Hi all,
I wanted to ask some questions about my quad implementation but I thought that it would be polite to introduce myself and my quad first.
I started my first quad design because my wife and I (and two kids under 2) were planning a 2 week four wheel drive trip across the Simpson Desert in central Australia. For those not familiar with the Simpson Desert it is 550 km of desert, 1100 sand dunes to cross, and 3000 km round trip. The quad seemed like the perfect way to get a different perspective on the landscape.
I have been following DIY Drones for a while because I supervised a couple of Electrical and Electronic Engineering final year projects to develop an IMU for a basic auto pilot application. So I ordered an ARM 2 and a bunch of parts from Hobby King.
I started with a cheap frame but quickly realised that it wasn’t going to be easy to mount the ARM 2 so I decided to design and build my own, keeping the aluminium arms and motor mounts. I wasn’t overly happy with my first design but it did serve to introduce me to some of the basic tuning and setup required. It also made me realise how much electronics I was going to have to cram into the quad to do what I intended.
I quickly realised that my first frame was going to be very difficult to carry in a fully loaded 4WD so I redesigned the frame to fold up and be stored against the cargo barrier above the rear seats. I also added some room for a pitch gimbal on the GoPro I intended to use.
The final assembly looks like this:
Folded for travel:
And the pitch gimbal and GoPro:
The basic parameters for the quad are:
1.6 kg with GoPro
NTM Prop Drive Series 28-26A 1200kv / 250w
APC 12x3.8 Propellers
Hobbyking X550 Aluminum Spare Booms ( 2pcs red/2pcs black)
ZIPPY Flightmax 4000mAh 3S1P 20C
Fat Shark Predator RTF FPV Headset System w/Camera and 5.8G TX
I broke quiet a few prop’s so I am now using:
Slow Fly Electric Prop 1045 SF
In the end it took four full days from start to finish before I left on the trip so I had very little time to learn to fly a quad and optimise the tuning. I have flown RC gliders since I was 14 so I had some basics but this was the first time I had flown anything with a motor. The most challenging part of the process was the tuning. I have a good understanding of control theory as make use of it from time to time in my day job but the Wiki control loop diagrams don’t seem to be up to date. This made it difficult to understand how some of the parameters interact.
I didn’t get to develop my flying skills too much before I left and I only started to get comfortable flying FPV near my last flight of the trip. Unfortunately I missed one of my ESC connectors worked its way out and I crashed the quad after approximately 10 flights. I some good footage though. I will post a video when I get one cut together.
I would like to thank the DIY Drones community and everybody who contributed to the ARM 2 board!
Comments
Hi Leonard,
Hope all is well.
I'm curios to know if you have done any modifications to this original frame - I'm keep thinking about making another :)
Rick
Derek is correct. But the gopro isn't the best choice for the fpv camera. In high contrast situations it is hard to see. I have to set up the camera that came with the goggles because that should be much better. Using the gopro is good for framing the image though. If only I could fly well enough to do it effectivly :)
@Brian Boatright you can see the 3.5mm headphone style plug coming out of the GoPro at the top in the last picture. That is how you get video out on the GroPro and you can plug that into your Video Tx.
Did you use the Fat Shark camera or hook into the GoPro somehow for your FPV camera?
Lack of updated documentation is the biggest problem with APM software.
Hi Denis,
I used 3mm plywood from the local hardware store. It isn't the lightest but it is more than strong enough for this application. As I said this was a very quick build and I am still working out what I want from a frame. When I understand the issues I will build a glass and carbon moulded fuse like I do with gliders.
As for the tuning there is a video made by someone doing a basic tune (I don't have a link to it off hand). And there is the simulator in the quad wiki that is good for getting a feel of how each parameter effects performance. The problem I found is that I had to read between the lines in a few places and guess what the control loops are because they have been updated and improved but the wiki is a little behind I think. I am slowly working through the code so that I can be sure what they are but once I have I might do up a couple of diagrams, as much for me as for everybody else. The thing is that these loops will probably change again over time.
It would be very hard to define what effect the gain on the integral or differential values of the pid controller will do for a random airframe without a reasonable understanding of control theory. But the DIY Drones team does a good job of giving everybody a starting point and some basic tuning tips. My approach is to use Matlab models to optimise the values but that isn't something that is easy for everybody to do (or me for that matter). It will take me quiet a bit of time before I could confidently suggest how to make it easier for people to tune. It is a hard problem.
For tuning, I have the same question. I have no idea of tuning impact. It would be great if someone make a table what are tuning variable used for and what are the side effect (with vidéo eventually).
As a beginner, I use a lot the altitude hold mode. It helps a lot.