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Adding Servo Characteristics to a Finite Element Model of a Structure

IP.com Disclosure Number: IPCOM000121109D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 4 page(s) / 137K

Publishing Venue

IBM

Related People

Hall, MW: AUTHOR [+2]

Abstract

A mathematical method that allows a servo loop to be added into the matrices of a Finite Element model of a mechanical structure.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

Adding Servo Characteristics to a Finite Element Model of a Structure

      A mathematical method that allows a servo loop to be
added into the matrices of a Finite Element model of a mechanical
structure.

      The Finite Element method for analyzing mechanical structures
is used extensively.  There are many cases where some of the elements
of a mechanical structure are connected via a servo, e.g., servo
control of a disk file or robotic arms.  This article shows a method
by which the servo characteristics can be added to the Finite Element
model. The principle is to represent the servo electronics as a
series of second order quotient polynomials in the Laplace Operator
S.

      The coefficients of the above mentioned polynomials can be
added into the Finite Element Matrices for a disk file as shown in
the next paragraph.  Nodes on the actuator and spindle are chosen to
represent the head and track and these are 'connected together' by
the servo.  The subscripts n and d represent the numerator and
denominator of the polynomial. A number of dummy nodes are created by
this method which have no real physical meaning; they are just points
within the electronics.  Fig. 1 shows this diagrammatically.

      The advantage of this scheme is that it allows a much more
realistic analysis of the servo/mechanics to be made and uses
existing and well-developed programs to analyze the result.  This
method has been tried using NASTRAN (Finite Element Analysis Prog...