Multiwii GPS Navigation Via Waypoints

[jimbo385]

I have tonight uploaded a work in progress firmware for Waypoint Navigation in Multiwii.

The full details can be found here http://www.multiwii.com/forum/viewtopic.php?f=8&t=3989

My experience and frustrations getting this code uploaded starts at around page 31 but If you';re interested, you must read the first post and I strongly recommend that you read all of the posts.

I';ve not flown it yet though! 

[barneyg]

Congrats on your progress.

personally I';ve shifted to eclipse for building/dev work ... much better IDE and there are some wiki/forum posts about setting it up.  The Arduino IDE sucks for projects of this complexity :)

I';m still completely in the dark about the 3dr bit ... I thought that stuff just worked (as long as the baud rates were set up right ... I really want to know what that new firmware does.

I';ve not been able to test this out due to not having a windows box to run the WinGui so I';m waiting for EosBandi to merge his stuff into  _shared and update the MultiWii Conf.

[jimbo385]

Took her out earlier in the wind and after a few trim adjustments for the wind, I was surprised!

  Acro works fine
  Horizon works fine
  GPS_HOLD worked really well!
  GPS_RTH started well but I bottled out!


In GOS_HOLD, the copter still wandered very slightly and changed altitude on its own. I put thus down to the conditions but I';m sure that I can tweak settings and get this better. Any suggestions?


GPS_RTH turned the copter towards home and struggled to get home which is when I bottled out! Any suggestions?

Altogether, a good session!

Cheers

[dirtyharry]

multiwii has toooo many variables for my brain so have made notes to remind myself of what does what.

These are  from various posts on the tinternet. I,ll post up my tricopter settings ones once I find them.

GPS stuff
Position Hold
The location error is calculated in centimeters for X (Longitude) and Y(Latitude) which is fed to a PI controller. The first stage of the controller takes the XY position error and decides how fast the copter should go to reach the correct location.
PI Controler - Poshold
Parameter: POSHOL_P is by default .4 or 30 cm/s for a 1m error. The desired rate maxes out at 150cm/s. This doesn';t limit the pitch of the copter, The rate controller will do what it takes to maintain this speed as it approaches the location.
Parameter: POSHOLD_I is used to overcome wind that may be pushing us away from our target. The higher the number the faster the copter will compensate. If your number is too high it will cause oscillations and overshoot.
PID Poshold Rate Control¶
Now that we have a desired rate, we need to change the copter pitch and roll to give us that rate of travel.
Parameter: POSHOLD_RATE_P are the proportional response. Your copter's optimal setting will depend on the weight and thrust of your engines. If your copter overshoots the target, lower this value.
Parameter: POSHOLD_RATE_I is set to 0 by default. Use this value to maintain tight control of the speed of the copter. If the copter is not achieving the speed it needs, this term will make up the difference by tilting the copter more or less.
Parameter: POSHOLD_RATE_D is the dampening part. If the value is too high you will see small oscillations in pitch or roll. Once the POSHOLD_RATE_P value is dialed in, start at 0, and increment slowly. You should see oscillations die down.

RTH and Navigation
The navigation (RTH) has only one PID control, the desired speed is directly calculated from the distance to the target and the defined speed constrains. The NAV_P, NAV_I and NAV_D parameters have the same functions as the POSHOLD_RATE.

POS = position hold = this works out how fast the copter will go to the "hold" position once it starts wandering off.
P= speed it needs to go depending on how far away it is  , range is 0-2.5  ,  0.1 = slow 0.5 = fast
I= how much to compensate for wind and "circling" the hold position , increase to reduce circling but not too much or copter will oscillate  . range = 0-2.5 typically set to 1.0-2.0

POSR = position hold rate = this takes the information from the POS and translates it into pitch and roll of the copter.

P= how much the copter reacts to the figures worked out in POS, increase until you start overshooting the "hold" position . Range = 0-25 typical value =2.0-6.0
I= how much it angles the multicopter to reach the speed worked out in POS , range = 0-2.5 typically 0.01-0.1 , keep it low
d= dampens the reactions with 0=no damping, increase till oscillations disappear , range 0.0-0.25 typically 0.045- 0.1

[dirtyharry]

[jimbo385]

Nice one DirtyHarry.

Good post!