Quote:
Originally Posted by DCM
the pulse doesn't get generated without a known rotor position, when that happens, you can get rollback or just pause, it is because of the sudden loss of motion, the esc can't work out which coil to energise.
|
You are correct in that the energizing of the correct leg dose not happen without knowing the rotor position. The premise of your statement is very close but this is not completely correct with sensored brushless systems. And even in sensorless it is not 100% true. I will explain...
Sensorless systems send a signal that "tests" the rotor location. This takes pico seconds. Then they fire the appropriate leg (L1, L2, or L3) to generate the desired rotational direction. This result is "tested" again to insure that the correct direction has hit. This is correct than 90% of the time. Except for Tekin (sensorless ESC's) and Castle Creations, they enjoy a correct rate of more than 98% because of the algorithms they employ.
In a sensored system this dose not happen (this gentleman and the ones I have seen this problem in are sensored) In sensored systems there is a hall effect (magnetic) sensor array that gives precise position to the ESC at ALL TIMES, even at rest. There is no "test". The ESC is receiving rotor position information and using that information to control the motor rotation and speed.
As far as loss of motion causing a loss that is really irrelevant. Since this "test" for sensorless and the hall effect array happen each and every time this would not account for it going the correct way but just at a slow speed. I have seen so many problems with the Spektrum that I would not rule it out but I think it is in the ESC itself or the connections or power supply.
The truth is that you will have to just eliminate one thing at a time.