I am not a Graupner expert, but can you disable the telemetry on one of the RX's so that only one is transmitting telemetry? This would seem to work as a solution also. Tabb
Hi Tabb, thanks for the idea. From what I read you can´t do that. Today I made a few tests with the Spectrum again - the problem with the asymmetry were the settings on the radio, those are eliminated. I couldn´t find any problem with the pulley and it seems the stuttering doesn´t appear when I am deliberately panning, using the radio. Only in "stabilized slew" when I move the copter on the boom and it bouces back. The slower the bounce gets the more evident the stuttering is. I also did some flight tests - from 70/100/100 to 70/140/140 without a real difference. The footage was as shaky as the one from the days before, even though I tightened the belts. The only progress was the pan, where the tightening of the pan servo pulley made a difference. The strangest thing: It seems that the footage is less jittery when I turn off the radians. I´ll try to go the gel route tomorrow as others have suggested.
I also searched the Graupner materials and couldn't find a way to disable the telemetry. Good thought though, Tabb. Wolfgang: Glad to hear you solved the asymmetry problem. By "stuttering" do you mean moving a bit, stopping, moving a bit, stopping....I've seen that. I've been experimenting with (a Futaba 8FG) and assigning different amounts of Exponential to a three position switch (0%, 40% and 60%). Also I've been experimenting with reducing the slew rate on the pan Radian sensor. What I think is happening is that the pan servo moves and the inertia in the gimbal causes a lag, then the pan servo stops and the gimbal overshoots...and the process repeats at what appears to be the natural resonance frequency of the cameral gimbal -- do you see that "stuttering" happening at more or less the same frequency as when the gimbal goes into oscillation because the gain is too high? JohnC (who wrote the Radian firmware) may well be able to elaborate on this? Ayup, JohnC, are you on this frequency? Andy.
Andy, thanks again for the input. I´ll try to make a short video today to show the stuttering. You sure have realized english is not my main language so it might be the wrong word all together ;-). It´s similar to what you´ve described though (without a real stop, just slowering down from what I remember). And yes, it seems to be the same frequency and your explanation sounds just about right. I´ve done that Expo thing with the Graupner MX-16 too, but with the Spectrum DX6i I already have some switches assigned - and there are only two position switches. Maybe I can "reprogram" my swith settings to at least get two different settings for pan and tilt.
Wolfgang: Trust me, your English is several orders of magnitude better than my German! Some of the things we see with the copters and the camera gimbals are hard for anyone to describe -- we're using words when really we should be using video or images. Given you're using a DX6i, then this thread showing how to use Mix might be helpful. Tabb: Any ideas on this kind of hesitating/shuddering/stuttering pan motion? I've certainly seen it and Wolfgang is seeing it too. I'm really not sure on the best way of resolving it. Thanks Andy.
Hahaha, thanks, Andy - but usually there is no need to talk or write German for a native English speaker :-D. Thanks for the link, Andy - that´s why I could set up my DX6i for Radian use - without really knowing what I´m doing though. I tried various other possibilities to change the switches but failed badly ;-).
Ah, but there is a need to read German when you work with Mikrokopter boards! I just wish I had studied German at school -- but they seemed more keen on teaching us Latin.... I'm sure it would have been useful if we had met any Roman Centurions.... num quid ilud negat. The documentation for the Graupner, Spektrum and Futaba transmitters and receivers is not very clear -- perhaps if you have grown up with radio-controlled models it is easier, but I did not -- and I suspect many Cinestar pilots did not, and the documentation assumes a lot of knowledge (e.g. about Mixes, Channels, etc.) Andy.
Hahahaha, oh yeah, Latin. They told us it´s good to learn Latin because when you know Latin it´s easier to learn other languages. Sounds as logic to me as the mixer settings on the Spektrum :-D. Write me a PM if you need anything in regard to MK-translation. I can give it a try, but I´m not a technician. You´ve done a lot for the community, I guess it´s time to give something back to you ;-).
The Spektrum is easier than Latin (at least for me) -- or as I think the word order would be: Spektrum for me than Latin easier is. (That sounds horribly like Yoda speaking). I will let you know regarding MK-translation. I appreciate the compliment regarding the community -- glad it's appreciated. Now let's figure out that damned stuttering pan! Andy.
Give credit, where credit is due ;-). OK, I´m back with the stuttering video - and a personal portrait :-D. It´s not as visible on the video as it is in reality (perhaps because of 25fps), but it should give you an idea. Yesterday I got rid of the o-rings and the two smaller carbon pieces in the dampening unit and added one and a half gel blocks per unit instead. Didn´t have the time to try it out yet, but it feels a lot different. Hopefully it wasn´t vainly. One more thing to mention off topic: I´m not sure if it is the best idea to use the purple thread locker loctite for the smallest screws. I had a hard time with my allen keys and finally went to buy one with a grip.
Curious, have you flown this setup? The type of movement in the clip you posted you will not usually get in flight?? Another issue you can run into is if the CineStar is extremely 'free' to rotate in the way it is hanging there wont be enough mass for the camera mount to stabilize against compared to in flight where the props and gyro fight to keep the heading of the CineStar. One way to test this is to put a firm hand on a boom and rotate the CineStar back and forth while keeping a firm grip to see if it changes. Best, Tabb
Hi Tabb, thanks a lot for your input, greatly appreciated. I did fly this exact setup before, but didn´t really do any pan movement, because I was mainly checking for roll - so you may be right, at least the part with the missing mass to stabilize against sounds physically logic to my limited knowledge. I´ll doublecheck with the firm hand and in flight. BTW: I hid this video from vimeo - I know most of the problems with devices like radian and cinestar are human errors, so I feel it doesn´t make sense to put the cat amongst the pigeons.
Wolfgang: Nice video -- and how on earth did you learn to speak English with such a good accent? A couple of comments: 1. I would set up the system so that the frameset (the booms/hubs) can freely rotate -- you have them constrained. If you use a single cord/string that will allow the whole assembly to rotate I suspect the dynamics will be closer to what will happen in flight -- as it is, you have to the frameset only able to do dampened harmonic motion and I wonder whether that is realistic. (This maybe restating what Tabb said). 2. Also, I noticed that you are using nylon screws for the boom clamps for attaching the landing gear. I was just curious why you chose to do that? Are they as strong as stainless steel or did you deliberately choose to make them a "weak link" to absorb energy.... Thanks Andy.
hahaha, you mean that latin accent? 1. I´ll check that - great that there is still room for improvement ;-) 2. I replaced some of the stainless steel screws because of weight (tried to choose the ones that don´t have to carry weight - so no, unfortunately they are not as strong as stainless steel). In Austria we have a law that restricts flying with machines heavier than 5kg (if higher you need an official permit which is pretty painfull e.g. for setup flights), so I need to stay beyond that. It saved me 100g all together - I still need a little more to be able to fly with the xc730 and still stay beyond 5kg - I´m looking into aluminium or probably titanium screws for the rest of the gimbal/cinestar. I did have some sort of weak link on my old MK OktoXL - mounting the landing gear with cable strap which worked once pretty well on a crash. But that wasn´t the reason in this setup.
No....the English accent. Regarding the screws: Understood. That makes sense. The 5 kg limit is an interesting one. I guess you have to get approved using a 4S 500 mAH battery and the smallest CX730 battery! Those titanium screws will be expensive! Andy.
Thanks, my next video will be very british ;-) You meant 4S 5000mAh, right? Thanks for the idea, you are absolutely right, I´m not sure if I want to reduce flight time even more. I´ve tried 5000mAh - there seems to be a bar in regard to flight time where it feels much more than it actually is. And oh yeah, the whole ride so far was expensive. Initially I thought 3.000€ would do the trick. A few more titanium screws will not make a huge difference anymore.
Sehr gut. Ich bin ein Engländer in Amerika leben. (Translation by Google, so I may have just told you I am sausage living on a balcony.... ) No, I was joking that you would have to use a 500 mAH battery to save weight for certification purposes! Seriously, that 5 kg limit is a real challenge for you. Andy.
Hahaha, that grammar was about the same as your translated latin sentence :-D. Oh man, didn´t get the joke - stupid me ;-). I´ll keep you updated about my findings.
OK, here we go. Unfortunately the firm grip with the hand didn't bring a change. As long as I move it slowly, the stuttering appears. Same in flight. Panning slowly results in stuttering. I had quite some wind today so I could only test in a limited area, but the tests with the gel weren't too successful. Same problem: Shaky video (perfectly keeping the angles though) when Radians are on, smoother video (loosing the angles - especially roll and tilt) when Radians are off. So for the moment I'd say it's not the o-rings that are causing the troubles. I'm at 70/100/100 and there don't seem a lot of change drastically increasing or decreasing gains. Starting to become frustrated - any ideas?
I agree. This is getting frustrating. Let's see if we can move or change the problem. Unless Tabb and/or JohnC contradict me, I would do an experiment. Swap over the tilt Radian sensor and servo with the pan Radian sensor and servo -- do the sensors first and test, then swap the servos second and test. (Oh, and don't be like me and forget to mark which are presently pan and tilt so you can become confused later! ) When you swap over the Radian sensors, does the problem change? If not, then swap over the servos. Does the problem change now? What I'm looking for is something that points us at the problem component. Is it a sensor or a servo? Let me know what you find. (Gruner Veltiner may ease the frustration.... ) Andy.