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

Servos for driving the control surfaces of unmanned aircraft are a vital part of the system design (writes Nick Flaherty). They are specified according to the size and weight of the control surfaces, as well as the airflow the surface has to operate against. There are two types of load that must be accounted for when specifying them. First is the continuous torque load, which is the load that can be applied constantly without the risk of overloading the servo. Servo components such as the motor, gears and electronics can withstand that load for their entire service life. Then there is the peak torque, which can be handled by the servo for a period of a few seconds, after which it needs to cool down at lower loads. The system engineer should choose the servo according to its continuous torque rating. In the example of the DA 58-D from Volz Servos, the continuous torque is 80 Nm while the peak torque is 200 Nm. It is a dual-channel redundant servo, where both channels can also run in a degraded mode if there is a problem. In this mode the continuous torque is 40 Nm but the peak torque is 100 Nm, ensuring that the control surfaces can still be operated. After running in this mode, the servo would need to be replaced. The servo’s peak torque is still an operating specification and should not be confused with the stall torque. At stall torque the servo delivers the highest possible torque, but the output shaft is not moving any longer. Therefore, there is no real use-case for this operating point. Servos should be chosen according to their continuous torque rating – for the Volz DA 58-D servo, that is 80 Nm Volz talks servo torque Airborne vehicles PENGUIN C VTOL THE PERFECTION OF VTOL UNMANNED AERIAL SYSTEMS Get more information at www.uavfactory.com Over 14 hours of flight endurance Automated precise takeoff and landing Compatible with a full range of EPSILON EO/IR payloads 20% endurance increase with patented boom technology Range of 180 km