08-02-2013, 10:11 AM
Control of BLDC motor with the help of Pulse Width Modulation
1Control of BLDC motor.pdf (Size: 226.48 KB / Downloads: 268)
Abstract :
Shift-by-Wire is about replacing the mechanical
link between the automatic transmission and the shift lever
with an electromechanical system. This will make new safety
functions possible and assist the driver in other
ways. To do this, an actuator with a brushless DC motor is
built into the transmission. It controls the position of the shift
valve, which decides the driving position. This thesis concerns
the working of the Brushless DC motor. This is done by
programming a shift control unit which generates PWM
signals along with an inverter
INTRODUCTION
Brushless Direct Current (BLDC) motors are one of
the motor types rapidly gaining popularity. BLDC
motors are used in industries such as appliances,
automotive, aerospace, consumer, medical etc. As the
name implies, BLDC motors do not use brushes for
commutation; instead, they are electronically
commutated. BLDC motors have many advantages
over brushed DC motors and induction motors. A few
of these are:1. Better speed versus torque
characteristics 2.High dynamic response 3.High
efficiency 4.Long operating life 5.Noiseless operation
6.Higher speed ranges.
Commutation Sequence
For every 60 electrical degrees of rotation, one of the
Hall sensors changes the state. Given this, it takes six
steps to complete an electrical cycle.
In synchronous, with every 60 electrical degrees, the
phase current switching should be updated. However,
one electrical cycle may not correspond to a complete
mechanical revolution of the rotor. The number of
electrical cycles to be repeated to complete a
mechanical rotation is determined by the rotor pole
pairs. For each rotor pole pairs, one electrical cycle is
completed. So, the number of electrical
cycles/rotations equals the rotor pole pairs. Figure 5
shows a block diagram of the controller used to
control a BLDC motor. Q0 to Q5 are the power
switches controlled by the PIC18FXX31
microcontroller. Based on the motor voltage and
current ratings, these switches can be MOSFETs, or
IGBTs, or simple bipolar transistors.
Conclusion
In conclusion, BLDC motors has advantages over
brushed DC motor and induction motors. They have
better speed versus torque characteristics, high
dynamic response, high efficiency, long operating
life, noiseless operation, higher speed ranges, rugged
construction and so on. Also the torque delivered to
the motor size is higher, making it useful in
applications where space and weight are critical
factors