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Speed Control of BLDC Motor using Sliding Mode Control

Speed Control of BLDC Motor using Sliding Mode Control


We will explore the speed control of a Brushless DC (BLDC) motor using a Sliding Mode Controller (SMC). We will walk through a Simulink model developed for this purpose, explain its components, and analyze the simulation results.




Simulink Model Explanation

The Simulink model for the speed control of a BLDC motor using a Sliding Mode Controller consists of the following main components:

DC Source

Three-Phase Voltage Source Inverter

BLDC Motor Drive

Motor Parameter Measurement (Hall Sensor Output, Speed, Electromagnetic Torque)

Sliding Mode Controller

Sliding Mode Controller

The Sliding Mode Controller (SMC) receives two inputs:


Switching Logic Circuit

The modulated signal (duty cycle) is compared with a triangular wave to generate PWM pulses. These PWM pulses are ANDed with the Hall sensor output from the BLDC motor, resulting in six pulses that drive the voltage source inverter.


The inverter's gate pulses control the motor's voltage and subsequently its speed.


Reference Speed and Torque Command

Initially, the reference speed is set to 1000 RPM. After 0.2 seconds, the reference speed is increased to 1500 RPM. The torque input for the BLDC motor is set to 5 Nm.


Simulation Results

Case 1: Reference Speed 1000 RPM to 1500 RPM

Initial Speed (1000 RPM):


The motor maintains the speed at 1000 RPM.

The overshoot is approximately 20 RPM (2%).

After 0.2 Seconds (1500 RPM):


The motor speed changes from 1000 RPM to 1500 RPM.

The overshoot is approximately 6 RPM (0.4%).

The SMC effectively controls the motor speed with minimal overshoot.


Case 2: Reference Speed 1500 RPM to 200 RPM

Initial Speed (1500 RPM):


The motor reaches 1500 RPM with an overshoot of 0.4%.

After 0.2 Seconds (200 RPM):


The motor speed changes from 1500 RPM to 200 RPM.

The speed is maintained at 202 RPM (error of 2 RPM).

The SMC effectively handles step changes in speed reference, maintaining the desired speed with minimal error.


Torque Response

During speed reference changes, the torque of the motor adjusts to balance the power. The torque is maintained at 5 Nm during steady-state operation.


Conclusion

The Sliding Mode Controller provides effective speed control for the BLDC motor, ensuring minimal overshoot and accurate speed tracking for both increasing and decreasing speed references. This demonstrates the robustness of the SMC in handling disturbances and maintaining desired performance.

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