Abstract
Classical PID controller has been widely used because of its single structure, convenient use, and so on. But PID controller has its limitation, where its linear combination brings the contradiction in speediness and overshoot, which limits PID controller's use. After discussing the defects of classical PID model and analyzing the variation tendency of each PID section in different responsive curves, the authors have created a coefficient model of each section by using the warp ′e′ as parameter correction, and established a universal nonlinear PID model. This model succeeds to the classical PID's advantage of the independence on models and improves on the classical PID's disadvantage. In this paper, considering the characteristic of the heating furnace, a kind of nonlinear PID controller has been put forward based on the nonlinear PID. Two kinds of manipulative methods are applied to heating furnace systems, they belong to classical PID ,nonlinear PID .From comparing with them，we can find that the nonlinear PID method which is presented by this paper, not only has the characteristic of high "robustness and adaptability" that nonlinear PID controller has，but also has higher corresponsive speed and shorter regulating time.
Key words: PID; Nonlinear PID; Nonlinear function; Large lag; Temperature control
