SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

Figure 5.5 – SV diagram for most efficient torque production; stationary frame.
ˆ jref i Ie I e
R R
p
jr
e
jr
2
All sinusoidal synchronous motor controllers must maintain a fixed space-phase relationship like
this. Instead of using a sinusoidal commutator to generate reference signals using trigonometric
functions, the reference could be generated in the rotor reference frame. A space vector is defined
by its components and it is clear that for optimal torque generation, the direct-axis component
should be zero. In that case torque is linearly proportional to the quadrature-axis component, thus
the reference is generated using Equation (5.6).
i
ref
q
T
(5.4)
(5.5)
ref
T
(5.6)
K
The torque controller in the rotor reference frame is shown in Figure 5.6, where the first block is
the inverse Park transform. The current reference signals generated are those shown in Figure 5.8a,
Figure 5.8-b, and Figure 5.8-c.
Figure 5.6 – Torque control in rotor reference frame.
In the previous two schemes it was entirely obvious that rotor position was needed in order to
properly phase the currents to produce torque. The same is true with this controller but there is
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