FPV Drone Disaster Movie

Gaining confidence with the Quad copters, I decided to have a try a flying mine by FPV rather than line of site. Thing didn’t quite go according to plan, below are 2 videos of the same flight, the first is from the ground station with the telemetry, the second is from the quad itself, higher resolution, but without any telemetry readout.

Although the orientation was easier in FPV than line of site, I seemed to be spending more time trying to correct drifts and rolls rather than flying it. I suspect the cheap boards that we have purchased are a little lacking, the addition of accelerometers rather than just the giros may help to stabalise the quad and make it easier to fly in this way. Although there are plenty of other videos on the web which these boards are used and they fly beautifully, which does make me think that we have not mastered the settings of this board yet, and need some more practice. The full roll over at the end of the video is a bit perplexing. I did remove the goggles because I didn’t think I could land it safely FPV. The RSSI is showing a good signal at the receiver, I released the sticks and increased the power slightly with the intention that the giros would level the quad, but they didn’t. Just before this flight I did increase the ‘I’ factoring on the board, perhaps this was set to high (perhaps higher than the ‘P’ factor) and so the board into continuing to roll rather than correcting the roll. I increased this with the intention of trying to make the quad more stable, and slower for FPV.

Fortunately very little damage seems to have been done to the quad, 2 broken props and 1 slightly bent motor mount. It will fly again!

Flying on Autopilot (ardupilot)

A while ago Mr Mel mentioned autopilot systems, at the time I was having enough trouble flying at the best of time without teaching a machine to fly so I didn’t give the idea much time, but more recently I have looked into this.

The first system that I discovered instructions on was the Arduino system, which appears to be a very extensible modular system which appears to allow you to fit together various modules and sensors to build pretty much anything you want (http://en.wikipedia.org/wiki/Arduino). This seemed great, but looked like it would need a lot of time and effort to get a simple system working. Carrying on looking I found some proprietary systems which had proprietary price tags. Eventually I came across the arudpilot system which appears to be a nicely packaged and programmed autopilot system based on the arduino systems, and it wasn’t that expensive. So I purchased a ardupilot, GPS with compass and an OSD module for the telemetry and for about £50 or so everything was delivered.
Ardu-rawmavlink

The Mission planner software which is used to program the ardupilot is rather impressive, but also a bit daunting at first view.

missionplanner

once connected to the ardupilot it starts receiving telemetry information. So I need to start with the basics, I’ll move onto full mission planning when I’ve managed to get the basics working.

The ardupilot hardware will work as an autopilot for planes, cars, helicopters and various configurations of multi-copters. The first step was to install the Ardupilot firmware onto the device so that it has the basic information that will allow it to fly a plane. The next step is to hook it up to the radio and the planes control systems

ardu-in-catalina

The ardupilot has a split power system with the input and the output power separated in this way:

ArduPOwerRails

Since the bec on the Catalina’s ESCs was probably 3amp at the very most I decided to use a second bec. I know the ESCs will power all the servos, so this is connected to the output line and powers all the control surfaces, and I connected another 3amp bec to the radio which provides power for the radio and ardupilot, both connect to the same battery using a 2 to 1 XT60 connector.

I powered up the system and configured the radio top and bottom points as per these instructions: http://plane.ardupilot.com/wiki/arduplane-setup/first-time-apm-setup/ I setup a mix on the gear switch and the flaps which combined gave 6 positions for the flight mode control. These I have setup with the options, Manual, Stabilize, Fly By Wire A, Loiter, Return to Launch, and mode 6 appears to be locked to manual as the systems ‘failsafe’ option.

Finally I hooked up the mavlink telemetry to my FPV gear and checked the information that gives on the screen:

vlcsnap-2014-11-07-10h37m29s159

As you can see its quite a lot, I think I will have to try to reduce the amount of information shown on this screen as soon as I can get hold of the appropriate cable and configuration software.

So the next step will be to test fly it…

Unfortunately my ground station for some reason did not record. I did get higher resolution shots from the on board camera, but this didn’t give the telemetry. I am really disappointed by this, and will update this post as soon as I can get some ground station recording done.

First Flight

Loiter was engaged at 1:26, Return to launch appears to be engaged at about 2:05. The plane seemed to be heading rather far over the house and away so I bottled it and disengaged it and went back to manual at 2:37 back to loiter at 4:18 I think, then off and back to manual at 5:00. Then a bit of a bouncy landing.

Mr Scott also followed the catalina with his Riot, but because I didn’t know quite how the ardupilot would perform I did fly rather high which made following it a challenge. Also as with all the videos the low autumn sun plays havoc with the camera trying to expose the recording correctly

 

Second flight

At 49 seconds return to launch was engaged, the plane then flew itself until 2 minutes and then manual for a better landing.

Really happy with the way it worked, would have been happier if I had some telemetry recording from the ground station to know more about what was going on, but will get this next time. Once I have a bit more GPS information recorded I can also move onto full mission planning, setting waypoints, and ultimately takeoff and landing 🙂

 

Update:

Although it is very stuttery, here is the onboard with the on screen telemetry, I think the stuttering is because there is so much more on the screen, so the compression on the recorder is so much more difficult and the recorder isn’t great. But it gives a good idea of what happens when each of the modes are engaged.

Working from the top left downward is:

Air speed, Ground speed (I dont have an air speed sensor so not sure if this is accurate), Throttle, battery percent (battery sensor not connected), Climb rate, GPS satellites in view, current and battery voltage (again battery sensor not contected), Longitude and Latitude. Middle column shows Roll angle, home direction arrow, warning text, artificial horizon, RSSI (looks like a bomb, but is not connected) and telemetry heartbeat  at the bottom. Right hand column shows, home distance, home altitude, current altitude, stopwatch, windspeed (linked to the air and ground speed, not sure how accurate this is, looks about right for today), pitch angle, WP distance and direction (don’t know), current flight mode (manual, loiter, return to launch0 with current heading to the right of this, and the heading rose under this.

Update 30/11/2014

A slightly better onboard video

But an Awful landing!

Building a Quadcopter

A rotary wing aircraft that I can fly outdoors has been something that I’ve been wanting to try for a little while, I even priced up the required items to build a quadcopter on hobbyking, but then procrastinated about buying it until I spoke with Scott who fancied building one too. So I ordered 2 full sets of kit so we could both build one each.

The shopping list I had for each copter was:

1 x Q450 V3 fibre glass frame

1 x Hobbyking multi-rotor controller V3.0

1 x QBrain 4 x 25amp brushless ESC

4 x Turnigy 1000kv D2830-11 brushless motors

1 pack of 4 10×4.5 slow fly props clockwise

1 pack of 4 10×4.5 slow fly props counter clockwise

 

It all arrived, so I built up the frame putting a drop of thread lock on each of the screws, and attached the 4 motors to the end of each arm, again with thread lock. I connected each motor to the speed controller, and just to check everything worked plugged it into the controller board and receiver and powered up… Nothing happened… So I thought I’d better read the instructions. First the speed controller required calibrating to the radio, setting the top and bottom of the throttle throw. So I did this. The instructions for the hobbyking controller board were ‘sparse’ to say the least, I eventually found by trial and error that setting the throttle to lowest and the rudder full left seemed to initialise the controller board, then every thing sprang to life. I now know this is ‘disarming’ the nav board… As opposed to arming which is done by moving the rudder to the right. Still none the wiser as to what that is if anyone knows?

Of course the first thing I had to sort now was the order of the motors, this was actually in the hobbyking instructions, but the firmware which shipped with the board was for a quad with a motor in front, behind, left and right. I wanted an ‘X’ configuration with a motor front-right, front-left, back-right and back-left. Fortunately I had a USBasp connector to update the firmware on the board, so when I eventually found the firmware update utility I update this to the X configuration from the hobbyking site, change the order of each motor to its connection on the controller board, powered up, put in left rudder to start the board and then a little throttle. This time all the motors appeared to start, and adding aileron and elevator appeared to speed up and slow down the motors as I would expect.  All is going well, next was to check the motors are all spinning in the correct direction and with a helpful little image in the instructions this wasn’t too much of an issue by placing a finger on the side of the motor case to see which way my finger was pushed, then reversing 2 wires if it was spinning the wrong way.

black_x

 

So next is attaching all the bits to the frame. Reading advice from other copter builders all seem to say that the controller board needs to be damped from vibration, my setup with the single ESC would seem to be advantageous in this situation since I could attach the controller board to the top of the ESC case using foam tape, then the ESC to the frame using foam tape the weight of the ESC should then help to damp the controller board from the vibrations in the frame. Although the heat management may be affected by attaching this to the ESC. We shall find out the effect soon anyway.

So after tidying up all the cables and tying them down this is what my copter looks like:

20141106_222311

 

At this point I got a little cocky and decided to spin it up with the props attached to see if it will shuffle around the floor in the correct directions, yaw the right way, etc. So I put a little bit of throttle on, not enough to take off, but enough to start taking the weight, then just touched the rudder slightly and the copter launched and smashed into the TV. After I extracted it, I removed all the props again (replaced the broken ones) and turned all the giros to minimum, and reduced the rates on my transmitter to 50% (with the dual rates switch set so I can increase this if needed) and put some expo in too. Strangely the pots on the board seem to need to be turned clockwise to reduce the rates. Turning them this way gave the lowest change in motor speeds for any given input, this way seemed a little counter intuitive to me. But I now felt confident again and being even more careful now I put the props back on and tried again, this time success, although there is a lot of effect from the walls and floor generally it seemed to shuffle in the way I expected.

All put together, this is now how it all looks:

20141107_072711

I still need to put a bit of tape on the receiver antennas, but next stop… a field test.

At the field we noticed that the single cable that I’d seen used elsewhere actually cross connected the Ailerons and Elevators, although we had set everything up so that the motors were working correctly of course the controller board didn’t have the motors set up correctly, so the first test flight was extremely unstable, the giros sending the copter more and more out of control. This was corrected, we then needed to add a significant amount of trim on various axis, but after this the copter took off and was controllable, but still a little wobbly. We turned up the gain on the giros on the controller board, this improved stability, this is the resulting flight by Mr Scott:

I then flew a little higher and further, caught a bit of wind which started it swaying, because it was a bit further away it was difficult to tell which way it was swaying. I should have simply left it to the giros to sort itself out, but instead I lost my cool and knocked the power down which then made things worse and ultimately led to it crashing

20141109_130730

But I do take a lot of positives from the days testing. We managed to get some genuine flying time, the copter performed well and we did get a lot of information that we can take forwards and improve them and do better next time. And Scott managed to do all this without smashing his up which is even more of a plus so he can take it forwards without too much work.

Good fun… needs a bit of work  🙂

Update 30/11/2014

I mounted the FPV and OSD removed from the catalina when I updated to the Ardupilot, the following was flown Line Of Site, but recorded from the Ground Station

 

Range of a Full Range Receiver

This seems to be a question that is asked, but never really answered. The normal response is a full range receiver has enough range to work as far as you can see the plane. This was correct, but more recently we have been flying FPV which has allowed us to explore this question further, and with the GPS overlays have a reasonably accurate idea of the answer.

We have had 3 incidents which I based this post on, the first was the balsa E-Fair glider which was posted about here:

http://blog.smfc.co.uk/2014/06/fpv-and-taking-it-a-bit-too-far/

An AR400 full range receiver was installed in the glider which was correctly range tested to over 40 paces. At about 1 minute 10 seconds into the second flight control was temporarily lost, from the GPS coordinates this was calculated to be a little over 500 meters from the landing point.

The second example was a new video which was a flight of my polystyrene Catalina containing an AR6210 full range receiver (genuine not Chinese fakes which are about at the moment and correctly range tested):

At about 1 minute 19 seconds into the video control was temporarily lost, although the overlay data is not on this video since it was recorded on the camera not the ground station the distance from the landing strip was a little short of 1600 feet (somewhere just over 500 meters)

The third incident is a little less clear. It is Scott’s balsa Decathlon flight. This contained an Orange DSMX 8 channel full range receiver:

http://blog.smfc.co.uk/2014/08/the-decathlon-that-caused-a-marathon/

Although the wind was blowing the plane away from the strip and the video was lost here which means that there is no direct evidence that the control was lost this was at around 1600 feet from the strip.

So the range of a standard Spektrum DSM based full range receiver appears to be about 500 meters. When flying FPV the pilot does not point towards the plane, so the orientation of the transmitter aerial will not be optimal, and in both cases where control comes back, the plane rotates then control returns, so the direction of polarization of the signal also appears to be taking an effect. We have also seen a notable drop in range of the FPV video gear when it was fully contain within even a foam plane, so perhaps the range could be extended slightly by externalizing the antennas. It is also possible that interference has caused these radio brownouts, we have seen brownouts before, but since both of these control losses happened at about the same distance in opposite directions from the strip, this offers less credence to this theory. Even with all these considerations I cannot see them extending the range to 1Km or more as I have see quoted on the internet. For normal flight 500 meters appears to be about the range of vision to reasonably see and control what your plane is doing. Our 250mw FPV gear with circular polarised antennas also appears to have about this as a range, higher powered FPV gear may need longer range control radios.

Catalina and Updated OSD test flight

Mr Scott recently brought my attention to an excellent hobbyking deal of the Catalina at £50 it was a bit of a bargain for a PNF. When it arrived it was made of polystyrene which is not the best, I did replace a couple of servos, they seemed a bit iffy, and changed the props since the ones that came with the model wouldn’t sit correctly on the motors and vibrated. But the main reason for purchasing was because it had such a huge capacity inside, a low wing loading so it should be able to lift a moderate weight and twin engines ment that an FPV camera would have a nice clear view. I also came across a new piece of software for the mini-OSD that I bought, uOSD. Now that I had bought a USBasp connector and soldered the connectors onto my mini-OSD as per the instructions here: http://arxangelrc.blogspot.co.uk/2013/06/g-osd-excellence-osd-re-flashing-and-programming.html the uOSD software was super easy to customise what was on the screen and where it was and it looked pretty good too.

So on Sunday I loaded it all up and although I thought I would make a couple of test flight not via FPV since the equipment was loaded I recorded the flights anyway. On the screen you will see in the top left the powered up time and the RSSI signal strenght, top middle the total distance travelled in feet, home set and direction icons and maximum distance from home in feet. On the left is the speed (mph) with the maximum speed above it, in the middle is a direction to home indicator, on the right the altitude in feet with the max above it. At the bottom of the screen aside from the GPS coordinates there is the current battery voltage on the left (with an optional second battery voltage currently not connected), in the middle bearing to home, and distance to home in feet on the right is the number of GPS satellites currently in use.

Its quite a nice easy plane to fly, very light wing loading means it floats around in the wind a bit making landing with even a bit of cross wind a bit of a challenge. The transmitter aerial also could do with a bit more thought, at the moment it is sticking out on the left of the plane, so when the left side is closest to the field (home arrow points left) the picture is ok, pointing the opposite way the picture tends to break up. Nothing that can’t be fixed.

Hopefully next week we can give it a proper FPV test fly.

Not a good day for FPV

Although today was a beautiful day, and I was looking forward to trying the new FPV OSD that I didn’t get to try properly next time out due to problems with the GPS.

This time out it still took a little while to get a full GPS fix, but it did fix. This was the first flight, watch the received signal strength from the spectrum receiver:

So the faulty receiver swapped out and fly again:

Unfortunately that spelt the end of the Cub for today, but it will fly again