Model-Based Integrated Control of Engine and CVT to Minimize Fuel Use

In this study, a model-based integrated control method for engines and continuous variable transmissions (CVTs) is developed. CVT refers to a type of transmission which allows an engine to be operated independently with respect to the vehicle speed, with the engine torque and CVT gear ratio controlled in an integrated manner. In the proposed integrated control scheme, engine operating points which minimize the rate of instantaneous fuel consumption are calculated, and the engine target torque and target gear ratio are determined in an integrated manner based on the results of the calculations. Unlike the previous map-based control method, the method introduced in this study does not require an engine torque map or a CVT ratio map for tuning, and the engine torque and CVT ratio are controlled to minimize the amount of fuel used while satisfying the level of acceleration demand from the driver. The control scheme is based on the powertrain model, and the CVT response lag and transmission loss are also considered in the integrated control processes. The algorithm is simulated with various driving cycles, with the simulation results showing that the fuel economy performance of the vehicle system is improved with the newly suggested engine-CVT integrated control algorithm.     

Development of dry hybrid belt CVT

We have developed a continuously variable transmission (CVT) which has superior transfer efficiency, by thoroughly reducing transfer loss by means of using a dry hybrid belt, using no lubrication composition system around the belt, and using an electric control system of a DC motor.The fuel efficiency and driveability of the prototype vehicle equiped with the CVT were proven equivalent or even superior to a 5 speed manual transmission.     

金属带式CVT速比控制的仿真与试验研究

针对装备金属带式无级变速器(CVT)的整车,建立了无级变速传动系统数学模型.以无级变速汽车动力性和经济性相协调为目标,设计了Fuzzy-PI复合速比控制器.采用Fuzzy-PD控制策略和Fuzzy-PI复合控制策略对汽车起动工况进行了仿真分析,对装备金属带式CVT的某轿车进行了起动工况的模拟试验.结果表明,Fuzzy-PI复合控制策略优于Fuzzy-PD控制策略,速比的试验结果与理论数据一致,说明所建模型合理.     

基于遗传算法系统效率优化的PHEV电量保持模式控制策略

为了提高插电式混合动力汽车（PHEV）在电量保持下的燃油经济性,并解决插电式混合动力汽车在运行过程中动力元件效率对系统能量利用率影响的问题,制定了系统效率最优的控制策略。以PHEV关键动力部件的测试数据为基础,建立发动机、驱动电机、无级变速器（CVT）以及动力电池等关键部件的效率数值模型,并考虑了温度及荷电状态（SOC）对动力电池充放电功率的影响。设计以混合动力系统效率最优为适应度评价函数,将CVT速比、发动机转矩作为优化变量,以车速、加速度和SOC为状态变量,在动力性指标的约束下,运用遗传算法进行迭代寻优,PHEV的系统效率在第20代左右收敛于全局最优值。同时发动机转矩和CVT速比通过多代遗传进化,较快收敛于最佳值。将相关优化结果与车速、加速度拟合成相应的三维控制数表,综合数值建模和试验测试数据建模的方法,基于MATLAB/Simulink搭建插电式混合动力汽车整车控制策略仿真模型,采用新欧洲行驶循环工况进行仿真验证。结果表明：插电式混合动力汽车在电量保持模式下,利用遗传算法优化的系统效率最优控制策略相比优化前,动力电池SOC运行更为平稳,CVT效率有所提升,驱动电机及发动机转矩分配更为合理;百公里燃油消耗量从优化前的5.2 L降至4.5 L,燃油经济性提升了13.5%。     

CVT混合动力汽车再生制动控制策略与仿真分析

分析了混合动力汽车制动过程中发动机反拖制动和CVT速比控制对车辆再生制动性能的影响,提出了低制动强度下仅由电机再生制动、高制动强度下电机与制动器共同制动和紧急制动时发动机参与制动的再生制动策略。对典型工况进行了再生制动仿真,仿真结果表明,CVT速比控制可使电机运行在高效区,从而获得了比传统手动变速混合动力汽车更好的制动能量回收效果。     

PHEV发动机驱动工况效率耦合分析与优化控制

单轴并联式混合动力系统（Parallel Hybrid Electric Vehicle，PHEV）包括电池、驱动电机、发动机、自动变速器等多个关键部件。各部件效率特性存在相互耦合的关系，要实现系统整体效率最优，需要辨明影响系统效率的控制参数，并对系统整体效率最优的控制参数进行优化。以装备无级变速器（Continuously Variable Transmission，CVT）的PHEV为研究对象，首先对系统各关键部件的效率特性进行分析，建立各关键部件效率模型，明确各部件效率与控制参数、状态参数之间的关系。在此基础上，对发动机单独驱动模式下动力传递路径中不同部件的效率耦合关系进行分析，推导出系统燃油消耗量与动力系统各状态参数、控制参数之间的函数关系。根据分析结果，选取车辆需求功率及车速为状态参数，变速器速比及发动机转矩为控制参数，以系统燃油消耗量最小为目标建立优化目标函数和约束条件，对系统优化问题进行定义。根据优化问题的特点，设计基于模拟退火的优化算法对优化问题进行求解，获取系统燃油消耗率最小时变速器目标速比和发动机目标转矩随状态参数的变化关系。建立系统仿真模型对所述优化算法进行仿真分析，并搭建混合动力试验台对优化结果进行试验验证。结果表明：无级变速器效率对系统整体效率影响较大，采用优化控制规律使发动机效率有所降低，但无级变速器效率升高更大，系统整体效率升高；在功率需求一定的循环工况下，优化控制算法比传统上仅以发动机效率最高为目标的控制算法节油1%~2%。     

Engine-CVT consolidated control using LQI control theory

For the drivetrain control, it has become important for fuel economy or AHS to control the throttle valve of the engine and the gear ratio of CVT simultaneously by DBW when the automobile is equipped with CVT. In this paper, LQI control theory was applied to control the drivertrain as a 2-I/O system to satisfy the demanded speed and better fuel economy. Moreover, modification of the weight parameter of LQI was investigated to obtain the desired performance for fuel economy or vehicle acceleration. Relatively good results were obtained.     

基于系统效率最优的CVT混合动力轿车转矩优化分配方法

无级变速器CVT消除了挡位概念,其速比在一定范围内连续可调。配备CVT的混合动力汽车能够实现动力源转矩和传动系统的优化匹配。针对此问题,提出了基于系统效率最优的CVT中度混合动力轿车动力源转矩优化分配方法:。该方法:综合考虑了各个关键部件的效率,以混合动力系统的总体效率为优化目标,以车速、车辆加速度、电池SOC为状态变量,优化分配了驱动工况下各动力源输出转矩,为整车能量管理策略的制定奠定了基础。     

压力钢带式无级变速器技术降低油耗的潜能分析(一)

为降低压力钢带式无级变速(CVT)车型的燃油消耗,将研究重点放在对其内部不同损耗源的分析上,并认为最有可能降低损耗的部分是压力钢带式CVT的变速机构、液压驱动回路及其控制策略。根据研究结果指出,通过采取诸如滑移控制、改进的液压回路、分离离合器或启动-停止控制等措施,压力钢带式CVT仍具有较大的降低油耗的潜力;今后的工作应着重于扩大CVT滑移控制的工作区域及将此功能应用于生产实际中。。     

Experimental investigation on the efficiency of the pulley-drive CVT

Because of their outstanding advantages over other transmissions, rubber V-belt pulley drive CVTs have been extensively used in low-power vehicles, such as scooters and snowmobiles. A rubber V-belt CVT installed on a snowmobile is used here to research transmission efficiency. The power loss of CVTs, including torque loss and speed loss, is studied based on an analysis of the transmission mechanism of CVTs. Experiments on CVT efficiency are conducted on a specific CVT test bench, on which the values of torque, speed, and displacement, etc., are measured. Results show that the variation trend of the efficiency is close to the operating conditions of CVTs and optimal structural parameters are given that can serve as a beneficial references for designing and tuning CVTs.     

The Horsepower Reserve Formulation of Driveability for a Vehicle Fitted With a Continuously Variable Transmission

Summary A systematic methodology is developed for choosing the optimum ratio trajectory of a continuously variable transmission in a passenger vehicle. The optimum CVT ratio schedule is formulated as a constrained optimization problem with maximum fuel economy as the objective function and driveability concerns and physical limitations included as the constraints. The key notion to achieving good driveability is the introduction and definition of a horsepower reserve function that creates a consistent and desirable vehicle response under different driving conditions. Simulation results compare the optimized schedule's performance with several other possible ratio schedules, including the minimum brake specific fuel consumption map. Results from the optimized schedule indicate only a mild tradeoff between driveability and fuel economy relative to the other ratio schedules. The ratio optimization problem formulation and solution provide a novel and unique approach for systematically addressing driveability and fuel economy considerations associated with a continuously variable transmission.     

Simulation Approach to the Effect of the Ratio Changing Speed of a Metal V-Belt CVT on the Vehicle Response

In regard to the belt and pulley system of a metal V-belt CVT, the characteristics of the ratio changing speed is obtained by experiments. It is summarized in a practical and simple experimental equation. By using this equation a simulation model is developed to analyze the response of a vehicle with a metal V-belt CVT to a rapid pulley ratio change. The simulation results are in reasonable agreements with experimental results.     

Development of a high torque capacity belt-drive CVT with a torque converter

A new belt-drive continuously variable transmission (CVT) has been developed and installed in a 2-liter class vehicle for the first time in the world. This paper describes the technical features of this high torque capacity transmission, the need for a torque converter, the importance of electronic control and the driving modes achieved. This new CVT provides better driving performance and fuel economy than current CVTs and 4-speed automatic transmissions.     

Simulation Approach to the Effect of the Ratio Changing Speed of a Metal V-Belt CVT on the Vehicle Response

SUMMARY

In regard to the belt and pulley system of a metal V-belt CVT, the characteristics of the ratio changing speed is obtained by experiments. It is summarized in a practical and simple experimental equation. By using this equation a simulation model is developed to analyze the response of a vehicle with a metal V-belt CVT to a rapid pulley ratio change. The simulation results are in reasonable agreements with experimental results.     

Multi-objective geometrical optimization of full toroidal CVT

The objective of this research is geometrical and kinematical optimization of full-toroidal continuously variable transmission (CVT) in order to achieve high power transmission efficiency and low mass. At first, a dynamic analysis is performed for the system. A computer model is developed to simulate elastohydrodynamic (EHL) contact between disks and roller and consequently, calculate CVT efficiency. The validity of EHL model is investigated by comparing output of this model and experimental data. Geometrical parameters are obtained by means of Particle Swarm Optimization algorithm, while the optimization objective is to maximize CVT efficiency and minimize its mass. The algorithm is run for different values of selected input parameters that are oil temperature, roller tilting angle (speed ratio). Optimization results show that optimized geometrical parameters are approximately constant for various values of input parameters. Also, it is observed that, increasing values of oil temperature and roller tilting angle (in clockwise direction), will decrease power transmission efficiency. An average power transmission efficiency of 86.7% is achieved over a wide range of input parameters, using optimized geometry.     

无级变速传动系统综合控制仿真与试验

基于无级变速传动系统动力学仿真模型与自适应模糊控制策略,综合考虑后备功率、动力传动系损失和CVT速比变化响应滞后的影响,提出了τ算法、发动机转矩补偿和发动机转速补偿3种控制方法,并分别对采用这3种控制方法时的动力性与燃油经济性进行仿真分析.结果表明,相对于常规控制,采用这3种综合控制方法后动力性基本保持不变,而经济性则分别提高了约2.9%-3.5%.     

Performance Evaluation of Ball CVT and Comparison with Half Toroidal CVT

This study aims at finding an analytical model of ball continuously variable transmission (B-CVT) behavior and performance, based on the existing model of the half-toroidal traction drive. The geometrical and kinematical aspects of this model have been found. Then, force-moment equilibrium equations have been applied for a B-CVT. The contact behavior has been modeled using the isothermal elastohydrodynamic lubrication (EHL) theory, and spin and relative slip losses have been estimated for this CVT. Finally, the overall efficiencies of the B-CVT have been analyzed and compared with the halftoroidal traction drive. This study results have shown that B-CVT has higher torque efficiency and lower speed efficiency in comparison with half-toroidal CVT. Also, it has shown that the adjustment of axial forces in B-CVT leads to higher efficiency in lower input torques.     

CVT轿车发动机建模及PID速比控制器设计

针对装备金属带式无级变速器轿车的发动机建立了其转矩模型和目标转速调节特性曲线。对无级变速器速比的取值范围进行了计算,并按照质量集中法简化了传动系的模型。设计了简单实用的PID速比控制器,并在simulink环境下对CVT整车模型起步、急加速和上坡工况进行了仿真分析。结果表明,实际速比对目标速比有很好的跟随效果。     

Study of fuel consumption improvement of the car with the dry hybrid belt CVT

By reducing transmission loss in the speed-change control system and optimizing the transmission ratio using an electronically controlled DC motor, the authors were able to prove that the dry hybrid belt CVT is more fuel efficient than manual transmissions. This paper describes the results of the transmission-loss analysis and the control method used for the speed-change ratio.     

金属带式无级变速器速比控制的试验研究

基于力-位置控制方案开发了金属带式无级变速器的控制测试系统：在无级变速器的控制系统中，考虑到速比控制阀的饱和非线性特性和无级变速系统的复杂非线性特性，设计了基于速比反馈的速比模糊控制器：试验结果表明，所设计的液压控制系统是可行和实用的。