Non-Powered Glider

Hello, I don't know if this is the best category to post this but I figured I should start somewhere.

I have a recently purchased ArduPilot Mega w/ Airspeed and Magnetometer. I am installing this in a traditional glider with no motor.

The goal is to launch the glider from several thousand feet, and have it RTH. I am struggling with the MANY tuning settings to achieve the best glide ratio. Here is my list of questions, if anyone already has a config for a glider maybe thats a good place to start.

Do I need to enable this? //#define THROTTLE_OUT

How does ArduPilot Mega act with no motor/ESC connected?

When setting waypoints, I don't want to set an altitude, rather assuming the glider will glide well, I want it to get get to the waypoint at whatever altitude it can. The at the last waypoint, loiter or circle till I switch to manual.

The majority of the flight will always into a headwind, so how do I set:

//#define AIRSPEED_CRUISE

//#define AIRSPEED_FBW_MIN
//#define AIRSPEED_FBW_MAX

Again, maybe someone has already got some good starting configurations for a glider.

I'm also very interested in this...

I've really just started going through the Arduplane code, but from what I've got of it so far it LOOKS like navigation towards a waypoint is done by 2 dimensional bearing... so if it crosses the waypoint at a greater or lesser altitude it will still go on to the next waypoint...

But I've been chasing airspeed and altitude variables all over the code tonight and haven't exactly figured out where the code is dealing with getting to the waypoint's altitude. It APPEARS that pitch is used solely to maintain airspeed, if the airspeed sensor is present... so if your glider has an airspeed sensor then you should be fine to just keep setting all your waypoints with an altitude of ground level and the ardupilot should fly your course without problem... If you don't have it configured to use an airspeed sensor it looks like ardupilot defaults to using altitude to set the pitch... so your glider might dive inefficiently to try to get to the target... UNLESS you'd set up the minimum pitch angle to be equal to your angle of attack for a best distance glide....

You might be able to set up your aircraft settings so the minimum pitch was your best distance glide and your maximum pitch gave your slowest rate of descent glide angle... so you could set waypoints of 0 altitude for your glider to travel to them at best distance gliding and of 40000(or other absurdly high number) for your glider to travel to them at lowest rate of descent.

That hack would also work with the powered glider scenario I suppose... if you set 20m as the height of all waypoints after the first couple (which you'd set at 100m) but set your min pitch to your best glide ratio and your max pitch to your best climb ratio... then the glider would climb to 100m then glide back to 20 m and hold steady.

All of that said, I wouldn't fly based on MY recommendation just yet! I'm still very new to this. I'm just trying to help ask the right questions of someone more knowledgeable!

For someone more knowledgeable than me...

1. Am I totally off base with all of that? Does ardupilot navigate and check waypoints based on lon and lat only? Does it hold airspeed with pitch and altitude with throttle?

2. Does the ardupilot completely chop power if it determines that it's above the desired waypoint, as Frank was hoping it would?

In the end, I think it would be great to take the arduplane base and write an arduglider derivative... with the appropriate modes like 'powered ascent' 'glide and hold base altitude' 'glide and return to powered ascent at base altitude' and perhaps eventually routines that analyzed data to know when we'd found a thermal or updraft and should circle to take advantage of it?

Art

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Cuddy January 12, 2012 at 11:21am

BUMP - I'm also running a project almost identical. Can someone with experience please chime in here if possible.

I've just ordered an APM2 however on looking at examples of code etc I have yet to see a non powered aircraft, there must be some people out there!

Many thanks
Art Whaley December 24, 2011 at 8:57pm

I'm also very interested in this...

I've really just started going through the Arduplane code, but from what I've got of it so far it LOOKS like navigation towards a waypoint is done by 2 dimensional bearing... so if it crosses the waypoint at a greater or lesser altitude it will still go on to the next waypoint...

But I've been chasing airspeed and altitude variables all over the code tonight and haven't exactly figured out where the code is dealing with getting to the waypoint's altitude. It APPEARS that pitch is used solely to maintain airspeed, if the airspeed sensor is present... so if your glider has an airspeed sensor then you should be fine to just keep setting all your waypoints with an altitude of ground level and the ardupilot should fly your course without problem... If you don't have it configured to use an airspeed sensor it looks like ardupilot defaults to using altitude to set the pitch... so your glider might dive inefficiently to try to get to the target... UNLESS you'd set up the minimum pitch angle to be equal to your angle of attack for a best distance glide....

You might be able to set up your aircraft settings so the minimum pitch was your best distance glide and your maximum pitch gave your slowest rate of descent glide angle... so you could set waypoints of 0 altitude for your glider to travel to them at best distance gliding and of 40000(or other absurdly high number) for your glider to travel to them at lowest rate of descent.

That hack would also work with the powered glider scenario I suppose... if you set 20m as the height of all waypoints after the first couple (which you'd set at 100m) but set your min pitch to your best glide ratio and your max pitch to your best climb ratio... then the glider would climb to 100m then glide back to 20 m and hold steady.

All of that said, I wouldn't fly based on MY recommendation just yet! I'm still very new to this. I'm just trying to help ask the right questions of someone more knowledgeable!

For someone more knowledgeable than me...

1. Am I totally off base with all of that? Does ardupilot navigate and check waypoints based on lon and lat only? Does it hold airspeed with pitch and altitude with throttle?

2. Does the ardupilot completely chop power if it determines that it's above the desired waypoint, as Frank was hoping it would?

In the end, I think it would be great to take the arduplane base and write an arduglider derivative... with the appropriate modes like 'powered ascent' 'glide and hold base altitude' 'glide and return to powered ascent at base altitude' and perhaps eventually routines that analyzed data to know when we'd found a thermal or updraft and should circle to take advantage of it?

Art
Frank December 15, 2011 at 7:20am

Same thing here but with a powered glider, I only have 5 minutes of full throttle and wish to setup a glide only auto mode..any help? did you find a solution? I actually permit the autopilot to use only half the power, it do level flight at 30%. at 100% it climbs a lot and sucks too much power.

I need it to climb at start at full power to 100m than glide to the waypoints and only if goes under 20m use half the power.

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