Tau Labs FUTABA, CC Throttle calibration and range problem

[Bartman]

I'm continuing to try to make an XAircraft X650 fly with my OpenPilot CC flight control board. Everything appears to be working now except for my throttle channel. Throuigh the calibration process I'm able to have GCS adjust itself to the throttle movement but when I llok at the values being displayed in the Flight Data page in the lower right corner, throttle starts at -1.0 and then requires almost the entire range of the throttle stick to ever reach a positive number and cause the motors to spool up. I've been able to remedy this by manually adjusting the throttle channel in the Input-Configuration tabs but maybe there's a better way. In the Input-Configuration tabs I was able to increase the minimum value to around 1850 so the range was then 1850 to 2047 and it was flyable but there was a large dead area in the bottom end of the sticks where the motors would go to idle and I came down rather hard at idle as a result.
Would anyone happen to have an idea to fix this problem?
The radio is a Futaba 9CHP with a PCM receiver (72 mHz) if it matters.
Thanks much,
Bart

 

[Bartman]

I didn't think of this earlier but while I was typing I had an idea. When I calibrated my controls I had my throttle trim set full closed throttle. I had enough throw in just the trim to trim the throttle value to just less than zero so my throttle response is now normal. I still had to advance the throttle min pulse to 1850 but it feels and sounds like normal throttle response.
Any reason this wouldn't be acceptable?
If not then it's time for dinner and a quick flight of the X-OP650

 

[Crash]

Why don't you post a screenshot of the input and output tabs.

It looks to me like whatever you are doing is trading away throttle resolution because the motor pulses aren't set right.

BTW, Don't pay attention to what the throttle stick shows on the controller gadget. It's misleading. Maybe James can explain more.

 

[Bartman]

Maybe tomorrow...................

 

[Crash]

Ouch....Sorry Bart. I guess you didn't see where Peabody/James said that "he wouldn't fly like that".

What happened?

 

[Bartman]

i flew it in the backyard and it jumped into the air but was marginally controllable, like flying with 90% expo. when it was almost completely out of control i jammed the throttle to keep from hitting the house and it did it's now typical 45 degree downline into the front yard. i was able to keep from hitting the house so maybe there was some little bit of control there.
so, yes, maybe James was right about it not being such a great idea to fly. in my own defense, the throttle was set up like this this afternoon and it flew ok but maybe I'm missing something and maybe that something is more important than I realize. ya think?!?

 

[Bartman]

regarding my decision to go fly............

http://www.youtube.com/watch?v=i37uttMA6Mc

 

[Crash]

Grab some coffee, some toe nail polish, and watch this:
http://vimeo.com/25839978

 

[Bartman]

if you look at James' video, when he goes to idle the red dot representing the left stick goes to about -60%. after calibrating, mine is way down at -90 to -100%.
@crash, can you look at your RC input screen? what do you show for the throttle range?
in the Flight Data area, what do you show for the throttle value at idle and how quickly does it exceed 0 when you move the stick forward? i have to move my stick almost full forward before the value exceeds zero. that is why i messed with the RC Input values.

interesting video though, if i had the thing flying it would have been nice to tune it at some point.

bart "Maybe I should be called Crash" C.

 

[Crash]

if you look at James' video, when he goes to idle the red dot representing the left stick goes to about -60%. after calibrating, mine is way down at -90 to -100%.
@crash, can you look at your RC input screen? what do you show for the throttle range?
in the Flight Data area, what do you show for the throttle value at idle and how quickly does it exceed 0 when you move the stick forward? i have to move my stick almost full forward before the value exceeds zero. that is why i messed with the RC Input values.

interesting video though, if i had the thing flying it would have been nice to tune it at some point.

bart "Maybe I should be called Crash" C.

...Sigh....
Do you need an app that can take a screen shot?
http://lightscreen.sourceforge.net/

 

[Bartman]

it looks like it's a Futaba thing. here's a reference from the OP forum

http://forums.openpilot.org/topic/5614-cc-board-throttle-un-linearity/page__view__findpost__p__18742

 

[peabody124]

Also the fact mine went to -60 versus -90 isn't terribly important. The important part is that my throttle goes negative pretty close to the bottom of the range, so I have most of the throttle range that is defined as positive.

 

[Bartman]

Reversing the throttle in the radio has definitely fixed the throttle calibration problem. Based on the information in the XAircraft wiki I'm pretty convinced that the ESC's want to range between 200 and 1200 and setting the channel ranges in the Output tab to 100 to 1300 has them working very well with fine adjustments available throughout the range of the throttle stick's movement. I wish it worked this well yesterday when I was getting ready to fly!!! To be fair, in case anyone assumed otherwise, it was entirely my fault that I didn't wait to work out my kinks and the OpenPilot board just did what it could with my flawed installation.
Thanks again for the help. When the parts arrive I should have a nice flying quad.
Bart

 

[Crash]

Reversing the throttle in the radio has definitely fixed the throttle calibration problem. Based on the information in the XAircraft wiki I'm pretty convinced that the ESC's want to range between 200 and 1200 and setting the channel ranges in the Output tab to 100 to 1300 has them working very well with fine adjustments available throughout the range of the throttle stick's movement. I wish it worked this well yesterday when I was getting ready to fly!!! To be fair, in case anyone assumed otherwise, it was entirely my fault that I didn't wait to work out my kinks and the OpenPilot board just did what it could with my flawed installation.
Thanks again for the help. When the parts arrive I should have a nice flying quad.
Bart

As I mentioned in the OP thread, I would rethink the 1300 value or at least do real life testing to see if your particular ESCs respond at that amount. The numbers must be realistic to what the ESCs can use because the CC board is going to expect that they are valid and will use them.

Also make sure the input throttle curve does not go to 100. I think that may have been changed in the later code to 90 or so. The reason is that you want some headroom for the CC to be able to control the copter at full throttle.

The two things above cost me two bent motor shafts and a prop in the 'early' days when I was doing full throttle launches.

 

[Bartman]

Thanks Crash.

Here's the comment from the XA wiki

• Ts: (start) Starting pulse width is 200us. It shall start the brushless motor equal to or more than 200us, functioning in a minimum output power. It will stop the motor when ESC receives signal less than 200us pulse width.
• Te: (end) Ending pulse width is 1200 us, ESC will output the maximum power when receiving signal equal to or more than 1200us pulse width. Pulse width between 200us and 1200us can be used for power tuning.

Am I reading it wrong or is it going to respond in the range of 200 to 1200?

 

[Crash]

Yea, that's what the Wiki says - 1200.

My point is that maybe they can go to 1300, maybe they can't. If the wiki is correct and they can't then your value of 1300 should be changed to something that is realistic for the XA ESCs.

In Dankers video, he sets his at 2000 IIRC. In my testing, I could not hear a speed difference above around 1850 for my ESCs so that's where I set mine. I did it by ear because I didn't have a tach at the time and it didn't occur to me that a watt meter could also be used to find where the ESCs reach full throttle.

 

[Bartman]

ok, i understand what you're saying now. i thought you were questioning the range i quoted from XA (200-1200)
thanks, it's working great now and should fly fine. i'm working on a video to show the conversion.
bart

 

[Crash]

it looks like it's a Futaba thing. here's a reference from the OP forum

http://forums.openpilot.org/topic/5614-cc-board-throttle-un-linearity/page__view__findpost__p__18742

FYI: In the 3 or 4 flight boards I have used, the Futaba throttle always has to be reversed.