More Fixes to the SK450

I am plagued by poor loiter on the SK450 and have made further changes to improve things:

1. Fixed the slop or wobble in the GPS mast.  It turns out that the cheap mounts rely on being able to screw down the knurled flange until the mast mount inside is snug.  However, a lot of them cannot be tightened.  I added a plastic washer from an old prop to the mast as shown and the wobble stopped.
2. The APM mount was maybe moving in flight, so I remounted it with the special vibration reducing foam rubber and I secured the USB cable better so it could not move the APM.
3. Added a little foam rubber inside the micro APM case to ensure the barometers were not getting fooled by the prop wash.
4. Wait 5 minutes after power on to get the GPS and all sensors stable before trying a flight.
5. Added some practice golf balls to the landing gear so they do not catch in the grass when taking off or landing.
   
6. I very carefully recalibrated the accelerometers, making sure that the quad was absolutely level during the first stage of calibration.  This made a HUGE difference versus my previous "it looks level" calibrations - the test flight was much beter with much less yaw and pitch on takeoff and during flight.
7. Made a stand out of a medium size plastic storage container as shown:

Fixed the Loiter

Well I fixed the Loiter problem, the quadcopter will now hold position and altitude on command.  The changes were detailed in the previous blog post

1. Put in a new GPS.  
2. Improve power feed to the controller and receiver by using a UBEC (battery eliminator) instead of the power feed from the ESCs.  
3. Get rid of extra wires in the controller wiring harness.
4. Performed an indoor test flight and analyzed logs.  
5. Performed an outdoor test flight which was successful.

I also included a parameter change:

- changed INS_MPU6K_FILTER from 0 to 20 to filter out barometer fluctuations

Don't Try Auto if You Cannot Loiter

Learned a new lesson yesterday, should not have needed to learn it, because it is obvious.

If your quadcopter cannot LOITER successfully, don't try an AUTO mission.

I headed over to the local "park" - more like a remote muddy field that the county calls a park - to fly my quad.  The plan was to check out AUTO mode with the program shown in the previous blog entry.  I forgot, or ignored the previous tests that showed that LOITER mode did not work well, the copter bobbed up and down and did not hold position.

So I try taking off in AUTO mode with no luck, then do a manual takeoff and flip the switch for Auto mode.  At first, things seemed OK, then the quad headed for the river, gaining altitude.  Before I could react, it was over the Potomac at about 75 feet, then it dipped below the tree line and I could not see it.  I flipped back to manual (Stabilize) control and thought "that quad is gone".  I hit the throttle to try and bring it back up above the trees and it appeared as a little speck in the distance.  I then was able to bring it back with some skillful (lucky) stick work and land it.  Was I ever lucky!

The saving grace is that it took some great video footage while on its semi-controlled mission.  Also, this is why you should not fly near people, as this could happen to you and someone could get hurt.

Here is the video:

Some Tips from the Meetup

I learned a few things at the Meetup that I will pass along.

• Flying with larger propellers will make your video smoother but make the quadcopter less maneuverable.  I have 10 inch props on my homebuilt but I could go to 12 inches.
• You cannot assign a separate channel to the AUTO function on your APM which triggers an autonomous mission.  AUTO is just a flight mode so it must be controlled by the same channel that allows you to use Stabilize or Loiter.  That was one of my questions that I got answered.
• There is a capability called "OpenTX" that allows you to program inexpensive radios to do almost anything.  The radio is the 9X which is available branded Turnigy, Flysky, etc. and costs $50 or so.  You can also add a board inside the transmitter to allow USB hookup, it is from Smartieparts and cost about $20.
• You can get plans to print a quadcopter frame using a 3D printer.

Flying The Quadcopter

The Quadcopter is flying well.

Yesterday I had some successful flights (see video above) but one crash landing that required some repairs - nothing major - a couple of new propellers and reattaching the GPS mount with glue.

Today I had some great flights in a park by the river with fabulous panoramic views under clear blue skies with little wind, but the camera stopped working so there is no footage.  I also tried the althold and loiter functions and they worked like a charm.

I am getting about 10 minutes of flying time with a 2200mah battery pack and I have ordered a 3000mah pack as a spare.  They take a while to recharge (a few hours).

First Flights with Camera

I managed to get some quadcopter test flights done with my Veho VCC-005 action camera attached, both indoors and outdoors.  You can see the results in the attached Youtube video.  I also checked out the Loiter and Althold modes by triggering them from the transmitter while in flight and they seemed to work well.