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97 suppliers have announced plans to build new chip foundries, although none are yet at production readiness. As a result, manufacturers are redesigning and updating their ECUs in new ways in order to continue supplying systems without being held back by the supply disruptions or extreme lead times – up to 2 years in some cases – that are becoming common for microprocessors and other parts. Looking deeper, additional changes and improvements are emerging as ECU engineers consider future methods of propulsion. UAVs and large air taxi- type vehicles need robust control of powertrains that are hybridised, running on alternative energies such as hydrogen, biodiesel or heavy fuels, or feature other differences that must be accounted for in the engine management system. It is important therefore that manufacturers of UAVs, urban air mobility vehicles and other autonomous systems pay close attention to the new capabilities and benefits of modern ECUs, so as not to miss out on anything they and their vehicles ought to be exploiting for safe and stable operations. Design A typical ECU design is centred on a processor tasked with several functions. Almost universally, these encompass the actuation of fuel injectors, spark plugs, throttle servos and the control of other ancillary systems. Through these outputs, the ECU can carry out commands from the autopilot, such as ramping shaft horsepower up or down or engaging a generator for more electrical power. The precision with which these are controlled is key to the timing, health and efficiency of engines, and is achieved through a comprehensive body of data inputs fed into the ECU from across the engine. Sensors for mass airflow, crank speed, crank position, cylinder head temperature (CHT), oil pressure and many others provide this data in real time, and this is then checked against embedded maps detailing how to adjust control outputs accordingly. This data can also be logged on board the ECU for future analyses, and communicated to the autopilot (and by extension to the operators at the GCS) for monitoring engine safety, diagnostics and performance, with that link also enabling real-time updates to ECU software if required. With the processor mounted on a circuit board, connectors are laid out for these inputs to feed into the processor and for it to send control signals and key data feeds. A power supply must also be present – anything much more than 10-20 V is rarely necessary – as well as perhaps data-logging drives and other non-critical electronics. This general architecture is well- established, but the market for subsystems in autonomous and uncrewed vehicles is known for requiring meticulous customisations, in order to right-size an aircraft or other system for an exact mission, endurance, payload and environment. As a result, the first step in designing a new ECU is often an extensive requirements definition process. That starts with high-level questions about the power plant itself, such as whether the engine is a two-stroke, four-stroke or Wankel, whether it runs on gasoline or heavy fuel, whether it is spark-ignited or compression-ignited, and various other details about the engine. Customers and engineers can also come to an agreement on the type of engine management strategy, largely by referring to how the ECU calculates injector opening times and ignition timing. These will have an impact on the types and integration of engine ECUs | Focus The precision with which autopilot commands are carried out is achieved through a comprehensive body of data inputs fed into the ECU Unmanned Systems Technology | April/May 2022 Defining high- and low-level requirements is key to plotting the design layout of a new ECU (Courtesy of Moscat Ingenieria)