Tham khảo tài liệu 'robotics process control book part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 18 Introduction Feedforward Control We can also consider another kind of the heat exchanger control when the disturbance variable v is measured and used for the calculation of the heat input . This is called feedforward control. The effect of control is not compared with the expected result. In some cases of process control it is necessary and or suitable to use a combination of feedforward and feedback control. Development of Process Control The history of automatic control began about 1788. At that time J. Watt developed a revolution controller for the steam engine. An analytic expression of the influence between controller and controlled object was presented by Maxwell in 1868. Correct mathematical interpretation of automatic control is given in the works of Stodola in 1893 and 1894. E. Routh in 1877 and Hurwitz in 1895 published works in which stability of automatic control and stability criteria were dealt with. An important contribution to the stability theory was presented by Nyquist 1932 . The works of Oppelt 1939 and other authors showed that automatic control was established as an independent scientific branch. Rapid development of discrete time control began in the time after the second world war. In continuous time control the theory of transformation was used. The transformation of sequences defined as Z-transform was introduced independently by Cypkin 1950 Ragazzini and Zadeh 1952 . A very important step in the development of automatic control was the state-space theory first mentioned in the works of mathematicians as Bellman 1957 and Pontryagin 1962 . An essential contribution to state-space methods belongs to Kalman 1960 . He showed that the linear-quadratic control problem may be reduced to a solution of the Riccati equation. Paralel to the optimal control the stochastic theory was being developed. It was shown that automatic control problems have an algebraic character and the solutions were found by the use of polynomial methods .
