Lighting up the tricopter

Tricopter - first flight FPV

FPV flying; well its a bit odd flying 'heads down' into a screen... took some tips from FliteTest and didn't try to switch between the screen and looking up :)

The video range is a bit suspect... but I have mounted the video Rx about 20cm from the transmitter!

Linky to youtube video

Tricopter maiden flight

Flying the tricopter during calm(er) spells on a gusty Sunday.

PIDs still need some tuning to get rid of the shakes, but this is surprisingly fly-able for a scratch build wot I made :) I attribute some of this to the SimonK flashed ESCs

Tricopter - electronics install and first (tethered) flight

740g flight weight (with 1800maH battery) just add GoPro and video TX :)

Complete Tricopter

 

First flight (securely tethered to a heavy table)

Tricopter design and build

This project started as an experiment in tilt-yaw steering (based on the excellent RC Explorer design from David Windestål). The first frame was made from a leftover quadcopter kit plate and aluminium 1/2 inch box section. It was small, cute, but not flyable!

First attempt proved difficult to tune and fly

The second iteration is currently in build, using wooden booms and an undertray battery/camera system to damp out video 'jello'.

Tricopter in plan - motors are 300mm from the centre of thrust

The rear tilt-able prop seemed to create a feedback wobble in the first model, so for this one I'm using a better servo and have mounted the heavy motor in line with the tilt hinge to reduce its moment. This should reduce the amount the tricopter reacts to tilting the rear prop, if I remember some basic mechanics... :o

All-up-weight with 1800mAH battery and video TX/GoPro is going to be around 900-950g. Dry weight without battery or video system should be around 550g. I'm thinking about drilling a few holes in the wooden booms to reduce weight further :D

Tail servo assembly.

Flight control board mounted on foamboard and four cubes of vibration damping foam. Hey, it might work!

Headcrab flying - with FPV!

First test flight with new landing legs, suspended battery/camera tray and FPV system installed.

It was dark, so testing was limited to the area lit by the back porch floodlight!

GPS + baro pressure (height) logging in the Bixler

Google Earth view of three flights - heights are logged from barometric pressure, lat lon from GPS

Platform was the Bixler trainer flown visually (hence lots of unexciting going round in circles!)

FPV - video tx/rx with DIY circular polarised antenna

Video transmitter using a GoPro camera, 5.8GHz video transmitter and a home made 'clover leaf' circular polarised antenna

Video receiver mounted on the radio control transmitter - matched 5.8GHz 'skew planar' circular polarised antenna to improve image reception

The video transmitter system mocked-up on my 'headcrab' quadcopter

rotary wing to fixed wing...

Flying the Bixler advanced trainer over Hampshire, UK with a HD wing cam from HobbyKing :)



Although this flight doesn't show it, I added 3-axis stabilisation using OpenAero and a redundant KK Multicopter control board. After some messing around with the KK flash tool software, I gave up and flashed the board from a command line using AVRdude

Headcrab quadcopter - Successful PID tuning!

So the last outing the 'Headcrab' had showed I had some vibration issues that may have been affecting the gyro performance... On reflection I think that the ESCs were not properly calibrated to the new motors I'd paired them with.

I wasn't very satisfied with the double sided foam attachment method for the flight controller board, so I made up a stand-off board with some scrap laser-cut plywood and used vibration damping foam to isolate it from the bolts holding the board up. Hopefully this will reduce the gyro interference to a manageable level using low-pass filtering in software. I also calibrated each ESC, just in case.

Vibration testing didn't look that much better, but I strung the quad' up to test its stability in acro mode and level mode:

This time the quad' looks rock solid at all power settings... the new Turnigy motors may be a tad overpowered :) I hope the ESCs and batteries can cope with the amps!

Batteries are on charge now. If I'm feeling brave tomorrow there may be a free-fright test :]

Tuning the 'Headcrab' quadcopter - bad vibrations

The 'Headcrab' quadcopter design now has an underslung battery carrier and vibration-damped camera mounting, thanks to some more laser-cut plywood from RazorLab. It's ready to fly! Almost!

But first, I needed to spend some quality time with the PID controller built into the MultiWii code. Basically, if this bit isn't right then the 'copter will be an un-flyable, rogue manhack that will not stop until it has lacerated its maker into mincemeat... or it crashes, or whatever...


PID tuning is a bit hit and miss (for me) but a nice safe way is to pop the 'copter on strings that hold it in one place and let it rotate about either the pitch or roll axis. This was working great, but I noticed that the quadcopter needed a constant pitch down input to stay level. As the throttle went up, more pitch down was needed to hold the drift in check. At this point I did the only sensible thing: put the quad away and thought about the problem for a few weeks (don't rush me!).

[Video of the gyro noise at different power settings - sad face]

I concluded that the likely cause was vibration (despite using foam tape and a big mass on the flight controller to try and damp things down). This is not a good sign. I already had concerns that the lovely body shape I'd created in Sketchup might act like a multi-modal resonator (kinda like how a guitar or violin amplifies vibrations).

Next stop is some serious damping efforts before I give up and try a different body plate design. I really wish sometimes that I could remember my lectures from university, especially the ones with control laws...

Building the 'headcrab' quadcopter

I've recently been busy building the new 'headcrab' quadcopter rather than fixing up the ol' X600 frame... The deployed frame is starting to take shape, with motors and ESCs (four yellow bits with all the wires coming out) mounted and connected up.
 

Here's the quad folded


The flight controller board will have a separate mounting plate that will be vibration-isolated from the main board. In addition, I've ordered another laser-cutting run to make a battery/camera mounting plate to hang underneath the quad, again using an anti-vibration mounting.

If this thing flies well and if anyone is interested, I'll put up the build steps and links to the laser cutting plans... but only if I see some comments from all three of you! :D

'Headcrab' quadcopter laser cut

Beer is a necessary component

Control board mount on the centre of gravity

Folded up - the quad stays in the unfolded position with friction - no more carrying a ratchet and a hex wrench!

Quadcopter flying in Devon

Quadcopter crash - Deja vu, again

Another random crash from my X600 quadcopter... Same as before, the quad oscillated nearly 90 degrees each way on an axis and lost height rapidly. Cutting power to save it from wrecking a motor, I heard a 'thunk' as it dropped onto a grassy slope out of my view. The quad suffered from another broken prop and a busted up aluminium arm where the wire landing gear broke out from its hole in the arm. I'm starting to wonder if the new avionics bay has an intermittent faulty connection.

Before the crash I did risk shooting some footage with my Wife's point-and-shoot camera mounted on the tripod thread on top of the quad... its nothing like this, but it does show that as a camera platform the quad isn't bad when a decent camera is fitted (R.I.P. Veho Muvi and its jelly vision)



New props ordered from Ebay - I might try out some wooden arms to replace the aluminium section arms, as a prototype for my scratch-build quad

Oh, and last time I weighed the X600 quadcopter with battery it came in at 1.2kg... a bit on the porky side...

Quadcopter redesign - the headcrab

After auguring in the 'copter, snapping a motor mount and losing my Veho Muvi camera in the bracken, grass and heather of Hampshire heathland, I decided to try designing my own quad frame...

[subsequent AAIB investigations showed that although pilot error was suggested by onlookers (my boy) the crash was most likely due to a wiring failure on a soldered bullet connector to one of the motors... with one phase gone the motor stopped working and the quad flipped]

The redesign was taking some time to finalise (ooh, what about a tricopter?), so I cobbled the X600 back together without the fibre board motor mounts, instead bolting and zip-tying the 'plus' shaped motor adapters that came with the kit onto the arms.

Meanwhile, the current design looks like this:

The aim is to have all the arms fold backwards (like an octopus?) to improve transportability. The arms will be held in place by friction by adjusting the pivot and stopper bolts so the top/bottom plates grip each arm with enough force to hold it still in flight, but still be able to fold up for transport (or a crash!)

The offset body/CG design also allows for an underslung battery tray that can double as a vibration damped camera mount.

Materials will likely be wood (I've some hardwood 1/2 inch sticks) and laser-cut plywood for the body plates and landing gear. Razorlab (UK Ponoko franchise) will be my source for cutting.

MORE videos from a quadcopter

Soon to appear - write up on the modification to the avionics bay and attempt to damp out some of the vibrations that are coming from the prop/motor shaft :(

More quadcopter videos

A quick post to link to the latest video from my quadcopter

First flight with new PID parameters

Hovering the Quad' was OK, but it still seemed to be unstable if a gust hit it or too much control was put in. This suggested the P term in the PID tuning was too large, causing oscillations if the difference between the commanded stick input and the measured attitude of the 'copter was too large. So I used the quadcopter on strings method to tune out P and I for pitch and roll (and had a stab at the yaw values). The results seemed good, so I found a nice large field in Devon, grabbed three battery packs and went flying...

PID values used were (low pass filter on the MPU-6050 set to 42Hz):

Roll and pitch: P=1.2 I=0.008 D=3
Yaw: P=2.5 I=0.016 D=0

Next step is to calibrate the auto-level!

Oh, and the crash at the end resulted in a snapped prop, and an excuse to buy lurid green and orange props :)

Quadcopter PID tuning and in-flight footage

Now that my quadcopter has its low-pass filter set on the accelerometer, I can fly again! This time I've put on a wee video camera from Veho to capture the quads-eye-view of the flight.

Still need to do some PID tuning as the quad reacts a bit too much to large disturbances, but its now controllable in a hover :)