MegapirateNG vs. MultiWii

I've been reading up on forums on the progress of future releases for the MegaPirateNG code base. To my astonishment I soon found out that the main maintainer behind MegaPirateNG left the project to join the ArduPilot team. This means that currently MegaPirateNG isn't developed. A small project fork all tho seem to have been done by some enthusiasts. This is called megapirateng-add-ons ( https://code.google.com/p/megapirateng-add-ons/ ) and is a beta into MegaPirateNG 2.9.1. Some folks claim its superb while some clam it has serious bugs. Others tell to look into the MultiWii code base instead.

Today I tried out the MultiWii 2.2 code, which is the latest in it's branch. From the first look and feel, it feels like the quad is handling a lot more stable. This is before touching any PID parameter configurations. I've done some level flights and it feels really stable. I haven't figured out if it's possible to configure the controller to decelerate the quad on releasing any of the pitch or roll controls, which MegaPirate did by default. That behavior is very helpful for beginners.

The guide I used to get going with MultiWii can be obtained from this forum thread:
http://www.multi-rotor.co.uk/index.php?topic=411.0

This is my current configuration and a look at the MultiWii configuration program.

One detail I found very useful is the fully configurable mode selector. This can be used to combine several features to build your own flight modes instead of having to use any vendor supplied modes.

My configuration states that not using AUX1 should result in a level (angle) flight. Using AUX1, level, barometer to hold altitude, magnetometer to hold heading and GPS to hold position should be used. AUX3 is used in a similar fashion but invoking GPS return to home instead.

It's thereby possible to combine any of these features in any desired way. Further explanation can be obtained at the MultiWii wiki page.

Stay tuned for more information as I go along. I will try to test out the GPS return to home function rather soon.

More electronics

Doing some further research found that HobbyKing also features the 433MHz telemetry kit I found at GLB (GoodLuckBuy.com). Link to mentioned kit.

However, this kit comes with antennas that are optimized for 900MHz rather than 433MHz according to comments. Seem to be the same transmitter and receiver anyhow so if I choose to buy these, it will be from GLB.

Further browsing, I found a flight controller resembling the MultiWii/MegaPirate controller I previously used. This controller claims to be version 3 and seem to have improvements in the way the serial ports are made. Version 2 had three serial ports in the same physical port when this controller has separate physical ports for each serial port. I can't see any other differences looking at chip specifications.

MultiWii & MegaPirate v2.0

MWC Mega 3.0

If I can find that these are compatible, I'd rather choose the version 3 as soldering small wires are a pain when breaking out the serial ports.

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 ;).

Cirus All-In-One Multiwii and MegaPirage flight controller

Today I made my first firmware build and fired up the Multiwii flight controller for the first timer. Here is a small sample of the feedback I got when I tried it out.

Only a short update today as I haven't been up to a lot yet other than this. I need to buy some "helping hands" in to start soldering connectors onto those ESC's. It's a common tool used when soldering as you often need a pair of extra hands. You can buy them online at Banggood but I think I'll buy them at a local hardware store as they don't cost much more over here.

Things I forgot about

When I started listing the parts I needed for my quad, I forgot about one thing. How would I go about converting the 11.1V output from the battery pack into 5.5V input for my Multiwii flight controller? The question struck me a couple of days ago and was solved using a uBec. Simply, a thing that converts high input to a lower output.

The second thing I forgot about is a charger. I've ordered my shiny 5000mAh battery but nothing to charge it with. I decided to go with a Turnigy charger that can charge batteries with up to six cells.





As far as I know, everything should now be either still at the warehouse or somewhere between there and here. Time to wait.

The beginning

So, I've decided to get my self a hobby. Hobby hasn't ever really been an issue as computers always been at hand, however, by getting older, I need something new to focus the ever shrinking free time on.

Walkera LadyBird V2 FPV was my first quad RC, seen here to the right. Bought it from the good old banggood.com.

As I grew more interested in quads, I've now decided to build my own from parts that can be acquired online. I've therefore made my self a wishing list of the things I need to buy in order to build my UAV. And as always, budget is of the essence and I've decided on a shoestring budget.




This budget may however change during the project but I will try to keep it up to date with all parts I need for the UAV.

To comment on some of the parts that are in the list, the frame I've decided to go for is a light weight low budget frame, which I will probably buy two of to keep one as spare part. Light weight also means more payload.

This Multiwii and Megapirate All-In-One Flight Controller allows for autonomous flight from take-off, thorough way-points and onwards to the landing. It runs on the same software as the well-known but more expensive ArduPilot flight controller. Once again, shoestring budget.