13-06-2012, 01:14 PM
Seminar on Fundamentals of Robotics
Fundamentals of Robotics.pdf (Size: 977.04 KB / Downloads: 370)
Overview
Even the most complex robotic system can be broken down into a few
basic components, which provide an overview of how a robot works. These
components are covered in this chapter, with more detail provided in later
chapters. Freedom of motion and the resulting shape of the robot’s work
area are also addressed in this chapter.
Parts of a Robot
Robots come in many shapes and sizes. The industrial robots illustrated
in Figure 2-1 resemble an inverted human arm mounted on a base. Robots
consist of a number of components, Figure 2-2, that work together: the
controller, the manipulator, an end effector, a power supply, and a means
for programming. The relationship among these five components is illustrated
in Figure 2-3.
Controller
The controller is the part of a robot that coordinates all movements of
the mechanical system, Figure 2-4. It also receives input from the immediate
environment through various sensors. The heart of the robot’s controller is
generally a microprocessor linked to input/output and monitoring devices.
The commands issued by the controller activate the motion control mechanism,
consisting of various controllers, amplifiers, and actuators. An
actuator is a motor or valve that converts power into robot movement. This
movement is initiated by a series of instructions, called a program, stored
in the controller’s memory.
The controller has three levels of hierarchical control. Hierarchical control
assigns levels of organization to the controllers within a robotic system. Each
level sends control signals to the level below and feedback signals to the level
above. The levels become more elemental as they progress toward the actuator.
Each level is dependent on the level above it for instructions, Figure 2-5.
Special Configurations
Many industrial robots use combinations or special modifications of
the four basic configurations. The robot pictured in Figure 2-39A uses an
articulated configuration, but its base does not rotate horizontally. It is
designed to literally bend over backwards in order to grasp objects behind
it. This feature makes it possible to install these robots very close to other
equipment, which minimizes space requirements, while maintaining
a large, effective work envelope, Figure 2-39B. These robots are used in
applications such as spot welding and material handling.