Issue 45 | Uncrewed Systems Technology Aug/Sept 2022 Tidewie USV Tupan | Performance monitoring | Bayonet 350 | UAVs insight | Xponential 2022 | ULPower UL350i and UL350iHPS | Elroy Air Chaparral | Gimbals | Clogworks Dark Matter

100 Focus | Gimbals are tested with new tyres. The gimbal can be spun under close observation – to obtain data such as current, vibration and motor position – so that engineers or automated test software can mark where counterweights (or other attempts at manual calibration) are needed to balance out the gimbal in all axes. Mechanical stabilisation Obtaining high-resolution imagery and video depends critically on keeping gimbals stable, particularly when pointing at far-off or moving targets. Mechanical stabilisation systems consist largely of BLDC motors and motor controllers. An increasing number of gimbal manufacturers are therefore choosing to specialise in the design of e-motor systems in-house, to control how they are optimised for parameters such as size, weight, latency, power efficiency and motion smoothness. For instance, field-oriented control (FOC) systems are highly beneficial, as they enable a sinusoidal, smooth-wave output of movement instructions from the motor controller to the motors in charge of each axis of rotation. Traditional control by trapezoidal commutation makes for a much more ‘jerky’, staccato output of rotation orders, meaning reduced precision and energy efficiency than gimbals using FOC. High-end gimbal companies are therefore developing their competencies in FOC, both in sensored and sensorless designs. The latter are less costly and more reliable, although the former might be better for many gimbals owing to the more precise control and low-speed torque they can achieve. Such companies are even exploiting new types of small electric motor technologies, including some of those we discussed recently (see issue 42, February/March 2022). These designs can feature highly useful qualities for gimbals – for instance, if a gimbal’s e-motors are designed with ironless stators, they will not exhibit ‘cogging’ torque ripple. As a result, each motor’s motion will be far smoother than those with iron stators, and its positioning will be more accurate, resulting in much clearer imagery from the gimbal when tracking and zooming in on moving targets. Ironless stators are also lighter, which provides major improvements in power- to-weight ratios, meaning they contribute to longer endurances between recharging or refuelling, with more data gathered and processed per mission. Digital stabilisation and video processing While mechanical stabilisation remains the first and most important step for clear and precise imagery, quality digital stabilisation is still a useful differentiator between high and lower end gimbal systems. Ongoing improvements in GPU and SoC technology are motivating high-end manufacturers to adopt more powerful engines for image enhancement. While silicon shortages still pose an issue for mass production or price reduction of such systems, the small-volume, high-price nature of the professional UAV market means there is still plenty of demand for gimbals running on the latest processors. As such, engineers are upgrading to newer products with up to eight times the performance of their predecessors. Some companies meanwhile continue to release new microcontrollers that gimbal manufacturers rely on for enhancing their data processing as well as control signals, which can feed into digital and mechanical stabilisation in critical ways. These are also key to providing a detailed application layer interface or companion computer through which end-users can adjust a gimbal’s mission parameters in a straightforward manner. Beyond digital stabilisation, other intelligent functions depend on the video processors of gimbal manufacturers, and today’s uncrewed systems customers expect advanced video processing functions such as target classification, continuous zoom, sensor data fusion and smart overlaying from their products. At a more fundamental level, the video processor is also responsible for the number and quality of video channels that can be encoded, which can directly limit the number of cameras per gimbal or the number of gimbals per vehicle. The key problem lies with the ability to fit increasingly large and powerful video processing units inside the tight space of the gimbal without it resulting in excessive power consumption or overheating on the part of the processor. Of course, these issues can be circumvented to a high degree by putting the video encoding and processing systems outside the gimbal, somewhere else on the vehicle (if the density August/September 2022 | Uncrewed Systems Technology Professional cinematographers subject their gimbals and cameras to incredibly rigorous forces and manoeuvres, pushing innovations such as new processor or battery integrations to their limits (Courtesy of Freefly Systems)