Sensitivity Analysis in Passive Vibration Control

The achievable dynamic performance in high-precision systems by applying light and stiff design principles is reaching its limits. To further increase performance, better insight is needed in the cause and effect of the systems modeshapes and forced vibrations. In this way, transfer functions between actuator/excitation sources and sensor locations/point of interest can be optimized specifically, instead of just pushing for the highest first resonance frequency on system level. The purpose of this study is to enhance the understanding of the dynamic behavior of a structure and to provide methods for improving the dynamic response by applying sensitivity analysis. This is realized by first investigating the existing methods to derive the sensitivity values of structural response functions that characterize the dynamic behavior. With this knowledge on computational methods, the investigation proceeds with a focus on design variables. It is shown that the element-wise design variables can be assembled into a vector. This vector then describes a global design change. By doing so, the number of design variables is effectively decreased without loosing the ability to reach an optimal solution. Reducing both the design space and the solution space has led to the development of an estimation procedure for 1D structures. With this method the required structural change that leads to an intended modeshape modification can be estimated. In three case studies sensitivity analysis was employed in the evaluation of a conceptual design of a mechatronic system. The application of sensitivity analysis in the first case study resulted in a significant improvement for the rejection of floor vibrations. However, it was also shown that such an improvement could not be obtained for a coordinate direction in which a controller is present. In the second and third case study, a method for connecting two components was developed. The method uses the nodal points of one component as connection locations. Combining both the static and dynamic nodal points led to a minimization of the energy transfer between the two. The development of a demonstrator must validate the concept. By studying the sensitivity of the nodal points two tuning parameters were identified, namely force distributions and addition of lumped masses. They created the possibility to show the effect of the optimization that uses the nodal points. Furthermore, the method of tuning for optimal dynamic response could be the next step in mastering dynamic behavior.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin

Bicycle Design: A different approach to improving on the world human powered speed records

The current International Human Powered Vehicle Association world records for faired bicycles stand at 133.284km/h for the 200m flying start speed record and 91.562 km for the hour record. Traditionally the recumbent bicycles that have been developed for breaking one of either of these records have been optimized around a specific, relatively small rider, enabling the overall size to be kept small. Creating the smallest frontal area possible and optimal aerodynamic shape were then the design goals. This paper discusses the development of the Velox recumbent bicycle, which has been designed using another approach. The power required to break either of the records depends mostly on air resistance. Therefore small riders have the advantage of allowing for smaller frontal areas, whilst larger riders are able to provide more power. Performance optimization, lead to a design based around an average 1.95m tall male rider for Velox. The aerodynamic shape of Velox was then developed around the above criterion and designed with CFD and validated with wind tunnel and road tests. Essential for the rider’s performance is that the rider feels comfortable whilst riding the bicycle. Therefore the uncontrolled lateral dynamics and the required rider steer control input were investigated. The bicycle’s geometry was optimized for low speed stability and the required control input.Mechanical, Maritime and Materials Engineerin