SPRUHJ1I January 2013 – October 2021 TMS320F2802-Q1 , TMS320F28026-Q1 , TMS320F28026F , TMS320F28027-Q1 , TMS320F28027F , TMS320F28027F-Q1 , TMS320F28052-Q1 , TMS320F28052F , TMS320F28052F-Q1 , TMS320F28052M , TMS320F28052M-Q1 , TMS320F28054-Q1 , TMS320F28054F , TMS320F28054F-Q1 , TMS320F28054M , TMS320F28054M-Q1 , TMS320F2806-Q1 , TMS320F28062-Q1 , TMS320F28062F , TMS320F28062F-Q1 , TMS320F28068F , TMS320F28068M , TMS320F28069-Q1 , TMS320F28069F , TMS320F28069F-Q1 , TMS320F28069M , TMS320F28069M-Q1
Figure 15-26 shows the current waveform under these conditions. Notice how the current changes phase indicating a change in direction.
In this example the actual speed is about 2.5 Hz (37 RPM), so we have a total error of about 7 RPM in this example. This error in the speed calculation is due to the error in flux. The error in flux might be due to inaccuracies of the modeled motor compared to the actual motor, possibly due to overheating or current and voltage sensing tolerances.
For best speed-reversal performance: enable Offsets and Rs Recal, disable forced angle, tune speed controller to avoid stalls, tune voltage feedback circuit.
The flux is higher in this test, as shown in Figure 15-27. This again might be a difference in motor model inaccuracies due to motor overheating after many tests under load.
The angle can be seen as it changes direction in Figure 15-28.
If we zoom-in on the angle (Figure 15-29), when it changes direction, we can see how FAST provides a stable angle even when doing speed reversals with full load.
The speed has a double change in sign here as well (Figure 15-30), and again this is because at near zero speed, especially with full load, the speed estimator chases the sign of the speed and in a transient, we can see how it changes signs from ±10 RPM, or ±0.66 Hz.
The torque estimator provides a clean zero crossing, and final values (Figure 15-31). However, as the estimation of the torque depends on the estimation of the flux, there is a small offset as the flux changed as per Figure 15-26 in this example.
The current, Iq, is also shown in Figure 15-32.