Unmanned Systems Technology 033 l SubSeaSail Gen6 USSV l Servo actuators focus l UAVs insight l Farnborough 2020 update l Transforma XDBOT l Strange Development REVolution l Radio telemetry focus

36 A ctuation encompasses the rotary or linear movement of control surfaces, widening and shutting throttle valves, opening and closing payload doors, deployment of landing gear, and a host of other functions on unmanned (and manned) vehicles. Advances in this sector are critical. The UAV industry alone purchases hundreds of thousands of servos a year, and in- field replacements of them are one of the most time-consuming and labour- intensive maintenance tasks, requiring extensive testing to confirm that each one has been installed correctly. While the term ‘actuator’ can encompass hydraulic and pneumatic systems, in the unmanned systems industry the overwhelming majority of (if not all) actuators are electromechanical, and are sometimes called ‘servomotors’ or simply ‘servos’. Servomotor technology has evolved considerably over the past several years. Materials, interfacing and data protocols, safety features and more are being optimised for different applications, leading to as diverse a range of actuator designs as unmanned vehicle configurations. Key actuator components A handful of common components inside servo housings enable the chain of events that output actuations in all unmanned vehicles. First, the circuits on the servo’s PCB assembly receive control signals and power from the vehicle’s autopilot. They are transmitted to an electric motor to allow it to produce the exact degree of rotation required. The motor produces a differing effect depending on whether the servo is rotary or linear. In the former, the rotor turns a geartrain, typically reducing the rotational speed to produce a higher torque at the output shaft. That end-point might have a servo arm and a pushrod for toggling a control surface, or a butterfly valve for opening and closing an engine’s throttle. For an electromechanical linear servo to extend or retract its output shaft, typically some form of screw train is used. Most often, a leadscrew is machine-cut with a helical thread, and a ball nut is mounted on the end Advances in servo actuator technology continues apace, writes Rory Jackson , who explains some of the latest developments Moving with the times New aerospace-grade servos are packing more features into smaller packages, with some now weighing as little as 30 g while still using aluminium housings and steel gears (Courtesy of Volz) August/September 2020 | Unmanned Systems Technology