Issue 39 Unmanned Systems Technology August/September 2021 Maritime Robotics Mariner l Simulation tools focus l MRS MR-10 and MR-20 l UAVs insight l HFE International GenPod l Exotec Skypod l Autopilots focus l Aquaai Mazu

82 Focus | Autopilots microcontroller’s silicon provider defines all the driver registries – for its Cortex products. CMSIS thus makes upgrading both software and hardware much easier. Beneath or otherwise aside from the low-level peripheral driver layer is typically a series of support modules for other key functions beyond the autonomous operation of the vehicle. For example, individual GUIs for GCSs, engineering and tuning code, calibrating the autopilot, as well as flight simulators or other virtual test environments can go here. Between these layers, it has become common to design interfaces that allow functional modules to be swapped in and out seamlessly. As a result, various new capabilities are now being seen across the unmanned space. These include intelligent algorithms for advanced manoeuvring such as autorotation, sea-skimming, and different forms of VTOL-transitioning, to accommodate the different types of VTOL-capable aircraft configurations. Also, as unmanned systems move into operations in urban and other populated environments for package delivery and so on, improved diagnostics capabilities are becoming key. Intelligent real-time analytics for confirming the integrity of sensor data and behaviour, processor functions and GNSS information are vital for preventing accidents. It is important to note however that traditional geo-referenced localisation – using measurements of latitude and longitude in degrees, minutes and seconds – was developed for maritime navigation, not aviation. It therefore has no vertical point of reference, and essentially all ‘controlled flight into terrain’ incidents occur because of autopilot errors in vertical localisation. While altimetry technologies are improving, an alternative approach gaining popularity is to create and embed a digital environment of a UAV’s mission airspace, including all the dimensions and dynamics, and parameters such as speed, time, acceleration and deceleration. The aircraft can then produce a point cloud in real time using either vision or Lidar to align itself with the mission parameters, dynamics and time requirements for absolute accuracy, and with no potential for collisions with structures, mountains or the ground. This approach is based closely on techniques used in digital movie special effects and computer graphics for positioning characters or objects precisely within an environment and timeline. Beyond accidents, the potential for hostile actors to interfere with autonomous vehicles has become well-known, particularly via the use of GNSS spoofing or jamming to halt or misdirect a UAV without its operator knowing. Algorithms aimed at detection of spoofing and jamming are therefore becoming either more prominent components or future development targets for autopilot systems. An alternative approach to preventing GNSS spoofing- or jamming-related problems has been the development of new localisation techniques that do not rely on GNSS. For example, both visual- and Lidar-based navigation has become increasingly popular for unmanned systems operating indoors or in tunnels, where GNSS signals cannot be received. Visual odometry techniques for flying at higher altitudes are also under development, which act similarly to close- range optical flow sensors by creating real-time points of reference to measure changes in a UAV’s position and orientation. While using such techniques to replace GNSS entirely may be a long way off, tests so far indicate that they can vastly reduce the rate of IMU drift, making this a potentially mission-critical technology for environments where the probability of extended GNSS jamming or outages is high. Open source Much of modern autopilot software has its roots in the widespread use and sharing of open-source architectures. Compared with other, less software-intensive forms of technology, open source has always had the advantage of being supported by a global community of individual programmers who can troubleshoot problems, contribute fixes, iterate algorithms for new features and provide other August/September 2021 | Unmanned Systems Technology Some newer autopilots come with control logic for advanced manoeuvres such as autorotation and sea-skimming (Courtesy of UAV Navigation)