Institute for Systems Research
Permanent URI for this communityhttp://hdl.handle.net/1903/4375
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Item Enumeration and Selection of Clutching Sequences Associated with Epicyclic-type Transmission Mechanisms(1997) Hsieh, Hsin-I; Tsai, L. W.; ISRThis dissertation investigates the kinematics, the torque distributions, and the power losses of epicyclic gear mechanisms based upon the concepts of fundamental geared entities and fundamental circuits. The kinematic characteristics of fundamental geared entity are applied to the overall speed ratio analysis of epicyclic gear mechanisms. It is shown that the overall speed ratio of an epicyclic gear mechanism can be symbolically expressed in terms of the speed ratios of its fundamental geared entities by decomposing an epicyclic gear mechanism into two subsystems and each subsystem into two subsystems until the lowest level subsystem contains only one fundamental geared entity. The results are then used for the estimation and comparison of various speed ratios of an epicyclic gear mechanism, which leads to the development of a methodology for the enumeration of feasible clutching sequences for a given epicyclic gear mechanism. Finally, a systematic methodology for the torque and power loss analyses is described and a procedure for selecting a most efficient clutching sequence of an epicyclic gear mechanism is presented.Item Mixed H2 /H∞ Optimization: A BMI Solution(1996) Yen, S.D.; ISRThe mixed H2 /H∞ problem arises as one means to achieve robust good performance for a controlled linear time-invariant system. The idea is to achieve H2 optimal performance subject to an H∞ bound as robustness. It has been difficult to find good algorithms for solving this problem. In this study the problem was transformed into a bilinear matrix inequality problem (BMI). Solving the BMI by the method of centers was shown to be complicated by discontinuities resulting from the unobservability of the closed-loop system. Transforming the BMI problem into a lattice of BMI subproblems makes it possible to avoid the discontinuity and solve the original problem. A robust flight control system for the F-14 is included as an example of the algorithm.Item Systematic Design of Gearless Differentials and Analysis of a Potential Mechanism(1996) Madhavan, Bharath; Tsai, L.W.; ISRThe method of classification of mechanisms according to kinematic structure and function is used to systematically enumerate gearless differential mechanisms. The method adopted here is to first enumerate 1:-1 constant-velocity shaft couplings which are later transformed into gearless differential. Preliminary screening of the enumerated mechanisms resulted in four potential 1:-1 constant-velocity shaft couplings that are free from singular conditions. With a little modification, these mechanisms are then converted to gearless differentials. A promising candidate mechanism is chosen and kinematic and dynamic analyses are performed. The dynamic analysis is done using the software package DADS. It is shown that the proposed mechanism does have the potential for use as a gearless differential. Finally design rules are laid out which can be used for the design of an optimal gearless differential.Item Systematic Enumeration of 1:-1 Constant-Velocity Shaft Couplings(1996) Madhavan, Bharath; Tsai, L-W.; ISRA systematic methodology is employed for the enumeration of 1:-1 constant-velocity shaft couplings. As a result, four potential 1:-1 constant-velocity shaft couplings that are free from singular conditions are enumerated. A promising mechanism is selected for the dynamic analysis. The analysis shows that the mechanism does have the potential for use as a 1:-1 constant- velocity shaft coupling and as a gearless differential.Item A Systems Engineering Approach to Design a Smart Tool Post Structure(1995) Ko, Wing F.; Zhang, G.M.; ISRPrecision machining has received more and more industry-wide attention as dimensional accuracy becomes a significant measure of quality in a product. The key in achieving today's quality requirement is, therefore, precision of a machine tool. Since the invention of the first CNC machine tool in the 1960s, machine tool research has entered an almost stagnant stage. There are numerous reasons for the slow progress, and the lack of system- wide studies of the machine tool performance is one of them.The research presented in this thesis focuses on improving machining accuracy using a systems engineering approach. A conventional lathe during machining is taken under consideration as a machining system. The tool post is identified as a critical component in the machining system to achieve the defined machining accuracy. Smart material made actuators are used to design a new tool post structure that is capable of carrying out an active vibration control during machining.
In this thesis research, the fabrication of the designed tool post is completed. Results obtained from the initial tests strongly demonstrate its capability to attenuate tool vibration during machining in an active and intelligent way. Thus, the smart tool post system fulfills the design objective of achieving microscopic level machining precision on a low-cost conventional machine tool platform. Suggestions on the actuator specifications are made for further improvement on vibration compensation.
Item Parametrically Optimal Control for the UH-60A (Black Hawk) Rotorcraft in Forward Flight(1995) Potter, P.J.; Levine, W.S.; ISRNew techniques for the design of rotorcraft flight control systems (FCS) to meet hover flight condition handling qualities requirements (HQR) have recently been developed. These techniques are based on multicriterion optimization as implemented in the optimization package CONSOL-OPTCAD (C-O). Further development of these methodologies applicable to the design of a FCS to meet forward flight HQR is presented herein. The forward flight design methodology is applied to the design of a FCS for the Advanced Digital Optical Control System (ADOCS) UH- 60A Black Hawk helicopter in forward flight at 80 knots. The controller parameters have been optimized to meet the ADS-33C forward flight specifications. Utilizing this approach, an optimal controller based on minimum actuator control energy has been obtained and trade-off studies have been performed.Item Geometric Algorithms for Recognition of Features from Solid Models(1995) Regli, W.C., III; Nau, D.S.; ISRCollaborative engineering has expanded the scope of traditional engineering design to include the identification and elimination of problems in the manufacturing process. Manufacturing features and feature-based representations have become an integral part of research on manufacturing systems, due to their ability to model the correspondence between design information and manufacturing activities. One necessary component of an integrated Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) environment is a tool to automatically recognize manufacturing features from a CAD or solid model. In this thesis we present a methodology for recognizing a class of machining features and for addressing the computational issues involved in building tractable and scalable solutions for automated feature recognition. This approach is described for a class of volumetric features based on material removal volumes produced by operations on 3-axis vertical machining centers. A computational framework is developed for representing different types of common machining features and specifying the recognition problem. Based on this framework, novel serial and multi-processor recognition algorithms are described and analyzed with respect to their completeness and complexity. The goal of this dissertation is to advance the understanding of the basic computational issues that arise in feature recognition from solid models of mechanical artifacts and to facilitate development of effective and efficient systems that can scale to address industrial problems.Item A Systems Approach to Nonlinear Finite Element Analysis of Shell Structures(1995) Chen, Xiaoguang; Austin, Mark; ISRThis report describes a systems approach to the nonlinear finite element analysis of shell structures. The research objective is to understand the structure a small language and computational environment should take so that matrix and nonlinear finite element computations can interact in a seamless manner.One four-node-thick shell finite element and one eight-node-thick shell finite element is formulated and implemented in ALADDIN [1]. The finite elements are based on a three-dimensional continuum formulation, and are simplified by assuming a flat element geometry. Numerical experiments are presented for in- plane displacements of a flat plate, and out-of-plane bending of a cantilever structure. In each case, material nonlinearities are modeled with bi-linear and Ramberg-Osgood stress-strain curves. The report concludes with recommendations for further work in the areas of nonlinear finite element solution procedures and enhancements to ALADDIN's problem-solving infrastructure.
Item ALADDIN: A Computational Toolkit for Interactive Engineering Matrix and Finite Element Analysis(1995) Austin, Mark; Chen, Xiaoguang; Lin, Wane-Jang; ISRThis report describes Version 1.0 of ALADDIN, an interaction computational toolkit for the matrix and finite element analysis of engineering systems. The ALADDIN package is designed around a language specification that includes quantities with physical units, branching constructs and looping constructs. The basic language functionality is enhanced with external libraries of matrix and finite element functions.Item Globally Convergent Algorithms for Robust Pole Assignment by State Feedback(1995) Tits, A.L.; Yang, Y.; ISRIt is observed that an algorithm proposed in 1985 by Kautsky, Nichols and Van Dooren (KNV) amounts to maximize, at each iteration, the determinant of the candidate closed-loop eigenvector matrix X with respect to one of its columns (with unit length constraint), subject to the constraint that it remains a valid closed-loop eigenvector matrix. This interpretation is used to prove convergence of the KNV algorithm. It is then shown that a more efficient algorithm is obtained if det (X) is concurrently maximized with respect to two columns of X, and that such a scheme is easily extended to the case where the eigenvalues to be assigned include complex conjugate pairs. Variations exploiting the availability of multiple processors are suggested. Convergence properties of the proposed algorithms are established. Their superiority is demonstrated numerically.