PAV-ER
Sep. 2021 - Dec. 2023
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The recent advancement of hybrid and electric vehicles has led to a surge in the number of start-up companies in the urban air mobility/advanced air mobility (UAM/AAM) industry. The PAV-ER project is aimed at assisting the FAA in certifying electric vertical takeoff and landing (eVTOL) aircraft. However, certifying these small electric aircraft presents challenges due to the vast design space. To address this, the PAV-ER testbed is designed to operate with over-actuated controls, providing more degrees of freedom. However, the use of helicopter control also presents unique challenges that need to be addressed.
PAV-ER V1
PAV-ER V1
As a student research assistant, I was responsible for designing parts for the first PAV-ER testbed using CATIA software and rapidly iterating the design. The testbed is assembled with carbon fiber baseplates, pipes, and 3D-printed parts. During a strap-down spool-up test, the first prototype experienced unscheduled rapid disassembly due to vibration and twisting of the arms, causing the propulsion pod structure to fail near the edge. In collaboration with our structure's expert, Sho, I conducted an arm torsion test and improved the design for PAV-ER V2. While waiting for the V2 components, I modified the V1 arm structure to address the torsional rigidity issue, allowing V1 to continue testing before the second prototype was built.
PAV-ER V2
PAV-ER V2
The second prototype of the PAV-ER project features carbon fiber drive shafts as arms, addressing the twisting issue observed during testing of V1. The airframe survived most of the scheduled tests with various control strategies, and flights were successful. To improve testing, I developed a 3-dof test stand and a kit that utilized piezoelectric sheets to sense and log vibrations while supporting the test operation. However, the vibration problem reoccurred at 1600 RPM, with the arms beginning to bend instead of twist. During a test exploring the vibrational behavior near the resonance frequency, the aluminum transmission casing cracked. To address this issue, I recently assembled a new test stand for the single-arm test at 2500 RPM, which showed that we have enough power to pass through the range with heavy vibration. Furthermore, the three-bladed rotor head has been shown to have less severe vibrations.
The Three-bladed PAV-ER
The Three-bladed PAV-ER
After the completion of the test, the V1 airframe was fitted with three-bladed rotorheads while repairs were being carried out on the V2 airframe. The PAV-ER underwent continuous flight tests, during which it was observed that the vehicle was able to maintain stable flight with one rotor off, and at higher rotor speeds with no noticeable resonance at the operating RPM.Â
Dynamic Modeling Support & Design Refinement
Dynamic Modeling Support & Design Refinement
While the controls team is focusing on the flight control law testing, I kept improving the design and supported the validation flight tests for all equipment. I was also conducting hardware examinations on the testbed that wasn't actively flying, to ensure that the alternative airframe is in an operable state.
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