The 1940s ~ 1950s was the period of local automation and the classical control theory formed during the Second World War

It played an important role in promoting the development of local automation after the war. In the process of solving the problem, the classical control theory is formed, various precise automatic adjustment devices are designed, and a new scientific field of system and control is created. This new discipline was called servo mechanism theory in the United States and automatic adjustment theory in the Soviet Union, mainly to solve the problem of single variable control. The name of classical control theory was put forward at the first American joint automatic control conference in 1960. After 1945, due to the lifting of the wartime publishing ban, there were works systematically expounding the classical control theory. In 1945, American mathematician Wiener, N. extended the concept of feedback to all control systems. Since the 1950s, classical control theory has made many new developments.. The method of classical control theory can basically meet the needs of military technology in the Second World War and the needs of post-war industrial development. However, in the late 1950s, it was found that when the method of classical control theory was extended to multivariable systems, it would draw wrong conclusions. The method of classical control theory has its limitations.