What are Robots?

Robots are programmable machines with some human like capabilities. These are automation systems made up of mechanical components, a control system and a computer. These elements can be arranged in different ways and varied in size and complexity to perform different tasks. Robots are available in a variety of types which vary in their mechanical configuration, freedom of motion and drive and control systems. The motion ability of a robot is determined by the degrees of freedom and working envelope provided by its geometric configuration. There are a number of different types of drive systems; each has its own advantages in cost and performance capabilities. No one drive system is best for all applications. Robot specifications must be matched to the needs of a particular application in order to select a type which will perform the required tasks.

Robotic systems have a number of economic and performance advantages over human labour or hard automation in many applications. This is particularly true for those applications involving batch manufacturing operations. The major advantages are due to their programmability. Robots can be programmed by several different techniques, some of which do not require the experience of professional programmers. A robot control performs a lot of tasks at high speed.

Definition of Robot

Many formal definitions have been developed to distinguish robots from other forms of automation. In general robots can be defined as "Programmable and Automatic Manipulators". It is a special type of computer-controlled machine that can perform a wide variety of tasks by using rational humanlike capabilities. Two definitions which have been adopted by industry are quoted here. The first is by Computer Aided Manufacturing-International (CAM-I), USA. It states that a robot is "a device that performs functions ordinarily ascribed to human beings, or operates with what appears to be almost human intelligence.”

The second definition by Robotics Institute of America (RIA), USA. RIA defines a robot as a "programmable, multifunction manipulator designed to move materials, parts, tools, or special devices through variable programmed motions for the performance of a variety of tasks."

Types of Robots

Industrial robots are made in a variety of shapes and sizes, but they can be classified by a few basic characteristics features, these are as follows:.

(a) The physical geometry of the manipulator arm and base unit.

(b) Degrees of freedom (Number of degrees of motion)

(c) The complexity of the path in which the manipulator can move.

(d) The type of power source used to move the manipulator

 (e)         The techniques and system used to control the motion of the manipulator

Adaptive Control

Adaptive control is the ability to modify a program in real time, based upon sensory data. Robots can make use of abilities such as familiarizing parts based on features, following a changed path, or recognizing work pieces. Adaptive control requires sensory input and the ability to respond to that input.

Robot Operation

Four basic modes of operation can be used to control the movements of a robot. These are as follows:

(a) Pick-and-Place. As the name implies, this mode involves a very limited sequence of moves to a fixed position where it grasps a part ("pick"),then moves to another position where it "places" the part. The pick- and-place mode can be accurate and capable of high speed.

(b) Point-to-Point. This is used for more complex movements where the arm is controlled in a series of steps that have been stored in memory. Each axis operates at its maximum rate until it reaches the desired endpoint position. Applications like spot welding are examples of point to point operations.

(c) Continuous Path. This mode is required when the control of the manipulator's path is critical, such as in a spray-painting application. The robot's path is not determined by a series of pre-programmed points. The path and movement of each axis is stored during a walk through programming session. Although this creates a continuous path, it is not precise. All the movements of the operator, intended are not are recorded. A large amount of memory and a high-speed sampling system are needed to record all the path data.

(d) Controlled Path. Where the total control of the robot's motion, as in an arc welding, is desired a detailed control program and sophisticated servo- control system must be used. This provides coordinated control of all the axes in terms of their position, velocity, and acceleration. The program can optimize the movements of the manipulator to reduce cycle time, minimize forces, eliminate jerky motions, and improve precision. Sensors provide the necessary feedback to control the process. For example vision sensors provide feedback of progress of a robotic welding operation.