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Active Vibration Control Using Elect...

Cho, Changik,

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Active Vibration Control Using Electric Rotor Torques in Evtol Aircraft /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Active Vibration Control Using Electric Rotor Torques in Evtol Aircraft // Changik Cho.
作者:	Cho, Changik,
面頁冊數:	1 electronic resource (117 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-05, Section: A.
Contained By:	Dissertations Abstracts International86-05A.
標題:	Aircraft. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31631281
ISBN:	9798346377368

Active Vibration Control Using Electric Rotor Torques in Evtol Aircraft /
Cho, Changik,

Active Vibration Control Using Electric Rotor Torques in Evtol Aircraft /Changik Cho. - 1 electronic resource (117 pages)

Source: Dissertations Abstracts International, Volume: 86-05, Section: A.

Electric aircraft are attracting more interest in both commercial and military markets due to their distinctive advantages, including environmental friendliness and reduced maintenance costs. Various electric Vertical Takeoff and Landing (eVTOL) aircraft configurations have been considered to increase hover time and forward flight speed in recent years. Although the battery density increase and significant battery price drop have accelerated the shift towards electric aircraft, eVTOL aircraft experience vibrations due to its propulsion system driven by rotors. Rotorcraft including helicopters and eVTOL aircraft are prone to vibrations caused by rotor excitation, vehicle maneuvers, wind gusts, and separated flow around the rotor hub. Additional vibrations from aerodynamic loads from the main rotor and turbulence over tail surfaces can lead to structural fatigue, component wear, passenger discomfort, and increased maintenance costs.This thesis introduces the novel idea of damping vibration using electric rotor torque on aircraft without compromising flight control. The large inertial and aerodynamic rotor loading and relatively high frequency torque perturbations mean that the rotor speed changes are small, so the rotor thrust and flight control performance are not significantly affected. A motivating example for eVTOL aircraft is a cantilevered beam with a propeller at the tip driven by an electric motor. The equations of motion of this system are obtained using Hamilton's principle, solved analytically in the frequency domain, and approximately in the time domain. Feeding back the beam tip angular rate to the motor torque is shown to asymptotically stabilize all transverse beam vibration modes. The overall vibration control consists of the inner rate feedback damping loop with an outer rotor speed control loop. Experimental frequency response and step response validate the models and show that the closed-loop damping in the first mode is three times higher than open loop with less than 1% rotor speed change for a 3% initial tip displacement. Theoretical results give good agreement with experiments. Parametric studies based on a 12 kg quadcopter indicate that if the rotor inertia is sufficiently large, then the proposed control can provide 8% damping with minimal impact on rotor speed.Nb/rev periodic aerodynamic forces and moments on the rotor blades and wings are the main vibration sources of rotorcraft. An optimal, active vibration controller (AVC) controller, is designed assuming known disturbance location and frequency. The transfer matrix of a single cantilevered wing is calculated and used to feed forward harmonic rotor torques. The wing undergoes aerodynamic disruptions at Nb/rev and the harmonic controller reducesNb/revshear force and bending moment at the cantilevered root by 20% and 58%, respectively, with less than 0.4% RPM rotor speed change.A full-scale quad tiltrotor aircraft model is used to assess the performance of electric rotor torque damping in both airplane and helicopter modes. The structural dynamics of the aircraft are represented using a finite element model of a quad tiltrotor aircraft. Using collocated angular rate feedback on all four rotors provides more than 10% damping in controllable modes. The RMS value of flap-wise angular rate can be reduced by 91% with less than 0.5% RPM rotor speed change in response to a 20% vertical step gust in airplane mode.

English

ISBN: 9798346377368Subjects--Topical Terms:

832698
Aircraft.

Active Vibration Control Using Electric Rotor Torques in Evtol Aircraft /
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520 $a Electric aircraft are attracting more interest in both commercial and military markets due to their distinctive advantages, including environmental friendliness and reduced maintenance costs. Various electric Vertical Takeoff and Landing (eVTOL) aircraft configurations have been considered to increase hover time and forward flight speed in recent years. Although the battery density increase and significant battery price drop have accelerated the shift towards electric aircraft, eVTOL aircraft experience vibrations due to its propulsion system driven by rotors. Rotorcraft including helicopters and eVTOL aircraft are prone to vibrations caused by rotor excitation, vehicle maneuvers, wind gusts, and separated flow around the rotor hub. Additional vibrations from aerodynamic loads from the main rotor and turbulence over tail surfaces can lead to structural fatigue, component wear, passenger discomfort, and increased maintenance costs.This thesis introduces the novel idea of damping vibration using electric rotor torque on aircraft without compromising flight control. The large inertial and aerodynamic rotor loading and relatively high frequency torque perturbations mean that the rotor speed changes are small, so the rotor thrust and flight control performance are not significantly affected. A motivating example for eVTOL aircraft is a cantilevered beam with a propeller at the tip driven by an electric motor. The equations of motion of this system are obtained using Hamilton's principle, solved analytically in the frequency domain, and approximately in the time domain. Feeding back the beam tip angular rate to the motor torque is shown to asymptotically stabilize all transverse beam vibration modes. The overall vibration control consists of the inner rate feedback damping loop with an outer rotor speed control loop. Experimental frequency response and step response validate the models and show that the closed-loop damping in the first mode is three times higher than open loop with less than 1% rotor speed change for a 3% initial tip displacement. Theoretical results give good agreement with experiments. Parametric studies based on a 12 kg quadcopter indicate that if the rotor inertia is sufficiently large, then the proposed control can provide 8% damping with minimal impact on rotor speed.Nb/rev periodic aerodynamic forces and moments on the rotor blades and wings are the main vibration sources of rotorcraft. An optimal, active vibration controller (AVC) controller, is designed assuming known disturbance location and frequency. The transfer matrix of a single cantilevered wing is calculated and used to feed forward harmonic rotor torques. The wing undergoes aerodynamic disruptions at Nb/rev and the harmonic controller reducesNb/revshear force and bending moment at the cantilevered root by 20% and 58%, respectively, with less than 0.4% RPM rotor speed change.A full-scale quad tiltrotor aircraft model is used to assess the performance of electric rotor torque damping in both airplane and helicopter modes. The structural dynamics of the aircraft are represented using a finite element model of a quad tiltrotor aircraft. Using collocated angular rate feedback on all four rotors provides more than 10% damping in controllable modes. The RMS value of flap-wise angular rate can be reduced by 91% with less than 0.5% RPM rotor speed change in response to a 20% vertical step gust in airplane mode.
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