Ground Station Setup For Converged IoT Platform

Antenna Cluster Planning

For vertical diving proximity, use 3-D modeling of the mission scenario sketch. The example with Blender is in the picture on the right. The small matchbox at the lower left corner is the base station. And, based on the mission scenario, the RF-control/FPV antennas are arranged to prevent internal interference and obstructions.

For surface proximity, ground obstacles were viewed in mapping software. 

An example here is the low-tide exposed rock obstacles that is not shown in map satellite images.

Zooming in reveals an extra outcrop of rocks blocking LOS of the 1km proximity site. 

The land survey revealed a radio LOS dead zone packet during low tides. 

The aerial survey avoided the dead zones with large margin accordingly.

However, during the actual proximity mission, the high tide prompted acute steering toward the land. Without an on-location survey, the proximity mission during high tide failed (drone loss in the sea) with altered path obstacles.

The high-tide view of the crash site immediately after the craft loss shows no sandy shoreline.

The rendezvous plan record was photographed immediately after the crash. Actual dive at 6336, 6090 by memory.

On-location investigating the next morning during low tide to walk the failure path. First, the obstacle path based on landmarks (wind generator and distant house), marked red, is plotted.

The red lines and red curves rest on the obsticale rock outcrop that blocked RF signals.

The view of the ground station is used to identify the on-location perspectives.

On-location perspective and tracing the path of the blocking obstacle were identified at the location of the crash.

The failed mission path and the original planned path were plotted.

The off-course path on-location perspective is identified next to the original planned (good LOS throughout) one. The doggy footprint trace is identified as the crash location.

The large rock is a reliable visual landmark (unblocked) after a storm eroded sand and displaced pebble stones.

Then, the proximity mission succeeded in the next attempt.

The in-car battery and VRX were under a white food bag to cool them in the sun during the mission.

RF Transmitter Setup

The alternative micro sized transmitter module wiring pictured here.

The alternative Frsky R9M module can be set to output 500mW using alternative Taranis QX7's transmitter's regular power pins without external power source, as shown in this video,

This flight sequence rehearses the mission plan, diving from 330 feet east, 440 feet north, ground distance 550 feet, air distance 1000 feet, relative to ground station. 3 flips above the landing patch area. Level traversal between 330 feet east, 440 feet north, and 330 feet straight east.

Video Receiver Setup

The gaming monitor automatically adjusts its refresh rate to the highest the VRX can generate, as pictured here. There is no obvious way to change this.

The brand-new VRX cost is here.

In-Car Battery Charging

Fight batteries should be warmed/cooled with car vent before charging in cold/hot temperatures. When the car engine is offline, the car battery voltage has a slight drop, so the flight battery charger needs to be set to output below 1 amp to prevent low low-voltage cut-off during charging. The charger wires are hung by velcro stripes without a sticky backing.

TalentCell power bank YB1206000-USB has overheating protection. Keep it on the dashboard and plug in the charging plug year-round. If it is overheated by the sun, wait until it cools down to power on.

Walksnail 1S Lite USB Adapter Compatible With HD V2 Cameras.

As long as the plug is aligned with the socket to the left most pin when viewing from the right side of the craft toward the left side of the craft.

Box 17.5 Inches Long And 3 Inches Thick Or Larger

Cut the cardboard by the green line and the seam line pointed by the arrow, cutting the box in half while keeping a lid.

FPV Feed Flight Path Tracking

The raw FPV DVR recorded mp4 of the tail-spin crash with fishbowl optical illusion is saved at googledrive https://drive.google.com/file/d/1IchzErZsqhmW0qukS_ZLuJz3CpO4A27t .

When viewed in Android MX Player or the FPV headset, the last 3 frames used to track down the wreckage is not available frame-by-frame. A laptop or Chromebook with Avidemux.AppImage is needed to step in the last 3 frames. 

Avsaase/walksnail-osd-tool From Github 

Compatible with Chromebook for crash GPS searching with frame-by-frame video of a crash.

Anthwlock/untrunc From Github

Compatible with Chromebook for crash-interrupted VRX .mp4 file un-corrupting. The code is based on original ponchio/untrunc that has bug compatibility with Chromebook. 

  248  git clone --recurse-submodules https://github.com/ponchio/untrunc
  249  cd untrunc
  250  vim ../untrunc-master/README.md 
  251  ls
  252  cd libav/
  253  ls
  254  ./configure 
  255  sudo apt install yasm wget
  256  ./configure 
  257  make FF_VER=3.3.9
  258  vim ../untrunc-master/README.md 
  259  cd ../
  260  vim ../untrunc-master/README.md 
  261  grep g++ ../untrunc-master/README.md 
  262  vim ../untrunc-master/README.md 
  263  g++ -o untrunc -I./libav file.cpp main.cpp track.cpp atom.cpp codec_*.cpp codecstats.cpp codec.cpp mp4.cpp log.cpp 

-L./libav/libavformat -lavformat -L./libav/libavcodec -lavcodec -L./libav/libavresample -lavresample -L./libav/libavutil 

-lavutil -lpthread -lz -std=c++11

  264  sudo cp untrunc /usr/local/bin
  265  which untrunc
  266  untrunc
  305  cd ../../
  306  cd MyFiles/Downloads/
  307  untrunc ./AvatarS0086.mp4 ./AvatarS0087.mp4
  

Blade 180 - Oxy 210 Rotor Characteristics

Product source is ebay seller amain. Item "OXY2-081 OXY Heli Plastic Main Blade 210mm (Orange) (2)"

The airfoil profile is (NASA predecessor)NACA0015. The symmetrical airfoil is generally known to have the center of pressure CP at quarter blade width from the leading edge during cruise flight when the attack angle is smaller than 2-3 degrees in the research paper. As shown in the picture below, the CP point is at 17.5mm/4 = 4.375mm from the leading edge but the bolting is at 4.3mm, so, when the attack angle is very small, it has perpetual pitch suppression. The research measurement also shows that the airfoil has perpetual up-pitching torque at a cruise attack angle of 6 degrees because of the "center of pressure moving forward of the quarter chord". 

When the mechanical margin of error is added between the actuator servos and the actual blade position, the blade angle shifts as the following timeline.


This means that a large slop gap can result in an unstable craft. And in the above example depiction, the slop should be improved from 3.2 degrees to 3 degrees to escape the perpetual pitch suppression slump. And to avoid over-correction, the slop needs to be smaller than 2.1 degrees.

Balancing With Feathering Shaft Slop Larger Than 0.2 mm

Going from 2650 to 3150 and higher RPM requires fine-tuning the rotor with hand-tethered hovering. Here the R/D test retained the original decal of the blades. And the tuning took 3 tries in the research process, as pictured below. First, I fixed the tremoring by cutting out a corner of a decal. When aggressively trimming the corner, it was over-corrected, and tremoring reoccurred. The balance was restored by cutting the corner of the other decal. Once the amount of taping was determined, all decals were removed, and the clear tape was put in place for the required balancing. The balancing progress during the research is the 4 pictured below from left to right. The conclusion is that one square centimeter of tape makes all the difference because the rotor is stretched by centrifugal force like a musical instrument wire, and the 3150 RPM is on one of the resonance frequencies of the device. The thickness of tape 0.002-0.003inch = 0.005-0.0075cm, weight (assuming density 1g/cm-square) 0.005-0.0075 grams. This means RPM3150 needs a precision balance of 1/100th of a gram.

   

However, during multiple test builds, it was discovered that most builds could not achieve smooth balance and that blade swapping was needed. One of the successful blade pairings was pictured above on the right with a green checkmark. The 2 distinct symmetries, rotation and mirror, for balancing the rotors is diagramed here.

 The swapping needs to restore the rotational symmetrically of curved blades because our rotor hub does not have a cord-wise balancing bolting like the Bell 222 rotor, as highlighted in the picture on the right. The 2 blades with up-down warpings can be none-mirroring as the right side in the above diagram when subjected to 3250+ RPM's centrifugal force. The solution is to pick and match a pair that dynamically match the warping to each other.

A new blade with natural backward curving when spun up (not the same curving at rest) can be matched to a old blade with crash-induced backward bending, as shown in the above example with a green checkmark; the older blade's color fades, but it is the best match picked out from 3 different sets of new purchases. The at-rest warping mismatch shall be disregarded. At rest, one may warp up, and the other down, but the forces may balance out when spun up to 3250+ RPM, depending on the material's internal stress. All the other blades from the 3 sets fail to match the lower blade in the picture. The only way to check the pairing is to spin them up to full speed. And each pairing test needs to be checked with 2 alternative orientations of the grip installation. In the pictured example, only one orientation can produce a smooth spin. The other orientation always has vibrations that can't be tuned out with scotch tape.

Before the pairing process of a purchase, mark each blade with a unique serial number you manage, then weigh each blade individually and note the heaviest blade. The following pictures show an example of the heaviest blade, blade 3, of 7.301 grams. Then use scotch tapes spread evenly on each blade (except the heaviest one) to patch all the blades in the purchase to the heaviest weight. This ensures that the pairing process focuses on matching the the warpings of the blade material.

 

 

So, what happens if the rotor is a non-symmetrical mismatch? RPM detection with Engine RPM Android App can not lock and detect the RPM.

Use the Android app Engine RPM to measure the rotor's RPM with the settings in the screenshot below.  The app automatically logs the detected RPM every 3 seconds, as seen in the screenshot below. There is a 1.5% discrepancy between the PWM control signal and the actual measured value. The PWM controls are pictured with the respective actual RPM logs below. We use the actual measured RPM as standard.

The ultimate smooth balancing has a lateral (on the side) ballast, in addition to the axial balancing, as follows with 24 AWG copper wires.

 

The first loop has the crossing beneath the DFC bolting and excess wire trimmed. Then, pinch and turn the wire for a few turns. In the example on the right, the 7 loops on one side are the correct balancing because 14 loops were tried on one side, and zero loops on either side were also tested to be lesser balance. This example ballast weighed 0.2 grams with 7 loops.  However, this level of ultra balance is not required for smooth HD video shooting.