Passive and semi-active torsional vibration control

This dissertation presents the results of research in the area of torsional-vibration control with the application of modern computational power as well as "smart" or adaptive materials. The research starts as an investigation into the potential for developing new crankshaft damper designs for use in internal combustion engines (ICE). An ICE time-domain simulation model is developed from the perspective of determining crankshaft vibrations. A genetic algorithm (GA) is then used to design an optimal crankshaft damper.; Tile second study in the research involves an investigation into the use of a magneto-rheological (MR) fluid brake as a semi-active crankshaft damper. Basic characteristics tests of the MR brake and its implementation as a variable friction damper on a single degree of torsional system are performed. Optimum friction levels are predicted based on established tuning rules. The error between the predicted and experimental optimal torques is significant enough to warrant further investigation into the exact optimal friction torque of a friction damper for a given primary system.; To that end, as the third study in this research, a new approach for the analysis of friction dampers is developed. The exact form of the steady state solution for a friction damper implemented on a primary system is derived and numerical solutions are used to determine the optimum friction in a friction damper applied to a specific primary system. When compared to classical results presented by earlier authors, the new approach provides a better solution.; The fourth study of this dissertation presents an alternative approach to the implementation of an MR brake for torsional vibration control. Experimerntal testing for an MR fluid brake is first performed to characterize the device. A linear model for the dynamic torque response of the brake is constructed. A feedback control system is then developed and implemented, which significantly improves the bandwidth of the brake's torque response. A test stand is designed to mimic applications that might be found in industrial settings. The MR brake is then used to control vibrations and to reduce the torque oscillations seen by the rotating primary system of the test stand.