7 Platform one Uncrewed Systems Technology | October/November 2024 Test cell gives pre-flight data VisionAir has developed a test cell for UAV engines that can provide accurate data on performance before a test flight, writes Nick Flaherty. “The problem is that with a static engine test you can’t really simulate any loads as dynamic thrusts,” said Ben Tschida, CEO of VisionAir. “With the propeller, you create a specific torque at a specific rpm, and you can’t change the torque. You also have losses in a propeller, particular at the tips, so you can’t really tell the precision of the tests you perform.” He explained: “So you have test data for the propeller, test data for the engines, data from the power system, but it’s impossible to test all of this on the ground in a static test. We always take a look at the full system, and there are so many inefficiencies in a full system, from the torque from the engine down to the servo, and it can be very complicated to provide the exact calculation.” “All of these uncertainties and inefficiencies led us to develop an engine test cell. We develop custom power management for all kinds of platforms, and when we provided the power electronics our customers faced challenges with the integration. “We were already testing the electronics and my background is mechatronics, so we built an engine tester that is as modular as possible to get as precise values as you can. We can also integrate a high-speed servo motor that can put out 9 kW to test the engine as a generator,” he said. The test cell uses magnetic eddycurrent generators to pro vide the simulated load on the engine or generator, and these can be air-cooled with a blower or water-cooled for higher power requirements. “We built the whole solution around a modular measurement system for automated tests, or use sliders to increase the power and voltage. The test cell is IP-based; we have an IP camera to monitor it, and run the engine or propulsion-test remotely,” he added. The test cell is mounted in a shipping container and includes a wide range of test systems. Acoustic cameras provide data on components that are creaking – for example, in the exhaust in the muffler – and infrared sensors to see how hot the gearbox or the generator gets. The test cell is modular, so with a 1275 cc engine it can be used with eddycurrent breakers for 10 kW, 20 kW or 40 kW loads. Sequencing of the electronics is used to avoid the engine stalling when pulling too much power. “We simulate the air speed that it is flying to define the air speed to cool the engine. This can determine whether a larger radiator is required for cooling or a smaller radiator can be used to save weight,” he said. “When you generate power, you take power from the engine, so how do you know how much power is left? You need a mechanical load and electrical loads, so we have a DC load to simulate loads during different parts, [such as] the operation, so, for example, a camera and the payload, and that helps to define the size of the batteries required. How much power is left after those loads and propulsion defines how high you can fly.” See the simulation and test focus on page 38 of this issue for more simulation discussion. Data Engine test cell (Image courtesy of VisionAir)
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