捷达轿车麦弗逊式前独立悬架设计及有限元分析【三维PROE模型】【3张CAD图纸、说明书】【QX系列】
喜欢就充值下载吧。资源目录里展示的全都有,下载后全都有,所见即所得,CAD图纸均为高清图可自行编辑,文档WORD都可以自己编辑的哦,有疑问咨询QQ:1064457796,课题后的【XX系列】为整理分类用,与内容无关,请忽视
Advances in Automobile Engineering: Brake Assisted Differential Locking SystemAbstract“It takes 8,460 bolts to assemble an automobile, andone nut to scatter it all over the road.”Some of the biggest advances in the field of automotive technology in the past 10 years have come in the area of safety.Spurred by the improvements in the microprocessor speed,miniaturization, and software development, the automobile continues to evolve.In this new approach proposed, I am going to have an electronic and a pneumatic circuit to automatically control the traction of the vehicle.During ordinary conditions, when the vehicle is driven down a straight road, or if the difference between speeds of the two(rear) wheels is below a specified limit, no signal will be generated by the electronic circuit. This helps the vehicle negotiate the turns with better traction control as differential action is unaltered. But if the difference between speeds is beyond a specified limit, the signal will be generated by the electronic circuit which will actuate the pneumatic circuit. This causes gradual braking on the faster wheel until it gains traction.Hence, the wheels will never lose traction.This system ensures a reduction of more than 50% in the capital investment as compared to the already existing systems can tilt the scales in the favour of the manufacturing company and eventually the cost conscious consumer.Key words: Differential locking, traction control, Limited slip differential, pneumatic braking.I. INTRODUCTIONAre you really comfortable manoeuvring your vehicle through a muddy patch?In dry conditions, when there is plenty of traction, the amount of torque applied to the wheels is limited by the engine and gearing; in a low traction situation, such as when driving on ice, the amount of torque is limited to the greatest amount that will not cause a wheel to slip under those conditions. So, even though a car may be able to produce more torque, there needs to be enough traction to transmit that torque to the ground .As long as the tyre grips the road,providing a resistance to turning, the drive train forces the vehicle forward.Driveline torque is evenly distributed between the two rear drive axle shafts by the differential. When one tyre encounters a slippery spot on the road, it looses traction, resistance to rotation drops, and the wheel begins to spin. Because the resistance has dropped, the torque delivered to both the wheels changes. The wheel with good traction is no longer driven. If the vehicle is stationary in this condition, only the wheel over the slippery spot rotates. Hence the vehicle does not move. This situation places stress on differential gears. As the traction fewer wheels rotates at a very high speed, amount of heat generated increases rapidly, lube film breaks down, metal to metal contact occurs, and the parts are damaged. Now if the spinning wheel suddenly has traction, then the shock of the sudden traction can cause severe damage to the drive axle assembly.So presently how do we overcome these difficulties?To overcome these problems, differential manufacturers have developed the Limited Slip Differential. In automotive applications, a limited slip differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In an automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity. The main advantage of a limited slip differential is found by considering the case of a standard (or open) differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate at twice its intended velocity the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use however, such as driving off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels. The clutch type LSD responds to drive shaft torque. The more drive shaft input torque present, the harder the clutches are pressed together and thus the more closely the drive wheels are coupled to each other.Limitations of the Limited Slip Differentiala) Heat dissipation leads to lube film breakage, metalto-metal contact occurs.b) If the friction lining of the energized clutch is damaged, the whole assembly has to be dissembled.c) High quality lubrication required.d) Due to presence of large number of mechanical components, reliability is less.e) As the speed increases, noise of vehicle also increases.f) Complicated and costly.II. PROPOSED INNOVATION-BRAKE ASSISTED DIFFERENTIAL LOCKINGSYSTEM (BADLS)In this new approach, there is an electronic and a pneumatic circuit to automatically control the traction of the vehicle. During the ordinary conditions, when the vehicle is driven down the straight road, or if the difference between the speeds of the two (rear) wheels is below a specified limit, no signal will be generated by the electronic circuit. This helps the vehicle negotiate the turns with better traction control, as the differential action is unaltered. But if the difference between the speeds is beyond a specified limit, the signal will be generated by the electronic circuit, which will actuate the pneumatic circuit. This causes gradual braking on the faster wheel until it gains traction. Hence, the wheels will never lose traction. The BADLS control module senses that a wheel is about to slip based on the input sensor data and in turn pulses the normally open inlet solenoid valve closed for that circuit.This allows fluid to enter the circuit. At the same time, the control module opens the normally closed solenoid valve for that circuit. This leads to the application of pneumatic pressure on the brake pads, leading to the artificial braking. Once the affected wheel returns to the same speed as the other wheel the control module returns both the valves to their respective normal positions releasing any residual pressure in the pneumatic circuit of the affected brake.Fig. 1 SCHEMATIC CIRCIUT OF BADLSWORKING:Normal Braking System Artificial Braking System(BADLS)When Slipping Take PlaceNormal Braking Condition When Speed Sensors Detect The Slipping ConditionBrake Control Valve ActuatedMicrocontroller Actuates Normally Opened Solenoid Valve2Microcontroller Actuates Normally Closed Solenoid Valve1 And Normally Opened Solenoid Valve2Solenoid Valve1 Remains InDefault Normally Closed StateArtificial Braking Is Applied To The Required Wheel By Flowing In The Auxiliary CircutAir Flows From Maste Cylinder Through The Main Circuit By Passing The Auxiliary Circut空气经主电路从主汽缸流出绕过辅助电路Fig. 2 WORKING OF THE BADLS CIRCUITFlowchart to explain working of the circuit shown in Fig 1 is given above in Fig 2. First flowchart shows working of normal breaking circuit and the latter shows the working when the badls circuit is working. During normal breaking condition solenoid valve 1 is in closed condition so air from master cylinder flows in main braking circuit bypassing the auxiliary circuit through solenoid valve 1 and thus normal breaking action is achieved. .In slipping condition microcontroller actuates normally closed solenoid valve and normally open solenoid valve 2 and thus artificial braking is applied to the required wheel.A. The BADLS Control moduleThe system is provided a control system, at least two driven wheels, a differential for transmitting power from the engine to the driven wheels and permitting relative velocity between the driven wheels. The control system includes two wheel velocity sensor, a comparator circuit and a control circuit. The wheel velocity sensor is configured to detect the angular velocity of the two driven wheels and to generate a signal. The comparator circuit is coupled to the wheel velocity sensor and is configured to compare the signals of the sensors and to generate a slip signal representative of the degree of slip of the driven wheels. The control circuit is coupled to the comparator circuit and to the brake assisted differential locking mechanism and is configured to generate control signals when a predetermined degree of slip occurs and to apply the control signals to the differential locking mechanism to limit relative velocity between the driven wheels.III. PROPOSED ARCHITECTURE FORBRAKE ASSISTED DIFFERENTIAL LOCKING SYSTEMThe control circuit shown below in Fig.3 is configured to receive signals representative of vehicle operating parameters (condition of slipping of wheels) and to generate control signals corresponding to the desired state of the brake assisted differential locking mechanism for limiting relative velocity between two driven wheels. Sensors are associated with the rear wheels. Control logic executed by the control circuit in a continuously cycled routine determines the desired state of the differential locking mechanism based upon the operating parameters.Fig. 3 PROPOSED ARCHITECTURE OF SYSTEMThe control circuit applies an appropriate control signal to the differential locking mechanism causing engagement or disengagement in accordance with the desired state. Wheel velocity sensor are configured to detect the velocity of the two rear wheels and to generate a wheel velocity signal given as an input to the micro controller. A comparator circuit of the micro controller is coupled to the wheel velocity sensors generate a slip signal representative of the degree of slip of the driven wheel. A control circuit is coupled to the comparator circuit and to the differentia locking mechanism and configured to generate control signals when a predetermined degree of slip occurs and to apply the control signals to the differential locking mechanism to limit relative velocity between the driven wheels by applying artificial braking by actuating the solenoid valves. The control circuit is further configured to disengage the differential locking mechanism when the degree of slip decreases to a level below a predetermined threshold. Wheel velocity sensor is provided for each of the driven wheels, each of the wheel velocity sensors being configured to generate wheel velocity signals and to apply the wheel velocity signals to the comparator circuit, and wherein the control circuit is configured to generate control signals for limiting relative velocity between the driven wheels when slip of any driven wheel exceeds a predetermined threshold value.IV. SPECIFICATIONS FOR ELECTRONIC COMPONENTS MICRO CONTROLLER ANALOG TO DIGITAL CONVERTER SIGNAL CONDITIONER1. Transistor2. DiodeA.MICROCONTROLLERUSE IN BADLS: The microcontroller input is the speed of the two wheel speed sensors. The microcontroller obtains the difference in between the two speed sensor outputs and compares it with the maximum allowable variation. If the variation is beyond the stipulated value, it activates the solenoid valves, thus enabling the auxiliary circuit, avoiding any slipping of the wheels.B.SOLENOID VALVEUSE IN BADLS: They act as ON/OFF switches and control flow of pressurized air into the Auxiliary Circuit. TYPE: Spool TypeC.ANALOG TO DIGITAL CONVERTERUSE IN BADLS: the analog speed signal from the wheel speed sensors is converted into the digital format by the ADC which is supplied as the input to the microcontrollerD. AIR BRAKING SYSTEMIn the air brakes simplest form, called the straight air system, compressed air pushes on a piston in a cylinder. The piston is connected to a brake shoe, which can rub on the wheel, using the resulting friction to slow the train. The pressurized air comes from an air compressor and is circulated by a pneumatic line made up of pipes and hoses. In order to apply the braking force to the brake shoes, compressed air is used. An air brake system in general includes a compressor unit, air-reservoir tank, brake chamber and wheel mechanism.For maintaining adequate braking force at all times even whenthe engine is not running and air-reservoir tank is also necessary. To maintain air pressure, which is small air pump,is used.The compressor takes air from the atmosphere through the filter and the compressor air is sent to the reservoir through the unloader valve, which gets lifted at a predetermined reservoir pressure and relieves the compressor load. From the reservoir the air goes to the various accessories and also to the brake chambers also called the diaphragm units at each wheel, through the brake valve. The control of brake valve is with the driver who can control the intensity of breaking according to the requirements. The unloader valve in the air breaking system serves to regulate the line pressure.V.TESTING AND EVALUATION PARAMETERSThe system has been tested on a SAE BAJA test vehicle at the Automotive Research Association of India (ARAI), pune. This was done keeping in mind that this application would be really helpful for SAE BAJA teams who encounter conditions like slipping of wheels very often. Since vehicle slip is usually about 12-15% while turning, this microcontroller of the system has been designed to active at about 20% slip conditions and deactivates at about 5% slip. The system was tested successfully and the next step would be practical implementation in automobiles after some minor modification.The vehicle was jacked up on one wheel with the other wheel resting on ground surface .This was done to simulate the condition of maximum slipping. This condition will be present in actual conditions when vehicle is negotiating rocky terrain. The engine was started and accelerated. Due to one wheel being in air, the vehicle did not move forward and the jacked wheel rotated excessively. Now the solenoid was activated for the slipping wheel and artificial braking was provided. As a result the torque transmitting capacity of the wheels increases and consequently, the vehicle pulls over the rocks and gravel on the basis of the torque from the individual wheel.VI.COST COMPARISION TABLEAs can be seen from the above table that this system ensures a reduction of more than 50% in the capital investment as compared to the already existing systems.Table I. COMPARISON OF BADLS SYSTEM WITH EXISTING LSD SYSTEM IN THE MARKETEXISTING SYSTEMLIMITED SLIP DIFFERENTIAL(LSD)l TRD LSD Rs.60000l QUAIFE LSD Rs.70000TOTAL-RS 65000 or $1625PROPOSED SYSTEM1. OPEN DIFFERENTIAL :Rs.200002. ELECTRONIC CIRCUIT :Rs.10003. SPEED SENSORS :Rs.75004. CHECK VALVE :Rs.10005. SOLENOID VALVE :Rs.1000TOTAL-RS 31000 or $750VII.ADVANTAGESa) Can be easily implemented in vehicles having pneumatic braking systems with slight modification.b) As electronic circuitry is used, response time, control and reliability are better than the existing systems.c) Low grade lubricants can be used as heat loss is reduced.d) Last but not the least; the system is economical and simple.VIII.LIMITATIONSThe overall efficiency depends on the combined efficiency of both the electronic as well as the pneumatic system.IX.APPLICATIONSThe system can be successfully incorporated in vehicles having pneumatic/hydraulic braking system, with a view to provide improves traction. It can be put to use in especially All Terrain Vehicles (ATV) and vehicles operating in high altitude areas (vehicles for military application) where snow causes excessive loss of traction. This system ensures a reduction of more than 50% in the capital investment as compared to the already existing systems which ensures the cost effectiveness of the endeavour.ACKNOWLEDGMENTSThe author is grateful to Prof. R.B.Patil, Head of Department,Army Institute of technology, India and Dr KC Vora at the Automotive Research Association of India, (ARAI) for their guidance and support.REFERENCES1 Jack Erjavec, Automotive Technology- A systems approach (Delmar Thomson Learning, 2000)2 T.K. Garrett, K.Newton, W.Steeds, the Motor Vehicle (Butterworth Heinmann, 2001)汽车工程的进步:微分锁刹车辅助系统摘要“要组装一辆汽车需要8460个螺栓,要把它全部撒在路上只需要一个螺母。”在过去十年里,汽车技术领域的一些最大进步已经发展安全。由于微处理器速度的提高、小型化和软件开发的刺激,汽车能够继续发展。在提出的这种新方法中,我将用一个电子电路和一个气压回路来自动控制车辆的牵引。在正常情况下,当车辆沿着直线道路行驶,或者两个(后)车轮的转速差低于限制值时,电子电路将不产生信号。这有助于车辆以更好的牵引力控制系统判定转向,因为微分动作是恒定的。但是,如果速度差超过指定限制时,电子电路将产生信号驱动气压回路,使渐进制动发生在速度更快的车轮上,直到它获得牵引力。因此,车轮将永远不会失去牵引力。和已经存在的系统相比,这个系统能确保减少超过50%的资本投资,可以使效益天平倾向于制造公司,并最终倾向于具有成本意识的消费者。关键词:微分锁;牵引力控制;防滑差速器;气压制动1 介绍当你操纵你的车通过一块泥泞的土地时,你真的感到舒适吗?在干燥条件下,当有足够的牵引力时,车轮的扭矩量被发动机和传动装置所限制;在低牵引力的情况下,例如在冰上开车时,扭矩量小于或等于最大值,不会导致车轮在这些情况下打滑。所以,即使一辆车可以产生更多的扭矩,仍然需要有足够的牵引力将扭矩传递到地面。只要轮胎抓住路面,提供一个转动阻力,传动系就能驱动车辆前进。动力传输线上的扭矩由微分装置均匀分配到两个后轮传动轴之间。当一个轮胎在路上遇到滑移点时,它会失去牵引力,旋转阻力下降,同时车轮开始旋转。因为阻力已经下降,传递给两车轮的扭矩就会改变。有足够牵引力的车轮将不再被驱动。如果在这种情况下车辆是静止的,那么只有在滑移点上的车轮能旋转。因此,车辆不能移动。这种情况强调了差速齿轮的重要性。随着牵引力变少,车轮以一个非常高的速度旋转,热量迅速增加,润滑油膜分解,金属与金属表面直接接触,造成接触部分损坏。现在,如果旋转的车轮突然获得牵引力,那么这种牵引力带来的冲击会在组成上对传动轴造成严重损坏。所以,目前我们如何克服这些困难呢?为了克服这些问题,差速器制造商开发了防滑差速器。在汽车应用中,防滑差速器(LSD)是差速齿轮装置的一种调整或派生类型,它允许输出轴存在转速差,但不允许速度差值增加并超出预设量。在一辆汽车中,这样的防滑差速器有时被用来代替标准差速器,他们能以更大的复杂性为代价,传达特定的动态优势。通过考虑在一个车轮完全没有接触地面的标准(或者“开放”)微分的情况下,防滑差速器的主要优势就被发现了。在这种情况下,接触的车轮保持静止,不接触的车轮以两倍预期的速度旋转。在两个车轮上传递的扭矩相等,但不会超过移动车辆所需的阈值扭矩,因此,车辆将保持静止。在典型道路上的日常使用中,这种情况并不太可能发生,因此正常的微分就足够了。但是,对于更高要求的使用,例如驾驶越野,或者高性能车辆,这种情况是不可取的,但是LSD可以解决这个问题。通过限制一对驱动轮的速度差,只需在至少一个车轮上获得些许摩擦,就可以传递有效的扭矩。离合器类型的LSD对驱动轴扭矩作出反应,驱动轴输入扭矩越多,离合器压合越困难,驱动轮被相互连接地更紧密。防滑差速器的劣势a)散热导致润滑油膜破损,金属和金属间的接触发生。b)如果离合器的摩擦片被损坏,整个组成必须被分解。c)要求高质量的润滑。d)由于存在大量的机械部件,可靠性变得更少。e)随着速度的增加,汽车的噪音也会增加。f)复杂并且昂贵。2 提出创新微分锁刹车辅助系统(BADLS)在这种新方法中,有一个电子电路和一个气压回路来自动控制车辆的牵引。在正常情况下,当车辆沿着直线道路行驶,或者两个(后)车轮的转速差低于指定值时,电子电路将不产生信号。这有助于车辆以更好的牵引力控制系统判定转向,因为微分动作是恒定的。但是,如果速度差超过指定限制时,电子电路将产生信号驱动气压回路,使渐进制动发生在速度更快的车轮上,直到它获得牵引力。因此,车轮将永远不会失去牵引力。微分锁刹车辅助系统(BADLS)的控制模块在输入传感器的数据基础之上,捕捉到车轮将要发生滑移的信号,反过来脉冲给该电路的常开进气电磁阀使其关闭,这允许液体进入回路。与此同时,控制模块打开回路的常闭电磁阀,使气压压力作用于刹车片,引起手动制动。一旦受影响的车轮速度和其他车轮速度相同,控制模块就让两个阀门回到他们各自的正常位置,在气压回路中释放剩余压力。Brake Pedal制动踏板Check Valve检测阀门Master Cylinder主缸Brake Wheel制 动 轮图1.BADLS电路示意图工作过程:正常制动系统 手动制动过程(BADLS)当滑移发生正常刹车情况当车速传感器检测到滑移状态驱动制动控制阀微控制器驱动常开电磁阀2微控制器启动常闭电磁阀1和常开电磁阀2电磁阀1保持默认的常闭状态手动制动经空气流入被应用于需要的车轮空气经主电路从主汽缸流出绕过辅助电路上面给出了解释图2.BADLS电路的工作过程上面给出了解释图1所示电路工作过程的流程图。在图2中,第一张流程图展示了正常制动电路的工作过程,而后者展示了BADLS电路工作时的工作过程。在正常制动状态下,电磁阀1处于关闭状态,所以主缸的空气流入主制动电路,通过电磁阀1绕过辅助电路,从而获得正常的刹车行动。在滑动状态下,微控制器启动常闭电磁阀和常开电磁阀2,使手动制动应用于需要的车轮。2.1 BADLS控制模块该系统有一个控制系统、至少两个驱动轮、一个差速器,用来将来自发动机的动能传递到驱动轮,并允许驱动轮间存在相对速度差。该控制系统包括两个车速传感器,一个比较器电路和一个控制电路。车速传感器被用于检测两个驱动轮的角速度并生成速度信号。比较器电路被连接到车速传感器,用于比较传感器的信号并生成一个代表驱动轮滑移程度的滑移信号。控制电路被连接到比较器电路和微分锁制动机构,并用于当一个预先确定的滑移量发生时,生成一个控制信号,将控制信号应用于微分锁机构来限制驱动车轮之间的相对速度。3 微分锁刹车辅助系统的体系结构下面图3所示的控制电路被用于接收代表车辆操作参数(车轮滑动的状况)的信号,以及生成对应于所需的用于限制两个驱动轮间相对速度的微分锁刹车辅助机构状态的控制信号。传感器与后轮相连接,由一个不断循环程序中的控制电路执行的控制逻辑决定了基于操作参数的微分锁机构所需的状态。Analog to Digital Covert模数转换器Reference Vol Regulator参数调节器Micro controller微 控 制 器Output Drivers输 出 驱 动Solenoid valve电 磁 阀Wheel Sensor车 轮 传 感 器图3.提出的系统的体系结构控制电路将一个适当的控制信号应用于微分锁机构,引起根据所需的状态接触或分离。车速传感器被用于检测两后轮的速度并生成一个输入到微控制器的车速信号。微控制器的比较器电路被连接到车速传感器,生成一个代表驱动轮滑移程度的滑移信号。控制电路被连接到比较器电路和微分锁机构并被用于当一个预先确定的滑移量发生时,生成一个控制信号并将控制信号应用于微分锁机
收藏