车辆工程专业毕业论文外文翻译1doc.docx

1、车辆工程专业毕业论文外文翻译1docDrive force control of a parallel-series hybrid systemAbstractSince each component of a hybrid system has its own limit of performance, the vehicle power depends on the weakest component. So it is necessary to design the balance of the components. The vehicle must be controlled to

2、operate within the performance range of all the components. We designed the specifications of each component backward from the required drive force. In this paper we describe a control method for the motor torque to avoid damage to the battery, when the battery is at a low state of charge. Society o

3、f Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.1. IntroductionIn recent years, vehicles with internal combustion engines have increasingly played an important role as a means of transportation, and are contributing much to the development of society. However, veh

4、icle emissions contribute to air pollution and possibly even global warming, which require effective countermeasures. Various developments are being made to reduce these emissions, but no further large improvements can be expected from merely improving the current engines and transmissions. Thus, gr

5、eat expectations are being placed on the development of electric, hybrid and natural gas-driven vehicles. Judging from currently applicable technologies, and the currently installed infrastructure of gasoline stations, inspection and service facilities, the hybrid vehicle, driven by the combination

6、of gasoline engine and electric motor, is considered to be one of the most realistic solutions. Generally speaking, hybrid systems are classified as series or parallel systems. At Toyota, we have developed the Toyota Hybrid System (hereinafter referred to as the THS) by combining the advantages of b

7、oth systems. In this sense the THS could be classified as a parallel-series type of system. Since the THS constantly optimizes engine operation, emissions are cleaner and better fuel economy can be achieved. During braking, Kinetic energy is recovered by the motor, thereby reducing fuel consumption

8、and subsequent CO2 emissions. Emissions and fuel economy are greatly improved by using the THS for the power train system. However, the THS incorporates engine, motor, battery and other components, each of which has its own particular capability. In other words, the driving force must be generated w

9、ithin the limits of each respective component. In particular, since the battery output varies greatly depending on its level of charge, the driving force has to be controlled with this in mind.This report clarifies the performance required of the respective THS components based on the driving force

10、necessary for a vehicle. The method of controlling the driving force, both when the battery has high and low charge, is also described.2. Toyota hybrid system (THS) 1,2As Fig. 1 shows, the THS is made up of a hybrid transmission, engine and battery.2.1. Hybrid transmissionThe transmission consists o

11、f motor, generator, power split device and reduction gear. The power split device is a planetary gear. Sun gear, ring gear and planetary carrier are directly connected to generator, motor and engine, respectively. The ring gear is also connected to the reduction gear. Thus, engine power is split int

12、o the generator and the driving wheels. With this type of mechanism, the revolutions of each of the respective axes are related as follows. Here, the gear ratio between the sun gear and theFig. 1. Schematic of Toyota hybrid system (THS).ring gear is :where Ne is the engine speed, Ng the generator sp

13、eed and Nm the motor speed. Torque transferred to the motor and the generator axes from the engine is obtained as follows: where Te is the engine torque.The drive shaft is connected to the ring gear via a reduction gear. Consequently, motor speed and vehicle speed are proportional. If the reduction

14、gear ratio is, the axle torque is obtained as follows: where Tm is the motor torque.As shown above, the axle torque is proportional to the total torque of the engine and the motor on the motor axis. Accordingly, we will refer to motor axis torque instead of axle torque.2.2. EngineA gasoline engine h

15、aving a displacement of 1.5 l specially designed for the THS is adopted 3. This engine has high expansion ratio cycle, variable valve timing system and other mechanisms in order to improve engine efficiency and realize cleaner emissions. In particular, a large reduction in friction is achieved by se

16、tting the maximum speed at 4000 rpm (=Ne max).2.3. BatteryAs sealed nickel metal hydride battery is adopted. The advantages of this type of battery are high power density and long life. this battery achieves more than three times the power density of those developed for conventional electric vehicle

17、s 4.3. Required driving force and performanceThe THS offers excellent fuel economy and emissions reduction. But it must have the ability to output enough driving force for a vehicle. This section discusses the running performance required of the vehicle and the essential items required of the respec

18、tive components. Road conditions such as slopes, speed limits and the required speed to pass other vehicles determine the power performance required by the vehicle. Table 1 indicates the power performance needed in Japan.3.1. Planetary gear ratioThe planetary gear ratio () has almost no effect on fu

19、el economy and/or emissions. This is because the required engine power (i.e. engine condition) depends on vehicle speed, driving force and battery condition, and not on the planetary gear ratio. Conversely, it is largely limited by the degree of installability in the vehicle and manufacturing aspect

20、s, leaving little room for design. In the currently developed THS, =0.385. 3.2. Maximum engine powerSince the battery cannot be used for cruising due to its limited power storage capacity, most driving is reliant on engine power only. Fig. 2 shows the power required by a vehicle equipped with the TH

21、S, based on its driving resistance. Accordingly, the power that is required for cruising on a level road at 140 km/h or climbing a 5% slope at 105 km/h will be 32 kW. If the transmission loss is taken into account, the engine requires 40 kW (=Pe max) of power. The THS uses an engine with maximum pow

22、er of 43 kW in order to get good vehicle performance while maintaining good fuel economy.3.3. Maximum generator torqueAs described in Section 2, the maximum engine speed is 4000 rpm (=Ne max). To attain maximum torque at this speed, maximum engine torque is obtained as follows:From Eq. (3), the maxi

23、mum torque on the generator axis will be as follows:This is the torque at which the generator can operate without being driven to over speed. Actually, higher torque is required because of acceleration/deceleration of generator speed and dispersion of engine and/or generator torque. By adding 40% to

24、rque margin to the generator, the necessary torque is calculated as follows:3.4. Maximum motor torqueFrom Fig. 3, it can be seen that the motor axis needs to have a torque of 304 Nm to acquire the 30% slope climbing performance. This torque merely balances the vehicle on the slope. To obtain enough

25、starting and accelerating performance, it is necessary to have additional torque of about 70 Nm, or about 370 Nm in total.From Eq. (2), the transmitted torque from the engine is obtained as follows:Consequently, a motor torque of 300 Nm (=Tm max) is necessary.3.5. Maximum battery powerAs Fig. 2 show

26、s, driving power of 49 kW is needed for climbing on a 5%slope at 130 km/h. Thus, the necessary battery power is obtained by subtracting the engine-generated power from this. As already discussed, if an engine having the minimum required power is installed, it can only provide 32 kW of power, so the

27、required battery power will be 17 kW. If the possible loss that occurs when the battery supplies power to the motor is taken into account, battery power of 20 kW will be needed. Thus, it is necessary to determine the battery capacity by targeting this output on an actual slope. Table 2 lists the req

28、uired battery specifications.Table 3 summarizes the specifications actually adopted by the THS and the requirements determined by the above discussion. The required items represent an example when minimum engine power is selected. In other words, if the engine is changed, each of the items have to b

29、e changed accordingly.4. Driving force controlThe THS requires controls not necessary for conventional or electric vehicles in order to control the engine, motor and generator cooperatively. Fig. 4 outlines the control system.Fig. 4. Control diagram of the THS.Inputs of control system are accelerato

30、r position, vehicle speed (motor speed), generator speed and available battery power. Outputs are the engine-required power, generator torque and motor torque.First, drive torque demanded by the driver (converted to the motor axis) is calculated from the accelerator position and the vehicle speed. T

31、he necessary drive power is calculated from this torque and the motor speed. Required power for the system is the total of the required drive power, the required power to charge the battery and the power loss in the system. If this total required power exceeds the prescribed value, it becomes requir

32、ed engine power. If it is below the prescribed value, the vehicle runs on the battery without using the engine power. Next, the most efficient engine speed for generating engine power is calculated; this is the engine target speed. The target speed for the generator is calculated using Eq. (1) with engine target speed and motor speed. The generator torque is determined by PID control. Engine torque can be calculated in reverse by using Eq. (3) and the torque transferred from the engine to the motor axis can be calculated from (2). The motor torque is obtained by