Assessment of optimal passive suspensions regarding motion sickness mitigation in different road profiles and sitting conditions

Automated vehicles (AVs) are expected to lead the evolution of mobility. Motion sickness, known as car sickness, is one of the main issues AVs will face, and could jeopardise their wide impact. However, a limited work has been done on how the optimisation of suspension dynamics could contribute. In this direction, this paper explores the mitigation of car sickness and the improvement of ride comfort through the optimisation of passive suspension systems. More specifically, a half car model, which represents a passenger vehicle from IPG/CarMaker, is used to optimise front suspension system for minimising comfort, but also maintaining vehicle handling while the vehicle is driving over two different road classes. The evaluation of comfort is conducted using the common standardised metric suggested by ISO-2631. After having obtained the optimum design solutions, the optimal solutions are simulated using IPG/CarMaker by assigning the road profiles on a 23 km long countryside road path. Then, vehicle accelerations are transferred to the occupant's head using appropriate models from the literature for both back-on and back-off sitting conditions. Afterwards, car sickness and ride comfort are further assessed to explore in detail how the tuning of the suspension systems through optimisation has minimised the first and enhanced the latter. For the assessment of car sickness, a three dimensional detailed biomechanical human model is used. The results imply that the pitch velocity seems more suitable, as a cost function for optimising the suspension systems with regards to motion sickness mitigation. Therefore, it should be considered either on its own or in combination with metric suggested by ISO-2631.