The proposed book is part of a series of monographs on non-linear automatic control systems. It discusses methods for synthesizing nonlinear automatic control systems that allow selecting its best structure and parameters during the design process. In the synthesis of systems, methods of separation of movements of complex systems, harmonic linearization and phase space are used. The examples of synthesis of specific non-linear control systems given in it are of independent importance. The book is intended for scientists, engineers, teachers and graduate students of higher educational institutions involved in automatic control.