AN1931D Freescale Semiconductor / Motorola, AN1931D Datasheet - Page 19

• Manufacturer Part Number: AN1931D
• Description: 3-Phase PM Synchronous Motor Vector Control
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
4.3 System Blocks Concept
4.3.1 Position and Speed Sensing
If any of the previously-mentioned faults occur, the motor control PWM outputs are disabled in order
to protect the drive, and the fault state of the system is displayed by the on-board LED.
A hardware error is also detected if the wrong power stage is used. Each power stage contains a simple
module generating a logic sequence unique for that type of power stage. During chip initialization, this
sequence is read and evaluated according to the decoding table. If the correct power stage is identified,
the program can continue. In the case of wrong hardware, the program stays in an infinite loop,
displaying the fault condition.
All members of Motorola’s DSP56F80x family, except the DSP56F801 device , have a quadrature
decoder. This peripheral is commonly used for position and speed sensing. The quadrature decoder
position counter counts up/down each edge of Phase A and Phase B signals according to their order.
On each revolution, the position counter is cleared by an index pulse; see
This means that the zero position is linked with the index pulse, but Vector Control requires the zero
position, where the rotor is aligned to the d axis; see
decoder to decode the encoder’s signal requires either the calculation of an offset which aligns the
quadrature decoder position counter with the aligned rotor position (zero position), or the coupling of
the zero rotor position with the index pulse of a quadrature encoder. To avoid the calculation of the
rotor position offset, the quadrature decoder is not used in this application. The decoder’s digital
processing capabilities are then free to be used by another application and the application presented can
then run on the DSP56F801, which lacks a quadrature decoder.
In addition to the quadrature decoder, the input signals (Phase A, Phase B and Index) are connected to
quad timer module A. The quad timer module consists of four quadrature timers. Due to the wide
variability of quad timer modules, it is possible to use this module to decode quadrature encoder
signals, sense position, and speed. A configuration of the quad timer module is shown in
Freescale Semiconductor, Inc.
3-Phase PM Synchronous Motor Vector Control
Figure 4-2. Quadrature Encoder Signals
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Section
4.3.1.3. Therefore, using a quadrature
Figure
4-2.
System Concept
Figure
4-3.
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