A Simple Explanation of How Do Robots Work

How Do Robots Work?
Robots, machines that can perform human tasks, have always interested tech-enthusiasts and the general public alike. Right from wired to humanoid robots, the basics of operation and design principles remain the same. Get to know the exact working of a robot in this Techspirited post.
Techspirited Staff
Last Updated: Mar 26, 2018
Did You Know?
Unimate, was the first digital and programmable robot, which was invented by George Devol in 1954.
Robots can be loosely defined as electro-mechanical devices that are actuated by certain input agents like sensors or transducers and are guided to work by computer circuitry. The robot definition sounds complicated, but the working of the machine itself isn't so tough to understand. Pretty much like we humans receive inputs from our sensory organs, process them in our brain, and carry out the desired action; robots too have the same building blocks. The inputs to the robots is via sensors, the processing is done by the CPU unit, and then the desired output is obtained.

Before knowing about the working of different types of robots, let us first take a look at the basic working of a robot.
Working of a Robot Explained
working robot
Any robot is made up of three parts - Sensors (for input), CPU (processor), and Mechanical Actions (for output). The sensory inputs that the robot takes can be anything from smell, touch, visual differences, etc. The central processing unit is the microprocessor or microcontroller that processes this input quantity, searches for the corresponding function to perform from the previously-fed or programmed instruction set, and then sends the signal on to the output port. Upon reception of this signal, the robot will perform the desired action. Let us take an example of a robot that will stop once it comes in contact with any obstacle.

Robot: Obstacle Avoider
Input: Touch
Output: Stop the motors
Purpose: In this example, the robot is to move freely in any direction, and stop once it collides with any object.

Once the robot comes in contact with any object, its input sensor (touch) will be activated. This sensor will send signal to the processing unit, as soon as it turns on. The CPU will look up in its instruction set to find the relevant action to be performed upon the reception of this signal. The instruction here is nothing but the program that is fed to the robot. As the desired function is to stop the robot's movement, the CPU will send a 'Stop' signal to the output module (motor's circuit). Thus, the robot will stop moving.
Commonly Used Components
Though the selection of components is done according to the application, a few most commonly used ones are mentioned below.
Input Unit
The input to the robot will be via sensors and transducers. The various sensors used in robotics are:
  • Contact/touch sensors
  • Temperature sensors
  • Light sensors
  • Sound sensor
  • Proximity sensor
  • Distance sensor
  • Pressure sensor,etc.

Based on the type of the sensor output, digital or analog, the further circuitry is decided.
Processing unit
As far as the processing unit is concerned, a microcontroller or microprocessor can be used. This choice will depend on the driving load. A microcontroller is cheap and is easy to program than a microprocessor. However, a microcontroller has very low output power, and so cannot drive large loads. On the other hand, its PC counterpart, the microprocessor can drive large loads at its output. The complexity of the operations being performed by the robot will depend on its processing unit.
Output unit
The output unit of the robot will vary according to its driving load. The most common output units are:
  • Actuator
  • Relays
  • Speakers
  • CD screens, etc.
Based on the applications the carrier changes. For wired applications, cables and wires are used while for wireless robots RF, RFID, Wi-Fi, DTMF, etc., technologies are used.

Now let us see the working of two basic types of robots―wired and wireless robots.
Working of Wired Robot
wired robot
wired robot
As the name suggests, these robots are operated by wired devices. The input here is a keyboard, joystick, or switches. When a particular key is pressed, it sends a particular voltage signal to the next circuitry. If the input device is analog in nature, its output will be voltage signal, and if the signal is digital in nature, its output is in the binary form of 1's and 0's. This signal is read by the encoder circuit which encodes the signal into a format that is recognized by the transmission medium. The encoder circuit gives serial output which is fed to the transmission medium i.e. wire/cable. This encoded signal is received at the decoder circuitry which decodes the signal to a format that is understood by the output device. Let us see the detailed working of wired robot through the following example.

Robot: Robotic Car
Input: Switch
Output: Turn motors in clockwise direction
Purpose: To propel the robotic car in the forward direction

In the robotic car that you wish to move in different directions, the input device will be a keyboard which will have four switches, one for each direction. If you want to move the robot in the forward direction, the relevant switch is pressed. The pressure of the key pressed will provide output voltage signal to the encoder circuitry, whereas the other keys will provide output 0 voltage signal. So, ideally, the parallel output from the keyboard will be 1 0 0 0 (Forward, Backward, Right, Left). This parallel output will be fed as parallel input to the encoder circuit, say HT12E. This encoder IC is the most commonly used circuit in robotics. This parallel input is converted to serial output by the encoder, and fed to the connecting wire. The wire will transmit these signals to the decoder circuit. Here, the decoder HT12D will convert this serial output to parallel output. This parallel output is fed to the DC motors via the motor driver IC L293D. The logic 01 will rotate the motors in clockwise direction which will move the robotic car in the forward direction.
Working of Wireless Robot
wireless robot
wireless robot
Wireless technology is used in most robots today, from autonomous to humanoid robots. The working of the wireless robot is similar to the wired robot, except for the change in the carrier circuitry. The wireless technology comes in transmitter-receiver pair. For transmitting the output signals over the wireless medium, a suitable frequency is chosen. Depending on the transmitting frequency, the transmitter and receiver antennas are chosen. The quality of signal transmitted depends on the efficiency of these antennas. Let us study the detailed working of wireless robot with the example of a robotic car.

Robot: RF controlled robotic car
Input: Switch
Output: Turn motors in clockwise direction and turn on LED
Purpose: To move the robotic car in the forward direction

Similar to the working of wired robots, the wireless robots will have an input module that will provide parallel output signal depending on the corresponding key that is pressed. This parallel output is converted into serial form by the encoder circuitry. This serial data is fed to the RF transmitter circuit which performs modulation on the amplitude of the input wave. This amplitude variation is known as Amplitude Shift Keying (ASK). The RF transmitter sends this ASK signal through its antenna. This data is generally sent on 433 MHz (free frequency band) at a rate of 1 Kbps-10 Kbps. This data is received by the receiver antenna, and sent to the RF receiver circuit. This data is converted into serial output by the receiver, and fed to CPU unit. The CPU unit can be either a microcontroller or a microprocessor. The decoding of the serial input signals is done by the processing unit. It will send this data to the relevant pins, which will, in turn, send parallel output signals to the motor driver circuitry. The motor driver will turn the motors in the relevant direction, in order to move the robotic car wheels. The CPU is used in this case to drive more than one output device. Along with motors, the CPU can switch on and off the LED, or can trigger a buzzer. The selection of the various components needs to be done considering the losses and interference effects. RF is the most preferred wireless medium because it can travel long distances, and is not line-of-sight technology. Complex robots are all built on this simple principle of wired and wireless robots.