AVIATION TESTING


Power Profile Test in the U


Atmos VTOL autonomous drone makes use of sophisticated test processes to ensure the right balance of power in its motors.


nmanned Aerial Vehicle specialist, Atmos UAV, was recently faced with a development challenge for its “Marlyn” autonomous Vertical Take-Off and Landing (VTOL) aircraft. The UAV


can perform VTOL manoeuvres as well as normal forward flight fully autonomously. Due to its complex propulsion system, the challenge


Marlyn presented to Atmos development engineers was to select a combination of motor system and propeller which could provide the required thrust in-flight and during take-off and landing, while maintaining a flat and safe power dissipation profile across all the varying load conditions. With so many parameters and variables to consider


and having tried a number of alternatives, Atmos chose the Yokogawa WT1800E Power Analyser to optimise range, efficiency and safety on the craft. By using this test instrument, Atmos was able to significantly reduce the time required to test combinations of off-the-shelf motors and propellers, and enabled them to quickly find the optimal configurations with a high degree of certainty.


CONSISTENT POWER The duties of Marlyn are such that consistent power delivery in all modes of operation are essential. Just like a fixed wing drone, Marlyn is capable of high- speed flight, which typically enables it to survey an area of 12 square kilometers in a single flight, while the VTOL capability allows it to be launched from almost anywhere. This kind of complex flying performance means that surveyors can dramatically reduce the required flying time and thus achieve higher productivity and lower operating costs. Benefiting from the ability to operate safely and reliably in wind speeds up to 45 km/h, Marlyn is being used throughout the world to survey, map, and gather geospatial data in such demanding industries as mining, agriculture, forestry and construction as well as defence agencies. Performance is therefore a key requirement and Atmos needed to test the motor power dissipation rigorously.


HIGH PERFORMANCE POWER ANALYSIS Before taking the WT1800E from Yokogawa, Atmos had previously attempted to measure motor/propeller combinations using readings from a temperature sensor as the basis to calculate power dissipation.


2 /// Aerospace Test & Validation Vol 2 No. 2


This was a slow procedure and it was difficult to compare results. By comparison, the WT1800E provides up to six measurement channels to enable electrical power measurements of up to six voltages and six currents at a sampling of rate of 2MS/s. Atmos was therefore able


to take measurements at the motor’s power supply, the motor drive circuit and at the motor itself simultaneously. These measurements were used to rapidly calculate power dissipation in the motor drive and the motor. According to Dirk Dokter,


Technical Director & Founding Partner of Atmos, the first tests that were performed were done without using a power analyser and it took over four hours to test each single motor drive combination. “With a power analyser, the test time fell


dramatically and after fine-tuning the power analyser test set-up, the time to test a single motor fell to just 30 minutes,” he says. The other factor that Atmos was aware of was


whether the results given by the analyser were trustworthy. In this respect, after performing a number of tests, Dokter has no hesitation in placing his trust in the instrument. “I didn’t have to worry about the WT1800E. I know


that the WT1800E was telling me the actual power dissipated and I had total confidence in the values displayed on screen,” he says.


THE WT1800E POWER ANALYSER The Yokogawa WT1800E is a high-performance power analyser, which guarantees a power accuracy of 0.05% of reading, plus 0.05% of range. Unlike measuring instruments which are not designed to measure power as their primary function, the power measuring accuracy of the WT1800E is specified for all factors such as power factor, crest factor, phase angle error, temperature range, warm-up time, stability period and common mode rejection. The high levels of stability also mean that measurements are consistent when repeated over the lifetime of the instrument. The WT1800E was developed to be flexible enough


❱ ❱ Smooth power delivery in all modes of operation of the Atmos Marlyn UAV was tested using specialist power measurement instrumentation


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