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Step 2: Click the Start button and the plot window will show two curves. The red
one is target current and the green one is actual current. There is large gap between
them in the scope. It indicates that a large Kp need to be introduced. See figure 6-21.
Figure 6-21: Current loop tuning with Kp=500, Ki=0
Step 3: Increase Kp to 1000 and click Start. The gap between target value and
actual value is smaller but a higher Kp is needed. See figure 6-22.
Figure 6-22: Current loop tuning with with Kp=1000, Ki=0
Step 3: Give Kp 2000, 3000, 4000, 5000 and click Start, respectively. The green
curve is getting more and more close to the red curve. See figure 6-23. Over-shoot
begins when we increase Kp to 5000. It indicates that you need to stop increasing
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Kp and back off. Our purpose is to make the green curve (the actual current) a little
higher than the red curve (the target). So we decrease Kp to 4500, 4200 and until the
actual value is exactly over the target value.
Step 4: Now Kp is relative good enough. But there is still gap between the green
curve and the red curve when we use the mouse to zoom in it as shown in figure
6-24. There is also big vibration, which will cause motor noise, on the green curve.
So we need to introduce Ki, the integral gain to reduce the "gap" or steady error at
the constant part. It follows the same procedure as Kp. Too high Ki will causes big
vibration, system lag and makes the performance worse. See figure 6-24 for this
procedure. Increase Ki until the gap can be accepted and not causes much vibration.
Step 5: The current loop tuning is basically finished. You can continue to adjust Kp
and Ki for better performance. Now the updated Kp and Ki is just stored in the
driver's RAM. They will be lost when we power off the driver. Please click
Option->SaveToDriver to store the changed value to the driver's EEPROM.
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Figure 6-23: Current loop tuning with with Ki=0 and increasing Kp
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↑Kp=2000, Ki=0
↑Kp=3000, Ki=0
↑Kp=4000, Ki=0
↑Kp=5000, Ki=0
↓Kp=4500, Ki=0
↓Kp=4200, Ki=0
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