Roll- and pitch-plane-coupled hydro-pneumatic suspension. Part 2: dynamic response analyses

In the first part of this study, the potential performance benefits of fluidically coupled passive suspensions were demonstrated through analyses of suspension properties, design flexibility and feasibility. In this second part of the study, the dynamic responses of a vehicle equipped with different configurations of fluidically coupled hydro-pneumatic suspension systems are investigated for more comprehensive assessments of the coupled suspension concepts. A generalised 14 degree-of-freedom nonlinear vehicle model is developed and validated to evaluate vehicle ride and handling dynamic responses and suspension anti-roll and anti-pitch characteristics under various road excitations and steering/braking manoeuvres. The dynamic responses of the vehicle model with the coupled suspension are compared with those of the unconnected suspensions to demonstrate the performance potential of the fluidic couplings. The dynamic responses together with the suspension properties suggest that the full-vehicle-coupled hydro-pneumatic suspension could offer considerable potential in realising enhanced ride and handling performance, as well as improved anti-roll and anti-pitch properties in a very flexible and energy-saving manner.     

Rollover mitigation for a heavy commercial vehicle

A heavy commercial vehicle has a high probability of rollover because it is usually loaded heavily and thus has a high center of gravity. An anti-roll bar is efficient for rollover mitigation, but it can cause poor ride comfort when the roll stiffness is excessively high. Therefore, active roll control (ARC) systems have been developed to optimally control the roll state of a vehicle while maintaining ride comfort. Previously developed ARC systems have some disadvantages, such as cost, complexity, power consumption, and weight. In this study, an ARC-based rear air suspension for a heavy commercial vehicle, which does not require additional power for control, was designed and manufactured. The rollover index-based vehicle rollover mitigation control scheme was used for the ARC system. Multi-body dynamic models of the suspension subsystem and the full vehicle were used to design the rear air suspension and the ARC system. The reference rollover index was tuned through lab tests. Field tests, such as steady state cornering tests and step steer tests, demonstrated that the roll response characteristics in the steady state and transient state were improved.     

无塔人行悬索桥设计研究

基于有限位移法,对某无塔非对称人行悬索桥进行了设计研究,根据工程的实际特点,对该桥的总体布置、主缆、吊杆以及加劲梁等进行了合理选择,对受力进行了相应分析,同时也对缆风索进行了设计研究。结果表明,设置缆风索能大幅提升结构整体刚度,从而使结构自振基频得到提高,且效果明显。研究的结论可为今后人行悬索桥的设计提供有益的参考,也为该类型桥梁的抗风设计等奠定基础。     

An analytical design approach for self-powered active lateral secondary suspensions for railway vehicles

In this paper, an analytical design approach for the development of self-powered active suspensions is investigated and is applied to optimise the control system design for an active lateral secondary suspension for railway vehicles. The conditions for energy balance are analysed and the relationship between the ride quality improvement and energy consumption is discussed in detail. The modal skyhook control is applied to analyse the energy consumption of this suspension by separating its dynamics into the lateral and yaw modes, and based on a simplified model, the average power consumption of actuators is computed in frequency domain by using the power spectral density of lateral alignment of track irregularities. Then the impact of control gains and actuators’ key parameters on the performance for both vibration suppressing and energy recovery/storage is analysed. Computer simulation is used to verify the obtained energy balance condition and to demonstrate that the improved ride comfort is achieved by this self-powered active suspension without any external power supply.     

Fundamental Issues in Suspension Design for Heavy Road Vehicles

Heavy road vehicles play an important role in the economy of many countries by providing an efficient means of transporting freight. Such vehicles can also have a significant impact on safety, the infrastructure and the environment. The design of the suspension affects the performance of the vehicle in terms of ride, infrastructure damage, suspension working space, energy consumption, rollover stability, yaw stability, braking and traction. The published literature on suspension design for heavy road vehicles is reviewed. It is found that extensive knowledge exists, but that there are areas where improved understanding is needed. Areas identified as fundamental issues requiring attention include ride discomfort criteria, secondary suspensions, and controllable suspensions. Two issues in particular are examined in detail: suspension tuning and suspension configuration. In the tuning of suspension parameter values for vibration performance, numerical optimisation techniques have been used extensively, but generic tuning strategies have not been widely developed. Modal analysis is proposed as a technique for gaining the insight into vehicle vibration behaviour necessary to enable tuning strategies to be devised. As an example, the technique is applied to the pitch-plane vibration of a tractor-semitrailer. In analyses of new suspension configurations or concepts, comparison with alternative concepts is not always made. Lack of such comparisons makes the selection of an optimum concept difficult. Analysis of alternative concepts using simple mathematical models, and comparison of their performance using common criteria, is advocated for enabling informed selection of an optimum. An example involving two alternative roll control systems is used to demonstrate the issue.     

Roll- and pitch-plane coupled hydro-pneumatic suspension

Passive fluidically coupled suspensions have been considered to offer a promising alternative solution to the challenging design of a vehicle suspension system. A theoretical foundation, however, has not been established for fluidically coupled suspension to facilitate its broad applications to various vehicles. The first part of this study investigates the fundamental issues related to feasibility and properties of the passive, full-vehicle interconnected, hydro-pneumatic suspension configurations using both analytical and simulation techniques. Layouts of various interconnected suspension configurations are illustrated based on two novel hydro-pneumatic suspension strut designs, both of which provide a compact design with a considerably large effective working area. A simplified measure, vehicle property index, is proposed to permit a preliminary evaluation of different interconnected suspension configurations using qualitative scaling of the bounce-, roll-, pitch- and warp-mode stiffness properties. Analytical formulations for the properties of unconnected and three selected X-coupled suspension configurations are derived, and simulation results are obtained to illustrate their relative stiffness and damping properties in the bounce, roll, pitch and warp modes. The superior design flexibility feature of the interconnected hydro-pneumatic suspension is also discussed through sensitivity analysis of a design parameter, namely the annular piston area of the strut. The results demonstrate that a full-vehicle interconnected hydro-pneumatic suspension could provide enhanced roll- and pitch-mode stiffness and damping, while retaining the soft bounce- and warp-mode properties. Such an interconnected suspension thus offers considerable potential in realising enhanced decoupling among the different suspension modes.     

Fundamental Issues in Suspension Design for Heavy Road Vehicles

Heavy road vehicles play an important role in the economy of many countries by providing an efficient means of transporting freight. Such vehicles can also have a significant impact on safety, the infrastructure and the environment. The design of the suspension affects the performance of the vehicle in terms of ride, infrastructure damage, suspension working space, energy consumption, rollover stability, yaw stability, braking and traction. The published literature on suspension design for heavy road vehicles is reviewed. It is found that extensive knowledge exists, but that there are areas where improved understanding is needed. Areas identified as fundamental issues requiring attention include ride discomfort criteria, secondary suspensions, and controllable suspensions. Two issues in particular are examined in detail: suspension tuning and suspension configuration. In the tuning of suspension parameter values for vibration performance, numerical optimisation techniques have been used extensively, but generic tuning strategies have not been widely developed. Modal analysis is proposed as a technique for gaining the insight into vehicle vibration behaviour necessary to enable tuning strategies to be devised. As an example, the technique is applied to the pitch-plane vibration of a tractor-semitrailer. In analyses of new suspension configurations or concepts, comparison with alternative concepts is not always made. Lack of such comparisons makes the selection of an optimum concept difficult. Analysis of alternative concepts using simple mathematical models, and comparison of their performance using common criteria, is advocated for enabling informed selection of an optimum. An example involving two alternative roll control systems is used to demonstrate the issue.     

Adaptive Ride Control In Active Suspension Systems

The paper describes the development of an adaptive control algorithm for active suspension systems based on optimal regulation methods. The objective is to design an algorithm which will automatically tune at start-up to changed vehicle conditions and adaptively re-tune to changes in driving conditions (in particular road generated disturbances). The proposed algorithm is a self-tuning regulator based on generalised minimum variance (GMV) control. Simulation results obtained for a 3 degree-of-freedom (DOF) quarter car suspension demonstrate potential benefits of fully adaptive control in automotive suspensions.     

Heavy vehicle pitch dynamics and suspension tuning. Part I: unconnected suspension

The influence of suspension tuning of passenger cars on bounce and pitch ride performance has been explored in a number of studies, while only minimal efforts have been made for establishing similar rules for heavy vehicles. This study aims to explore pitch dynamics and suspension tunings of a two-axle heavy vehicle with unconnected suspension, which could also provide valuable information for heavy vehicles with coupled suspensions. Based on a generalised pitch-plane model of a two-axle heavy vehicle integrating either unconnected or coupled suspension, three dimensionless measures of suspension properties are defined and analysed—namely the pitch margin (PM), pitch stiffness ratio (PSR), and coupled pitch stiffness ratio (CPSR)—for different unconnected suspension tunings and load conditions. Dynamic responses of the vehicle with three different load conditions and five different tunings of the unconnected suspension are obtained under excitations arising from three different random road roughness conditions and a wide range of driving speeds, and braking manoeuvres. The responses are evaluated in terms of performance measures related to vertical and pitch ride, dynamic tyre load, suspension travel, and pitch-attitude control characteristics of the vehicle. Fundamental relationships between the vehicle responses and the proposed suspension measures (PM, PSR, and CPSR) are established, based on which some basic suspension tuning rules for heavy vehicles with unconnected suspensions are also proposed.     

Optimal selection of suspension parameters in large scale vehicle models

Optimum values are selected for the suspension damping and stiffness parameters of complex car models, subjected to road excitation, by applying suitable numerical methodologies. These models result from a detailed finite-element discretisation and possess a relatively large number of degrees of freedom. They also involve strongly nonlinear characteristics, due mostly to large rigid body rotation of some of their components and the properties of the connection elements. First, attention is focused on gaining some insight into the dynamics of the mechanical models examined, resulting when the vehicle passes over roads involving typical geometric profiles. Then, the emphasis is shifted to presenting results obtained by applying appropriate optimisation methodologies. For this purpose, three classes of design criteria are first set up, referring to passenger ride comfort, suspension travel and car road holding and yielding the most important suspension stiffness and damping parameters. Originally, the optimisation is performed by forming a composite cost function and employing a single-objective optimisation method. Since the design criteria are conflicting, a multi-objective optimisation methodology is also set up and applied subsequently.     

Development and Simulation of a Novel Roll Control System for the Interconnected Hydragas® Suspension

The design of passive suspension systems using conventional springs and dampers is limited by the need to compromise between vehicle ride and handling functions. The Interconnected Hydragas Suspension fitted to the current Rover 100 series partially allays this compromise by reducing the vehicle pitch stiffness witfiout affecting the bounce and roll stiffnesses. However, the vehicle body is still subject to roll during cornering manoeuvres. This paper outlines the development and simulation of a sealed low bandwidth active roll control suspension based on the existing Interconnected Hydragas System. Following a brief explanation of the Hydragas suspension operating principle die paper outlines the design of a fluid displacer or 'shuttle'. This shuttle enables control over body roll during manoeuvres by displacing fluid from one side of the car to the other. Care is taken to ensure low power consumption whilst the sealed nature of the fluid based suspension units guarantee reliable operation without leakage. Using computer simulation, the system performance is predicted and compared with experimental measurements. It is shown that roll during manoeuvres can be reduced or eliminated using a minimum of hydraulic components with only moderate power consumption and cost.     

Comparison of the properties of active and semiactive suspension

In this article, the properties of active and semi-active suspension for heavy goods vehicles are compared. The criteria for the comparison are the RMS sprung mass vertical acceleration, RMS dynamic tyre force, and suspension power consumption. The active system is based on an air-spring with controlled in-flow and out-flow of the air. In the semi-active system, a controlled hydraulic damper is employed. The results concerning the semi-active suspension system were taken from the article by Besinger et al. [Besinger, F.H., Cebon, D. and Cole, D.J., 1995, Force control of a semi-active damper. Vehicle System Dynamics, 24(9), 695-723.].     

Control Algorithms for Active Cab Suspensions on Agricultural Tractors

This paper describes active agricultural tractor cab suspensions based on optimal control theory. Control algorithms based on time invariant state feedback and on adaptive control are developed and studied. The influence of different observers and measurement noise levels on the vibration damping capacity are studied as well as the power consumption for the suspensions.

The principle for the adaptive algorithm is based on the parameters in the penalty matrices being varied so that the resulting controller always strives to make optimum use of available travel space. The feedback and observer gains are also changed depending on the characteristics of the vehicle's frame movements.

The results show that it is possible to design an effective active suspension, but that the choice of feedback gains must be dependent on the surface characteristics to reach satisfactory vibration damping performance.     

Comparison of the properties of active and semiactive suspension

In this article, the properties of active and semi-active suspension for heavy goods vehicles are compared. The criteria for the comparison are the RMS sprung mass vertical acceleration, RMS dynamic tyre force, and suspension power consumption. The active system is based on an air-spring with controlled in-flow and out-flow of the air. In the semi-active system, a controlled hydraulic damper is employed. The results concerning the semi-active suspension system were taken from the article by Besinger et al. [Besinger, F.H., Cebon, D. and Cole, D.J., 1995, Force control of a semi-active damper. Vehicle System Dynamics, 24(9), 695–723.].     

Fuel consumption of fuel cell hybrid vehicles considering battery SOC differences

Fuel cell hybrid vehicles (FCHVs) have become one of the most promising candidates for future transportation due to current energy supply problem and environmental problem. Fuel economy is an important factor in FCHVs. In order to properly evaluate the fuel economy of an FCHV, the initial battery state of charge (SOC) and the final battery SOC have to be identical so that the effect of the battery energy usage on the fuel economy is neglected. In the simulation or in the real driving, however, the final battery SOC is usually different from the initial battery SOC, and the final battery SOC often depends on the power management strategy. To consider the difference between the two battery SOC values, the concept of equivalent fuel consumption is presented by two methods. One is based on the relationship between delta SOC and delta fuel consumption, and the other is based on the optimal control theory. Two rule-based power management strategies for an FCHV are presented, and for each strategy, the fuel economy is evaluated based on the two methods. The characteristics of the two methods are discussed and compared, and the superior one is selected based on the comparison.     

EPS与主动悬架系统自适应模糊集成控制的仿真与试验研究

在建立的汽车整车主动悬架和EPS动力学模型(包含转向运动、俯仰运动和侧倾运动等模型)的基础上,运用自适应模糊控制方法,利用车身姿态的变化动态地调节主动悬架控制器和EPS控制器的输出,实现了对EPS和主动悬架系统的集成控制。为了验证控制系统的可行性和有效性,分别进行了仿真和实车道路试验。结果表明,集成控制显著提高了汽车的行驶平顺性和操纵稳定性,整车综合性能明显优于传统的悬架和转向系统。     

Hierarchical optimisation of the design parameters of a vehicle suspension system

This paper presents a design methodology for the mechanical systems entitled First Design. It is based on a hierarchical organisation of the design, taking into account the notion of robustness at an early phase of the project. The aim is to improve the quality of the system in order to make it robust, less sensitive to the variability of the external parameters and design parameters. We distinguish two main stages of the design cycle: one concerning functional parameters and another concerning physical parameters. The methodology is based on simplified models, on sensitivity analysis and on robust multi-objective optimisation. As an example, the methodology will be applied to the optimisation of vehicle suspension system design parameters. For each stage of the hierarchical design, adapted simplified models, sensitivity analyses and optimisation processes will be studied and applied to our vehicle suspension system.     

Hierarchical optimisation of the design parameters of a vehicle suspension system

This paper presents a design methodology for the mechanical systems entitled First Design. It is based on a hierarchical organisation of the design, taking into account the notion of robustness at an early phase of the project. The aim is to improve the quality of the system in order to make it robust, less sensitive to the variability of the external parameters and design parameters. We distinguish two main stages of the design cycle: one concerning functional parameters and another concerning physical parameters. The methodology is based on simplified models, on sensitivity analysis and on robust multi-objective optimisation. As an example, the methodology will be applied to the optimisation of vehicle suspension system design parameters. For each stage of the hierarchical design, adapted simplified models, sensitivity analyses and optimisation processes will be studied and applied to our vehicle suspension system.     

Wear/comfort Pareto optimisation of bogie suspension

Pareto optimisation of bogie suspension components is considered for a 50 degrees of freedom railway vehicle model to reduce wheel/rail contact wear and improve passenger ride comfort. Several operational scenarios including tracks with different curve radii ranging from very small radii up to straight tracks are considered for the analysis. In each case, the maximum admissible speed is applied to the vehicle. Design parameters are categorised into two levels and the wear/comfort Pareto optimisation is accordingly accomplished in a multistep manner to improve the computational efficiency. The genetic algorithm (GA) is employed to perform the multi-objective optimisation. Two suspension system configurations are considered, a symmetric and an asymmetric in which the primary or secondary suspension elements on the right- and left-hand sides of the vehicle are not the same. It is shown that the vehicle performance on curves can be significantly improved using the asymmetric suspension configuration. The Pareto-optimised values of the design parameters achieved here guarantee wear reduction and comfort improvement for railway vehicles and can also be utilised in developing the reference vehicle models for design of bogie active suspension systems.