Control Engineering Practice

Control engineering is concerned with the analysis and design of goal-oriented systems. Therefore the mechanization of goal-oriented policies has grown into a hierarchy of goal-oriented control systems. Modern control theory is concerned with systems with the self-organizing, adaptive, robust, learning, and optimum qualities. This interest has aroused even greater excitement among control engineers.

The control of an industrial process (manufacturing, production, and so on) by automatic rather than human means is often called automation. Automation is prevalent in the chemical, electric power, paper, automobile, and steel industries, among others. The concept of automation is central to our industrial society. Automatic machines are used to increase the production of a plant per worker in order to offset rising wages and inflationary costs. Thus industries are concerned with the productivity per worker of their plant. Productivity is defined as the ratio of physical output to physical input. In this case we are referring to labor productivity, which is real output per hour of work. In a study conducted by the U.S. Commerce Department it was determined that labor productivity grew at an average annual rate of 2.8% from 1948 to 1984. In order to continue these productivity gains, expenditures for factory automation in the United States are expected to double from 5.0 billion dollars in 1988 to 8.0 billion dollars in 1992. World-wide, expenditures for process control and manufacturing plant control are expected to grow from 12.0 billion dollars in 1988 to 22.0 billion dollars in 1992. The U.S. manufacturers currently supply approximately one-half of worldwide control equipment.

The transformation of the U.S. labor force in the country's brief history follows the progressive mechanization of work that attended the evolution of the agrarian republic into an industrial world power. In 1820 more than 70% of the labor force worked on the farm. By 1900 fewer than 40% were engaged in agriculture. Today, less than 5% work in agriculture.

In 1925 some 588,000 people, about 1.3% of the nation's labor force, were needed to mine 520 million tons of bituminous coal and lignite, almost all of it from underground. By 1980 production was up to 774 million tons, but the work force had been reduced to 208,000. Furthermore, only 136,000 of that number were employed in underground mining operations. The highly mechanized and highly productive surface mines, with just 72,000 workers, produced 482 million tons, or 62% of the total.

The easing of human labor by technology, a process that began in prehistory, is entering a new stage. The acceleration in the pace of technological innovation inaugurated by the Industrial Revolution has until recently resulted mainly in the displacement of human muscle power from the tasks of production. The current revolution in computer technology is causing an equally momentous social change: the expansion of information gathering and information processing as computers extend the reach of the human brain.

The work week in U.S. manufacturing industries shortened from 67 hours in 1860 to about 39 hours in 1984.

Control systems are used to achieve (1) increased productivity and (2) improved performance of a device or system. Automation is used to improve productivity and obtain high quality products. Automation is the automatic operation or control of a process, device, or system. We utilize automatic control of machines and processes in order to produce a product within specified tolerances.

The term automation first became popular in the automobile industry. Transfer lines were coupled with automatic machine tools to create long machinery lines that could produce engine parts, such as the cylinder block, virtually without operator intervention. In body-parts manufacturing, automatic-feed mechanisms were coupled with high-speed stamping presses to increase productivity in sheet-metal forming. In many other areas where designs were relatively stable, such as radiator production, entire automated lines replaced manual operations.

With the demand for flexible, custom production emerging in the 1980s, a need for flexible automation and robots is growing.

There are about 150,000 control engineers in the United States and also in Japan, and over 100,000 control engineers in the Soviet Union. In the United States alone, the control industry does a business of over thirty billion dollars per year! The theory, practice, and application of automatic control is a large, exciting, and extremely useful engineering discipline. One can readily understand the motivation for a study of modern control systems.

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