Optimization of Public Seat Functions to Assure a Comfortable Sitting Posture in Diverse Conditions

Abstract

Seat functions for public seats, such as those in railway vehicles, have been designed to assure a comfortable sitting posture. However, the importance of these functions is not widely understood. Public seats are used in a variety of conditions because users have diverse physiques and sitting postures. Thus, design solutions that consider only standard conditions, physiques, and sitting postures are insufficient. The objectives of this study are 1) to clarify the relative importance of seat functions in assuring a comfortable sitting posture and 2) to optimize important seat functions in diverse conditions. First, an analytic hierarchy process (AHP) and a fuzzy analytic hierarchy process (Fuzzy AHP) clarified that the forward tilt function of the seatback and seat swing function are necessary to assume a comfortable sitting posture because they contribute to the fitness of the seatback and prevent the hip sliding force, respectively. However, there is trade-off between satisfying the fitness and preventing the hip sliding force. Second, the seat swing function with a forward tilt function was optimized. The solution is the optimal relationship between the seatback and the seat cushion angles adjusted by the seat swing function to prevent the hip sliding force considering diverse conditions and the forward tilt angles. Finally, a sensory experiment confirmed the effectiveness of the optimized design solution.