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Time and Frequency Analysis of a Speed-Controlled Rotor in Hover

Matthew Asper, Jayant Sirohi, The University of Texas at Austin

https://doi.org/10.4050/F-0079-2023-18064

Abstract:
As electric propulsion technologies advance, rotor speed control is becoming viable for manned VTOL aircraft primary propulsion. These control methodologies are an area that still needs to be explored, especially for high Reynolds number conditions. For this reason, a 2 meter diameter, speed-controlled rotor system was tested in hover. The rotor was driven by an electric motor, and step and sine inputs of 3% of the nominal speed were commanded at blade loadings up to CT /σ = 0.11 to determine the time and frequency response of rotor thrust and torque. Sine inputs were tested at frequencies up to 25% of the rotor speed. The data was used to validate an integrated aerodynamic and powertrain model of a speed-controlled rotor. A dynamic inflow model with blade element momentum theory predicted the aerodynamic loads, and an electromechanical model was used to account for the motor and control dynamics. Findings showed that there was good agreement between measured and predicted motor speed, thrust, and torque time response. Experimental results showed a faster response in the measured thrust and a lower peak torque versus the model. The model was able to capture the correct trends in magnitude and phase for motor speed, thrust and torque for all conditions tested. Inertial torque dominated the peak torque response, resulting in a linear increase with frequency of the input speed variation, whereas aerodynamic torque added damping and resulted in a negative offset in phase. Discrepancies between the model and the experiment may be due to the algorithms programmed into the motor controller, which were not modeled. The results of this study will be useful for informing engineers looking to design for rotor speed control.


Time and Frequency Analysis of a Speed-Controlled Rotor in Hover

  • Presented at Forum 79
  • 12 pages
  • SKU # : F-0079-2023-18064
  • Electric VTOL

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Time and Frequency Analysis of a Speed-Controlled Rotor in Hover

Authors / Details:
Matthew Asper, Jayant Sirohi, The University of Texas at Austin