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A new CAD-based model of the occupant/driver for interior and seat design has been developed. Unlike traditional automotive iterative design methods that begin with a 2D human manikin in an environment based on the location of H-point, the 3D ERL manikins determine the initial design positions of multiple occupants based on the simulated interactions of seat, driver package, skeletal linkage system and deflected human tissue. The 3D ERL human body representations come from measurements of posture-critical skeletal landmarks on 102 test subjects combined with measurements of “deflected human tissue” data from 60 test subjects. The result is a set of three dimensional, posture-biofidelic manikins that a computer algorithm optimizes the driver's workplace environment to fit the population range of sizes and postural preferences.

Virtual drivers in math models can design and evaluate the seating package in all classes of vehicles. With the driver's seated geometry constrained by vision and reach to the steering wheel and pedal, seat design is optimized to support all drivers in three back postures to operate the vehicle. The position of each virtual driver model in the seat is calculated from a biomechanical model of seated load distribution with each model represented by functionally correct positions of pelvis and spine as well as the deflected shape of the seated body in a vehicle seat. This geometry is optimized to design or evaluate seats by changing boundary conditions of select variables and functions in the math tool. The math comfort score is calculated from the physical interface between the virtual drivers and the seating package. The weighted sum of scores for all virtual drivers is the population comfort score for the vehicle seating package.

A digital human body model is used to mathematically calculate occupant position in the vehicle package. The unoccupied seat shape that will support the digital human body model is optimized using a biomechanical model of the human body, a load-deflection model of the seat along with manufacturability and safety criteria. By unloading the seat at anatomically comparable landmarks for each digital human body model, as defined by gender and body size, the collection of points on the unoccupied seat surface define a patch. With 3 patches on the cushion and 4 patches on the back, two surfaces representing the centerline of the seat and seat insert can be defined for the population of occupants. This process can be done with constrained or unconstrained vehicle package geometry. The result is a “one seat fits all” design of the unoccupied deliverable seat given the requirements of the ergonomic task of driving the vehicle.

The location of the pelvis in the seated automobile operator is critical for proper packaging and seat comfort design. The pelvis is the skeletal structure which contains the hip joint (H-point) and ischial tuberosity (D-point). The orientation of the pelvis largely determines the curvature in the low back which is supported by lumbar supports in the seat back. A methodology has been developed that uses onboard video and pressure measurement systems to locate the pelvis. This system has been used in a mid-sized vehicle on seated operators driving the vehicle on the highway. This paper describes the methodology and the location of the pelvis in seated automobile operators.

A vehicle laboratory has been developed in which the vehicle operator's posture, pressure distribution, muscle activity, and comfort can be measured while driving on the highway. This instrumented vehicle uses video camera, pressure mats, electromyography, and questionnaires to make these measurements. There is an on-board PC486 to record the data fro later off-line analysis. These data are useful for developing design criteria for seating comfort as well as investigating the real-life position that the operator sits in the vehicle package while driving the vehicle on the highway.

In this paper we present a method for converting the CAESAR full body scanned data into human body models for use in the ERL design software. The ERL software is a comprehensive interior automobile design tool, used in design or evaluation. The 3D CAD occupants in ERL were generated from anatomical cross sections at comparable landmarks and spinal shapes. Skeletal landmarks in the CAESAR data are used to establish segmental coordinates from which cross-sections are defined. The anatomical cross sections are used to re-generate the external shape of the body. Additional skeletal landmarks are calculated using regression equations. Segmental mass distributions are calculated based on segmental volume.

Human accommodation, has undergone rapid changes in the past few years which are outdistancing current concepts, data and design tools. This paper examines the basis of current problems in the application of these tools to the design of safe and comfortable seats. Examples of the types of new data needed are given and the discussion proposes new paths to solve current problems.