Taking Stephen's concept hexa into full autopilot mode

After dealing with the motor issues (0.5-1 degree off alignment on 3 motors), the hexa is now performing really well.

Here you can first see a little stabilize test. Excellent performance, quick compensation. There was 'some' wind here, about 2-3Bft. 

Then the first fully autopilot flight @ 60m high. Amazingly, the hexa just goes straight up as if there's no wind whatsoever. See the flight log in the end. Only one leg was deviated slightly probably due to some temporary wind gust. In this test I'm already using the 143g camera payload and the large battery. Current consumption was 15-19A during flight in wind. This makes it reasonably comparable to the hover test. After two flights, the stab test and some 10 mins on the ground for preparation I had 15.8V left in the battery without load.

This build is with the RCtimer motors and the slim props. So the concept as-is works, but I'm awaiting my new hobbyking motors @ 530kV which I intend to test with my 14x8 graupner props instead. This will probably draw a bit more current, taking away some endurance, but the hexa should have more thrust available that way.

Issues:

  • Taking over in manual had throttle set a bit too low. The hexa started falling, but I was high enough to recover. It did take 5-10 meters to do so and quite a bit of extra throttle. So; the hexa is indeed not coping well if you allow it to descend too rapidly.
  • Due to above, weights higher than 2600g need to be evaluated very carefully. I don't feel happy slapping another 400g battery on or some more 300g of payload with these motors and props. I think 3-3.5kg weight does require a change on the motors and props, since they're too big and produce too little thrust.
  • I didn't take any photos unfortunately, because the mission planner updated the night before. It replaced the way I did mission planning and it didn't send out signals to my relay pin A9. I need to investigate what changed and which parameters need to be set to use the new mode: a camera distance trigger. The new mode uses gps traveled distance and doesn't require 'action' waypoints. This saves a lot of space on eeprom and allows for longer flights. That needs investigation.
  • Yawing the craft around shouldn't be done too aggressively. It could lose altitude and it's clear that it becomes less stable.
  • Autopilot performance was very good. I'm still using all stock PID settings from apm.

Conclusion: Very happy. With the autopilot this machine works like a charm, but available thrust remains an issue of concern. I'm using a very gentle 1 m/s descent/ascent speed and 5 m/s forward speed.

Views: 230

Comment by Thorsten on October 2, 2013 at 3:19am

Gerard, I am curious concerning the flight time with your new motors. I was also thinking about switching to bigger ones but after some more flights I am asking myself if it is really needed. I had the hexa out for some auto missions as well as longer flights in stabilize mode. And it performs pretty well even with an AUW of 3010g. I also made some tests with yawing and, as far as it it possible with this hexa, aggressive flying. It didn't lose altitude but it hardly can gain altitude when yawing. Apart from this it flies absolutely ok. For sure you have to be careful with throttle when changing between modes. I almost forgot: I switched off most of the logs in APM and all logs in Droidplanner and have the feeling that it is more stable now.

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