This Thanksgiving day I’m thankful for many blessings: family, friends, neighbors, shelter, food, our siberian husky who lived 16 years, and many other things. The weather was nice Thanksgiving morning so I was thankful to have an hour to run out to the field first thing to do some flying.
On Thursday, November 22 (Thanksgiving day) my Senior Telemaster past an interesting milestone: 12 cumulative hours of fully autonomous flight. This may not sound like a whole lot, but it represents 58 separate flights over the span of 3 years. In every flight it has performed beautifully and majestically and … 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.
ATI has been developing a number of flight control system building blocks and we have been testing them on my Senior Telemeaster airframe. This week I decided to connect them up to create a simple SAS (stability augmentation system.)
Briefly, when flying with an SAS, the pilot is still 100% in manual control over the airplane, however we have inserted a flight computer in between the pilot control inputs and the control surface actuators. Rather than the pilot’s stick commands directly moving the control surfaces, the pilot stick commands are translated to roll and … Read the rest... >>
One of the most challenging aspects of autopilot setup is tuning the gains for a particular airframe. When the gains are tuned poorly, the aircraft my oscillate excessively, it may lag way behind the target pitch angle or roll angle or velocity, it may never reach the target values. Poorly tuned gains could destroy an airframe in a worst case scenario, but often people just live with non-optimal gains that aren’t great but work well enough to get the aircraft around the sky. It’s hard to know what gains to tune and why and a person could … Read the rest... >>
(Sep 4, 2010 edit: I’ve moved way beyond this todo list, we are on our 2nd and 3rd gen autopilot hardware now. The software has been totally revamped. Still, kind of fun to look back to see where we were a few years ago. Never did clean the gummy residue off the load struts though …)
Setup a heading hold mode and implement waypoint following.
Setup auto-throttle control module.
Install secondary “tapped PPM signal” receiver.
Install MaxStream radio modem.
Low priority: clean gummy sticker residue off the aluminum load struts.
While rummaging around my hard drive I stumbled on some early footage of our Senior Telemaster flying. This footage includes some of my earliest successful autonomous flight using the original MNAV sensor head (now discontinued.) There isn’t anything especially great about this footage, other than I love the way the Telemaster looks in the air, especially it’s “scale” take offs and landings. These videos date back to sometime in mid-summer 2007.
The following movie includes some take offs, landings, and some early autonomous flight. One thing that is purposely highlighted in this video is an MNAV firmware bug that would … Read the rest... >>