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A closed-loop shape control methodology for flexible stretch forming over a reconfigurable tool

IP.com Disclosure Number: IPCOM000128108D
Original Publication Date: 1999-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 10 page(s) / 30K

Publishing Venue

Software Patent Institute

Related People

Valjavec, Marko: AUTHOR [+3]

Related Documents

http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1999-40: URL

Abstract

Today stretch forming of sheet metal parts and associated tool design methods used in the aerospace industry are still more an art than a science. Few analytical tool design techniques exist and even fewer are used in practice. When they are, they only address the result but not the cause of the forming anomalies. Rigid tooling, fixed-configuration facilities and dependence on tool designers' expertise are the major drawbacks of modern tool design. Tool fabrication result in long lead times, high manufacturing costs and insufficient product quality.

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 This record is the front matter from a document that appears on a server at MIT and is used through permission from MIT. See http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1999-40 for copyright details and for the full document in image form.

A Closed-loop Shape Control Methodology for Flexible Stretch Forming Over a Reconfigurable Tool

by

Marko Valjavec
Dipl. Eng. in Mechanical Engineering (1992) University of Ljubljana, Slovenia Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering

at the Massachusetts Institute of Technology

February 1999
SIGNATURE OF author: [[signature omitted]]

Mechanical Engineering

December 15, 1998
CERTIFIED BY: [[SIGNATURE OMITTED]]

David E. Hardt Professor of Mechanical Engineering Thesis Supervisor ACCEPTED BY: [[SIGNATURE OMITTED]]

Ain A. Sonin

Chairman, Department Committee on Graduate Studies ARCHIVES MASSACHUSETTS INSTITUTE OF TECHNOLOGY LIBRARIES

Massachusetts Institute of Technology Page 1 Dec 31, 1999

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A closed-loop shape control methodology for flexible stretch forming over a reconfigurable tool

[2]

[3]

A Closed-loop Shape Control Methodology for Flexible Stretch Forming Over a Reconfigurable Tool

by

Marko Valjavec

Submitted to the Department of Mechanical Engineering on December 15, 1998 in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Mechanical Engineering

ABSTRACT

Today stretch forming of sheet metal parts and associated tool design methods used in the aerospace industry are still more an art than a science. Few analytical tool design techniques exist and even fewer are used in practice. When they are, they only address the result but not the cause of the forming anomalies. Rigid tooling, fixed-configuration facilities and dependence on tool designers' expertise are the major drawbacks of modern tool design. Tool fabrication result in long lead times, high manufacturing costs and insufficient product quality.

In response to this, a methodology combining a self tuning shape control algorithm and reconfigurable forming tool is developed and implemented for stretch forming This methodology is based on empirical estimation of the process characteristics from the calibration forming trials, and is capable of generating a tool shape that produces, upon the impact of unloading and in- process variations, the final part shape of desired precision. The methodology is based on a new system identification strategy, where the effect of decreasing signal magnitudes on the transfer function estimate is greatly alleviated. The assumption that the change in tool shape is linearly related to the corresponding change in part shape proved to accurately capture the stretch forming characteristics. The relative stability analysis shows that the final part shape converges to the designed shape despite significant alterations of the calibration die shape and proportional controller gai...