Mechanical and Control Design of a Variable Geometry Active Suspension System

In this study, a variable geometry active suspension system is considered. Actuation is employed to vary the leverage ratio between spring/damper unit and road wheel assembly. Since actuation is substantially perpendicular to the main suspension unit forces, work is primarily done only against frictional resistances to motion and the systems have inherently low force and energy requirements. Mechanical design and control system design involving proportional/differential elements or neural networks are discussed. System performance in self-levelling, free vibrations and manoeuvring of a theoretical vehicle are calculated. Good control of roll angle and jacking responses are predicted and energy economy is confirmed by these trials, which include a detailed consideration and modelling of the electrical actuators. The results reinforce the notion that variable geometry schemes have practical applications potential and are worthy of further research effort.     

On the achievable performance using variable geometry active secondary suspension systems in commercial vehicles

There is a need to further improve driver comfort in commercial vehicles. The variable geometry active suspension offers an interesting option to achieve this in an energy efficient way. However, the optimal control strategy and the overal performance potential remains unclear. The aim of this paper is to quantify the level of performance improvement that can theoretically be obtained by replacing a conventional air sprung cabin suspension design with a variable geometry active suspension. Furthermore, the difference between the use of a linear quadratic (LQ) optimal controller and a classic skyhook controller is investigated. Hereto, an elementary variable geometry actuator model and experimentally validated four degrees of freedom quarter truck model are adopted. The results show that the classic skyhook controller gives a relatively poor performance while a comfort increase of 17–28% can be obtained with the LQ optimal controller, depending on the chosen energy weighting. Furthermore, an additional 75% comfort increase and 77% energy cost reduction can be obtained, with respect to the fixed gain energy optimal controller, using condition-dependent control gains. So, it is concluded that the performance potential using condition-dependent controllers is huge, and that the use of the classic skyhook control strategy should, in general, be avoided when designing active secondary suspensions for commercial vehicles.     

State of the art survey: active and semi-active suspension control

This survey paper aims to provide some insight into the design of suspension control system within the context of existing literature and share observations on current hardware implementation of active and semi-active suspension systems. It reviews the performance envelop of active, semi-active, and passive suspensions with a focus on linear quadratic-based optimisation including a specific example. The paper further discusses various design aspects including other design techniques, the decoupling of load and road disturbances, the decoupling of pitch and heave modes, the use of an inerter as an additional design element, and the application of preview. Various production and near production suspension systems were examined and described according to the features they offer, including self-levelling, variable damping, variable geometry, and anti-roll damping and stiffness. The lessons learned from these analytical insights and related hardware implementations are valuable and can be applied towards future active or semi-active suspension design.     

Vehicle Dynamic Analysis and Evaluation of Continuously Controlled Semi-Active Suspensions Using Hardware-in-the-loop Simulation

A semi-active suspension system with continuously variable damper is greatly expected to be used mainly in the future as a high-performance suspension system due to its cost-effectiveness, light weight, and low energy consumption. In this paper, to develop a suitable control logic for the semi-active suspension system, the hardware-in-the-loop simulation is performed for the experimental continuously variable damper combined with a quarter-car model, and the simulation results are compared for passive, on/off controlled, and continuously controlled dampers in the aspects of ride comfort and driving safety, assuming each damper to be installed on the vehicle.     

Suboptimal Control Design of Active and Passive Suspensions Based on a Full Car Model

An optimal control design method is introduced and then applied to the optimum design of active and passive suspension systems. A basic three-dimensional 7-DOF car riding model subjected to four correlated random road inputs is considered. The design method is basically developed to allow arbitrary choice of sensors for various car state variables to be used for feedback control of each suspension unit. Previous studies show that full-state control laws and even some limited-state control laws often include feedback gains which are almost zero. Some other gains, although not zero, don't play an important role in improving the system performance measures. With the method proposed in this work, every suspension unit can have its own feedback measurements and the criterion function can be related to all state and control variables. Thus a large number of active and semi-active suspension systems with full- or limited-state control laws based on different measurement combination can be suggested, studied, and compared with each other. Instead of comparing these optimized active and semi-active suspension systems with a basic, passive suspension, the passive system itself is optimized with the same criterion. Simulations in the time domain and frequency analyses are performed, and comparisons are made among the systems in terms of r.m.s. car response measures and ISO riding comfort criterion.     

主动汽车悬架的非线性控制

本文采用１／４车模型对天棚阻尼器和主动悬架的动力学性能进行分析，针对执行器的非线性特性，探讨了微分几何法和反馈法线必互法在主动悬架控制中的应用，在系统控制设计中采用了离散滑模法，仿真结果显示非线性控制律能有效地改善主动悬架的隔振特性。     

Roll stabilisation of road vehicles using a variable stiffness suspension system

A variable stiffness architecture is used in the suspension system to counteract the body roll moment, thereby enhancing the roll stability of the vehicle. The variation of stiffness concept uses the ‘reciprocal actuation’ to effectively transfer energy between a vertical traditional strut and a horizontal oscillating control mass, thereby improving the energy dissipation of the overall suspension. The lateral dynamics of the system is developed using a bicycle model. The accompanying roll dynamics are also developed and validated using experimental data. The positions of the left and right control masses are sequentially allocated to reduce the effective body roll and roll rate. Simulation results show that the resulting variable stiffness suspension system has more than 50% improvement in roll response over the traditional constant stiffness counterparts. The simulation scenarios examined is the fishhook manoeuvre.     

轿车动力柴油化的技术措施探析

介绍了电控泵喷嘴、电控高压共轨喷油系统、可变几何涡轮技术、4气门技术、冷却废气再循环、燃烧系统和排气后处理等工作原理以及对轿车柴油机性能的影响,分析了实现柴油机轻量化等技术措施对整车性能的重要性。文中还列举了当前国内外典型的几种先进的轿车用柴油机的性能和技术特点,指出轿车柴油化是未来轿车动力的发展方向。     

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.     

A new active variable stiffness suspension system using a nonlinear energy sink-based controller

This paper presents the active case of a variable stiffness suspension system. The central concept is based on a recently designed variable stiffness mechanism which consists of a horizontal control strut and a vertical strut. The horizontal strut is used to vary the load transfer ratio by actively controlling the location of the point of attachment of the vertical strut to the car body. The control algorithm, effected by a hydraulic actuator, uses the concept of nonlinear energy sink (NES) to effectively transfer the vibrational energy in the sprung mass to a control mass, thereby reducing the transfer of energy from road disturbance to the car body at a relatively lower cost compared to the traditional active suspension using the skyhook concept. The analyses and simulation results show that a better performance can be achieved by subjecting the point of attachment of a suspension system, to the chassis, to the influence of a horizontal NES system.     

An efficient sensitivity analysis method for modified geometry of Macpherson suspension based on Pearson correlation coefficient

The main purpose of this paper is to propose a new method for designing Macpherson suspension, based on the Sobol indices in terms of Pearson correlation which determines the importance of each member on the behaviour of vehicle suspension. The formulation of dynamic analysis of Macpherson suspension system is developed using the suspension members as the modified links in order to achieve the desired kinematic behaviour. The mechanical system is replaced with an equivalent constrained links and then kinematic laws are utilised to obtain a new modified geometry of Macpherson suspension. The equivalent mechanism of Macpherson suspension increased the speed of analysis and reduced its complexity. The ADAMS/CAR software is utilised to simulate a full vehicle, Renault Logan car, in order to analyse the accuracy of modified geometry model. An experimental 4-poster test rig is considered for validating both ADAMS/CAR simulation and analytical geometry model. Pearson correlation coefficient is applied to analyse the sensitivity of each suspension member according to vehicle objective functions such as sprung mass acceleration, etc. Besides this matter, the estimation of Pearson correlation coefficient between variables is analysed in this method. It is understood that the Pearson correlation coefficient is an efficient method for analysing the vehicle suspension which leads to a better design of Macpherson suspension system.     

High Speed Stability for Rail Vehicles Considering Varying Conicity and Creep Coefficients

The critical or hunting speed of solid axle rail vehicles is known to be a strong function of primary suspension stiffness, wheel/rail profile geometry (conicity and gravitational stiffness), wheel/rail friction forces (creep coefficients), bogie/carbody inertia properties, and secondary suspension design. This paper deals with the problem of maximizing the critical speed through design of the primary and secondary suspension but with control only over the range of wheel/rail geometry and friction characteristics. For example, the conicity may varie from .05 to .3 and the linear creep coefficients from 25% to 100% of the predicted Kalker values.

It is shown that the maximum critical speed is greatly limited by the wheel/rail geometry and friction variations. It is also shown that, when lateral curving and ride quality are considered, the best design approach is to select an intermediate primary longitudinal stiffness, to limit the lowest value of conicity (e.g. to .1 or .2) by wheel profile redesign, increasing the secondary yaw damping value (yaw relaxation) and optimizing the primary and secondary lateral stiffness.     

Energy Dissipation Due to Vehicle/Track Interaction

The effects of track irregularities and wheel profile on the amount of energy dissipated in railroad freight vehicles is examined. A nonlinear computational model is used to determine the average dissipation in the vehicle suspension and the wheel/rail contact patches. This dissipation is a component of the total resistance force acting on the vehicle. Parametric results are presented showing the effects of track geometry, wheel profile, suspension design, and hunting on train resistance. Track geometry studies consider the effects of track quality and curving. The AAR 1:20 wheel profile and the Heumann wheel profile are compared under various operating conditions. Compared with the Heumann profile, the AAR 1:20 profile is shown to have lower average resistance on good quality tangent track, but higher average resistance in steady curves. A trade-off exists between the two profiles when dynamic curve entry is considered.     

High Speed Stability for Rail Vehicles Considering Varying Conicity and Creep Coefficients

SUMMARY

The critical or hunting speed of solid axle rail vehicles is known to be a strong function of primary suspension stiffness, wheel/rail profile geometry (conicity and gravitational stiffness), wheel/rail friction forces (creep coefficients), bogie/carbody inertia properties, and secondary suspension design. This paper deals with the problem of maximizing the critical speed through design of the primary and secondary suspension but with control only over the range of wheel/rail geometry and friction characteristics. For example, the conicity may varie from .05 to .3 and the linear creep coefficients from 25% to 100% of the predicted Kalker values.

It is shown that the maximum critical speed is greatly limited by the wheel/rail geometry and friction variations. It is also shown that, when lateral curving and ride quality are considered, the best design approach is to select an intermediate primary longitudinal stiffness, to limit the lowest value of conicity (e.g. to .1 or .2) by wheel profile redesign, increasing the secondary yaw damping value (yaw relaxation) and optimizing the primary and secondary lateral stiffness.     

Energy Dissipation Due to Vehicle/Track Interaction

SUMMARY

The effects of track irregularities and wheel profile on the amount of energy dissipated in railroad freight vehicles is examined. A nonlinear computational model is used to determine the average dissipation in the vehicle suspension and the wheel/rail contact patches. This dissipation is a component of the total resistance force acting on the vehicle. Parametric results are presented showing the effects of track geometry, wheel profile, suspension design, and hunting on train resistance. Track geometry studies consider the effects of track quality and curving. The AAR 1:20 wheel profile and the Heumann wheel profile are compared under various operating conditions. Compared with the Heumann profile, the AAR 1:20 profile is shown to have lower average resistance on good quality tangent track, but higher average resistance in steady curves. A trade-off exists between the two profiles when dynamic curve entry is considered.     

On the Performance Capabilities of Active Automobile Suspension Systems of Limited Bandwidth

Using methods established in earlier work, calculations are carried out to reveal the influence of actuator bandwidth on the performance capabilities of a class of active suspension system for automobiles. The suspension consists of an actuator in series with a spring, the combination being in parallel with a passive damper, and the system is modelled as a single wheel station traversing a random road. The results indicate that a system with a 3 Hz bandwidth actuator and variable damping will have excellent ride performance qualities over a wide range of road roughness conditions. Since such a system can be expected to be easily adaptable to the running conditions, to provide good static and dynamic attitude control, to be capable of contributing to good steering control responses and to be inexpensive in terms of capital and energy consumption costs compared with most of the active systems which have previously been discussed, it is suggested that it is a prime candidate for further study and practical development.     

A Comparison of Adaptive LQG and Nonlinear Controllers for Vehicle Suspension Systems

A design feature of many computer-controlled suspension systems, is their ability to adapt control law parameters to suit prevailing road conditions. Here, for systems employing high bandwidth actuators and state variable feedback control, the benefits of such adaptation are shown to be at best marginal. An optimal adaptive LQG system is compared with a fixed structure nonlinear feedback controller in the context of a simple quarter-vehicle suspension model. Performance comparisons are made, and trends considered under more realistic conditions. In consequence the overall usefulness of this type of adaptation is called into question.     

兼具馈能与主动抗侧倾功能的电控液压悬架系统设计与研究

为解决特种车辆或载重车辆在极端工况下易侧翻的问题,提出了一种兼具馈能与主动抗侧倾功能的电控液压悬架系统。对该悬架系统的主动抗侧倾模式和馈能模式进行了功能原理设计与分析;针对主动抗侧倾模式与馈能模式,构建了电液悬架系统仿真模型;设计了电液悬架系统主动抗侧倾模糊PID控制策略和侧倾力矩分配方案,以及执行机构逻辑门限值控制策略,并基于Matlab/Simulink、TruckSim和AMESim仿真软件,搭建了电液悬架系统主动抗侧倾控制策略联合仿真平台;对装配有电液悬架系统的车辆模型在极限工况下的抗侧倾性能进行仿真分析,并对车辆在随机路面激励输入下的馈能特性进行仿真分析。结果表明,装配该电液悬架的特种车辆具备较强的防侧翻能力,并具有较好的悬架运动能量回收潜力。     

发动机隔振系统振动固有特性的优化计算及影响因素分析

对发动机隔振系统振动固有特性进行了理论分析,引入了六自由度能量解耦理论,依托Matlab的矩阵运算能力,开发了发动机隔振系统优化设计软件,并利用该软件对系统进行了振动固有特性分析和能量解耦优化。考虑到悬置元件刚度的实际值与设计值可能存在一定偏差,因此针对某解耦度较高的系统,按照悬置元件各向刚度参数±20%的偏差范围,对系统进行仿真试验,研究了悬置元件刚度偏差对系统振动固有特性的影响,所得结论对隔振设计和悬置元件的工艺控制具有一定的指导意义。     

电磁馈能式悬架方案设计与节能分析

电磁馈能式悬架是一种能够回收汽车垂直振动能量的新型悬架系统.阐述了电磁馈能式悬架的工作原理、结构及设计方案,并建市了电磁馈能式悬架模型.运用CARSIM及MATLAB/SIMULINK等仿真软件,分析了电磁馈能式悬架的节能情况.结果表明,电磁馈能式悬架能够在一定程度上回收振动能量.经分析可知,结构阻尼、馈能元件阻尼器及充电电路性能是影响馈能元件能量回收效率的主要因素.