A little bit of engineering (Несколько текстов для зачёта), страница 10

Early in the 19th century, however, this haphazard system of chemical education changed. Many provincial universities were established in Germany, a country with a long tradition of research. A research center in chemistry was set up at Giessen by the German chemist Justus Liebig. This first teaching laboratory became so successful that it drew students from all over the world; other German universities soon followed.

A large group of young chemists was thus trained just at the time when chemical industries were beginning to exploit new discoveries. This exploitation had its start during the Industrial Revolution; the Leblanc process for the production of soda, for example—one of the first large-scale production processes—was developed in France in 1791 and was commercialized in England beginning in 1823. The laboratories of such growing industries were able to employ the newly trained chemistry students and also to use university professors as consultants. This interplay between the universities and the chemical industry benefited both of them, and the accompanying rapid growth of the organic chemical industry toward the end of the 19th century created the great German dye and pharmaceutical trusts that gave Germany scientific predominance in the field until World War I.

After the war, the German system was introduced into all the industrial nations of the world, and chemistry and chemical industries progressed even more rapidly. Among some of the more recent industrial developments, increasing use has been made of enzymatic reaction processes (see Enzyme), mainly because of the low costs and high yields that can be achieved. Industries are at present studying production methods using genetically altered microorganisms for industrial purposes (see Genetic Engineering).

Chemistry has had an enormous influence on human life. In earlier periods chemical techniques were used to isolate useful natural products and to find new ways to employ them. In the 19th century techniques were developed for synthesizing completely new substances that were either better than the natural ones or could completely replace them more cheaply. As the complexity of synthesized compounds increased, wholly new materials with novel uses began to appear. Plastics and new textiles were developed, and new drugs conquered whole classes of disease. At the same time, what had been entirely separate sciences began to be drawn together. Physicists, biologists, and geologists had developed their own techniques and ways of looking at the world, but now it became evident that each science, in its own way, was the study of matter and its changes. Chemistry lay at the base of each of them. The resulting formation of such interscientific disciplines as geochemistry or biochemistry has stimulated all of the parent sciences.

The progress of science in recent years has been spectacular, although the benefits of this progress have not been without some corresponding liabilities. The most obvious dangers come from radioactive materials, with their potential for producing cancers in exposed individuals and mutations in their children. It has also become apparent that the accumulation in plant and animal cells of pesticides once thought harmless or of by-products from manufacturing processes often have damaging effects. These dangerous materials have been manufactured in enormous amounts and dispersed widely, and it has become the task of chemistry to discover the means by which these substances can be rendered harmless. This is one of the greatest challenges science will have to meet.

Robot

Robot, computer-controlled machine that is programmed to move, manipulate objects, and accomplish work while interacting with its environment. Robots are able to perform repetitive tasks more quickly, cheaply, and accurately than humans. The term robot originates from the Czech word robota, meaning “compulsory labor.” It was first used in the 1921 play R.U.R. (Rossum's Universal Robots) by the Czech novelist and playwright Karel Capek. The word robot has been used since to refer to a machine that performs work to assist people or work that humans find difficult or undesirable.

The concept of automated machines dates to antiquity with myths of mechanical beings brought to life. Automata, or manlike machines, also appeared in the clockwork figures of medieval churches, and 18th-century watchmakers were famous for their clever mechanical creatures.

Feedback (self-correcting) control mechanisms were used in some of the earliest robots and are still in use today. An example of feedback control is a watering trough that uses a float to sense the water level. When the water falls past a certain level, the float drops, opens a valve, and releases more water into the trough. As the water rises, so does the float. When the float reaches a certain height, the valve is closed and the water is shut off.

The first true feedback controller was the Watt governor, invented in 1788 by the Scottish engineer James Watt. This device featured two metal balls connected to the drive shaft of a steam engine and also coupled to a valve that regulated the flow of steam. As the engine speed increased, the balls swung out due to centrifugal force, closing the valve. The flow of steam to the engine was decreased, thus regulating the speed.

Feedback control, the development of specialized tools, and the division of work into smaller tasks that could be performed by either workers or machines were essential ingredients in the automation of factories in the 18th century. As technology improved, specialized machines were developed for tasks such as placing caps on bottles or pouring liquid rubber into tire molds. These machines, however, had none of the versatility of the human arm; they could not reach for objects and place them in a desired location.

The development of the multijointed artificial arm, or manipulator, led to the modern robot. A primitive arm that could be programmed to perform specific tasks was developed by the American inventor George Devol, Jr., in 1954. In 1975 the American mechanical engineer Victor Scheinman, while a graduate student at Stanford University in California, developed a truly flexible multipurpose manipulator known as the Programmable Universal Manipulation Arm (PUMA). PUMA was capable of moving an object and placing it with any orientation in a desired location within its reach. The basic multijointed concept of the PUMA is the template for most contemporary robots.

The inspiration for the design of a robot manipulator is the human arm, but with some differences. For example, a robot arm can extend by telescoping—that is, by sliding cylindrical sections one over another to lengthen the arm. Robot arms also can be constructed so that they bend like an elephant trunk. Grippers, or end effectors, are designed to mimic the function and structure of the human hand. Many robots are equipped with special purpose grippers to grasp particular devices such as a rack of test tubes or an arc-welder.

The joints of a robotic arm are usually driven by electric motors. In most robots, the gripper is moved from one position to another, changing its orientation. A computer calculates the joint angles needed to move the gripper to the desired position in a process known as inverse kinematics.

Some multijointed arms are equipped with servo, or feedback, controllers that receive input from a computer. Each joint in the arm has a device to measure its angle and send that value to the controller. If the actual angle of the arm does not equal the computed angle for the desired position, the servo controller moves the joint until the arm's angle matches the computed angle. Controllers and associated computers also must process sensor information collected from cameras that locate objects to be grasped, or they must touch sensors on grippers that regulate the grasping force.

Any robot designed to move in an unstructured or unknown environment will require multiple sensors and controls, such as ultrasonic or infrared sensors, to avoid obstacles. Robots, such as the National Aeronautics and Space Administration (NASA) planetary rovers, require a multitude of sensors and powerful onboard computers to process the complex information that allows them mobility. This is particularly true for robots designed to work in close proximity with human beings, such as robots that assist persons with disabilities and robots that deliver meals in a hospital. Safety must be integral to the design of human service robots.

In 1995 about 700,000 robots were operating in the industrialized world. Over 500,000 were used in Japan, about 120,000 in Western Europe, and about 60,000 in the United States. Many robot applications are for tasks that are either dangerous or unpleasant for human beings. In medical laboratories, robots handle potentially hazardous materials, such as blood or urine samples. In other cases, robots are used in repetitive, monotonous tasks in which human performance might degrade over time. Robots can perform these repetitive, high-precision operations 24 hours a day without fatigue. A major user of robots is the automobile industry. General Motors Corporation uses approximately 16,000 robots for tasks such as spot welding, painting, machine loading, parts transfer, and assembly. Assembly is one of the fastest growing industrial applications of robotics. It requires higher precision than welding or painting and depends on low-cost sensor systems and powerful inexpensive computers. Robots are used in electronic assembly where they mount microchips on circuit boards.

Activities in environments that pose great danger to humans, such as locating sunken ships, cleanup of nuclear waste, prospecting for underwater mineral deposits, and active volcano exploration, are ideally suited to robots. Similarly, robots can explore distant planets. NASA's Galileo, an unpiloted space probe, traveled to Jupiter in 1996 and performed tasks such as determining the chemical content of the Jovian atmosphere.

Robots are being used to assist surgeons in installing artificial hips, and very high-precision robots can assist surgeons with delicate operations on the human eye. Research in telesurgery uses robots, under the remote control of expert surgeons that may one day perform operations in distant battlefields.

Robotic manipulators create manufactured products that are of higher quality and lower cost. But robots can cause the loss of unskilled jobs, particularly on assembly lines in factories. New jobs are created in software and sensor development, in robot installation and maintenance, and in the conversion of old factories and the design of new ones. These new jobs, however, require higher levels of skill and training. Technologically oriented societies must face the task of retraining workers who lose jobs to automation, providing them with new skills so that they can be employable in the industries of the 21st century.

Automated machines will increasingly assist humans in the manufacture of new products, the maintenance of the world's infrastructure, and the care of homes and businesses. Robots will be able to make new highways, construct steel frameworks of buildings, clean underground pipelines, and mow lawns. Prototypes of systems to perform all of these tasks already exist.

One important trend is the development of microelectromechanical systems, ranging in size from centimeters to millimeters. These tiny robots may be used to move through blood vessels to deliver medicine or clean arterial blockages. They also may work inside large machines to diagnose impending mechanical problems.

Perhaps the most dramatic changes in future robots will arise from their increasing ability to reason. The field of artificial intelligence is moving rapidly from university laboratories to practical application in industry, and machines are being developed that can perform cognitive tasks, such as strategic planning and learning from experience. Increasingly, diagnosis of failures in aircraft or satellites, the management of a battlefield, or the control of a large factory will be performed by intelligent computers.