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Nonlinear dynamic model and simulation of a high pressure monotube shock absorber using the bond graph method

IP.com Disclosure Number: IPCOM000128085D
Original Publication Date: 1997-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 6 page(s) / 21K

Publishing Venue

Software Patent Institute

Related People

Mollica, Rosario: AUTHOR [+3]

Related Documents

http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1997-351: URL

Abstract

A physics-based model for a high pressure monotube shock absorber is proposed by which the nonlinear dynamic behavior of these dampers can be analyzed. The bond graph technique is used to model these shock absorbers accurately over a wide range of stroking frequencies and to identify the interaction between mechanical, fluid, and thermodynamic elements. Various phenomena are modelled such as fluid inertia effects, laminar orifice flow, air entrained in the hydraulic fluid, and cavitation. Simulation results demonstrate good model accuracy when compared to test data for similar hydraulic dampers. Parametric studies involving various elements of the system including gas pressurization, the amount of entrained air, and stiction are conducted in order to demonstrate the affects of these parameters on system performance. Results indicate the fundamental characteristics of shock absorbers are produced by the interaction of resistive and capacitive elements inherent in these systems, Capacitive elements combine with resistive elements resulting in hysteresis in the force-velocity characteristic and less energy dissipation at higher frequencies for constant maximum stroking velocities, The effects of fluid inertia and laminar flow are found to be negligible for the range of frequencies investigated (1 to 20Hz) in the monotube design of this study. Modifications to the model are proposed to reduce the state order for use in automotive suspension system models. Thesis Supervisor: Dr. Kamal Youcef Toumi Title: Associate Professor of Mechanical Engineering [4]

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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/1997-351 for copyright details and for the full document in image form.

Nonlinear Dynamic Model and Simulation of a High Pressure Monotube Shock Absorber Using the Bond Graph Method

by

Rosario Mollica
M.S., Engineering University of Michigan, 1986 B.S., Mechanical Engineering Worcester Polytechnic Institute, 1985
Submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering

at the Massachusetts Institute of Technology

February 1997
(c) 1997 Rosario Mollica. All rights reserved.

The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies of this thesis document in whole or in part.

SIGNATURE OF author: [[signature omitted]]

Department of Mechanical Engineering

February 5, 1997

CERTIFIED BY: [[SIGNATURE OMITTED]]

Dr. Kamal Youcef-Toumi

Associate Professor Thesis Supervisor

ACCEPTED BY: [[SIGNATURE OMITTED]]

Dr. Ain A. Sonin Chairman, Department Committee on Graduate Students ARCHIVES MASSACHUSETTS INSTITUTE OF TECHNOLOGY LIBRARIES OCT 27 1999

Massachusetts Institute of Technology Page 1 Dec 31, 1997

Page 2 of 6

Nonlinear dynamic model and simulation of a high pressure monotube shock absorber using the bond graph method

Nonlinear Dynamic Model and Simulation of a High Pressure Monotube Shock Absorber Using the Bond Graph Method

by

Rosario Mollica

Submitted to the Department of Mechanical Engineering on January 17,1997 in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering

Abstract

A physics-based model for a high pressure monotube shock absorber is proposed by which the nonlinear dynamic behavior of these dampers can be analyzed. The bond graph technique is used to model these shock absorbers accurately over a wide range of stroking frequencies and to identify the interaction between mechanical, fluid, and thermodynamic elements. Various phenomena are modelled such as fluid inertia effects, laminar orifice flow, air entrained in the hydraulic fluid, and cavitation.

Simulation results demonstrate good model accuracy when compared to test data for similar hydraulic dampers. Parametric studies involving various elements of the system including gas pressurization, the amount of entrained air, and stiction are conducted in order to demonstrate the affects of these parameters on system performance. Results indicate the fundamental characteristics of shock absorbers are produced by the interaction of resistive and capacitive elements inherent in these systems,

Capacitive elements combine with resistive elements resulting in hysteresis in the force-velocity characteristic and less energy dissipation at higher frequencies for constant maximum stroking velocities, The effects of fluid inertia and laminar fl...