Life-Saving Locomotive Bumpers (Donate to Rail Safety)
Motivated by the thousands of pedestrians killed each year in train impacts, Professor Paden and his collaborators are investigating the life-saving capability of locomotive bumpers. The head motions produced by various concepts are modeled and analyzed using the Head Injury Criterion (HIC) frequently used in the automotive industry. Surprisingly, the analyses show that a number of concepts can achieve survivable HIC values for impacts with a locomotive traveling at 100km/h. Two of the concepts eject the pedestrian trackside with at a velocity of roughly 40km/h and the risk of ground-impact injury can be compared to survivable automobile accidents. The required bumper lengths are a fraction of the overall length of a locomotive and are thus feasible for practical implementation. This basic feasibility research motivates future investigations into the detailed design of bumper shapes, multi-body pedestrian simulations, and finite-element injury models. Please read “On the Feasibility of Life-Saving Locomotive Bumpers.” Donate and support this research here.
Performance of MEMS Resonant Sensors
MEMS inductor-capacitor (LC) resonant pressure sensors have revolutionized the treatment of abdominal aortic aneurysms. In contrast to electrostatically driven MEMS resonators, these magnetically coupled devices are wireless so that they can be permanently implanted in the body and can communicate to an external coil via pressure-induced frequency modulation. Motivated by the importance of these sensors in this and other applications, this research develops relationships among sensor design variables, system noise levels, and overall system performance. Specifically, new models are developed that express the Cramér-Rao lower bound for the variance of resonator frequency estimates in terms of system variables through a system of coupled algebraic equations, which can be used in design and optimization. Further, models are developed for a novel mechanical resonator in addition to the LC-type resonators.
High-speed mechanisms are important in a wide range of products and manufacturing systems. In this consulting project, a novel electromechanical valve actuation system comprised of a linear actuator, valve, and energy storing cam/spring mechanism was developed. The system dynamics are modeled using Lagrangian mechanics, and a minimum-energy point-to-point optimal control problem is solved to find an optimal trajectory and input. The optimal input is used as a feedforward component in a transition controller to move the valve between the open and closed positions. Between transitions, a simple linear controller stabilizes the valve in the open and closed positions. A high-order model capturing the distributed nature of valve springs is used to validate state constraints related to positive cam/follower forces and a nonslip condition on the cam/follower.