COMPACT PERSONAL AIRCRAFT

The Quaternion Group, a Miami, FL based startup, is involved in the research, design, development and commercialization of a novel Hybrid-IC eVTOL Compact Personal Aircraft "CPA" air-taxi embodiment, based upon US patent: ENHANCED NET PITCHING MOMENT MULTI- WING VTOL COMPACT PERSONAL AIRCRAFT

The CPA envisioned, has a reduced cost of manufacture due it's low mechanical complexity and features high energy efficiency under a typical low altitude, 60 mile urban operational radius of operation.

Achieving a relatively low 100 mph optimum air velocity and superior high lift horizontal flight capable energy efficiency with exceptional maneuverability for a five passenger compact personal aircraft in a congested low altitude UAM commuter airspace, are demanding requirements of an affordable, low maintenance CPA air-taxi embodiment.

As high energy efficiency in transportation is universally recognized as a store of value, the all carbon fiber composite construction, Hybrid-IC eVTOL CPA embodiment will achieve the highest attainable energy efficiency attainable of a mitigated landing area, UAM commuter air-taxi.

Low wing loading, large wing planform, mono-wing eVTOL aircraft can have stall speeds in the range of 55 to 80 mph, below which their rotors must provide predominantly vertical thrust.

The Compact Personal Aircraft can achieve an extremely low, 35 mph stall speed, before becoming 100% reliant upon its rotors for vertical thrust, providing unprecedented maneuverability and the highest energy efficiency of competing urban eVTOL aircraft.

In terms of investability and collateralizability, the novel and patented multi-wing embodiment of the Compact Personal Aircraft exists within a class of its own, providing unequivocal product differentiation with matching technical and fit-for-purpose performance.

The Quaternion Group, Compact Personal Hybrid-IC eVTOL Aircraft has been featured by The Vertical Flight Society at https://evtol.news/quaternion-group-compact-personal-aircraft

An initial slide deck is available at https://drive.google.com/file/d/1-yZKVocZy9q68wj0QsTCHKYOSPqHNXOe/view

The CEO of the Quaternion Group, Brendan Graham is an accomplished Electronics Engineer with over 30 years of developed proficiency in diverse areas of mathematics, complex analysis, digital electronic circuit design, analog and switched mode power conversion, custom avionics propulsion control, data telemetry, closed-loop feedback control and gradient descent platform stability, GNC, IMU and embedded hardware and software architecture.

Contact

Brendan Graham (CTO)

info@QuaternionG.com

305-793-3778

In order to facilitate my ultimate intent, that is to build a full sized 6 m x 6 m Compact Personal Aircraft with the ability to transport five human occupants, the decision has been made to construct iterations of RC scale models for sale and to raise both self sustaining funding and visibility for driving high net worth investment.

Here I begin the journey into constructing a 4' x 4' (1.2 m2), all carbon fiber, 1/5 scale model prototype of the Compact Personal Aircraft. Two major components are needed (a) an AHRS IMU electronic attitude and stability control system (b) CAD of the Compact Personal Aircraft, and (c) a scale model aircraft built of carbon fiber composite.

The good news is that I have already completed the design and coding of a high performance IMU based on the ESP32 s well as the CAD design in Blender, of the Compact Personal Aircraft featured on both this website's landing page and in the accompanying video animation.

Construct of the wings and struts of Compact Personal Aircraft in carbon fiber composite material will however require the construction of precision molds. A CNC machine is required to create the molds. To this end, the current task involves the construction of a high rigidity custom CNC machine.

A custom electronic attitude control systems, otherwise known as an IMU was developed over eighteen months beginning in January 2023 to June 2024, refactoring C code from my previously designed IMU targeting a TI OMAP AM3358 on BeagleBone running a Linux Xenomai real time kernel, to an intermediary STM32F746ZG based SBC running the Mbed OS, then finally to the ESP32-PICO-V3-02 running FreeRTOS. This rather time consuming embedded design project was necessary to enable the desired extreme high IMU performance and miniature physical size requirement and wherein a 1kHz (1 ms) real time gyro-accelerometer sample rate was achieved.

I had this adapter board fabricated to facilitate integration and interfacing of an inexpensive MPU9255 gyro/accelerometer board to the ESP32 over the SPI interface.

20240820_190117.mp4

Dual core ESP32 is a serious number cruncher. Yes it's io limited and intended to target WiFi and SPI and AD/DA applications where parallel io requirements are minimal. FreeRTOS is however not at all free. The learning curve for proper SMP implementation is very steep.

The resultant architecture incorporated a proprietary hardware timer interrupt driven synchronous thread dispatch layer on top of the FreeRTOS kernel enabling tailored threads interaction. This took months to finalize the architecture. FreeRTOS is not free.

Interestingly, the time to develop a well architected thread dispatch layer was worth the effort. With a 240MHz clock, the application achieved synchronous 1ms real time quaternion closed loop integrator processing of 6-DOF SPI sensor data and 3 PID controllers over bidirectional WiFi communication channel with the remote base station.

As has previously been stated, an attempt at running similar code on a 180MHz STM32F746 running Mbed OS was made, but the best that could be achieved was a 3ms thread periodicity. In the initial iteration of this embedded IMU project dating back to the January 2016, a 1GHz TI OMAP AM3358 running a Linux Xenomai RTC with a 200MHz PRU (auxiliary processor) assigned to sensor SPI communications also achieved the requirements, but without native WiFi. An externally attached USB WiFi dongle was used along with a bash script to maintain connectivity. Quite frankly, Linux is overkill plus one has to maintain kernel module interrupt C code, PRU C code, bash and uboot scripts plus a 200 page project manual. That's to much maintenance!

This is the initial iteration of the custom CNC machine build. The result will be a high rigidity machine enabling a similarly high degree of repeatable precision milling and turning. Several additions are in the process of being made including extending the X-axis gantry beam from 80 mm x 80 mm to 80 mm x 160 mm to achieve torsional rigidity requirements and additional linear rails on both the X and Y axes.

Unfortunately the "Made in the USA" days are long gone. Obtaining precision CNC components from China is incurring both increased costs and shipping delays and lead times.

As previously mentioned, the x-axis gantry must be extended vertically from 80mm x 80mm to 80mm x 160mm T-slot extrusion profile to facilitate the calculated torsional rigidity requirement, with the added benefit permitting an additional parallel horizontal x-axis linear rail coupling to z-axis actuator. I have currently used Rattmmotor ZBX80 linear actuators on all axes, but since the ballscrew housing brackets are a proprietary (yuk) design, I am compelled to ignore what would have been the easy solution in favor of an x-axis to z-axis MGN12H to MGN12H carriage perpendicular coupling.