TMS320F28026F Datasheet, PDF (8/19 Pages) Texas Instruments – InstaSPIN-FOC Software

Comparing FAST Estimator to Typical Solutions
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5 Comparing FAST Estimator to Typical Solutions
Table 1 shows a comparison of the FAST estimator and InstaSPIN-FOC solution to typical software
sensors and FOC solutions.
Table 1. FAST Estimator Compared to Typical Solutions
Topic
Typical Software Sensors and FOC Solutions
Fast Estimator and InstaSPIN-FOC Solution
Electrical Motor
Parameters
Motor-model based observers heavily dependent on
motor parameters.
Relies on fewer motor parameters.
Off-line parameter identification of motor – no data
sheet required.
On-line parameter monitoring and re-estimation of
stator resistance.
Estimator Tuning Complex observer tuning, done multiple times for
speed/loads, for each motor.
No estimator tuning required. Once motor parameters
are identified, it works the same way every time,
across speed/torque dynamics.
Estimator Accuracy Angle-tracking performance is typically only good at
over 5-10Hz with challenges at higher speeds and
compensation for field weakening.
Dynamic performance influenced by hand tuning of
observer; Motor stalls typically crash observer.
FAST provides reliable angle tracking which
converges within one electrical cycle of the applied
waveform, and can track at less than 1 Hz frequency
(dependent on quality and resolution of analog
sensing).
Angle tracking exhibits excellent transient response
(even with sudden load transients which can stall the
motor, thus enabling a controlled restart with full
torque).
Start-up
Difficult or impossible to start from zero speed.
Observer feedback at zero speed is not stable,
resulting in poor rotor angle accuracy and speed
feedback.
InstaSPIN-FOC includes:
• Zero Speed start with forced-angle
• 100% torque at start-up
• FAST rotor flux angle tracking converges within
one electrical cycle.
FAST is completely stable through zero speed,
providing accurate speed and angle estimation.
Current Loop
Tuning FOC current control is challenging – especially Automatically sets the initial tuning of current
for novices.
controllers based on the parameters identified. User
may update gains or use own controllers, if desired.
The algorithm to fully tune the observer and torque
controller takes less than 2 minutes.
Feedback Signals System offsets and drifts are not managed.
FAST includes automatic hardware/software
calibration and offset compensation.
FAST requires 2-phase currents (3 for 100% and
over-modulation), 3-phase voltages to support full
dynamic performance, DCbus voltage for ripple
compensation in current controllers.
FAST includes an on-line stator resistance tracking
algorithm.
Motor Types
Multiple techniques for multiple motors: standard
back-EMF, Sliding Mode, Saliency tracking, induction
flux estimators, or "mixed mode" observers.
FAST works with all 3-phase motor types,
synchronous and asynchronous, regardless of load
dynamics. Supports salient IPM motors with different
Ls-d and Ls-q.
Includes PowerWarp™ for induction motors = energy
savings.
Field-Weakening
Field-weakening region challenging for observers - as
the Back-EMF signals grow too large, tracking and
stability effected.
FAST estimator allows easy field weakening or field
boosting applications due to the stability of the flux
estimation in a wide range, including field weakening
region.
Motor Temperature Angle tracking degrades with stator temperature
changes.
Angle estimation accuracy is improved from online
stator resistance recalibration.
Speed Estimation Poor speed estimation causes efficiency losses in the High quality low noise Speed estimator, includes slip
FOC system and less stable dynamic operation.
calculation for induction motors.
Torque Estimation Torque and vibration sensors typically required.
High bandwidth motor Torque estimator.
8 TMS320F28026F, TMS320F28027F InstaSPIN™-FOC Software
Copyright © 2013, Texas Instruments Incorporated
SPRUHP4 – August 2013
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