Unmanned Systems Technology 028 | ecoSUB Robotics AUVs I ECUs focus I Space vehicles insight I AMZ Driverless gotthard I InterDrone 2019 report I ATI WAM 167-BB I Video systems focus I Aerdron HL4 Herculift

42 heat, it could be determined fairly quickly whether adequate cooling will be available for the vehicle and its operating environment. True ‘health monitoring systems’ for predictive maintenance analytics have yet to be implemented in any UAV ECUs. However, the spread of data recording systems means ECU manufacturers can begin amassing the vast quantities of engine logs needed for accurately modelling which combinations of measurements and anomalies would need preventative measures. Depending on the willingness of end-users to share their data, ECUs might start coming with true predictive maintenance algorithms within the next five years. Testing and screening Once an ECU is manufactured, its PCB should be closely checked for any soldering defects, either visually or (preferably) by functionally testing every part of the circuit board. The conformal coating should also be examined, under UV light. UV blue tracer additive is used in the coating, and any section of the ECU not fluorescing under the light shows that the coating was not applied properly. Such areas will be vulnerable to environmental damage and must be addressed. Assembled ECUs should undergo environmental stress screen tests, in which they are subjected to repeated temperature and vibrational cycles to weed out early-life failures before they enter service. These failures can be reviewed, so that over time, patterns can be identified in the types of defects happening, to unearth flaws in either the design or manufacturing process. During stress screening, ECUs will often be powered up and operating with dynamically representative sensors, actuators and loads while undergoing extremes or near-worst cases of heat, cold or turbulence. That allows abnormal operating conditions to be tested more easily so that fault detection and accommodation systems can be updated to compensate if necessary. Some ECU manufacturers are going as far as putting new ECU models through highly accelerated life testing (HALT). This places units in a test chamber and subjects them not only to great extremes of temperature and vibration but also wide swings in those variables. While there are no standards requiring October/November 2019 | Unmanned Systems Technology Focus | Engine control units keep maintenance records, potentially reducing operating costs and improving operation safety. For more accurate analytics as to when maintenance is needed and what kind should be performed, a wide range of ECU inputs can be logged after measurements are received. That can mean not just the number of engine hours but the total number of revolutions, the hottest cylinder head temperature recorded in flight, the lengths of time spent at excessively high temperatures, time spent at high load and even the number of engine starts. That information can then be fed into an onboard maintenance scheduling system, and update it so that it ‘knows’ when to send alerts to the user, in a similar way to how a ‘check engine’ light works on a road vehicle. The ECU could then take the pertinent data and output it as a detailed record for the UAV’s technicians or even for the engine manufacturer (if the unit is sent back to them). Designing and installing more detailed logging systems such as these onto ECUs would also make it easier to integrate engines onto vehicle chassis. As an example, by looking broadly at how long the engine spends at high With SD card technology continually getting smaller and lighter, some ECUs now come with data loggers for recording an engine’s running history and aiding in maintenance tracking (Courtesy of Northwest UAV) Aggregating engine data via the ECU from flight hours or test cycling accelerates the development of predictive models that help prescribe maintenance for engines and ancillary components (Courtesy of Performance Electronics)