7 Platform one Uncrewed Systems Technology | October/November 2024 Test cell gives pre-flight data VISIONAIR has developed a test cell with the capability to evaluate all aspects of a complete UAV propulsion system, including internal combustion and electrical elements. Ben Tschida, CEO of VISIONAIR, points out that engine dynos are commonplace but, even where there is no electrical propulsion force to be accounted for, the use of one is of limited value. “The problem is that with a static engine test you can’t really simulate any loads as dynamic thrusts,” he notes. “Also with a propeller you create a specific torque at a specific rpm, but you can’t change that torque value without changing the propeller. You also have losses in a propellor, particular at the blade tips, so you can’t really tell the precision of the tests you perform. “Using conventional test systems you can have test data for the propellor, test data for the engine, data from the electrical power system, but it is impossible to test all of this as an integrated system. There are so many inefficiencies in a full system from the torque from the engine down to the servo, so it can be very complicated to provide an exact calculation. All of these uncertainties and inefficiencies led us to develop a test cell to serve the entire propulsion system. “Our company develops modular power management systems for all kinds of UAV platform. When power electronics need to be integrated that can be a challenge. We were already testing the electronics and my background is mechatronics, so we have developed a modular test cell for the entire powertrain system to get as precise values as possible.” Tschida emphasises that there is no ‘standard’ version of this testing equipment - it is configured to suit the application. An eddy current brake is used for engine loading, with three size options according to requirement. Optionally a high speed servo motor can put out 9kW to test generators and electronics standalone, if an engine is not available. Moreover the sealed cell uses blowers to simulate the airspeed that a UAV would be flying at to evaluate the cooling supplied to engine fins and/or engine and electrical system coolant radiators. This can determine whether a larger radiator is required or whether a smaller radiator can be used to save weight. “When you generate propulsion thrust you use power from the engine so how do you know how much power is left?” asks Tschida “You need mechanical and electrical loads so we have many DC loads to simulate loads during different parts of a mission, for example when using on board equipment. That helps to optimise the overall propulsion system or define the size of the batteries required. How much power is left after those prescheduled loads and the propulsion requirement defines how high you can fly, considering the altitude power losses of an engine. “We built the whole system around a modular measurement system for automated test setups or we can use manual inputs to increase the various loads. The test cell network is IP based. We have an IP camera to record tests and we can run a propulsion test remotely in cooperation with a customer.” The test cell is based on a ISO shipping container and includes a wide range of test systems. Optional acoustic cameras provide visual data on components that might provide acoustic warning of strain while Infrared sensors measure how hot a specific zone of the powertrain gets. The rig is water cooled to allow for prolonged continuous running, for example 150 hour testing. See the simulation and test focus on page 38 of this issue. Data UAV powertrain test cell (Image courtesy of VISIONAIR)
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