中文2840字外文资料INDYSTIAL ROBOTSThere are a variety of definitions of the term robot.Depending on the definitino used,the number of robot installatinos wordwide varies widely.Numerous single-purpose machines are used in manufacturing plants that might appear to be robots.These machines are hardwired to perform a single function and cannot be reprogrammed to perform a different function.Such single-purpose machines do not fit the definition for industrial robots that is becoming widely accepted.This definition was developed by the Robot Institute of America.A robot is a reprogrammable multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.Note that this definition contains the words reprogrammable and multifunctional.It is these two characteristics that separate the true industrial robot form the various single-purpose machines used in modern manufacturing firms.The term “reprogrammable” implies two things: The robot operates according to a written program,and this program can be rewriten to accommodate a variety of manufacturning tasks.The term “multifunctional” means that the robot can, through reprogramming and the use of different end-dffectors, perform a number of different manufacturing tasks.Definitions written around these two critical characteristics are becoming the accepted definitions among manufacturing professioals.The first articulated arm came about in 1951 and was used by the U.S.Atomic Energy Commission.In 1945,the first programmable robot was designed by George Devol.It was based on two important technologies:(1) Numerical control (NC) technology.(2) Remote manipulation technology.Numerical control technology provided a form of machine control ideally suited to robots.It allowed for the control of motion by stored programs.These programs contain data points to which the robot sequentially moves, timing signals to initiste action and to stop movement, and logic statements to allow for decision making.Remote manipulator technology allowed a machines to be more than just anotherNC machine.It allowed such machines to become robots that can perform a variety of manufacturing tasks in both inaccessible and unsafe environments.By merging these two technologies, Devol developed the first industrial robot, an unsophisticated programmable materials handling machine.The first commercially produced robot was developed in 1959.In 1962, the first industrial robot to be used on a production line was installed by General Motors Corporation.This robot was produced by Unimation.A major step forward in robot control occurred in 1973 with the development of the T-3 industrial robot controlled bya minicomputer.Numerical control and remote and remote manipulator technology prompted the wide-scale development and use of industrial robots.But major technological developments do not take place simply because of such new capabilities.Something must provide the impetus for taking advantage of these capabilities.In the case of industrial robots, the impetus was economics.The rapid inflation of wages experienced in the 1970s tremendously increased the personnel costs of manufacturing firms.At the same time, foreign competition became a serious problem for U.S.manefacturers.Foreign manufacturers who had undertaken automation on a wide-scale basis, such as those in Japan, began to gain an increaaingly large share of the U.S.and world market for manufactured goods, particullarly automobiles.Through a variety of automation techniques, including robots, Japanese manufacturers, beginning in the 1970s, were able to produce better automobiles more cheaply than nonautomated U.S.manufacturers.Consequently, in order to survive, U.S.manufacturers were forced to consider any technological developments that could help improve productivity.It become imperative to produce better products at lower costs in order to be competitive with foreign manufacturers.Other factors such as the need to find better ways of performing dangerous manufacturing tasks contributed to the development of industrial robots.However, the principal rationale has always been, and is still, improved productivity.One of the principal advantages of robots is that they can be used in settings that are dangerous to humans.Welding and parting are examples of applications where robots can be used more safely than humans.Even though robots are closely associsted with safety in the workplace, they can, in themselves, be dangerous.Robots and robot cells must be carefully designed and cinfigured so that they do not endanger human workers and other machines.Robot work envelopes should be accurately calculated and a danger zone surrounding the envelope clearly marked off.Red flooring strips and barriers can be used to keep human workers out of a robot is work envelope.Even with such precautions it is still a good idea to have an automatic shutdown system in situations where robots are used.Such a system should have the capacity to sense the need for an automatic shutdown of operations.Fault-tolerant computers and redundant systems can be installed to ensure proper shutdown of robotics systems to ensure a safe environment.The components of a tobot systerm could be discussed either forma physical of view or from a systems point of ciew.Physically, we would divide the system into the robot, power system, and controller(computer).Likewise, the robot itself could be partitioned anthropomorphically into base, shoulder, elbow, wrist, gripper, and tool.Most of these terms require little explanation.Consequently, we will describe the components of a tobot system from the point of view of information transfer.That is, what information or signal enters the component; what logical or arithmetic operation does the component perform; and what information or signal does the component produce? It is important to note that the same physical component may perform many different information processing operations (e.g., a central computer performs many different calculations on different data ).Likewise, two physically separate components may perform identical information operations (e.g., the shoulder and elbow actuators both convert signals to motion in very similar ways).Actuator Associated with each joint on the robot is an actuator which causes that joint to move.Typical actuators are electric motors and hydtraulic cylinders.Typically, a robot system will contain six actuators, since six are required for full control of position and orientation.Many robot applications do not require this full flexibility, and consequently, robots are often built with five or fewer actuators.Sensor To control and actuator, the computer must have information regarding the posetion and possibly the velocity of the actuator.In this contest, the term position refers to a displacement from some arbitrary zero reference point for that actuator.For example, in the case of a rotary actuator, “ position ” would really the angular posit ionand be measured in radians.Many types of sensors can provide indications of position and velocity.The various types of sensors require different menchanisms for interfacing to the computer.In addition, the industrial use of the manipulator requires that the interface be protected from the harsh electrical environment of the factroy.Sources of electrical noise such as are welders and large motors can easily make a digital system useless unless care is taken in design and construction of the interface.C omputation We could easily have labeled the computation module “ computer , ” as most of the function to be described are typically performed by digital computer.However, many of the functions may be performed in dedicated custom hardware or networks of the computers.We will, thus, discuss the computational component as if it were a simple computer, recognizing that the need for real-time control may require special equipment and that some of this equipment may even be analog, although the current trend is toward fully digital systems.One further note: We will tend to avoid the use of the term microprocessor in this book and simply say computer, although many current robot manufacturers use one or more microprocessors in their systerms.The computation component performs the following operations:Servo Given the current position and/or velocity of an actuator,determine the appropriate drive signal to move that actuator toward its desired position.This operation must be performed for each actuator.Kinematics Given the current state of the actuators ( position and velocity ), determine the current state of the gripper.Conversely, given a desired state of the hand, determine the desired state for each actuator.Dynamics Given konwledge of the loads on the arm ( inertia, friction, gravity, acceleration ), use this information to adjust the servo operation to achieve better performance.Workplace Sensor Analysis Given knowledge of the task to be performed, determine appropriate robot motion commands.This may include analyzing a TV picture of the workplace or measuring and compensating for forces applied at the hand.In addition to these easily identified components, there are also supervisory operations such as path planning and operator interaction.工业机器人有许多关于机器人这个术语的定义。