Drive force control of a parallel-series hybrid system
Abstract
Since 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 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 of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.
1. Introduction
In 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, vehicle 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, great 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 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 both 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 and subsequent CO 2 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 within 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 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) [1,2]
As Fig. 1 shows, the THS is made up of a hybrid transmission, engine and battery.
2.1. Hybrid transmission
The transmission consists of 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 into the generator and the driving wheels. With this type of mechanism, the
revoluti ons of each of the respective axes are related as follows. Here, the gear ratio betwee n the sun gear and the
—MEJthanical Power
Electrical Powsr
Fig. 1. Schematic of Toyota hybrid system (THS).
ring gear is p :
2-上'
where Ne is the engine speed, Ng the gen erator speed and Nm the motor speed.
Torque tra nsferred to the motor and the gen erator axes from the engine is obta ined as follows:
motor axis torque：二 ------- Te.
r 1 +p
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 proporti on al. If the reducti on gear ratio is n , the axle torque is obta ined as follows:
aide torque : (■-_-—Te + Tm jff. (4(
where Tm is the motor torque.
As show n above, the axle torque is proporti onal to the total torque of the engine and the motor on the motor axis. Accordi ngly, we will refer to motor axis torque in stead of axle torque.
2.2. Engine
A gasoline engine having 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 setting the maximum speed at 4000 rpm (= Ne max).
2.3. Battery
As 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 conven ti onal electric vehicles [4].
3. Required driving force and performance
The THS offers excellent fuel economy and emissions reduction. But it must have the ability to
：2i
Hybrift transmission
output en ough driv ing force for a vehicle. This secti on discusses the running performa nee required of the vehicle and the essential items required of the respective 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 n eeded in Japa n. 3.1. Planetary gear ratio p
The planetary gear ratio (p ) has almost no effect on fuel 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 in stallability in the vehicle and man ufacturi ng aspects, leav ing little room for desig n. In the curre ntly developed THS, p =0.385.
3.2. Maximum engine power
Since the battery cannot be used for cruising due to its limited power storage capacity, most driving is relia nt on engine power only. Fig. 2 shows the power required by a vehicle equipped with the THS, based on its driv ing resista nce. Accord in gly, the power that is required for cruis ing 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 power of 43 kW in order to get good vehicle performance while maintaining good fuel economy.
TjhJe 1
ui red lieitkms Ebr Yfhi 讨己
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RcquiriMi abdiiy CniLsin^ iiminiLjin AbiJal^
lew uphill rc^ad AbUily far
uphill
road 3l higJi speed 30% {11 ) 5% (3 > it 105 km h
5% (3 ) it 130 krn-li nnttintancnuft
33 Maximum gen erator torque
As 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:
1000 x max
l2TT '60f x Ar ma\ From Eq. (3), the maximum torque on the gen erator axis will be as follows:
- --- Te msx = 26-5 (Nm). i + p
2(kJ-
琢.3 Required dnvc torque st the moio-r 日ELE ”
Te mat = 95.5 (Nm).
Vehicle Speed (kni/h} Fig. Z Rirquired drive power.
5% slof>e
I 思啊I Hoad 1 議 0 k
ni/h
105 km/h
Bo 140 km/1
A chicle Sjta^ed (koi/h} 一日
也
.
EH
<
SSN
S nnE-h-.
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 an d/or
gen erator torque. By add ing 40% torque margin to the gen erator, the n ecessary torque is calculated as
follows:
---- Te ma\x. L4 = 7 JTIJK- 37,1 (Nm|. + p
3.4. Maximum motor torque
From Fig. 3, it can be see n that the motor axis n eeds to have a torque of 304 Nm to acquire the 30% slope climb ing performa nee. This torque merely bala nces the vehicle on the slope. To obta in en ough starting and accelerating performanee, 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:
y!—Te max = 70.0 (Nm).
Con seque ntly, a motor torque of 300 Nm (=T m max) is n ecessary.
3.5. Maximum battery power
As Fig. 2 shows, driv ing power of 49 kW is n eeded for climb ing 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 hav ing the mini mum required power is in stalled, it can only provide 32 kW of
power, so the required battery power will be 17 kW. If the possible loss that occurs whe n the battery
supplies power to the motor is take n into accou nt, battery power of 20 kW will be n eeded. Thus, it is
necessary to determine the battery capacity by targeting this output on an actual slope. Table 2 lists the
required battery specificati ons.
Table 3 summarizes the specifications actually adopted by the THS and the requirements determ ined
by the above discussi on. The required items represe nt an example whe n mini mum engine power is
selected. In other words, if the engine is changed, each of the items have to be changed accord in gly.
Tub-le 2
Required batter) Kpecificatians
Item.Value
2SS V
Power20 IcW
Energy 1.8 kWh
Table 3
Required and. actual E-pcciOralions of the TI1W compDaienEs
Spcciiication Required vdlue THS
t inline EH髯imum pox弋丁44)k.W
Cicncnit口:r m^ximuinni lorquc17.1 Nm Ss N]n
hi 口tor maiimium torque Nm305 Mm
liallery mdiiinnium21 LW
uodl erwrgy(inKtantantnusI LH kWh
4. Driving force con trol The 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.
In puts of con trol system are accelerator positi on, vehicle speed (motor speed), gen erator speed and available battery power. Outputs are the engin e-required power, gen erator 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. The 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 required 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 gen erati ng engine power is
calculated; this is the engine target speed. The target speed for the gen erator is calculated using Eq.⑴ with engine target speed and motor speed. The generator torque is determ ined by PID con trol. 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 subtracting this torque from the initially
calculated drive torque. Since it is not possible to produce a torque whereby the motor con sumpti on power exceeds the total of the gen erator-ge nerated power and the power supplied by the battery, it is n ecessary to con trol the motor power (torque) with in this total power. Fig. 5 shows the control method. The sum of the power form the generator and the available battery power become the power that can be used by the motor. The available motor torque can be obtained by dividing this combined power by the motor speed. When the motor speed is low, if the calculated motor torque exceeds the motor specificati on of torque the motor
torque is determ ined by the specification. By controlling the motor torque requirement with this limited torque, the motor con sumpti on power can be con trolled to within the available power. If the available battery power is large eno ugh, the available motor torque hardly limits the motor torque. Con versely, whe n the charge is low, the motor torque is frequently limited.
Fig. 6 shows the respective maximum drive torque of the battery, the engine, and the engine plus the
battery while running based on the controls above, when the THS has the components as specified
Accelomlor Podd
PxitiQ 口 Trq.
1 h Acc. Speed
M-olor 、 Motor Tortjue Motor f by Power ------ k
A Avnilflible Ballery Power , L __ Power Genera Spwd
Required Drive Torque At Mow Axk Vehicle (Motor) 9peed Driwt Tgrgue fr^m Engine Genera lor . ContToller **
Battery SJharg'e Power
Required Power Engine Powf r Motor Speed
PID (kmtrol
Target hjlBltK! Tar^eL
GanfiratOf Spood. Geinerftlflr * T&rq?5__
in Secti on 3.
5. Con clusi ons
This paper discussed the control of drive power in the Toyota Hybrid System. The following
con clusi ons were obta in ed:
The performa nee required for each comp onent can be determ ined by reversely calculati ng power
performa nee required for a vehicle.
The available battery power varies according to its state of charge. However, by limiting the motor
torque, the battery power can be con trolled to within the battery's available power.
混合动力系统驱动力的串并联控制
摘要
由于混合动力系统的每个部分都有自己的极限性能，所以汽车动力取决于最脆弱的哪一个组成部分。因此，有必要对各个部件进行平衡设计。因为车辆必须在所有部件的控制范围内从事经营活动，所以我们根据所要求的驱动力反过来进行各部件的设计。在本文中，我们描述一种扭矩控制方法，以避免在低电量时损坏电池。日本B.V.科技公司的汽车工程协会保留所有版权。
1. 简介
近年来，内燃机车辆作为一种交通工具发挥了越来越重要的作用，为社会的发展做出了很多贡献。然而，车辆排放的废气使空气遭到污染，甚至使全球气候变暖，这就需要有效地对策去解决。在减少废气的排放方面正在取得各种各样的进展，但是，仅仅从提高引擎和传动装置已不再有很大希望得到改善。因此，发展电力、混合动力和天然气驱动的车辆是目前的最大期望。从当前使用的技术和汽油站检测服务设施，结合当前已安装的基础设施，以汽油发动机和电动机驱动的混合动力汽车是最现实的解决方案之一。
总的来说，混合动力系统分为串联和并联系统。在丰田，我们通过将这两个系统的优点结合起来，开发了丰田混合动力系统（以下简称THS）。在某种意义
上THS 可以称作串并联控制系统。由于丰田混合动力系统对发动机操作和排放的不断优化，因此可以取得更好的燃油经济性。在制动的过程中，动能被电动机重新回收，从而减少燃油消耗和随后的CO2 排放量。
通过使用丰田混合动力系统作为动力驱动系统，废弃的排放量和燃油经济性得到大大提高。然而，丰田混合动力系统采用了发动机、电动机、电池和其他组件，每个组件都有自己的特殊能力。换句话说，每个组件必须在自己的能力限制范围内生成驱动力。特别是由于电池的输出很大水平上取决于其充电量，因此要时刻铭记驱动力必须被限制。
这份报告澄清了基于车辆必须的驱动力对与丰田混合动力系统各组件的性能要求。驱动力在电池高低压时的控制方法也作了先关描述。
2.丰田混合动力系统
如图.1所示，丰田混合动力系统由混合动力传动装置、发动机和电池组成2.1. 混合动力传动系统
混合动力传动系统由发动机、发电机、动力分配装置和减速器组成。动力分配装置是一个行星齿轮机构。太阳轮、齿圈和行星架分别直接连接到发电机、电动机和发动机，齿圈也直接连接到减速器。因此，发动机的动力被分配到发电机和驱动轮。使用这种机械装置，各轴的转速有以下关系。在这里，太阳轮和齿圈之间的传动比是p :
Inventory management Inventory Control On the so-called "inventory control", many people will interpret it as a "storage management", which is actually a big distortion. The traditional narrow view, mainly for warehouse inventory control of materials for inventory, data processing, storage, distribution, etc., through the implementation of anti-corrosion, temperature and humidity control means, to make the custody of the physical inventory to maintain optimum purposes. This is just a form of inventory control, or can be defined as the physical inventory control. How, then, from a broad perspective to understand inventory control? Inventory control should be related to the company's financial and operational objectives, in particular operating cash flow by optimizing the entire demand and supply chain management processes (DSCM), a reasonable set of ERP control strategy, and supported by appropriate information processing tools, tools to achieved in ensuring the timely delivery of the premise, as far as possible to reduce inventory levels, reducing inventory and obsolescence, the risk of devaluation. In this sense, the physical inventory control to achieve financial goals is just a means to control the entire inventory or just a necessary part; from the perspective of organizational functions, physical inventory control, warehouse management is mainly the responsibility of The broad inventory control is the demand and supply chain management, and the whole company's responsibility. Why until now many people's understanding of inventory control, limited physical inventory control? The following two reasons can not be ignored: First, our enterprises do not attach importance to inventory control. Especially those who benefit relatively good business, as long as there is money on the few people to consider the problem of inventory turnover. Inventory control is simply interpreted as warehouse management, unless the time to spend money, it may have been to see the inventory problem, and see the results are often very simple procurement to buy more, or did not do warehouse departments . Second, ERP misleading. Invoicing software is simple audacity to call it ERP, companies on their so-called ERP can reduce the number of inventory, inventory control, seems to rely on their small software can get. Even as SAP, BAAN ERP world, the field of
Statistical hypothesis testing Adriana Albu，Loredana Ungureanu Politehnica University Timisoara,adrianaa@aut.utt.ro Politehnica University Timisoara,loredanau@aut.utt.ro Abstract In this article,we present a Bayesian statistical hypothesis testing inspection, testing theory and the process Mentioned hypothesis testing in the real world and the importance of, and successful test of the Notes. Key words Bayesian hypothesis testing; Bayesian inference;Test of significance Introduction A statistical hypothesis test is a method of making decisions using data, whether from a controlled experiment or an observational study (not controlled). In statistics, a result is called statistically significant if it is unlikely to have occurred by chance alone, according to a pre-determined threshold probability, the significance level. The phrase "test of significance" was coined by Ronald Fisher: "Critical tests of this kind may be called tests of significance, and when such tests are available we may discover whether a second sample is or is not significantly different from the first."[1] Hypothesis testing is sometimes called confirmatory data analysis, in contrast to exploratory data analysis. In frequency probability,these decisions are almost always made using null-hypothesis tests. These are tests that answer the question Assuming that the null hypothesis is true, what is the probability of observing a value for the test statistic that is at [] least as extreme as the value that was actually observed?) 2 More formally, they represent answers to the question, posed before undertaking an experiment,of what outcomes of the experiment would lead to rejection of the null hypothesis for a pre-specified probability of an incorrect rejection. One use of hypothesis testing is deciding whether experimental results contain enough information to cast doubt on conventional wisdom. Statistical hypothesis testing is a key technique of frequentist statistical inference. The Bayesian approach to hypothesis testing is to base rejection of the hypothesis on the posterior probability.[3][4]Other approaches to reaching a decision based on data are available via decision theory and optimal decisions. The critical region of a hypothesis test is the set of all outcomes which cause the null hypothesis to be rejected in favor of the alternative hypothesis. The critical region is usually denoted by the letter C. One-sample tests are appropriate when a sample is being compared to the population from a hypothesis. The population characteristics are known from theory or are calculated from the population.
经典文档下载后可编辑复制 湖北文理学院 毕业设计(论文)英文翻译 题目有限元热分析的陶瓷离合器 专业车辆工程 班级Xxx 姓名Xxxx 学号2010138xx 指导教师 职称Xxx 副教授 2014年2月25日
Fethermal analysis of a ceramic clutch 1. Introduction Abrasive dry running vehicle clutches are force closure couplings. Torque and speed transmission are ensured by the frictional force generated between two pressed surfaces. Reasons for the application of ceramic as a friction medium include good heat and wear resistance properties, which provide the opportunity to drive higher pressures, and a low density. Thus, an increasing power density is enabled with a parallel minimization of construction space. Measurements with a first prototype of a clutch disk using ceramic facings were performed at Karlsruhe University in a laboratory specialized in passenger car drive system testing. In the course of analysis the finite element (FE) model was to be constructed with the knowledge of measurement data and measurement conditions. Calculations were intended to determine the temperature distribution of the clutch disk and its environment at each moment in time corresponding to measurements. It is essential to be familiar with the temperature range in order to examine the wear characteristics of the system. Thus, important information is derived from measurement data. In critical load cases, the highest expected temperatures must be forecast in space and time in order to protect measuring instruments close to the location of heat generation. The goal of this study is to analyze and modify the clutch system to provide better operating conditions by improving the heat conduction and convection of the system or to increase the amount of the energy converted into frictional heat. Furthermore, it is desired to find better design solutions for more efficient clutch systems. Calculations were performed by the Cosmos Design Star software. During model development, great care had to be taken for proper simplification of geometry, the selection of element sizes, and the correct adjustment of time steps due to the substantial hardware requirements for transient calculations. Changes in thermal parameters such as the surface heat convection coefficient and thermal load had to be taken into consideration on an on-going basis in terms of time and location. The two sides of the analyzed test clutch system can only be managed by two independent models linked by heat partition,
吉林化工学院理学院 毕业论文外文翻译English Title（Times New Roman ，三号） 学生学号：08810219 学生姓名：袁庚文 专业班级：信息与计算科学0802 指导教师：赵瑛 职称副教授 起止日期：2012.2.27～2012.3.14 吉林化工学院 Jilin Institute of Chemical Technology
1 外文翻译的基本内容 应选择与本课题密切相关的外文文献（学术期刊网上的），译成中文，与原文装订在一起并独立成册。在毕业答辩前，同论文一起上交。译文字数不应少于3000个汉字。 2 书写规范 2.1 外文翻译的正文格式 正文版心设置为：上边距：3.5厘米，下边距：2.5厘米，左边距：3.5厘米，右边距：2厘米，页眉：2.5厘米，页脚：2厘米。 中文部分正文选用模板中的样式所定义的“正文”，每段落首行缩进2字；或者手动设置成每段落首行缩进2字，字体：宋体，字号：小四，行距：多倍行距1.3，间距：前段、后段均为0行。 这部分工作模板中已经自动设置为缺省值。 2.2标题格式 特别注意：各级标题的具体形式可参照外文原文确定。 1．第一级标题（如：第1章绪论）选用模板中的样式所定义的“标题1”，居左；或者手动设置成字体：黑体，居左，字号：三号，1.5倍行距，段后11磅，段前为11磅。 2．第二级标题（如：1.2 摘要与关键词）选用模板中的样式所定义的“标题2”，居左；或者手动设置成字体：黑体，居左，字号：四号，1.5倍行距，段后为0，段前0.5行。 3．第三级标题（如：1.2.1 摘要）选用模板中的样式所定义的“标题3”，居左；或者手动设置成字体：黑体，居左，字号：小四，1.5倍行距，段后为0，段前0.5行。 标题和后面文字之间空一格（半角）。 3 图表及公式等的格式说明 图表、公式、参考文献等的格式详见《吉林化工学院本科学生毕业设计说明书（论文）撰写规范及标准模版》中相关的说明。
农村社会养老保险的现状、问题与对策研究社会保障对国家安定和经济发展具有重要作用，“城乡二元经济”现象日益凸现，农村社会保障问题客观上成为社会保障体系中极为重要的部分。建立和完善农村社会保障制度关系到农村乃至整个社会的经济发展，并且对我国和谐社会的构建至关重要。我国农村社会保障制度尚不完善，因此有必要加强对农村独立社会保障制度的构建，尤其对农村养老制度的改革，建立健全我国社会保障体系。从户籍制度上看，我国居民养老问题可分为城市居民养老和农村居民养老两部分。对于城市居民我国政府已有比较充足的政策与资金投人，使他们在物质和精神方面都能得到较好地照顾，基本实现了社会化养老。而农村居民的养老问题却日益突出，成为摆在我国政府面前的一个紧迫而又棘手的问题。 一、我国农村社会养老保险的现状 关于农村养老，许多地区还没有建立农村社会养老体系，已建立的地区也存在很多缺陷，运行中出现了很多问题，所以完善农村社会养老保险体系的必要性与紧迫性日益体现出来。 （一）人口老龄化加快 随着城市化步伐的加快和农村劳动力的输出，越来越多的农村青壮年人口进入城市，年龄结构出现“两头大，中间小”的局面。中国农村进入老龄社会的步伐日渐加快。第五次人口普查显示：中国65岁以上的人中农村为5938万，占老龄总人口的67.4%.在这种严峻的现实面前，农村社会养老保险的徘徊显得极其不协调。 （二）农村社会养老保险覆盖面太小 中国拥有世界上数量最多的老年人口，且大多在农村。据统计，未纳入社会保障的农村人口还很多，截止2000年底，全国7400多万农村居民参加了保险，占全部农村居民的11.18%，占成年农村居民的11.59%.另外，据国家统计局统计，我国进城务工者已从改革开放之初的不到200万人增加到2003年的1.14亿人。而基本方案中没有体现出对留在农村的农民和进城务工的农民给予区别对待。进城务工的农民既没被纳入到农村养老保险体系中，也没被纳入到城市养老保险体系中，处于法律保护的空白地带。所以很有必要考虑这个特殊群体的养老保险问题。
Automobile Brake System汽车制动系统 The braking system is the most important system in cars. If the brakes fail, the result can be disastrous. Brakes are actually energy conversion devices, which convert the kinetic energy (momentum) of the vehicle into thermal energy (heat).When stepping on the brakes, the driver commands a stopping force ten times as powerful as the force that puts the car in motion. The braking system can exert thousands of pounds of pressure on each of the four brakes. Two complete independent braking systems are used on the car. They are the service brake and the parking brake. The service brake acts to slow, stop, or hold the vehicle during normal driving. They are foot-operated by the driver depressing and releasing the brake pedal. The primary purpose of the brake is to hold the vehicle stationary while it is unattended. The parking brake is mechanically operated by when a separate parking brake foot pedal or hand lever is set. The brake system is composed of the following basic components: the “master cylinder” which is located under the hood, and is directly connected to the brake pedal, converts driver foot’s mechanical pressure into hydraulic pressure. Steel “brake lines” and flexible “brake hoses” connect the master cylinder to the “slave cylinders” located at each wheel. Brake fluid, specially designed to work in extreme conditions, fills the system. “Shoes” and “pads” are pushed by the slave cylinders to contact the “drums” and “rotors” thus causing drag, which (hopefully) slows the c ar. The typical brake system consists of disk brakes in front and either disk or drum brakes in the rear connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder (Figure). Basically, all car brakes are friction brakes. When the driver applies the brake, the control device forces brake shoes, or pads, against the rotating brake drum or disks at wheel. Friction between the shoes or pads and the drums or disks then slows or stops the wheel so that the car is braked.
软件专业毕业论文外文文献中英文翻译 Object landscapes and lifetimes Tech nically, OOP is just about abstract data typing, in herita nee, and polymorphism, but other issues can be at least as importa nt. The rema in der of this sect ion will cover these issues. One of the most importa nt factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object con trolled? There are differe nt philosophies at work here. C++ takes the approach that con trol of efficie ncy is the most importa nt issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocatio n and release, and con trol of these can be very valuable in some situati ons. However, you sacrifice flexibility because you must know the exact qua ntity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided desig n, warehouse man ageme nt, or air-traffic con trol, this is too restrictive. The sec ond approach is to create objects dyn amically in a pool of memory called the heap. In this approach, you don't know un til run-time how many objects you n eed, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is runnin g. If you n eed a new object, you simply make it on the heap at the point that you n eed it. Because the storage is man aged dyn amically, at run-time, the amount of time required to allocate storage on the heap is sig ni fica ntly Ion ger tha n the time to create storage on the stack. (Creat ing storage on the stack is ofte n a si ngle assembly in structio n to move the stack poin ter dow n, and ano ther to move it back up.) The dyn amic approach makes the gen erally logical assumpti on that objects tend to be complicated, so the extra overhead of finding storage and releas ing that storage will not have an importa nt impact on the creati on of an object .In additi on, the greater flexibility is esse ntial to solve the gen eral program ming problem. Java uses the sec ond approach, exclusive". Every time you want to create an object, you use the new keyword to build a dyn amic in sta nee of that object. There's ano ther issue, however, and that's the lifetime of an object. With Ian guages that allow objects to be created on the stack, the compiler determines how long the object lasts and can automatically destroy it. However, if you create it on the heap the compiler has no kno wledge of its lifetime. In a Ianguage like C++, you must determine programmatically when to destroy the
本科毕业论文（设计）文献综述和外文翻译 撰写要求与格式规范 一、毕业论文（设计）文献综述 （一）毕业论文（设计）文献综述的内容要求 1．封面：由学院统一设计，普通A4纸打印即可。 2.正文 综述正文部分需要阐述所选课题在相应学科领域中的发展进程和研究方向，特别是近年来的发展趋势和最新成果。通过与中外研究成果的比较和评论，说明自己的选题是符合当前的研究方向并有所进展，或采用了当前的最新技术并有所改进，目的是使读者进一步了解本课题的意义。文中的用语、图纸、表格、插图应规范、准确，量和单位的使用必须符合国家标准规定，引用他人资料要有标注。 文献综述字数在5000字以上。 正文前须附500字左右中文摘要，末尾须附参考文献。 参考文献的著录按在文献综述中出现的先后顺序编号。 期刊类文献书写方法:[序号]作者（不超过3人，多者用等表示）.题（篇）名[J].刊名,出版年,卷次（期次）:起止页次.
图书类文献书写方法:[序号]作者.书名[M].版本.出版地:出版者,出版年:起止页次. 论文集类文献书写方法:[序号]作者.篇名[C].论文集名.出版地:出版者,出版年:起止页次. 学位论文类书写方法:[序号]作者.篇名[D].出版地:单位名称,年份. 电子文献类书写方法:[序号]主要责任者. 题名:其他题名信息[文献类型标志/文献载体标志 ]出版地:出版者,出版年（更新或修改日期）[引用日期].获取和访问途径. 参考文献篇数应符合学院毕业论文（设计）工作的要求。 （二）毕业论文（设计）文献综述撰写与装订的格式规范 第一部分：封面 1.封面：由学院统一设计，“本科生毕业论文（设计）”根据作业实际明确为“论文”或“设计”，其它文本、表格遇此类情况同样处理。 第二部分：文献综述主题 1.中文摘要与关键词 摘要标题（五号，宋体，顶格，加粗）
毕业论文（设计）外文翻译 题目：中国上市公司偏好股权融资：非制度性因素 系部名称：经济管理系专业班级:会计082班 学生姓名：任民学号： 200880444228 指导教师：冯银波教师职称:讲师 年月日
译文： 中国上市公司偏好股权融资：非制度性因素 国际商业管理杂志 2009.10 摘要：本文把重点集中于中国上市公司的融资活动，运用西方融资理论，从非制度性因素方面，如融资成本、企业资产类型和质量、盈利能力、行业因素、股权结构因素、财务管理水平和社会文化，分析了中国上市公司倾向于股权融资的原因，并得出结论，股权融资偏好是上市公司根据中国融资环境的一种合理的选择。最后，针对公司的股权融资偏好提出了一些简明的建议。 关键词：股权融资，非制度性因素，融资成本 一、前言 中国上市公司偏好于股权融资，根据中国证券报的数据显示，1997年上市公司在资本市场的融资金额为95.87亿美元，其中股票融资的比例是72.5％，，在1998年和1999年比例分别为72.6％和72.3％，另一方面，债券融资的比例分别是17.8％，24.9％和25.1％。在这三年，股票融资的比例，在比中国发达的资本市场中却在下跌。以美国为例，当美国企业需要的资金在资本市场上，于股权融资相比他们宁愿选择债券融资。统计数据显示，从1970年到1985年，美日企业债券融资占了境外融资的91.7％，比股权融资高很多。阎达五等发现，大约中国3/4的上市公司偏好于股权融资。许多研究的学者认为，上市公司按以下顺序进行外部融资：第一个是股票基金，第二个是可转换债券，三是短期债务，最后一个是长期负债。许多研究人员通常分析我国上市公司偏好股权是由于我们国家的经济改革所带来的制度性因素。他们认为，上市公司的融资活动违背了西方古典融资理论只是因为那些制度性原因。例如，优序融资理论认为，当企业需要资金时，他们首先应该转向内部资金（折旧和留存收益），然后再进行债权融资，最后的选择是股票融资。在这篇文章中，笔者认为，这是因为具体的金融环境激活了企业的这种偏好，并结合了非制度性因素和西方金融理论，尝试解释股权融资偏好的原因。
Drive force control of a parallel-series hybrid system Abstract Since 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 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 of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved. 1. Introduction In 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, vehicle 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, great 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 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 both 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 and subsequent CO 2 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 within 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 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) [1,2] As Fig. 1 shows, the THS is made up of a hybrid transmission, engine and battery. 2.1. Hybrid transmission The transmission consists of 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 into the generator and the driving wheels. With this type of mechanism, the