Design of Linear Functional Noncircular Gear with High Contact Ratio Used in Continuously Variable Transmission

Continuously variable transmission(CVT)of noncircular gear has the technical advantages of large bearing capacity and high transmission efficiency.The key technology of CVT with noncircular gear has been broken through some countries,and is in the stage of deep application research.Although the characteristics and design methods of noncircular gear pairs have been continuously studied in China,the noncircular gear CVT is still in the preliminary exploration and research stage.The linear functional noncircular gear pair,whose transmission ratio is a linear function in the working section,to realize continuously variable transmission was the research object in this paper.According to the required transmission ratio in the working section,the transmission ratio function in the non-working section was constructed by using a polynomial.And then the influence of pitch curve parameters in the working section on which in the non-working section was also analyzed to obtain the pitch curve suitable for transmission of this gear pair.In addition,for improving the stability and bearing capacity of gear transmission,the noncircular gear pair transmission with high contact ratio was designed.Furthermore,the accurate value of the contact tooth length was calculated based on the gear principle and the characteristics of the involute tooth profile,from this the contact tooth length error was calculated by comparing the accurate value with its actual value obtained by the rolling experiment.Finally,an indirect method to verify the contact ratio by detecting the contact length error of the tooth profile was proposed.

Hydro-mechanical Transmit Performance Analysis for a Continuously Variable Transmission

Based on an exact CAD model of hydro-mechanical continuously variable transmission （HMCVT） gearbox which can transmit 180 horsepower, virtual prototype of the HMCVT was built. Revolution speed of shafts, gears and clutches of the HMCVT were calibrated by using results obtained by theoretical calculation and test methods. The needed power and torques of both mechanical power input shaft and hydropower input shaft were calculated by simulation. Hydraulic power distributing ratio and power flow of the system was also studied. The analysis results showed that cycle power was produced inevitably when the output shaft speed of HMCVT change smoothly during mechanical and hydraulic working state HM1 to HM4, and the instantaneous maximum cycle power was 39.5%. Then the overall transmission efficiency of HMCVT was studied, and the maximum overall efficiency of the system was about 87%. The results of the studies gave references to select suited engine and variable displacement pump for the HMCVT, and to develop rational speed control strategies for the HMCVT by changing displacement ratio of variable displacement pump.

Integrated Control Strategy for CVT Powertrains with Consideration of Vehicle Drivability

During shift,power flow is not interrupted in powertrains equipped with continuously variable transmission（CVT）.When hard acceleration is commanded,engine speed will flare and corresponding torque will be consumed,which leads to a drop in vehicle drive torque and also the vehicle acceleration.This is the reason why CVT vehicles have poor drivability during hard acceleration maneuver.Conventional method such as torque compensation doesn＇t always work due to the limited backup torque of engine.According to this,means to evaluate the drivability of CVT vehicles are studied,affect factors of drivability are analyzed in detail.Hard acceleration process of CVT vehicle is studied by theoretical analysis,based on which engine torque and ratio change rate of CVT are identified as two key control parameters that decide the drivability of CVT vehicles during hard acceleration maneuver.Therefore,a control strategy based on restricting the change rate of CVT ratio together with torque compensation is proposed,and two different algorithms to establish the limitation of ratio change rate are proposed.These two algorithms are simulated and compared with each other,results indicate that drop of vehicle acceleration is eliminated evidently by limit the change rate of CVT ratio,but small ratio change rate also results in a longer time to finish the accelerate process,an algorithm to decide a proper ratio change rate is needed in order to tune these different characteristics.In order to get better control effects,a new fuzzy logic based algorithm is proposed to decide a proper ratio change rate during kick down conditions,simulation and experiment results indicate that,the amount of vehicle acceleration decrease is reduced from about 1 m/s2 to almost 0,in the mean time the accelerate process only delayed for about 0.3 s.The proposed control strategy and algorithm can effectively tune the characteristics of CVT equipped vehicle during kick down conditions.

基于DEM的无人驾驶拖拉机前馈稳速控制

针对农田坡度变化影响无人驾驶农机行驶速度稳定性,进而降低播种均匀性和肥药施用精度等问题,该研究设计了一种基于农田数字高程模型(digital elevation model,DEM)和前馈控制策略的拖拉机稳速控制方法。首先建立坡地干扰补偿模型,基于拖拉机实时位置从农田DEM中提取前方作业路径的坡度信息,计算拖拉机前方目标速度补偿量,实现拖拉机行驶的稳速控制。以DF1204无级变速拖拉机为试验平台,在中国农业大学烟台研究院开展3组不同目标速度的上坡、平地和下坡行驶对比试验。试验结果表明,拖拉机以目标速度4、6和8 km/h行驶时,上坡行驶的实测速度均值分别为4.03、5.94和7.85 km/h,平地行驶的实测速度均值分别为4.04、6.02和8.03 km/h,下坡行驶的实测速度均值分别为4.00、6.10和8.19 km/h,与对照组相比,在上坡、平地和下坡行驶时的速度均方根误差平均分别降低了46.63%、21.92%和37.15%,试验组上坡和下坡行驶的实测速度均值更接近目标速度。所提方法可有效提高无人驾驶拖拉机在起伏农田的稳速控制精度,有助于提高农机作业质量。

Research on the novel discretized ratio control strategies and hardware-in-the-loop test for continuous variable transmission system

Based on traditional continuous control strategy for Continuously Variable Transmission(CVT)ratio,according to the principles of shift control strategy for stepped automatic transmission,the influences of throttle opening and external resistance or vehicle speed on CVT ratio control are analyzed on bumpy road.Under the same variation of external resistance condition,the differences between optimal economic control strategy and optimal dynamic control strategy are discussed.Then,the traditional continuous optimal dynamic and economic control lines are divided into multi-step upshift points.Meanwhile,the corresponding downshift points are set to avoid the interference near shift points.After that,the novel discretized ratio control methods for CVT system are proposed.By respectively discretizing throttle opening and vehicle speed,the discretized ratio control strategy for throttle opening,and the integrated discretized ratio control strategy for throttle opening and vehicle speed are further proposed and simulated.Furthermore,the hardware-in-the-loop(HIL)test system is built to further verify the feasibility and accuracy of discretized ratio control strategies.Both simulation and HIL test results show that the sensitivity of throttle opening and vehicle speed to ratio control is reduced dramatically,the fluctuation of ratio is decreased considerably,the transmission efficiency is increased significantly,and the jerk is declined moderately.

拖拉机液压机械无级变速器速比匹配设计与实验

液压机械无级自动变速器能够根据拖拉机作业模式的差异,实现不同作业模式下发动机转速、转矩的匹配。将液压机械前进区段设计为等比四区段,各区段传动公比φ为1.88,纯液压区段用于拖拉机低速爬行作业以及起步。基于液压机械换段等比传动的连续性,对各区段齿轮的参数以及传动比进行设计,并对变量泵和定量马达的匹配进行选型。加载实验中模拟拖拉机不同作业模式的负荷,进行了液压机械各区段下的发动机最佳经济点的速比匹配。验证了变速箱在各区段之间的平稳换段以及拖拉机平稳加速的连续性响应。

金属带式无级变速器的速比控制

在分析了速比控制阀特性的基础上 ,考虑到无级变速传动系统的复杂性 ,设计了模糊控制器 ,开发了基于速比反馈的速比控制系统 ,并进行了台架模拟试验。试验结果表明 ,实际速比能够较好地跟踪目标速比的变化 。

等差式液压机械无级变速器的速比控制理论与试验研究

速比跟踪控制是车辆无级变速器控制系统的核心,以等差式液压机械无级变速器为对象开展速比控制理论研究,提出适合于液压机械无级变速器使用的速比控制方法。分析等差式液压机械无级变速器的组成原理,推导出等差式液压机械无级变速器速比关系的一般表达式,获得等差式无级变速器的段位组成方式;结合研究对象具体结构,研究换段时各执行元件的转速关系,提出换段条件;构建速比控制系统的设计框图,分析得到控制器的传递函数,给出控制算法设计方法;对等差两段式液压机械无级变速器进行速比跟踪控制试验,试验结果表明:通过对液压机械无级变速器实施速比控制,能够实现对目标速比的跟踪;当跟踪阶跃速比时不存在稳态误差,跟踪斜坡速比时存在稳态误差。

混合动力汽车动力传动系参数设计

根据整车控制策略和自动无级变速器 (CVT)特性 ,以满足整车动力性指标为前提 ,从最大限度地降低电机、电池组容量和燃油油耗的角度 ,对装备 CVT的并联型混合动力汽车的发动机功率、交流感应电动机特性。

金属带-行星齿轮无级变速系统调速特性的研究

车用金属带行星齿轮无级变速传动系统 ,具有结构简单、速比变化范围宽 (可超过 2 5～ 30 )的优点 ,是目前国际上广泛进行研究的一种较理想的新型传动装置。本文详细阐述了其传动机理和功率流程 ,并通过速比调控规律的分析 ,揭示了系统于同步转换点处发生振动的内在原因 。

轻度混合动力汽车再生制动能量管理策略

提出以满足ECE制动法规为前提,蓄电池再生制动能量回收最大为优化目标的轻度混合动力汽车再生制动能量管理策略。基于发电机效率图、蓄电池充电效率图和发动机反拖阻力矩图,建立发电机和行车制动系的制动力分配优化模型,分别获得采用有级式变速器和无级变速传动的轻度混合动力汽车在不同制动强度下的再生制动能量管理控制规则。分别对采用单离合器—有级式变速器、双离合器—有级式变速器和无级变速器三种传动型式的轻度混合动力汽车进行NEDC循环工况仿真,结果表明采用双离合器—有级式变速器的轻度混合动力汽车再生能量效率最高。对采用有级式变速器的混合动力系统完成了基于dSPACE快速控制原型技术的再生制动控制试验。

基于无级变速器速比控制的插电式混合动力汽车再生制动控制策略

为了能够在不影响驾驶制动意图的同时尽可能多地回收制动能量,首先在基于再生制动门限值所制定的理想再生制动力分配策略的基础上,考虑电机、电池及无级变速器(CVT)综合效率最优的目标要求,制定了基于综合效率最优的CVT速比控制策略;然后,根据制动过程中传动系统动态特性分析所得到的系统惯性矩与驾驶制动意图之间的关联规律,以提高再生制动功率为目标,采用离散穷举优化方法对CVT目标速比及制动力分配进行修正,从而提出了基于速比变化限制及电机协调控制的CVT速比优化控制策略。仿真结果表明,在不同的工况下,本文提出的再生制动控制策略能使车辆在制动过程中有效跟随驾驶员的制动意图,同时提高再生制动能量回收率,改善驾驶性能。

DMC-PID串级控制在CVT速比控制系统中的应用

通过分析CVT速比控制系统的结构及基本控制原理,确定该系统具有时滞弱非线性特性,论述了常规PID控制算法以及单一的DMC控制算法应用于该系统的局限性.针对这一问题,设计了DMC-PID串级预测控制算法,该算法将经过PID校正的速比控制系统作为广义的控制对象,用DMC预测算法在线滚动优化控制参数,在优化过程中利用实测信息不断进行反馈校正,充分发挥DMC算法的超前预测性和强鲁棒性以及PID控制算法的抗干扰能力.台架实验结果表明,与常规的PID算法相比,该算法能有效减小速比跟踪过程中的波动,超调量由14%下降为4%,过渡时间由6 s缩短为4.5 s,提高了系统的动静态性能.

金属带-行星齿轮无级变速传动效率特性分析

在金属带无级变速传动效率试验测试的基础上 ,建立了金属带行星齿轮无级变速传动效率分析模型 ,获得了传动效率随传动速比、传递扭矩和输入转速等因素的变化规律 ,从而为金属带行星齿轮无级变速传动控制策略的制定和变速器产品的开发打下基础。分析结果显示 :该无级变速传动方式较目前广泛采用的纯金属带无级变速传动和双状态无级变速传动系统具有更好的效率分布特性。

拖拉机液压机械无级变速箱控制与交互系统

为了满足拖拉机各种作业工况下的行驶速度及动力需求,对拖拉机液压机械无级变速箱的控制与交互系统进行了研究。首先,针对自主研发的某新型液压机械无级变速箱,简要阐述了其液压功率分流机构与无级调速原理,明确了被控对象与控制量。而后,对变速箱的无级调速与负载自适应控制进行了研究,一方面,提出了变速箱速比的点位控制方法,将变速箱速比在全程范围内划分为96帧,作出每一帧与变量泵励磁电压、变量泵流量方向电磁阀、离合器电磁阀的动作关联查询表,通过程序指针的顺序移动实现无级调速与段位切换;另一方面,基于发动机功率控制的要求,提出了一种负载自适应速比调整策略,给出了相应的模糊控制表,并分析了该算法在不同段位区间内的性能;而后,阐述了无级调速拖拉机的交互挡杆与变速箱电子控制单元设计;最后,基于所开发的控制系统进行了拖拉机加速和负载自适应调整试验。研究结果表明,点位控制时拖拉机的速比调节过程较为稳定,属于开环控制;负载自适应控制时的变速箱速比完全取决于负载变化,属于反馈控制。研究结果表明,所设计的控制系统可以很好地对拖拉机液压机械无级变速箱实施控制。

履带车辆液压机械差速转向系统控制策略

为了准确实现驾驶员转向意图,解决履带车辆液压机械差速转向系统转向行驶控制问题,该文在对液压机械差速转向系统工作原理进行分析的基础上,运用动力学理论和模块化方法,推导了液压机械差速转向系统动力学方程,建立了系统数学模型。根据履带车辆转向行驶理论和转向安全要求,结合系统数学模型,设计了一种履带车辆液压机械差速转向系统控制策略,通过控制单元与液压泵排量控制器相互配合实现转向控制。仿真结果表明,所设计的液压机械差速转向系统控制策略安全有效,能准确实现驾驶员转向意图。

基于驾驶意图的无级变速器目标速比确定方法

运用模糊数学理论提出一种基于驾驶意图的金属带式无级变速器(CVT)目标速比的确定方法,不需采用传统的经过手动方式选择动力模式或经济模式的方式,即可确定一个在动力和经济模式之间的目标速比。根据基于模糊规则的驾驶意图指数确定的目标速比进行CVT的速比控制,以达到按照驾驶意图来兼顾汽车的动力性和经济性能,从而避免了传统模式选择过程中速比突变导致传动系统的冲击、振动和发动机颤动,且能够根据驾驶员的驾驶意图进行调整,提高了驾驶操纵性。最后根据目标速比控制策略设计了控制器,并通过试验验证了目标速比确定方法的适用性。

轻度混合动力汽车巡航工况总工作效率分析和优化

在混合动力电动汽车巡航工况时,为了降低油耗和延长电池的使用寿命,对其能量管理策略的优化除了考虑发动机和电动机工作点的优化之外,还应考虑电池工作点的优化。针对这个问题,建立一种具有无级变速结构的轻度混合动力电动汽车的纵向动力学方程,在此基础上综合考虑发动机、电池、电动机与传动系统的效率,分析车辆巡航工况下的系统效率,得到系统效率优化的目标函数和约束条件。随后利用序列二次规划算法对轻度混合动力电动汽车系统效率进行优化计算,从而确定车辆巡航工况下的最佳蓄电池功率和最佳无级变速器(Continuously variable transmission,CVT)减速比。优化结果揭示出驱动系统的特性,可为驱动系统的优化奠定基础。

无级变速汽车最佳动力性优化控制策略

无级变速器(Continuously Variable Transmission,CVT)效率对汽车驱动功率的大小有直接影响,需要在最佳动力性控制中加以考虑。在分析CVT效率对汽车驱动功率影响机理的基础上,以驱动功率最大为优化目标,对各节气门开度和车速下的CVT目标速比进行优化计算。建立系统仿真模型,对优化前后的控制效果进行了仿真对比分析,结果表明,优化后系统百公里加速时间减少约0.63s。

提高汽车金属带式无级变速器效率的途径

分析了目前汽车金属带式无级变速器（MBCVT）传动效率未能得到充分发挥的原因,结果表明,现有的MBCVT的带轮轴向力是根据最大传递转矩来确定的,这样会使带轮轴向力过大,加大了液压系统的能耗.通过实验探索了其核心元件——金属带传动的滑差率和效率与传递载荷的关系.依据实验结果,提出了根据实际传递转矩施加带轮轴向力的方法：通过控制滑差率在9.6%-10.9%之间来调节带轮轴向力的大小,保证金属带传动始终工作在转矩比为0.8-0.9范围.这是其传动能力最强、传动效率最高的工况,可减少轴向力10%-46%,降低油耗5%-8%.