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Speed control of BLDC motor using H Infinity Controller in MATLAB

Speed control of BLDC motor using H Infinity Controller in MATLAB

This video explains the how to design H infinity controller for speed control of bldc motor in matlab simulink.

Speed Control of BLDC Motor Using H Infinity Controller in MATLAB

In the field of electrical engineering, speed control of motors plays a crucial role in various applications. One such motor widely used is the Brushless Direct Current (BLDC) motor. BLDC motors are known for their high efficiency, compact size, and low maintenance requirements. To ensure optimal performance of BLDC motors, speed control becomes essential. In this article, we will explore the concept of speed control of BLDC motors using an H Infinity controller in MATLAB.

Table of Contents

  1. Introduction to BLDC Motors

  2. Basics of Speed Control

  3. H Infinity Controller Overview

  4. Implementation of H Infinity Controller in MATLAB

  5. Simulation Results and Analysis

  6. Advantages of H Infinity Control

  7. Limitations and Challenges

  8. Future Developments and Trends

  9. Conclusion

  10. FAQs

Introduction to BLDC Motors

BLDC motors, also known as electronically commutated motors, are widely used in industries and appliances due to their superior performance characteristics. Unlike conventional motors, BLDC motors eliminate the need for brushes and commutators by using electronic commutation. This feature makes them more reliable, efficient, and durable compared to traditional motors.

Basics of Speed Control

Speed control of BLDC motors refers to the ability to regulate the rotational speed of the motor according to the desired application requirements. Various speed control methods exist, including open-loop control, closed-loop control, and sensorless control. Closed-loop control, which utilizes feedback from sensors, is the most commonly used method as it offers precise speed regulation.

H Infinity Controller Overview

The H Infinity controller is a robust control technique that provides optimal performance even in the presence of uncertainties and disturbances. It aims to minimize the effects of external disturbances and system uncertainties on the motor's speed response. The H Infinity controller achieves this by designing a controller that maximizes the closed-loop system's stability and performance while considering the worst-case scenarios.

Implementation of H Infinity Controller in MATLAB

MATLAB, a popular software tool for mathematical computation and simulation, offers powerful features for designing and implementing control systems. To implement the H Infinity controller for speed control of a BLDC motor, the following steps can be followed:

  1. System Modeling: Develop a mathematical model of the BLDC motor and its associated dynamics.

  2. Controller Design: Design the H Infinity controller using the system model and controller synthesis techniques.

  3. Simulation Setup: Set up the simulation environment in MATLAB, including defining the desired speed reference and disturbance signals.

  4. Control System Integration: Integrate the H Infinity controller with the BLDC motor model in MATLAB.

  5. Performance Evaluation: Simulate the closed-loop system and analyze the speed response, control effort, and disturbance rejection capability.

  6. Fine-Tuning and Optimization: Iterate the design process, making adjustments to the controller parameters for achieving desired performance.

Simulation Results and Analysis

After implementing the H Infinity controller in MATLAB, a simulation can be carried out to evaluate the performance of the speed control system. The simulation results provide insights into the motor's speed response under different operating conditions, such as step changes in the reference speed and disturbances. The analysis of these results helps in assessing the effectiveness of the H Infinity controller and identifying areas for improvement, if any.

Advantages of H Infinity Control

The utilization of an H Infinity controller for speed control of BLDC motors offers several advantages:

  1. Robustness: The H Infinity controller provides robust performance, ensuring stability and control even in the presence of uncertainties and disturbances.

  2. Precision: It allows for precise speed regulation, meeting the specific requirements of various applications.

  3. Adaptability: The controller can adapt to changes in the motor's dynamics and external factors, maintaining optimal performance.

  4. Enhanced Efficiency: By minimizing the effects of disturbances, the H Infinity controller helps improve the motor's overall efficiency.

Limitations and Challenges

While the H Infinity control technique offers numerous benefits, it is essential to consider its limitations and challenges:

  1. Complex Design Process: The design and implementation of the H Infinity controller require expertise in control theory and system modeling.

  2. Computational Requirements: The calculations involved in synthesizing the H Infinity controller can be computationally intensive, necessitating powerful hardware.

  3. Tuning Sensitivity: Fine-tuning the controller parameters for optimal performance can be a challenging task, requiring careful adjustment and analysis.

  4. Real-time Implementation: Implementing the H Infinity controller in real-time systems may introduce additional complexities and constraints.

Future Developments and Trends

As technology continues to advance, the field of speed control for BLDC motors using H Infinity controllers is likely to witness further developments. Some potential future trends include:

  1. Advanced Control Algorithms: Researchers are exploring the integration of advanced control algorithms, such as machine learning and adaptive control, with H Infinity control for improved performance.

  2. Hardware Optimization: Efforts are being made to develop specialized hardware platforms that can efficiently execute H Infinity control algorithms, reducing computational requirements.

  3. Integrated Control Systems: The integration of H Infinity control with other control systems, such as position control and torque control, is an area of interest for achieving comprehensive motor control.


Speed control is a crucial aspect of maximizing the performance and efficiency of BLDC motors. The utilization of an H Infinity controller in MATLAB enables precise control and robust performance, even in the presence of uncertainties and disturbances. By following the outlined steps for implementation and conducting simulations, engineers can design and evaluate the effectiveness of the control system. With ongoing advancements in control algorithms and hardware, the future holds promising developments in the field of speed control for BLDC motors.


  1. Q: Can I use other control techniques for speed control of BLDC motors? A: Yes, various control techniques like PID control and sliding mode control can be used for speed control of BLDC motors. However, the H Infinity controller offers robust performance in the presence of uncertainties and disturbances.

  2. Q: What are the key advantages of BLDC motors compared to traditional motors? A: BLDC motors offer higher efficiency, compact size, reduced maintenance requirements, and improved reliability compared to traditional motors.

  3. Q: Is MATLAB the only software tool available for implementing control systems? A: No, there are other software tools available for control system design and simulation, such as Simulink, LabVIEW, and Python-based libraries like Control Systems Toolbox.

  4. Q: Can the H Infinity controller be applied to other types of motors? A: Yes, the H Infinity controller is a general control technique and can be applied to various types of motors, including DC motors and AC induction motors.

  5. Q: Are there any commercial products available that utilize H Infinity control for BLDC motor speed control? A: Yes, several companies offer motor control solutions that incorporate H Infinity control techniques for precise speed control of BLDC motors.

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