MECHANICAL THEORY Thermal Engineering

Robot Classification-Robot Components, Vision Sensing, RCU,SCU etc.

Robot Classification-Robot Components, Vision Sensing, RCU,SCU etc: Robot is derived from the Czech word ‘robota’ which means slave labour was invented by Karel Capek in 1917. Asimov (1970) in his three laws of robotics explained robots as harmless and were in the control of humans.These are invented in order to replace humans where there is a value for human life i.e. in wars,fire fighting etc. Therefore, In this article, I will be listing all the concepts of robotics in a detailed way.

  • Definition of robot
  • Components of robot
  • Classification of Robots
  • Types of sensors used in robotics
  • Applications of robots
  • Classification of robots etc.

The explanation of each is as follows…

Definition of Robot:

  • Definition of robot: The Robot is defined as A “re-programmable, multi-functional manipulator designed to move parts,materials, tools or specialized devices through various programmed motions for the performance of a variety of tasks”.
  • The study of Robots is called robotics.

Components of robot:

The basic components of a Robot are

  1. Manipulator
  2. Power Supply
  3. Robot control unit (Control System)
  4. Sensor control unit

These components  may be assembled as one integral unit or separated into individual components which are connected by hydraulic,pneumatic or electrical source.

The explanation of above components is as follows…

1.Manipulator:

  • The manipulator is an assembly of various axes which is capable of providing motion in various directions.
  • The manipulator essentially consists of Base, Shoulder swivel,Elbow extension and wrist. [Understanding Purpose:Considering manipulator as a human being then legs of human is nothing but the base of manipulator, Shoulder swivel,Elbow extension and wrist are similar to humans.]
  • The “wrist ” located at the end of the robot arm has 1 to 3 DOF (Degree of Freedom), depending on the model made.
  • The wrist of the robot has 3 degrees of freedom i.e.  pitch, yaw, and roll axes which were shown in the figure of manipulator.
  • The manipulator is powered by pneumatic cylinders or hydraulic cylinders or hydraulic motors to power the various axes of motion.
  • Feedback devices are used to measure the position and velocity of various axes of motion and send this information to the control systems for use in coordinating the robot motions.
  • The duty of Feedback devices is to send the feedback to the Robot controller taken from the work region.The Robot controller will check the (actual amount of work to be done) to the (work has done on the workpiece) and calculate the difference. This difference is again given to the manipulator to do the remaining work.

 

2.Power Supply:

  • The power supply is the source of energy used to regulate the robot’s drive mechanisms. 
  • The energy comes from three sources are Electric, Hydraulic and Pneumatic.
  • Electric drives  has a high degree of accuracy and repeatability. 
  • They also offer a wide range of payload capacity, accompanied by an equally wide range of costs.

  • Hydraulic drives, are most popular now-a-days and has high payload capacities which are relatively easy to maintain.
  • They are however, rather expensive and not as accurate as either the electric or pneumatic drives.

  • Pneumatic drives, although limited to smaller payloads, are relatively inexpensive but they are fast and reliable.

3.Robot Control system (RCS):

  • The Robot Control system acts as the brain of the robot. It coordinates and sequences the motion of the various axes of the robot and provides communication with external devices and machines.
  • Programmes may be written in AML (A Manufacturing Language), which is a high-level language developed specifically for industrial robot applications.
  • The operator interacts with the RCS(Robot Control system) through a standard video terminal.
  • The terminal is used to create and edit programmes, enter robotic commands and execute programmes, and generate data points during the robot training phase.
manipulator
manipulator

The sensors used in this system are vision sensor, Prismatic sensor etc.

Vision Sensing:

Adaptive control for robots may be defined as the modification in it’s behavior such that it will adjust to the changes in it’s working environment.

The main advantage of adaptive control lies in its Flexibility, the ability to change the control programme easily to a new function or adjust to new parts as the need arises.

The two components that provide the Adaptive control are

1.Robot Control Unit(RCU)

2.Sensor Control Unit (SCU)

The Robot controlled unit was already discussed…Now let’s discuss Sensor Control Unit (SCU).

4.Sensor Control Unit (SCU):

The Sensor Control Unit (SCU) provides visual information about the scene to be analyzed. It takes the information about the performance of each camera ,analysis the image and transposes that information to the robot’s coordinate system.

An image of an object comes through the camera lens and falls on an image plane inside the camera.

The most useful camera for machine vision is the solid-state matrix array camera, which was designed for military space use.

sensor control unit
sensor control unit

 

This camera consists of grid light-sensitive elements called pixels or picture elements.The information from this grid is acquired by scanning rapidly the entire field, line by line.

The varying light intensities associated with each pixel are then translated into varying voltage levels and transmit to the interface electronics.

Adaptive control of a robot eliminates the need for accurate fixturing of work pieces, precise fabrication tolerances of equipment and accurate teaching of the coordinate data.

The 3D coordinate information is analyzed by the Sensor Control Unit (SCU) and sent it to the RCU (Robot Control Unit) so that action can be taken by the control unit and deliver it to the manipulator.

Robot Classification:

Robots are classified based on work envelope:

  1. Rectangular Coordinate (Cartesian) Robot
  2. Cylindrical Coordinate Robot
  3. Spherical Coordinate Robot
  4. Jointed Spherical Robot
  5. SCARA

Robots are classified based on Functionality:

  1. Non servo point to point and 
  2. Servo Controlled (point to point and continuous-path).

Explanation of Robot classification:

1.Rectangular Coordinate (Cartesian) Robot

Rectangular Coordinate (Cartesian) Robot
Rectangular Coordinate (Cartesian) Robot

Robots with Rectangular Arm Geometry use cartesian coordinates and move linearly along each of the X,Y & Z axes. This type of movement is also called as 3P Geometry.

Where, P-Prismatic or linear motion

This type of geometry is most commonly used with Pick and Place for a large overhead mounted robots.

Rectangular arm geometry robots can only move linearly in each direction.

Ex:An Overhead crane robot is the best example for this type of motion.

It can move forward and backward, Left and Right, Up and Down directions and are generally used in Material handling systems.

Work Envelope:Robotic arms that use cartesian coordinates geometry generate a rectangular work envelope 

The remaining classification will be updated soon

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