Smith, W, Zhang, N & Hu, W 2011, 'Hydraulically interconnected vehicle suspension: handling performance', Vehicle System Dynamics, vol. 49, no. 1-2, pp. 87-106.View/Download from: UTS OPUS or Publisher's site
This paper extends recent research on vehicles with hydraulically interconnected suspension (HIS) systems. Such suspension schemes have received considerable attention in the research community over the last few years. This is due, in part, to their reported ability to provide stiffness and damping rates dependent on the suspension mode of operation (i.e. the bounce, roll, pitch or articulation of the unsprung masses relative to the sprung mass), rather than relying on the stiffness and damping characteristics of the single wheel stations. The paper uses a nine-degrees-of-freedom (DOF) vehicle model and simulations of a fishhook manoeuvre to assess the handling performance of a vehicle when it is fitted with: (a) a conventional independent suspension, and (b) an HIS. In the case of the latter, the fluid subsystem is modelled using a nonlinear finite-element approach, resulting in a set of coupled, first-order nonlinear differential equations, which describe the dynamics of the integrated mechanicalhydraulic vehicle system. The simulation results indicate that, in general, the HIS-equipped vehicle possesses superior handling, as measured by the sprung mass roll angle, roll rate, roll acceleration, lateral acceleration and the vehicleâs Rollover Critical Factor. The potential effects of the suspension set-up on ride performance are also considered by studying the transient response when one side of the vehicle traverses a half-sine bump. The obtained results are then discussed, and it is shown that they are consistent with previous findings, both by the authors and other researchers. The presented work outlines an alternative approach for studying the dynamics of HIS-equipped vehicles, particularly suited to analyses in the time domain.
Smith, W & Zhang, N 2010, 'Recent developments in passive interconnected vehicle suspension', Frontiers of Mechanical Engineering in China, vol. 5, no. 1, pp. 1-18.View/Download from: UTS OPUS or Publisher's site
This paper presents an overall review on the historical concept development and research advancement of passive hydraulically interconnected suspension (HIS) systems. It starts with an introduction to passive HIS systems and their various incarnations developed over many decades. Next, a description is provided of a recently proposed multidisciplinary approach for the frequencydomain analysis of vehicles fitted with an HIS. The experimental validation and applications of the method to both free and forced vibration analysis are discussed based on a simplified, roll-plane half-car model. A finite-elementmethod- based approddach for modelling the transient dynamics of an HIS vehicle is also briefly outlined. In addition, recent work on the investigation of NVH associated with HIS-equipped vehicles is mentioned. Discussion is then provided on future work to the further understanding of HIS and its applications. The paper concludes that interconnected suspension schemes can provide much greater flexibility to independently specify modal stiffness and damping parameters â a characteristic unique among passive suspensions. It points out that there is a need for system optimisation, and there are troublesome NVH issues that require solutions. It suggests that further research attention and effort be paid to NVH issues and system level optimisation to gain a greater understanding of HIS and to broaden its applications.
Zhang, N, Smith, W & Jeyakumaran, JM 2010, 'Hydraulically interconnected vehicle suspension: background and modelling', Vehicle System Dynamics, vol. 48, no. 1, pp. 17-40.View/Download from: UTS OPUS or Publisher's site
This paper presents a novel approach for the frequency domain analysis of a vehicle fitted with a general hydraulically interconnected suspension (HIS) system. Ideally, interconnected suspensions have the capability, unique among passive systems, to provide stiffness and damping characteristics dependent on the all-wheel suspension mode in operation.Abasic, lumped-mass, four-degree-of-freedom half-car model is used to illustrate the proposed methodology. The mechanicalâfluid boundary condition in the double-acting cylinders is modelled as an external force on the mechanical system and amoving boundary on the fluid system. The fluid system itself is modelled using the hydraulic impedance method, in which the relationships between the dynamic fluid states, i.e. pressures and flows, at the extremities of a single fluid circuit are determined by the transfer matrix method. A set of coupled, frequency-dependent equations, which govern the dynamics of the integrated half-car system, are then derived and the application of these equations to both free and forced vibration analysis is explained. The fluid system impedance matrix for the two general wheel-pair interconnection types â anti-synchronous and anti-oppositional â is also given. To further outline the application of the proposed methodology, the paper finishes with an example using a typical anti-roll HIS system. The integrated half-car systemâs free vibration solutions and frequency response functions are then obtained and discussed in some detail. The presented approach provides a scientific basis for investigating the dynamic characteristics of HIS-equipped vehicles, and the results offer further confirmation that interconnected suspension schemes can provide, at least to some extent, individual control of modal stiffness and damping characteristics.
Smith, W, Zhang, N & Jeyakumaran, JM 2010, 'Hydraulically interconnected vehicle suspension: theoretical and experimental ride analysis', Vehicle System Dynamics, vol. 48, no. 1, pp. 41-64.View/Download from: UTS OPUS or Publisher's site
In this paper, a previously derived model for the frequency-domain analysis of vehicles with hydraulically interconnected suspension (HIS) systems is applied to the ride analysis of a four-degrees of freedom roll-plane, half-car under a rough road input. The entire road surface is assumed to be a realisation of a two-dimensional Gaussian homogenous and isotropic random process. The frequency responses of the half-car, in terms of bounce and roll acceleration, suspension deflection and dynamic tyre forces, are obtained under the road input of a single profile represented by its power spectral density function. Simulation results obtained for the roll-plane half-car fitted with an HIS and those with conventional suspensions are compared in detail. In addition, sensitivity analysis of key parameters of the HIS to the ride performance is carried out through simulations. The paper also presents the experimental validation of the analytical results of the free and forced vibrations of the roll-plane half-car. The hydraulic and mechanical system layouts, data acquisition system and the external force actuation mechanism of the test set-up are described in detail. The methodology for free and forced vibration tests and the application of mathematical models to account for the effective damper valve pressure loss are explained. Results are provided for the free and forced vibration testing of the halfcar with different mean operating pressures. Comparisons are also given between the test results and those obtained from the system model with estimated damper valve loss coefficients. Furthermore, discussions on the deficiencies and practical implications of the proposed model and suggestions for future investigation are provided. Finally, the key findings of the investigation on the ride performance of the roll-plane half-car are summarised.
Smith, W & Zhang, N 2010, 'Hydraulically Interconnected Vehicle Suspension: Optimization And Sensitivity Analysis', Proc. of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 224, no. D11, pp. 1335-1355.View/Download from: UTS OPUS or Publisher's site
This paper extends recent research on vehicles with hydraulically interconnected suspension (HIS) systems. Such suspension schemes have received considerable attention in the research community over the last few years. This is due, in part, to their reported ability to provide stiffness and damping rates dependent on the suspension mode of operation (i.e. the bounce, roll, pitch, or articulation of the unsprung masses relative to the sprung mass), rather than relying on the stiffness and damping characteristics of the single wheel stations. In this paper, the optimization of such a system is considered. Use is made of a previously derived four-degree-of-freedom model of a roll-plane half-car fitted with a typical antiroll HIS system. Objective functions are then developed, based on the desire to improve ride comfort and to minimize suspension working space and tyre normal force fluctuations. With this formulation, a large number of optimal solutions are found and presented graphically, and the performance limitations and trade-offs between the desired objectives are illustrated. To contextualize these results, a similar optimization process is applied to a half-car with a conventional independent suspension. Four optimal parameter combinations are then selected as base points for further examination of the HIS vehicle. This is done by way of a basic sensitivity analysis, based on the local method, which involves single-parameter perturbations about a base point. The objective of the paper is to outline the dynamic performance, trade-offs, and limitations of an HIS-equipped vehicle, and to identify the systemâs most important parameters.
Du, H, Zhang, N & Smith, W 2009, 'Robust yaw moment control for vehicle handling and stability', SAE International Journal of Passenger Cars - Mechanical Systems, vol. 2, no. 1, pp. 772-779.View/Download from: UTS OPUS or Publisher's site
This paper presents a robust controller design method for improving vehicle lateral stability and handling performance. In particular, the practical load variation will be taken into account in the controller synthesis process such that the controller can keep the vehicle lateral stability and handling performance regardless of the load variation. Based on a two-degree-of-freedom (2-DOF) lateral dynamics model, a model-based Takagi-Sugeno fuzzy control strategy is applied to design such a controller and the sufficient conditions for designing such a controller are given in terms of linear matrix inequalities (LMIs) which can be solved efficiently using currently available numerical software. Numerical simulations are used to validate the effectiveness of the proposed control approach.
Smith, W & Zhang, N 2009, 'Experimental and Theoretical Investigation into the Dynamics of a Half-Car with an Interconnected Passive Suspension', SAE World Congress & Exhibition 2009 - Technical Paper, SAE World Congress, SAE International, Detroit, MI, USA, pp. 1-10.View/Download from: UTS OPUS
In this paper, a previously derived theoretical model of an integrated hydraulically interconnected suspension (HIS) half-car system is experimentally validated. The paper outlines the development of the HIS fluid system model and its integration into a four degree-of-freedom, roll-plane half-car system. An experimental approach to validate the model is outlined, and the resulting purposebuilt half-car test facility is described in detail. Experimental results from both free and forced vibration testing are presented and compared with model-based simulations. In general, very good agreement is observed. Limitations of the testing approach and reasons for any discrepancies are discussed. Finally, the broader implications of the obtained results in terms of practical HIS system design are considered.
Smith, W, Zhang, N & Jeyakumaran, JM 2008, 'Free vibration of vehicles with interconnected suspensions', XXII International Congress of Theoretical and Applied Mechanics: ICTAM 2008 CD-ROM Proceedings, International Congress of Theoretical and Applied Mechanics, University of Adelaide, Australia, Adelaide, Australia, pp. 1-2.View/Download from: UTS OPUS
This paper presents a computationally efficient approach for the free vibration analysis of vehicles fitted with a general hydraulically interconnected suspension (HIS) system. A linear half-car model is analysed as an example. Details of the equations which govern the coupled dynamics of the integrated half-car system are given and a numerical root searching scheme is outlined. The results offer further confirmation that interconnected suspensions can provide some control over modal stiffness and damping.
Smith, W, Zhang, N & Jeyakumaran, JM 2007, 'Hydraulically Interconnected Suspension Parameter Sensitivity in Half-Car Ride Performance', SAE Technical Papers - SAE World Congress, SAE World Congress, SAE International, Detroit, Michigan, USA, pp. 1-8.View/Download from: UTS OPUS
In this paper, the development of a hydraulically interconnected suspension (HIS) system model and the integration of this model into a four degree-of-freedom half-car system is briefly introduced. The appropriate frequency response functions are derived in order to simulate the system response to a stochastic road profile. The sprung mass vertical and roll accelerations, the dynamic normal tyre force, and the suspension deflection are considered in the frequency domain up to 20 Hz. Four key hydraulic system parameters are identified and investigated to gauge their effects on the system's dynamic performance. The results indicate that HIS system performance can be greatly affected by these hydraulic parameters.
Jeyakumaran, JM, Zhang, N & Smith, W 2007, 'Transient Characteristics of a Hydraulically Interconnected Suspension System', SAE Technical Papers: SAE World Congress, SAE World Congress, the Society of Automotive Engineers, Detroit, Michigan, USA, pp. 1-11.View/Download from: UTS OPUS
This paper describes vehicle dynamic models that capture the large amplitude transient characteristics of a passive Hydraulically Interconnected Suspension (HIS) system. Accurate mathematical models are developed to represent pressure-flow characteristics, fluid properties, damper valves, accumulators and nonlinear coupling between mechanical and fluid systems. The vehicle is modeled as a lumped mass system with half- and fullcar configurations. The transient performance is demonstrated by numerical integration of the second order nonlinear differential equations. The stiffness and damping characteristics corresponding to vehicle bounce, roll and pitch motions are extracted from the transient simulation. Simulation results clearly demonstrate the superiority of the HIS system during vehicle handling and stability by providing additional roll stiffness and reduced articulation stiffness.
Smith, W, Zhang, N & Jeyakumaran, JM 2007, 'High frequency parameter sensitivity in hydraulically interconnected suspensions', Proceedings of the Fifth Australasian Congress on Applied Mechanics, Australasian Congress on Applied Mechanics, Engineers Australia, Brisbane, Australia, pp. 608-613.View/Download from: UTS OPUS
In this paper, the development of a hydraulically interconnected suspension (HIS) system model and its integration into a four degree-of-freedom half-car system is briefly introduced. Frequency response functions are derived in order to simulate the system response to a stochastic road profile. The sprung mass vertical and roll accelerations are considered in the frequency domain up to 1000 Hz. Four key hydraulic system parameters which affect the systemâs high frequency dynamics but not its low frequency response are identified and investigated. The results indicate that HIS system performance in the high frequency range (50-1000 Hz) can be greatly affected by these hydraulic parameters, while the favourable ride characteristics typical of HIS vehicles are retained.
Zhang, N, Smith, W, Jeyakumaran, JM & Hu, W 2007, 'Determination of Modal Parameters of a Half-Car Fitted with a Hydraulically Interconnected Suspension from Simulated Free decay Responses', Proceedings of the Fifth Australasian Congress on Applied Mechanics, Australasian Congress on Applied Mechanics, Engineers Australia, Brisbane, Australia, pp. 601-607.View/Download from: UTS OPUS
This paper presents an alternative approach for determining the vibration modal parameters, in terms of natural frequencies, damping ratios and modal shapes of a roll-plane half-car fitted with a general hydraulically interconnected suspension system. The dynamic model of the system, which consists of the sprung mass and the HIS and the wheels, is formulated using the state space representation approach. The state variables describing rigid body motions of the sprung and unsprung masses are heavily coupled with those describing the dynamics of HIS fluid circuits. A numerical simulation scheme is developed to obtain the transient and free decay responses of the half car vehicle using specific initial conditions or road inputs. The obtained results are compared with those determined from the free vibration analysis of the system using the transfer matrix method. Discussions on the advantages and limitations of the presented method are also provided.
Smith, W, Zhang, N & Jeyakumaran, JM 2006, 'Ride Simulations of a Half-car with a Hydraulically Interconnected Passive Suspension', Proceedings of FISITA 2006 World Automotive Congress, FISITA World Automotive Congress, Society of Automotive Engineers of Japan Inc, Yokohama, Japan, pp. 1-10.View/Download from: UTS OPUS
Jeyakumaran, JM, Smith, W & Zhang, N 2006, 'Transient Characteristic of a Hydraulically Interconnected Suspension System', Proceedings of FISITA 2006 World Automotive Congress, FISITA World Automotive Congress, Society of Automotive Engineers of Japan Inc, Yokohama, Japan, pp. F2006 V123.1-10.View/Download from: UTS OPUS