Simulação e otimização de uma suspensão veicular considerando segurança e conforto do usuário em um perfil de estrada irregular

• Autor(a) principal: Basilio, Julio Cesar de Castro
• Data de Publicação: 2019
• Outros Autores: [e-mail]
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/17143
• topic: Mechanical engineering; Strength of materials; Cars - Springs and suspension; Human comfort; Traffic Safety; MATLAB (Computer program); Genetic algorithms; Engenharia mecânica; Resistência de materiais; Automóveis - Molas e suspensão; Conforto humano; Segurança no trânsito; MATLAB (Programa de computador); Algorítmos genéticos; ENGENHARIAS::ENGENHARIA MECANICA::MECANICA DOS SOLIDOS

Passive vehicle suspension should reconcile parameters that result in comfort and safety for vehicle users, however, as presented in this study, these characteristics may be conflicting. According to ISO 2631, the comfort criterion is related to the human perception of vibration resulting from oscillations in the vehicle, with sprung mass acceleration being the measure of comfort. Scientific literature indicates that road irregularities may hinder the driver’s ability to control the vehicle, as greater oscillations decrease the contact force between the tire and the track, and consequently, reduce vehicle handling and ride safety. To better understand the behavior of a suspension system, simulations were performed in software Matlab®, through mathematical development of a quarter car model, with two degrees of freedom (DOF). As input to the system, a mathematical model representing classes of road profiles was implemented, aiming to approximate the analysis of real situations. The stiffness and damping of the suspension were analyzed using two parameters of the system known as: undamped natural frequency and damping ratio. Defined masses (sprung and unsprung) and tire stiffness, Matlab® simulations confirmed the conflict between comfort and safety criteria, highlighting the need to use optimization methods to find the ideal values of the suspension parameters. Since the goals of suspension optimization are to minimize vertical acceleration of the sprung mass to improve comfort, while minimizing dynamic wheel force and suspension deflection to improve safety, this is a multiobjective optimization problem. Thus, the method used was the genetic algorithm (GA), more specifically the NSGA-II algorithm, being widely used in other studies and be available between Matlab® optimization tools. The results of optimizations, especially when focused on comfort and safety, point to the natural frequency values equal to 1 Hz and damping ratio equal to 0,2. This represents suspension stiffness and damping values close to 10000 N/m and 650 Ns/m, respectively. In addition, the results show the influence of road quality, the travel speed and the sprung mass variation on the criteria of comfort and safety.