汽车专业英语Word

　　Control of gear shifts in dual clutch transmission powertrains班级：研1501班 姓名：王四松 学号：2015020029

　　ABSTRACTTo 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. 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.

　　摘要：在双离合变速器换档期间，为了获得最好的换挡响应，通常要用到发动机和 离合器共同控制。离合器通过减速器来匹配发动机和车轮的速度。发动机控制不 足将导致换档困难和延长啮合时间。本文研究主要内容 (1) 换档品质评价和影响因素的研究是提高换档品质的基础，本文从双离合 器自动变速器的组成及其原理入手，提出评价标准并对换档品质的影响 因素进行理论分析。 (2) 对双离合器自动变速器的换档的过程建立数学模型，深入分析换档过程 中影响换档品质的因素。 (3) 结合MATLAB软件仿真模块，建立含有双离合器自动变速器的整车模型。

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　　1.IntroductionThe combination of engine and clutch control in modern automated vehicular powertrains aims to deliver tractive driving torque to the road during shift transients in a manner providing high efficiency and excellent ride quality. While good system design can maximise these requirements for general driving, it is the engine and transmission control systems, including clutch hydraulics, which must provide ideal control of clutch and engine speeds and torques to achieve the best possible results during the shift period. This is particularly important for stepped transmission systems such as planetary automatics (AT) and dual clutch transmissions where control of both speed and torque control is required to minimise shift transients.

　　2.Model development2.1 Lumped inertia model(总惯性模型)The development of a reasonable 4DOF finite element model of the dual clutch transmission powertrain uses elements provided for the engine, clutch drum, transmission, and vehicle.

　　The vehicle powertrain parameters of inertia, damping, and stiffness are presented in Table 1.

　　2.2 Clutch modelThe piecewise model of the clutch is defined as a combination of dynamic and static friction where the static friction is calculated as the average torque in the clutch, and limited to the static friction of the clutch.

　　2.3 Vehic

　　le resistance modelThe vehicle resistance torques includes rolling resistance, aerodynamic drag, and incline of the road. This is given as

　　where Mv is vehicle mass, g is gravity, φ is angle of inclination(倾角), Av is vehicle area(迎风面积), CD is drag coefficient(空气阻力系数), V is vehicle speed, ρair is air density, and CT tire friction coefficient.

　　2.4 Hydraulic control system modelEliminated from the control system are the pump, various pressure control and safety valves that have minimal influence on clutch control.

　　Simplified hydraulic system for clutch control.

　　Through mass conservation it is assumed that

　　Then the equation can be solved to determine the transient pressure change. This will be integrated numerically to determine the local pressure in specific control volumes.

　　3.Control system methodology

　　Control logic for gear shift of DCT powertrains.

　　The inertia phase contributes the majority speed synchronisation (同步 )between clutch and drum, with target clutch held at constant torque and the control of engine throttle input aids shifting.

　　4.Simulation results and discussionFor the simulations presented in this paper a general third to fourth gear up-shifts will be employed. Third gear ratio is 4.443 and fourth gear is 3.3912, this includes the transmission reduction gear and final drive gears. The initial vehicle speed is approximately 70 rad/s, equivalent to 80 km/h, resulting in initial engine speeds near 2800 rpm. The final clutch torque is estimated using the average torque in clutch 2 at the point of slip. For this simulation the hydraulic control system is replaced by ideal input torques for the clutches, demonstrating the ideal response of the system.

　　Simulation results for a 3–4 up-shift showing speeds for (a) clutch drum and clutch 2, (b) vehicle acceleration, and (c) clutch pressures during shifting using ideal clutch torques.

　　5.ConclusionsThe development of speed and torque orientated shift control methods for dual clutch transmissions have been presented in this paper. This includes a 4DOF finite element model of the vehicle powertrain and a detailed model of the clutch hydraulics using classical fluid dynamics. The detailed model of the clutch hydraulic system is required to demonstrate realistic responses of clutch control during shift transients. Control methodologies focus on the integration of clutch torque, engine speed and torque control techniques. Simulations using values exceeding nominal were shown to increase vibration in the system above nominal results.

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