Hi. I have made some modifications to the MatrixPilot code to do tests on In flight tunable gain. If this is further refined, it will be possible to do tuning of P/D gains on roll, pitch and yaw axis while in flight. The idea is that the gains can be tuned with a spare button on your RC transmitter one after the other (separately) while you fly the plane in stabilized mode. The gain you want to tune is gradually increased until oscillation is seen at max desired airspeed and then reduced back somewhat to ensure stability on that axis with that gain. My code mods is a hack at the moment, but this is just to illustrate the concept.
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Hi. I have made some modifications to the MatrixPilot code to do tests on In flight tunable gain. If this is further refined, it will be possible to do tuning of P/D gains on roll, pitch and yaw axis while in flight. The idea is that the gains can be tuned with a spare button on your RC transmitter one after the other (separately) while you fly the plane in stabilized mode. The gain you want to tune is gradually increased until oscillation is seen at max desired airspeed and then reduced back somewhat to ensure stability on that axis with that gain. My code mods is a hack at the moment, but this is just to illustrate the concept.
Hi. I have finished the first prototype of the lightweight KFM3 wing for my UDB2 / Matrixpilot UAV. The wing is made entirely out of Polystyrene. The benfits of this wing are: wide AOA range, wider stable CG range since lift is produced farther back on the wing surface, no aileron reflex needed so lower aileron reflex drag. I will add vinglets to reduce wingtip vortexes and drag due to vortex leakage out from the rear KFM surfaces.
This design should also give a low wingloading for autopiloted photo missions in low speed.
I have made a USD 2,- handheld cutter head for the PWM controller desribed in my previous blog post. The handheld cutter is nice for trimming off edges and so on. The spring keeps the wire tensioned. The final version don't need a series dropping resistor as the PWM driver stage uses two FETs.
The controller has also has been tested on a vertical setup for cutting spacers to my KFM3 depron wings (below):
The cutter gives nice clean cuts for vertical cutting operations (below). Please note the fan that sucks gases out from the workpiece. This is very important because blue and red foam gives off fumes that are very toxic when they are melted.
The PWM controller outputs pulses and is configurable both in duty cycle and several other parameters (below).
Based on interest, I may make a kit available.
I have finished my Arduino based pulse width modulated (PWM) hot wire cutter controller. It allows precise USB or analog temperature control of a hot wire of length from 10cm to 2m for use with manual cutters or CNC based cutter. The PSU is extermal (battery or PSU) The 12v power is attached to the GND and + 12V terminals. The + to the hotwire is attached on the red terminal on the top. The current return thru the FET is connected to the black return terminal. An FTDI board can be attached to the Arduino thru the "programming window".
What do you think :) ?
Just wanted to inform you all that I have sucessfully modded and flown William Premerlani's UDB2 board (red board) with the invensys gryo board designed by Russell Duffy. The AP / stab code was MatrixPilot r466 and the planes were a Fun Jet and an Easystar clone (higher wingloading and with ailerons).
I have attached an Excel sheet that I made with the equations needed to design a barometric altitude sensor.
For lower altitudes and for small altitude deltas, one can assume that there is a linear relationship between pressure and altitude. Please see the attached Excel sheet for more details.
The SCP1000 pressure sensor seems like a very good candidate for a pressure sensor:
http://www.sparkfun.com/commerce/product_info.php?products_id=8161
The manufacturer gives these data:
Resolution: 3 Pascal (the fineness to which the sensor can be read - nothing to do do with the accuracy)
Relative accuracy (how close to the real pressure the sensor measurements are) over temp range +10C to +40C and 600 hPa to 1200 hPa: +/- 50 Pa. (It is not given in the datasheet if this is sensor to sensor or for the same sensor)
The manufacturer does not give noise data. However sources on the Internet may indicate that the sensor has an inherent noise of +/- 50 Pa.
Datasheet: http://www.sparkfun.com/datasheets/Components/SCP1000-D01.pdf
Sample code: http://www.sparkfun.com/datasheets/Components/SCP1000-D01.pdf
Another guy using the sensor for a variometer for paragliding: http://www.pixelproc.net/varios.html
The noise may be filtered out using an averaging filter however. Even a kalman filter and two sensors may be used.
baro_height_measurement_unit.xls
Here are some photos of my new pulse width modulated (PWM) hotwire foam cutter prototype.
Find more photos like this on DIY Drones
I use it for cutting foam of all types. Instead of moving the wire, I move the object to be cut. In this way it is possible to make straight and 90 degree cuts referenced to the base plate. I have drilled a hole in the baseplate for the hot wire to run thru.
My new airframe that can contain a lot of electronics will be cut by this cutter.
Its not CNC controlled, however the PWM controller can be used for a CNC controlled unit (plans in progress).
I use a power fet and a Atmel controller do do the PWM control. It can accept PWM commands from a host PC or analog input via a A/D port.
I got the telemetry and videolink azimut / elevation antenna tracker prototype up and running the other day. Here is a video of it (without antennas) when it receives ASCII commands from the test software running on my lab PC.
Find more videos like this on DIY Drones
Preliminary specs:
=================
720 degree azimut rotation range
>110 degree elevation rotation range
Relatively high torque
Ball bearings on shafts
Tracking controller programmable in C (Arduino based)
Commands to tracking controller can be sent via serial link from the ground control computer
ASCII based command protocol.
I have now written some initial telemetry code that extracts data from the internal data structures of the r,p,y code running on the UAV DevBoard. The code generates ASCII telemetry frames.
I will later make a binary telemetry frame format for better efficiency. If you have suggestions to the format, let me know. It would be nice to be compatible with the Ardustation.
What I would like to integrate in my UAV system in the future is an accurate height measurement unit (laser, radio, ultrasonic or pressure) as well as an airspeed indicator.
I will carry out some initial RF range testing later today or tonight.
This is fun!
I have now sucessfully sent rmat data from William Premierlanis green UAV dev board to the PC and displayed it with the pyton code developed by Brian Wolfe. I tailored the datagrams from the UAV Dev board to fit Brians format so I didnt have to recode the Python code.
Video:
I use a FTDI board attached to the spare serial port of the UAV Dev board. I send data as ints and the python code parses the data and converts to floats by dividing the modified Q15 format by 16384
The yaw axis drifts since the GPS is stationary, however its difficult to see that on this video. The accelleration compensated axes are stable due to the correction from the accellerometers.I have another video that I will post son that shows the drift of the yaw axis better. The yaw drift is no supprise by the way, as this system isn't supposed to give correct yaw information if the plane is stationary as it uses GPS for yaw correction. (The plane may drop to the ground if the groundspeed is zero unless the course is into headwind with airspeed over stall speed).
For a helicopter a three axis magnetic compass may be used for yaw correction. In fact I have a three axis electronic compass intended for use on my four rotor helicopter laying ready for some possible later testing if I get to dig deeper into the code.
(By the way look at the bottom board, not the red one hanging down. The red board is the UHF diversity RX for the telecommand link )
I plan on doing some flight testing with telemetry soon.
