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**Control theory, is it a model analysis approach or a direct control approach?**
*(Chinese.
English summary)*
Zbl 0698.93042

Summary: Observing the development of control theory one sees that there are basically two different approaches: model analysis and direct control approach. In the past three decades the model analysis approach has been the dominating one, while the classical regulation theory and the guidance theory, etc. are of direct control approach.

There is no clear line between linearity and nonlinearity in control systems. The purpose of control is, more or less, a kind of time-varying process of optimization; it is not a global 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 to get rid of the mathematical model of the systems, and to find a control law, which does not depend on particular expressions of the system.

There is no clear line between linearity and nonlinearity in control systems. The purpose of control is, more or less, a kind of time-varying process of optimization; it is not a global 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 to get rid of the mathematical model of the systems, and to find a control law, which does not depend on particular expressions of the system.

### MSC:

93C15 | Control/observation systems governed by ordinary differential equations |

93D15 | Stabilization of systems by feedback |