seminar presentation bldc

8/14/2019 seminar presentation bldc

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Outl ine

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Abstract

INTRODUCTION

BRUSHLESS DC MOTOR DRIVE

STRATEGIES DIGITAL PWM CONTROL OF BLDC DRIVES

CONTROLLER DESIGN

DESCRIPTION OF EXPERIMENTAL SETUP

SIMULATION RESULTS ANDEXPERIMENTAL VERIFICATION

CONCLUSION


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Abstract

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Development of advanced motor drives has yielded

increases in efficiency and reliability.

Residential and commercial appliances such as

refrigerators and air conditioning systems use conventional

motor drive technology.

The machines found in these applications are

characterized by low efficiency and high maintenance.


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In a market driven by profit margins, the appliance industry is

reluctant to replace the conventional motor drives with theadvanced motor drives (BLDC) due to their higher cost.

A simple novel digital pulse width modulation (PWM) controlhas been implemented for a trapezoidal BLDC motor drive

system.

The novel controller is modeled and verified using simulations.

Experimental verification is carried out using field-

programmable gate arrays to validate the claims presented.


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INTRODUCTION

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An ELECTRIC motor is defined as a transducer thatconverts electrical energy into mechanical energy.

In the case of dc machines, they require moremaintenance due to the presence of brushes.

Replacing these inefficient motors with more efficientbrushless dc (BLDC) motors will result in substantialenergy savings.


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BRUSHLESS DC MOTOR DRIVE

STRATEGIES

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The typical inverter drive system for a BLDC motor is

shown in Fig. 1.

Fig. 1. Typical inverter drive system for a BLDC motor.


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In order to get constant output power and, consequently,

constant output torque, current is driven through a motor

winding during the flat portion of the back-EMF waveform.

shown in Fig. 2.

Fig. 2. Back EMF and phase current variation with rotor electrical angle.


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It is important to know the rotor position in order to follow the

proper energizing sequence.

A timing diagram showing the relationship between the sensor

outputs and the required motor drive voltages is shown in Fig.

3.

Fig. 3. Sensor versus drive timing.


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The input sensor state and the corresponding drive state

required for commutation can be put in the form of a state

table as shown in Table I.


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DIGITAL PWM CONTROL OF BLDC

DRIVES

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The general structure of a current controller for a BLDCmotor is shown in Fig. 5.

Fig. 5. Conventional PWM current control.


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This paper presents the design, simulation, and experimentalverification of a novel constant-frequency digital PWM

controller which has been designed for a BLDC motor drivesystem. shown in Fig. 6.

Fig. 6. Flowchart describing the novel digital control.


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This paper presents a controller with no need of any state

observer. Fig. 7 shows the proposed digital controller. Fig. 8

shows the complete block diagram of the motor drive system.

Fig. 8. Block diagram for digital PWM

control for a BLDC motor drive systemFig. 7. Proposed digital control.


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A proportional controller provides the reference for the current

limit.

The minimum value of Ilimit decides the steady-state error.

The proportional constant K for a desired speed ripple can be

calculated as follows. In steady state, |err 2|. In the

worst case, = |err 2|. For the desired speed ripple , a

constant Kset can be defined as


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Taking the maximum value of the speed ripple

As long as

In addition, Ilimit error

By using (1)(3) in (4), it can be shown that


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In this control strategy, both the high- and low-side switches

are switched simultaneously. Both high- and low-side diodes

conduct. The waveforms for this type of switching are shown inFig. 9.

Fig. 9. Gate switching waveforms.


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CONTROLLER DESIGN

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The value of D can be expressed as a function of the motorparameters. From the torque equation, we have


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DESCRIPTION OF EXPERIMENTAL

SETUP

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The experimental setup is shown in Fig. 12.

Fig. 12. Final experimental setup.


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TABLE II

DATA SHEET FOR BLDC MOTOR FROM POLY-SCIENTIFIC


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The actual speed was easily calculated as a time between two

Hall effect signals. The schematic of the controller simulated in

the FPGA is shown in Fig. 13.

Fig. 13. Block diagram showing operations and functions implemented

in FPGA device.


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SIMULATION RESULTS AND

EXPERIMENTAL VERIFICATION

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For the verification of the control scheme, severaloperating conditions were selected.

Fig. 14. Simulated duty, speed, and current response for a commanded

speed of 2500 r/min for full-load operation.


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Fig. 17. Experimental results for a reference speed of 1500 r/min under

no load condition.

Fig. 18. Experimental results for a reference speed of 1500 r/min. Loadis 30% of rated value.


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Fig. 19. Experimental results for a reference speed of 2100 r/minunder full load.


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Fig. 20. Speed response for

change in load torque and for a

reference speed of 2000 r/min.

Fig. 21. Experimental results for a

change in reference speed from 2200

to 1300 r/min under no-load condition.


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CONCLUSION

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The aim of this paper is to develop a low-cost controller for

applications where inefficient single-phase induction motors are used.

Due to the simplistic nature of this control, it has the potential to be

implemented in a low-cost application-specific integrated circuit.

Furthermore, this control strategy does not require a state observer.

Under dynamic load conditions, the proposed controller was found to

be capable of regulating speed without the use of an observer.

This results in a considerable reduction of size and the cost of the

system.

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