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Home Position - Is this correct?
  • ptaylor999
    I've posted about this once before, but have made a recent discovery that might change everything, so I thought I'd throw this out there to see if anyone might know.

    My original issue is that I want my Home Position switch to work properly, but I can't seem to make that happen. I previously thought that hitting the switch would throw the gimbal into a different yaw position every time. However, what I've recently noticed is that, when I throw that switch, the gimbal resets itself to the initial position it was in when the gimbal was turned on, regardless of the orientation of the copter. So, if the gimbal was pointing due south when I powered up the gimbal, and I yaw the copter (gimbal is in follow mode) 90 degrees to the right and hit the Home Position switch, the gimbal will aim itself due south, no matter which direction the copter is pointing. It took me a while to put this together, but now that I have, I've noticed that this is actually very consistent behavior. It does it every time!

    Unfortunately, that's not what I want. I really need the Home Position switch to re-orient the gimbal so that it's pointing forward relative to the copter. That makes sense, right?

    So, is this current behavior correct? Am I asking too much of the board to want the gimbal to reset to pointing forward in relation to the copter? Or am I doing something wrong?
  • Garug
    How would the gimbal know to what direction the copter is heading?

    If it is encoder gimbal, then it knows, but I am not sure where encoder gimbal goes on home button press.

    The potentiometer modification sets the gimbal position related to airframe http://www.rcgroups.com/forums/showthread.php?t=2243241
    But it does not affect home button functionality, it must be set differently. There can be a mode that does not use the potentiometer and one that does. the one that does will set the gimbal heading to multicopter heading.
  • ptaylor999
    So, are you saying that the behavior I am currently seeing is correct?

    Your potentiometer mod sounds fascinating, but I have no idea how to adapt it into the system so that my Home Position button resets according to craft orientation.
  • Garug
    Yes, and the gyros will anyway drift. It could maybe be possible to set frame IMU above yaw and it could possible with some FW and some settings work as you like (reasonably reliable) without encoders or potentiometer, but I have no experience on this.

    The potentiometer modification does not work with home button, but you can set a profile that uses potentiometer and the one that does not. The one that does will automatically go to gimbal heading same as multicopter heading (after the potentiometer is connected and oriented correctly.)

    Depending of your controller/FW, instead seeing different profiles you could also use the adj.vars settings, to control the returning speed and when it is 0 it should work as potentiometer is not connected. i.e. setting speed higher than 0 would put the gimbal to home.
  • ptaylor999
    Thanks for all the awesome info, Garug.

    I do believe I've discovered a solution, though it's a bit unconventional.

    While doing more research into this, I discovered that the latest version of the firmware added a functionality where the gimbal will reset its position, on all three axes, with the Motor On command. The question then became whether this reset would simply do the same thing as the Home Position command and ignore the copter orientation, or if it would somehow recurrent copter orientation into account. After creating a switch and testing it out on my bench, it seemed that it does in fact look at the copter yaw position. In fact, it resets all three axes to theit init position, relative to the copter, which is exactly what I want! I tested this new switch in the air a few hours ago, and threw many flying situations at it, and it is working perfectly. Finally!

    I have the switch mapped to my Taranis' SH, spring loaded, dual position switch, so that the down position turns off the motors (Motors Off), and the up position turns the motors back on (Motors On). Since its spring loaded I really just need to flip it, and voila, the gimbal resets to the forward position of the copter, no matter where the copter is pointed. In fact, I tried yawing the gimbal 270°, flipped the switch, and the gimbal took the short route back to zero.

    I know this is not the most elegant of solutions, and feels more like a hack than anything, but it is working where nothing else I tried would.

    My only question now is whether this tactic of switching the motors on and off could be bad for the motors themselves over time.
  • Garug
    It will cause no problems for the motor.
  • ptaylor999
    Great to hear. Thanks for your help, Garug.
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