AN1917D Freescale Semiconductor / Motorola, AN1917D Datasheet - Page 7

• Manufacturer Part Number: AN1917D
• Description: 3-Phase PM Synchronous Motor Control with Quadrature Encoder Using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
3.1.1 Control Technique
The presented control algorithm demonstrates the principle of PM Synchronous motor control and use
of the DSP56F80x peripheral. It means that this algorithm can be used as starting point for more
sophisticated algorithms.
As is well known, the PM Synchronous (Permanent Magnet) motor is very similar to a Brushless DC
motor. The PM Synchronous motors differ in three respects:
Using a six-step control technique we get six flux vectors. This technique is commonly used for BLDC
motors (see [14], [15]). In the case of sinusoidal voltage output, we are able to generate the stator flux
in any position. The resultant flux is calculated as the sum of flux vectors of Phase A, Phase B and
Phase C (see
field is generated. As a result, a PM Synchronous motor runs smother and quiter than a BLDC motor.
The motor runs with optimal torque generation when the angle between the stator and rotor flux is 90
electric degrees (see
To ensure the angle between rotor and stator flux equals to 90 electric degrees it is necessary to know
the position of the rotor and stator flux.
The position of the rotor flux is bound to the rotor position. Thus, by measuring rotor position we can
get the exact position of the rotor flux.
The position of stator flux is bound to the vector of the stator current. To know the exact position of the
stator flux, it requires measurement of the phase currents and the calculation of the stator current
vector. Since the presented application does not measure current, there is no way to obtain the position
of current vector.
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sinusoidal distribution of magnet flux in the air gap
sinusoidal current waveforms
sinusoidal distribution of stator conductors.
Figure
Figure 3-6
3-5). If the phase voltage changes sinusoidally over time, a fluent rotational flux
3-Phase PMSM Control with Quadrature Encoder
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 3-5. Stator Flux Generation
a)).
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Target Motor Theory
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