Engineering topics

Levine, William S.

Publications and source records attributed to Levine, William S..

9 records

NASA NTRS2001

Insensitivity of Control System Performance to Controller and System Parameters

An experimental and theoretical study of the CONDUIT sensitivity tools was conducted. The literature on sensitivity in nonlinear programming was reviewed to see in what ways it could be applied to CONDUIT. One result of this was the conclusion that the current insensitivity measure in CONDUIT is the right one. The question of scaling of the specifications in CONDUIT was also studied. Many simple examples were created, analyzed and, in most cases, solved. However, no general solution to the scaling problem was found. Instead, the appropriate scaling needs to be determined by review of a reasonable number of real aircraft design problems.

Levine, William S.↗

NASA NTRS1999

CONDUIT: Control Designer's Unified Interface

CONDUIT, which stands for control designer's unified interface, is a computer software package. Its purpose is to assist a human control system designer in designing control systems for aircraft. At the present time CONDUIT is being used by most of the major U. S. rotorcraft and fixed-wing aircraft manufacturers to assist in the design of stability and control augmentation systems. Work is also continuing on the development of additional features for CONDUIT, including tools for analyzing the sensitivity of solutions, and on further enhancements to the basic package. The purpose of this paper is to describe CONDUIT, its operation, and the sensitivity tools that are being developed for inclusion in the next release of the package.

Levine, William S.↗

NASA NTRS1999

Further Development, Support and Enhancement of CONDUIT

From the first airplanes steered by handles, wheels, and pedals to today's advanced aircraft, there has been a century of revolutionary inventions, all of them contributing to flight quality. The stability and controllability of aircraft as they appear to a pilot are called flying or handling qualities. Many years after the first airplanes flew, flying qualities were identified and ranked from desirable to unsatisfactory. Later on engineers developed design methods to satisfy these practical criteria. CONDUIT, which stands for Control Designer's Unified Interface, is a modern software package that provides a methodology for optimization of flight control systems in order to improve the flying qualities. CONDUIT is dependent on an the optimization engine called CONSOL-OPTCAD (C-O). C-O performs multicriterion parametric optimization. C-O was successfully tested on a variety of control problems. The optimization-based computational system, C-O, requires a particular control system description as a MATLAB file and possesses the ability to modify the vector of design parameters in an attempt to satisfy performance objectives and constraints specified by the designer, in a C-type file. After the first optimization attempts on the UH-60A control system, an early interface system, named GIFCORCODE (Graphical Interface for CONSOL-OPTCAD for Rotorcraft Controller Design) was created.

Veronica, Moldoveanu↗

NASA NTRS1998

Further Development, Support, and Enhancement of CONDUIT

A great deal of progress was made in the past year, Most importantly, the CONDUIT software package was developed to the point where it could be released to several aircraft companies for use in the design of control systems. During the week of February 23 to February 27, 1998, we collaborated with personnel from Moffett Field and California Polytechnic Institute in teaching a short course to 18 representatives of industry and the U. S. Government on the use of CONDUIT. This was a major milestone in the development of CONDUIT. At present, CONDUIT is being used by a number of companies in the design of several aircraft control systems. Most of our effort during the past year was devoted to research on items for inclusion in the CONDUIT diagnostics menu, work on good illustrative examples of the operation of CONDUIT, and on assisting in publicizing CONDUIT to industry and the government. Substantial progress was made in all of-these areas. The original goals for this contract are presented in the following section of this report. The modifications to these goals and the reasons for them are also described. This is followed by a section containing the results of work on this contract. A final section contains suggestions for future work on this project.

Levine, William S.↗

NASA NTRS1997

Transfer of the CONSOL-OPTCAD Rotorcraft Design Tool to Industry

Significant progress was made. Initial results on the improvement of the user-friendliness and useability of GIFCORCODE led to the decision to provide GIFCORCODE with a menu-driven user interface. In collaboration with staff at Moffett field and students from Cal Poly this objective has been largely met. GIFCORCODE is now menu-driven and very much easier to use. Complete designs for stability and control augmentation systems for the UH-60A ADOCS/RASCAL rotorcraft in both hover and 80 knots forward flight have been completed and documented. The originally planned presentations to industry were deferred so the new user interface for GIFCORCODE could be completed. The industry presentations are now planned for the next year. Similarly, the work on preparing a short course on the use of GIFCORCODE was deferred. The details of the original goals for this contract are presented in this report. The modifications to these goals and the reasons for them are also described. This is followed by a section containing the results of work on this contract. A final section, conclusions, contains suggestions for future work on this project.

Levine, William S.↗

NASA NTRS1997

Proposal for beta-test of GIFCORCODE

This year's effort produced very significant progress in the development of the software package heretofore known as GIFCORCODE. One important change has been in the name. The package is now named CONDUIT for CONtrol Designer's Unified InTerface. There have also been some more significant changes in the way CONDUIT is used. These changes caused some modifications in the work accomplished. Both the original goals for the year and the modifications will be described in the next section of this report. The major goal for this year was to bring CONDUIT to beta-test. This has been accomplished. The software package is in beta-test at Bell Helicopters and has been since September 1996. This and the other achievements during the past year are described in the third section of this report. Some discussion of the scaling issue is also included here. This is in answer to a question that arose at one of the CONDUIT briefings. The report concludes with a brief set of suggestions for further work. An appendix describing the issues involved in dynamic linking is also included.

Levine, William S.↗

NASA NTRS1997

CONDUIT: A New Multidisciplinary Integration Environment for Flight Control Development

A state-of-the-art computational facility for aircraft flight control design, evaluation, and integration called CONDUIT (Control Designer's Unified Interface) has been developed. This paper describes the CONDUIT tool and case study applications to complex rotary- and fixed-wing fly-by-wire flight control problems. Control system analysis and design optimization methods are presented, including definition of design specifications and system models within CONDUIT, and the multi-objective function optimization (CONSOL-OPTCAD) used to tune the selected design parameters. Design examples are based on flight test programs for which extensive data are available for validation. CONDUIT is used to analyze baseline control laws against pertinent military handling qualities and control system specifications. In both case studies, CONDUIT successfully exploits trade-offs between forward loop and feedback dynamics to significantly improve the expected handling, qualities and minimize the required actuator authority. The CONDUIT system provides a new environment for integrated control system analysis and design, and has potential for significantly reducing the time and cost of control system flight test optimization.

Tischler, Mark B.↗

NASA NTRS1994

Techniques for designing rotorcraft control systems

Over the last two and a half years we have been demonstrating a new methodology for the design of rotorcraft flight control systems (FCS) to meet handling qualities requirements. This method is based on multicriterion optimization as implemented in the optimization package CONSOL-OPTCAD (C-O). This package has been developed at the Institute for Systems Research (ISR) at the University of Maryland at College Park. This design methodology has been applied to the design of a FCS for the UH-60A helicopter in hover having the ADOCS control structure. The controller parameters have been optimized to meet the ADS-33C specifications. Furthermore, using this approach, an optimal (minimum control energy) controller has been obtained and trade-off studies have been performed.

Yudilevitch, Gil↗

NASA NTRS1993

Techniques for designing rotorcraft control systems

This report summarizes the work that was done on the project from 1 Apr. 1992 to 31 Mar. 1993. The main goal of this research is to develop a practical tool for rotorcraft control system design based on interactive optimization tools (CONSOL-OPTCAD) and classical rotorcraft design considerations (ADOCS). This approach enables the designer to combine engineering intuition and experience with parametric optimization. The combination should make it possible to produce a better design faster than would be possible using either pure optimization or pure intuition and experience. We emphasize that the goal of this project is not to develop an algorithm. It is to develop a tool. We want to keep the human designer in the design process to take advantage of his or her experience and creativity. The role of the computer is to perform the calculation necessary to improve and to display the performance of the nominal design. Briefly, during the first year we have connected CONSOL-OPTCAD, an existing software package for optimizing parameters with respect to multiple performance criteria, to a simplified nonlinear simulation of the UH-60 rotorcraft. We have also created mathematical approximations to the Mil-specs for rotorcraft handling qualities and input them into CONSOL-OPTCAD. Finally, we have developed the additional software necessary to use CONSOL-OPTCAD for the design of rotorcraft controllers.

Levine, William S.↗