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A new experimental seat was designed to investigate sitting biomechanics. Previous literature suggested links between sitting discomfort and shear force, however, research on this topic is limited. The evaluation of sitting discomfort derived from past research has been primarily associated with seat pressure distribution. The key innovative feature of the experimental seat is not only pressure distribution evaluation but shear forces as well. The seat pan of the experimental seat compromises of a matrix of 52 cylinders, each equipped with a tri-axial force sensor, enabling us to measure both normal and tangential forces. The position of each cylinder is also adjustable permitting a uniform pressure distribution underneath the soft tissue of the buttocks and thighs. Backrest, armrests, seat pan and flooring are highly adjustable and equipped with forces sensors to measure contact forces.

The majority of existing studies on arm reaching were either limited to the determination of reach envelopes or to motion analysis for understanding motion control strategies and/or their simulation. For ergonomic applications of digital humans, it is important to simulate motion and also to predict the discomfort felt by the virtual operator. Generic arm reaching movements in a seated position were studied in order to investigate the effects of age, gender and target position on motion and discomfort. The main results of discomfort analysis will be reported in the present paper. The analysis of the discomfort ratings has shown that elderly subjects differed significantly from younger ones. The results showed that both target orientation plane and height had a quadratic effect on the discomfort. The minimum was located in the sagittal plane at the half height between the seat and shoulder. Discomfort increased almost linearly with the distance.

Both motion simulation and discomfort evaluation are needed for a design engineer when using a digital human model. Thanks to recent progress on motion capture and motion modeling, simulating complex motions in industrial application oriented becomes possible. However, how to evaluate the discomfort associated with such complex motions is another challenge for digital human modeling researchers. In collaboration with French car makers, we have investigated the issue of how to build generic predictive discomfort models of highly environment-constrained motions such as car ingress/egress motions. The purpose of this paper is to present a novel concept called ‘neutral movement’ and to show how it can be used for discomfort modeling of environment-constrained motions. In this paper, the discomfort of car ingress/egress movements will be analyzed with help of the concept of neutral movement. The advantages and limitations of the proposed discomfort modeling approach will also be discussed.

This paper focuses on full body dynamical analysis of car ingress/egress motion. It aims at proposing an experimental protocol adapted for analysing joint loads using inverse dynamics. Two preliminary studies were first performed in order to 1/ define the main driver/car interactions so as to allow measuring the contact forces at all possible contact zones and 2/ identify the design parameters that mainly influence the discomfort. In order to verify the feasibility of the protocol, a laboratory study was carried out, during which two subjects tested two car configurations. The experimental equipment was composed of a variable car mock-up, an optoelectronic motion tracking system, two 6D-force plates installed on the ground next to the doorframe and on the car floor, a 6D-Force sensor between the steering wheel and the steering column, and two pressure maps on the seat. Motions were reconstructed from measured surface markers trajectories using inverse kinematics.

This study was motivated by the simulation of the muscular forces developed during a clutch pedal operation. Fifteen subjects took part in the experiment. Four design parameters (seat height, pedal travel, pedal travel inclination, pedal resistance) were controlled. 28 configurations were tested. For each trial the subjects were asked to rate the perceived discomfort. Individual muscular forces of the left leg for each trial were simulated using motion reconstruction, inverse dynamics and static optimization. The analysis of these simulated muscular forces gave an insight into the way a clutch pedal operation is performed in terms of muscular exertion and coordination. Similarities in muscular force patterns of different subjects were found. The way a change in conception parameters of a car interior affected this muscular exertion was also investigated. This last point revealed that some conception parameters did affect muscular forces significantly.

Realistic simulation of human posture and movement is one of key requirements for digital human models for workplace design. In a recent European research project REAL MAN (IST 2000-29357), we have suggested a data-based motion simulation approach, which includes motion capture, model-based motion reconstruction, motion analysis and data structuration, motion simulation and discomfort estimation. After the REAL MAN project, we have decided to apply this approach and to create a complete in-vehicle reach motion database for car interior design. The objective of this paper is to show our in-vehicle reach motion database. Two female and four male subjects participated in motion data collection. Each subject carried out 64 reach movements which covered 17 common driver’s control command reaches. Motion data were analyzed in order to identify key kinematic characteristics of each motion and then structured according to subject’s anthropometric information; task and command location.

This paper investigates the feasibility of calculating joint forces and moments during a whole body truck cabin ingress/egress motion. For such a task, it is difficult to evaluate a future truck instep as the influences of the architecture parameters are complex over the motion and the discomfort feeling. In order to evaluate the future product at an early stage of the design process, Digital Human Models (DHMs) are interesting tools. However, most existing DHM simulation packages can only efficiently evaluate the kinematics of postures where the dynamics of the whole motion is necessary for such a task. The enhancement of DHMs towards a dynamic analysis and modeling is therefore necessary. In this study, the motions of subjects entering and exiting an adjustable truck cabin were measured by mean of an opto-electronic motion capture system and six load sensors. The joint angles were then calculated using an inverse kinematics method.

Computational finite element (FE) human body models (HBM) are used to estimate internal loads and soft tissue deformation, which cannot be easily measured experimentally, for seating discomfort investigation. However, most existing models only represent a limited number of body sizes and postures and cannot be easily personalized and repositioned, which limits their applicability. In recent years, an open source software package has been developed within the European project PIPER (available at www.PIPER-project.org) to help personalize and to position an HBM used for crash injury simulation. In addition to the personalizing and positioning tools, a child model has also been developed and is also now available. The present study aims to derive an adult male HBM to study seating discomfort from the PIPER Child model using the PIPER personalizing tools and information with external body shape and partial internal skeleton of an adult as targets.

Recently, we proposed a unified data based approach which aimed at predicting both reach envelopes and reach discomfort for a digital human model [1]. In this approach, four reach surfaces, from half-flexed arm distance to maximum reach with torso participation, need to be defined. The discomfort associated with a point on each surface is defined at first. Then, the discomfort of an intermediate distance between two reach distances is interpolated. The proposed approach was demonstrated on a reaching task corresponding to push a toggle switch from a seated posture without seat back. As data were collected in an environment which is different from the driving situation, these data can not be directly applied to driver's reach capacity and discomfort. In this study, we will apply this approach for in-car driver's reach for predicting different reach envelopes and discomfort.

Improvement in the accessibility assessment of the seatbelts using a Digital Human Model requires a precise description of driver belt donning movement and of the associated discomfort. In order for automotive designers to be able to simulate seatbelt reaching movement, a general approach of motion simulation for complex and specific tasks has been proposed in this paper. It consists of three steps: constitution of a structured database, selection of an appropriate movement and its adaptation to meet new constraints. From an experiment, a database of 644 movements of automotive seatbelt reaching movements has been built-up. In order to structure the database, the temporal and spatial characteristics of the trajectories of main markers (e.g. markers attached to the hand and the torso) as well as joint movements were analysed, allowing us to identify motion control strategies.