Open loop aspects of two-wheeled vehicle stability characteristics
Mears, Barry Craig
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Permalink
https://hdl.handle.net/2142/21959
Description
Title
Open loop aspects of two-wheeled vehicle stability characteristics
Author(s)
Mears, Barry Craig
Issue Date
1989
Doctoral Committee Chair(s)
Klein, Richard E.
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
Bicycles and motorcycles constitute one of the most popular means of transportation in the world. While the literature regarding two wheeled vehicle behavior is extensive, to this day, no consensus exits in the literature as to what principles govern the steering and stability characteristics of two wheeled vehicles. This is due in part to the complex nature of the dynamic equations of motion required to model two wheeled vehicle behavior. Kinematic coupling and non-holonomic constraints make it difficult to address the two wheeled vehicle stability problem on an analytical basis. Development of tools that facilitate the analytical study of complex dynamic systems and their application to a motorcycle model are the goals of this research.
This study beings by scanning the literature and selecting appropriate equations of motion which model the open loop stability characteristics of a two wheeled vehicle. A software tool is developed based on Cramer's Rule that can determine input/output transfers functions for complex dynamic models. This tool works with ease when kinematic coupling and linear non-holonomic equality constraints are present in the model, as is the case for the selected motorcycle dynamics model. The software tool is applied to the motorcycle model and it is discovered that the motorcycle is counter intuitive due to its counter steering behavior. A nominally unstable vehicle is found to become stable for some ranges of velocity. The nominally unstable vehicle is stabilized using a simple proportional feedback control law. It is observed that gyroscopic angular momentum for the rear frame improves stability and that front wheel gyroscopic momentum improves stability at low speeds. It is also found that front wheel gyroscopic momentum has a deleterious effect on stability at high speeds. Finally, it is verified that increasing front fork head angle improves vehicle stability.
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