speed control of bldc motor using pi and

8/10/2019 Speed Control of BLDC Motor Using PI And

1/20

Speed control of BLDC motor

using PI and PID controller

Presenting by:-

Rahul Sharma

Power electronicsand drive

Summited to

Dr. Ravindra K. Singh


2/20

Content

Introduction.

Basic diagram of BLDC motor.

Advantage of BLDC motor.

mathematic modeling of BLDC motor.

Speed control of BLDC.

PI controller.

PID controller.

Comparison between PI and PID controller. Conclusion.

References.


3/20

Introduction

BLDC motor has a rotor with permanent magnets and astator with windings.

The Brushless DC motor is driven by rectangular ortrapezoidal voltage strokes coupled with the givenrotor position.

The commutation takes place electronically.


4/20

Basic diagram of BLDC motor


5/20

Advantage

Reliability.

High dynamic efficiency.

Low maintance . Less electrical noise.

Better speed and torque characteristics.

Low losses.


6/20

MATHEMATICAL MODELING OF BLDC

Motor

BLDCM can be modeled in the three phase abc variableswhich consist of two parts.

1. Electrical part which calculates the electromagnetictorque and current of the motor.

2. The other is the mechanical part, which generatesrevolution of the motor

The following assumptions are made:

1. Ignore the core saturation, as well as eddy current lossesand hysteresis losses.

2. Ignore the armature reaction.3. Power switches and flywheel diode of the inverter circuit

have ideal switching feature


7/20

BLDC motor can be expressed in the matrix form

as:

If there is no change in rotor reluctance with angle

because of a non-salient rotor, and assuming three

symmetric phase,


8/20

.(2)

From the equation (2), phase voltage for phase a,

Va can be derived as

The stator phase currents are constrained to bebalanced

ia+i

b+i

c=0


9/20

The phase voltage of phase b and c, Vb and Vc can bewritten similarly as given below

Equivalent circuit diagram of bldc motor


10/20


11/20

The trapezoidal back-EMF wave forms are modeled as a

function of rotor position so that rotor position can be actively

calculated according to the operation speed.


12/20

Speed control of BLDC motor


13/20

Current controller


14/20

PI Controller

The transfer function of the most basic form of PI

controller is,

Kpis the proportional gain and Kiis the integral

gain.


15/20

Pi controller conti.

Proportional controller produces offset error. Integral controller reduces offset error.

So we have to maintain KPand KIvalues for

stability. Proportional action increases the loop gain

Makes the system less sensitive to variationsof system parameter.

The integral action eliminates or reduces thesteady state error


16/20

PID Controller

The transfer function of the most basic form of PID controller is

Kpis the proportional gain, Kiis the integral gain and Kdis the derivative gain


17/20

PID controller cont.

Proportional controller stabilizes the gain but

produces a steady state error

Integral controller reduces the rise time,

causes an overshoot, increases the settling

Time and most importantly eliminates the

steady state error.

Important function of Kd is to reduce

overshoot and reduce settling time.


18/20

Comparison

Overshoot and settle time is less in PIDcontroller compare to PI controller.

PID controller is more stable , easy adjustment

and high reliable then PI controller.


19/20

Conclusion

Due to non linearity of BLDC motor these

controller faced problem.

Non linearity arises due to change in load,

drive inertia.

For better performance, used some intelligent

techniques with these controller.

PI or PID controller + fuzzy logics.


20/20

References

Atef Saleh Othman, Proportional Integral and

Derivative Control of Brushless DC Motor,

European Journal of Scientific Research,

volume 35, pp. 198-203.

2012 IEEE International Conference on Power

Electronics, Drives and Energy Systems

December16-19, 2012, Bengaluru, India

speed control of bldc motor using pi and

Documents