We describe a method of monitoring of the instantaneous velocity of moving elements in positioning systems. It is shown that various internal or external sources (engines, transmissions, carriages, etc.) cаn give contribution into the velocity variation. A comparison of several drives is given, including the case of a sharp velocity reduction, namely, the defect of non-critical "jamming" when the amplitude of the vibration velocity components decreases to zero. The developed method is of interest for monitoring the occurrence and development of defects in positioning systems during its operation.