Year

2024

Degree Name

Doctor of Philosophy

Department

School of Electrical, Computer and Telecommunications Engineering

Abstract

The escalating attention on ride comfort and safety in vehicles, driven by a surge in transportation time, underscores the critical role of vehicle suspension. This study focuses on electrically interconnected suspension (EIS), a burgeoning technology utilizing electrical components for enhanced flexibility and adaptability. The research aims to develop and validate effective EIS systems and control strategies to elevate ride comfort.

The three types of suspension systems: passive, active, and semi-active, highlight the design challenges of balancing ride comfort, road handling, and suspension deflection limitations. The limitations of these systems, particularly active suspension's drawbacks of high energy consumption and cost, prompt exploration of semi-active solutions such as EIS.

An innovative EIS system is introduced, featuring variable inertance and variable damping (VIVD) in the heave direction and variable stiffness (VS) in the roll direction. Unlike traditional systems, this EIS achieves suspension interconnection through an electrical network (EN), offering enhanced design flexibility, energy efficiency, and rapid system response. Experimental validation on a half-car test rig demonstrates superior performance compared to passive suspension, emphasising its potential to enhance ride comfort.

Further enhancing EIS performance, a disturbance compensation control strategy based on acceleration measurements is introduced. Disturbance observers, grounded in practical acceleration measurements, address challenges related to unknown disturbances, model simplification, and EN nonlinearity. Experimental results affirm the effectiveness of the proposed disturbance compensation controller, emphasising its promise for practical applications.

In addition, a closed-loop current control unit (CCU) is designed to achieve precise and continuous current control for the EIS system. Employing high-frequency metal–oxide–semiconductor field-effect transistors (MOSFETs) and a resistor, the CCU enables dynamic resistance adjustment through a Pulse Width Modulation (PWM) signal. A robust sliding mode control strategy is implemented to address nonlinearities, forming a closed-loop CCU. Experimental validation demonstrates the CCU's effectiveness in significantly enhancing vibration control performance, highlighting its potential contribution to EIS technology.

Introducing known nonlinearity into vibration control systems has been proven to enhance performance. A novel nonlinear electromagnetic damper (EMD) integrated into decoupled EIS utilising the CCU has been proposed. The damper allows for the emulation of equivalent nonlinear mechanical properties in corresponding directions. Through dynamic resistance adjustment within the EN, damping can be continuously modulated based on arbitrary nonlinear functions related to suspension deflection or deflection rate. The proposed approach offers flexibility and effectiveness in achieving nonlinear damping with minimal structural constraints compared to other nonlinear damping/stiffness structures. Simulation results demonstrate significant improvements compared to passive systems. These findings offer valuable insights for designing nonlinear damping mechanisms to enhance vibration control performance in various engineering applications.

The thesis concludes by summarizing the main contributions, including the development of a versatile semi-active EIS, decoupled control strategies, disturbance compensation methods, and an innovative closed-loop CCU. These advancements underscore the potential of EIS in revolutionizing vehicle suspension systems, particularly in achieving superior ride comfort in diverse and challenging conditions.

FoR codes (2008)

0906 ELECTRICAL AND ELECTRONIC ENGINEERING

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.