Tuning Guide
Figure 11. Correct Align Time and Acceleration Rate
Figure 12. Align Time Too Long
Figure 13. Align Time Too Short
6.1.2
Open to Close Loop Threshold
Open to close loop threshold determines the threshold frequency at which the controller goes from open-
loop commutation to closed-loop, back-emf, zero-crossing-based commutation. For best performance to
get stability during dynamic load/speed changing conditions and for maximum possible speed range, the
motor should run in closed-loop commutation mode, therefore, the threshold frequency should be chosen
as low as possible. However, too low values will cause an issue with sensor-less control because back-
emf will not be sufficient to allow closed loop operation. Typically this threshold should be 10% to 25% of
the speed desired to run the motor. The values tunable via GUI are in units of Hz. Normally, higher-speed
motors (maximum speed) require a higher handoff threshold because higher speed motors have lower Kt,
and as a result, lower BEMF.
In other words, if your desired RPM is 3000, then the open to close loop threshold should be 1/4 × (500
rpm) = 125 Hz. Therefore, the open to close loop threshold should be around 50
≈
125 Hz.
14
DRV10963 Evaluation Module
SLAU643 – July 2015
Copyright © 2015, Texas Instruments Incorporated
