Indian Streams Research Journal
Vol.2,Issue.IV/May; 12pp.1-4
R.Meenakshi
ISSN:-2230-7850
Research Papers
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE SYSTEM
USING ASYMMETRIC PWM CONTROL TECHNIQUE
S.Sella Kumar
Associate Professor,
Jeppiaar Engineering College,
Chennai, Tamilnadu, India.
Dr.M.Sasikumar
Professor,
Jeppiaar Engineering College,
Chennai, Tamilnadu, India.
R.Meenakshi
P.G Scholar,
Jeppiaar Engineering College,
Chennai, Tamilnadu, India.
Abstract
This paper describes the simulation model for four-switch three-phase (FSTP) brushless dc (BLDC)
motor drives using novel voltage PWM technique. In this paper a back EMF based sensor less scheme is
clearly explained with the help of MATLAB\SIMULINK models. The low cost BLDC driver is achieved by the
reduction of switch device count, cost down of control, and saving of hall sensors for commercial
applications. Field programmable gate array was chosen as the hardware platform because of its benefits
like high operating frequency and parallel processing capabilities. Asymmetric pulse width modulation
scheme is developed to drive FSTP BLDC motors with the desired dynamic and static speed–torque
characteristics. The simulation analysis of the back EMF based sensor less BLDC driver will be discussed and
the performance using novel schemes will be evaluated.
Index Terms—Brushless dc (BLDC) motor, four-switch three phase(FSTP) inverter, field
programmable gate array (FPGA),sensor less control.
1. INTRODUCTION
The 3-phase BLDC motors are well adoptable for industrial applications that require medium
and very high speeds. Sensor and sensor less control are the two methods of control of BLDC motors. In
sensor control Hall sensors are normally used which need maintenance. Some researchers from [1] to [6]
developed new power inverters with reduced cost. Hence in this paper a position sensor less BLDC
motor drive with a new algorithm for sensor less operation and sensor less control without signal
injection is proposed. The rotor position is sensed using back EMF of the motor. Conventionally, BLDC
motors are excited by a six-switch inverter as shown in Fig. 1. In the proposed method the three-phase
voltage source inverters with only four switches, as shown in Fig. 2, is developed In comparison with the
usual three-phase voltage-source inverter with six switches, the main features of this converter are
twofold: the first is the reduction of switches and freewheeling diode count; the second is the reduction
of conduction losses. The BLDC motor has a permanent-magnet rotor, and the stator windings are
wound such that the back electromotive force (EMF) is trapezoidal. It therefore requires rectangularshaped stator phase currents to produce constant torque. The trapezoidal back EMF implies that the
mutual inductance between the stator and rotor is non sinusoidal. Therefore, no particular advantage
exists in transforming the machine equations into the known two-axis equations, which is done in the
case of machines with sinusoidal back EMF So BLDC motor drive with trapezoidal back electromotive
force (EMF) is developed.
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Research Journal
Vol.2,Issue.IV/May; 2012
Figure 1 Conventional six-switch three-phase inverter
Figure 2 Configuration of four-switch three-phase inverter
Figure 3 FPGA-based sensorless FSTP BLDC motor configurations
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
Figure 4 Six commutating modes of voltage PWM scheme for FSTP inverter: (a) Mode I (X, 0); (b)
Mode II (1, 0); (c) Mode III (1, X); (d) Mode IV (X, 1);
In Conventional method position sensors are used to achieve commutation control of BLDC
motors. However, position sensors make the total system more expensive, larger in volume, and less
reliable. On the other hand, sensor less control for four switch three-phase BLDC motors has had many
successful applications. Almost all sensor less control schemes for BLDC motors have to detect the zerocrossing point of voltage waveforms from unexcited windings to estimate the rotor position, but it is
impossible to achieve sensor less control schemes for four-switch three-phase BLDC motors by using
the conventional four-space-vector strategy. In contrast, if six commutation modes are used in the fourswitch inverter, then there are four floating phases during the operating period. Hence, the position
information can be detected from the floating line. This paper presents a novel sensor less control
scheme for the FSTP BLDC motors. On the other hand, with the rapid progress in microelectronics, field
programmable gate array (FPGA) is more and more flexible, programmable and lower in cost, is
therefore to achieve a low cost BLDC control, the Xilinx 3S100E FPGA is used to replace the
microprocessor or DSP to implement the sensor less FSTP inverter scheme, as shown in Fig. 3.
2. NOVEL PWM SCHEME FOR PROPOSED SYSTEM
The proposed voltage pulse width modulation (PWM) scheme for FSTP inverter requires six
commutation modes which are (X,0), (1,0), (1,X), (X,1), (0,1) and (0,X), as shown in Fig. 4 is developed.
The symbols in parenthesis denote the switch ON/OFF states of Sau, Sal, Sbu, Sbl and (phases A and B).
“X” denotes the OFF state for both the high- and low-side switching devices in the same leg, “1” denotes
the ON state for the high-side switching device, and “0” denotes the ON state for the low-side Switching
device. There are two modes to be noted. Two stages corresponding to mode II using conventional PWM
scheme are (1, 0) and (X, 0). This scheme produces a discharging loop between the capacitor and low
side switch and causes non-rectangular stator current waveforms which are harmful for constant torque.
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
Figure 5 Operation stages of FSTP using novel PWM scheme in Mode II:(a) stage (1,0), (b) stage
(X,0), (c) stage (X,X), and (d) the experimental results of stator current waveforms
This paper proposes a novel voltage PWM to overcome this drawback. There are three stages
corresponding to (1, 0), (X, 0), and (X, X), respectively, in Mode II for the novel voltage PWM scheme,
as shown in Fig.5. Experimental results show that the stator current waveforms of the FSTP inverter
using this novel voltage PWM scheme is rectangular, as shown in Fig.5(d). Similar situations apply to
Mode V. The new stage (X, X) of this is introduced to turn off all power devices to prevent the capacitor
discharging from the low-side switch. The commutation sequence and the PWM duty are shown in
table I.
TABLE I
Switching sequence of the novel asymmetric voltage PWM scheme
3. SENSORLESS SCHEME
The FSTP BLDC motor drives using the novel voltage PWM scheme have two phases to detect
the back EMF, but the split capacitors cause the voltage waveform of back EMF to be triangular like.
The voltages detected from phases A and B becomes two triangular like waveforms, and the voltage of
the uncontrolled phase (phase C) becomes VDC/ 2, as shown in Fig. 6. Fortunately, after observing a lot
of experimental results, we found that there we two waveform crossings between phase A and B voltage
waveforms which can be used to estimate the rotor position. If we install rotor position sensors (Hall
sensors) into BLDC motors, when we can observe the voltage waveforms of phases A and B, we found
that two waveform crossings matched the two Hall signals at the same time respectively. Therefore, we
propose to use the two crossings for rotor position estimation for sensor less commutation purposes.
From the crossings we can estimate the timing of the two commutations TC1, andTC2. Assume the first
estimated commutation is equal to T/ 3, and the second estimated commutation is 2T/ 3. The time
difference between the two crossings is equal to the crossing counter (N) multiplied by the period of the
timing counter, which is 10-6 (s).
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
4. SIMULATION RESULTS
In this chapter a position sensor less control scheme for four switch three phase inverter to drive
the BLDC motor has been explained with the simulation results.Figure4.1 shows the simulation model
for sensor less BLDC motor with resistive load and The figure4.3 shows the simulation model for
sensor less control of BLDC motor with motor load. Demultiplexer subsystem configuration is shown
in the figure 8. The stator current, rotor speed, back EMF, electromagnetic torque has been discussed
with the help of simulation results.
Figure 6 simulation model sensor less control of BLDC motor with resistive load
Figure 7 pulses obtained with resistive load
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
Figure 8 Simulation model for Sensor less control of BLDC motor with motor load
4.1 Simulated waveform of sensor less control of BLDC motor
Figure 9 stator current with motor load
Figure 10 rotor speed with motor load
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
Figure 11 Electromagnetic torque with motor load
Figure 12 BackEMF of three phase motor
Table II shows that the torque ripples are reduced and maintained constant when compared with the
conventional system.
5. CONCLUSION
The modeling and the simulation analysis of sensor less control of BLDC motor speed and its
torque results are tested. The motor command speed from 720rpm to a higher speed of 2000rpm runs
stably at both high and low speed under open loop position sensor less control. The position information
is estimated from the crossings of voltage waveforms in floating phases and a low cost FPGA is utilized
to implement the algorithm. Since the stator current waveforms of the FSTP inverter using this novel
voltage PWM scheme are rectangular, the motor will operate smoothly and the torque ripple are
maintained at the same level as reported in [11]. Switches and freewheeling diode count is reduced.
Conduction losses are reduced remarkably. With the developed control scheme and the lowest cost
implementation, the proposed scheme is suitable for commercial applications.
REFERENCES
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brushless DC”.
[2] Shao and Nolan, (2005) “Further improvement of direct back EMF detection for sensorless
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[3] Ogasawara and Akagi, (2008) “An approach to position sensorless drives for brushless dc
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[4] Muthuramalingam, Vedula, and Janakiraman, (2006) “Performance evaluation of an FPGA
controlled soft switched inverter”.
[5] Puyal, Barragán, Acero, Burdío, and Millán, (2006) “An FPGA-based digital modulator for fullor half-bridge inverter control”.
[6] V. krishnakumar and Dr.S. Jeevanandhan, (2011) “Four Switch Three Phase Inverter Control of
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[7] Kwang-Woon Lee, Dae-Kyong Kim, Byung-Taek Kim, and Byung-Il Kwon, (2008) “A Novel
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[8] P. Damodharan and Krishna Vasudevan, (2010) “Sensorless Brushless DC Motor Drive Based
on the Zero-Crossing Detection of Back Electromotive Force (EMF) From the Line Voltage
Difference”.
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)
PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE..............
Indian Streams Reserach Journal
Vol.2,Issue.IV/May; 2012
[9] R.Foley, R. Kavanagh, W. Marnane, and M. Egan, (2006) “Multiphase digital pulsewidth
modulator”.
[10] M. Azab and A. L. Orille, (2001) “Novel flux and torque control of induction motor drive using
four switch three phase inverter”.
[11]B.K Lee, T.H. Kim, and M. Ehsani, (2003) “On the feasibility of four switch three phase BLDC
motor drives for low cost commercial applications: topology and control”.
[12]P.Pillay and R.Krishnan, (1989) “Modelling, Simulation, and analysis of permanent-magnet
motor drives”.
Please cite this Article as : R.Meenakshi , S.Sella Kumar and Dr.M.Sasikumar , PERFORMANCE ANALYSIS OF
SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE : Indian Streams
Research Journal (MAY ; 2012)