AN1931D Freescale Semiconductor / Motorola, AN1931D Datasheet - Page 18

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

System Concept
18
The control process is as follows:
When the Start command is accepted (using the Start/Stop Switch or PC master software command),
the required speed is calculated according to the Up/Down push buttons or PC master software
commands. The required speed proceeds through an acceleration/deceleration ramp, and a reference
command is put to the speed controller. The actual speed is calculated from the pulses of the
quadrature encoder. The comparison between the required speed command and the actual measured
speed generates a speed error. Based on the error, the speed controller generates a current, Is_qReq,
which corresponds to torque. A second part of stator current Is_dReq, which corresponds to flux, is
given by the Field-Weakening Controller. Simultaneously, the stator currents Is_a, Is_b, and Is_c are
measured and transformed from instantaneous values into the stationary reference frame
consecutively into the rotary reference frame d-q (Park - Clarke transformation). Based on the errors
between required and actual currents in the rotary reference frame, the current controllers generate
output voltages Us_q and Us_d (in the rotary reference frame d-q). The voltages Us_q and Us_d are
transformed back into the stationary reference frame
recalculated to the 3-phase voltage system, which is applied to the motor.
Beside the main control loop, the DCBus voltage, DCBus current and power stage temperature are
measured during the control process. They are used for overvoltage, undervoltage, overcurrent and
overheating protection of the drive. The undervoltage and overheating protection is performed by
software, while the overcurrent and overvoltage fault signal utilizes a fault input of the DSP.
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