The aim of this paper is present the digital approach to solving one of the most important control problems nowadays: the identification of the time variable physical parameters of a control plant and first of all the moment of inertia. The digital technique opens new possibility in this area. The identification problems of the time variable physical parameters of a control plant and the matrix constituents and the matrix constituents of a linear multidimensional discrete-time system that is the mathematical model of the control plant are considered. Identification conditions for the both cases that connect the memory depth, the quantization frequency and the quantity of the identified parameters are formulated. Using this technique makes possible receiving the estimation of the moment of inertia without information of the load torque. The condition of the identification of the moment of inertia is formulated.