Abstract

Personalized vehicles have gained significant popularity in urban environments due to their simplicity and convenience. Among these, unicycles are emerging as one of the preferred choice for short-distance travel. However, the unique dynamics of unicycles present challenges related to ride comfort and safety, particularly when they are exposed to vibrations from uneven road surfaces. Understanding the biodynamic responses of riders under such conditions is critical for optimizing the unicycle design and ensuring compliance with vibration exposure standards. This study investigates the biodynamic responses of a unicycle rider subjected to whole-body vibrations across various road surfaces. The human body is modelled as a lumped parameter system with 13 degrees of freedom (DOF), where the unicycle is modelled analogous to a quarter-car system. The equations of motion were derived using the Euler-Lagrange method, and the biodynamic responses were evaluated in accordance with the ISO 5982-2001 standard. Key metrics such as Foot-to-Head Transmissibility (FTHT), Driving Point Mechanical Impedance (DPMI), and Apparent Mass (AM) are derived and computed to evaluate the vibration behaviour of the system. In addition, the road surfaces were modelled following the ISO 8606 standard, and the effects were incorporated into the rider-system dynamics. The peak acceleration values for individual body segments were analyzed for different road conditions, highlighting the pelvis and thighs as the segments experiencing the highest vertical vibration transmission. In addition, the primary response of the system was observed at approximately 9-10 Hz, which can be attributed to the vibration modes of the thigh and pelvic pitches.