Robust control system design using phase constraints variation approach

When designing a control system, it is quite important to consider different constraints in order to provide the system´s degree of robustness. It is possible to design the robust systems using some conventional approaches. However, they do not make clear how to consider constraints on systems parameters, sufficient system nonlinearities, and how to provide the necessary degree of robustness. The approach is based on phase constraints variations, which allow to solve problems mentioned above.