A robot is an electro-mechanical device controlled by an electronic circuit or any software tool. It can replace humans in performing tasks in dangerous and extreme environments. A typical robot consists of the following basic elements:
- Movable structure made up of limbs and wheels connected by joints.
- Sensors for gathering data about the surroundings.
- Actuator that can be enabled using a pneumatic system, a hydraulic system or an electric motor.
- Power supplies for triggering the actuators.
- Electrical circuit for controlling motor and hydraulic and pneumatic systems.
- Reprogrammable circuit for controlling all the components.
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Robots are essentially machines that imitate animal and human behaviors. This article discusses all of the components required for building a robot, and their functions.
Essential Parts of Robots
The following are the major components of robots:
Pin project board – PICAXE-28X1
A breadboard is a basic element required to form robotic circuits. PICAXE-28X1 is an 18-pin microcontroller board that is available in two forms - high-power and standard. The standard configuration provides eight digital outputs of 800 mA each, by using a darlington driver integrated circuit. The high-power configuration provides four digital outputs of 1.5A each by employing four field-effect transistors. This board can be operated using a power supply of 3 - 5V. Output and input devices can be connected to the pins on the board.
The jumper leads are essentially extension cables that can be used when the servo wire has to be extended. These cables are available in different sizes and configurations – male to male, male to female and female to female.
Motor drivers are used to control the direction and speed of the motors. Robots can be made up of AC or DC motors. A typical drive control system of the robot includes an AC/DC motor and a drive controller for regulating the speed of the motor.
DC motors are mainly of four types as follows:
- Shunt-wound motors that exhibit simple reverse control and flat speed-torque properties
- Series wound motors that have high initial torque, but poor speed control characteristics
- Compound wound motors that have stable speed and excellent initial torque
- Permanent magnet motors with good speed control and starting torque.
AC motors, on the other hand, are further classified into induction and synchronous motors. Induction motors are the common type of electric motors used in industries. Synchronous motors are used for operations that are carried out at synchronous speed.
Infrared sensors are widely used in mobile robots for distance measurement, and obstacle detection and avoidance. They are operated based on the reflection of infrared light after hitting an obstacle. According to Benet G et al (2002), these sensors have a fast non-linear response which enhances the real-time operation of mobile robot.
Grove Infrared Receiver developed by Trossen Robotics is an excellent option for the integration of remote communication technology into mobile robots. It is capable of detecting infrared signals at a frequency of 35 kHz within a 10 m detection limit.
Gear Motors and Wheels
The usage of gear motors with wheels in mobile robots helps to achieve a desirable speed to torque ratio. A shift in rotational torque and velocity can be achieved by changing the diameters of the gears used.
GM10 gear motor developed by Solarbotics is one of the commercially available gear motor that rotates at a speed of 370 rpm. It features two traction bands, a motor and a wheel. With a wheel diameter of 25 mm, the gear motor can drive the robot at a rate of 15 cm/s.