Electrohub Spider + Flip 1.5 Problems

[NHS77]

Hi everyone

I just completed the build of my first multirotor based on the Electrohub with the Flip 1.5 and all the suggested parts from RTFQ. Went to maiden it yesterday with theses issues:

Before take off the tail wants to lift up first and once in the air the craft has a distinct forward drift. Trying to pitch backwards to correct this my quad starts to twitch in all axes if I go beyond half stick on the pitch, making it un-controllable. In addition pitch and roll seem extremely sluggish - I have to go pretty much full stick for anything to happen - resulting in said twitching (pitch, roll, yaw and throttle). I crashed it three times after a few seconds of flight and am at a loss how to fix this.

ESCs were calibrated using the CANNOT_FLY command in arduino, PID settings are standard as they come from RTFQ, ACC was calibrated in Multiwii Config (OSX version). CG is fine as well... The twitching happens in both acro and angle mode.

Any help would be appreciated!

 

[makattack]

Can you post a picture of the MultiWiiConf screen with your TX on, and connected to the RX, with a battery in the quad, and connected to the computer?

We need to see your RC Channels to see if the sticks at neutral, are at 1500. It would also be helpful to see (you can just type) the roll, pitch and yaw stick values at their extremes. This will also let us see the PIDS. Your TX doesn't have any expo or rate limits programmed in right? Also would be useful to know what TX/RX you are using.

Looks like a great build though! Welcome to the forums at FT and congratulations on a nice looking quad.

 

[Craftydan]

That camera seems VERY far forward for the CG to be just aft of the electrohub center . . . but you're measuring it, I'm just eyeballing it.

Assuming your board is functioning properly (a defective board can do interesting things) I'd usually associate the twitching behavior with vibration issues.

Have you balanced your props? do the motors spin up to a whir or a buzz? a little dissonance in the sound when maneuvering is ok, but if it's hovering a balanced power system should have a single breathy tone.

How is your board mounted? A hard mounting with bolts will transmit vibe straight to the sensors, where padding, foam mounting tape or isolation mounts will dampen the vibration.

How's the video? Cameras are SURPRISINGLY sensitive to vibe. If you know what to look for, you'll see vibe problems on the cam before you can hear them.


Apart from the twitching, the "unresponsiveness" may just be and issue with the gains and rates -- which are linked in multiwii (change the gains, you'll have to adjust the rates to suit) -- but settle the twitching first. If you're convinced vibe isn't an issue, Clearing the EEPROM and reloading the sketch couldn't hurt.

 

[brettp2004]

Looks like a clean build though. What did you use for the canopy?

 

[NHS77]

Thank you so much for your replies!

Here we go with the info you're asking for:

TX/RX: Spektrum DX5e & 6-Channel Lemon RX (I used the Spider with DX5e sketch from RTFQ)

CG: Holding the Electrohub at the outer mid points of the disks it seems well balanced. (May not be perfect but fairly close)

Props Balancing: Should be OK I think (although I don't have a fancy balancer) - will look into it again.

FC is mounted on foam tape...

Here's a link to the GoPro footage from the last flight (with sound for Craftydan). Notice towards the end how I try to pitch back and the twitching starts: https://www.youtube.com/watch?v=uBC5o6YthGk

How do I clear the EEPROM as suggested by Craftydan?

And finally the screenshots from Multiwii Config:



Hope you can make something from it - looking forward to your responses!

Greetings from Switzerland!

 

[Reuds]

Where did you get the canopy from? readytoflyquads?

 

[makattack]

I do agree with Dan in that it does sound like your CoG is too far forward. That would explain the forward drift. That said, if you move your battery back far enough for it to balance out, that should be ok. Your midpoints are close but a little too far from 1500. I personally adjust my subtrims on the transmitter until the mids are right on 1500 +-2

Not a big deal, but it also looks like you don't have the full extended ranges on your roll, pitch, yaw channels. I also like to get those to their full 1000/2000 by extending the channel/servo limits on the TX.

The default PID's (which it looks like you're using) will set you up for a fairly docile, easy flying, but not very responsive quad. You will probably need to tune it to your liking once you get it flying level in acro mode. I would not switch to any of the level (angle or horizon) modes until you get it flying steady in acro. When you switch to the level mode, you're just introducing more variables into the equation. The accelerometers and their calibration/trimming.

As for erasing the EEPROM, the Arduino IDE includes example sketches, one of which is an "EEPROM Erase" sketch. Just load it onto the flip, watch for the blue LED to come on, and reflash with the MultiWii software.

Hope this helps!

 

[Craftydan]

Ok, got a chance to look at the video . . .

The vibe is strong with this one.

I've seen worse, but it's pretty bad. Those props need to be balanced . . . but that's just a general rule -- the better you get and better your craft is tuned, the more and more you'll appreciate a clean frame


I'm wondering a few things:

- it looks like you're hunting on the throttle quite a bit (like you're playing chutes and ladders). there's a bit of skill you can pick up to help this, but cleaning the vibe on the frame will make this MUCH easier.

- how many layers of foam tape? one usually isn't enough. most people tend to settle on 2-3 layers.

- At 1:07, did you cut throttle or did it do that on it's own? If it did that on it's own, that's VERY bad, and you need to pick over your electrical connections on the power side.

- The twitching at 1:25 and 1:40 is bad. It does seem to be a little speed dependent -- it's not so much the angle that sets it off, but the momentum it's picked up. Vibration increases with airspeed . . . . so I'm back to blaming vibe.

- from the intermittent nature I'm wondering if there's something under the canopy that is jiggling around, or the canopy is loose enough to bump against the board -- anything that can transmit vibe that can lean/bump/rub against the board bypasses your vibration isolation.


Even needing to clean up the vibe, it's a good sanity check to clear the EEPROM and start fresh:

- open the arduino app,
- go to File>Examples>EEPROM>eeprom_clear
- upload the sketch.

- open and upload your working sketch

Multiwii should now be working from a clean slate.


ALL THAT BEING SAID . . . it's a nice build. You're heading the right direction. Work out this gremlin causing the jitter and jello and you'll have a fine craft to learn on.

 

[NHS77]

I do agree with Dan in that it does sound like your CoG is too far forward. That would explain the forward drift. That said, if you move your battery back far enough for it to balance out, that should be ok. Your midpoints are close but a little too far from 1500. I personally adjust my subtrims on the transmitter until the mids are right on 1500 +-2

Not a big deal, but it also looks like you don't have the full extended ranges on your roll, pitch, yaw channels. I also like to get those to their full 1000/2000 by extending the channel/servo limits on the TX.

Thanks a bunch! I'm wondering though: Can I even adjust the subtrims on my Spektrum DX5e? It doesn't have a menu or anything... Do you think an upgrade to a better TX (DX6 and up) would be a good idea?

 

[NHS77]

Ok, got a chance to look at the video . . .

The vibe is strong with this one.

I've seen worse, but it's pretty bad. Those props need to be balanced . . . but that's just a general rule -- the better you get and better your craft is tuned, the more and more you'll appreciate a clean frame

Thank you Dan for all the input! Indeed I only have one layer of foam under the FC. I'll look into everything, especially the vibe in the next few days and get back to you guys with good or bad news....

 

[makattack]

Ah right, I overlooked the part where you mentioned using a DX5e. That should be fine, especially since you also are using the DX5e version of the config, which should have the limits and midpoint set for you. Are your trim buttons centered on the DX5e? I think, again, Dan is correct... I also missed the youtube link you posted. I also see quite enough vibration that if the flight board wasn't well damped/isolated from, it could explain what you're seeing. Yeah, with the cover that makes everything look neat, it's hard to tell is something isn't banging against it (a wire, etc)

 

[NHS77]

Ah right, I overlooked the part where you mentioned using a DX5e. That should be fine, especially since you also are using the DX5e version of the config, which should have the limits and midpoint set for you. Are your trim buttons centered on the DX5e? I think, again, Dan is correct... I also missed the youtube link you posted. I also see quite enough vibration that if the flight board wasn't well damped/isolated from, it could explain what you're seeing. Yeah, with the cover that makes everything look neat, it's hard to tell is something isn't banging against it (a wire, etc)

I actually used the trims on the dx5e to get the midstick values closer to 1500. If they're centered midstick is around 1530. I'll give it a shot when they're centered and remove the cover and pull the camera back and tripple dampen the board and try to do a better job on the prop balancing...

 

[makattack]

You definitely want the midstick values to be at 1500 +-2 or 3, so if you center those trims, you may need to load up your ArduinoIDE and edit the config.h MIDRC value set it to 1530, if that's what centered trims give you. This way, the flight board knows what "center" is, otherwise, it's going to think you're inputting roll, pitch or yaw.

 

[bgfireguy92]

OK first off nice build. I built this exact setup with the flip 1.5 +baro & mag, but minus your camera boom. Now here's my thoughts on it and Dan correct me here if I'm wrong (Dan helped me with mine as well. Did you calibrate the endpoints on the throttle? Your low point to arm it is at 1152 which seems high (mine is at 1003) and your top end point seems a hair low (again mine is set for 2001). Doing that will help with your throttle control. RTF Quads has a good video on how to do that not only with your throttle but all your inputs click link and scroll all the way to bottom its labeled as radio setup. http://www.readytoflyquads.com/the-rtf-wiki

Second balance your props! I know your in Europe but hobbyking has a cheap halfway decent setup to do this and I looked it up in the European warehouse http://hobbyking.com/hobbyking/store/__77471__CNC_Alloy_Prop_Balancer_for_Propeller_EDF_Heli_Shaft_Blade_EU_Warehouse_.html

Now last where did you get that cover for your Electrohub? Ive been wanting to do that to mine for awhile now. PLEASE TELL ME!!!!

Hope this helps. Solve your throttle /vibration issues and then go after the sluggishness issues

 

[NHS77]

All right guys, here's what I did:

Did my best to balance the props better (Balancer is ordered...)
Put tripple foam tape under the board.
Removed the canopy to make sure it doesn't transfer vibes to the board.
Moved the camera approx 1.5 inches back. Same with the battery. If anything it feels a little tail heavy now.
Cleared the EEPROM and uploaded a fresh version of RTFQ's Spider DX5e sketch
Centered my trims on the DX5e resulting in a 1540-ish mid stick reading in Multiwii Conf
Dropped in those values for MIDRC in Arduino (and uploaded to the board again)

What I noticed while still on the bench: Motors start at around 1250 (about 1/4 stick) and max out at about 1750 (3/4 stick). I tried to mess with max/min throttle settings in Arduino but it didn't seem to make much of a difference, so I set them back to standard.

And here's the video of sadly another unsuccessful attempt: https://www.youtube.com/watch?v=tW3gS-XZRwU&feature=youtu.be

Once more the tail wanted to lift up first. Seeing that, I tried to see what happens on roll as well as pitch while at min throttle and still on the ground. That seemed to be more or less correct (although it wanted to also yaw a bit at the same time).

So I upped the throttle one click wanting to slowly find the point where it lifts off. All of a sudden it increased the throttle itself and flipped over.

I double checked that the motors are spinning the right way and that the correct props are mounted on each. So it can't be that. Im seriously starting to doubt the board and/or my TX for that matter.

Here's a picture without the cover after the crash:

 

[NHS77]

OK first off nice build. I built this exact setup with the flip 1.5 +baro & mag, but minus your camera boom. Now here's my thoughts on it and Dan correct me here if I'm wrong (Dan helped me with mine as well. Did you calibrate the endpoints on the throttle? Your low point to arm it is at 1152 which seems high (mine is at 1003) and your top end point seems a hair low (again mine is set for 2001). Doing that will help with your throttle control. RTF Quads has a good video on how to do that not only with your throttle but all your inputs click link and scroll all the way to bottom its labeled as radio setup. http://www.readytoflyquads.com/the-rtf-wiki

Second balance your props! I know your in Europe but hobbyking has a cheap halfway decent setup to do this and I looked it up in the European warehouse http://hobbyking.com/hobbyking/store/__77471__CNC_Alloy_Prop_Balancer_for_Propeller_EDF_Heli_Shaft_Blade_EU_Warehouse_.html

Now last where did you get that cover for your Electrohub? Ive been wanting to do that to mine for awhile now. PLEASE TELL ME!!!!

Hope this helps. Solve your throttle /vibration issues and then go after the sluggishness issues

Thanks for your comments. As mentioned in my last reply I did notice the throttle range as well... I'll check out the video right after this. Prop Balancer has already been ordered

As for the canopy: It's a transluscent plastic sphere that comes apart in the middle. I picked it up at the Swiss version of Home Depot in the home decorating section. I suppose the idea is to paint or glue stuff on it or fill it with something and use it as a decoration of sorts. I simply used one half, dremeled a few spaces on the rim to fit over the screws and wires and drilled three holes to strap it down with zip ties to the Ehub. And spray painted it of course.

Here's what they look like:

 

[makattack]

Ack, that's no good! You didn't change how things were connected from before right? You should check the config.h for the MINTHROTTLE value. I though Paul sets his defaults fairly high (1280 if I recall) but actually might be very close to your 1250 min throttle actual observed result. Actually, if you don't mind posting your config.h (can't as a direct attachment, but if you can upload it to dropbox or any number of free storage sites), we can take a look at it and offer suggestions.

 

[NHS77]

Ack, that's no good! You didn't change how things were connected from before right? You should check the config.h for the MINTHROTTLE value. I though Paul sets his defaults fairly high (1280 if I recall) but actually might be very close to your 1250 min throttle actual observed result. Actually, if you don't mind posting your config.h (can't as a direct attachment, but if you can upload it to dropbox or any number of free storage sites), we can take a look at it and offer suggestions.

Nope, nothing changed, didn't even unplug anything. Here's the link to the config.h as I "flew" it today: https://onedrive.live.com/redir?resid=CE254229E22E8109!5881&authkey=!AI-FUwAbwH-QdeY&ithint=file,h

Many thanks for your help!!!

 

[RichB]

What's the longest amount of time, in seconds, that this thing has ever been in the air?

 

[NHS77]

What's the longest amount of time, in seconds, that this thing has ever been in the air?

40 Sec. - maybe