A System-Dynamics-Based Hazard Analysis of Inverted-Pendulum Human Transporters

Best practices in product design require engineers to perform preliminary hazard analyses on the most promising conceptual designs, as well as a more rigorous hazard analysis when the details of the product are being finalized. When the product is a complex dynamic system that interacts directly with a human, the engineers must consider the wide range of possible motions and forces that the device could create. Such an analysis goes beyond a simple thought exercise and requires detailed knowledge about the system dynamics and operating environment. This paper presents such an analysis of an inverted-pendulum human transporter. The list of hazards is constructed by using fundamental knowledge of the dynamics and the mechanical design obtained through simulation and experimentation. However, the dynamics are so complex that the list is augmented with hazards that are revealed by searching through accident videos posted on the Internet. The severity of each hazard is estimated using an energy-based measurement of the hazard onset conditions. While this case study is interesting, it also provides a systematic approach to hazard analysis that can be applied to other complex and dangerous dynamic systems.