Predicting ground reaction forces of human gait using a simple bipedal spring-mass model.

Aircraft design must be lightweight and cost-efficient on the condition of aircraft certification. In addition to standard load cases, human-induced loads can occur in the aircraft interior. These are crucial for optimal design but difficult to estimate. In this study, a simple bipedal spring-mass model with roller feet predicted human-induced loads caused by human gait for use within an end-to-end design process. The prediction needed no further experimental data. Gait movement and ground reaction force (GRF) were simulated by means of two parameter constraints with easily estimable input variables (gait speed, body mass, body height). To calibrate and validate the prediction model, experiments were conducted in which 12 test persons walked in an aircraft mock-up under different conditions. Additional statistical regression models helped to compensate for bipedal model limitations. Direct regression models predicted single GRF parameters as a reference without a bipedal model. The parameter constraint with equal gait speed in experiment and simulation yielded good estimates of force maxima (error 5.3%), while equal initial GRF gave a more reliable prediction. Both parameter constraints predicted contact time very well (error 0.9%). Predictions with the bipedal model including full GRF curves were overall as reliable as the reference.

Seat cushions made of warp knitted spacer fabrics influence seat transmissibility.

The aim of this study was to compare the application of different warp knitted spacer fabrics on a car seat shell to a standard seat in terms of vertical seat transmissibility. Furthermore, the results obtained by human subject tests were compared to results of an anthropodynamic dummy test. Experiments were conducted on a vertically actuated platform under laboratory conditions with 16 human subjects and an anthropodynamic dummy. Seat Effective Amplitude Transmissibility of the seat pan and the seat backrest were calculated to evaluate ride quality. Seat transmissibility ranged between 73.6% for backrest and 177.7% for pan. Based on the results of statistical tests, the hypothesis that the transmissibility of a seat would be influenced by seat cushion conditions was accepted (p < 0.05). It was also shown that an anthropodynamic dummy test could replace tests with human subjects (r2 = 0.907) if the target population was matched sufficiently.

Analytical evaluation of the effects of inconsistent anthropometric measurements on joint kinematics in motion capturing.

Clinical decisions based on gait data obtained by optoelectronic motion capturing require profound knowledge about the repeatability of the used measurement systems and methods. The purpose of this study was to evaluate the effects of inconsistent anthropometric measurements on joint kinematics calculated with the Plug-in Gait model. Therefore, a sensitivity study was conducted to ascertain how joint kinematics output is affected to different anthropometric data input. One previously examined gait session of a healthy male subject and his anthropometric data that were assessed by two experienced examiners served as a basis for this analytical evaluation. This sensitivity study yielded a maximum difference in joint kinematics by the two sets of anthropometrics of up to 1.2°. In conclusion, this study has shown that the reliability of subjects' anthropometrics assessed by experienced examiners has no considerable effects on joint kinematics.