H-point simulation in musculoskeletal models of seating

This paper investigates the opportunity to simulate soft surfaces in rigid body inverse dynamics musculoskeletal models. More precisely, the paper addresses the change of H-point location in response to the forces produced by the body against the environment, such as pedal forces or steering forces. This situation cannot be handled by basic inverse dynamics, because the elastic deformations contribute to the movement but are unknown when the simulation begins.
We demonstrate how a new inverse dynamics analysis method called force-dependent kinematics (FDK) can be used to simulate the body’s movement in a cushioned seat. In other words, the method allows some motions to be output rather than input in the inverse dynamics simulation.
The paper briefly introduces the basis of the method, presents a seated human model and shows sample simula-tion results for the case of emergency braking.
It is concluded that H-point and seated body-seat posture can be simulated given information about the nonlin-ear compliance, i.e. force-deformation curves of the seat cushions and the soft tissues in contact with the seat. The latter information can be obtained either experimentally or by advanced finite element simulation.