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How to ensure Pixhawk reaches a waypoint's altitude before flying on?

Posted by Bill Salopek on February 1, 2016 at 7:17am

Hi guys...

I fly in mountainous terrain in New Mexico.

I'd like to ensure that my F550 reaches a waypoint altitude before moving on to the next waypoint (more important of course flying UP along rising terrain than the other way around).

Couple questions:

1) Does the Pixhawk do this by default? Perhaps adjusting horizontal speed between waypoints so as to reach the next waypoint's altitude at the same time that next waypoint is reached horizontally? (Seems to be a reasonable safety precaution.)

2) If not, how can I program a flight plan so as to guarantee reaching the next waypoint altitude before moving on?

Thanks...

--

Bill

P.S.  I have been searching high and low for a "complete feature list" of Pixhawk...I find "complete parameter list", and "release notes", but can't find a document that actually says what Pixhawk does in this or that scenario.  Does a document like that exist?  Thanks...

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Replies

  • T3
    Stephen Zidek February 3, 2016 at 9:29am

    Just put a takeoff command after each waypoint?  As far as I know, takeoff won't let the copter go to the next point until it has achieved the specified altitude.

    • Developer
      Bill Bonney > Stephen Zidek February 5, 2016 at 5:50am

      You don't need to do that, as explained in previous comments.

      Takeoff behaviour is the same as normal waypoint, the only difference in the code is that is uses the current location, and not set lat/lon.

  • Derek February 1, 2016 at 8:40am

    I think the "Verify height" option in the flight plan tab is supposed to use google earth topography to ensure your however many feet above the terrain, versus feet above launch site.

    Here's the page http://copter.ardupilot.com/wiki/common-planning-a-mission-with-way...

    • Bill Salopek > Derek February 1, 2016 at 2:22pm

      Derek,

      Yes indeed, "verify height" does add Google Earth terrain elevations to the altitude of the armed/takeoff spot.

      But what I want to know is will the copter adjust it's horizontal speed so as to actually REACH that waypoint's altitude?

      And if not, how can I create a flight plan that will not let the copter go past, say, waypoint 1, without first attaining waypoint 1's altitude.

      Thanks...

      --

      Bill

      • Derek > Bill Salopek February 2, 2016 at 4:12am

        I think its ascent will be regulated by a combination of its WPNAV_SPEED and WPNAV_SPEED_UP, as well as the acceleration versions of each. My guess, having not experimented with it, is the copter will rise at a function of those two summed. Say WPNAV_SPEED_UP is 1m/s and WPNAV_SPEED is 1m/s (and accels are the same), I would think the copter will travel at approx a 45 deg angle.

        Let x = ground and y = elevation, what you're probably asking is if the copter is flying fairly fast on the x axis, will it "get to the waypoint" on the x axis before attaining y. I think it can, then my guess is it'll travel nearly vertical (probably not what you want for traversing terrain). I think you're going to have to find velocities and accel's that obtain the wanted outcome.

        Could be wrong though! Guessing on most of this

      • Tony Heaton > Bill Salopek February 1, 2016 at 6:44pm

        Bill, I can only give you and educated guess from observation.  From my experience, I also flew in NM, Jemez Mountains (6600' to 9000' alt), NW of Albuquerque.  I now live in Florida.  It always appeared to me that my quad would reach the altitude at or before the waypoint was reached.  I never verified this with logs.  I also never made huge altitude changes between waypoints, especially when going up terrain.  It would suggest setting a mission in a wide open area and simulate what you would do in the mountainous terrain and then look at the logs to see if and when the the altitude and waypoints were reached.  One would need to read the code to find out what happens to the next WP if altitude is not reached for current WP.  I would hope it would not continue unless next WP is at or below current altitude.  A developer may be reading and can answer without us needing to read the code.  I haven't found an answer in several searches

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