1. Chapter 3 Simulation for BLDC Motor Drives
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

2. Why is simulation used? Difficulties of experiment:
(1) High requirements for hardware and experiment conditions.
(2) Cause damage to the motor.
(3) Increase the cost of the research.
Computer simulation can effectively help to reduce such difficulties.
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

3. The software commonly used in simulation for motor control system:
What can simulation do?
Help researchers to design and analyze control system more conveniently.
Quicken product development.
Cut down the cost of research.
The software commonly used in simulation for motor control system:
MATLAB/Simulink
ACSL
SPICE
Saber
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

4. Introduction of MATLAB/Simulink
MATLAB/ Simulink has fairly wide application. Simulink owns
Specific toolkit for motor control system simulation.
Demos covering almost all the common types of DC and AC drives.
User-friendly interface.
Strong capability of data analysis based on MATLAB.
Program of MATLAB/Simulink
S-function simulation
Graphical simulation
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

5. 3.1 S-function simulation
Brief introduction of S-function
It is a computer language description of a Simulink block.
It can be used to expand the simulation capability of Simulink.
It can be written in MATLAB language, as well as in other computer languages.
The structure of BLDC motor simulation system
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

6. 3.1 S-function simulation
The commutation logic control and the motor, both realized by S-function programming, are masked as “Control” and “BLDC_Motor”
S-function simulation model for BLDC motor control system
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

7. 3.1 S-function simulation
The core of the sub-system “BLDC_Motor” is an S-function module named “BLDC_Motor” , The main calculating process is:
(1) Calculae back EMF and hall signal;
(2) Calculate the differential of the current state variable;
(3) Calculate torque and angular speed.
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

8. 3.2 Graphical simulation
Simulink can employ all sorts of modules arranged as libraries to achieve dynamic system graphical modeling.
Besides the commonly used modules, Simulink provides module libraries in the form of the toolbox for different research areas.
SimPowerSystem is a power system simulation library
It offers fairly accurate models of many components used in power
system.
It provides libraries of specific application systems, including various
motor drive system models
It is a GUI-based tool with intuitive graphics capability and excellent
data processing ability
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

9. 3.2 Graphical simulation
When the SimPowerSystem library is employed for modeling, the followings have to be paid attention to:
The connection between electrical models and the
common Simulink models.
The measurement of voltage and current.
The connection of inductance and capacitance.
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

10. 3.2 Graphical simulation
Simulation of double closed-loop speed control system
The block diagram of the simulation system
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

11. 3.2 Graphical simulation
Simulation of double closed-loop speed control system
The whole system is comprised of four parts:
(1) The main power circuit
(2) The motor
(3) Measurement unit
(4) Controller unit
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

12. 3.2 Graphical simulation
Advanced conduction of phase current for BLDC motor control
When the reference speed is lower than the rated value, speed regulation can be achieved by changing the terminal voltage of the windings. However, when the reference speed is higher than the rated value, the back EMF is fairly high, and the voltage of the winding cannot be increased any more, so the windings current is not enough to generate higher torque. this will cause the difficulty of increasing the speed of the motor. To overcome this difficulty, the advanced conduction of phase current is usually adopted for BLDC motor speed regulation
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.

13. 3.2 Graphical simulation
Advanced conduction of phase current for BLDC motor control
The simulation block diagram of the BLDC motor controlled by the advanced conduction of phase current
Permanent Magnet Brushless DC Motor Drives and Controls, First Edition. Chang-liang Xia.
© 2012 Science Press. Published 2012 by John Wiley & Sons Singapore Pte. Ltd.