Jason Zheng Jiang

Hydraulic shock absorbers in passenger vehicles typically generate damping through valves and orifices that create a restricted fluid passage between the cylinder’s upper and lower chambers. Motivated by the proven effectiveness of inerters in various applications, this study investigates the integration of hydraulic inertance into this fluid passage to enhance absorber performance. While prior research has explored such integration, a systematic method for identifying optimal configurations of hydraulic stiffness, damping and inertance elements within the passage remains undeveloped. To address this gap, this study proposes a novel configuration‐optimisation framework for hydraulic absorbers using a predefined number of each element type. The absorber is modelled as a three‐terminal hydraulic network, and a graph‐based enumeration method is introduced to generate all feasible network layouts. Each candidate is then tuned and evaluated to determine the optimal design, which is subsequently realised using physical components considering necessary nonlinear and parasitic effects. A numerical case study involving a simplified car model demonstrates the framework’s effectiveness. The trade‐off between ride comfort and road handling ability is investigated. For a comfort‐oriented design scenario, using just one stiffness, one damping and one inertance element, the proposed method identifies a physical design that improves ride comfort by 19.4% compared with a conventional absorber with a single orifice in the fluid passage.

Hydraulic interconnected suspension (HIS) systems represent a burgeoning technology in the automotive industry, notably due to their abilities to reconcile the well-known trade-off between ride comfort and handling performance. Numerous design possibilities for HIS systems exist, considering various hydraulic components (such as orifices, accumulators, and pipelines) and their topological connections. At present there is a lack of a systematic design approach for such systems. Traditional design approaches focus on making piecemeal modifications to existing designs, neglecting a substantial catalogue of fundamentally different and transformative schemes. Consequently, significant potential performance enhancements remain untapped. To address this limitation, this paper proposes a novel systematic design approach for HIS systems, which enables a wide range of design possibilities to be explored, and an optimal configuration to be identified. The efficacy of the methodology is demonstrated via a case study. Given a predefined design complexity, a beneficial single-axle HIS system is constructed, which can achieve a 15.6% ride comfort performance improvement while maintaining roll-control performance compared with the traditional system.

Passive vibration absorbers (PVAs) play a crucial role in mitigating excessive vibrations in engineering structures. Traditional PVA design typically begins with proposing a beneficial topological layout, incorporating stiffness, damping, and inertance elements, followed by optimal sizing of each element to minimise specific response of dynamically excited structures. An alternative approach involves first designing the impedance function of a PVA and then identifying a passive mechanical layout that replicates this impedance using network synthesis techniques. However, both methods struggle to identify the most efficient PVA layout using the minimum number of elements (referred to as “complexity”) for a given vibration suppression problem. To this end, this study introduces a graph‐based methodology for designing optimal configurations (i.e., layout + sizing) of two‐terminal spring‐damper‐inerter PVAs that achieve specified performance goals with minimum complexity. In this approach, a PVA is represented as a weighted coloured multigraph, enabling the application of a novel graph‐based enumeration technique to generate the full set of potential layouts from any given number of mechanical elements. This enumeration is followed by a performance assessment of all layouts to pinpoint the optimal absorber configuration for the given problem. The methodology’s automation capability and versatility make it suitable for various civil and mechanical engineering applications. The effectiveness of the proposed methodology is demonstrated through two case studies: a vibration absorber design for a wind‐excited tall building and a suspension design for a road vehicle. In both cases, the proposed methodology successfully identifies innovative PVA layouts that surpass traditional designs with minimum additional elements.

In the field of structural dynamics, system identification usually refers to building mathematical models from an experimentally obtained data set. To build reliable models using the measurement data, the mathematical model must be representative of the structure. In this work, attention is given to robust identification of geometrically nonlinear structures, particularly those with large inertial effects. We draw inspiration from reduced-order modelling to determine a suitable model for the system identification. There are large similarities between reduced-order modelling and system identification fields, i.e. both are used to replicate the dynamics of a system using a mathematical model with low complexity. Reduced-order models (ROMs) can accurately capture the physics of a system with a low number of degrees of freedom; thus, in system identification, a model based on the form of a ROM is potentially more robust. Nonlinear system identification of a structure is presented, where inspiration is taken from a novel ROM to form the model. A finite-element model of the structure is built to simulate an experiment, and the identification is performed. It is shown how the ROM-inspired model in the system identification improves the accuracy of the predicted response, in comparison with a standard nonlinear model. As the data are gathered from simulations, system identification is first demonstrated on the high-fidelity data, and then, the fidelity of data is reduced to represent a more realistic experiment. A good response agreement is achieved when using the ROM-inspired model, which accounts for the kinetic energy of un-modelled modes. The estimated parameters of this model are also shown to be more robust and rely on the underlying physics of the system.

There are numerous design possibilities for vibration–suppression systems considering components from multiple domains (e.g., mechanical, hydraulic, pneumatic, electrical). Traditional vibration absorber design approach could only explore limited possibilities, of which the performance is away from optimal. Since the 2000s, network synthesis-based approach has been applied. It allows identification of optimal absorber properties represented by networks consisting of modeling elements (stiffness, damping, inertance), providing significant theoretical performance improvements. However, such improvements have not yet been realized in industry. This is because the following questions have not been answered: (1) What are the network-represented properties of the conventional absorber? (2) How can the optimal network-represented properties be realized considering multidomain physical components? This article provides a method for answering these questions by proposing a novel multidomain synthesis technique, allowing bidirectional transformation between networks and multidomain components. Building on this technique, a vibration–absorber design methodology is proposed, which can construct physical realizations of optimal absorbers considering multidomain components. Another contribution of this work is to propose a novel component, providing a hydraulic realization of compliance ‘embedded’ in a hydraulic network. This methodology is demonstrated using an automotive case study, where the constructed optimal hydraulic suspension provides 23% ride comfort enhancement over the conventional one.