Hybrid neural network bushing model for vehicle dynamics simulation

Although the linear model was widely used for the bushing model in vehicle suspension systems, it could not express the nonlinear characteristics of bushing in terms of the amplitude and the frequency. An artificial neural network model was suggested to consider the hysteretic responses of bushings. This model, however, often diverges due to the uncertainties of the neural network under the unexpected excitation inputs. In this paper, a hybrid neural network bushing model combining linear and neural network is suggested. A linear model was employed to represent linear stiffness and damping effects, and the artificial neural network algorithm was adopted to take into account the hysteretic responses. A rubber test was performed to capture bushing characteristics, where sine excitation with different frequencies and amplitudes is applied. Random test results were used to update the weighting factors of the neural network model. It is proven that the proposed model has more robust characteristics than a simple neural network model under step excitation input. A full car simulation was carried out to verify the proposed bushing models. It was shown that the hybrid model results are almost identical to the linear model under several maneuvers. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Dr. Wan-Suk Yoo was born in 1954, and received B.S. degree from Seoul National University (1976), and got M.S. degree from KAIST (1978) and Ph.D. from the University of Iowa (1985). He is currently a full professor at the Pusan National University in Korea, where he joined since 1978. His major area is vehicle dynamics and flexible multibody dynamics. He became an ASME Fellow (2004), and currently serving as an associate editor for the ASME, J. of computational and nonlinear dynamics. He is also serving a contributing editor for the multibody system dynamics journal. He is serving as ISC chair for the ACMD2008, and a member at IFToMM TC for multibody dynamics. He is currently a vicepresident of the KSME (Korean Society of Mechanical Engineers).     

一种新型橡胶衬套理论模型及其参数识别

为了研究常用减振元件——橡胶衬套在减振方面的性能,建立了一种能准确描述其动态特性的理论模型。通过试验得到了橡胶衬套轴向的静、动态特性,对其频率相关性和振幅相关性进行了分析。首先,提出一种基于弹性单元、摩擦单元和若干个黏弹单元叠加的新型橡胶衬套模型;然后,根据试验结果进行参数识别;最后,通过比较得知,不同频率下衬套的动刚度和阻尼系数的仿真结果与试验结果规律一致,且最大误差分别只有5.99%和7.73%,满足工程应用的精度要求。     

Vehicle dynamic simulation including an artificial neural network bushing model

In this paper, a practical bushing model is proposed to improve the accuracy of the vehicle dynamic analysis The results of the nubber bushing are used to develop an empirical bushing model with an artificial neural network A back propagation algorithm is used to obtain the weighting factor of the neural network Since the output for a dynamic system depends on the histories of inputs and outputs, Narendra algorithm of ‘NARMAX’ form is employed to considet these effects A numerical example is earned out to verify the developed bushing model Then, a full car dynamic model with artificial neural network bushings is simulated to show the feasibility of the proposed bushing model     

不同活塞销孔衬套-活塞销摩擦副匹配性能研究

活塞销孔衬套-活塞销是柴油机重要的摩擦副之一,其匹配性能的优劣直接影响使用寿命和动力特性。为探讨不同制备工艺的活塞销孔衬套与柴油机在用活塞销的匹配性能,将分别采用挤压和旋压工艺制备的活塞销孔衬套,以及进口衬套分别与柴油机在用活塞销匹配,在摆动摩擦副摩擦磨损试验台进行承载、抗咬合和耐磨损性能试验。试验结果表明：制备工艺对摩擦副匹配性能具有一定的影响;从摩擦扭矩、摩擦温度、宏观形貌和磨损量4个方面分析,相同工况下挤压衬套承载极限、抗咬合性能和耐磨损性能均优于旋压衬套,具备对标进口衬套的能力,可为国内活塞销孔衬套的选配提供参考。     

Sensitivity of a vehicle ride to the suspension bushing characteristics

The sensitivity of the ride characteristics of a road vehicle to the mechanical characteristics of the bushings used in its suspension is discussed here. First, the development and computational implementation, on a multibody dynamics environment, of a constitutive relation to model bushing elements associated with mechanical joints is presented. Bushings are made of a rubber type of material, which presents a nonlinear and viscoelastic relationship between the forces and moments and their corresponding displacements and rotations. Suitable bushing models for vehicle multibody models must be accurate and computationally efficient, leading to more reliable models. The bushing is modeled in a multibody code as an arrangement of springs that penalize the motion between the bodies connected. In the methodology proposed here, a finite element model of the bushing is developed in the framework of a finite element (FE) code to obtain the curves of displacement/rotation versus force/moment for different loading cases. The basic ingredients of the multibody model are the same vectors and points relations used to define kinematic constraints in any multibody formulation. Spherical, cylindrical and revolute bushing joints are developed and implemented in this work, since the methodology is demonstrated through the ride over bumps, at different speeds, of two multibody models of a road vehicle: one with perfect kinematic joints, for the suspension sub-systems; the other with bushing joints, riding. Then, sensitivities of different vehicle kinematic responses to the characteristics of the bushings used in the suspension are evaluated, by using numerical sensitivities. Based on the sensitivity analysis, indications on how to modify the vehicle response by modifying the bushing characteristics are drawn. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Jorge A.C. Ambrósio received his Ph.D. degree from the University of Arizona in 1991, being currently Professor at the Mechanical Engineering Department of Instituto Superior Técnico at the Technical University of Lisbon, Portugal. He is the author of several books and a large number of papers in international journals in the areas of multibody dynamics, vehicle Dynamics, crashworthiness and biomechanics. He has been responsible for several international projects in railway dynamics, biomechanics and passive safety. Currently he is the Editor-in-Chief of Multibody System Dynamics and member of the editorial boards of several international journals.     

Evolution of Wear in a Two-Dimensional Bushing

A model for the evolution of wear for the shaft and bushing for a simple two-dimensional bushing system was developed under the assumptions of uniform contact pressure and constant applied load. A simple laboratory apparatus was constructed to test the model. Two experiments were run; one showed wear on the shaft only and the other showed wear on the bushing only. The results showed the predicted linear progression of wear.     

Zero-load stability of a rigid rotor supported on pressurized porous gas bearings

A theoretical and experimental investigation of stability characteristics of a rigid rotor mounted on externally expressurized gas-lubricated porous bearings in made. The hydrodynamic fluid film forces of an unloaded journal which undergoes steady whirl are obtained to find limits of the stable region. The results are compared with experimental data and with a similar solution using Galerkin's method. The effect of a feeding parameter, supply pressure, thickness of porous bushing and porosity of bushing material on stability characteristics is also investigated.     

船舶舵机负载模拟系统位置与力跟踪控制特性研究

舵机装置是用来改变船舶航行方向的执行机构，为了测试其操作性能和可靠性，缩短研制周期，节约研制成本，需要对舵机装置的工作载荷进行模拟，从而满足舵机装置的性能测试需求。舵机负载模拟系统是一种半实物仿真系统，主要用来对舵机装置进行负载模拟加载，模拟船舶在实际航行过程中舵机装置所受到的水动力载荷。建立舵机负载模拟系统的数学模型与AMESim仿真模型，重点研究加载系统的力跟踪闭环控制特性。     

汽车控制臂后衬套台架试验疲劳寿命分析

实现多轴工况下的橡胶部件的疲劳寿命预测具有重要意义,对橡胶衬套的台架疲劳试验寿命进行预测,研究和分析实现衬套多轴疲劳寿命预测的一些关键问题。进行衬套部件的台架疲劳试验,获得了部件的试验疲劳寿命。选定疲劳损伤模型,进行橡胶材料的疲劳寿命测试,拟合模型参数;使用有限元仿真和线性叠加法计算得到衬套在台架疲劳试验中的应力和应变响应;对衬套的台架试验疲劳寿命进行预测,分析损伤参数、载荷相位、线性叠加等因素对疲劳寿命的影响。结果表明,该文的材料疲劳试验方法和寿命预测方法能够较好地预测橡胶衬套台架疲劳寿命;对于台架试验工况,损伤参数对寿命影响不大,载荷的相位对寿命影响较大,线性叠加引起的误差不大。     

基于JFO边界条件的连杆衬套润滑特性理论分析

采用有限差分法求解基于JFO(Jakobsson-Floberg-Olsson)边界条件(即质量守恒边界)下的雷诺方程,推导出连杆衬套油膜压力分布、油膜厚度、油膜承载力、润滑油端泄量表达式;建立连杆衬套在贫油润滑状态下的油膜压力分布模型,分析载荷对连杆衬套轴心轨迹位置、最大油膜压力和最小油膜厚度的影响。结果表明:在不同曲轴转速下,连杆衬套的润滑特性具有相同的变化规律,且在柴油机做功行程上止点的附近区域的油膜端泄量大于供油量,导致油膜的完整性被破会,形成空穴发生边界摩擦,甚至干摩擦或者磨损;连杆衬套与活塞销的最佳相对间隙为0.025%~0.05%。     

Journal bearing housing design—A statistical study with FEM

When designing journal bearing housings for construction equipment, one goal is to get an even pressure distribution over the length of the bushing. This is to avoid excessive wear due to contact pressure peaks.A housing that is considered good, does not allow the pin to deflect and keeps the stresses low in the weld. To do this it must be stiff and this will lead to high contact pressures on the edges of the bushing, which is not preferable since wear is highly dependent on the contact pressure level.If the distribution of the contact pressure could be smoothed out over the bushing, the material might be used more efficiently. The normal way to do this is to crown the bushing to allow for pin deflection. However this leads to reduced area in contact. Another method to avoid high pressures in the bearing is to optimize the bearing housing for optimum stiffness.This paper describes one way to optimize journal bearing housings in regard to the contact pressure in the tribo-contact. A statistical approach was applied to a parameterized finite element model with contact elements. Three parameters were analyzed at different loads; set ring thickness, set ring width and fillet weld size.The contact pressure distributions were evaluated in two different ways to a single value to meet the statistical demand of measurable result. The results show that the set ring thickness and width are the parameters that influence most the contact pressure distribution. To reduce the maximum contact pressure the set ring thickness should be kept small.     

计入柱塞套弹性变形的柱塞副摩擦与密封特性分析

综合考虑径向柱塞泵柱塞副粗糙表面接触和弹性变形,建立混合润滑状态下柱塞副弹流润滑理论分析模型,并结合有限差分法与有限单元法,基于MATLAB和ANSYS开展联合仿真,分析不同入口压力及凸轮转速下柱塞副弹性变形及表面形貌对摩擦与密封特性的影响。结果表明：柱塞套弹性变形对柱塞副微凸体接触影响显著,且影响程度与入口压力及凸轮转速有直接关系;弹性变形及表面形貌均在一定程度上影响摩擦功耗及泄漏量且弹性变形的影响更大;柱塞副摩擦与密封特性对工作条件较为敏感,随着入口压力或凸轮转速的增大,摩擦功耗、压差流量与剪切流量均有不同程度的增加。     

衬套结构对篦齿密封封严性能的影响

为提高压气机级间篦齿密封封严性能,设计矩形开槽、梯形开槽、矩形挡环和梯形挡环4种衬套结构,数值研究不同压比和间隙下衬套结构对篦齿密封泄漏特性的影响,并与光滑衬套进行对比。结果表明：随压比增加,流体加速,密封泄漏量均增大,然而设置挡环衬套可直接阻碍壁面射流,其中梯形挡环可以引导射流回冲,加剧齿腔中湍流混乱程度,故泄漏量增速逐渐变缓;间隙相同时,挡环衬套密封效果最好,开槽衬套仅在最佳间隙值时才凸显其封严优势,而挡环衬套随间隙增加封严优势逐步放大。因此,高压比大间隙工况下,挡环衬套封严性能更好,其中梯形挡环更具优势。     

基于多体力学模型的车辆侧翻仿真研究

利用多体系统动力学ADAMS软件建立某轿车的整车多体仿真模型,考虑了悬架、转向系统空间机构的几何非线性特性以及轮胎、衬套等部件的非线性,模型准确的表达了整车的动态特性;对车辆侧翻多种工况进行了仿真研究,仿真结果可以准确的表达真实车辆的侧翻特性,为实车试验提供了参考。     

Comparison of different estimation techniques for biomass concentration in large scale yeast fermentation

In this study, previously developed five different state estimation methods are examined and compared for estimation of biomass concentrations at a production scale fed-batch bioprocess. These methods are i. estimation based on kinetic model of overflow metabolism; ii. estimation based on metabolic black-box model; iii. estimation based on observer; iv. estimation based on artificial neural network; v. estimation based on differential evaluation. Biomass concentrations are estimated from available measurements and compared with experimental data obtained from large scale fermentations. The advantages and disadvantages of the presented techniques are discussed with regard to accuracy, reproducibility, number of primary measurements required and adaptation to different working conditions. Among the various techniques, the metabolic black-box method seems to have advantages although the number of measurements required is more than that for the other methods. However, the required extra measurements are based on commonly employed instruments in an industrial environment. This method is used for developing a model based control of fed-batch yeast fermentations.     

基于虚拟试车场的轿车悬架耐久性强化试验仿真研究

汽车产品的耐久性是影响其竞争力的重要因素,同时其开发周期与成本迫切需要在产品概念设计阶段对其耐久性进行控制。针对轿车开发过程中传统悬架耐久性道路强化试验周期长费用高的缺点,以农安试车场各种耐久性强化路面为输入条件,应用虚拟试车场技术(Virtual proving ground,VPG)建立某轿车整车柔性虚拟试车场仿真模型,解决虚拟试车场技术运用中的轮胎模型、橡胶衬套刚度、路面模型和整车模型计算效率等关键技术,分析轿车悬架系统时间历程动应力响应,并与相同工况下的实车耐久性试验结果进行对比,仿真结果与测试结果时域和频域趋势基本一致,验证柔性虚拟试车场技术仿真的悬架系统动应力响应的有效性。在此基础上,实现开发过程中悬架系统耐久性的有效预报。     

Analysis of aerostatic porous journal bearings using the slip velocity boundary conditions

A theoretical analysis of the static characteristics of aerostatic porous journal bearings is presented using the slip velocity boundary condition at the interface of the lubricating film and porous surface of the bearing. With thin wall bearings, the pressure in the porous bushing is obtained in closed form and the modified Reynolds equation is solved numerically using the finite difference method. The load capacity and the mass rate of flow are expressed non-dimensionally and are calculated numerically for different operating conditions. Variation in $\text{W}\text{?}$ and $\text{G}\text{?}$ with the feeding parameter and other parameters is shown graphically. The effect of velocity slip on $\text{W}\text{?}$ and $\text{G}\text{?}$ for different operating conditions was studied. The theoretical results are compared with a similar available solution using a three-dimensional flow model in the bushing. There is near-perfect agreement.     

连杆衬套内表面磨损的正交试验研究

在连杆衬套内表面磨损的试验研究中,分别选取间隙值、载荷和转速作为试验因子。用正交试验法进行摩擦磨损试验,并用极差分析法分析了试验结果。结果表明：对连杆衬套内表面磨损影响主次顺序为转速、载荷、间隙值。从中得到了连杆衬套内表面最大磨损量和最小磨损量的工况。     

电磁阀的热物理场数值仿真与试验研究

以某型航空发动机控制系统上的电磁阀为研究对象，建立其流固耦合模型，开展热物理场数值仿真研究，对其不同工况下的热物理场特性进行分析。同时搭建试验系统进行试验验证，根据试验结果对仿真模型及参数进行优化迭代，并得出结论：在实际使用过程中，电磁阀的温升主要受环境温度、外加功率、内部结构及外部热交换条件的影响，电磁阀的热物理场数值仿真结果与试验数据的最大误差为7.0%,数值仿真模型准确度较高，能有效地预测电磁阀的温度场分布。该模型可指导电磁阀热设计，具有较高的实际工程应用价值。     

Thermal response simulation for tuning PID controllers in a 1016 mm guarded hot plate apparatus

A mathematical model has been developed and used to simulate the controlled thermal performance of a large guarded hot-plate apparatus. This highly specialized apparatus comprises three interdependent components whose temperatures are closely controlled in order to measure the thermal conductivity of insulation materials. The simulation model was used to investigate control strategies and derive controller gain parameters that are directly transferable to the actual instrument. The simulations take orders-of-magnitude less time to carry out when compared to traditional tuning methods based on operating the actual apparatus.The control system consists primarily of a PC-based PID control algorithm that regulates the output voltage of programmable power amplifiers. Feedback parameters in the form of controller gains are required for the three heating circuits. An objective is to determine an improved set of gains that meet temperature control criteria for testing insulation materials of interest.The analytical model is based on aggregated thermal capacity representations of the primary components and includes the same control algorithm as used in the actual hot-plate apparatus. The model, accounting for both thermal characteristics and temperature control, was validated by comparisons with test data.The tuning methodology used with the simulation model is described and results are presented. The resulting control algorithm and gain parameters have been used in the actual apparatus without modification during several years of testing materials over wide ranges of thermal conductivity, thickness, and insulation resistance values.