Blogs

Angle of Attack and Sideslip angle estimation from ArduIMU V2+ and GPS data

Posted by Joseph Lum on November 29, 2010 at 12:29am

Hi, I'm wondering if there's a way to obtain AoA and sideslip angle information from GPS speed data? There is vertical speed and 3d speed so this would probably be able to give me an estimate of the angle of attack, but for sideslip, I would have to have the y-component of the speed. Is there a way to get this from GPS or the IMU unit?

I have also tried it for one whole day but am at a loss of how to get the information to be passed from ArduIMU V2+ to ArduPilot so that I can use XBee to transmit it wirelessly to my GCS. Any clues from any good samaritans out there?

Otherwise, I think I am left with integrating acceleration information from the IMU which will probably be susceptible to a lot of errors, and also since it depends on the 'initial conditions' the errors will accumulate continuously.. :( Any ideas on whether this is a feasible option at all?

E-mail me when people leave their comments –
Follow

You need to be a member of diydrones to add comments!

Join diydrones

Comments

  • Joseph Lum November 29, 2010 at 8:59pm
    Hi Hamish, Doug, Jimbo, Michael, thanks all for the help rendered!! I'll take a look at the available sensors for angle of attack and sideslip and try to wire them into my ArduPilot board.. Thanks again!
  • Michael Zaffuto November 29, 2010 at 6:53pm
    An AoA sensor was previously discussed briefly and resulted in this link to Charles River's Albatross

    This is his schematic: http://www.charlesriverrc.org/articles/asfwpp/lelke_alb1electronics...
    This is his AoA Sensor: http://www.charlesriverrc.org/articles/asfwpp/lelke_launch.htm

    Pressing "Back" and "Next" on his site will reveal additional info.

    His AoA sensor is a low friction vane with magnets exciting a HoneyWell 91SS12 Hall Effect sensor
    providing an analog output voltage to represent angle of attack.
  • Joseph Lum November 29, 2010 at 6:30pm
    Hmm, looks like I have to get a pot for these two readings.. If I'm using ArduPilot, how can I connect the potentiometer signals to my ArduPilot? There are R/C inputs and also servo outputs for the aircraft controls.. Can I use empty channels from these? Or do I have to use another microcontroller? The reason is that I need to synchronize the potentiometer readings to the same timer that I control the aircraft flaps so that I am able to get the dynamics of the aircraft..
  • Jimbo1981 November 29, 2010 at 9:29am
    Hey Joseph,
    I think you mean the flight path angle, because the angle of attack is the angle between the airflow and the wing cord. you can not get that from gps data. the flight path angle is always less, but this you can get from gps.
    And side slip is is not easy either! should read up wiki or something like that, because both these info's have nothing to do with gps data. GPS is not the instrument that is used in basic flying. It's extra info for position of the aircraft only
    Greet
  • Developer
    Doug Weibel November 29, 2010 at 7:06am
    Unless you are using a magnetometer ArduIMU uses gps ground course to correct for gyro drift in the yaw axis, so there is no way to get an instantaneous estimate of sideslip. Any sideslip is incorporated into the gyro drift correction such that the IMU's output gives you an estimate of ground course and not actual heading.
  • hamish November 29, 2010 at 2:59am
    y = v*sin(theta)

    y=sidespeed
    v=actual speed
    theta=angle between actual velocity and direction the plane is pointing

    Is what I would do for sideslip. And for AoA I would make myself a little vane connected to a pot, and stick it on the side of my plane. then read the pot value for a brilliantly accurate AoA.
This reply was deleted.