Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

7 Platform one Unmanned Systems Technology | April/May 2021 Windhover has developed customised hardware for its high-reliability flight software for UAVs and space systems (writes Nick Flaherty). The hardware runs Windhover’s fault-tolerant Airliner software that was developed using a software framework from NASA, and uses the latest Xilinx Ultrascale FPGA system on chip (SoC). The SoC has two ARM Cortex-R5 cores for safety-critical operations and four ARM Cortex-A53 processors along with programmable logic. “It’s a flight computer that matches the capability and reliability of the software,” said Mathew Benson, Windhover’s CEO and chief engineer. “We partitioned the board into one processor reserved for the critical functions and another for functions that need the performance,” he said. “We have a lot of layers of redundancy with the sensors, down to the CPU itself. It’s all designed for high-altitude operation, and we will use it for UAVs and small satellites.” Each R5 core runs the same software using a real-time operating system (RTOS) certified to run the safety-critical operations. The two cores run in a mode called ‘lock step’, where the operation of each core is checked by the other. The quad A53 cores can run a standard Linux operating system for high-performance applications such as sensor fusion algorithm, imaging or machine learning. The programmable FPGA fabric can also be used to implement custom logic. Windhover has also added an extra processor core in the fabric to process sensor data before sensor fusion on the A53 cores. Different sensor interface modules can be added to the board for flexibility. “The synchronisation of the boards is proprietary – they aren’t ever wrong, they are either right or they go quiet,” Benson said. “That means the boards don’t have to vote to provide the correct answer, as that makes the software complicated and fragile.” Flight systems Hardware-software match The prototype board is partitioned for critical functions and performance Researchers at CEA-Leti in France have developed a high-performance gyroscope that can improve the inertial navigation of UAVs and driverless cars (writes Nick Flaherty). Working with researchers at the Politecnico di Milano, the team used a technique called NEMS (nano- electromechanical systems) to build a gyroscope that can operate accurately in harsh environments with a lot of vibrations. NEMS uses piezoelectric elements that measure between 10 and 25 nm. These vibrate when an electric field is applied, and movement varies the vibration, providing the gyroscope function. The NEMS design replaces the capacitive element in a MEMS (micro-mechanical) gyroscope. The design shows it is possible to detect minute rotational movement even among system vibrations. Low-cost MEMS gyroscopes tend to drift as a result of the vibrations in the platform, especially in a UAV in the air or a vehicle on the road. The NEMS accelerometer operates at a resonant frequency of 50 kHz, well above the typical frequencies of up to 20 kHz in physical systems, and so shows a stability of 0.5 º /hour. This can be used for more accurate inertial navigation when there is no satellite signal for GNSS systems. As the NEMS device measures 1.45 mm 2 it can be integrated with a three-axis accelerometer and/or a high- performance pressure sensor on a single, low-cost chip with less drift and higher accuracy. Gyro exploits nanotech Navigation Using piezoelectric materials for the gyro provides greater accuracy for inertial navigation systems