Uncrewed Systems Technology 046

16 Netherlands-based Fusion Engineering has developed a flight controller designed to allow better fine path-holding and station-keeping for next-generation multi-rotor applications, by using a proprietary control methodology (writes Rory Jackson). “The Fusion Reflex flight controller contains our own hardware platform, which is the carrier for our operating system and control algorithms,” explained Robert Crone, CEO of Fusion Engineering. “The algorithms are what sets our performance apart from other flight controllers. They are based on INDI, or Incremental Nonlinear Dynamic Inversion, and are optimised for aircraft.” The core goal of using INDI was to achieve the fastest control response that a multi-rotor can handle, correcting very quickly for disturbances such as wind gusts without resulting in instabilities. To get the same performance from a conventional PID-based controller would mean increasing its gain to levels that can result in unstable behaviours. INDI algorithms are oriented around precisely calculating and implementing the dynamics required of the vehicle. INDI itself is a relatively simplified and flexible approach that uses a UAV’s accelerometers’ feedback to compute the dynamic behaviour of the system and output suitable responses to external disturbances. By measuring the difference in a UAV’s actual acceleration relative to the desired acceleration, and doing so in extremely small increments over very short periods of time, the onboard motor’s speeds will continuously and rapidly change to ensure that the next increment in acceleration is always one step closer to the acceleration the operator wants. “We have a video showing one of our test UAVs in a wind tunnel test where it undergoes 72 kph gusts while sustaining minimal deflections and very quick, short recovery times without overshooting,” Crone adds. The Fusion Reflex itself weighs 100 g and operates using two 5 V power inputs, for redundancy. It also includes two independent I2C ports, two UART interfaces, a CAN bus with two connectors, two USB ports, an SPI port and 16 dedicated ESC I/Os. A 2.4 GHz wi-fi modem is also installed. It comes with integrated triple- redundant inertial systems as well as its own internal real-time clock. A 1.2 GHz 64-bit ARM Cortex A53 processor with four cores is used as the central computer, with 1 Gbyte of RAM, and featuring 32 Gbytes of flash storage and a separate 100 MHz ARM Cortex-M4 processor for computing I/O signals and ESC rpm control. Airborne vehicles Rapid UAV controller October/November 2022 | Uncrewed Systems Technology The Fusion Reflex flight controller uses Incremental Nonlinear Dynamic Inversion to achieve the fastest control response a multi-rotor can handle