【作者】 赵亮；

【导师】 钟志华；

【作者基本信息】 湖南大学 ， 车辆工程， 2008， 博士

【摘要】 目前车辆悬架系统振动研究主要集中在两方面:（1）新的弹性元件和阻尼元件的提出;（2）新的振动控制算法的提出。本着这一指导原则,本论文在这两方面都提出了一些创新性的工作:（1）首先根据实际车辆的底盘布置形式,提出了一种崭新的阻尼元件即扭转阻尼减振器,并且对其进行了深入的研究;（2）以可控悬架为控制对象,提出了一些创新性的悬架振动控制算法。其研究内容如下:1.扭转阻尼减振器的研究在实际车辆的底盘设计中,设计者往往希望将底盘设计的越紧凑越好,根据这一指导原则,通过分析现有悬架结构中减振器与弹簧以及导向机构的安装方式,创新性的提出了一种便于实现与扭杆弹簧进行紧凑安装的扭转阻尼减振器,并且在第七代菱形车上得到了应用。本论文将围绕扭转阻尼减振器进行多方面的研究,以便将其推广到以扭杆弹簧作为弹性元件的现行车辆中去。首先讨论了阻尼元件、弹性元件与菱形车中悬架系统的匹配设计。根据四分之一悬架模型建立了悬架性能指标与车辆参数的函数关系。分析了车辆系统参数对悬架性能指标的影响,确定以阻尼系数作为优化变量的四分之一悬架系统多目标优化问题。利用小种群多目标遗传算法对这个多目标问题进行优化求解。在频域内分析了阻尼系数对悬架性能指标的影响,得到了阻尼系数与悬架系统匹配设计的一般规律,即车身共振区需要重阻尼、人体振动敏感区需要轻阻尼、非簧载质量共振区需要重阻尼。由于车身共振区与非簧载质量共振区的阻尼力分别对应开阀阻尼力和最大开阀阻尼力,因此减振器的外特性可以用三级阻尼力的形式进行控制。利用三级阻尼力控制的方法实现了以线性悬架系统优化设计的阻尼系数构成减振器的非线性外特性曲线。根据悬架性能指标的相应要求,选择十组具有代表性的非支配解进行不同频率下的悬架性能指标概率分析,确定了平均开阀阻尼系数和平均最大开阀阻尼系数。通过选择双向阻尼比计算了伸张行程和压缩行程中的开阀阻尼系数和最大开阀阻尼系数。利用减振器在悬架中的一般布置结构得到了开阀速度和最大开阀速度,从而得到了与该悬架匹配的减振器非线性外特性曲线。利用伸张行程的开阀阻尼力计算菱形车中悬架系统所需等效筒式减振器的活塞和活塞杆的尺寸。当阻尼元件确定以后,弹性元件利用汽车设计中提出的扭杆弹簧设计方法就可以很方便地得到。根据流体力学和液压理论建立了扭转阻尼减振器阻尼力矩的基本计算公式,计算得到了常通节流小孔的直径、伸张阀和压缩阀的基本参数,并且建立了扭转阻尼减振器物理参数力学模型,通过对其进行的仿真,得到其外特性速度曲线,该曲线与三级阻尼力控制计算得到的等效阻尼力曲线非常相似。紧接着分析了缝隙对扭转阻尼减振器的影响。为了进一步论证上面提出的扭转阻尼减振器外特性计算理论的正确性,设计制造了一扭转阻尼减振器进行台架试验研究。通过将试验研究的结果与理论模型的对比证明上述的理论计算是合理的。为了方便后面的振动分析,根据试验得到的结果建立了扭转阻尼减振器的数学模型。并且利用遗传算法对模型中的参数进行反求。最后对基于扭转阻尼减振器的扭杆弹簧双横臂悬架的非线性平顺性进行仿真分析。利用空间运动学和动力学建立扭杆弹簧双横臂悬架的运动学和动力学方程,证明了双横臂悬架的空间运动对扭转阻尼减振器在车轮垂向上提供的等效阻尼力没有影响。根据虚位移原理计算得到了扭杆弹簧双横臂悬架的非线性悬架刚度与车轮跳动的函数关系。最后根据车辆平顺性脉冲激励和随机激励的国标要求对其进行了非线性的平顺性仿真,仿真结果表明基于扭转阻尼减振器的扭杆弹簧双横臂悬架的平顺性是合理的。2.可控悬架控制算法的研究本文所指的可控悬架有两种形式:（1）磁流变阻尼器半主动悬架;（2）主动悬架。分别以上面两种悬架为控制对象提出了一些具有创新的振动控制算法。（1）磁流变阻尼器半主动悬架最优控制研究磁流变阻尼器是一种基于智能材料的、新型的半主动阻尼器。所产生的阻尼力可调范围比传统阻尼器大,反应迅速,易于控制,因此能够更好的应用于车辆系统的减振,实现从被动悬架向半主动悬架的飞跃。本文利用最优控制对基于磁流变阻尼器的四分之一车辆系统的半主动控制进行研究。采用改进型Bouc-Wen模型作为磁流变阻尼器的力学模型。利用小种群遗传算法（μGA）对随机最优控制器的权值进行寻优。仿真结果表明,利用最优控制的磁流变阻尼器半主动悬架性能指标明显优于被动悬架。（2）基于多目标遗传算法的主动悬架H₂/H_∞多目标控制研究本文利用多目标遗传算法结合线性矩阵不等式对四分之一主动悬架的混合H₂/H_∞控制的保守性进行研究。将车身垂向加速度定义为H₂性能指标。悬架动行程和轮胎动位移定义为H_∞性能指标。利用多目标遗传算法（μMOGA）搜索控制增益,通过解矩阵不等式得到H₂和H_∞范数。将计算得到的H₂和H_∞范数结果和Matlab多目标控制工具箱进行比较,发现基于μMOGA的LMI优化方法的保守性明显小于Matlab多目标控制工具箱的计算结果。根据μMOGA/LMI对四分之一主动悬架进行设计,其仿真结果和被动悬架进行比较发现主动悬架的性能指标明显优于被动悬架的性能指标。更多还原

【Abstract】 Nowadays, investigations on vibration of vehicle suspension system mainly concentrate in two aspects: （1） new spring elements and damp elements; （2） new vibration control algorithms. According to the idea, the dissertation proposes some original works in the two aspects: （1） according to analyzing actual vehicle chassis layout, a new damp element （torsion damp shock absorber） is presented and investigated; （2） controllable suspension is regarded as control object to investigate some suspension vibration control algorithms. Its investigations are followed as:1. Investigation on torsion damp shock absorberIn the process of designing practicable vehicle chassis, designers usually hope that the vehicle chassis is very compactly designed. According to the principle, analysing the installment method of the shock absorber with the spring and the guide mechanism in current suspension structure, a torsion damp shock absorber is originally proposed to practise compact installment with torsion bar spring and successfully applied into the seventh diamond vehicle. Therefore, the dissertation will investigate the torsion damp shock absorber in some fields in order to make it popular in present vehicle with torsion spring.It is firstly discussed that a damp element and a spring element matchs with the diamond vehicle middle suspension. The function of suspension performance index and vehicle parameters was established according to the 1/4 suspension model. Analyzing the effect of the vehicle parameters to the suspension index, it was detemined that damp coefficient was regarded as an optimization variable in the 1/4 suspension system multi-objective optimization. The multi-objective optimization problem was sovled by micro multi-objective genetic algrothim. The effect of the damp coefficient to the suspension index was discussed in frequency range and the rule of the damp coefficient matching with the suspension system was obtained. The rule is that the resonance range of the vehicle body and unspring weight need heavy damp and the body sensitive range need soft damp. Because the damp force in resonance range of the vehicle body corresponds to the opening valve damp force and the damp force in resonance range of the unspring weight corresponds to the max opening valve damp force, the velocity characteristic curve of the shock absorber can be controlled with three stage damp force. The method is implemented that using optimization design damp coefficient in linear suspension system constructs nonlinear velocity characteristic curve. According to suspension index requirements, choosing ten groups typical non-dominated solution and calculating their probability was to obtain average opening valve damp coefficient and average max opening damp coefficient. Choosing bidirection damp ratio, the opening valve damp coefficient and the max opening valve damp coefficient in promotion and compress process of the shock absorber were calculated. After the opening valve velocity and the max opening valve velocity was obtained according to the shock absorber in suspension structure arrangement, the nonlinear velocity curve of the shock absorber matching with the suspension structure can be obtained. The piston and piston stick diameters of the equivalent tube shock absorber matching the diamond vehicle middle suspension system can be calculated with the opening valve damp force in the promotion process. After the damp element is determined, the spring element is easy to be obtained by torsion bar spring design method in the vehicle design theory.According to fluid mechanics and hydraulic theory, the basic equation to calculate the damp moment of the torsion damp shock absorber was established. The diameter of the normal open orifice and the basic parameter of the promotion valve and compress valve were calculated. Its physics parameter mechanics model was built up. The velocity characteristic curve obtained by simulating in a computer was similar with the equivalent damp force curve controlled by three stage damp force. The gap effect to the torsion damp shock absorber was analysed.Afterwords, in order to demonstrate that the theoretical calculation to the above-mentioned torsion damp shock absorber was correct, a torsion damp shock absorber was designed and manufactured in order to be investigated in experimental rig. Through comparing the experimental results with theoretical model, it was indicated that the above theory calculation was reasonable. To be convenient vibration analysis in the next chapter, the mathematical model of it was proposed by experimental results. The parameters of the model was inversely solved by genetic algorithm.Finally, the nonlinear ride equality of the torsion bar spring double wishbone suspension based on torsion damp shock absorber was simulated in the disstertation. The kinematics and dynamics equations of the torsion spring double wishbone suspension was concluded according to space kinematics and dynamics. It was proved that space movement of the double wishbone suspension can not affect the equivalent damp force produced by torsion damp shock absorber above the tire vertical direction. The function of the nonlinear suspension stiffness with tire skipping distance was obtained by virtual displacement theory. At last, the nonlinear ride equality was simulated according to the national standard requirements to vehicle ride equality stimulated by pulse stimulation and random sitmulation. The simulation results presented that the ride equality of the torsion bar spring double wishbone suspension based on torsion damp shock absorber was reasonable.2. investigation on controllable suspension control algrithmsThere are two forms of the controllable suspension in the dissertation: （1） magnetorheological damper semi-active suspension; （2） active suspension. Above-mentioned two suspensions were respectively regarged as controllable object to investigate their vibarion control algorithms.（1） magnetorheological damper semi-active suspension optimal control investigationMagnetorheogical damper is a semi-active damper based on intelligent materials. The damp force adjustable scope produced by it is more than traditional damper. Because the MR damper can quickly react and be easily controlled, it can be applied into vehicle suspension damp systems. In the paper, the quarter vehicle system based on magnetorheological damper is investigated by the optimal control. The improved Bouc-Wen model is used to describe the mechanical model of MR damper. The weight values in the optimal control are found by the micro-genetic algorithm. Numerical results demonstrate that the optimal control strategy for the performance improvement of the semi-active suspension based on MR damper is very effective.（2） the investigation on the mixed H₂/H_∞multi-objective control on the active suspension based on multi-objective mirco genetic algorithmsThe paper presents to use micro multi-objective genetic algorithm （μMOGA） to deal with the conservation problem about the active suspension multi-objective control while solving the mixed H₂/H_∞multi-objective robust control with linear matrix inequality （LMI） method. A quarter-vehicle model with active suspension system is considered. The acceleration of the vertical vehicle body is defined in the H₂ performance specification. The max suspension workspace and the tyre deflection are defined in the H_∞performance specification. After the control gain has randomly been sought byμMOGA, the H₂ and H_∞norm of the close-loop system are calculated by LMI toolbox. The comparison between H₂ and H_∞norm calculated byμMOGA/LMI and the multi-objective control toolbox in Matlab shows clearly in simulation the advantages of theμMOGA/LMI method. The conservation problem is obviously reduced by uMOGA/LMI method. In the framework ofμMOGA/LMI optimization, the mixed H₂/H_∞multi-objective robust control active suspensions are designed on a quarter-vehicle model. The comparison of the simulation results between passive and active suspension shows that ride comfort performance is clearly improved while assuring suspension deflection within bounds and convincing a firm contact of wheels to road.更多还原