Any automatically operated machine that replaces human effort, though it may not resemble human beings in appearance or perform functions in a humanlike manner. The term is derived from the Czech word robota, meaning "forced labour." Modern use of the term stems from the play R.U.R., written in 1920 by Czech author Karel Capek, which depicts society as having become dependent on mechanical workers called robots that are capable of doing any kind of mental or physical work.

Modern robot devices descend through two distinct lines of development--the early automaton (q.v.), essentially mechanical toys, and the successive innovations and refinements introduced in the development of industrial machinery.

Possibly the earliest ancestor of today's industrial-robot devices is the clepsydra, or water clock, which improved upon the hourglass by employing a siphon principle to automatically recycle itself. Ctesibius of Alexandria, a Greek physicist and inventor, is reputed to have constructed such a clock about 250 BC. Weight-driven, pendulum-controlled clocks were invented in the European Middle Ages. The spring-driven clock was finally developed during the 18th century, which also witnessed the introduction of rudimentary forms of automatic machinery in the textile industry.

The Industrial Revolution stimulated the invention of elementary robot mechanisms to perfect the production of power itself. The steam engine inspired the governor (actuated by rotating weights), which, when it slowed under load, increased the flow of steam to the engine and, when its load decreased, reduced it. The internal-combustion engine of the 19th century brought a recycling innovation in the form of pistons that repositioned themselves after each cycle. The later 19th and early 20th centuries saw a rapid proliferation of powerful machinery in industrial operations. These at first required a person to position both the work and the machine, and later only the work. Automatic cycle-repeating machines (automatic washers), self-measuring and adjusting machines (textile colour-blending equipment), and machines with a degree of self-programming (automatic elevators) soon followed.

Since the late 1960s major developments in microelectronics and computer technology have led to significant advances in robotics. In the automobile industry, for example, the introduction of computer-controlled robot devices have automated assembly lines to a marked degree. These one-armed robots are capable of simulating the articulation and movement of the human arm and hand and can be used to lift, weld, and spray-paint automobile bodies. The mechanical arms are programmed by physically moving them through the desired motions. The different movements are recorded in the computer's memory so that they can be repeated precisely. Some high-performance robots have built-in sensors that enable them to correct their movements if they deviate from the programmed patterns. Others are equipped with electronic digital cameras and are used to inspect automobile bodies to make certain that their dimensions meet specified standards. In such robot devices, the camera converts images into patterns of digital pulses, which in turn are compared with pulse patterns stored in the controlling computer's memory. The stored patterns represent two-dimensional geometric shapes that the computer has been programmed to identify. Similar kinds of advanced high-performance robots have been adopted by other assembly industries. Aircraft manufacturers employ single-arm mechanisms for drilling and riveting body sections, while a growing number of electronics firms are utilizing robot devices in conjunction with other computerized instruments to sort or test finished products.

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