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New models are being developed to represent the geometry and movements of people in seated postures. The positions and motions of the torso skeletal structures for different amounts of lumbar curvature have been studied and represented in side view, two dimensional computer models of the average man, small woman, and large man. Some further developments for the average man include: 1. two dimensional, articulated drafting template, 2. three dimensional computer model of the skeletal system with soft tissue thicknesses added to represent the external body contours on the back of the torso, and 3. model of forces and moments between body segments based on seated posture, body segment masses, and seat surface forces. This paper describes these new biomechanical models and their potential uses in designing seats that more comfortably fit and move with people.

To assist automotive seat development and evaluation, a technique for predicting the posture of seated occupants has been developed. The method involved modeling the torso geometry and articulation of a mid-size male, based on information presented in SAE paper number 930110 [1]. This mid-size male model, known as 2-D JOHN, was developed in a commercial kinetic modeling software and used in a comparative seat evaluation study between a current production automotive seat and a prototype articulating seat. The 2-D JOHN model was supported a greater range of postures, defined as Total Lumbar Curvature (TLC) and Torso Recline Angle (TRA), in the prototype seat than the automotive seat.

The geometric, inertial, and joint characteristics of two Part 572 crash test dummies were measured to provide input to the MVMA 2-D occupant model. Segments of the dummies were defined which correspond to the links of the model and coordinate axes were defined for each segment. The center of gravity of each segment was located and its coordinates were measured along with the locations of joint centers, instrument mounts, and other significant geometric features. The mass moment of inertia for each segment about a lateral axis through its center of gravity was measured. The geometric and inertial measurements are presented on summary sheets for each segment with the hardware definition, coordinate system, and special notes for that particular segment. These summary sheets present the data in a format that is readily usable for defining computer model input.

The ASPECT (Automotive Seat and Package Evaluation and Comparison Tools) Program has developed the next generation SAE 3-D H-Point testing manikin. During the development of the ASPECT manikin, new data were collected on how people loaded different regions of a seat and how these loads varied with different postures. These data, along with a computer model of the ASPECT manikin, were used to assist in the development of a human-like weight distribution for the new seating device, the ASPECT manikin.

Auto and boat racers suffer fatigue and injury from loading of their necks. While racing, a driver's neck often becomes fatigued because it must support the weight of the head and helmet. In crashes, extreme motions of a driver's unrestrained head relative to the restrained torso cause excessive loads in the driver's neck. These neck loads between the head and torso can cause severe or fatal injuries such as spinal dislocations and basilar skull fractures. A new type of head and neck support has been developed that restrains the driver's head relative to their torso to reduce undesirable head motions and neck loads that cause fatigue and injury. This paper describes recent work, using computer crash simulations, crash dummy tests, and driver experiences, to better understand head and neck injury in racing and to evaluate the performance of a new head and neck support.