helojerry
Posts: 102
Joined: 4/17/2008
From: Phoenix,
AZ, USA
Status: online
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quote:
ORIGINAL: dknovick
I was surprised by the 2k Hz frequency, a DC motor (with it's inertia) can't respond to those kind of changes!
Evidently, it does respond! to the average!! It is still low enough freq that I hear a squeal as I apply the throttle from zero. On model trains, that sound is objectionable so I think they use even higher frequencies.
quote:
The HoneyBee FP has two pots. One to adjust the steady state and one to adjust the gain in the rate gyro. Ours (on the F40) just seems to adjust the stead state. So for my case I can adjust the pot, and move the trim lever back closer to center (currently, almost to the far right). The equivalent of adjusting the length of the ball links for the swash plate, so you can recenter the trims.
This is inconsistent with your measurements, but consistent with the way the system seems to respond. I don't know how to reconcile that. From the scope measurement, the duty cycle barely changed with a full turn of the pot. This would indicate that it affects rate gain, not trim.
quote:
I did also check to rate gyro gain, and I couldn't see a difference when I was shaking the board (but it was hard to see). One easy way to see is to adjust the pot to it's extremes. If you need to adjust the trim tab to hold a heading, then the pot is adjusting the steady state. If the tail wags (or is slow to respond), then the pot is adjusting the rate gyro gain.
Agreed. The F40 manual I have says nothing about this.
A straight proportional gain on the rate feedback is only going respond to a yaw rate. When the yaw rate goes to zero, then you have no contribution from the gyro. It will not take out a DC error. The gyro may be fighting the yaw rate, but the gain is too low to stop it. If the gain is too high, then you get the tail wag. So it is going to be a compromise between having oscillations or having a steady state yaw rate. At a particular head speed, you should be able to adjust the trim tab to stop the motion, but if you change the throttle, then that requires a new trim setting. Now if it is really smart, then the controller could add in some yaw thrust for an increase in main throttle, but I'm kind of doubting that from what I'm reading. Also, we have different battery voltages, different motors, different pinions, even different tail boom lengths!! Lots of variables there!! If the controller was going to try to compensate for main throttle, it would have to work off commanded throttle position. It doesn't know you are using an 11.1 v battery!!(BTW, I assume that the MOSFET drives full battery voltage to the motor, not a regulated voltage.)
One other factor to consider is that the controller could read the pot setting one time during power up. But I think that is inconsistent with one of your early posts that says the tail motor speed changes in real time as you vary the pot setting. Again, this seems to contradict the Oscope data.
I seem to be getting just a bit of tail wag during hover with throttle steady. I have not adjusted the pot yet. I'm still working on more basic stuff like motors and batteries!
Later,
Jerry
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RE: Falcon 40 (Exceed heli) Forum - 
If I can answer any questions for you on this, I'll do my best 
