Types of Robots
Configurations of Robots
The configuration or coordinate systems of robot for the manipulation of arm may be many but following are more commonly adopted.
(i) Cartesian coordinate system
(ii)Spherical (or polar) coordinate system
(iii) Cylindrical coordinate system
(iv) Revolute coordinate or jointed-arm configuration system
Types of Robots
Industrial robots may be of two following types:
- General purpose robot
- Spherical purpose robot
General purpose robots may carry standard designs and parts and are available readily. These robots can be adopted easily to the user’s need by adding suitable end effectors or fingers. They are used for performing operations such as welding, spray painting and part pickling. They are cheaper also because the use of readily available standard components. Special purpose robots are tailor-made to satisfy the needs of a specific job. They are specially designed according to the needs and turnout to be costlier also.
Motion System of Robot
It is about the methods adopted by a robot for reaching from one location to another. (i) Point to point system (POP) is mostly used for robots employed for loading and unloading, pick and place, etc. In this system, only the movement of the robot from one point to another is controlled with no regard to the path followed by it in doing so.
(ii) Continuous path or contouring system compels the robot to follow a predetermined path in reaching from one point to another. This needs for the robot to have higher levels of memory and controls. Robots engaged in welding, spraying, etc. use this system of movement.
Some Terms Related to Robot
- Work envelope or work volume of a robot represents the volume space around the manipulator arm within which it can operate. It differs from robot to robot
- Speed of movement is the speed at which a robot is capable of manipulating its end effector. Heavy parts and higher placement accuracy demand slower movements.
- Load carrying capacity of a robot varies according to its structure.
- Precision of movements is defined as the degree of precision with which a robot is capable of moving the end points of the wrist of its manipulator arm.
Energy to operate robots may be received through electric drives, hydraulic drives and pneumatic drives. Hydraulic drive is most popular.
A human being possesses a number of intelligence characteristics such as capacity to leam, understand and interpret a language and capacity to analyze reason and solve problems. Humans possess many other intelligence features such as sensing heat and cold, distinguishing colours, recognizing shapes and colours, etc. All this has been possible by synchronizing the brain intelligence with many human traits like touch, vision, sensing, etc.
Efforts had been made to impart as many intelligence characteristics to the robot as possible so that it could perform its task more and more intelligently. However, it has not been possible so far to impart all the human intelligence characteristics to robots or any other automated machine. Efforts are on, however, to impart more and more intelligence characteristics to robot. These characteristics, when imparted to machines, are called artificial intelligence (AI) of the machine concerned.
Robot Programming and Languages
For programming the work cycle of a robot, the following four methods are used:
- Manual programming method
- Walk through programming method
- Teach pendant method
- Off-line programming method
1. Manual programming method is used for simple robots with shorter work cycle. Controlling components of robot such as cams, stops, relays and switch are set through this method. Robots engaged on jobs like pick and place, loading and unloading, etc. use this method of programming.
2. Walk through programming method suits well for robots used in welding, spray painting. etc. Programme is not concerned at all about the cycle time, which is controlled independently. The hands and arms of the robot are initially moved manually and these movements are stored in computer memory for being followed during further operations.
3. Teach pendant method or lead through method uses, Teach pendant which is a small control device held in hand and is used to switch on power drives for various robot movements in predetermined sequence of motions. In this method also, the initial robot motions are recorded in a computer memory and played back during further operations.
4. Off-line programming method: This type of programme is separately prepared and fed into the computer memory. It is then readily available for use whenever the operation is to be performed. Programming languages: Some commonly used computer languages used for programming. for robot include the following.
(vi) MCL and
Robot Sensing and Sensors
In order to bring robot’s operations nearer to that of human beings, efforts were being made for improving its sensing abilities, i.e. vision, hearing and feeling by touching other objects. These objectives are achieved by using different types of sensors which may be digital type, analog type, contact type, visual type, etc. Internal state sensors include devices such as linear inductive scales, resolvers, potentiometers, LVDTS, RVDTS, optical encoders, etc. These are used for measuring position, velocity, acceleration of end effector or joints. of Yet another class of sensors, external state sensors, help in determining the robot. the relationship of the robot with its environment and objects handled by it and these include proximity devices, strain gauges, electromagnetic sensors, pressure transducers, etc. These help in sensing force, torque, obstruction, distance from an object, touch, etc. Visual external state sensors include video camera with programmed computer and a light source to sense the presence, position and orientation of an object in the line of its vision within its work volume.
Robots vs NC Machines
There are a number of similarities and dissimilarities in features and attributes of a robot and an NC machine. These are summarized in the following..
- Power technology used is similar in both.
- Similar feedback systems are used in both.
- There is a common trend of increased computer control.
- Some type of NC technology is used in robots for actuating robot arms as is used for operating NC machines. Many of the industrial applications are common.
- A robot is lighter and more portable..
- Programming of robot is different from part programming used in NC machines.
- Robot is used for more general applications such as welding, spraying, material handling, etc., whereas an NC machine tool finds use in metal machining only
Applications of Robots
- Use of a robot for industrial applications can be justified only under the following conditions if economically viable also.
- Working conditions are dangerous and potentially hazardous to health.
- Work cycle is repetitive in nature maintaining the same sequence.
- Work may be heavy, awkward or difficult to handle by the human beings. Process of manufacturing is continuous type requiring a large force of labour to work in shifts, one after the other.
Industrial robot finds applications in the following fields:
- Welding: Generally spot welding and arc welding in automobile industry.
- Spray painting of automobile bodies and other appliances.
- Loading and unloading of components in CNC machines, forging presses, transfer machines, stamping and punch presses.
- Material handling in shifting material from one place to another.
- Other processing operations such as wire brushing, riveting, heat-treatment, etc.
- Assembly operations in making an assembly of components using bolts, nuts and other means.
- Sorting of good components from one bin and placing the sorted out components into another bin.
- Inspection of parts: Robots are used for inspection of finished parts and assemblies, specially of electronic components and devices.
See More: Robotics:(Into and Main Parts)
See More: Transfer Machining:(Parts and Types)
See More: Mechanization and Automation