Electronics and Instrumentation

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Instrumentation is a collective term for measuring instruments used for indicating, measuring and recording physical quantities.
The term instrumentation may refer to something as simple as direct reading thermometers or, when using many sensors, may become part of a complex Industrial control system in such as manufacturing industry, vehicles and transportation. Instrumentation can be found in the household as well; a smoke detector or a heating thermostat are examples.
Although control systems of various types date back to antiquity, a more formal analysis of the field began with a dynamics analysis of the centrifugal governor, conducted by the physicist James Clerk Maxwell in 1868, entitled On Governors. This described and analyzed the phenomenon of self-oscillation, in which lags in the system may lead to overcompensation and unstable behavior. This generated a flurry of interest in the topic, during which Maxwell's classmate, Edward John Routh, abstracted Maxwell's results for the general class of linear systems. Independently, Adolf Hurwitz analyzed system stability using differential equations in 1877, resulting in what is now known as the Routh–Hurwitz theorem.
A notable application of dynamic control was in the area of manned flight. The Wright brothers made their first successful test flights on December 17, 1903 and were distinguished by their ability to control their flights for substantial periods (more so than the ability to produce lift from an airfoil, which was known). Continuous, reliable control of the airplane was necessary for flights lasting longer than a few seconds.
By World War II, control theory was an important part of fire-control systems, guidance systems and electronics.
Sometimes, mechanical methods are used to improve the stability of systems. For example, ship stabilizers are fins mounted beneath the waterline and emerging laterally. In contemporary vessels, they may be gyroscopically controlled active fins, which have the capacity to change their angle of attack to counteract roll caused by wind or waves acting on the ship.
The Sidewinder missile uses small control surfaces placed at the rear of the missile with spinning disks on their outer surfaces and these are known as rollerons. Airflow over the disks spins them to a high speed. If the missile starts to roll, the gyroscopic force of the disks drives the control surface into the airflow, cancelling the motion. Thus, the Sidewinder team replaced a potentially complex control system with a simple mechanical solution.
The Space Race also depended on accurate spacecraft control, and control theory has also seen an increasing use in fields such as economics.
People in systems and control
Many active and historical figures made significant contribution to control theory including
  • Pierre-Simon Laplace (1749–1827) invented the Z-transform in his work on probability theory, now used to solve discrete-time control theory problems. The Z-transform is a discrete-time equivalent of the Laplace transform which is named after him.
  • Alexander Lyapunov (1857–1918) in the 1890s marks the beginning of stability theory.
  • Harold S. Black (1898–1983), invented the concept of negative feedback amplifiers in 1927. He managed to develop stable negative feedback amplifiers in the 1930s.
  • Harry Nyquist (1889–1976) developed the Nyquist stability criterion for feedback systems in the 1930s.
  • Richard Bellman (1920–1984) developed dynamic programming since the 1940s.
  • Andrey Kolmogorov (1903–1987) co-developed the Wiener–Kolmogorov filter in 1941.
  • Norbert Wiener (1894–1964) co-developed the Wiener–Kolmogorov filter and coined the term cybernetics in the 1940s.
  • John R. Ragazzini (1912–1988) introduced digital control and the use of Z-transform in control theory (invented by Laplace) in the 1950s.
  • Lev Pontryagin (1908–1988) introduced the maximum principle and the bang-bang principle.
  • Pierre-Louis Lions (1956) developed viscosity solutions into stochastic control and optimal control methods.
  • Ali H. Nayfeh (December 1933 - March 2017) who was one of the main contributors to Non-Linear Control Theory and published many books on Perturbation Methods

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