DC motors are widespread used in modern day applications of different kind, especially those that require a closed loop control. In order to use a DC motor in closed loop control systems, it is required to know the dynamic both electrical and mechanical parameters. Parameter estimation for DC motors, both brushed and brushless, is of equal importance in the field of motor control. Accurate determination of DC motor parameters is vital for a good control. The estimation of parameters could be done using several methods: using hybrid equivalent circuit model, step response, dynamic load variation, closed loop error approach, least square parametric estimation, leastsquares approximation technique and a closed-loop disturbance observer. In the present paper, it is studied the dynamic mechanical parameter identification as a response to a step input signal and identified with a 2 nd order dynamic system.

In this paper fault detection of permanent magnet dc motor is described. In past, Current Signature Analysis (CSA) has become an established tool for online fault analysis of AC induction motors. Presently, very little research has been performed using current signature analysis on DC motors. This paper is a brief introduction to fault diagnosis of DC motors using vibration and current signature analysis. In order to do the diagnostics there are analyzed vibration from the piezoelectric accelerometer. The accelerometer is mounted on the frame's motor. Also, for the current measurement it's used ampere sensor. Initially the measurements were realized by using "healthy" DC motor. Then we made successive measurements for the same type of motor with provoked faults. The many faults of DC motors are regarding collectors motor, the commutator short circuit and displaced permanent magnet out of poles in polar axe. We observe significant vibration and also current spectrum differences between "healthy" motors and faulty electrical motor. The spectral analysis of current and vibration provides a method to detect DC motors faults. Using these methods, diagnostic of commutator short circuit and displaced permanent magnet out of poles in polar axe, would be detected even if the motor operated unload.

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