Performance analysis of air suspension system of heavy truck with semi-active fuzzy control

In order to analyze and evaluate the performance of the air suspension system of heavy trucks with semi-active fuzzy control, a three-dimensional nonlinear dynamical model of a typical heavy truck with 16-DOF（degree of freedom） is established based on Matlab/Simulink software. The weighted root-mean-square（RMS） acceleration responses of the vertical driver ＇s seat, the pitch and roll angle of the cab, and the dynamic load coefficient（DLC） are chosen as objective functions, and the air suspension system is optimized and analyzed by the semi-active fuzzy control algorithm when vehicles operate under different operation conditions. The results show that the influence of the roll angle of the cab on the heavy truck ride comfort is clear when vehicles move on the road surface conditions of the ISO level D and ISO level E at a velocity over 27.5 m/s. The weighted RMS acceleration responses of vertical driver＇ s seat, the pitch and roll angle of the cab are decreased by 24%, 30% and 25%, respectively,when vehicles move on the road surface condition of the ISO level B at a velocity of 20 m/s. The value of the DLC also significantly decreases when vehicles operate under different operation conditions. Particularly, the DLC value of the tractor driver axle is greatly reduced by 27.4% when the vehicle operates under a vehicle fully-loaded condition on the road surface condition of ISO level B at a velocity of 27.5 m/s.

Hierarchical Control of Ride Height System for Electronically Controlled Air Suspension Based on Variable Structure and Fuzzy Control Theory

The current research of air suspension mainly focuses on the characteristics and design of the air spring. In fact, electronically controlled air suspension （ECAS） has excellent performance in flexible height adjustment during different driving conditions. However, the nonlinearity of the ride height adjusting system and the uneven distribution of payload affect the control accuracy of ride height and the body attitude. Firstly, the three-point measurement system of three height sensors is used to establish the mathematical model of the ride height adjusting system. The decentralized control of ride height and the centralized control of body attitude are presented to design the ride height control system for ECAS. The exact feedback linearization method is adopted for the nonlinear mathematical model of the ride height system. Secondly, according to the hierarchical control theory, the variable structure control （VSC） technique is used to design a controller that is able to adjust the ride height for the quarter-vehicle anywhere, and each quarter-vehicle height control system is independent. Meanwhile, the three-point height signals obtained by three height sensors are tracked to calculate the body pitch and roll attitude over time, and then by calculating the deviation of pitch and roll and its rates, the height control correction is reassigned based on the fuzzy algorithm. Finally, to verify the effectiveness and performance of the proposed combined control strategy, a validating test of ride height control system with and without road disturbance is carried out. Testing results show that the height adjusting time of both lifting and lowering is over 5 s, and the pitch angle and the roll angle of body attitude are less than 0.15°. This research proposes a hierarchical control method that can guarantee the attitude stability, as well as satisfy the ride height tracking system.

Fuzzy Sliding Mode Control for the Vehicle Height and Leveling Adjustment System of an Electronic Air Suspension

The accurate control for the vehicle height and leveling adjustment system of an electronic air suspension(EAS) still is a challenging problem that has not been effectively solved in prior researches. This paper proposes a new adaptive controller to control the vehicle height and to adjust the roll and pitch angles of the vehicle body(leveling control) during the vehicle height adjustment procedures by an EAS system. A nonlinear mechanism model of the full?car vehicle height adjustment system is established to reflect the system dynamic behaviors and to derive the system optimal control law. To deal with the nonlinear characters in the vehicle height and leveling adjustment processes, the nonlinear system model is globally linearized through the state feedback method. On this basis, a fuzzy sliding mode controller(FSMC) is designed to improve the control accuracy of the vehicle height adjustment and to reduce the peak values of the roll and pitch angles of the vehicle body. To verify the effectiveness of the proposed control method more accurately, the full?car EAS system model programmed using AMESim is also given. Then, the co?simulation study of the FSMC performance can be conducted. Finally, actual vehicle tests are performed with a city bus, and the test results illustrate that the vehicle height adjustment performance is effectively guaranteed by the FSMC, and the peak values of the roll and pitch angles of the vehicle body during the vehicle height adjustment procedures are also reduced significantly. This research proposes an effective control methodology for the vehicle height and leveling adjustment system of an EAS, which provides a favorable control performance for the system.

A Hybrid Approach to Modeling and Control of Vehicle Height for Electronically Controlled Air Suspension

The control problems associated with vehicle height adjustment of electronically controlled air suspension （ECAS） still pose theoretical challenges for researchers, which manifest themselves in the publications on this subject over the last years. This paper deals with modeling and control of a vehicle height adjustment system for ECAS, which is an example of a hybrid dynamical system due to the coexistence and coupling of continuous variables and discrete events. A mixed logical dynamical （MLD） modeling approach is chosen for capturing enough details of the vehicle height adjustment process. The hybrid dynamic model is constructed on the basis of some assumptions and piecewise linear approximation for components nonlinearities. Then, the on-off statuses of solenoid valves and the piecewise approximation process are described by propositional logic, and the hybrid system is transformed into the set of linear mixed-integer equalities and inequalities, denoted as MLD model, automatically by HYSDEL. Using this model, a hybrid model predictive controller （HMPC） is tuned based on online mixed-integer quadratic optimization （MIQP）. Two different scenarios are considered in the simulation, whose results verify the height adjustment effectiveness of the proposed approach. Explicit solutions of the controller are computed to control the vehicle height adjustment system in realtime using an offline multi-parametric programming technology （MPT）, thus convert the controller into an equivalent explicit piecewise affine form. Finally, bench experiments for vehicle height lifting, holding and lowering procedures are conducted, which demonstrate that the HMPC can adjust the vehicle height by controlling the on-off statuses of solenoid valves directly. This research proposes a new modeling and control method for vehicle height adjustment of ECAS, which leads to a closed-loop system with favorable dynamical properties.

Life Prediction Based on Transient Dynamics Analysis of Van Semi-trailer with Air Suspension System

The early fatigue damage in the van-body of the semi-trailer is often caused by the unique mechanical characteristics and the dynamic impact of the loads.The traditional finite element method with static strength analysis cannot support the fatigue design of van-body;thus,the dynamics analysis should be adopted for the endurance performance.The accurate dynamics model to describe the transient impacts of all kinds of uneven road and the proper system transfer functions to calculate the load transfer effects from tire to van-body are two critical factors for transient dynamics analysis.In order to evaluate the dynamic performance,the dynamics model of the trailer with the air suspension is brought forward.Then the analysis method of the power spectral density （PSD） is set up to study the transient responses of the road dynamic impacts.The transient responses transferred from axles to van-body are calculated,such as dynamic stress,dynamic RMS acceleration,and dynamic load factors.Based on the above dynamic responses,the fatigue life of van-body is predicted with the finite element analysis （FEA） method.Applying the test parameters of the trailer with air suspension,the simulation system with Matlab/Simulink is constructed to describe the dynamic responses of the impacts of the tested PSD of the vehicle axles,and then the fatigue life is predicted with FEA method.The simulated results show that the vibration level of the van-body with air suspension is reduced and the fatigue life is improved.The real vehicle tests on different roads are carried out,and the test results validate the accuracy of the simulation system.The proposed fatigue life prediction method is effective for the virtual design of auto-body.

Buildup and simulation of a truck model with rear air suspension using leaf spring as guiding rod

A new kind of commercial truck is presented, which has rear air suspension using leaf spring as guiding rod instead of original leaf spring. ADAMS/Car is used as a tool to build the whole truck model. The designed truck＇s constant-radius cornering analysis and its ride performance simulation analysis under B class random road condition are carried out according to national experimental method standards. Compared the simulation results with the field test results indicate that performance index of the designed air suspension truck＇ s constant-radius cornering and its ride performance meets the design requirements and reaches its prospective target. And resuhs from simulation are similar to those from tests in value and trend, which indicates the virtual prototype is correct. The model can be used further to opti,nize suspension parameters and do some design work on the control system of air suspension.

Uncertainty Analysis and Optimization of Quasi-Zero Stifness Air Suspension Based on Polynomial Chaos Method

To improve the vibration isolation performance of suspensions,various new structural forms of suspensions have been proposed.However,there is uncertainty in these new structure suspensions,so the deterministic research cannot refect the performance of the suspension under actual operating conditions.In this paper,a quasi-zero stifness isolator is used in automotive suspensions to form a new suspension−quasi-zero stifness air suspension(QZSAS).Due to the strong nonlinearity and structural complexity of quasi-zero stifness suspensions,changes in structural parameters may cause dramatic changes in suspension performance,so it is of practical importance to study the efect of structural parameter uncertainty on the suspension performance.In order to solve this problem,three suspension structural parameters d_(0),L_(0) and Pc_(0) are selected as random variables,and the polynomial chaos expansion(PCE)theory is used to solve the suspension performance parameters.The sensitivity of the performance parameters to diferent structural parameters was discussed and analyzed in the frequency domain.Furthermore,a multi-objective optimization of the structural parameters d_(0),L_(0) and Pc_(0) of QZSAS was performed with the mean and variance of the root-mean-square(RMS)acceleration values as the optimization objectives.The optimization results show that there is an improvement of about 8%−1_(0)%in the mean value and about 4_(0)%−55%in the standard deviation of acceleration(RMS)values.This paper verifes the feasibility of the PCE method for solving the uncertainty problem of complex nonlinear systems,which provide a reference for the future structural design and optimization of such suspension systems.

Design, Development and Testing of an Air Damper to Control the Resonant Response of a SDOF Quarter-Car Suspension System

An air damper possesses the advantages that there are no long term changes in the damping properties, there is no dependence on working temperature and additionally, it has less manufacturing and maintenance costs. As such, an air damper has been designed and developed based on the Maxwell type model concept in the approach of Nishihara and Asami [1]. The cylinder-piston and air-tank type damper characteristics such as air damping ratio and air spring rate have been studied by changing the length and diameter of the capillary pipe between the air cylinder and the air tank, operating air pressure and the air tank volume. A SDOF quarter-car vehicle suspension system using the developed air enclosed cylinder-piston and air-tank type damper has been analyzed for its motion transmissibility characteristics. Optimal values of the air damping ratio at various values of air spring rate have been determined for minimum motion transmissibility of the sprung mass. An experimental setup has been developed for SDOF quarter-car suspension system model using the developed air enclosed cylinder-piston and air-tank type damper to determine the motion transmissibility characteristics of the sprung mass. An attendant air pressure control system has been designed to vary air damping in the developed air damper. The results of the theoretical analysis have been compared with the experimental analysis.

Applying machine learning for cars’semi-active air suspension under soft and rigid roads

To improve the ride quality and enhance the control efficiency of cars’semi-active air suspensions(SASs)under various surfaces of soft and rigid roads,a machine learning(ML)method is proposed based on the optimized rules of the fuzzy control(FC)method and car dynamic model for application in SASs.The root-mean-square(RMS)acceleration of the driver’s seat and car’s pitch angle are chosen as the objective functions.The results indicate that a soft surface obviously influences a car’s ride quality,particularly when it is traveling at a high-velocity range of over 72 km/h.Using the ML method,the car’s ride quality is improved as compared to those of FC and without control under different simulation conditions.In particular,compared with those cars without control,the RMS acceleration of the driver’s seat and car’s pitch angle using the ML method are respectively reduced by 30.20% and 19.95% on the soft road and 34.36% and 21.66% on the rigid road.In addition,to optimize the ML efficiency,its learning data need to be updated under all various operating conditions of cars.

Numerical simulation of high temperature air combustion in aluminum hydroxide gas suspension calcinations

The high temperature air combustion(HiTAC) process in gas suspension calcinations(GSC) was studied by using a CFD software FLUENT that can simulate the three-dimensional physical model of GSC with the k-epsilon turbulent viscous model, PDF non-premixed combustion species model, P1 radiation model, thermal and prompt NO pollution model. The simulation vividly describes the distributions of the temperature, velocity and consistency fields. Finally, the optimal operation conditions and igniter configuration of particular fuel combustion are obtained by analyzing and comparing the simulation results. And the emission quantity of NOx, CO and CO2 deduced from computation can play a role as reference. These optimal and estimated values are beneficial to practical operation.

Kinematic characterization and optimization of vehicle front-suspension design based on ADAMS

To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random excitations of the test platforms of respectively the left and the right wheels according to actual running conditions of a vehicle, and explored the changing patterns of the kinematic characteristic parameters in the process of suspension motion. The irrationality of the suspension guiding mechanism design was pointed out through simulation and analysis, and the existent problems of the guiding mechanism were optimized and calculated. The results show that all the front-wheel alignment parameters, including the camber, the toe, the caster and the inclination, only slightly change within corresponding allowable ranges in design before and after optimization. The optimization reduces the variation of the wheel-center distance from 47.01 mm to a change of 8.28 mm within the allowable range of ?10 mm to 10 mm, promising an improvement of the vehicle steering stability. The optimization also confines the front-wheel sideways slippage to a much smaller change of 2.23 mm; this helps to greatly reduce the wear of tires and assure the straight running stability of the vehicle.

基于分数阶的空气弹簧建模及电动汽车主动悬架控制研究

电控空气悬架系统(electrically controlled air suspension, ECAS)具有调节悬架刚度和车身高度的功能,可有效改善车辆乘坐舒适性和操纵稳定性。以某乘用车ECAS为对象,利用分数阶理论描述橡胶气囊的黏弹性阻尼特性,考虑等效阻尼及滞回特性对其热力学模型进行了优化,结果与实验数据吻合良好,验证了优化后的空气弹簧模型的精确性。在此基础上,考虑车辆纵横向动力学特性与Dugoff轮胎模型,建立14自由度整车ECAS动力学模型,提出模型预测(model predictive control, MPC)主动悬架控制方法,以可测变量为控制器输入,实现直线及转向行驶工况下的主动控制。仿真与整车台架实验研究表明,分数阶修正模型可以很好地反映ECAS变刚度特性,基于MPC的主动悬架控制策略能实时调整空气弹簧刚度,控制车身姿态,有效改善电动汽车行驶时的平顺性与稳定性。论文的研究方法为车辆悬架系统建模及主动控制提供了一种新思路。

LQG-IMC集成的空气悬架车身俯仰姿态控制策略研究

为了提高空气悬架车辆在非紧急工况下的整车性能和车身姿态,建立了刚度可调空气悬架车辆半车纵向行驶动力学模型,结合LQG控制与IMC控制的优缺点,设计了空气悬架LQG-IMC集成控制器,并引入粒子群算法来优化了IMC时间常数。应用MATLAB/Simulink搭建了仿真模型,仿真了初始速度30m/s、B级路面和非紧急制动工况。结果表明,与被动悬架相比LQG-IMC集成控制空气悬架车辆的车身俯仰角、前悬架及后悬架的动挠度均方根分别改善了56.44%、53.33%和63.71%,且车身姿态得到进一步控制,为空气悬架控制器的开发奠定了理论基础。

轮毂电机电动汽车空气悬架阻尼GA-LQR控制研究

针对轮毂电机驱动电动汽车因电机内部不平衡电磁力引起的负面振动加剧等问题,提出一种基于遗传算法的线性二次型调节器(GA-LQR)的空气悬架阻尼控制方法。建立包含轮毂电机和空气悬架系统的轮毂电机驱动电动汽车8自由度半车动力学模型,并进行实车试验验证模型;仿真分析路面激励和不平衡电磁力两者对电动汽车垂向振动的影响;根据最优控制理论提出LQR控制策略,并通过遗传算法对LQR控制中的加权矩阵Q和R进行全局搜索优化,构建了GA-LQR阻尼控制器。仿真结果表明:相较于被动悬架和LQR控制的空气悬架,基于GA-LQR控制的空气悬架对电动汽车各评价指标的改善效果明显,可有效抑制轮毂电机因偏心引起的不良振动,极大地提高车辆的乘坐舒适性。

车辆主动空气悬架控制系统开发与研究

以主动空气悬架为研究对象,建立1/4动力学模型。针对悬架系统非线性特性强、易受外界干扰等缺点,选用模糊滑模控制算法对主动悬架控制系统进行设计与开发。使用Simulink软件建立悬架控制系统模型,并设计控制系统硬件。通过硬件在环仿真验证所设计的控制算法的有效性,结果表明:所设计主动悬架控制系统相较于被动悬架在车身加速度、悬架动挠度和轮胎动位移性能上分别提高了24.52%、29.40%和9.72%,有效地提高车辆行驶的操纵稳定性,同时也改善整车乘坐的舒适性。

乘用车电控空气悬架高度控制策略

为了提高乘用车电控空气悬架在车身高度调节过程的控制精度,设计了基于粒子群的PID控制器。首先通过对空气悬架系统工作机理的分析,利用AMESim建立单轮空气悬架数学模型,针对车高调节过程中出现的“过充过放”问题,设计了基于粒子群的PID控制器,然后在AMESim-Simulink-Carsim联合仿真平台中建立了整车空气悬架模型对其控制效果进行验证。最后进行了实车测试。结果表明,所设计的基于粒子群的PID控制器在不同工况下的车身高度稳态误差均小于2 mm,且没有出现明显的高度反复调节或者控制超调现象。

悬索桥主缆截面固定网格多孔模型构建与流动特性研究

为研究悬索桥主缆除湿过程中紧束态钢丝束区域截面流动特性,以深中通道伶仃洋大桥为背景进行主缆截面固定网格多孔模型构建与流动特性研究。利用固定网格的方法,考虑钢丝束间隙,构建一种适用于悬索桥主缆截面的精准多孔模型,研究钢丝束间隙、通气方向、阻力系数计算方法、钢丝束阶数对空气流动特性的影响。结果表明:通气方向不同时,精准多孔模型体现了主缆截面内部流速分布的不均匀性以及流动阻力的各向异性;入口速度一定时,垂直通气时两侧间隙流速大于钢丝束内部流速,水平通气时水平间隙流速有所增大,垂直通气进出口压差大于水平通气,两者相差11.29%;对比采用Ergun公式计算的阻力系数模型与采用拟合计算的实际阻力系数模型,进出口压差差异随着入口速度的减小而逐渐增大,在入口速度为0.031 25 m/s时,水平通气和垂直通气下,2种模型进出口压差差异分别为89.5%和95.6%;钢丝束阶数不同时,各个阶数粘性阻力系数值相差小于1%,惯性阻力系数值相差小于2%,可认为阻力系数计算与钢丝束阶数近似无关。

基于灵敏度分析的某商用车悬架系统参数优化

为提高某商用车的行驶平顺性,对某商用车悬架系统参数进行了优化.基于空气弹簧试验数据拟合得到其刚度特性曲线,建立前后悬架及整车多体动力学模型,仿真得出该车随机输入工况和脉冲输入工况平顺性.搭建悬架系统参数化的多平台联合仿真模型,通过全域灵敏度分析得出悬架系统设计参数对平顺性的影响程度.建立整车平顺性多目标响应面近似模型,利用多目标遗传优化算法进行参数可行域内寻优.结果表明:在随机输入工况下,车速为100 km/h时,驾驶员处和乘客处加权加速度均方根值分别减小了12.50%和29.71%;在脉冲输入工况下,车速为30 km/h驾驶员处和车速为20 km/h乘客处的垂向最大加速度分别减小了14.69%和31.28%,优化效果明显.

核桃物料空气动力学特性研究与壳仁风选设备优化

壳仁分选是核桃破壳取仁的重要环节,是核桃进行精深加工的基础。为探索风选技术在核桃壳仁分选领域的可行性,通过理论计算与试验研究对核桃物料的空气动力学特性进行了研究,并在此基础上设计了一种核桃壳仁风选设备,运用单因素试验和响应面试验对该设备的工作参数进行优化。结果表明:核桃壳仁混合物料中仅有碎仁与1/2壳的悬浮速度范围有少量重叠区域,同等级核桃壳、仁具有不同的悬浮速度范围,通过控制气流速度可实现核桃壳仁分离;核桃壳仁风选设备的工作参数对清选率的影响由大到小依次为入料口高度、喂料速度、风机频率,最佳工作参数组合为喂料速度5kg/min、风机频率46Hz、入料口高度34mm,在此条件下清选率为99.32%,损失率为1.03%。综上,运用风选法进行核桃壳仁分离具有可行性,通过参数优化可提升风选设备的分选效果。

基于模式切换的互联空气悬架性能研究

为进一步提高互联空气悬架性能,设计了一种互联模式切换策略,该策略首先建立互联空气悬架整车动力学模型;然后基于平顺性和操稳性性能指标函数设计综合评价指标,利用不同连通模式下综合指标的变化规律,设计互联模式切换控制策略;最后进行数值仿真,仿真结果表明,该控制策略可明显地改善互联空气悬架性能,提高乘车舒适性。