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Browsing Staff publications (AA) by Subject "4001 Aerospace engineering"

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    Control allocation problem transformation approaches for over-actuated vectored thrust VTOLs
    (Elsevier, 2025-06-01) Enenakpogbe, Emmanuel; Whidborne, James F.; Lu, Linghai
    One main challenge of vectored thrust VTOLs is actuator thrust control saturation because it may lead to undesired behaviour and loss of control if the control channels are not prioritised. Another challenge of vectored thrust VTOLs is that the vectored thrust results in non-linear effector mapping preventing the direct use of standard linear control allocation approaches. Linear control allocation approaches have lower online computational and complexity burden, and have simplier requirements for fault tolerance and reconfigurability than nonlinear control allocation approaches. This paper proposes three real-time control allocation approaches for transforming a nonlinear control allocation problem to a linear problem so that classical linear control allocation approaches can then be used. The approaches which addresses the two main challenges of the particular VTOL configuration are then tested using three selected flight test manoeuvres on a generic over-actuated vectored thrust three degrees of freedom planar VTOL with no aerodynamics. The first approach transfers the non-linearity from the effector mapping to the computation of the actuator limits by formulating the real controls in cartesian form and then converts the physical actuator limits from polar to cartesian form. The second approach transforms the non-linear effector mapping to a linear mapping via numerical linearisation of the non-linear effector mapping in real-time. The third approach is similar to second approach except an extra step which transforms the virtual controls from cartesian to polar before performing an analytical linearisation resulting in a different and more complicated linear Effector mapping. The results demonstrate the effectiveness of the proposed control allocation schemes to allocate remaining control authority to higher priority and critical control channels in order to maintain operational safety and stability during certain flight conditions while there is limited control authority.
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    Energy optimization strategies for automatic tiltrotor electric vertical takeoff and landing aircraft
    (AIAA, 2025-03-25) Kang, Namuk; Lu, Linghai; Whidborne, James F.
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    Wind tunnel installation effects on a high-speed exhaust flow under large blockage
    (American Institute of Aeronautics and Astronautics (AIAA), 2025-05-19) Tsentis, Spyros; Goulos, Ioannis; Debiasi, Marco; Prince, Simon; Pachidis, Vassilios; Zmijanovic, Vladeta; Saavedra, Josè
    This study presents a numerical investigation of wind tunnel installation effects on the exhaust flow for a high-speed system under a blockage ratio of 16.5%. The configuration features a nozzle and a cavity embedded at the base of an ogive-cylindrical body and is representative of future, high-speed exhausts. The work is motivated by the need of testing large, powered-on models and the size of most closed transonic tunnels available in academic research facilities. This combination leads to high blockage ratios and therefore severe flow distortion. The objective is to examine the installation effects and quantify the base flow similarity relative to unbounded conditions. The numerical approach is validated against experimental data. A jet vectoring effect is identified due to the pylon, which is intensified under choked tunnel operation. Additionally, a methodology is proposed, which allows base pressure to be compared to unbounded flow conditions. Results show that the pressure distribution agrees within 1.5% and 0.1% for the base and cavity walls, respectively. This demonstrates that local aerodynamic similarity can be established between large-blockage, tunnel-tested conditions and unbounded flow through the proposed approach. This enables the use of small-scale facilities for base flow studies of high-speed exhausts under large blockage.