Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 172-178).

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A general approach to numerically simulating wear in rollingand sliding contacts is presented in this thesis. A simulationscheme is developed that calculates the wear at a detailedlevel. The removal of material follows Archard’s wear law,which states that the reduction of volume is linearlyproportional to the sliding distance, the normal load and thewear coefficient. The target application is the wheel-railcontact. Careful attention is paid to stress properties in the normaldirection of the contact. A Winkler method is used to calculatethe normal pressure. The model is calibrated either withresults from Finite Element simulations (which can include aplastic material model) or a linear-elastic contact model. Thetangential tractions and the sliding distances are calculatedusing a method that incorporates the effect of rigid bodymotion and tangential deformations in the contact zone.Kalker’s Fastsim code is used to validate the tangentialcalculation method. Results of three different sorts ofexperiments (full-scale, pin-on-disc and disc-on-disc) wereused to establish the wear and friction coefficients underdifferent operating conditions. The experimental results show that the sliding velocity andcontact pressure in the contact situation strongly influencethe wear coefficient. For the disc-on-disc simulation, therewas good agreement between experimental results and thesimulation in terms of wear and rolling friction underdifferent operating conditions. Good agreement was alsoobtained in regard to form change of the rollers. In thefull-scale simulations, a two-point contact was analysed wherethe differences between the contacts on rail-head to wheeltread and rail edge to wheel flange can be attributed primarilyto the relative velocity differences in regard to bothmagnitude and direction. Good qualitative agreement was foundbetween the simulated wear rate and the full-scale test resultsat different contact conditions. <b>Keywords:</b>railway rail, disc-on-disc, pin-on-disc,Archard, wear simulation, Winkler, rolling, sliding

A novel design methodology of a decentralized adaptive sliding mode control scheme for a class of large-scale systems with mismatched disturbances and uncertainties in each subsystem and interconnections is proposed in this thesis. The main idea of this new method is that the design of the switching surface of each subsystem is through the design of a pseudo-feedback controller which can stabilize the dynamics when system is in the sliding mode. The feedback gain of the pseudo controller then becomes a important parameter of switching surface. The proposed controllers of each subsystem contain three parts. The first part is measurable feedback signals, and the second part is an adaptive control mechanism, which is used for overcoming the disturbances and uncertainties of each subsystem and interconnections among subsystems. The information of upper bound of those disturbances and uncertainties are not required. The third part of the decentralized controllers is used for adjusting the convergent rate of state variables of the controlled system. The asymptotical stability is guaranteed for each subsystem even if the mismatched perturbations exist when employing the proposed control scheme. An example is demonstrated for showing the feasibility of the proposed methodology.

A methodology of designing a novel sliding surface for a class of large-scale systems with matched and mismatched perturbations is proposed in this thesis. The main idea is that some adaptive mechanisms are embedded both in the sliding surface function and in the controllers, so that not only the mismatched perturbations are suppressed during the sliding mode, but also the information of upper bound of perturbation is not required except the upper bound of perturbation from input channel. The proposed controller of each subsystem contains two parts. The first part is measurable feedback signals, and the second part is an adaptive control mechanism, which is used for overcoming the perturbation of each subsystem as well as interconnections among subsystems. The dynamics of the controlled system can be driven into the sliding surface in a finite time, and the property of asymptotical stability of each subsystem is guaranteed. Two numerical examples are given to demonstrate the feasibility of the proposed methodology.

Based on the Lyapunov stability theorem, a methodology of designing an adaptive sliding mode control (ASMC) scheme is proposed in this thesis for a class of linear dynamic systems with matched and mismatched perturbations. Firstly, by utilizing a pseudo control input in the design of a novel sliding surface function, one can not only suppress the mismatched perturbations in the sliding mode, but also achieve the objective of output tracking. In addition, the accuracy of output tracking can be adjusted through the designed parameter embedded in this pseudo controller. Then, a sliding mode controller is derived to guarantee the existence of the sliding mode in a finite time by using adaptive mechanism, which is used to overcome the lumped perturbations so that the upper bound of perturbations is not required. Finally, two illustrative examples are given to demonstrate the validity of the results.

In this paper, the slipping friction is considered in the problem of a progressive wave of real fluids propagating over a permeable bottom. In the interface of soil and fluid, the ¡§no-slip¡¨ condition is relaxed and a sliding friction coefficient is introduced. Thus, the slipping effect and the permeability of bottom on the velocity near the seabed can be studied. The results indicate that the joint effect of slipping friction and permeability is crucial. The overshooting phenomena also can be explained by this joint effect.

Based on the Lyapunov stability theorem, a methodology of designing a decentralized multi-surface adaptive sliding mode control scheme is proposed in this thesis for a class of large-scale nonlinear systems with mismatched perturbations and interconnections. By utilizing the sliding mode control technique, the designed decentralized robust controller with adaptive mechanisms embedded enable the output of each subsystem to track its own desired output signal, and stabilize the whole large-scale system as well as each subsystem at the same time. In addition, the accuracy of output tracking can be adjusted through the designed parameter embedded in the controller. The purpose of the adaptive mechanisms included in the controller is to adapt the unknown upper bounds of perturbations and interconnections. Finally, two illustrative examples are given to demonstrate the feasibility of the proposed methodology.

Abstract A simple design methodology of robust adaptive sliding m de utput tracking controllers for a class of MIMO nonlinear mismatched perturbed systems is presented in this thesis.First,the derivatives of tracking error

A sliding mode controller is proposed for controlling molten steel level in a mold of continuous casting machine in this thesis. The comparisons of dynamic response, control accuracy, and reaction to perturbation between proposed controller and PID controller currently used are also presented. A perturbation estimator is embedded in the sliding mode controller in order to enhance the robustness against model uncertainty, parameter variation, and external disturbance. The perturbation considered in this thesis includes variation of casting speed, variation of area of slide gate, time delay, variation of mold area, and Dead-Band etc.. In addition, the effects of adjusting the design parameter of the proposed controller on system¡¦s dynamics are also considered.