Aeronautics and astronautics
http://hdl.handle.net/1773/4889
Thu, 22 Feb 2024 15:43:40 GMT2024-02-22T15:43:40ZModeling of Active Aeroservoelastic Systems
http://hdl.handle.net/1773/51076
Modeling of Active Aeroservoelastic Systems
Su, Anthony Mark
This thesis demonstrates the synthesis and testing of a physics-based aeroservoelastic mathematical model for a flexible wind tunnel model. Ground vibration testing of the wind tunnel model is detailed herein. An aeroservoelastic mathematical model was synthesized for the wind tunnel model from a finite-element analysis and first principles. The wind tunnel model's structural dynamic, aerodynamic, and actuator models were coupled together into a linear time-invariant state-space model. The wind tunnel model's frequency response was measured experimentally at the University of Washington's 3x3 low-speed wind tunnel. The frequency response was used to adjust the mathematical model to account for physical phenomena which were not well captured by the initial model. Results show that the updated mathematical model is better able to capture the relevant physics and responses of the wind tunnel model. The results of this study can be used as the baseline for further system identification or for aeroservoelastic control law design.
Thesis (Master's)--University of Washington, 2023
http://hdl.handle.net/1773/51076Proof-of-Concept In-Situ Diagnostic for Magnetically Shielded Hall Thruster Erosion
http://hdl.handle.net/1773/51075
Proof-of-Concept In-Situ Diagnostic for Magnetically Shielded Hall Thruster Erosion
Rieco, Isabella
Validating flight-ready hardware for magnetically shielded Hall thrusters is criticallydependent on lifetime testing. Traditionally, measuring the erosion of the inner pole requires
breaking vacuum, a process that can influence test results, and typically allow for erosion
measurements only after extensive durations. A proof-of-concept in-situ erosion diagnostic is
explored to assess its feasibility for more accelerated testing. The diagnostic operates by using
a conductive material, specifically ITO-coated glass, and tracking the change in its electrical
resistance over time. This change in resistance is directly correlated to the material’s erosion
rate. Testing was conducted under three different operating conditions: 200V, 250V, and
300V in the plume of a magnetically shielded Hall thruster along it’s centerline. Theoretical
results were also shown for the probe’s behavior at the inner pole. The results demonstrated
that the resistance change exhibited an inverse trend, in line with theoretical expectations,
and the probe was capable of detecting resistance changes as low as 0.05 Ω/s in the plume
and theoretical resolution of 0.04 Ω/s at the inner pole. Looking ahead, future improvements
will focus on mitigating thermal variations and employing more robust materials that erode
more slowly, enhancing the diagnostic’s durability and accuracy at the inner pole. The
successful implementation of this approach — placing a conductor in plasma and measuring
its resistance as it erodes — paves the way for the development of in-situ erosion sensors for
accelerated Hall thruster lifetime testing.
Thesis (Master's)--University of Washington, 2023
http://hdl.handle.net/1773/51075Optimal Control for Electrically Propelled Aircraft and Urban Air Mobility Network
http://hdl.handle.net/1773/51073
Optimal Control for Electrically Propelled Aircraft and Urban Air Mobility Network
Wang, Mengyuan
This dissertation aims to address fundamental challenges in the field of Urban Air Mobility (UAM) through optimal control strategies. Three key aspects are studied to enhance the operation and performance of UAM. First, a trajectory optimization algorithm for All-Electric Aircraft (AEA) is proposed, along with the corresponding Simulink models, to minimize the operating cost of AEA. The impact of battery dynamics on optimal trajectories is explored by integrating several battery models with distinct fidelity into the corresponding optimal control problems. Second, an energy management system is designed for Hybrid-Electric Aircraft (HEA) to optimize fuel consumption. Numerical results for two HEA models indicate the limited fuel-saving achieved by using the engine to charge the battery during flight. This observation leads to the investigation of two parallel hybrid electric configurations, aiming to answer the question of whether it is worthwhile to charge the battery during flight at all. A finite-dimensional optimization problem is formulated, and numerical results indicate that increasing onboard battery capacity is more fuel-efficient than in-flight charging. Finally, two important topics related to the UAM are investigated: optimal vertiport selection problem and task assignment and vehicle routing problem. For the vertiport selection problem, a mixed-integer programming approach is developed and applied to a hybrid ground-air network to improve the traffic performance. As for the task assignment problem, a centralized approach is adopted to assign a sequence of tasks to each vehicle, maximizing the overall profit. The problem is transformed into an identification of multiple paths in a task network and is solved using a greedy algorithm.
Thesis (Ph.D.)--University of Washington, 2023
http://hdl.handle.net/1773/51073Development of a 5N-moment Multi-Fluid Plasma Model for D-T Fusion in an Axisymmetric Z Pinch
http://hdl.handle.net/1773/51074
Development of a 5N-moment Multi-Fluid Plasma Model for D-T Fusion in an Axisymmetric Z Pinch
Takagaki, Yu
The thermonuclear fusion process in a D-T Z pinch is investigated by developing the multi-component, deuterium-tritium-helium-electron, model including fusion reactions and interspecies collisions via the WARPXM simulation framework. The geometric source terms are implemented into WARPXM to solve axisymmetric problems in cylindrical coordinates without changing the code’s infrastructure. The 5N-moment growth rates peak at the expected wavenumber and further stabilize at large wavenumbers in a manner that agrees with previously published studies using higher fidelity kinetic models. The radially-sheared axial flow, ∂rvz ̸= 0, stabilizes the sausage instabilities significantly as observed in the Fusion Z-pinch Experiment (FuZE) at the University of Washington. Braginskii viscosity and thermal conductivity also indicates the stronger stabilizing effects with decreasing plasma collisionality. The energetic alphas produced in the core of the Z-pinch plasma expand radially and interact with the azimuthal magnetic field, which drives an axial current of alpha particles. The primary energy cascade initiates from energetic alphas to electrons, and eventually the electron energy transfers to the ions. The increase in fusion gain becomes significant when the plasma pinch current exceeds 1.35 MA, which corresponds to a pinch radius equal to the gyroradius of a D-T fusion alpha. While never reaching ignition, the fusion gain increases from 8.14 to 151.8 with the increasing pinch current and 7% of the alpha heating fraction.
Thesis (Ph.D.)--University of Washington, 2023
http://hdl.handle.net/1773/51074