机械专业毕业设计论文外文文献原稿和译文

北京化工大学北方学院毕业设计（论文）外文文献原稿和译文外文文献原稿和译文原 稿Mechanical and Regenerative Braking Integration for a Hybrid Electric VehicleAbstractHybrid electric vehicle technology has become a preferred method for the automotive industry to reduce environmental impact and fuel consumption of their vehicles. Hybrid electric vehicles accomplish these reductions through the use of multiple propulsion systems, namely an electric motor and internal combustion engine, which allow the elimination of idling, operation of the internal combustion engine in a more efficient manner and the use of regenerative braking. However, the added cost of the hybrid electric system has hindered the sales of these vehicles.A more cost effective design of an electro-hydraulic braking system is presented. The system electro-mechanically controlled the boost force created by the brake booster independently of the driver braking force and with adequate time response. The system allowed for the blending of the mechanical and regenerative braking torques in a manner transparent to the driver and allowed for regenerative braking to be conducted efficiently.A systematic design process was followed, with emphasis placed on demonstrating conceptual design feasibility and preliminary design functionality using virtual and physical prototyping. The virtual and physical prototypes were then used in combination as a powerful tool to validate and develop the system. The role of prototyping in the design process is presented and discussed.Through the experiences gained by the author during the design process, it is recommended that students create physical prototypes to enhance their educational experience. These experiences are evident throughout the thesis presented.1.1 Modern Hybrid Electric VehiclesWith rising gas prices and the overwhelming concern for the environment, consumers and the government have forced the automotive industry to start producing more fuel efficient vehicles with less environmental impact. One promising method that is currently being implemented is the hybrid electric vehicle.Hybrid vehicles are defined as vehicles that have two or more power sources 25. There are a large number of possible variations, but the most common layout of hybrid vehicles today combines the power of an internal combustion engine (ICE) with the power of an electric motor and energy storage system (ESS). These vehicles are often referred to as hybrid electric vehicles (HEVs) 25. These two power sources are used in conjunction to optimize the efficiency and performance of the vehicle, which in turn will increase fuel economy and reduce vehicle emissions, all while delivering the performance the consumer requires. In 1997, the Toyota Prius became the first hybrid vehicle introduced into mass production in Japan. It took another three years for the first mass produced hybrid vehicle, the Honda Insight, to be introduced into the North American market. The release of the Honda Insight was closely followed by the release of the Toyota Prius in North America a couple of months later 35.Hybrid electric vehicles have the distinct advantage of regenerative braking. The electric motor, normally used for propulsion, can be used as a generator to convert kinetic energy of the vehicle back into electrical energy during braking, rather than wasting energy as heat. This electrical energy can then be stored in an ESS (e.g. batteries or ultracapacitors) and later released to propel the vehicle using the electric motor.This process becomes even more important when considering the energy density of batteries compared to gasoline or diesel fuel. Energy density is defined as the amount of energy stored in a system per unit volume or mass 44. To illustrate this point, 4 kilograms (4.5 litres) of gasoline will typically give a motor vehicle a range of 50 kilometres. To store the same amount of useful electric energy it requires a lead acid battery with a mass of about 270 kilograms 25. This demonstrates the need for efficient regenerative braking to store electrical energy during driving, which in turn will keep the mass of the energy storage system down and improve the performance and efficiency of the HEV.1.2 Research Scope - Regenerative Braking SystemsThe scope of the research presented is to create a low cost regenerative braking system to be used on future economical hybrid vehicles to study the interaction between regenerative and mechanical braking of the system. This system should be able to control the combination of both regenerative and mechanical braking torque depending on driver demand and should be able to do so smoothly and safely. Controlling the regenerative braking torque can be done using control algorithms and vector control for induction motors. However, controlling the mechanical braking torque independently of the driver pedal force, while maintaining proper safety back-ups, proved to be more of a challenge. To overcome this problem, a system was developed that would attenuate the pressure in the brake booster in order to control the amount of mechanical torque developed by the braking system2.1 Hybrid Electric Vehicle OverviewHybrid vehicles have emerged as one of the short term solutions for reducing vehicleemissions and improving fuel economy. Over the past 10 years almost all of the majorautomotivecompanies have developed and released for sale their own hybrid electricvehicles to the public. The popularity of hybrid electric vehicles has grown considerably since the turn ofthe century. With enormous pressure to become more environmentally friendly and withunpredictable gas prices, the sales of hybrid electric vehicles have increased dramaticallyin recent years. 2.1.1 Hybrid ConfigurationsFor the past 100 years the objective of the hybrid has been to extend the range of electricvehicles and to overcome the problem of long recharging times 35. There are threepredominant hybrid electric vehicle configurations currently on the market today. These configurations are known as series hybrids, parallel hybrids and series/parallel hybrids.Each configuration has its advantages and disadvantages which will be discussed in the following sections.Series HybridsIn series hybrids the mechanical output from the internal combustion engine is used todrive a generator which produces electrical power that can be stored in the batteries orused to power an electric motor and drive the wheels. There is no direct mechanicalconnection between the engine and the driven wheels. Series hybrids tend to be used inhigh power systems such as large trucks or locomotives but can also be used for lower power passenger vehicles 18. The mechanically generated electrical power is combined with the power from the battery in an electronic controller. This controller then compares the driver demand with the vehicle speed and available torque from the electric motor to determine the amount of power required from each source to drive the vehicle. During braking, the controller also switches the power electronics to regenerative mode, and directs the power being regenerated to the batteries 55.There are many advantages made possible by the arrangement described above. It is possible to run the ICE constantly at its most efficient operating point and share its electrical output between charging the battery and driving the electric motor. By operating the engine at its most efficient operating point, emissions can be greatly reduced and the most electrical power can be generated per volume of fuel. This configuration is also easierto implement into a vehicle because it is less complex which makes this method more cost effective.Parallel HybridsIn parallel hybrid configurations the mechanical energy output from the ICE is transmitted to a gearbox. In this gearbox the energy from the ICE can be mechanically combined with a second drive from an electric motor. The combined mechanical output is then used to drive the wheels 35. In this configuration there is a direct connection between the engine and the driven wheels. As in series hybrids the controller compares the driver demand with the vehicle speed and output torque and determines the amount of power to be used from each source to meet the demand, while obtaining the best possible efficiency. A parallel hybrid also controls regenerative braking similarly to a series hybrid. Parallel hybrids are usually used in lower power electric vehicles in which both drives can be operated in parallel to provide higher performance 18.There are a number of advantages of a parallel hybrid over a series hybrid. The most important advantage is that since only one conversion between electrical and mechanical power is made, efficiency will be much better than the series hybrid in which two conversions are required. Since the parallel hybrid has the ability to combine both the engine and electric motor powers simultaneously, smaller electric motors can be used without sacrificing performance, while getting the fuel consumption and emission reduction benefits. Lastly, parallel hybrids only need to operate the engine when the vehicle is moving and do not need a second generator to charge the batteries.Series/Parallel HybridsCombined hybrids have the features of both series and parallel configurations. They use a power split device to drive the wheels using dual sources of power (e.g. electric motor only, ICE only or a combination of both). While the added benefits of both series hybrids and parallel hybrids are achieved for this configuration, control algorithms become very complex because of the large number of driving possibilities available.2.1.2 Degree of HybridizationSince most HEVs on the road today are either parallel or series/parallel, it is useful to define a variable called the degree of hybridization to quantify the electrical power potential of these vehicles.The degree of hybridization ranges from (DOH = 0) for a conventional vehicle to (DOH = 1) for an all electric vehicle 25. As the degree of hybridization increases, a smaller ICE can be used and operated closer to its optimum efficiency for a greater proportion of the time, which will decrease fuel consumption and emissions. The electric motor power is denoted by Pem and the internal combustion engine power is denoted by Pice.Micro HybridMicro hybrids have the smallest degree of hybridization and usually consist of an integrated starter generator (ISG) connected to the engine crankshaft. The ISG allows the engine to be shut off during braking and idling to conserve fuel and then spins the crankshaft up to speed before fuel is injected during acceleration. The ISG also provides small amounts of assist to the ICE during acceleration and acts as a generator to charge the batteries during braking. Micro hybrids usually improve fuel economy by about 10 percent compared with non hybrids 53.Mild HybridMild hybrids have a similar architecture to the micro hybrid except that the ISG is uprated in power to typically greater than 20 kW. However, the energy storage system is limited to less than 1 kWh 35. Mild hybrids usually have a very short electric-only range capability but can provide a greater assist to the ICE during accelerations. The electrical components in a mild hybrid are more complex than a micro hybrid and play a greater role in the vehicle operation. Fuel economy can be improved by 20 to 25 percent with a mild hybrid over non hybrid vehicles 53.Full HybridFull hybrids do away with the ISG and replace it with a separate electric motor and alternator/starter that perform the same function. The electric motor has the ability to propel the vehicle alone, particularly in city (stop and go) driving. The energy storage system is upgraded to improve electric-only range capability and the engine is usually downsized to improve fuel economy and emissions. Full hybrids can achieve 40 to 45 percent fuel consumption reductions over non hybrids 53.Plug-in HybridPlug-in hybrids are very similar to full hybrids except that they have a much larger ESS that can be connected to an outside electrical utility source for charging. These vehicles use only the electric motor to propel the vehicle within the range of the batteries and then operate like full hybrids once the batteries have discharged to a predefined level.2.1.3 Fundamentals of Regenerative BrakingOne of the most important features of HEVs is their ability to recover significant amounts of braking energy. The electric motors can be controlled to operate as generators during braking to convert the kinetic energy of the vehicle into electrical energy that can be stored in the energy storage system and reused. However, the braking performance of a vehicle also greatly affects vehicle safety. In an emergency braking situation the vehicle must be stopped in the shortest possible distance and must be able to maintain control over the vehicles direction. The latter requires control of brake force distribution to the wheels 12.Generally, the braking torque required is much larger than the torque that an electric motor can produce 12. Therefore, a mechanical friction braking system must coexist with the electrical regenerative braking. This coexistence demands proper design and control of both mechanical and electrical braking systems to ensure smooth, stable braking operations that will not adversely affect vehicle safety.Energy Consumption in BrakingBraking a 1500 kg vehicle from 100 km/h to 0 km/h consumes about 0.16 kWh of energy based on Equation 2.2.If 25 percent of this energy could be recovered through regenerative braking techniques, then Equation 2.2 can be used to estimate that this energy could be used to accelerate the vehicle from 0 km/h to about 50 km/h, neglecting aerodynamic drag, mechanical friction and rolling resistance during both braking and accelerating. This also assumes that the generating and driving modes of the electric motor are 100% efficient. This suggests that the fuel economy of HEVs can be greatly increased when driving in urban centres where the driver is constantly braking and accelerating. Note that the amount of energy recovered is limited by the size of the electric motor and the rate of which energy can be transferred to the ESS.2.1.4 Methods of Regenerative BrakingThere are two basic regenerative braking methods used today. These methods are often referred to as parallel regenerative braking and series regenerative braking. Each of these braking strategies have advantages and disadvantages that will be discussed in this section.Parallel Regenerative BrakingDuring parallel regenerative braking, both the electric motor and mechanical braking system always work in parallel (together) to slow the vehicle down 48. Since mechanical braking cannot be controlled independently of the brake pedal force it is converting some of the vehicles kinetic energy into heat instead of electrical energy. This is not the most efficient regenerative braking method. However, parallel regenerative braking does have the advantages of being simple and cost effective. For this method to be used, the mechanical braking system needs little modification and the control algorithms for the electric motor can be easily implemented into the vehicle. This method also has the added advantage of always having the mechanical braking system as a back-up in case of a failure of the regenerative braking system.Series Regenerative BrakingDuring series regenerative braking the electric motor is solely used for braking. It is only when the motor or energy storage system can no longer accept more energy that the mechanical brakes are used 48. This method requires that the mechanical braking torque be controlled independently of the brake pedal force and has the advantage of being the most efficient by converting as much of the vehicles kinetic energy into electrical energy . The downfall of this method is that it brings many costs and complexities into the system. For this method to function properly a brake-by-wire system has to be developed which either uses an electro-hydraulic brake (EHB) or an electro-mechanical brake (EMB). Both of these types of brakes require brake pedal simulators and redesigned brake systems which can become costly. Since these systems are brake-by-wire there are also many redundancies required with sensors, processors and wiring for safety which add to the complexity of the system.2.1.5 Current Regenerative Braking SystemsThe current regenerative braking system in most HEVs (e.g. Toyota Prius) is the more costly electro-hydraulic braking (EHB) system. This system uses a brake pedal simulator, which is separate from the hydraulic braking circuit, to establish driver braking demand. The braking demand is then proportioned into a regenerative and mechanical braking demand. The mechanical braking demand is then sent to a system that contains a high pressure hydraulic pump, accumulator and proportional control valves. The proportional control valves allow the brake line fluid to flow to each wheel at predefined pressures determined by the braking demand.译 文混合动力电动汽车机械和再生制动的整合摘 要为了减少对环境的污染和车辆的燃油消耗，混合动力电动汽车已经成为汽车工业的首选方法。混合动力电动汽车通过使用由电动马达和内燃发动机组成的混合动力系统来达到减少环境污染和燃油消耗的目的。混合动力系统消除了怠速，使发动机以一种更有效的方式运行，增加了再生制动的使用。但是，混合动力的成本的增加阻碍了这些车辆的销售。在这里提出一个更具成本效益的电液制动系统的设计。该系统使用电控机械结合的控制方式控制制动助力器产生的推动力，并有足够的时间反应。这个系统使驾驶员清楚地了解机械和再生制动力矩的混合，使再生制动力系统得到有效的控制。一个系统化的设计过程是其次，重点在于展示概念设计方案的可行性和使用虚拟和实物模型的初步设计功用。虚拟和实物模型的结合使用成为验证和开发系统的强大工具，本文将介绍和讨论在设计过程中模型所起到的作用。因为在设计过程中设计者可以获得相关的经验，提倡学生设计实物模型，以提高学生的学习经验。很明显，这正是本文所要提出的。1.1现代混合动力电动汽车 随着油价的上涨和环境保护意识的提高，消费者和政府迫使汽车行业开始生产省油和对环境污染小的汽车。一个有前景的方法就是现在实行的混合动力电动汽车。混合动力汽车指的是有两个或两个以上动力来源的车辆。混合动力汽车动力的来源可能有很多的不同，但是现在混合动力汽车最常见的布局是由内燃发动机和电动马达，能量储存系统共同输出动力，这样的车辆就叫混合动力电动汽车。汽车可以同时使用发动机和电动马达输出的动力，从而可以提高汽车的使用性能和效率，进而又可以提高燃油经济性，减少废气的排放，同时还能满足消费者对汽车性能的要求。1997年，丰田成普瑞斯为了第一款混合动力电动汽车，在日本进行了批量生产。本田公司花费了三年的时间进行混合动力电动车的生产，然后进军北美市场。丰田普瑞斯在北美发行几个月后，本田Insight紧随其后也在北美进行发行。混合动力电动车具有再生制动系统的独特优势。在制动过程，通常用于动力输出的电动马达，可以起到发电机的功用，把汽车的动能转化为蓄电池的电能，而不会转化为热能浪费掉。转换的电能可以储存到蓄电池中，然后可以作为电动马达驱动汽车使用的能量。考虑到蓄电池能量密度时，动能转换为电能这个过程就更加重要了。能量密度是指单位体积或质量下能量储存系统所储存的能量。为了说明这一点，我们可以做个对比，4.5公升的汽油通常可以维持一辆汽车行驶50千米。而要把相同的能量储存到蓄电池中，则需要一个质量约为270千克的铅酸蓄电池。这就说明了在汽车行驶过程中能够有效地储存再生制动系统产生的能量的重要性，从而可以保证在提高混合动力电能车性能的前提下，不至使能量储存系统所占体积过大。1.2再生制动系统研究范围 本文所提出的再生系统的研究范围是研究再生制动系统和机械制动系统之间相互作用的关系，目的是设计开发出一个低成本的再生制动系统，从而可以应用到未来经济型的混合动力电动汽车上。这个系统可以根据驾驶员的需要进而控制再生制动系统和机械制动系统产生的制动力矩的结合，还应该保证这个过程的平顺性和安全性。再生制动力矩是通过使用的异步电动机的矢量控制算法进行控制的。但是，独立地控制制动踏板产生的机械制动力矩，同时又要保持机械制动系在再生制动系统失效后起到备用作用，这是一个很大的难题。为了解决这个问题，需要研究一个通过减少制动主缸内制动液压来来控制机械制动系统产生的制动力矩的制动系统。2.1混合电动汽车概述混合动力电动车已经成为了可以在短时间内减少汽车污染排放和提高燃油经济型的解决方法之一。在过去的10年几乎所有的主要汽车公司都已经向公众发行销售自己的混合动力电动汽车，混合动力电动汽车的普及和销售在这个世纪有了很明显的增长，随着不可预测的汽油价格的增长和对环境保护的关注，混合动力电动汽车的销售将在最近几年内急剧增长。2.1.1混合动力装置在过去100年来混合动力的研究目标是延长电动汽车的使用寿命，解决蓄电池的长期充电问题。在目前市场，现在主要有三种混合动力装置，这些混合动力装置为串联混合动力，并联混合动力，串并联混合动力。每一种动力装置都有其优点和缺点，这将在以后的章节进行讨论。串联混合动力串联混合动力汽车使用发动机输出的动力来驱动发电机产生电能，这些电能可以储存在蓄电池中，也可以用来驱动电动马达来驱动汽车。在串联混合动力汽车上，发动机和驱动轮之间没有直接的机械连接，串联混合动力往往在高功率系统中使用，如大型货车或火车，也可以应用到低功率的客运车辆上。发动机输出的机械能和蓄电池输出的电能可以通过电子控制器进行控制接合，然后这个电子控制器通过比较驾驶员所需的动力和汽车车速，电动马达输出的转矩，从而决定每个动力源驱动汽车行驶所要输出的能量。在制动过程中，这个电子控制装置可以使电能输出模式转换为再生模式，直接把再生制动系统产生的电能储存在蓄电池内。按照这种布置方式进行设计有很多的优点。发动机可以保持高效率的运行，使发动机产生的电能在蓄电池和驱动马达之间得到分配。发动机在其最高效率的工况下运行，排放可以大大降低，燃烧每体积的燃料可以产生更多的电能。因为串联动力装置结构简单且成本低，这种动力装置很容在汽车上落实。并联混合动力在并联混合动力汽车中，发动机输出的机械功传到变速箱中。发动机输出的机械功和电动马达输出的功在变速箱内进行机械式的接合，混合的机械功用于驱动汽车行驶。在这种混合动力装置结构中，发动机和驱动轮之间有直接的机械连接。在串联混合动力装置中，电子控制器通过比较驾驶员所需的动力和汽车车速，电动马达输出的转矩，从而决定每个动力源驱动汽车行驶所要输出的能量，以满足汽车行驶性能，获得最佳的效率。正如串联混合装置一样，并联混合动力也以相似的方法控制再生制动。并联混合动力装置通常应用到低功率的电动车中，这两种驱动力可以同时使用，提供更高的行驶性能。与串联混合动力系统相比，并联混合动力系统有很多优势。其中最重要的一项优势是效率高，因为在并联混合动力中，电能和机械能只需转换一次，而在串联混合动力中，电能和机械能需要两次转换。由于并联混合动力可以