Classification of robots

Classification of robots

Before we plan to design and build a robot, we need to understand the purpose of a robot. Do not jump into conclusion that you need to build a complete and complicated robot in a day; they are complex, and at least for a beginner it is a terrifying thought. Read about the different types of robots available and start off with a simple design.
There are many different kinds of robots available, each created for different tasks and behavior, and works on different platforms. Robots can be built for entertainment, knowledge, competitions, domestic help, industrial uses, surveillance etc. Each of these robots can be classified as autonomous, controlled or semi-autonomous based on the way they are controlled.

Autonomous vs. Remote controlled robots

Autonomous robots
Autonomous robots as the name suggests, works autonomously. They have preprogrammed directions and are given a choice of taking decisions based on situations and surroundings. An Artificially intelligent robot can even learn certain behaviors and act accordingly (Artificial intelligence in itself is a very vast topic and the reason we will not delve into it now).
Autonomous robots can be as simple as an obstacle avoider, or as complex as an intellectual humanoid. However due to restrictions in power, size and intelligence these robots may not be good enough to perform complicated tasks.
Controlled Robots
These are robots that require human intervention to accomplish a task. They can either be wire controlled or remote controlled that are guided to perform any kind of complicated activities. A remote controlled robot can be programmed and guided to perform dangerous and complex tasks without being on the spot.
Semi-Autonomous robots
 These robots take the best of both worlds. The intelligence built in helps them perform simple tasks and take simple decisions. For complex tasks however, human intervention may be required. Generally the program is designed to take intelligent decisions on its own until any human input.
Virtual robots
There are also virtual robots which are computer programs designed to simulate a real robot. Robot Simulators, Chatbot, Web crawlers are all examples of virtual robots. Since they do not follow our robot definition, we will keep them out of this list for the time being.
Robots can be further classified, based on the way and the environment it is designed to work. Follow the links below to understand each of those classifications in detail.

1. Robot Locomotion
2. Land Based Robots
1. Wheeled Robots
2. Tracked Robots
3. Legged Robots
4. Wheeled-Legged & Hybrid Robots
3. Aquatic Robots
4. Flying Robots & Other Hybrid Robots

5.        

6.     Robot Locomotion

7.      Robots can be either mobile or stationary. Mobile robots include rolling robots, crawling robots, swimming robots and many more. Stationary robots include robot arm, robot face, industrial robots etc. Although known as stationary, these robots are not actually motionless, but are confined to a small boundary. Each of these robots are designed to work on different platforms and the most common ones work either on Land, Air, Water, space etc. Some of the robots are designed to work on more than one platform and can shift from land to water to air. Based on the way robots move, they can be further classified as "Holonomic" or "Non-Holonomic" drive Robots

8.     Holonomic and Non-Holonomic Drive

9.      Holonomic Drive

10.  Holonomic refers to the relationship between controllable and total degrees of freedom of a robot. If the controllable degree of freedom is equal to total degrees of freedom, then the robot is said to be Holonomic. A robot built on castor wheels or Omni-wheels is a good example of Holonomic drive as it can freely move in any direction and the controllable degrees of freedom is equal to total degrees of freedom. The image shows a castor wheel which can rotate in both X-axis and Y-axis making it move in both the directions.

11.  Non-Holonomic Drive

12.  If the controllable degree of freedom is less than the total degrees of freedom, then it is known as non-Holonomic drive. A car has three degrees of freedom; i.e. its position in two axes and its orientation. However, there are only two controllable degrees of freedom which are acceleration (or braking) and turning angle of steering wheel. This makes it difficult for the driver to turn the car in any direction (unless the car skids or slides).

13.  Redundant Drive

14.  What if the controllable degrees of freedom are more than the total degrees of freedom? Then the controls are considered to be redundant. A robot arm or even a human arm has only six degrees of freedom, but seven controllable degrees of freedom. (Try twisting and rotating your arm and find out what are the seven degrees of freedom, including shoulder, elbow and wrist).