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Comparing FAST Estimator to Typical Solutions www.ti.com
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 Motor-model based observers heavily dependent on Relies on fewer motor parameters.
Parameters 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 No estimator tuning required. Once motor parameters
speed/loads, for each motor. are identified, it works the same way every time,
across speed/torque dynamics.
Estimator Accuracy Angle-tracking performance is typically only good at FAST provides reliable angle tracking which
over 5-10Hz with challenges at higher speeds and converges within one electrical cycle of the applied
compensation for field weakening. waveform, and can track at less than 1 Hz frequency
(dependent on quality and resolution of analog
Dynamic performance influenced by hand tuning of
sensing).
observer; Motor stalls typically crash observer.
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. InstaSPIN-FOC includes:
Observer feedback at zero speed is not stable, • Zero Speed start with forced-angle
resulting in poor rotor angle accuracy and speed
• 100% torque at start-up
feedback.
• 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 FAST works with all 3-phase motor types,
back-EMF, Sliding Mode, Saliency tracking, induction synchronous and asynchronous, regardless of load
flux estimators, or "mixed mode" observers. 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 FAST estimator allows easy field weakening or field
the Back-EMF signals grow too large, tracking and boosting applications due to the stability of the flux
stability effected. estimation in a wide range, including field weakening
region.
Motor Temperature Angle tracking degrades with stator temperature Angle estimation accuracy is improved from online
changes. 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.
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TMS320F28026F, TMS320F28027F InstaSPIN™-FOC Software SPRUHP4–August 2013
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