A numerical tool to simulate the kinematics of the ingress movement in variably-dimensioned vehicles for elderly and/or persons with prosthesis

This paper presents a method for simulating the kinematics of the vehicle ingress movement of elderly people and/or people with prostheses (represented by a humanoid mannequin with a head, trunk, pelvis and lower limbs) in variably-dimensioned vehicles, starting from real experimental data. To solve this “complex” problem, we propose a three-stage method. The first stage concerns the construction of an “exploitable” movement database, containing movements resulting from the numerical processing of the ingress movements measured in experiments carried out on two vehicles with 2 distinct geometries. The second stage, consisting of 4 phases, analyzes and automatically identifies the ingress movement strategies. By the end of this stage, 2 ingress strategies and 6 sub strategies were identified. The third stage is the simulation. It uses the results from stages 1 and 2 to simulate the ingress movement of a subject in the database, adopting a given sub-strategy for a vehicle with a different geometry. The simulation of the ingress movement of the same subject but for another vehicle is formulated as an inverse kinematics problem, which is solved by constrained nonlinear programming.Simulations involving elderly people and/or people with prostheses made it possible to validate the proposed method for the two ingress strategies. Despite the differences with the measured movements, the simulated movements conform to the sub-strategies adopted by the subjects during the experiments. Furthermore, the simulations made it possible to partially explain the shifts in strategy of some subjects when they changed vehicles during the experiments. Finally, simulations on fictitious vehicles highlighted some of the limitations of our simulation tool. This study opens several perspectives for future research. For example, we could improve the simulation tool by considering the subjects' intra-individual differences.Relevance to industryThis study can aid ergonomists and car manufacturers to simulate the ingress movement in variably-dimensioned vehicles for elderly and/or prosthesis having persons. The results of the simulations can be used in the products' (Vehicles) evaluation and adaptation processes. The developed methodology can be extended to the simulation of other movements as it can be integrated into digital human models (DHMs) software.