Michael J. Rabins

Controller Synthesis for Maximizing Disturbance Bounds in Linear Uncertain Systems

Abstract A recently developed design methodology [1]-[4] for maximizing the disturbance bound for SISO systems with no uncertainty is extended to SISO systems with structured uncertainty. In particular, we consider systems of the form Y s = G u s , α U s + G w s , α W s where U(s) is the control input, W(s) is the disturbance, Y(s) is the output and a is a vector characterizing the bounded uncertain parameters. The objective is to synthesize a controller Gc(s) to (i) maximize the disturbance bound (ii) simultaneously satisfy hard magnitude constraints on the control, output and intermediate states and (iii) satisfy bandwidth constraints. The methodology proposed is based on pointwise design in the frequency domain. The plant uncertainty is characterized by templates that depend on the frequency. Since the magnitude and phase vary with both frequency and the uncertain parameters, a Nichols chart is utilized to represent the plant templates. These templates are generated by bounding the uncertain plant by the so-called Kharitonov polynomials. Controller synthesis is accomplished by loop shaping so that the nominal loop transfer function stays within the acceptable boundaries in the Nichols chart corresponding to each frequency. In order to generate the allowable design regions, the state/control constraints and bandwidth limitations are incorporated into a set of target transfer functions. These target transfer functions are chosen on the basis of a unit step distrubance. Selecting the targets is particularly easy if only disturbance rejection is considered. The entire design process utilizes classical control theory and has much in common with QFT [5]. The design procedure is illustrated by an example.

Two methods for ethics case analysis

Engineering instructors are often reticent about introducing ethics cases into their engineering courses. One way to overcome this reticence is to provide one or more simple methodologies that have been found effective both in stimulating class discussion and in providing ways of resolving ethical problems. The authors present two such methodologies. One is a methodology for resolving what the authors call conflict problems. The other is a methodology for resolving what they call line-drawing problems. Most practical ethical problems can be classified as either conflict problems or line-drawing problems, but one approach is usually more useful for resolving a given moral problem than the other.<<ETX>>

Mode Localization by State Feedback Control Quasi-Perturbation of a Multi-Degree-Of-Freedom System

Abstract This paper describes the research done at Texas A&M University into the application of mode localization as a means of vibration control. The paper begins with a discussion of past research efforts, including the design and constniction of a periodic system test rig. Next is a discussion of current efforts to produce mode localization through fictitious perturbations, where active feedback torque control mimics real, mode-localizing perturbations in the system. Finally, the paper explains how this research has proven beneficial to undergraduate mechanical systems and controls coursework at Texas A&M.

Teaching Multi-Degree-of-Freedom Dynamics: A Laboratory Demonstration Tool

Abstract The development of the design and fabrication for a five degree of freedom rig of symmetrically coupled pendula for demonstrating eigenvalues, eigenvectors and dynamic system analysis theory is described. Although originally designed for testing and corroborating mode localization theory, the serendipitous capability of the system to be used as a teaching device in vibration or dynamic system analysis classes using TV tapes of the five separately excited natural modes was recognized early during the project, and is demonstrated in this paper. Instrumentation and data-analysis techniques are discussed.

Advances in Automatic Controls Educations

Abstract A summary report on two sessions of papers presented at the recent American Control Conference in Atlanta, Georgia on June 15-17, 1988. The presentations focused on new laboratory experiments, new classroom demonstrations, new P.C. software packages, new problem/project solutions that can be replicated, and relevant video-tape segments. This report will summarize and evaluate all of those presentations and will include detailed descriptions of all of the table-top exhibits associated with the presentations.