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.     

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.     

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。     

Damper Models for Heavy Vehicle Ride Dynamics

A laboratory rig for testing hydraulic dampers using the 'hardware-in-the-loop' method is described, and the accuracy of the test method is investigated. A mathematical model of a hydraulic shock absorber is then developed. The model is suitable for vehicle simulations and has seven parameters which can be determined by simple dynamic measurements on a test damper. The shock absorber model is validated under realistic operating conditions using the test rig, and the relative importance of various features of the model on the accuracy of vehicle simulations is investigated.     

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...     

Damper Models for Heavy Vehicle Ride Dynamics

SUMMARY

A laboratory rig for testing hydraulic dampers using the ‘hardware-in-the-loop’ method is described, and the accuracy of the test method is investigated. A mathematical model of a hydraulic shock absorber is then developed. The model is suitable for vehicle simulations and has seven parameters which can be determined by simple dynamic measurements on a test damper. The shock absorber model is validated under realistic operating conditions using the test rig, and the relative importance of various features of the model on the accuracy of vehicle simulations is investigated.     

电控气动式可调阻尼减振器的设计与应用

确定了电控气动式可调阻尼减振器在"软"、"硬"阻尼状态下的阻尼力设计目标.设计了以电磁阀和摆动气缸作为驱动机构的电控气动式可调阻尼减振器,通过仿真计算分析了该减振器的阻尼特性.研制了可调阻尼减振器样件并在试验台架上进行了性能测试.结果表明,除后减振器压缩阻力外.其余各项阻尼力试验值与仿真值的平均偏差小于7%,表明减振器的仿真模型有效.将该可调阻尼减振器装车进行的道路平顺性试验表明,与被动式减振器相比,采用可调阻尼减振器可使客车的行驶平顺性得到提高.     

麦弗逊式前悬架液力减振器阻尼特性仿真与试验

分析了某轿车麦弗逊式前悬架液力减振器的结构特点,建立了该减振器阻尼特性的数学模型,分别采用钱氏摄动法和有限元法计算减振器节流阀片的挠曲变形,通过仿真计算得到了相应的减振器阻尼特性,通过台架试验进行了减振器样件的阻尼性能测试。对比分析表明:仿真结果与试验结果基本一致,验证了减振器阻尼特性数学模型的有效性;根据有限元法计算的阀片变形所预测的减振器阻尼特性更接近试验值,研究结果有利于提高液力减振器阻尼特性的计算精度。     

Hybrid neural network model for history-dependent automotive shock absorbers

The method of numerical multi-body simulation is an often used and well-understood development tool in the automotive industry. In order to reproduce the ride comfort or handling behaviour of vehicles, mathematical models have to be built up. To achieve accurate simulation results, highly detailed component models are required. However, the formulation of appropriate physically-based model equations of complex automotive components (e.g. air springs, shock absorbers, rubber bearings, tyres, etc.) can be very difficult. To handle this, empirical modelling methods have been developed. Simple algebraic equations are used to describe complex system behaviour. This simplification is very effective, although it largely ignores the natural laws of mechanics and thermodynamics but is still capable to predict the component response. This article illustrates how to take advantage of this approach in numerical simulations. We describe the development of a hybrid automotive shock absorber model based on both spline and neural network (NN) approaches. By combining these different approaches, an accurate model is achieved without loss of variability. Non-isothermal laboratory force-displacement measurements of an automotive shock absorber are being used to estimate the parameters of the NN. As shown, the model replicates the measured data with sufficient accuracy, especially the hysteresis. Finally, we present a set of quarter-car simulations with a built-in hybrid NN shock absorber.     

半主动悬架磁流变液减振器研究

针对Passat B5轿车前悬架,开发了双筒滑阀式磁流变液减振器,提出了簧载质量的绝对速度及其与非簧载质量间的相对运动速度估计算法,利用实测悬架参数和磁流变液减振器的非线性阻尼力特性,建立了带磁流变液减振器的半主动悬架模型。沥青路面试验结果表明:相对于被动悬架,采用磁流变液半主动悬架后车辆平顺性改善大于10%。     

Kinematic and dynamic analysis of the McPherson suspension with a planar quarter-car model

McPherson suspension modelling poses a challenging problem due to its nonlinear asymmetric behaviour. The paper proposes a planar quarter-car analytical model that not only considers vertical motion of the sprung mass (chassis) but also: (i) rotation and translation for the unsprung mass (wheel assembly), (ii) wheel mass and its inertia moment about the longitudinal axis, and (iii) tyre damping and lateral deflection. This kinematic–dynamic model offers a solution to two important shortcomings of the conventional quarter-car model: it accounts for geometry and for tyre modelling. The paper offers a systematic development of the planar model as well as the complete set of mathematical equations. This analytical model can be suitable for fast computation in hardware-in-the-loop applications. Furthermore, a reproducible Simulink implementation is given. The model has been compared with a realistic Adams/View simulation to analyse dynamic behaviour for the jounce and rebound motion of the wheel and two relevant kinematic parameters: camber angle and track width variation.     

Heavy-duty vehicle modelling and longitudinal control

This paper addresses modelling, longitudinal control design and implementation for heavy-duty vehicles (HDVs). The challenging problems here are: (a) an HDV is mass dominant with low power to mass ratio; (b) They possess large actuator delay and actuator saturation. To reduce model mismatch, it is necessary to obtain a nonlinear model which is as simple as the control design method can handle and as complicated as necessary to capture the intrinsic vehicle dynamics. A second order nonlinear vehicle body dynamical model is adopted, which is feedback linearizable. Beside the vehicle dynamics, other main dynamical components along the power-train and drive-train are also modelled, which include turbocharged diesel engine, torque converter, transmission, transmission retarder, pneumatic brake and tyre. The braking system is the most challenging part for control design, which contains three parts: Jake (engine compression) brake, air brake and transmission retarder. The modelling for each is provided. The use of engine braking effect is new complementary to Jake (compression) brake for longitudinal control, which is united with Jake brake in modelling. The control structure can be divided into upper level and lower level. Upper level control uses sliding mode control to generate the desired torque from the desired vehicle acceleration. Lower level control is divided into two branches: (a) engine control: from positive desired torque to desired fuel rate (engine control) using a static engine mapping which basically captures the intrinsic dynamic performance of the turbo-charged diesel engine; (b) brake control: from desired negative torque to generate Jake brake cylinder number to be activated and ON/OFF time periods, applied pneumatic brake pressure and applied voltage of transmission retarder. Test results are also reported.     

Heavy-duty vehicle modelling and longitudinal control

This paper addresses modelling, longitudinal control design and implementation for heavy-duty vehicles (HDVs). The challenging problems here are: (a) an HDV is mass dominant with low power to mass ratio; (b) They possess large actuator delay and actuator saturation. To reduce model mismatch, it is necessary to obtain a nonlinear model which is as simple as the control design method can handle and as complicated as necessary to capture the intrinsic vehicle dynamics. A second order nonlinear vehicle body dynamical model is adopted, which is feedback linearizable. Beside the vehicle dynamics, other main dynamical components along the power-train and drive-train are also modelled, which include turbocharged diesel engine, torque converter, transmission, transmission retarder, pneumatic brake and tyre. The braking system is the most challenging part for control design, which contains three parts: Jake (engine compression) brake, air brake and transmission retarder. The modelling for each is provided. The use of engine braking effect is new complementary to Jake (compression) brake for longitudinal control, which is united with Jake brake in modelling. The control structure can be divided into upper level and lower level. Upper level control uses sliding mode control to generate the desired torque from the desired vehicle acceleration. Lower level control is divided into two branches: (a) engine control: from positive desired torque to desired fuel rate (engine control) using a static engine mapping which basically captures the intrinsic dynamic performance of the turbo-charged diesel engine; (b) brake control: from desired negative torque to generate Jake brake cylinder number to be activated and ON/OFF time periods, applied pneumatic brake pressure and applied voltage of transmission retarder. Test results are also reported.     

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.     

轻型货车车架纵梁异常开裂原因的分析

针对轻型货车在行驶过程中纵梁撕裂的问题，应用有限元分析软件对车架的强度进行了分析，并通过实验的方法证明了计算模型的正确性。分析结果表明：减震器支架在车辆行驶过程中对纵梁的冲击导致了纵梁的开裂。根据实际工艺要求，提出了改进措施，使得开裂区域的应力值降低了61％。     

Vehicle handling dynamics modelling by a data-driven identification method

Modelling of vehicle handling dynamics has received a renewed attention in recent years. Different from traditional vehicle modelling, a novel data-driven identification method for vehicle handling dynamics is proposed, which can avoid the problems of the under-modelling and parameter uncertainties in the first-principle modelling process. By first-order Taylor expansion, the nonlinear vehicle system can be linearised as a slowly linear time-varying system with fourth-order. In order to identify the derived identifiable model structure, a recursive subspace method is presented. Derived by optimal version of predictor-based subspace identification (PBSID_opt) and projection approximation subspace tracking (PAST), the identification method is numerical stability and gives an unbiased estimation for the closed-loop system. Based on standard road tests, the proposed modelling method is proven effective and the obtained model has good predictive ability. Additionally, it is noted that the model obtained from the initial phase of straight driving is just a mathematical model to describe the relationship between input and output. And when the vehicle is steering, the model can converge to a stable phase quickly and represent vehicle dynamic performance.     

An Analytical and Experimental Investigation of the Driver-Seat-Suspension System

SUMMARY

Vertical seat-suspension systems are characterized by a generalized two- degree-of-freedom model incorporating nonlinearities due to shock absorber damping, linkage friction and bump stops. The analytical model is validated using the results obtained from laboratory tests performed under sinusoidal excitations in the 0.5-8.0 Hz frequency range. Human body models of varying complexities, derived from the mechanical impedance data, are discussed and integrated to the nonlinear seat-suspension model to derive a coupled driver- seat-suspension model. Nonlinear analytical models are expressed by their linear equivalent models using a local equivalent linearization technique based on energy similarity. The vibration attenuation performance characteristics of the seat-suspension and driver-seat-suspension models are investigated for deterministic and random cab floor excitations. The results of the study revealed that the seated human body contributes considerably to the overall ride performance.     

汽车减震器变硬现象原因分析

汽车减震器通过长时间的使用以后,减震器变软或变硬。本文件探讨了减振器硬度的原因:在进行耐久性测试之后,从减振器油中提取减振器油,以分析减振油制剂性能的变化。为了加速减振车架和车身的振动,以提高车辆的可读性("舒适性"),在大多数车辆的悬挂系统内装有减震器的车辆减震器也称作"悬挂",弹簧和减震器的化合物,缓冲器不用来承受车身的重量,但是,当弹簧吸收弹簧时,可以容纳冲击和吸收表面冲击的能量。反弹弹簧用于缓冲冲击,将"高能量二次冲击"转换为"低能量多次冲击",而减震器则逐渐减少"多重低能量冲击"。     

Yaw damper modelling and its influence on railway dynamic stability

This paper deals with the modelling of yaw dampers and determining the influence of the modelling of this component on the results obtained when predicting the dynamic stability of a vehicle. The first part of the work analyses the influence of the yaw damper characteristics on railway dynamic stability. Following this, a physical model of the damper is developed which allows its performance to be reproduced accurately in the whole range of operating conditions the damper is envisaged to operate in. Once obtained, it was found that the computational cost of the model was relatively high. Therefore, a simplified model has been developed. The simplified model allows obtaining accurate results without excessively increasing the time required to perform the simulations. Analysing the results obtained with this model, it has been concluded that with respect to previous model based on conventional approaches, it improves the accuracy of dynamic calculation for the stability assessment. Also, it has been found that the accurate modelling of the yaw damper is critical when dealing with the vehicle's dynamic performance. In the last part of the paper, a special type of yaw damper was studied as well as its effect on the dynamic behaviour of the vehicle.     

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.