Thursday, November 13, 2014

GeoFence and Current Config

Turned on the GeoFence. The aircraft is small and I'm currently only flying LineOfSight (LoS) with no FPV (yet). So, I think this is reasonable.

GeoFence (current settings):
Type: Altitude and Circle
Action: RTL or Land
Max Altitude: 120m (400 ft is current suggested AMA Limit in USA)
Max Radius: 200m (656 ft or 1/8 mile)
RTL Altitude: 20m (65 ft. Note that this is the normal RTL altitude parameter)

Note: (added after later GPS trouble repaired): With the GeoFence enabled, the pre-arm checks will require you have GPS lock before Arming the vehicle (at all, in any mode). Consider controlling it with a TX switch or take laptop with MP to field every time. Leaving it enabled for now because I only fly Nova outside, and never fly without a minimal GPS-Lock. If I need to Arm it inside house for some reason, I'll have to switch GeoFence off first.

FrSky Taranis:
Switch B: Flight Timer-A
Switch D: Loiter, Stabilize, Altitude-Hold
Switch E: Off, Simple-Mode, Super-Simple-Mode (GPS)
Switch F: Off, RTL (ReturnToLaunch)

Android 4.x Tablet running DroidPlanner 1.x (GCS)

MissionPlanner: v1.3.11
ArduCopter: v3.1.12 (Nova stock)
FW: v120
FC: APM_v252_v2.0
Props: 8045 stock (8in x 4.5 pitch)
Battery: Turnigy LiPo 11.1v 2700mah 3s 20-30c (102x35x28mm)

Soft camera mount
Mobius 1080p camera
HK 3DR 915Mhz Telemetry Radio v2

Monday, November 10, 2014

Flight Testing

Due to the way our house is constructed, I never get any GPS satellites inside the house. I when into back-yard to test re-assembled Nova (like I usually do) before driving all the way to flying field. Out in the open, I couldn't get a GPS-Lock for 30 minutes (as in 0 sats and 100 hdop). Since I had just had quad apart, I thought problem might be on my end. According to other forum pilots, looks like today was bad day for good GPS. According to , there was a MCE that's going to be disrupting things for a while.

To estimate what GPS you should be getting:

After 30 minutes of sats=0, hdop=100 ... it just started working. I finally got a GPS-3D-Lock but hdop was still too high to Arm in Loiter Mode. Depending on yard location ... Sats 5-7 & hdop 2.3-6.7. I just Armed in Stabilize, did some AutoTrims and hovers and flew around in back-yard "obstacle-course" :)

Backyard hovering and flying.
GPS still not good, but at least getting something now.

The good news is that the vibration problems appear to be fixed (and hopefully also WobbleOfDeath). I didn't fly very much and wasn't very high, but no WoD was observed. For reference, the X-Y (red & green) Acceptable Range is -3 ~ +3. The Z (blue) Acceptable Range is -15 ~ -5.

All vibrations are well within acceptable levels. "Landing spikes" can be ignored.

Zoomed into a period (from above graph) for a closer look

Friday, November 7, 2014

Quadcopter and Multi-Rotor videos

They say a picture is worth a thousand words ... so how much for a video? I keep finding cool multi-rotor videos, so I thought I would link to them in this post. Most of these are geared toward sales and marketing. Videos geared toward "how-tos" are usually linked in the relevant posts themselves, throughout the blog. Most of these are better in HD with sound.

Here is the HobbyKing Quanum Nova marketing video.

You can tell Walkera has a large marketing budget, and wins the award for flashy/polished product videos. Be sure the sound is on and crank-up the YouTube resolution (gear icon) for these.

Hitler reacts reacts to a DJI Phantom flyaway. Remember that Quanum Nova is Arduino-based and RTC is short for "Return-to-China". After loosing 3 Phantoms, he decides to try a Blade 350. These are funny (sorta like Hogan's Heroes) and he reacts strongly to lots of things on YouTube (I never knew).

DHL is using quadcopters for deliveries. Video-1Video-2 and Video 3 (wish I had a team of people helping with pre-flight and watching my Telemetry).

The multi-rotors fly so well, the Internet is loaded with fly-away videos. Here is a Phantom fly-away over water and last minute RTL. Here is a Phantom-2 fly-away and eventual recovery. Here is a bunch of Fly-Aways in an Yahoo article (don't try this at home boys and girls).

RCUK edited this video with iMovie. Footage from his (custom APM-based) Walkera Scout X4 & GoPro.

Tuesday, November 4, 2014

Troubleshooting Wobble of Death (WoD)

With the help of the multi-rotor pilots in the RCGroups forums, it appears my WoD might be related to excessive airframe vibrations affecting the APM FlightController. While not much, as I've been adding extra weight to Nova (Camera Mount, Mobius Camera, Telemetry Radio, and finally Prop Guards) it seems to be getting worse and more frequent during flights. While I originally thought the WoD spells were a new development, as I review my flight-log-posts ... it has been occurring as far back as Flight #4.

Here is an IMU graph from Flight #7.

According to:

The X-Y (red & green) Acceptable Range is -3~+3. The Z (blue) Acceptable Range is -15 ~ -5. Even ignoring what appear to be "landing spikes" ... all vibrations are beyond acceptable levels.

The following items will be checked:
  1. Flight Controller mounting location
  2. Flight Controller mounting material and isolation from airframe
  3. Propeller Vibration and Balancing
1. PASSED. Currently, the Nova's FC is mounted Aft of CenterOfGravity or CenterOfFrame by about 10mm, and Port about 20mm (away from CenterLine). The FC still has the indicated side Forward. That side is parallel to the front side of quad, and is perpendicular in the aircraft. This was done in the beginning to facilitate mounting everything (FC, RX, and GPS) to PowerBoard without them touching each other, or any raised components on PowerBoard. While nothing is declared in official docs, according to some knowledgeable pilots in APM forum, there is no reason to re-mount FC in exact CG middle of quadcopter. After normal calibrations (including Accelerometer/Gyro) due to quadcopter's size and speed, there should not be a performance or dependability penalty for this slightly off-set mounting location.

Edit 2015-01: This turned out to be a FAIL. While it doesn't show as good on above graph (as others on this blog) ... X and Y should originate at 0. I think this can only happen when FC's gyro/accelerometer chip is in true middle of quad.

2a. PASSED - FAILED. Mounting needs to be around 10mm thick so that the side USB plug clears the RX, yet FC does not touch the top of body shell. As I examine the current layers of thin white foam tape, it seems very rigid. I have replaced it with a more appropriate material. I used two 1-inch sections (one on each end) of thick/plush (5mm) foam gyro mounting tape, two layers for 10mm thick. The FC mount is now plush and flexible (but still secure) and should be much better at isolating vibrations from FC and it's on-board instrumentation.

2b. PASSED - FAILED. Since the FC boards are not actually screwed down inside plastic case, there is some movement. I'm not sure, but I think the PCBs (and attached sensors) might have been vibrating inside case. Added small pieces of gyro foam-tape inside case (on sides ... not on top where barometer-foam piece is). Seems to work fine.

2c. PASSED. Inside the FC, (with it's two-PCB construction) I noticed the grounding metal case of the Micro-USB plug (on upper-PCB) is dangerously close to pins hanging-down from main power-header (from lower-PCB). Added a small piece of electrical-tape (3 layers thick) to prevent a short circuit or arcing.

3. PASSED. Balanced stock-white CX-20 8045 props with Dubro Prop Balancer. They needed little if any balancing so I really doubt they were causing any significant vibrations.

Other things I have done to Nova in this maintenance cycle:
  • Did another Accelerometer calibration since FC was moved. Hold quad very still and level/perpendicular at each stage.
  • Motor Test via MP/Terminal. They all run and sound ok.
  • Upgraded MissionPlanner to v1.3.10 and then to v1.3.11 a few days later
  • Set THR_MID parameter to 550.

Saturday, November 1, 2014

Flight #7 - Return to Flight

I took the repaired Nova to larger middle-school field to fly it. Winds were 10mph (with gusts) on a clear day. Flew 2 batteries (about 20 minutes total) and Nova survived with no damage. However, I seem to have a re-emergence of an old problem (now more frequent and pronounced) ... I think it's called Wobble of Death. It's not Ground Effect because I'm high-up, usually trying to hover. As I describe flights, assume all is ok (no wobble) unless I mention it. It happened about 5 times.

First flight was an AutoTrim. It seemed to really need it, so I did it twice (to finish with a good landing) and it worked fine.

Had a quick dhop of 1.8. I'm really liking the new Prop-Guards since if it tips over on landing a prop-strike is prevented. Even if it flips on landing (in short grass) it doesn't really bind props/motors.

Flight 1

Colors are the different Flight-Modes

On first battery I tested Stabilize, Loiter, AltHold, and RTL. I'm trying to remember now when the WoD happens. It seemed the Mode didn't matter (saw it during most of them). Wind gusts seem to cause it and while it almost flipped completely over a few times, it never actually did. Switching to Stabilize and making a course correction seemed to cure it.

On second battery I did another AutoTrim (just in case it would help WoD, but it didn't). Ran though all modes but I also tested Simple-Mode for the first time. Generally kinda weird but works fine and might come in handy. It works in Stabilize as well as AltHold (a welcome surprise).

I have Mobius video and logs to analyze. So, what causes Wobble of Death?