Flight dynamics and handling qualites of electric quad-rotor aircraft for urban air mobility applications
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Authors
Walter, Ariel
Issue Date
2024-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Aeronautical engineering
Alternative Title
Abstract
The growth of Future Vertical Lift and Advanced Air Mobility programs has led to thedevelopment of a large variety of novel electric Vertical Take-Off and Landing (eVTOL)
aircraft concepts. In this thesis, the viability of the use of a quad-rotor configuration for
Urban Air Mobility (UAM) applications is examined based on flight dynamics and handling
qualities considerations.
An isolated, variable-RPM rotor is first considered, and an examination is conducted
of the effects of increasing rotor size on response time and power consumption, due to
the increasing rotor blade inertia. With variable-RPM, larger rotors may not be responsive
enough for effective operation without relatively over-sized power-trains. In order to examine
the effects of scaling up typical quad-rotor platforms on power-train requirements, variable-
RPM quadcopters of increasing size are simulated in hover. Motor weight fractions are
found to be notably higher for the larger quadcopters, highlighting the relative lack of control
authority of variable-RPM inputs for producing changes in thrust. The effects of disk loading
on the control authority are also considered. Increased disk loading results in increased trim
power, but is shown to significantly reduce estimated motor weight.
As an alternative to variable-RPM alone, a UAM-scale quadcopter with a hybrid control
scheme is proposed to improve the flying qualities of the quadcopter. Hover and forward
flight analysis is performed on a single-passenger, UAM-scale quadcopter with both variable
rotor speed and collective pitch control. With these redundant controls, power consumption
can be increased to improve authority of the pitch inputs for changes in rotor thrust. Hybrid
control mixing is implemented using a complementary filter, allowing the aircraft to use
pitch-control for short-term responses and RPM-control for trim. The benefits of this hybrid
control scheme are demonstrated through simulation of hot/high/heavy conditions, where
trimming with RPM-control allows the pitch actuators to maintain margin for maneuvers.
Hybrid control allows the aircraft to reap the benefits of pitch-control for maneuverability,
while maintaining stall margin by using RPM-control for trim.
In order to perform pilot evaluations of the handling qualities, a real-time capable
simulation model is developed for the hybrid control quadcopter. Four control modes are
flown by test pilots in a flight simulator. Three hybrid control configurations (Eco, Standard, and Sport modes) are evaluated, along with a baseline variable-RPM case. The RPM
control case is shown to be undesirable to pilots due to its increased delays associated with
rotor acceleration. Standard and Sport modes perform the best overall, though some pilot
comments suggest that Sport mode may be overly aggressive. Power-efficient Eco mode has
the lowest Handling Qualities Ratings due to its slow response and reduced magnitude of
commands. Overall, it is shown that the hybrid control quadcopter is able to significantly
outperform its variable-RPM counterpart in piloted simulation of Mission Task Elements.
Description
May2024
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY