Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems with inputs, and how their behavior is modified by feedback. The usual objective of control theory is to control a system, often called the plant, so its output follows a desired control signal, called the reference. The aim is to develop a model or algorithm governing the application of system inputs to drive the system to a desired state, while minimizing any delay, overshoot, or steady-state error and ensuring a level of control stability.
While roots can be traced to 19th-century work on governors for steam engines by James Clerk Maxwell, the modern era of control theory began in the mid-20th century. Key developments include the formalization of feedback amplifiers and the establishment of cybernetics by Norbert Wiener in the 1940s, which laid the groundwork for analyzing and designing complex control systems.
Control theory is widely used in many fields, including engineering, economics, and biology. It is the foundation for automation and is used to design and analyze systems that can regulate themselves, such as cruise control in cars, autopilots in airplanes, robotics, industrial process control, and thermostats in buildings. It is also used to model and understand complex systems, such as the climate and the economy.