Investigation of active suspension system in a multi-body quarter car model

Shastry, Himadri Kumar (2013) Investigation of active suspension system in a multi-body quarter car model. Masters thesis, Memorial University of Newfoundland.

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Abstract

Technological advancements in the automotive industry have led to various improvements in vehicle safety, ride quality and aesthetics. Vehicle safety is one of the foremost issues that the automotive industry is constantly working on to reduce the risk of injury and discomfort to passengers. Humans are sensitive to vibrations and excessive vibrations can cause injury or discomfort such as back pain, fatigue, mental stress and unseating of passengers. Road holding and vehicle stability is affected by road disturbances, suspension characteristics and directional motion of the vehicle. Ride quality is also influenced by vibrations induced from the road as well as imbalances in the tire/wheel assembly. In order to analyze and suppress vehicle vibrations and increase vehicle safety, a non-linear multi-body quarter car model and a linear quarter car model have been developed using bond graph methodology. -- Active suspension system has been developed in this research using a linear quadratic controller and applied to the linear quarter car and the multi-body model. The multi-body model has been characterized to obtain the parameters for suspension and damping coefficients that can be used in the linear quarter car model. Non-linearity has been introduced in the multi-body model with the use of non-linear components (springs and dampers) and/or use of geometric non-linearity of the suspension. A gain factor is applied to the actuator force of the active suspension system of the multi-body model to compensate for the kinematic differences between the linear model and the non-linear model. A comparison study is performed in frequency and time domain for both the models and four cases have been developed to study the effectiveness of the linear quadratic controller on the multi-body model as well as the linear quarter car model. The results show that the multi-body model performs better than the linear quarter car model when there is low geometric non-linearity. When component non-linearity and high geometric non-linearity are introduced in the multi-body model, the performance of the linear quadratic controller deteriorates in comparison to the linear quarter car, particularly for the ride quality scenarios. The active suspension system for the multi-body model performs better than the passive system in all the four cases. -- The research winds up with a discussion on how the objectives outlined in the study have been attained and recommendations for future work.

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