| There exist many uncertainties in practical control systems, such as external disturbances and noises. These disturbances, system uncertainties, and parameter changes have great impact on system performance. It is indeed necessary to study this control issue. Active disturbance rejection control (ADRC), a method that is independent of precise mathematical model of the controlled object has a function of active estimating and compensating uncertainties. In addition, the method can solve the problem of model disturbance. The content of this thesis is as follows:1. Linear active disturbance rejection control (LADRC) solves the difficulty in parameter turning of early proposed nonlinear ADRC. The paper proposed an improved method of ADRC which is based on linear state feedback and high-order Taylor polynomial approximation. First the system total disturbance was reconstructed through a high-order Taylor polynomial. Then reference input and its differential were used to obtain linear state feedback control. Therefore, the total disturbance can be estimated and compensated effectively. The method provides the solution to two-degree-of-freedom control issue in which characteristics of trajectory tracking and disturbance rejection are hard to meet simultaneously. The improved method has advantages of high-precision tracking, accurate state estimation, and simple implementation.2. The input gain of ADRC is generally set as a constant value, but actually it is a variable with respect to time. If the model of the controlled object can be added into controller design the controller will then be simplified. Moreover, system performance will get better. This paper also proposed a method of dynamic estimating input gain of ADRC. Timing and dynamic controller gain can be obtained by the method based on extended Kalman filter. Dynamic gain method can get over the difficulty and inaccuracy of empirical values.3. The control of the Chylla-Haase polymerization reactor is a control engineering benchmark problem. Control tasks of heat-up period and hold period are different. Because monomer feed and termination, changeable ambient temperature, monomer impurity factor, and fouling factor of reactor wall seriously affect reactor temperature. The control of polymerization reactor is very challenging. Reactor model built by Chylla and Haase has characteristics of nonlinear structure and partial parameter uncertainty. This research suggested that ADRC was applied to Chylla-Haase reactor system. The simulation results show that under reactor parameter uncertainty and interference, the control system remains strong robustness and reliability. With the increasing complexity of modern production processes, research of this subject provides an effective method for model uncertainty and disturbed control system. |
