Generation (excitation) of oscillations. The third class of control goals corresponds to the problems of "excitation" or "generation" of oscillations. Here, it is assumed that the system is initially at rest. The problem is to find out if it is possible to drive it into an oscillatory mode with the desired characteristics (energy, frequency, etc.) In this case the goal trajectory of the state vector x ∗ ∗ ( t ) is not prespecified. Moreover, the goal trajectory may be unknown, or may even be irrelevant to the achievement of the control goal. Such problems are well known in electrical, radio engineering, acoustics, laser, and vibrational technologies, and indeed wherever it is necessary to create an oscillatory mode for a system. Such a class of control goals can be related to problems of dissociation, ionization of molecular systems, escape from a potential well, chaotization, and other problems related to the growth of the system energy and its possible phase transition. Sometimes such problems can be reduced to tracking, but the reference trajectories x ∗ ∗ ( t ) in these cases are not necessarily periodic and may be unstable. Besides, the goal trajectory x ∗ ∗ ( t ) may be known only partially.