Variable Gear Ratio Control Using Vehicle Body Slip Angle

Vehicles with variable steering characteristics have long been studied and compared with those having typical fixed gear ratio steering, and the variable gear ratio properties are reported to have improved maneuverability and stability in high-speed lane changes and on slippery low-friction road surfaces. However, it is not clear how gear ratios should be set for individual vehicle characteristics. Therefore, the present study has investigated a variable steering gear system using body slip angle feedback for the purpose of improved maneuverability and stability in the critical cornering range and upwards, in excess of the critical limit, and into the countersteer range. The results of a driving simulator experiment show that the steering effect improves and maneuverability and stability increase in the critical cornering range and upwards, in excess of the critical limit, and into the countersteer range by applying linear-variable control to the steering ratio from a body slip angle of 5?. This result is seen both in double lane changes, such as in hazard avoidance, and in J-turns with long drifting. Moreover, it shows an improvement in drift controllability through prompt countersteering. Overall, the present system can enhance the driver’s hazard avoidance capability.

Variable stiffness control algorithm for high-rising buildings of closely spaced frequencies based on wavelet transforms

To establish the algorithm of SAT-TMD system with the wavelet transform(WT),the modal mass participation ratio is proposed to distinguish if the high-rising structure has the characteristic of closely distributed frequencies.A time varying analytical model of high-rising structure such as TV-tower with the SAT-TMD is developed.The proposed new idea is to use WT to identify the dominant frequency of structural response in a segment time,and track its variation as a function of time to retune the SAT-TMD.The effectiveness of SAT-TMD is investigated and it is more robust to change in building stiffness and damping than that of the TMD with a fixed frequency corresponding to a fixed mode frequency of the building.It is proved that SAT-TMD is particularly effective in reducing the response even when the building stiffness is changed by ±15%;whereas the TMD loses its effectiveness under such building stiffness variations.

Nonlinear combined forecasting model based on fuzzy adaptive variable weight and its application

In order to enhance forecasting precision of problems about nonlinear time series in a complex industry system,a new nonlinear fuzzy adaptive variable weight combined forecasting model was established by using conceptions of the relative error,the change tendency of the forecasted object,gray basic weight and adaptive control coefficient on the basis of the method of fuzzy variable weight.Based on Visual Basic 6.0 platform,a fuzzy adaptive variable weight combined forecasting and management system was developed.The application results reveal that the forecasting precisions from the new nonlinear combined forecasting model are higher than those of other single combined forecasting models and the combined forecasting and management system is very powerful tool for the required decision in complex industry system.

Power supply for generating frequency-variable resonant magnetic perturbations on the J-TEXT tokamak

To further research the response of the tearing mode（TM） to dynamic resonant magnetic perturbation（DRMP） on the J-TEXT tokamak, a modified series resonant inverter power supply（MSRIPS） with a function of discrete variable frequency is designed for DRMP coils in this study. The MSRIPS is an AC–DC–AC converter, including a phase-controlled rectifier, an LC filter, an insulated gate bipolar transistor（IGBT） full bridge, a matching transformer, three resonant capacitors with different capacitance values, and three corresponding silicon controlled rectifier（SCR） switches. The function of discrete variable frequency is realized by switching over different resonant capacitors with corresponding SCR switches while matching the corresponding driving frequency of the IGBT full bridge. A detailed switching strategy of the SCR switch is put forward to obtain sinusoidal current waveform and realize current waveform smooth transition during frequency conversion. In addition, a resistor and thyristor bleeder is designed to protect the SCR switch from overvoltage. Manufacturing of the MSRIPS is completed, and the MSRIPS equipment can output current with an amplitude of 1.5 kA when its working frequency jumps among different frequencies. Moreover, the current waveform is sinusoidal and can smoothly transition during frequency conversion. Furthermore, the transition time when the current amplitude rises from zero to a steady state is less than 2 ms during frequency conversion. By using the MSRIPS, the expected discrete variable frequency DRMP is generated, and the phenomenon of the TM being locked to the discrete variable frequency DRMP is observed on the J-TEXT tokamak.

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.

Study on fuzzy control of dynamic equalization based on state prediction

A new method of using dynamic equalization technology to realize the maximum energy storage utilization was presented to overcome the influence of the disaccord among units of series super capacitor （SC） bank and ensure that the units could work safely. By considering in combination with the high specific power, low working voltage, wide voltage working range and noulinear external characteristics, we present constant duty ratio pulse frequency modulation mode and fuzzy control method based on state prediction in the active equalization circuit and accomplish the software and hardware design for the equalization system. The simulation analysis and experiment results of constant current muhi-cycle and variable current multi-cycle charge-discharge process verify the validity of the design.

串并联混合动力变速箱挡位对整车性能的影响

针对串并联混合动力车辆变速箱选型匹配问题,采用试验设计(DOE)方法选取变速箱最优速比并分析挡位对整车性能的影响。建立了整车仿真模型和控制策略并进行了台架验证,分析了该混合动力系统3种变速箱挡位配置对车辆的加速性能、爬坡性能和整车油耗的影响。仿真结果表明,挡位的增多可以提高整车动力性,降低整车对电池放电功率及电池容量的需求,但是对整车油耗改善较小。进一步仿真结果表明,即使改善发动机低转速中高负荷区域的燃油消耗率,变速箱挡位数对整车油耗的影响也不大。

重型装载机械的液压无级变速器自适应传动控制策略研究

液压无级变速器作为重型装载机械传动系统的核心部件,对提高装载机械的工作效率和性能具有关键作用。然而,由于工况的复杂性,单纯的液压无级变速器已然无法满足工作需求。因此,文章首先对机械液压无级变速器进行了分析,阐述了其速比测算方式。在此基础上,通过构建阻力估算模型提出了一种分工况速比自适应控制策略。实验结果表明,阻力估算模型的误差平均值为4.5%,MAE最低为3.17、MAPE最低为12.93%、RMSE最低为1.02。相较于传统策略,分工况策略能够加快机械液压无级变速器的运行速度、缩短装载机械的作业时间并节省燃油。其速比控制误差最低为3.3%,响应时间最短为5.7 s。

大展弦比飞行器变形辅助高度控制策略

针对变形飞行器结构/飞行耦合动力学的飞行控制问题,以大展弦比飞行器为研究对象开展了变形辅助高度控制策略研究。采用单元翼多体假设,构建了大展弦比飞行器二面角变形结构,建立了结构/飞行纵向耦合动力学模型,基于线性二次型(LQR)控制器设计方法设计了主动变形(AM)和被动变形(PM) 2种控制策略。其中,被动变形控制策略仅采用升降舵作为控制输入,结构二面角动态行为由耦合动力学驱动;主动变形控制策略以二面角铰链处的扭矩作为额外输入对高度跟踪进行协调控制。仿真分析了2种控制策略下的高度跟踪效果及状态变化,研究结果表明:采用主动变形控制策略可有效改善高度跟踪暂态过程的性能,降低姿态回路的阻尼特性,为未来先进变形飞行器的结构/飞行一体化控制提供研究基础。

双有源桥串联欠谐振变换器的最小回流电流控制

该文采用时域分析法对双有源桥串联欠谐振电路进行了分析,得到电感电流在稳态时的表达式并推导所有开关管实现软开关的条件。由于电压增益偏离1时仅采用移相控制难以实现所有开关管的软开关,因此,该文在传统移相控制的基础上,引入额外的变频控制策略,使得电路在不同的电压增益和负载条件下都能有较好的软开关性能。然而,软开关的实现会增加电路的回流电流,影响电路的传输效率。该文对所提出的变频移相控制进行了进一步的优化,使其可以在确保电路实现软开关的同时产生最小的回流电流和电感电流有效值。所提出的控制策略在一台2 kW的样机中进行了验证。

线控转向系统汽车的主动转向控制研究

以线控转向系统汽车为研究对象,为提高车辆在低附着路面以及高速行驶时的行驶稳定性,提出了一种基于指数趋近律的滑模控制算法。基于Simulink与Carsim平台,建立整车模型,并对转向执行总成部分进行频率响应特性分析,验证其工作稳定性。根据固定转向增益,设计理想角传动比曲线,并设计滑模控制器实现车辆的主动转向功能。仿真结果表明,与PI控制器的结果相比,这里所提出的控制策略可以更有效地实现主动转向功能。

基于模糊控制的车辆线控转向变角传动比研究

为了提高线控转向车辆的操纵稳定性,文章首先在不同速域下对车辆响应进行研究,确定车辆稳态增益的变化特征。其次对不同方向盘输入频率的车辆响应进行分析,确定以转向输入频率为模式切换的阈值条件。然后对方向盘中位与“死区”的关系进行探究设计传动比的增量规律。最后,基于多因素的分析设计变结构传动比模糊控制器,并通过典型工况进行仿真研究。结果表明,在稳态回转试验工况下该策略在低车速下车辆转弯半径明显小于机械转向系统,并随着车速的提高横摆角速度响应降低但仍高于机械转向,这符合理想传动比的设计要求。同时在中间转向试验工况中,该策略下的车辆横向位移更小,符合在中间转向位置需要较大转向输入的预期。

基于模型预测VSFPWM的串联绕组逆变器电磁干扰抑制研究

脉宽调制(Pulse width modulation,PWM)逆变器开关过程产生的共模电磁干扰(Electromagnetic interference,EMI)会对系统产生显著的负面影响。以新型的串联绕组逆变拓扑结构为研究对象,采用基于电流纹波预测模型的变开关频率脉宽调制技术(Variable switching frequency PWM,VSFPWM),同时考虑实际逆变系统中电感饱和效应的影响,实现对电流纹波的精确控制,完成共模电磁干扰的抑制和开关损耗的降低。提出串绕组拓扑下考虑电感饱和的模型预测变开关频率策略,通过仿真和试验对比分析不同变频开关频率调制策略下的电磁干扰抑制效果、输出电流质量及开关损耗等性能。仿真和试验表明该策略能够有效抑制共模电磁干扰、降低开关损耗,并确保输出电流的波形质量。

海洋石油开采中钻井泵变频调速修正控制方法

海洋石油钻井泵目前广泛使用的是三缸单作用往复泵(简称三缸泵)。三缸泵虽然在压力和流量上基本满足现代海洋石油开采的需要,但是其采用曲柄连杆机构驱动,存在重量大、流量波动大、效率低、功能部件寿命短等缺点,通常采用恒定转速运行,无法根据实际工况需求进行调整,容易导致频率控制失稳。为此,提出一种海洋石油钻井泵自动变频调试方法。通过对钻井泵提升过程的转速变化进行分析,建立矢量分析数据,以判断变频控制要素。根据石油钻井泵电机的额定输出功率来确定最大消耗功率频率,通过匹配电机功率和泵轴功率的关系来调节变频控制要素,以实现频率最大化。利用相似定律和经验值估算法进行频率变化修正,确保钻机在最佳频率范围内运行。实验结果表明:所提方法能够有效实现钻井泵的变频调速,保证海洋石油钻井作业的稳定运行。

汽车ABS模糊变结构控制设计

针对汽车制动过程中防抱死制动系统(ABS)存在的难以充分利用地面附着系数和高度非线性的问题,提出了一种基于路面识别的ABS模糊变结构控制策略。利用Burckhardt轮胎模型设计路面识别算法,并通过模糊变结构控制调节路面识别算法识别出的最优滑移率。仿真实验结果表明,路面识别算法响应速度快、准确率高;在跃变路面条件下,模糊变结构控制比变结构控制的制动时间减少7%,制动距离缩短6%,控制器输出的抖振幅度得到有效削弱.

双风机变风量空调系统

早期的变风量空调系统设计只配备1台风机(送风机),而随着变风量空调系统的发展,越来越多的变风量空调系统设计配备了1对风机,即送风机+回风机或送风机+排风机。本文从理论上解释了为什么配备回风机或排风机的双风机系统设计比只配备1台送风机的单风机系统设计节能,并分析了双风机设计的优缺点,论述了如何设计和控制双风机变风量空调系统。

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。

机械式前轮主动转向系统的原理与应用

以宝马轿车上选装的主动转向系统为例,详细介绍了该系统的组成、双行星齿轮机构的结构及工作模式,以及该系统可变传动比、稳定车辆等功能的实现原理和系统安全性设计。指出通过与其他动力学控制系统一起实现底盘一体化集成控制将是主动转向技术未来的发展方向。

基于LQR变传动比控制的4WIS电动车转向控制仿真研究

理想转向特性对改善车辆操纵稳定性有重要意义。本文中基于LQR最优控制理论,提出了一种新型后轮主动转向变传动比控制策略。首先,综合考虑低速操纵响应性与高速行驶稳定性,建立4WIS电动车理想转向特性;接着根据变传动比曲线设计预期的横摆角速度,并基于LQR最优控制理论提出了主动后轮转向控制策略,以跟踪横摆角速度的预期值;最后,针对典型的双移线工况,进行人车路闭环控制仿真,结果表明,所提出的控制策略较好地实现了理想转向特性。

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 。