Tuning parameters for thermals

Hi everyone,

With my friend we built a solar powered glider (4m wingspan). Yesterday we made a 7 hours flight with 7800mah battery pack, the total load was 17500mah with solar cells.

It was great BUT, during the day the controler was fighting with thermals to regulate the altitude, what a waste of energy !

I tried to set the maximum sink to zero in TECS params but it didn't work. I'm sure there is a solution to let the plane taking altitude with thermals. The max climb max is set to 0,5m/s and it works great to limit the power and it is enought to lock the alti.

Maybe someone know how to let the plane free to climb but managing an altitude floor.

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  • Thank you, I will try this fork on another plane to test it. It is exately what we need. I hope it's not a too old version of arduplane.

    Gavin Greenwood said:

    Post a link to youtube! Great work guys! I'd check out ArduSoar firmwareon gitHub. I used it for an automated soaring project and it went well.

  • Post a link to youtube! Great work guys! I'd check out ArduSoar firmwareon gitHub. I used it for an automated soaring project and it went well. 

  • Andreas Gazis said:

    My skywalker and bixler consume about 4 amps @ 3S so, let's say roughly 50W to hold altitude.

    How much does your motor draw?

    The cells should produce enough to keep it up when the sun is high. What about battery voltage? Was it generally close to full when the sun was high? Did you start noticing the voltage starting to drop at a particular time in the day or was it being slowly being drained throughout?

    Hi Andreas,

    For the altitude hold it supposed to consume 56W. In fact it consume only 37W !

    The weather was bad and we lauched at the morning so the battery voltage started to decrease until 14V. When the sun was high the voltage was 15,8V. Some cells are broken and it was cloudy. With small battery the key is when to lauch, not to early, not to late. The solar controller is a GENASUN GV10 li-ion.3702299915?profile=original

    Philipp Oettershagen

    Exactly, this is also what we set (and extended) in the "passively thermal compliant" version of TECS (and also the active thermal tracking variant of it) that we use on our Pixhawk- and solar-powered glider. It is really not that tough to adapt TECS in that way, although you need to potentially take care of integrator wind up (due to the altitude error that is not being corrected). See http://diydrones.com/profiles/blogs/ackling-the-european-refugee-cr... and the papers at http://www.atlantiksolar.ethz.ch/wp-content/downloads/publications/... .

    @Jean-Jacques: Great great work btw., love to see more of this!

    Hi Philipp, thank you for advice, we are following atlantiksolar project, great team. Your groundstation software looks nice but it's another subject.



  • paul riseborough said:

    The TECS algorithm has a control parameter labelled TECS_SPDWEIGHT which controls the ratio of speed and height error affecting the demanded pitch angle. If TECS_SPDWEIGHT is set to 2.0 then the demanded pitch angle is determined by 100% by airspeed errors and 0% by height errors (height errors will be controlled via throttle) which is what you want in a thermal. If set to 0.0 then the percentages are reversed and pitch will 100% be controlled by height error (not what you want). the default is 1.0 which provides a balance between the two.

    When set to 2.0 this will allow the plane to climb above the demanded height on min throttle when climbing in a thermal or descend at full throttle if in a large downdraft with the speed controlled to the set speed in both cases. Effectively the plane flies at a constant airspeed controlled by elevator and the throttle is used to control total energy. The downside is reduced precision in height control over-all and the possibility that TECS_TIME_CONST will need to be increased to get smooth height control. The TECS_PTCH_DAMP and TECS_THR_DAMP parameters can also be adjusted to compensate, but this is very trial and error unless you know how the algorithm works.

    Paul (original TECS developer)

    Exactly, this is also what we set (and extended) in the "passively thermal compliant" version of TECS (and also the active thermal tracking variant of it) that we use on our Pixhawk- and solar-powered glider. It is really not that tough to adapt TECS in that way, although you need to potentially take care of integrator wind up (due to the altitude error that is not being corrected). See http://diydrones.com/profiles/blogs/ackling-the-european-refugee-cr... and the papers at http://www.atlantiksolar.ethz.ch/wp-content/downloads/publications/... .

    @Jean-Jacques: Great great work btw., love to see more of this!

  • My skywalker and bixler consume about 4 amps @ 3S so, let's say roughly 50W to hold altitude.

    How much does your motor draw?

    The cells should produce enough to keep it up when the sun is high. What about battery voltage? Was it generally close to full when the sun was high? Did you start noticing the voltage starting to drop at a particular time in the day or was it being slowly being drained throughout?

  • The wings are populated by 48 solar cells (sunpower C60 maxeon). They are supposed to provide more than 3w each in good conditions. So, in theory it should provide something around 150w. But the solar charger efficiency, attitude off the plane, broken cells....

    For this particular flight in september with clouds:

    total load:17870mah (3DR power module data)

    total solar cells charge:6715 mah (frsky sensor data)

    battery capacity charged after flight: 7337mah

    This datas doesn't match. We need to calibrate amps meter of the power module and we think that the frsky current sensor don't work well because the value was not stable during flight.



    Andreas Gazis said:

    Wonderful, well done. How many kwh did your panels produce? How many were supplied by the battery and how many were consumed in total?

  • Wonderful, well done. How many kwh did your panels produce? How many were supplied by the battery and how many were consumed in total?

  • bravo les gars !

  • Cant wait for the details! :)

  • Developer

    Lovely !

This reply was deleted.

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