Speed Control of PMBLDC Motor Using MATLAB/Simulink and Effects of Load and Inertia Changes


Modeling and simulation of electromechanical systems with machine drives are essential steps at the design stage of such systems. This paper describes the procedure of deriving a model for the brush less dc motor with 120-degree inverter system and its validation in the MATLAB/Simulink platform. The discussion arrives at a closed-loop speed control, in which PI algorithm is adopted and the position-pulse determination is done through current control for a standard trapezoidal BLDC motors. The simulation results for BLDC motor drive systems confirm the validity of the proposed method.


  1. PMBLDC Motor
  2. Simulation and modeling
  3. Speed control




Figure 1. PMBLDC motor drive system


Steady state currentimage002

Figure 2. Stator phase currents

Back EMF of the BLDC motor


Figure 3. Trapezoidal back EMF


Figure 4. Reference current waveform


Figure 5. Representative phase voltage (van)


Figure 6. Torque and speed responses during startup transients


Figure 7. Torque and speed responses – step input change – moment of inertia 0.013 kg-m2 (step time 0.5 S)


Figure 8 Torque and speed responses at moment of inertia 0.098 kg-m’


Figure 9. Torque and speed-Step input with moment of inertia 0.098

kg-m2 (step time 0.5 S)


Figure 10. Step load torque (9Nm) at 0.75 step


Figure 11. Step load torque (25 Nm) at 0.75


Figure 12. Application of heavy load (100 Nm)


Figure 13. Load toque 25Nm at step of 0.5


The nonlinear simulation model of the BLDC motors drive system with PI control based on MATLAB/Simulink platform is presented. The control structure has an inner current closed-loop and an outer-speed loop to govern the current. The speed controller regulates the rotor movement by varying the frequency of the pulse based on signal feedback from the Hall sensors. The performance of the developed PI algorithm based speed controller of the drive has revealed that the algorithm devises the behavior of the PMBLDC motor drive system work satisfactorily. Current is regulated within band by the hysteresis current regulator. And also by varying the moment of inertia observe that increase in moment of inertia it increases simulation time to reach the steady state value. Consequently, the developed controller has robust speed characteristics against parameters and inertia variations. Therefore, it can be adapted speed control for high performance BLDC motor.


[I] Duane C.Hanselman, “Brushless Permanent-Magnet Motor Design”, McGraw-Hill, Inc., New York, 1994.

[2] TJ.E. Miller, ‘Brushless Permanent Magnet and Reluctance Motor Drives.’ Oxford Science Publication, UK, 1989.

[3] RKrishnan, Electric Motor Drives: Modeling, Analysis, and Control, Prentice-Hall, Upper Saddle River, NJ, 2001.

[4] P Pillay and R Krishnan, “Modeling, simulation, and analysis of permanent Magnet motor drives. Part II: The brushless dc motor drive,” IEEE Transactions on Industry Applications, vol.IA-25, no.2, pp.274-279, Mar./Apr. 1989.

[5] RKrishnan and A. J. Beutler, “Performance and design of an axial field permanent magnet synchronous motor servo drive,” Proceedings of IEEE lASAnnual Meeting, pp.634-640,1985.




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