An investigation of energy efficiency of a wheel loader with automated manual transmission

This paper describes an investigation of energy efficiency by applying an advanced powertrain system in a conventional wheel loader. A conventional powertrain of a wheel loader consists of an engine, torque converter and transmission. A torque converter in a conventional system generally causes a significant amount of energy loss, as determined by analyzing energy flow based on V-pattern working. To prevent energy loss in a torque converter, Automated manual transmission (AMT) was proposed and modeled in this paper as an advanced powertrain. A wheel loader based on AMT does not need to use a torque converter since the single clutch system is used between the engine and transmission with subsystems of engine controller, clutch actuator and controller. A simplified single clutch system and controller were constructed for V-pattern working of a wheel loader. Additionally, a PI-controller was used as a control algorithm for engine speed control to prevent energy loss while the clutch is not engaged. All simulation models have been constructed in the Matlab/ Simulink environment, and simulation studies were conducted by using a simulation model of a wheel loader with a driver model based on V-pattern working. Simulation results of the AMT-based wheel loader were analyzed by comparison with the results of the torque converter-based wheel loader, and the results show that the AMT-based wheel loader is more energy efficient than the conventional wheel loader.     

干式DCT双离合器联合起步最优协调控制

基于自主开发的6速干式双离合器自动变速器(Dual clutch transmission, DCT),提出基于极小值原理的双离合器联合起步过程发动机和双离合器转矩协调最优控制算法。在起步滑摩阶段,以滑摩功和冲击度为性能指标,在反映驾驶员意图的终端约束下,采用极小值原理和改进的发动机恒转速控制,研究并确定起步过程中双离合器,发动机转矩及其转速。根据起步控制目标,确定分离离合器分离条件和离合器的转矩分配关系。在需求转矩切换阶段,将发动机输出转矩平滑切换到驾驶员需求转矩。在Matlab/Simulink软件平台上,搭建DCT车辆双离合器联合起步控制仿真模型,对不同驾驶意图和起步档位下DCT车辆的起步过程进行仿真。结果表明,所提出的基于极小值原理的发动机和双离合器转矩协调控制策略,有效地保证双离合器联合起步品质,反映起步意图,延长离合器使用寿命。将所得的离合器最优转矩控制律转化为离合器位置控制律,在离合器伺服控制试验台架上进行离合器位置闭环控制,得到较好的跟踪效果。     

自动离合器液压执行机构正向设计方法

以电控机械式自动变速系统为研究对象,建立了自动离合器液压执行机构的正向设计方法。结合离合器控制策略获取离合器执行机构控制目标;以膜片弹簧载荷变形特性为依据计算出执行机构设计的边界条件;完成了液压执行机构主要部件的参数设计及控制算法的制定。仿真结果表明,所设计的执行机构能够准确快速地跟踪目标接合位移,误差小于10%。     

干式离合器台架执行机构模糊滑模控制

基于五速干式DCT,搭建了干式离合器台架执行机构,考虑其非线性时变特征,设计了滑模变结构控制器,并利用模糊控制器实时补偿负载转矩同时调整滑模趋近律参数,以提高控制精度同时削弱滑模变结构控制稳态的抖振现象。结合双离合器式自动变速器(DCT)的起步与换挡过程,进行了硬件在环仿真试验。     

Research on intelligent launching control of dual clutch transmissions based on adaptive neural fuzzy inference system

Vehicle launching has an important influence on driving performance of the vehicle. For vehicles with dual clutch transmissions (DCT), the clutch torque control is the key to the launching control. Therefore, a data-driven control method for DCT launching process based on adaptive neural fuzzy inference system (ANFIS) is proposed. Firstly, the vehicle test data during launching process is collected and the optimal clutch torque is obtained based on multi-objective particle swarm optimization (MOPSO). Afterward, to learn the launching control rules from optimization results, the combination of neural network and fuzzy logic algorithm, referred to as an ANFIS, is established. The dataset of the optimized launching clutch torque is utilized to train the ANFIS controller. Finally, the simulation and test results show that the data-driven control can accurately learn the launching control rules from the optimality, thereby achieving the optimal control for different launching intentions.

     

Friction coefficient, torque estimation, smooth shift control law for an automatic power transmission

For shift quality improvement, torque sensors are currently too expensive to be used on production vehicles. To achieve smooth acceleration shift, the reference trajectory of the clutch slip speed for accomplishing the shift process within a designated shift completion time and its relationship with the clutch actuating torque were suggested by Jeong and Lee (1999). In order to facilitate the proposed algorithm, nonlinear estimators for necessary information such as the axle shaft torque, clutch friction and turbine torque were designed using only speed sensors. Accounting for the modeling error, a control law for this indirect smooth shift was proposed based on the above mentioned suggestions. Simulation results of the proposed estimators and shift controller were presented and further considerations for practical applications are discussed.     

Iterative learning control for the filling of wet clutches

This paper discusses the development of an advanced iterative learning control (ILC) scheme for the filling of wet clutches. In the presented scheme, the appropriate actuator signal for a new clutch engagement is learned automatically based on the quality of previous engagements, such that time-consuming and cumbersome calibrations can be avoided. First, an ILC controller, which uses the position of the piston as control input, is developed and tested on a non-rotating clutch under well controlled conditions. Afterwards, a similar strategy is tested on a rotating set-up, where a pressure sensor is used as the input of the ILC controller. On a higher level, both the position and the pressure controller are extended with a second learning algorithm, that adapts the reference position/pressure to account for environmental changes which cannot be learned by the low-level ILC controller. It is shown that a strong reduction of the transmitted torque level as well as a significant shortening of the engagement time can be achieved with the developed strategy, compared to traditional time-invariant control strategies.     

Model reference self-learning fuzzy control method for automated mechanical clutch

Automated mechanical clutch is a critical component in vehicle powertrain, whose operations have great influence on fuel economy, comfort, and drivability. However, the control of clutch is a challenging problem due to the nonlinearities and uncertainties, which has attracted extensive attention. This paper proposed a model reference self-learning fuzzy control method with considering clutch wear. Fuzzy control is a simple but effective method to deal with the nonlinear system, but the determined fuzzy rules cannot be suitable for system variations due to clutch wear. Therefore, a self-learning algorithm based on referent model is introduced into fuzzy controller. Then, simulations are carried out in MATLAB/SIMULINK, and the results show that the method solves the problem of clutch wear effectively compared with the fuzzy control without self-learning ability. Finally, a test bench is designed and experiments are carried out to verify the validity of the proposed method.     

Dynamic analysis and control strategy of wet clutches during torque phase of gear shift

Control over the clutch during gear shift is the key technique in automatic transmission shift control and this control largely decides the shift quality. The engagement of the on-coming clutch and the disengagement of the off-going clutch should be controlled synchronously and accurately to achieve a smooth shift. Optimal control of clutch torque exchange phase is required to achieve this synchronous and accurate control. Shift quality can be easily influenced with inappropriate control parameters because of the many factors that affect the torque phase, as well as the use of closed-loop control. In this study, a dynamic model of frictional clutch with electro-hydraulic shift control is built. On the basis of the study of the influence of clutch-related parameters, an optimal control model is proposed with the closed-loop control together with an adaptive control method based on micro-slip clutch control. This control method can continually self-adjust control parameters to prevent shock, improve control precision and effectively reduce the calibration work after. Test result shows that this closed loop with adaptive method ensures consistently good shift quality.     

Control of gear shifts in dual clutch transmission powertrains

To achieve the best possible responses during shifting in dual clutch transmissions it is commonplace to integrate clutch and engine control, while the clutch is used to match speeds between the engine and wheels via reduction gears, poor engine control can lead to extended engagement times and rough/harsh shift transients. This paper proposes a method for combined speed and torque control of vehicle powertrains with dual clutch transmissions for both the engine and clutches. The vehicle powertrain is modelled as a simple four degree of freedom system with reduction gears and two clutches. Including a detailed clutch hydraulic model, comprising of the direct acting solenoids and clutch piston with the hydraulic fluid modelled as a compressible fluid. Powertrain control is realised through control of clutch solenoids and manipulation of the engine throttle input. Sensitivity study of clutch performance evaluating inaccurate torque estimation demonstrated variance in the response of the hydraulic system, with an indicative simulation of poor estimation resulting in increased powertrain vibration during and after shifting. Simulations are conducted to demonstrate the capacity for this method of engine and clutch control to further reduce shift transients developed in dual clutch transmission powertrains. The obtained results also show that the adoption of torque based control techniques for both the clutch and engine, which makes use of the estimated target clutch torque, significantly improves the powertrain response as a result of reduction in the lockup discontinuities.     

分形特征在湿式离合器磨合状态预测中的运用

针对湿式离合器试验过程中磨合状态的预测问题,提出利用摩擦转矩信号分形特征来预测和评价磨合状态的新方法.首先,分别阐述了摩擦转矩信号盒子维数和关联维数的计算方法;然后,在湿式离合器试验台上提取了磨合试验的摩擦转矩信号,并对信号进行了自相似性分析;最后,应用盒子维数和关联维数分别对摩擦转矩信号进行了分形研究.分析结果表明:盒子维数和关联维数都能定量描述试验过程中摩擦转矩信号的分形特征,随着磨合次数的增加,摩擦转矩信号的盒子维数和关联维数的波动范围都逐渐减小,并且最终收敛于较小的波动范围.因此,利用试验中摩擦转矩信号的分形特征能够在不开箱条件下定量地预测和评价湿式离合器的磨合状态.     

基于无级变速器的混合动力汽车动态模式切换研究

对基于无级变速器的混合动力系统的结构及其工作模式进行分析,建立了动力学模型。针对伴随发动机启动的混合动力模式切换问题,提出了一种模糊推理与最优控制理论相接合的综合控制策略。首先基于驾驶意图采用模糊控制得到离合器接合时长,然后基于动力学模型采用动态规划得到离合器的最优传递转矩和发动机的最优目标转矩,再根据离合器最优传递转矩利用电机的快速响应性来实时调整电机输出转矩。通过试验对上述模式切换控制策略进行了验证。试验结果表明：该策略能够优化离合器滑摩时间,体现驾驶意图,实现模式切换的平顺性。     

四轮轮毂电机驱动智能电动汽车转向失效容错控制研究

四轮轮毂电机驱动电动汽车各轮驱动力矩独立可控,可通过控制前轴左右两轮的力矩差实现前轮转向。以四轮轮毂电机驱动智能电动汽车为研究对象,针对线控转向系统执行机构失效时的轨迹跟踪和横摆稳定性协同控制问题,提出一种基于差动转向与直接横摆力矩协同的容错控制方法。该方法采用分层控制架构,上层控制器首先基于时变线性模型预测控制方法求解期望前轮转角和附加横摆力矩,然后考虑转向执行机构建模不确定性以及路面干扰,设计基于滑模变结构控制的前轮转角跟踪控制策略。下层控制器以轮胎负荷率最小化为目标,利用有效集法实现四轮转矩优化分配。最后,分别在高速换道和双移线工况下仿真验证了该控制方法的有效性和实时性。     

OPTIMAL TORQUE CONTROL STRATEGY FOR PARALLEL HYBRID ELECTRIC VEHICLE WITH AUTOMATIC MECHANICAL TRANSMISSION

In parallel hybrid electrical vehicle (PHEV) equipped with automatic mechanical transmission (AMT), the driving smoothness and the clutch abrasion are the primary considerations for powertrain control during gearshift and clutch operation. To improve these performance indexes of PHEV, a coordinated control system is proposed through the analyzing of HEV powertrain dynamic characteristics. Using the method of minimum principle, the input torque of transmission is optimized to improve the driving smoothness of vehicle. Using the methods of fuzzy logic and fuzzy-PID, the engaging speed of clutch and the throttle opening of engine are manipulated to ensure the smoothness of clutch engagement and reduce the abrasion of clutch friction plates. The motor provides the difference between the required input torque of transmission and the torque transmitted through clutch plates. Results of simulation and experiments show that the proposed control strategy performs better than the contrastive control system, the smoothness of driving and the abrasion of clutch can be improved simultaneously.     

单摩擦元件纯电动两档变速器换档最优控制*

针对单摩擦元件纯电动两档变速器的动力换档过程,提出基于极小值原理的双控制变量换档协调优化控制策略。在转矩相阶段,对整车进行稳定加速度控制;在惯性相阶段,构造目标泛函兼顾末时刻点的冲击度和过程中的滑摩功,以电动机、摩擦元件转矩变化率为控制变量,并根据过程中的容许冲击度对控制变量施加约束,针对该带约束条件的波尔扎问题,利用极小值原理最优控制算法求解电动机、摩擦元件的最优状态变化轨迹。在Matlab/Simulink软件平台上搭建换档控制仿真模型,验证自由边界条件下的双控制变量优化控制策略的可行性。并将该换档策略应用于所搭建的试验台架上,换档试验结果表明其能有效地提高换档品质,延长摩擦元件的使用寿命。     

基于等效BSFC和电池SOC平衡的插入式混合动力汽车分段式能量分配策略研究

基于所提出的插入式并联混合动力汽车系统结构,对整车动力/传动系统(包括发动机、电机、电池、离合器、变速箱等子系统)进行了动态精确建模,模拟了行车换挡过程中同步器切换、离合器接合/分离等瞬态过程。根据电池SOC值分段采用最大用电策略或效率优先策略,提出了基于等效BSFC和电池SOC平衡的分段式能量分配策略,兼顾了发动机BSFC和电机充/放电效率,实现了系统在当前转速和输入轴需求转矩下的最佳转矩分配。结果表明,所提出的能量分配策略在不牺牲汽车各项性能的前提下,提高了动力系统工作效率和整车燃油经济性。     

双离合器变速箱换档动力学和控制

依据包含一双离分器变速箱的汽车动力传动系统的详细动力模型开发了一个集成的动力传动系的换档控制.基于换高档和换低档以及发生于变速箱相同一部分的换档控制的仿真结果证实了该控制器的工作.采用带有再现单向离合离工作目标为均匀传递发动机转矩离合器滑动的闭环控制制订了控制法则,进一步的要素是通过发动机控制和离合器压力操纵的组合对发动机速度的闭环控制.此外,它证实了变速箱换档时输出转矩的控制可增加控制的持久性以及提供了直接操纵换档品质的方法.最后讨论了通过方便的液力传动锥型同步器在总换档质量方面予选换档的动力影响.     

DCT车辆起步及换挡过程双离合器H∞鲁棒控制

根据自主研发的双离合器自动变速器（DCT）结构和工作原理,建立了DCT车辆起步及换挡过程动力学模型。考虑起步及换挡过程中发动机扭矩波动及油门踏板抖动等不确定性因素,基于Riccati不等式和线性矩阵不等式设计了H∞鲁棒控制器,分析了冲击度和滑摩功两项离合器接合性能指标,探讨了离合器最优传递扭矩的求解问题,并与线性二次型最优控制策略进行了仿真对比分析,结果表明：H∞鲁棒控制可以较好地解决DCT车辆起步与换挡过程离合器压力控制问题,并能显著地改善离合器控制的鲁棒性能。     

平面并联机构的自适应控制方法研究

针对并联机构的动力学模型有很强的非线性,模型参数不易获得,基于运动学的控制或PID闭环控制方法适应性差、精度低的不足,提出了一种以计算力矩结构为基础的改进的自适应控制方法,利用驱动铰的理想值进行逆动力学计算,在驱动空间上计算反馈力矩。在分析一个平面冗余链并联机构的动力学模型后,给出了几种算法的对比实验结果,实验结果表明,所提出方法能获得更小的跟踪误差,具有更好的适应性。     

Validation of dynamic torque response of an electrorheological (ER) clutch

It is now well established that using actuators, which have faster speeds of response than d.c. servomotors, can solve the positional errors of the robot arms. One of the possible robotic actuators can be an electro-rheological (ER) clutch. To justify this objective, the authors measured the output torque response of a co-axial ER clutch. However, due to the dynamic inefficiency of a torque transducer, the measured torque response is inaccurate for analytical studies. Therefore, this measured torque is signal processed by using the transfer functions of this torque sensor and a filter to yield the ER torque response. The validity of this ER torque is investigated by comparing the numerical errors between the measured torque and its inverse torque response. From the torque error analysis, it is concluded that the ER clutch can be an actuator to improve the positioning accuracies of the robot arms.