigms. There are two types of sensors: Proprioceptive and Exteroceptive sensors. The former is responsible for the robot’s orientation, position, and other motor skills, while the latter includes visionary and sound sensors.

11. Tripedal and Quadrupedal robots

Quadrupedal robotsBoston Dynamics’ WildCat

While tripedal or three-legged robots are not so common, a robotics and mechanism laboratory in Virginia has developed a radical three-legged robot named STriDER. It uses a fairly new concept of passive dynamic locomotion to walk in all directions. This highly efficient robot can also be guided with minimal control.

In contrast to tripedal robots, four-legged robots are more popular. The four-legged robots, also known as quadrupedal robots, have more stability, especially when they are not in motion. Many quadrupedal robots use the alternating technique (in pairs) to walk.

Some of the best examples of quadrupedal robots are WildCat, Cheetah, and Big Dog.

12. Hexapod Robots

hexa robots

In geometry, Hexagon implies a six-sided polygon, so a hexapod would mean a robot with six legs, right? Yes, that is the case here. Although a robot can be perfectly stable on just three legs, the extra legs of a hexapod robot provide a great deal of flexibility and increase its capabilities.

Many, if not all, hexapod designs are inspired by the locomotion of Hexapoda (Greek for 6-legged) family of insects. They are also used to test various biological theories about insect locomotion and motor control. These hexapods utilize various types of gaits to make a move. The most common are:

  • Alternating tripod: Out of possible six, only three legs stay on the ground at a time
  • Crawl: only one leg stays on the ground at a time, giving the impression of crawling

13. Hybrid Robot

We had robots with legs and robots with wheels, but Boston Dynamics, a robotics company, launched a research robot named Handle, which can stand tall up to 6.5 feet and travel short distances at a speed of 9 mph. It can also jump vertically up to 4 ft.

Although it has all the basic working principles found in a quadruped robot (like balance and mobile manipulation), it only uses ten actuated joints. Therefore, it’s far simpler than other walking robots. With wheels (efficient on flat turfs) and legs (efficient for rough terrain), ‘Handle’ can actually handle anything thrown at him.

14. Flying Robots

flying robotImage Courtesy: Ted Talks

How badly were you waiting for this? I was eager to write this too.

Without a shadow of a doubt, flying robots are the most popular Robo types. Right now, some big multinational companies are planning to incorporate those automated flying machines into their day-to-day business. These robots aren’t just cool; they are also strong and aerodynamically sound.

In some areas, Amazon has started shipping products through flying drones. These fully electric and autonomous drones can fly up to 15 miles and deliver packages weighing 5 pounds in less than 30 minutes.

Read: 14 Unique Early Experimental Flying Planes

15. Swimming Robots

swimming robot

And why should flying robots get all the limelight; why not swimming robots? Yes, they are as cool as flying robots; the only difference is that instead of flying, they can swim. These robots can take the form of insects, fish, or big slithering snakes.

One such unique robot is NASA’s SWIM (short for Sensing With Independent Micro-Swimmers). It’s a smartphone-sized robot capable of swimming through oceans and descending through the icy shell of a distant moon in search of extraterrestrial life. It can cover larger water regions compared to a singular probe.

More To Know

What are the most common uses of humanoid robots?

In addition to personal assistance and caregiving, human-like robots are used as research tools in various scientific fields, including biomechanics and cognitive science. They are used to develop complex prosthetics for people with disabilities and personalized healthcare aids for the elderly.

In the entertainment industry, humanoid robots have served as stunt doubles. Some robots have been specifically built to simulate real-world, dynamic movement.

At present, these robots can perform certain tasks only and are far from autonomous. Many practical applications are still unexplored.

In the future, such robots (integrated with AI technology) could be useful for space exploration missions — we don’t have to bring them back to Earth once the mission is accomplished.

Who developed the first autonomous robots?

In 1948, British neurophysiologist William Grey Walter developed the first electronic autonomous robot with complex behavior. He named it Elmer.

Due to its structure and slow rate of movement, it was often called a three-wheeled tortoise robot. It was capable of finding its own path to a charging station when it ran low on battery power.

What are some of the most famous robots?
  • Spot: An agile mobile robot that can navigate the terrain with exceptional mobility.
  • Sophia: A humanoid robot that follows faces, makes eye contact, and recognizes individuals.
  • AIBO: A robotic dog that can recognize faces, respond to voice commands, and learn tricks via cloud computing.
  • Stretch: A commercial warehouse robot that can handle a variety of package types, sizes, and stacking configurations.
Robotics market size

According to a report published in Precedence Research, the global robotics technology market size will exceed $225.6 billion by 2030, growing at a CAGR of 12.3% from 2022 to 2030.

The major factor behind this growth includes the increasing demand for industrial robots that assist in material handling, manufacturing, welding, packaging and labeling, and security and inspection. Plus, the growing number of funding and investments in the field of robotics and machine learning is also driving this market across the globe.

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Written by
Varun Kumar

Varun Kumar is a professional science and technology journalist and a big fan of AI, machines, and space exploration. He received a Master's degree in computer science from GGSIPU University. To find out about his latest projects, feel free to directly email him at [email protected] 

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4 comments
  • This is great. I am researching on the types of robots that are used in the motor vehicle manufacturing companies. Am I right to say that most of them are stationary robots?

  • this site is so helpful i used this a lot on my project for school if you look at the commets then i say i reccomend this to you it will help you so much with work and or school if you like doning robotics or you are a robo engenier

  • dear sir im in market and looking for a robot who can put any sort of flat pack kit together . let me know when you programed one.