Autopilot phase 1 (stabilization & servo controller)
I’ve been slowly working on my own autopilot system for more than half a year. I spent most of my time gathering knowledge and components. The last few weeks I worked a bit more intense on the project and it paid off: the stabilisation and servo controller are finished. They have been tested successfully and proved to be reliable!
Schematic:
Now, what can my module do:
- Calibration on startup (defining min and max values for the sensors, and the neutral point)
- Manual mode: Pass transmitter signals to the servo’s
- Stabilized mode: Read the desired roll- and pitch angle from the transmitter sticks and stabilize the plane in those desired angles. This stabilization works with thermophiles. They sense the temperature difference between the ground and the sky.
- (mode is determined by a slider on the RC-transmitter)
Other features:
- Delta mixing is done in the microcontroller so it’s not required on the transmitter (makes it easier to read pitch and roll input signals seperately)
- DSP filtering. The PPM signal is taken from the receiver before any DSP-filtering is done, so we need to do it ourselves to eliminiate glitches. Features:
- Checks if every PPM frame has the same number of channels.
- Checks if every pulse in the PPM frame is within a valid range (1ms and 2ms).
- When a bad frame is received: keep the last valid positions. Go to failsafe positions after 2 seconds.
Planned features:
- Read input from UART instead of RC-transmitter (interfacing to other microcontroller or PC)
I tested the stabilization unit on a small delta wing (40cm span) because I see no use in testing it in an easystar :-)
Module on the bottom of the wing:
Sensors on top of the nose, slightly pointing up:
Now some showing off :-)
The stabilization works so well I can launch the plane with the transmitter on the ground! When I give full left, the plane understands this as “go as much left al long as you can still see the horizon”. Considering the IR-sensor lens of 100 degrees, this will probably be about 40-50 degrees.
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hi mate, i’ve seen infrared sensors used in quite a few uavs but never figured out what they are used for or how they work could you link me to a page with a explanation ? thanks :)
— tuna, 25 July 2007, 13:37 | #
Hi Tuna,
I find this paper on the sensors very usefull:
http://www.ctie.monash.edu.au/hargrave/horizon_sensing_autopilot.pdf
Maybe one day I’ll write a blog entry about it :-)
Tom
— Tom, 25 July 2007, 16:01 | #
Hi Tom,
Looks nice, would you mind sharing the code?
— Koen, 18 September 2007, 00:37 | #
Hi Koen,
I only have the not-yet-cleaned-up code with hard-coded default values for my system (CSS PICC4 code for PIC16/18). Email me if you want it.
— Tom, 22 September 2007, 15:55 | #
Dear Tom,
I found your blog looking for articles on how to stabilize a system based on thermopile sensing. I´m trying to stabilize a camera platform for aerial photografy and I want to use thermopile sensors. Can you please send me your code for the PIC? I´m not very practised on PID alghorithm programs…..
Thanks in advance and My Best Wishes with your autopilot project.
— Marcos, 1 January 2008, 20:18 | #
Hi there Tom, Congratulations for a magnificent work. I also would like to have a peek into your pic code and if could be so kind as pointing me to the thermopile sensors…
Thanks and best regards
— Luis Miguel Riacho, 3 March 2008, 15:00 | #
Hi Tom, I’ve come across your page many times and am amazed every time I see the clip. Now I would like to kindly ask you if you would like to send me the code for it? Thanks a lot in advance,
Cheers,
Hartwig
— Hartwig, 4 March 2008, 00:21 | #
Hi Tom.
Loks like your delta is a peach to fly. Well done with your project.
What complier do you like to use.
Can you send me the code for a peek.
Thanks
George
— George Talhelli, 15 March 2008, 19:29 | #
Hy,
Great job you-re doing.
Works great as far as I see
Mind to ask for the code? I doubt i’ll really help, I can’t use thermophiles in space, but whatever, maybe i use the stabilisation code.
Btw, for my project, htt://www.arca.ro the section about stabilo
niky666_2004@yahoo.com
— Dicu Nicolae, 10 June 2008, 15:37 | #
Hello, I would like to find out how you calculate the cener of gravity placement on a delta wing. Can you help me? Thanks for your time.
— Brent Saska, 19 March 2010, 02:28 | #