Observer‐Based Fault Detection for DC Motor Drives: Integrated PI Control and Diagnosis of Parametric and Disturbance Faults

ABSTRACT

In this paper, an integrated fault detection and compensation approach on a direct current (DC) motor drive, focusing on two important fault situations namely, internal parameter changes (increase in motor armature resistance), and disturbance in the load torque, has been introduced. The main concept behind the proposed approach is based on the use of a PI speed control scheme along with a reduced‐order current observer. A mathematical model of a DC motor has been derived, and incorporation of fault conditions has been introduced as a 20% rise in motor armature resistance along with a step change of 2.0 Nm in load torque. The PI control scheme, identified on a root locus, has ensured fast convergent response as well as eliminated steady‐state error. The numerical results indicate that the control system ensured a steady reference speed of 100 rad/s within a small overshooting margin and a shorter settling time. During the introduction of the fault, a stabilization in the system took place without oscillations as the transient deviations were eliminated. The value of the residual, calculated from the difference between the actual and estimated currents, indicated a level below 0.01 A for the healthy state, a rise to 0.06 A in the resistance fault, and a sudden spike to 0.2 A in the torque disturbance. The phase plane validation demonstrated the robustness of the closed‐loop system. The proposed framework combines a proportional–integral speed controller with a reduced‐order current observer for residual generation. The reported findings are based on numerical simulations, while processor‐specific real‐time assessment and experimental validation on a physical direct‐current motor platform remain subjects of future investigation.