Simple robust control structures based on the model‐following concept–A theoretical analysis

Abstract

SUMMARYThe paper deals with three robust control systems that may be regarded as a part of the model-following control (MFC) family. The systems are easy-to-synthesize control structures, thus offering an alternative to the low-robust single-loop PID system, to the relatively difficult-to-synthesize internal-model control structures, or to complex adaptive systems. A basic comparative theoretical and computational analysis of properties exhibited by the presented control structures is given. Also, recommendations as to practical implementation are provided. The solutions presented in the paper have found some application, e.g. in force/position control for an industrial robotic manipulator, temperature control of electro-heated furnaces with highly varying parameters, and oxide content control in a steam boiler. Owing to the interesting robustness properties displayed by MFC strict requirements on quality of controlled processes that are both strongly nonlinear and time variant have been met.

Multi-loop model based parallel control systems

“…As may be noted, the robustness of the singleloop structure is the higher, the smaller is the magnitude |R| is, (4). This means that the robustness to plant perturbations is achieved at the expense of quality of tracking the reference signal or of suppression of disturbances.…”

“…1 for the simplest configuration i = 1 has been carried out in [4]. In this case, a further system arises for the switch combination (s 1 = 0, s 2 = 0), namely the known 2DOF IMC structure, along with three different two-loop MFC systems.…”

“…In [4] the allowable process perturbations ∆ p for the single model loop case (i=1) for three structures 1-MFC-m, 1-MFC-p and 1-MFC-mp have been determined:…”

“…It is a simple 2DOF (Degree-ofFreedom) structure based on a forward plant model, which employing initially two classic PID controllers. Its theoretical analysis and interesting robust properties are described in [3] [4]. One of the features displayed by the structure is that the model loop is not affected by disturbances, which not necessarily should be regarded as an advantage.…”

Data‐based output feedback control using least squares estimation method for a class of nonlinear systems

“…Besides, this method is also applicable to MIMO systems.Moreover, most existing nonlinear adaptive control methods generally fall into two broad categories: methods based on explicit knowledge of mathematical model structures and methods based on intelligent control theory. The first category consists of control methods with special requirements on the model structure [24][25][26], for example, lower triangular structure, nonlinear affine structure with respect to the input, and the structure of controlled plant with dynamic inversion. Among these methods, people usually use feedback linearization method or backstepping method, which, however, are not robust to model perturbation or unmodeled dynamics.…”