CONTROL THEORY,IS IT A MODEL ANALYSIS APPROACH OR A DIRECT CONTROL APPROACH?

Observing the development of the control theory one sees that there are basically two diff-erent approaches:Model Analysis and Direct Control Approach.In the past three decades themodel analysis approach has been the dominating one,while the classical regulation theory andthe guidance theory,etc.are of Direct Control Approach.There is no clear line between the linearity and non-linearity in control systems.The pur-pose of the control is,more or less,a kind of time-varying process of optimization;it is not aglobal system optimization.The value of feedback is not necessarily a function of state variables;it may be some time-varying quantity.To solve the problems of robustness and adaptability of control systems,it is necessary toget rid of the mathematical model of the systems,and to find the control law,which does notdepend on particular expressions of the system.