Search

A leg prosthesis test robot with hydraulic knee actuator is modeled and tested with closed loop control simulation. A cascade control architecture is designed for the system, the outer loop is controlled by a robust passivity-based controller (RPBC) and the inner loop is controlled by an optimization method. The control algorithm provides knee angle tracking with an RMS error of 0.07 degrees. The research contributes to the field of prosthetics by showing that it is possible to find effective closed loop control algorithm for a newly proposed hydraulic knee prosthesis. The simulations demonstrate the efficiency of RPBC's ability to control complex, nonlinear and multivariable system with plant variability and parameter uncertainty. Dynamic equations for the hydraulic knee actuator are derived from bond graph, an optimization method is used to solve the inversion problem. Low-pass filters are implemented to eliminate signal chatter. Necessary modifications of knee actuator parameters are discussed and recommended to achieve better tracking performance.

This dissertation presents work on the flame propagation and extinction of various liquid hydrocarbon fuels, including conventional and alternative jet fuels, surrogate fuels, and their reference hydrocarbon components. The laminar flame speeds and extinction stretch rates are experimentally determined by using a twin-flame counterflow setup integrated with a Digital Particle Image Velocimetry system for the flow field measurement. The experimental results are also compared with computed values obtained by using various published kinetic models for different fuels. In general, most of the simulation results agree with the experimental data with an average deviation less than 10%, which are reasonable considering the uncertainties in both experiments and kinetic models.The results of this work show that the conventional Jet-A and alternative jet fuels share very similar flame speeds and extinction limits despite of their differences in the molecular composition. The results of two surrogate mixtures for Jet-A show that they are both able to reproduce very well the flame speeds and extinction limits of the target jet fuel. Additional studies on aromatic species relevant to the conventional jet fuels illustrate that the degree and position of alkyl substitution on the benzene ring have a strong effect on the reactivity of the aromatic components studied. By extending the flame propagation studies to elevated pressures up to 3 atm, it is found that the flame speed results at elevated pressures are consistent in the trend with atmospheric results. Further attempts are made to identify and quantify the effects of preheat temperature and pressure on burning rate.This dissertation provides experimental flame speed and extinction data of high fidelity for jet fuels and relevant hydrocarbons. The fundamental data provided herein can serve as the benchmark database, and can be used in development and validation of combustion kinetic models.