. What is modern control theory? What is the relationship or connection with classical control theory? What are the different advantages and disadvantages of each in solving control problems?

Modern control theory to state space description (essentially a system of first-order differential or difference equations) as a mathematical model, the use of computers as a means of system modeling analysis, design and even control, adapted to multivariable, nonlinear, time-varying systems. The state space method belongs to the time domain method, the core of which is to do optimization techniques.

Classical control theory to analyze and design control systems using the method is the frequency characteristic method and root trajectory method. These two methods are effective for analyzing and designing linear, constant univariate systems. However, for nonlinear systems, time-varying systems, multivariable systems, etc., classical control theory is powerless. At the same time, with the improvement of the automation level of the production process, the task of the control system is becoming more and more complex, the control accuracy requirements are also more and more high, therefore, the modern control theory based on the state space analysis method has been rapidly developed.