I would like to start off my first post in this series by briefly describing where I’ve been and where I’m going. Hopefully this will give a bit of context to help understand subsequent posts and hopefully will help put my engineering decisions in some context.
History of the World, Part 1
Somewhere around 2005 I became very interested in aerial robotics. I have always been an aviation enthusiast, I’ve built model airplanes since I was a kid, and I have been flying RC airplanes since high school. At the time I was working for the Univ. of Minnesota … Read the rest... >>
This is a project that was sponsored by NOAA to develop a fully marinized small UAS that could be deployed from a variety of small vessels, recovered in the water, and used for marine debris detection or wild life surveys.
The “Resolution 3” purpose built UAS airframe is just one of the really cool products to evolve out of this project.… Read the rest... >>
(If it was me, I’d click on the “watch on youtube” icon in the lower right corner and select 480p and go full screen — but that’s just me.)
Flying a continuous tight circle pattern around a fixed ground reference point is about the closest thing we can get to parking an airplane in flight. It isn’t too hard to do a lazy orbit around the point, but we want to keep the radius fixed, even if there is a wind. This means that as we fly around the perimeter of the circle we have to continually vary our bank … Read the rest... >>
In previous posts I’ve described the process of carefully modelling the basic geometry and mass properties of a UAS in YASim to provide a real time flight dynamics simulation of the aircraft in FlightGear. I also described how we carefully modelled the blended body shape of our UAS using airfoil plots and spline curves. These curves were then imported into MoI and used as the basis to generate a smooth, flowing, organic surface shape. MoI is able to export the model as a 3d triangle mesh in a variety of formats including 3ds.
MoI (Moment of Inspiration) is a really interesting 3d modelling tool. There are two things that separate it from other tools in my view.
1. It has a very simple and intuitive interface.
2. It has powerful and intuitive primatives for drawing and manipulating curves and 3d surfaces. For example MoI allows you to define 2d (or even 3d) curves and then stretch a 3d curved surface between your curved lines–possibly with additional guide curves to control the shape. Like with any tool, it takes a little thought, practice, and planning to break down the structure … Read the rest... >>
Dynamics (Physics) Modelling and Flight Simulation
There are many great tools available to help engineers design and develop new aircraft and flight control systems. One such tool is the flight simulator. More specifically: an open source flight simulation such as FlightGear. Being open-source FlightGear is flexible and adaptable and can be used to solve or explore new scenarios that a proprietary software applications may never have anticipated.
FlightGear + YASim
Here I describe the process of modelling a flying wing in FlightGear using the built in “YASim” physics engine.
Are you insane? Yes, but in a nice sort of way (I hope!) 🙂
Since I’ve already admitted to being insane, you won’t mind if I explain the back story that let up to my evil plot. I work with a small high tech company (ATI out of Wasilla Alaska … and yes if you were wondering, but no I haven’t met her myself.) Some of the things we do is develop a variety of UAS related technologies. One project involves developing a marinized (water proof) UAS that can be launched from a … Read the rest... >>
This is a little proof of concept video I just put together. The goal is to always keep my aircraft’s shadow in the field of view.
Equipment: Senior Telemaster. Fly-Cam-One-3 with built in pan/tilt. Sparkfun 6DOFv4 IMU (it was laying around so I used it.) Gumstix flight computer. Ardupilot used for controlling pan/tilt servos on the camera.
The flight is 100% manually piloted. Camera is 100% automatically pointed.
On board I am running a 15-state kalman filter for attitude estimation. The filter converges to “true” yaw angle independent of ground track, wind, and magnetometer. This is actually critical … Read the rest... >>
I am changing acronyms starting with this post. Previously I was calling this an SAS for “Stability Augmentation System” but someone pointed out that this is technically more of a CAS for “Command Augmentation System”.
SAS implies a direct connection between pilot input and control surface deflection with some additional stability augmentation mixed in. CAS implies that a flight computer is translating pilot inputs into a “request” and the flight computer then tries to satisfy that request, but there is no immediate direct mapping between stick deflection and control surface deflection.
1. We added some additional logic to slowly roll the wings to perfect level if the pilot puts the bank angle within +/- 10 degrees of level. It’s really hard to get it exact from a ground perspective, so the idea is to let the pilot get in the ball park and the system will take over and finish the job. Auto-leveling will only kick in after the pilot centers the stick so it doesn’t fight the pilot if the pilot is intending to bank the aircraft.