Families of phase portraits for dynamical systems of pendulum type

In many branches of physics (e.g., dynamics of rigid bodies in nonconservative fields, theory of oscillations, theoretical physics), so-called pendulum-type systems often arise. In this paper, we present methods of analysing such systems that allow one to generalize the previous results of the author concerning such systems. Also, we discuss some problems of the qualitative theory of ordinary differential equations. We prove that generalized systems have nonequivalent phase portraits obtained earlier.