TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.04 • 2018-Dec-11
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3.5.9 Orientations, Models of Motors, and Coordinate Transformations
The orientation of magnetic axes (U, V, W for FOC3 resp. X, Y for FOC2) is essential for the FOC together
with the relative orientation of the rotor. Here, the rotor is modeled by a bar magnet with one pole pair
(n_pole_pairs = 1) with magnetic axis in north-south direction.
The actual magnetic axis of the stator - formed by the motor coils - is determined by measurement of the
coil currents.
The actual magnetic axis of the rotor is determined by incremental encoder or by Hall sensors. Incremental
encoders need an initialization of orientation, where Hall sensors give an absolute orientation, but with
low resolution. A combination of Hall sensor and incremental encoder is useful for start-up initialization.
Figure 3: Orientations UVW (FOC3) and XY (FOC2)
Figure 4: Compass Motor Model w/ 3 Phases UVW (FOC3) and Compass Motor Model w/ 2 Phases (FOC2)
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