iFlight AOS 5 O3 5" FPV Drone Frame Kit

Vibrations limit performance

As a pilot I often struggled with Jello, mid-throttle oscillations and propwash handling on my 5 inch freestyle mini quads. As an aerothermal engineer I realized that the issue lay in the vibration and resonance performance of the quadcopter frame itself.

Even the cleanest motors and props produce large amounts of vibration in flight. These vibrations excite the resonant modes of the frame amplifying vibrations at certain frequencies, increasing their amplitude and energy. These vibrations pass into the gyro and create noise on the signal. This noise requires additional filtering, which adds latency, and limits maximum PID gains through motor heating.

Modern flight firmware: Betaflight 4.3, KISS Ultra, and FETTEC all benefit enormously from a low vibration airframe. The AOS 5 O3 allows you to run less filtering, with less associated delay, and increase your PID gains far higher than any other frame in it's weight class. Get ready for the most responsive 5" quad you have ever flown.

Harmonic analysis, topology optimization.

I used Blackbox logging and harmonic analysis to visualize the vibrations of the AOS 5 O3 during the design process. For the O3 I combined this with topology optimization to tune the geometry of each part of the frame, moving the frame resonances up and away from the motor frequencies and separating them as far as possible. This avoids, as far as possible, the situation where the motor frequencies match a frame resonant frequency and so amplification is minimized.

As a result, you can run less filtering. Every layer of filtering adds delay that’s mathematically related to how effectively it removes vibrations. This delay prevents the flight controller from responding rapidly enough to propwash leading to poor propwash handling. Reducing the amount of filtering is the best way to improve propwash handling. With the AOS 5 O3 you’ll be in the best possible position to reduce your filtering to an absolute minimum.

Another advantage of lower noise is the ability to run higher PID gains. Higher PID gains allow the quad to track your stick movements with less delay and more precision. The result is greater confidence, particularly when flying tight lines where fast reactions are vital.

Top and bottom plates

The 2.5mm thick main plate supports up to three full-sized 30.5mm stacks. 20 and 25.5mm stacks are supported and the M2 20mm holes are designed to be easily drilled out to M3 if required.

The top plate has pressnuts installed for effortless GoPro mounting using the AOS standard 32x32mm footprint.

The cut outs in the top and bottom plate of the AOS 5 O3 are optimized to preserve as much of the bending and torsional stiffness of the plate as possible whilst minimizing weight.

ARMS

The AOS 5 O3 uses a topology optimized truss design for the arms. This truss design provides enormous torsional stiffness, resolving a key source of vibration in traditional frames. It also allows two particularly harmful resonant modes to be individually modified to separate them in frequency.

Truss structures are inherently very strong as they convert bending loads into compression and tension in the individual members. Carbon is much stronger in pure tension and compression than in bending. The 3 screw motor mounting reduces weight and removes the motor hole that can be a stress riser for compressive failure in hard crashes. 

Y-shaped motor protectors minimize the risk of damage to those expensive components. Should you ever need to replace an arm, there are only two screws to undo and neither are shared with your electronics.

Camera Protection

The AOS 5 O3 uses 2.5mm Carbon Plates to hold and protect the camera. These are stiffer, lighter and cheaper to replace than aluminum or titanium.

The camera plates include 2 standoffs to maximize durability and a cutout pattern that supports DJI O3 and all typical19-20mm FPV cameras.

GoPro Mount

The AOS 5 O3 has 32x32 mm M3 mounting holes for 3D printed mounts for your HD camera. Press-nuts in the top plate make installing the mount a breeze.

You can download an STL for the mount shown HERE.