The idea and practice of automatic control have a long history. It is produced in the process of human understanding and transforming the world, and continues to develop with the development of society and the progress of scientific level. As early as 300 BC, ancient Greece used the feedback control principle to design the float regulator, which was used in water clocks and oil lamps. As early as more than 1000 years ago, ancient Chinese ancestors also invented control devices such as copper pot drip timer and guide car. The first automatic controller used in industry was the flying ball controller invented by j.watt in 1769 to control the speed of steam engine. Before 1868, the design of automatic control devices and systems was still in the intuitive stage, without systematic theoretical guidance. Therefore, problems often occurred in the coordinated control of various performance (such as stability, accuracy and speed) of the control system. In the latter half of the 19th century, many scientists began to study the automatic control theory based on mathematical theory, which had a positive impact on the performance improvement of the control system. In 1868, j.c.maxwell established the differential equation mathematical model of the flying ball controller, and analyzed the stability of the system according to the solution of the differential equation. In 1877, e.j.routh put forward the stability criterion without seeking the root of the differential equation of the system. In 1895, a.hurwitz independently proposed a similar Horwitz stability criterion. Before and after the Second World War, due to the need of automatic weapons, there was a greater demand for the research and practice of control theory, which greatly promoted the development of automatic control theory. In 1948, the publication of cybernetics by mathematician N.Wiener marked the official birth of cybernetics. After more than half a century of continuous development, the "science of control and communication in animals and machines" (Wiener's classical definition) has undergone great changes in its research contents and research methods. Generally speaking, the development of cybernetics has gone through three periods: the first stage is the classical cybernetic period from the late 1940s to the 1950s, focusing on the study of single machine automation, Solve the control problem of SISO (single input single output) system; Its main mathematical tools are differential equation, Laplace transform and transfer function; The main research methods are time domain method, frequency domain method and root locus method; The main problems are the rapidity, stability and accuracy of the control system. The second stage is the period of modern control theory in the 1960s, focusing on solving the control problems of unit automation and MIMO multi input multi output systems of biological systems; The main mathematical tools are first-order differential equations, matrix theory, state space method and so on; The main methods are variational method, maximum principle, dynamic programming theory, etc; The key points are optimal control, stochastic control and adaptive control; The core control device is an electronic computer;
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