Drones - test

FPV racer hardware review : Flycolor 4 in 1 F3 board

hugues — Tue, 02 Aug 2016 13:00:49 +0000

This is a hardware review of an interesting product for FPV racers.

This product consists in an integration of mutliple components you would otherwise need to solder and assemble together with lots of wiring, thus saving weight and making a cleaner build.

In brief, it is at the same time:

-a F3 flight controller board (could have been the latest F4 generation but hey, F3 is good enough for my flying skills). The F3 board plugs/unplugs from the ESCs/PDB motherboard. So it can be replaced if needed.

-a power distribution board

-a 5V BEC

-a 12V BEC

-4 in 1 20 amps BLHeli ESCs. Their signal+ground wires are connected to the F3 board within the PCB , so no wires required. All four ESCs can also be individually replaced if needed.

The video shows all positive and negative aspects I found about it. A big plus is the weight saving and ease of build. The biggest negative point is you are stuck with a rectangular form factor and the solder pads for the motor wires are not best placed for a typical FPV X frame.

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FPV racer

review

test

flycolor

Review & history of flight controllers for FPV racing (MultiiWii branch)

hugues — Tue, 02 Aug 2016 12:56:52 +0000

The whole flight controller firmware landscape has changed dramatically in the last couple of years since the introduction of the Naze board for FPV racers running baseflight firmware.

As opposed to software (r)evolutions, flight controllers hardware did not evolve as much (apart from processing power increase, nothing revolutionnary). One noticeable novelty on hardware level is the relatively new open source "SP racing F3" board. Made a quick tech review of this board in the video which, as I understand it, became the state of the art flight controller for "seriously pro" FPV racers.

This video also shares some brief historical & evolution about hardware/firmware for FPV racing (MultiiWii evolution branch).

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Anti Jello mount for Mobius brushless gimbal

hugues — Tue, 02 Aug 2016 12:19:26 +0000

To suppress vibrations & jello in videos taken by very lighweight camera brushless gimbals is a challenge as none of the classical methods are working well. The more weight, the easier it is to manage vibrations. When you combine extreme lightweight gimbal with a CMOS sensor technology, you'll get very prone to the so called "jello" effect.

In this video I share some findings about what works best with my 50 gr 2-axis Mobius gimbal.

The ship itself is my Subonekilo quadcopter project (800g actually with battery) which I blogged about previously. It runs Arducopter on Pixhawk, 9 " props, 3S battery.

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Review & test of Gearbest's Pixhawk and comparison with 3DR's Pixhawk

hugues — Tue, 02 Aug 2016 12:17:06 +0000

Recent 3DR's move not to sell DIY components & parts anymore, pushes hobbyists and prosumers to diversify their supplier's sources. Like many others in the community, my issue is to find an "as good quality as 3DR" alternative for a Pixhawk board. I started looking around for possible 3DR Pixhawk replacement candidates, with a quality I can trust in my builds.

There exist myriads of different "Pixhawk" equivalent boards. Most of them are not direct drop-in replacements as they are equipped with different connectors and have different sizes and shapes. Furthermore, most of them do not share the same quantity and redundancy of sensors (i..e.: two gyro, two accel, compass, baro, etc). A direct drop-in replacement is essential for prosumers and professionals trying to standardize parts, connections and components to a maximum.

Then, I was kindly requested by Gearbest to review some of their new FPV racer quad; offer which I declined being a very poor racer pilot (wouldn't have made justice to their fpv quad), proposing them instead to review their Pixhawk board which looked to be an exact match for 3DR Pixhawk board on all aspects: schematics, size, shape, connectors, etc.

This is what this video is about : a test, review and comparison of Gearbest's Pixhawk (versus 3DR's Pixhawk).

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Review and tests of camera anti-vibration systems

hugues — Fri, 31 Oct 2014 10:35:50 +0000

To optimize videophotography results, vibrations need to be reduced as much as possible. The objective is to disturb as little as possible a brushless gimbal holding a camera. (we all know too well how hard it is to get a brushless gimbal well tuned).

As most people, brushless gimbal tuning is done on the bench using accelerometers & gyros of the brushless gimbal's IMU. And like most, we do not get as good results when flying. Why?: frame & air vibrations. Frame vibrations are created by motors, props and wind. Direct air vibrations (external wind) also impact the brushless gimbal.

This is a blog post showing anti-vibrations objective measurements of different isolation systems, obtained on my Mr. Grey X8 workhorse shown on the introductory picture. All vibrations measurements are made during periods of min 30 sec of hover in stabilize mode. Take-off and landing periods are excluded of measurements.

Configuration of the test craft:

-Pixhawk controlled -Stabilize mode

-T-Motors MT3515-400Kv

-15x5 XOAR props

-6S batteries

-2 axis brushless gimbal - Alexmos

-Sony NEX5 camera

-Weight of the gimbal+camera+fpv+3S 1ah battery : about 1250 g

-AUW : about 6.8Kg

Vibrations measurement setup:

-All tests were made with the craft configured fully ready-to-film : except the gimbal which remained off not to measure its own generated vibrations. The camera was thus simply screwed on the gimbal with no power to the brushless motors.

-X-Cam vibration measurement tester

X-Cam is installed on the different areas of the craft to be tested. Its mesaurements are triggered remotely by a PWM pulse (on/off switch allocated on Taranis). It is powered directly through the PWM servo cable connected on the receiver.

Data are stored on board its flash memory. It is made for vibrations measurements in the 0-200Hz range and can store up to 3 min of continuous measurements.

Through the X-Cam GUI , data is downloaded from the flash memory to produce a time graph (basically useless as it shows the X-Y-Z vibrations measurements along the time axis), and a frequency graph showing X,Y,Z vibrations amplitudes (in number of g) versus frequency (in Hz). Raw data or weighted averaged data can be calculated.

Two anti-vibration systems were measured,

First a silicon ring system as shown below,

Four of these were used in a X configuration between Mr Grey's two plates (see introductory picture). Each plate is made of plywood; square shaped with 20 cm long sides.

Silicon rings come in two stiffnesses: red for softter silicon, black for stiffer silicon. Here, only the red softer ones were tested. Each Secraft system costs about 9 euros each (www.secraft.net) , which is relatively cheap.

Second tested system is a "Bell" shaped precompressed silicon system. Each "Bell" is made for a 250g payload. Each one of them costs about 39 euros (www.altigator.com) which is quite expensive. It is mostly used in high end professional aerial photography rigs :

Four of those were used, in each corner in between Mr Grey's test plates as shown below:

Reference measurement:

In order to compare results, a reference measurement is made on the frame itself, with the X-Cam placed at the center of Mr Grey's top plate, under its protective "flower pot".

Frequency domain picture shows two frequencies were vibrations are significant : 85Hz and 175Hz; The measurements show about 0,3g of vibrations on all three axis at 85Hz; and 0,4-0,5 g vibrations at 175Hz.

First test result with Silicon rings system:

X-Cam is now placed on the second bottom plywood plate on which the gimbal is fixed,

The results show that frame vibrations are continuing to pass through to the gimbal at the same frequencies (85Hz and 175 Hz) but amplitudes are divided by a factor of 10 at 85 Hz and almost by a factor of 20 at 175Hz, versus non damped frame vibrations.

Second test with the "Bell" system:

X-Cam is placed at the exact same location as for the first test,

The results show that frame vibrations are continuing to pass through to the gimbal at the same frequencies (85Hz and 175 Hz) but amplitudes are divided by a factor of 2 at 85 Hz and by a factor of about 2 at 175Hz, versus non damped frame vibrations.

If we show the silicon ring's system on a graph at the same scale as Bell's system:

The silicon ring anti-vibes system literally erases vibrations in comparison with the "Bell" anti-vibe system....

Comparison of both anti-vibrations systems:

It appears clearly that the "silicon ring system" is much more efficient at reducing vibrations versus the "Bell" system. Further, this silicon ring system is much cheaper than the Bell system.

For once, more expensive, supposedly professionnal parts were not up to the task versus cheaper diy parts.

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