Mixed Motion Sickness in eVTOL Aircraft: A Survey of Mechanisms, Measurement, Estimation, and Mitigation

Electric vertical takeoff and landing (eVTOL) aircraft are anticipated to become a cornerstone of future urban air mobility (UAM) and intelligent three-dimensional transportation systems in smart cities. Enhancing passenger comfort is crucial for improving public acceptance of eVTOLs. However, motion sickness (MS) monitoring and mitigation pose key challenges in this context. This paper presents a comprehensive review of MS research for eVTOL applications, focusing on mixed MS induced by the combined effects of physical motion and visual stimuli in intelligent eVTOL cockpits. The underlying theories and MS-related eVTOL characteristics are first examined, based on which the technologies capable of quantifying and estimating mixed MS are then reviewed. The usage of multi-modal visual and physiological signals combined with classical MS theories is highlighted. Subsequently, the methods for MS alleviation in eVTOLs are investigated. Lastly, this work delineates critical challenges stemming from eVTOL feature complexity, eVTOL-specific MS data scarcity, intricate mixed MS modeling, and its neglect in intelligent flight systems. A potential monitoring and mitigating framework for MS in eVTOL is proposed to bridge these gaps and advance practical development.