Mechanical Structure

The robot structure consists basically of the robot body that includes arms and wheels. Some force such as electricity is required to make the arms and wheels turn under command. One of the most interesting aspects of robot in general is its behavior, which requires a form of intelligence.

 

Motors

A variety of electric motors provide power to robots, making them move with various programmed motions. The efficiency rating of a motor describes how much of the electricity consumed is converted to mechanical energy.

 

DC motors. Permanent-magnet DC motors require only two leads, and use an arrangement of fixed- and electro-magnets (stator and rotor) and switches. These form a commutator to create motion through a spinning magnetic field.

 

AC motors. These motors cycle the power at the input-leads, to continuously move the field.

 

Stepping motors. They are like a brushless DC or AC motor. They move the rotor by applying power to different magnets in the motor in sequence (stepped). Stepping motors are designed for fine control and will not only spin on command, but can spin at any number of steps-per-second (up to their maximum speed).

 

Servomotors. Servos are simple DC motors with gearing and a feedback control system. They adjust themselves until they match the signal. Servos are used in radio control airplanes and cars.

More About Motors

 

Mechanisms

Gears and chains. Gears and chains are mechanical parts that provide a mechanism to transmit rotational motion from one place to another with a possibly of changing it along the way. The speed change between two gears depends on the number of teeth on each gear.

 

Pulleys and belts. Pulleys and belts, two other simple machines used in robots, work the same way as gears and chains. Pulleys are wheels with a groove around the edge, and belts are the rubber loops that fit in that groove.

 

Gearboxes. A gearbox operates on the same principles as the gear and chain, without the chain.  Examples of gearboxes are found on the transmission in a car and the paper-feed of a printer.

 

 

Sensors

Robots operate according to a basic measurement, requiring different kinds of sensors. A sense of time is usually built-in through perceptual hardware and software, which updates quickly. Sensors interact with external environment and transforms the energy associated with what is being measured (sound, light, pressure, temperature, etc.) into another form of energy. Common sensors used in robotics include light sensors, touch sensors, sound sensors, and acceleration sensor.

A sound sensor is installed at the ear position of the robot in order to detect the voice of a subject. An acceleration sensor is installed in the body to detect shaking. A touch sensor is installed in the forehead of the robot to detect touch

 

 

Power Supply

In general, power supply is provided by two types of sources: batteries that are used once only and then discarded; and rechargeable batteries that operate from a reversible chemical reaction and can be recharged thousand times. The first use of a rechargeable battery gives up to 4 hours of continuous operation in an application.

 

Control System

There are two main systems to control robots: logic circuit and a microcontroller.

 

Logic Circuit

A digital logic circuit controls the mechanical system. The circuit is usually coupled to the mechanical structure through a bridge relay. A control signal generates a magnetic field in the relay's coil that mechanically closes a switch. transistors, for example, are good silicon switches, available in many technologies to control the mechanical systems.

 

Microcontroller

Microcontrollers are intelligent electronic devices that are used inside robots. They deliver functions similar to those performed by a microprocessor (CPU) inside a personal computer. Microcontrollers are slower and have less memory than CPUs, but are designed for real-world control problems. One of the major differences between CPUs and microcontrollers is the number of external components needed to operate them. Microcontrollers may run with no external parts, and typically need only an external crystal or oscillator.

There are three main characteristics of a microcontroller for consideration: speed, size, and memory. Speed is designated in clock cycles, and is usually measured in millions of cycles per second (Megahertz, MHz). Size specifies the number of bits of information the Microcontroller can process in one step (for example, 4-, 8-, 16-, and 32-bits). Microcontrollers count most of their read-only memory (ROM) in thousands of bytes (kB) and random access memory (RAM) in single bytes.