ABSTRACT:
This paper proposes a new position
sensorless drive for brushless DC (BLDC) motors. Typical sensorless control
methods such as the scheme with the back-EMF detection method show high
performance only at a high speed range because the magnitude of the back-EMF is
dependent upon the rotor speed. This paper presents a new solution that
estimates the rotor position by using an unknown input observer over a full
speed range. In the proposed method, a trapezoidal back-EMF is modelled as an
unknown input and the proposed unknown input observer estimating a line-to-line
back-EMF in real time makes it possible to detect the rotor position. In
particular, this observer has high performance at a low speed range in that the
information of a rotor position is calculated independently of the rotor speed
without an additional circuit or complicated operation process. Simulations and
experiments have been carried out for the verification of the proposed control
scheme.
KEYWORDS:
1.
BLDC motor
2.
Full speed range
3.
Sensorless control
4.
Unknown input observer
SOFTWARE:
MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Overall structure of the proposed sensorless drive system.
EXPECTED SIMULATION RESULTS:
Fig.
2. Response waveforms at under step change of load torque. (Speed reference: 50
rpm, Load: 0.2 → 0.5 Nm).
Fig.
3. Response waveforms under step change of load torque. (Speed reference: 1650
rpm, Load: 0.75 → 1.5 Nm).
Fig.
4. Response waveforms under step change of speed reference. (Load: 0.75 Nm,
Speed reference: 50 → 1650 → 50 rpm).
CONCLUSION:
This paper presented a
new approach to the sensorless control of the BLDC motor drives using the unknown
input observer. This observer can be obtained effectively by using the equation
of augmented system and an estimated line-to-line back- EMF that is modelled as
an unknown input. As a result, the actual rotor position as well as the machine
speed can be estimated strictly even in the transient state from the estimated
line-to-line back-EMF.
The novel sensorless
method using an unknown input observer can
·
be achieved without additional circuits.
·
estimate a rotor speed in real time for
precise control.
·
make a precise commutation pulse even in
transient state as well as in steady state.
·
detect the rotor position effectively
over a full speed range, especially at a low speed range.
·
calculate commutation function with a
noise insensitive.
·
be easily realized for industry
application by simple control algorithm.
The simulation and experimental results successfully
confirmed the validity of the developed sensorless drive technique using the
commutation function.
REFERENCES:
[1] N. Matsui, “Sensorless PM brushless
DC motor drives,” IEEE Trans. on Industrial Electronics, vol. 43, no. 2,
pp. 300-308, 1996.
[2] K. Xin, Q. Zhan, and J. Luo, “A new
simple sensorless control method for switched reluctance motor drives,” KIEE
J. Electr. Eng. Technol., vol. 1, no. 1, pp. 52-57, 2006.
[3] S. Ogasawara and H. Akagi, “An
approach to position sensorless drive for brushless DC motors,” IEEE Trans.
on Industry Applications, vol. 27, no. 5, pp. 928-933, 1991.
[4] J. C. Moreira, “Indirect sensing for
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range,” IEEE Trans. on Industry Applications, vol. 32, no. 6, pp. 1394-1401,
1996.
[5] J. X. Shen, Z. Q. Zhu, and D. Howe,
“Sensorless flux-weakening control of permanent-magnet brushless machines using
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