Full vehicle simulation using thermomechanically coupled hybrid neural network shock absorber model

In the case of full vehicle models, the technique of multi-body simulation (MBS) is frequently used to study their highly non-linear dynamic behaviour. Many non-linearities in vehicle models are induced by force elements like springs, shock absorbers, bushings and tires. Commonly, spline functions are used to represent the force responses of these components. If the non-linear relationships are more complicated, the spline approximations are no more accurate. An alternative approach is based on empirical neural networks which are based on the mathematical approximation of measured data. It is well known that neural networks are able to represent and predict complex component responses accurately. The aim of this paper is to perform a dynamic full vehicle simulation using a thermomechanically coupled hybrid neural network shock absorber model. In this shock absorber model, the spline approach is combined with a temperature-dependent neural network. Based on a displacement-controlled excitation on a four post test rig in the ADAMS/Car MBS software, a rugged test track is simulated. In this way, the front and rear shock absorbers are dynamically loaded with comfort-relevant frequencies in the range of 0.75–30 Hz and velocity amplitudes up to 2 m/s. By the simulation, stability of the hybrid neural network model is demonstrated. Furthermore, the damping force, the vertical acceleration of the chassis and the required simulation times are compared. The standard spline approach is used as a reference.     

Full vehicle simulation using thermomechanically coupled hybrid neural network shock absorber model

In the case of full vehicle models, the technique of multi-body simulation (MBS) is frequently used to study their highly non-linear dynamic behaviour. Many non-linearities in vehicle models are induced by force elements like springs, shock absorbers, bushings and tires. Commonly, spline functions are used to represent the force responses of these components. If the non-linear relationships are more complicated, the spline approximations are no more accurate. An alternative approach is based on empirical neural networks which are based on the mathematical approximation of measured data. It is well known that neural networks are able to represent and predict complex component responses accurately. The aim of this paper is to perform a dynamic full vehicle simulation using a thermomechanically coupled hybrid neural network shock absorber model. In this shock absorber model, the spline approach is combined with a temperature-dependent neural network. Based on a displacement-controlled excitation on a four post test rig in the ADAMS/Car MBS software, a rugged test track is simulated. In this way, the front and rear shock absorbers are dynamically loaded with comfort-relevant frequencies in the range of 0.75-30 Hz and velocity amplitudes up to 2 m/s. By the simulation, stability of the hybrid neural network model is demonstrated. Furthermore, the damping force, the vertical acceleration of the chassis and the required simulation times are compared. The standard spline approach is used as a reference.     

Simulation Tools,Modelling and Identification,for an Automotive Shock Absorber in the Context of Vehicle Dynamics

For purpose of simulation of vehicle dynamics, a physical model of an automotive shock absorber has been developed and implemented in several software packages for multibody simulations. In the present paper, the damper model structure is shortly elaborated together with some measurement and estimation techniques to retrieve the model parameters, possibly from dynamometer measurements only. These techniques are illustrated on a shock absorber normally used on the front suspension of a BMW series 7.     

Simulation Tools, Modelling and Identification, for an Automotive Shock Absorber in the Context of Vehicle Dynamics

For purpose of simulation of vehicle dynamics, a physical model of an automotive shock absorber has been developed and implemented in several software packages for multibody simulations. In the present paper, the damper model structure is shortly elaborated together with some measurement and estimation techniques to retrieve the model parameters, possibly from dynamometer measurements only. These techniques are illustrated on a shock absorber normally used on the front suspension of a BMW series 7.     

Efficient empirical modelling of a high-performance shock absorber for vehicle dynamics studies

This paper develops an intuitive empirical nonlinear dynamic shock absorber model for simulation studies. Unlike other existing dynamic shock absorber models, it does not suffer from the complexity of modelling complex physical behaviour, or the inefficiencies of unstructured black-box modelling. The model consists of an algebraic backbone, which is a function of velocity alone, and a nonlinear low-pass filter, which has been designed based on the observation that the damper can respond more quickly at higher velocities. Due to the simplicity of the model, it can be fitted with data and evaluated quickly. The model was fitted using shock dynamometer test data using a random shock position command. The completed model is then validated using random, sine wave, and bump test data. This analysis shows the strengths and weaknesses of the model and suggests areas for future development.     

Evaluation of Shock Absorber Models

A non exhaustive overview of shock absorber models is presented. The ability of the models to match experimental data is emphasized. Two physical models are presented that are able to extract the internal valve parameters from data without hysteresis. In order to implement a model that copes with hysteresis, most models require the numerical solution to a set of nonlinear differential equations. The use of an alternative restoring force method can get round the time consuming iterative simulation and identification routines. The alternative nonparametric method models the force as a function of velocity and acceleration. The theoretical relevance of the model is studied.     

A Thermomechanically Coupled Model for Automotive Shock Absorbers: Theory, Experiments and Vehicle Simulations on Test Tracks

In the development of cars numerical simulation plays a more and more important role. A method commonly used in this context is based on the formalism of multibody dynamics. In this approach a vehicle is described as a system of rigid bodies connected by joints, bushings, springs and dampers. For the purpose of estimating the time-dependent dynamical loads when riding, for example, over potholes or other obstacles we need enhanced models representing the mechanical behavior of the shock absorbers. A model of this type should describe the nonlinear rate dependence of the force in combination with friction effects and thermomechanical coupling phenomena. Due to the dissipation of energy the temperature of the shock absorber increases and influences its damping behavior. When riding over long rugged test tracks these effects are strongly pronounced. Thus we develop a thermomechanical model representing all these phenomena with good approximation and being compatible with the natural laws of thermodynamics. To validate the theory, we investigate the thermomechanical behavior of two automotive shock absorbers in detail. We measure the velocity dependence of the force under different temperature levels as well as the dissipative change in the temperature during cyclic excitations. Finally we carry out a vehicle test on a rugged test track and record the temperature of the front and rear dampers. As we show, the model describes all phenomena with sufficient approximation, especially the evolution of temperature.     

On the performance of rheological shock absorber models in full vehicle simulation

A comparative study of the performance of three rheological automotive shock absorber models as well as of an extended force-velocity relation in full vehicle simulation is performed. Simulation results for both the shock absorber test rig and a full vehicle crossing a single obstacle are compared with measured data. While the gain of accuracy by the extended force-velocity relation is marginal, the rheological models in general yield a noticeable improvement, which, however, in full vehicle simulation is less significant than in test rig simulation. Among the rheological models studied here, the one consisting of a nonlinear spring-dashpot element with an element modelling friction by a continuous transition from the compression to the extension range in parallel and a quadratic approximation of the static gas force exhibits the best global performance.     

A Thermomechanically Coupled Model for Automotive Shock Absorbers: Theory,Experiments and Vehicle Simulations on Test Tracks

In the development of cars numerical simulation plays a more and more important role. A method commonly used in this context is based on the formalism of multibody dynamics. In this approach a vehicle is described as a system of rigid bodies connected by joints, bushings, springs and dampers. For the purpose of estimating the time-dependent dynamical loads when riding, for example, over potholes or other obstacles we need enhanced models representing the mechanical behavior of the shock absorbers. A model of this type should describe the nonlinear rate dependence of the force in combination with friction effects and thermomechanical coupling phenomena. Due to the dissipation of energy the temperature of the shock absorber increases and influences its damping behavior. When riding over long rugged test tracks these effects are strongly pronounced. Thus we develop a thermomechanical model representing all these phenomena with good approximation and being compatible with the natural laws of thermodynamics. To validate the theory, we investigate the thermomechanical behavior of two automotive shock absorbers in detail. We measure the velocity dependence of the force under different temperature levels as well as the dissipative change in the temperature during cyclic excitations. Finally we carry out a vehicle test on a rugged test track and record the temperature of the front and rear dampers. As we show, the model describes all phenomena with sufficient approximation, especially the evolution of temperature.     

An insight into linear quarter car model accuracy

The linear quarter car model is the most widely used suspension system model. A number of authors expressed doubts about the accuracy of the linear quarter car model in predicting the movement of a complex nonlinear suspension system. In this investigation, a quarter car rig, designed to mimic the popular MacPherson strut suspension system, is subject to narrowband excitation at a range of frequencies using a motor driven cam. Linear and nonlinear quarter car simulations of the rig are developed. Both isolated and operational testing techniques are used to characterise the individual suspension system components. Simulations carried out using the linear and nonlinear models are compared to measured data from the suspension test rig at selected excitation frequencies. Results show that the linear quarter car model provides a reasonable approximation of unsprung mass acceleration but significantly overpredicts sprung mass acceleration magnitude. The nonlinear simulation, featuring a trilinear shock absorber model and nonlinear tyre, produces results which are significantly more accurate than linear simulation results. The effect of tyre damping on the nonlinear model is also investigated for narrowband excitation. It is found to reduce the magnitude of unsprung mass acceleration peaks and contribute to an overall improvement in simulation accuracy.     

On the performance of rheological shock absorber models in full vehicle simulation

A comparative study of the performance of three rheological automotive shock absorber models as well as of an extended force–velocity relation in full vehicle simulation is performed. Simulation results for both the shock absorber test rig and a full vehicle crossing a single obstacle are compared with measured data. While the gain of accuracy by the extended force–velocity relation is marginal, the rheological models in general yield a noticeable improvement, which, however, in full vehicle simulation is less significant than in test rig simulation. Among the rheological models studied here, the one consisting of a nonlinear spring–dashpot element with an element modelling friction by a continuous transition from the compression to the extension range in parallel and a quadratic approximation of the static gas force exhibits the best global performance.     

基于神经网络的汽车磁流变减振器非参数化建模

结合汽车用减振器的工作特点,按照国产某微型轿车后悬架的技术要求,设计了基于混合工作模式的单出杆单筒磁流变减振器,并进行了实物样品研制。根据流体力学理论,建立混合工作模式下磁流变减振器计算模型,并对磁流变减振器的阻尼力、动态响应时间及其影响因素进行了理论分析。对设计的磁流变减振器进行台架动态特性测试,试验结果表明：单出杆...     

采用电流变阻尼器汽车悬架的半主动控制研究

采用电流变阻尼器作为汽车悬架系统的减振器，应用最优控制策略，设计了汽车悬架的半主动控制系统。大量仿真实验表明，采用电流变阻尼器的半主动控制悬架系统有效地改善了汽车驾驶平顺性和乘坐舒适性。     

液压减振器非线性动态仿真和试验

本文建立复杂的减振器台架试验动力学模型,并应用多体系统动力学软件ADAMS开发出双筒液压减振器虚拟样机,进行数值仿真。在虚拟样机中采用的不对称非线性迟滞环足由速度外特性试验曲线拟合而得,突破了常规减振器建模中的速度外特性不对称双线性化模型。比较表明,虚拟样机动态仿真与台架试验结果基本相符。该样机可为优化设计和整车性能匹配提供设计平台。     

车用减振器的外特性建模与仿真

针对某轿车的弹性阀片和弹簧结合型减振器的结构形式，建立了减振器复原行程开阀前、开阀后及压缩行程的阻尼力力学模型，推导出了减振器阻尼力的计算公式，并通过计算机仿真得出该轿车减振器的模拟工作特性。计算机仿真和生产实践证明，所建立的数学模型是正确的，计算方法也符合实际要求。     

汽车悬架减振器不解体测试方法的研究

通过建立系统的数学模型和相应的参数算法，将系统频响函数拟合技术应用到汽车减振器测试台的开发中。提出了一种悬架减振器不解体测试的新方法、主动激振测试台的结构以及合理评价减振器性能的指标。     

基于混合编程技术的可调阻尼减振器性能仿真与试验

建立了分体式充气可调减振器阻尼特性数学模型,运用混合编程方法开发了该减振器阻尼特性的仿真分析软件。利用C Builder语言完成了应用程序模块和用户界面的设计,通过调用MATLAB中的数学函数库和图形函数库,实现了仿真结果的图形绘制功能。运用所开发的仿真软件计算了减振器的阻尼特性,并进行了减振器性能台架试验,仿真结果与试验结果基本一致,从而验证了减振器模型和仿真系统的有效性。     

汽车悬架系统磁流变减振器的数学模型及其试验研究

基于磁流变减振器的汽车悬架系统具有明显的滞后非线性,系统中的非线性阻尼和非线性刚度等对其动力学行为产生了很大的影响。影响汽车平顺性的主要因素是车身的垂直振动。为了描述这种振动,建立了汽车悬架系统的力学模型及其动力学方程,并结合阻尼特性试验,利用不同的数学模型描述了磁流变减振器的非线性滞后特性和饱和特性。     

Investigation of Cavitation Process in Monotube Shock Absorber

The paper investigates cavitation effect which negatively influences the performance of a monotube shock absorber of road vehicle (passenger car). For better understanding of this phenomena, three physical models of shim stack valves are analyzed. Validation results allowed selecting the most appropriate valve model in presence of cavitation processes. A mathematical model of monotube damper with consideration of fluid compressibility and cavitation phenomena is developed. Simulation results are validated by experimental data obtained on hydraulic test rig. Based on the selected approach, a simplified method suitable for assessment of cavitation processes in automotive monotube shock absorbers is proposed. After investigation it is found that damping force when cavitation occurs mainly depends on the initial pressure and absorber inner diameter.     

一种新型汽车减振器优化设计方法研究

在对磁流变液减振器理论模型进行分析的基础上,确定了影响磁流变液减振器性能的结构参数。将磁流变液的非线性磁特性与非牛顿流体力学性能相结合,建立了以降低磁流变液减振器响应时间常数、增加其调节比为目标函数的优化模型。根据优化结果,研制了一种新型车用磁流变液减振器,并进行了验证试验。