J. Mitchell

Ohio University · Department of Electrical Engineering and Computer Science

Herein a method of hybrid frequency domain and state space system identification is developed, tested and implemented. A frequency domain least squares system identification algorithm, along with a coherence function technique for eliminating noisy data is used to sequentially develop discrete single-input, multiple-output (SIMO) transfer function...

As technology's influence grows, it is critical that engineers take a greater role in public and private leadership. Most engineering students, however, are not exposed to formal studies in leadership development. For the past 12 years, the Robe Leadership Institute (RLI) has encouraged effective leadership for the college's students, faculty, and...

This report details the results of a one year effort by Ohio University to apply the transfer function modeling and analysis tools developed under NASA Grant NAG8-167 (Irwin, 1992), (Bartholomew, 1992) to attempt the generation of Space Shuttle Main Engine High Pressure Turbopump transfer functions from time domain data. In addition, new enhancemen...

The major contributions of the grant effort have been the enhancement of the Compensator Improvement Program (CIP), which resulted in the Ohio University CIP (OUCIP) package, and the development of the Model and Data-Oriented Computer Aided Design System (MADCADS). Incorporation of direct z-domain designs into CIP was tested and determined to be nu...

In numerous cases, the application of analytical techniques to control system design has been found to yield unsatisfactory results. The need for an analytical model, the small number of design specifications that can be satisfied, and the possibility of a high order resulting controller are disadvantages common to many of these techniques. An alte...

An iterative numerical algorithm for designing robust controllers using experimental data models is presented. This numerical approach has several advantages over standard analytical approaches. First, design constraints of many types can be specified. Also, the controller order is pre-specified by the designer. Finally, no analytical model of the...

An iterative numerical algorithm for designing robust controllers using experimental data models is presented. This numerical approach has several advantages over standard analytical approaches. First, design constraints of many types can be specified. Also, the controller order is pre-specified by the designer. Finally, no analytical model of the...

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A solution to the problem of obtaining a multi-input, multi-output statespace model of a system from its individual input/output frequency responses is presented. The Residue Identification Algorithm (RID) identifies the system poles from a transfer function model of the determinant of the frequency response data matrix. Next, the residue matrices...

The results of the application of modern robust control design techniques have been disappointing. This is particularly true for applications involving flexible structures due to the conservatism inherent in assuming the presence of unstructured model uncertainty. It has been observed that models for such systems derived from finite element approac...

Finite-element methods (FEMs) and extraction from experimental data are the most widely used methods for developing models of flexible structures for the analysis, design, and simulation of control systems. However, these methods produce models with modes that do not contribute significantly to the fidelity of the model. Eliminating these modes is...

The most accepted methods for developing models of flexible structures for the analysis, design and simulation of control systems are finite element methods and extraction from experimental data. Using either of these methods, models are often produced with modes that do not significantly add to the fidelity of the model. This paper presents techni...

An adaptive control scheme for suppressing vibrations of large flexible structures is presented. The control scheme utilizes self-tuning digital notch filters to minimize the excitation of the system resonant modes by control forces. The notch filters are tuned so that their center frequencies coincide with the system resonant frequencies, which ar...

The advantages of designing control systems for large space structures (LSS) using frequency-domain models extracted from empirical time data are discussed. Techniques for performing MIMO system identification from test data are presented as well as techniques for improving the performance of the system identification process in the presence of noi...

A minimum of system testing of the Space Station will take place on the ground. Hence, the dynamic characteristics of the Station will have to be determined on-orbit. This paper describes a technique for determining these characteristics and concurrently designing a digital controller. This design approach is termed “Design-to-Performance”.

A minimum of system testing of the Space Station will take place on the ground. Hence, the dynamic characteristics of the Station will have to be determined on-orbit. This paper describes a technique for determining these characteristics and concurrently designing a digital controller. This design approach is termed "Design-to-Performance".

The design of control systems for precision pointing systems which operate in a space or an airborne environment involves usually a design of three dimensional pointing systems. The present investigation is concerned with a design methodology which is applicable to a large class of gimbaled pointing systems. The considered methodology is based on d...

The theory and associated numerical techniques for the Multiple Input Multiple Output Compensator Improvement Program are presented. This algorithm is applicable to the design of the feedback compensation matrix for linear time-invariant control systems with plants possessing multiple control inputs and multiple outputs. The algorithm discussed in...

The cofactors of [sI-A] are the key to accurate, efficient calculation of [sI- A]^{-1} and partial lambda/partial a_{ij} , where a ij is an element of A . These cofactors can be evaluated by transforming their equivalents to phase variable or quasi-phase variable form. The procedure for forming the equivalent cofactors is the principal topic of thi...

An electromechanical feedback system for controlling the perfusing pressure to the lower left lobe of dog lungs was developed. It functioned by regulating the size of a balloon located within the lobar artery or vein. The system successfully controlled lobar arterial pressure in 30 dogs and venous pressure in 15 dogs. This control system could be v...

In control theory, a synonymous term for pole sensitivity is eigenvalue sensitivity. Existing methods of calculating eigenvalues are cumbersome, and cannot be trusted for systems roughly greater than tenth order. The method proposed in the present paper is applicable to high-order system. (It has been routinely used to generate eigenvalue sensitivi...

In the above paper an analytical technique for designing cascade lead compensation is presented. In this note it is shown that with modified conditions the technique is, also, applicable to the design of lag compensation.

This short paper presents a computerized algorithm for the design of compensators for large launch vehicles. The algorithm is applicable to the design of compensators for linear, time-invariant, control systems with a plant possessing a single control input and multioutputs. The achievement of frequency response specifications is cast into a strict...

The sampled frequency response of a continuous system can be represented by an infinite series which is truncated for practical application. In utilizing the truncated series, it is desirable to retain the fewest number of terms and still keep the error between the actual sampled frequency response and the approximated sampled frequency response be...

A computer-aided-compensator design technique is presented for a control system, with open loop frequency response by n discrete frequency points which result in n functions of the compensator coefficients. Several of these functions are chosen so that the system specifications are properly portrayed; then mathematical programming is used to improv...

In the past few years there has been an increasing interest in the use of the computer for designing compensators of control systems.1,2,3,4,5,6 The compensator design technique presented in [1] is basically a weighted least squares fit of the actual frequency response curve to some desired frequency response. Somewhat different, the method describ...

Compensator improvement program with application to large space vehicles and tables noting relative stability versus frequency response

This paper presents the theory and a technique for compensator improvement. Several definitions in regard to relative stability are presented along with some frequency response limitations and characteristics of a large space vehicle. A nonlinear programming algorithm for obtaining an improved solution for a strict constraint problem is developed a...

This paper presents the preliminary studies of compensator growing from a frequency response point of view. Several definitions in regard to relative stability of a control system are made. Three theorems for helping to determine the necessary size of the compensator that should be employed for a specific system are stated and proved. Following the...

A generalized root locus following technique is presented. Fundamentally, the concept involved is that of approximating a locus by a straight line in order to predict another point on the locus. The method is applicable to a large class of root loci problems and yields expressions for calculating the real and imaginary parts of the roots in terms o...

Data sampling system compensation based on bending frequency filtering through information obtained by varying sample rate, using saturn 5 launch vehicle simulation

Frequently the analysis of sampled-data control systems is most easily accomplished by the frequency response methods. A practical way of determining an approximate sampled-frequency response of a continuous data system is to truncate the infinite series version of this frequency response after a finite number of terms. The amount of error produced...

The theory and associated numerical techniques for the Multiple Input, Multiple Output Compensator Improvement Program (MIMO CIP) are presented. This algorithm is applicable to the design of the feedback compensation matrix for linear, time-invariant control systems with plants possessing multiple control inputs and multiple outputs. The design spe...

A new computer aided design algorithm for linear time-invariant control systems is presented. The technique is called the Pole Optimization Program (POP). The basic design philosophy and the theory underlying POP are discussed. The salient features and practical application are illustrated by numerical examples.

Following is the continuation of the list of titles and authors: Nonlinear Programing in Design of Control Systems with Specified Handling Qualities. By Albert A. Schy. On-Line Digital Controller for Plants with Saturating Inputs. By J. B. Plant, JJ. T. A. J. Marcotte, J. L. J. Lyrette. Digital Compensators with Transdport Delay. By B. E. Bona. Dig...

An adaptive sampling technique utilizing the first three terms of a Taylor series expansion about the n th sampling instant for the error signal in an error-sampled feedback control system is presented. The necessary rules for determining the sign convention used in applying the technique are given along with an example illustrating the method. The...