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15 Different Types of Robots | Explained

[Estimated read time: 9 minutes]

AI and Robotics are undoubtedly two of the most promising fields of study right now. These two will certainly define the future of humanity. On one hand, we have ultra modern machines with sleek designs, agile and highly capable bodies, which are capable of doing almost any kind of work with efficiency, on the other hand, we have machine intelligence, which is literally revolutionizing the way we do our most of the work virtually.

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

Basically, robots are divided into two broad categories; first, based on their application and second based on kinematics or locomotion. But here we are only classifying robots based on kinematics. The reason you ask? Well, as many of you may already know that application of anything, especially a robot, vaguely describes its characteristics, as two different types of robots can perform a single type of job without any difference in the outcome.

Note: Based on kinematics, robots are subdivided further. Below we’ve only mentioned major robotic types.

Robotic Arms or Stationary Robots


1. Cartesian Robots

Cartesian robotImage Courtesy: Florian Schäffer/ An implemention 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 principally have three axes which are linear i.e, they can only move in straight lines rather than rotating and are mounted at right angles to each other. The mechanical arrangement of cartesian robots is far simpler than most of 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 movements. First the Z axes, where it rotates and move vertically and the Y axes, where it moves along in a linear motion. Sometimes these cylindrical robots are mistakenly regarded as SCARA robots or vice versa which is erroneous. 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 the assembly purposes all over the world due to its easy and unobstructed mounting.

SCARA Robots generally have what we know as the 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 rather inexpensive Cartesian robots and the fact that 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 robots is flight simulators, which are used by Military and commercial pilots to enhance their flight abilities by simulating real life situations.

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

The parallel robot are specially designed in a way that it may remain rigid and resist all the unwanted disturbances and movements, which is contrary to serial manipulator robots. Even though each actuator works with a degree of freedom, their flexibility is eventually constrained by the other actuators. It’s this rigidity and stiffness that 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 the industrial works unlike most of the other types of robots we discussed earlier. 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, welding etc.

6. Spherical robots

spherical robotImage Courtesy: Seelio.com

Based on the level of sophistication, spherical robots are somewhere in between Cartesian or cylindrical robots and those ultra sophisticated articulated robots. Basically, a spherical robot is a mid-sized robot inside a spherical ball, which moves with the help of 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 us have actually ridden a unicycle? Well! I will tell you that I tried it once, couldn’t even get seated properly. The problem is that unicycles are not stable like bicycles so it’s extremely difficult and one would fall instantly without proper support.

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

Murata girl or Murata Seiko-chan is a unicycle robot manufactured by Japanese electronics company Murata. According to the company, she has advanced gyro sensors which enable her to stabilize, a Bluetooth device for communication and an ultrasonic sensor for target detection. These types of compact robots can come handy in extremely 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 extremely popular 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 are using just two wheels on either side and always have to be in motion to maintain its upright position. To make it more stable, batteries from which they are powered are mounted directly below their bodies.

9. Three Wheel Robots

three wheel robots

Three wheel robots are generally of two types based on the nature of steered wheels. The first type is where two wheels are separately powered and the third is free rotating purely for balance (differentially steered), while the second type is where two wheels are powered by one source and a different source for the third wheel.

For differentialy steered three wheel robots, the direction at 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. In a case where two wheels have the same rate of rotation and same direction, it will continue 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, but many of those robots are only based on some part of the human body, like from waist up or something like that.

Read: 12 Advanced Robotic Animals That Are Transforming Scientific Research

One of the main components of a humanoid robot is sensors, as they play a pivotal role in robotic paradigms. There are two types of sensors Proprioceptive and Exteroceptive sensors. The proprioceptive sensors sense the robot’s orientation, position and other motor skills, while Exteroceptive includes visionary and sound sensors.

11. Tripedal and Quadrupedal robots

Quadrupedal robotsBoston Dynamics’ WildCat

Tripedal or three-legged robots are not so common, however, 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 dynamically and be highly efficient, which can also be guided with minimal control.

In contrast to tripedal robots, four legged robots are more popular. The four legged robots, which are 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 to a six sided polygon, so a hexapod would mean a robot with six legs right? Yes, that is the case here. Now since, a robot can be perfectly stable on just three legs, the remaining legs of a hexapod robot provide a great deal of flexibility and increases its capabilities.

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

  • Alternating tripod: Out of possible six, only 3 at the ground at a time, and
  • Crawl: only one leg 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 both stand tall up to 6.5 feet and travel in 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, i.e., balance and mobile manipulation, it only uses 10 actuated joints, so it’s far simpler than other walking robots. With wheels, efficient on flat turfs and legs on a rather 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? To say the truth, I was eager to write this too. Without a shadow of a doubt, flying robots are the most popular robo types, now whether it’s among youngsters or old timers. Not only that, right now some big multinational companies are also 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.

Read: 14 Unique Early Experimental Flying Planes

15. Swimming Robots

swimming robot

And why flying robots get all the limelight, why not the swimming robots. Yes, they are as cool as the 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 snake you just name it.

One comment

  1. Kegesa Danvas Abdullah

    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?

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