Due to the past 2-3 months of bad rainy weather and gusty winds, I've decided that it was time that I invested in a tool that will be able to give me preliminary understanding the flight control is a scientific way . That means I will have to acquire a mathematical model of the airframe and use the current hardware to form a In-The-Loop Simulation (HILS). My approach for this will be to use DATCOM to derive aerodynamics parameters then coding the equations in C. This will then be flashed unto a separate Atmega microcontroller and will talk to the the rest of the hardware via the serial interface . The accelerometers and gyroscope values (superimposed with errors and biases) will be then form part of the output from the airframe model which in turn will exercise the flight controller and mission controller. What's not sure yet is how to test completely the waypoint tracking algorithm without using the GPS hardware. One way was to have a simulated GPS module as part of t...

This one is going to be quite short. Yesterday was the turn of the heading error algorithm to be tested. This heading error is calculated based on the heading the between two waypoints and heading measurement from the GPS module. This error will then be fed into a the roll controller as an input for roll command to reduce it to zero. But for the roll controller to work accordingly, the input must be right and within certain bounds. Same as the previous ground test, waypoints were loaded unto the autopilot and serial debug data was monitored using my Asus TF101 Tablet. It's worth saying that I managed to get serial data output straight from the LINUX command line . So the command line integration with VIM is complete. So it takes approximately under 10sec to upload and start debugging data of the autopilot. Sweet! Anyway, it was found that the GPS accuracy should be considered at 10-12m. Anything less than that and you'll be running for trouble. That is not a real conc...

So after a period of absence of over a month (feel depressed everytime I say it), I got back into the groove of things. Decided not to wait to get back on the field to test the pitch and roll autopilot and decided to start working on the waypoint tracking algorithm . The advantage of having your own home with a garden is that you no longer struggle to get a GPS lock (There's no more concrete flats surrounding us yeah!!!). So got familiar with my gear again. Also decided to buy a piezo buzzer that could be used as a replacement of the serial monitor. The aim was to increase the intensity of sound as you got closer to the next waypoint. In such a way you will know if you're going the correct way. Decided to use GPS Visualizer to get waypoints on the property. Re-formatted the points into the code uploaded it onto the controller. It must add that I managed to successfully run arduino from the linux command line and use the program screen as a serial monitor. Not only is it m...

deadband diagram (Photo credit: Wikipedia ) Managed to squeeze another flight test on Sunday morning (the usual madness occurred afterwards). Had about 7 - 8 hand launches to test the pitch autopilot with the gyro measurements integrated in the PID loop . It was quite that some adjustment to the how these inputs are being used was needed. So after each landing, adjustment to the gains was made. The erratic nature of the control requires a deadband filter approach which would enable the airframe to settle on a particular flight path naturally (restoring motion). A crude logic was implemented and tested and seemed to work although further test will need to confirm such approach. From a kinematics point of view, it makes sense and prevents excessive servo control usage which decreases the life of the part dramatically. Once confirmation that the logic is sound, the same approach will be made on the roll and speed autopilots which will allow us in the next 2-3 weeks move towards...

We've been having quite bad (windy) weather that It has been almost impossible to get the glider up in the air to gather more flight data . But nonetheless, I managed to analyse the data that I have come to some interesting conclusion on the behaviour of the aircraft in flight. The post-filtering of the IMU euler angles prior to controller design only add approximately 4/10th of the second in lag (guestimate). The servo limiter which I set on all channels is which what a normal flight actuation is experienced (considering wind factors). It's quite clear from the graphs that GPS velocity is expected to change with aircraft pitch although the nature of the sensitivity over a 1Hz update was not expected. The noise factor in launch in both roll and pitch channels shows that an alternative method needs to be established for a take-off and landing autopilot mode. There seems to be a considerable lag in pitch servo input and pitch change. This makes sense for the fact that t...

Depicts a traditional PID controller. (Photo credit: Wikipedia ) I'm such an exciting right now. It's been over a year of putting this UAV glider with custom autopilot and electronics together and now we're at the pivotal stage. In-flight testing of autopilot and GPS waypoint tracking!! Decided to go for a flight test on Sunday morning before church (around 7am) eventhough I was performing the church band that morning (crazy I know). It was bitter cold but decided to push through. I must say that I realised that I need a small collapse table/stool to setup the instruments instead of the wet/moist ground. I was great to see that the transmitter code works as expected. There was no lag in the transmission of signals from transmitter -> autopilot -> servos. The turning of aircraft with rudder and elevator control was smooth and consistent. It was refreshing to see that the filtering algorithm worked well. Decided to test the roll autopilot first, this...