Still missing.. and continuation

 

Yesterday I was out with a few relatives again to try and find the X550. No luck but must my posters are still hanging on the trees. My strongest guess is still that it's stuck in one of the trees at 15+ meters. However, due to the thick leafs it's quite hard to see anything. I'll have to wait for the leafs to fall off this fall and have a return trip to see if it's possible to spot it.

In the meanwhile if I get no word from any by-passers in a few weeks and as I still have a lot of parts and utilities, I think I'm going to start building a new quad. Almost half of what I've so far invested into this hobby are things such as battery chargers, spare parts, spare propellers and so on. This means I can probably put one together with not too much money.

What I'm missing are electronics and motors, which at most add up to a little more than $150. What I will further invest into and which would have saved my X550 that's done MIA is a radio linked telemetry system. It would have broadcasted it's position and I'd been able to find it easy. Now there are a few ways of solving the telemetry.

3DR $86

One way is the all expensive 3DR Radio Telemetry Kit seen to the right. It costs $86 and would probably do it's job in excellence. But as I'm still aiming for a shoestring budget, I'm sure there are alternatives.

Below are two low cost alternatives. They cost less than half of the original 3DR but should do the job. I've read a blog post regarding the APC220 about how to connect it properly. The third option I found yesterday browsing the web. I have no idea if it works but its branded as the 3DR with a different price so I guess it's a copy. But might still work as well as as the original.

3DR copy(?) $36

APC220 $33

In short, the X550 is still MIA

 

As the topic says, my X550 is still MIA. The day before today, I went to a library and produced these posters and have put a bunch of them up on trees in the area where it disappeared. Today I also filed a report to the local police department regarding my loss hoping that if someone turns it in, the report will be recognized. My hopes now stay with possible by-passers that happens to spot my quad and hopefully makes a phone call. 

And no, it's not my real phone number. It's juts prepaid number I acquired for the poster that I'll terminate once it's no longer required.

Stay tuned! All hopes aren't gone yet.

RTL fly away...

Yesterday I went away to find a field large enough to do some serious RTL (return to launch) and navigation testing. This requires space without trees too close. I found some nice fields and started testing. I successfully tested both RTL and three way point navigation before my last RTL went sour...

I flew quite far away as I previously had done and hit the RTL. The normal procedure then is for the quad to gain height to 15 meters, which is default. Then head to its home position and descend to about 3 meters and loiter. This time, instead of turning towards home, it started drifting to the left. I quickly intervened to save the quad by counter steering rightwards. The quad then rotated 90-180 degrees making the direction impossible to see from this distance and disappeared behind those trees according to the drawing. I then ran towards the highway and never saw it again.

I've since then been covering the grounds around the point where it disappeared for about 8 hours in total, checking trees and the ground where it might have crashed without result.

It might have kept going in that direction ending up on the other side of the field as the program does not include anything about landing, but keeping 15 meters until the destination has been reached. It might also have taken a short trip on the field, then turned around ending up somewhere else. I still think the highest possibility is that it sitting in one of those trees along the highway.

Later today or tomorrow, I'm going to print posters asking people to contact me if they find my quad. Hope that gives some results. At this point, I don't think I can afford a new one, which leaves me with a pile of spare parts that will not be used..

The new propellers was a success

Last night I tried out the new 8 inch propellers along with a fresh motor to replace the last faulty one. The x550 now spins like a cat and flies like a bird. I trimmed the flight controller for the new propellers, which wasn't all that much to change and it's very stable.

After the basic trimming I started working on navigation and RTL (return to launch). These also has a set of P, I and D parameters for navigation. There is a good guide over at the ArduCopter wiki. However, I didn't have much success in trimming the RTL and the x550 always overshot or navigated wrong. Once both batteries were drained, I figured out that I'd trimmed using wrong parameters, dooh! I had been trimming the HLD_LAT/LON instead of LOITER_LAT/LON. Will have to do this at some other point where I can find a good field to try it out at.

Link to the guide: https://code.google.com/p/arducopter/wiki/AC2_loiter_PID

Packages packages, more packages and washers

 

This came in the mail today. It's the order for new motors and 8 inch propellers. Having smaller propellers also eases the torch on the motors, which should lessen the overheat.

Now I might have come to a conclusion why my motors are failing. Due to the nature of aluminum, its quite weak. Now as the screws that hold the motor in place slightly bends the aluminum inwards, the top of the screw seem to get scewed too far into the motor and may cause a short circuit.

To counter this condition, I've bought some washers. These washers are used both to protect the aluminum from bending too far and also to put some distance between the top of the screw to the motor. I also bought some locking washers to keep the screws in place keeping them from coming loose due to vibrations.

This is the end result, now only time can tell if it works or not. Will try this out tonight along with the 8 inch propellers.

What does it weigh?

It's always essential to know what your model weighs. This model seem to weigh 1.3kg. My own estimations was 1.1kg given the weight info given for the parts used.

During test flights it have been able to sustain almost 16 minutes of flight time. That is using 1200kv motors with 9x4.7 propellers. I'm however intrigued to know what the data will be using the 8x4.7 propellers that are soon to arrive. I want to try the smaller propellers as I still feel that the motors are over performing given the model weight.

Malfunctioning motors

This is the video that I just recently submitted along with a support request to maybe get some new motors. You can see from the top left, to the bottom right motor 1, 2 and 3 not running properly.

Ultrasonic range finder part II: how it works

The now famous URF (ultrasonic range finder) has a bit more to tell than I wrote in my last post. One of my big questions was how it would interact with the on-board barometer. As any technical person would understand, is that at some point there will be some kind of conflict as these sensors will indicate different measures.

The URF is rather exact but only has a range of five meters. The barometer on the other hand has unlimited range but isn't that exact. In fact, its quite noisy and differ +/- 1-2 meters.

My experience is that the flight controller handles this in the way that, if the URF indicates different than last measurement then, it's the current height. Otherwise, the barometer is used. This way the URF is disregarded if it's too far from any object and the barometer takes over but also acts as an anti-collision sensor when coming in proximity to the ground.

What I'm still to experience is: What happens if the quad flies over trees? The barometer may indicate 20 meters, while the URF suddenly indicates 3 meters. What happens if it's programmed to hold at 20 meters? Does the quad bounce up 17 meters further? Interesting question.

Issues that I've experienced installing the sensor is that on my device, the Echo and Trigger labels are the wrong way around. On the flight controller that I'm using, the Multiwii MegaPirate board I'm supposed to connect echo to pin 9 and trigger to pin 10. That didn't work unless I connected them the other way around ;).

It became self aware

Someone once said: -"Pictures or it didn't happen".

This is how to get prepared for flight. In addition to the quad and the transmitter, you need a laptop.

Everything is by this time wired. That's why you see the green light on the flight controller. It indicates that the GPS reports that it is locked on to a fixed position. The sonar is also connected and reports correctly.

 

Another picture..

So, you wanna see how it flies :) ? The video is rather short due to two factors.

• The battery of my mobile was at this time drained to 4%, hence keeping it short.
• The left down motor gets seriously overheated due to some fault. It may break down if its magnets gets loose. This could happen due to heat as they are glued on...

 Note that I show no hands as the quad loiters :)

Spare parts has arrived!

 

A spare HobbyKing X550 frame, which I'm going to do some DIY'ing to use to add another level/layer of stuff to my current frame. You'll see how it works out soonish.

Battery for the Turnigy transmitter and a li-po low voltage alarm. I must have misplaced my other alarm I ordered a while ago because I can't find it. This alarm does both show the level of charge and also sound an alarm when the charge drops below 3.3V. My ESC's are currently programmed to cut-off at 3V to not harm the battery. This will hopefully prevent any fatal crashes that could happen if the motors are cut in mid-air. Luckily, this hasn't happened yet. The only times I've encountered cut-offs are just after takeoff which resulted in a one meter free fall.

Ultrasonic range finder and stuff

My trials with the ultrasonic range finder shows that it doesn't get too much interference from the other electronics that are located close by. I still made the rookie mistake by connecting the Echo and Trigger cable the wrong way around and spent much time trying to figure out what was wrong until I figured it out. I've also tried to activate AltHold while having the range finder activated. Didn't see much difference in it's behavior but it'll be essential for automatic landings.

Also, yet another motor has started showing signs of problem. It's slaming back and forth before spinning up but doesn't seem too big of an issue with that. However, after running for a while, 5-7 minutes, it gets really hot while the other three motors stay cool. I'm wondering why I'm having these problems with the motors all the time :(. Therefore I've made another order for more spare motors and I also threw in some more propellers. This time 8 inch x 4.5 propellers. Will try and see if these propellers are more suitable for the quads weight.

It's alive again!

 

I found some replacement screws for the one I lost in a local DIY store :). This afternoon I've also done some test flying to see that everything is OK and it seems so.

Regarding the package of replacement stuff and battery I ordered, it arrived in Sweden this morning but haven't got any updates from package trackers since 4.53 this AM. Hopefully I'll get it tomorrow but my hopes aren't that high for that to happened. Tuesday would however be a more realistic time of arrival.

Next I'll do some more trimming on the AltHold and will also try the AutoLand function soonish :).

Stay tuned!

Order for spare parts

I decided to order another frame as spare part to replace the lost screw and to have more parts in case, or when things break.

While ordering the spare frame, I also threw in a chargeable battery for the transmitter. The transmitter uses eight batteries and replacing that will be somewhat costly in the long run. The battery might need some modification to the connector to fit my transmitter but I don't think it'll be an issue.

Today I received the tracking number, and as I ordered from the Germany warehouse, I hope the shipment will arrive soon.

One motor down..

Yesterday, I started trimming the AltHold function that relies on any altitude sensors. The sensor I have so far been using is the barometer, which is very noisy. That means it's less then perfect at holding it's altitude, but works +/- 1-2 meters.

Today, I thought of doing some more testing, maybe even try the AutoLand function as the AltHold seemed to work. However, after a few minutes of flying this happened..

 

One of the motors came off upon takeoff and took a piece of the radio antenna with it. The motors are fastened with two screws at the bottom and it seems as it came unscrewed, possibly due to vibrations. This seem to be the case for one other of the motors when I checked them all. It seems as checking the screws before going flying is a bullet on the pre-flight checklist.

Now, I only found one of the screws, which means, I have to get another somehow. Not sure if I should order a whole new frame as spare part or if I should try to find one in a local utility store. I'm going to try the second option tomorrow to see if they have any thing available that would work as a substitute.

Yes, there will be more videos. I have two that I filmed yesterday when doing some trimming but I haven't uploaded them to YouTube yet as my bandwidth is limited and the amount is not unlimited at the moment.

Update on the lost signal alarm

In short, don't use the throttle servo as I did. Apparently it doesn't move enough during flight so the alarm behaves as if the signal is lost from time to time. I'm now using something else, channel 4, whatever that is, but it works fine. Channel 3 is throttle.

Sensors, sensors

 

This is how I've mounted the ultrasonic range finder. It needs to be mounted some distance away from other electronics to avoid interference. I still don't know if this will work but it's a first try. Otherwise I'll have to find another solution. The range finder has a maximum range of five meters and should be pretty exact. I still have no clue how the flight controller will treat it's information in conjunction with it's on-board barometer. That's for the future to tell.

The other sensor, or should I say alarm, is a lost signal alarm. It reacts by emitting beeps after one minute of no change to the servo I've attached it to. It's currently attached to the throttle and so, if I don't change the throttle for one minute, it'll start beeping. I'd say the theory is that if you don't move the stick for more then a minute, your signal should probably be lost. Anyhow, then after another minute, it'll sound a more than 85dB beep until it's regained signal. In theory you should then be able to find your model if it's crashed somewhere out of sight. Cheap insurance policy.

It has taken to the skies

 

[spot the shadow from the quad down to the right]

 

After painstakingly tuning P, I and D parameters in Mission Planner, it can now fly. This is a configuration part that I wasn't aware of until a few days ago, when I didn't understand why it was way too wobbly and always crashed. The reason was that my PID parameters was offside given the model, motor and propeller size I have. After some tuning using this guide, I was able to get it stable. There is still far to go when it comes to more autonomous flight but.. it flies!

Link to PID tuning guide.

Six weeks later

 

Six weeks ago, I ordered these items from Deal Extreme. Two weeks ago, I reported the package as lost and wanted an investigation into the possibility to get another package sent. However, the support department asked me to wait another week and here it is, the post office has done it's magic. Just wondering why some packages from China / Hong Kong arrive after nine days and some after six weeks. 

Anyway, to the right, a bluetooth to attach to the flight controller, which enables configuration and remote command both from a computer or smartphone. The Android app SteadiDrone enables remote control and the regular APM Mission Planner also allows for connection over bluetooth. The other thing is a USBISP thing that soldered to the Turnigy transmitter allows for firmware update. More on that in another post.