Axiomatic design of a customizable pneumatic automotive suspension with hydraulic ride height regulator

• Main Author: Wong, Amy L. (Amy Lai)
• Other Authors: Nam P. Suh.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2006
• Subjects: Mechanical Engineering.
• Online Access: http://hdl.handle.net/1721.1/32970

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2005. === "May 2005." === Includes bibliographical references (leaf 15). === Stiffness has long since governed the way people choose automobiles. Stiffer suspensions allow for the better handling necessary in sporty cars while softer suspensions provide the comfort expected in luxury cars. Automobiles have also been limited by ride height: a higher ride height will yield more clearance from bumps along the ground. However, lower ride height lowers the center of gravity of the car, which is desired for safety. The purpose of this work is to propose a way of using axiomatic design to device a system that uses orifice controlled dampers, pneumatic springs and hydraulic chambers to achieve a fully customizable suspension system and ride height regulation. In addition, a way to create the best possible user experience is proposed by using control theory to keep the car chassis at the same level at all times, thus giving the user the ability to have a smooth ride at any suspension setting, even stiff suspension systems in the case of sporty car settings. To achieve the goals of this work, a short-long arm (SLA) suspension system was modeled and modified. The SLA suspension system is the most common front wheel independent suspension system that is used today. === (cont.) By keeping a similar overall design for the proposed system, adaptability of the proposed system is increased. The coil spring of the common SLA suspension system is replaced by an air spring with a fluid chamber in series. The air spring has a variable spring stiffness that is related to the volume of air inside. Because air is compressible, the volume changes with the force applied, yielding a nonlinear relationship that must be compensated for by an active control system that monitors the overall volume of the air spring and compensates for any changes during use by addition or removal of air. The fluid chamber is responsible for keeping the chassis at the same level at all times by taking into account the changing volume of the air spring and the changes in the road by having incompressible fluid pumped in and out of the chamber. === by Amy L. Wong. === S.B.