TY220型拖拉机离合器设计【说明书+CAD】
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TY220
拖拉机
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TY220型拖拉机离合器设计【说明书+CAD】,TY220,拖拉机,离合器,设计,说明书,CAD
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International Journal of Automotive Technology, Vol. 12, No. 5, pp. 763768 (2011)DOI 10.1007/s1223901100887Copyright 2011 KSAE12299138/2011/06016763TORQUE CONTROL OF ENGINE CLUTCH TO IMPROVETHE DRIVING QUALITY OF HYBRID ELECTRIC VEHICLESH. S. HWANG1), D. H. YANG2), H. K. CHOI2), H. S. KIM2) and S. H. HWANG2)*1)Korea Automotive Technology Institute, 74 Yongjeong-ri, Pungse-myeon, Cheonan-si, Chungnam 330-912, Korea2)School of Mechanical Engineering, Sungkyunkwan University, Gyeonggi 440-746, Korea (Received 28 June 2010; Revised 24 March 2011)ABSTRACTAs a powertrain for hybrid electric vehicles (HEVs), the automatic transmission (AT) is not only convenient forthe driver but also reduces hybridization costs because the existing production line is used to produce the AT. However, it haslow fuel economy due to the torque converter. To overcome this disadvantage, this paper studies HEVs equipped an ATwithout a torque converter. In this case, additional torque control is needed to prevent the driving quality from deteriorating.This paper suggests three different torque control methods and develops a simulator for an HEV that can simulate the dynamicbehaviors of the HEV when the engine clutch is engaged. The HEV drive train is modeled with AMESim, and a controllermodel is developed with MATLAB/Simulink. A co-simulation environment is established. By using the developed HEVsimulator, simulations are conducted to analyze the dynamic behaviors of the HEV according to the control methods.KEY WORDS : Hybrid electric vehicle (HEV), Engine clutch, Driving quality, Drive shaft torque, Torque control, Enginecontrol, Motor control1. INTRODUCTIONThe need for eco-friendly vehicles such as hybrid electricvehicles (HEVs) has increased rapidly due to resourceexhaustion and increased awareness of environmentalissues. The Toyota Prius first went on sale in Japan in 1997,making it the first mass-produced hybrid vehicle. It is soldin more than 40 countries and regions, with its largestmarkets in Japan and North America. In 2008, globalcumulative Prius sales reached the 1 million salesmilestone, and by early 2010, the worldwide cumulativesales reached 1.6 million units (Toyata, 2009; InternationalBusiness Times, 2009).The Toyota Prius has the Toyota Hybrid System (THS),which has a single power-split device (incorporated as asingle 3 shaft planetary gearset); thus, it can be classified asan input-split system because the power of the engine issplit at the input to the transmission. This power-splitsystem makes the setup very simple in mechanical termsbut has some drawbacks. For example, the maximum speedis mainly limited by the speed of the smaller electric motor.Additionally, the transmission efficiency depends heavilyon the amount of power being transmitted over theelectrical path because multiple conversions cause the pathto have a lower efficiency than the purely mechanical path.In particular, in higher speed regions, the efficiency, therefore,drops below that of a generic automatic transmission with ahydrodynamic coupler. To overcome these drawbacks, it isnecessary to develop a new hybrid electric system that canreduce additional costs due to hybridization and can beproduced using the existing production line effectively(Muta et al., 2004).As a powertrain for the HEV, the automatic transmission(AT) has some advantages, including a smooth start,convenience for the driver and safety. Furthermore,because the existing production line can be used to producethe AT, the hybridization costs can be reduced. AT hasexcellent accelerating and shifting performance because ofthe torque converter. However, because the torqueconverter transmits power with low efficiency, it serves asan obstructing element in the improvement of fueleconomy when it is applied to the HEV. To overcome thisdefect, some studies have focused on an AT without thetorque converter. Without the torque converter, additionaltorque control is required to prevent the deterioration ofdriving quality upon engagement of the engine clutch. Oilpressure control methods upon engagement of the engineclutch have been investigated (Kim et al., 2008a).Improvement of the shift quality (SQ) with motor torquecontrol when shifting gears has also been investigated(Kim et al., 2008b).In this study, an HEV simulator is developed that cansimulate the dynamic behaviors of the HEV equipped withan AT without a torque converter upon engagement of theengine clutch. To reduce the torque fluctuation that causes*Corresponding author. e-mail: hshme.skku.ac.kr764H. S. HWANG et al.low driving quality upon engagement of the engine clutch,three different torque control methods are suggested:sychronized control of the engine and motor speeds beforeengagement of the engine clutch; motor torque control afterengagement of the engine clutch; and combined control ofthe engine and motor torques. Simulations were performedto analyze the dynamic behaviors of the HEV according tothe control methods.2. HEV SIMULATION MODELFigure 1 illustrates the structure of the test HEV. It is a 2-shaft parallel hard HEV with an AT. It can be operated inelectric vehicle (EV) mode, in which only the motor isdriven, and can be changed into the HEV mode bycontrolling the engine clutch installed between the engineand the motor.2.1. Engine, Motor and ISG Simulation ModelAn engine has complex characteristics depending on the fuelinjection time, ignition period and combustion characteristics,for example. In this paper, a simple model of the engine isused that approximates a torque-generating device with steadystate characteristics. The vibration characteristic of the crankshaft and that of the simple model are considered to simulatethe explosive torque vibration of the engine.The driving motor and integrated starter generator (ISG)are modeled as a 1st order transfer function by approximatefitting curves with a steady state torque characteristic withrespect to speed considering the time delay. Figure 2 showsthe characteristic curves of the motor and ISG used in thispaper.2.2. Torsional Damper and Engine Clutch Model The engine clutch of the HEV in this paper uses theAMESim model, which is a wet multi-disk clutch. Thetransmitted torque and friction coefficient are calculatedusing the following equations (Deur et al., 2005; Yang etal., 1998).(1)(2)where is the friction coefficient, s and k are the staticand dynamic friction coefficients, N is the number of clutchplates, P is the acting pressure on the clutch, Ac is the actingarea of the clutch, Ro and Ri are the external and internalradii of the clutch, is the relative rotational velocity dueto slip, and s is the rotational velocity in the steady state.The operation of the engine clutch has the following 3different ranges: the disengaging range from the powershaft of the engine; the slip range as power is transmitted;and completely engaged range between the engine andmotor axes. A torsional damper is modeled as a spring and a damperwith various stiffnesses w.r.t. the relative twisting anglebetween the torsional damper ends. Figure 3 shows thehysteresis characteristic of the torsional damper.2.3. Automatic Transmission and Vehicle Dynamics ModelVehicle dynamics modeling is performed using AMESim,which is used widely with vehicle and hydraulic models. Inthe vehicle model, the inertia, stiffness and damping effectare considered to describe the dynamic behaviors of theTtransNAP23- -Ro3Ri3()Ro2Ri2()-=sk()s-kexp=Figure 1. Structure of a parallel HEV with AT.Figure 2. Characteristic curves of the motor and ISG.Figure 3. Characteristic curve of torsional damper.Figure 4. Schematic diagram of an automatic transmission.TORQUE CONTROL OF ENGINE CLUTCH TO IMPROVE THE DRIVING QUALITY 765HEV in detail. The HEV has adopted the 6 speed automatictransmission, as shown in Figure 4. Figure 5 shows theHEV powertrain model that is used in AMESim. Thetransmission was constructed with three PGs (PlanetaryGears), OWC (One Way Clutch), LRB (Low and ReverseBrake), UD/B (Under Drive Brake), and OD/C (OverDrive Clutch). Figure 6 shows the results of the comparison of the driveshaft torque between experiment and simulation, which areused to validate the vehicle model.The simulation results were obtained with the sameinput conditions for the engine torque, motor torque, andoil pressure profile. In the test condition, the acceleratorposition is 100%, which is the wide open throttle (WOT)condition, and the driving mode and gear shifting conditionsare included.2.4. Controller Model The controller was modeled using MATLAB/ Simulink,and the co-simulation environment was established. Thehybrid control unit (HCU) determines the torquesdemanded for the engine management system (EMS) andmotor control unit (MCU); these torques are calculatedaccording to the drivers command and driving strategy(Ahn et al., 2009). This study applied a simple drivingstrategy because we were only concerned with the effect ofvariations of drive shaft torque on the driving qualityduring engagement of the engine clutch. The drivingstrategy used is shown in Table 1, which shows theoperating conditions and actions of the four driving modes.The EMS transmits the throttle open signal, which iscalculated according to the demand torque from the HCUto the engine. The TCU transmits an oil pressure profilesignal according to the gear shifting schedule, whichdepends on the driving mode (e.g., the EV or HEV mode),to the engine. The MCU transmits the demand torques,which are transferred from the HCU to the motor and ISG.Figure 7 shows the HEV controller model built withMATLAB/ Simulink.Figure 5. HEV Powertrain model used in AMESim.Figure 6. Comparison between the experiment and thesimulation.Table 1. Driving strategy.DrivingmodeCondition and actionEVmodeCondition 0 APS thresholdActionStarting engine and engine clutch is on slip conditionHEVmodeCondition Engagement of an engine clutchActionDriving motor and engine simulta-neouslyBrakingmodeCondition BPS 0ActionRegenerative braking according to conditions APS: Accelerator Position Sensor (%)BPS: Brake Position Sensor (%) Figure 7. HEV controller model built with MATLAB/Simulink.766H. S. HWANG et al.3. SIMULATION RESULTSVarious simulations were performed under the followingconditions with the applied torque control algorithms toreduce the torque vibrations of the drive shaft. Table 2shows the various simulation conditions according to thecombination of engine and motor controls.The input condition of the accelerator pedal is a stepfunction of 100% APS.3.1. Without ControlFigure 8 shows the simulation results without the controlalgorithm to decrease the vibrations upon engagement ofthe engine clutch. During the mode change, the enginetorque is constant according to the throttle position, and themotor torque is determined according to the APS.Figure 8 (a) shows the speeds of the engine and themotor as well as the drive shaft torque, which is a referencevalue for the driving quality in this paper. In this figure, thepoint at which the engine speed coincides with the motorspeed is the point of complete engagement of the engine.The variation of the drive shaft torque can be observedfrom the slip range just prior to the complete engagementpoint. Figure 8 (b) shows the mean output torques of themotor and the engine. The negative values of initial enginetorque are the torque losses due to the friction loss of theengine, and the ISG covers the loss torque.3.2. Engine Speed Control Prior to EngagementThe engine speed control method controls the tracking ofthe motor speed prior to engagement of the engine clutchafter the engine is started. This control algorithm calculatesthe engine output torque using the feedback on the motorspeed and then generates the command signal for the enginethrottle position based on the calculated torque (Figure 9).Figure 10 shows the simulation results from enginespeed control. These results illustrate that the drive shafttorque with control has less fluctuation than one withoutcontrol after engagement of the engine clutch.3.3. Motor Torque Control during EngagementMotor torque control is applied during engagement; itsblock diagram is shown in Figure 11.Figure 12 shows the simulation results with motorTable 2. Simulation conditions.NoSimulation conditions1Without control2Engine speed control prior to engage3Motor torque control during engaging4Combination of engine and motor torque controlsFigure 8. Simulation results without control.Figure 9. Control block diagram of the engine torque control.Figure 10. Simulation results with engine speed control.Figure 11. Block diagram of the motor torque control toreduce torque fluctuation.TORQUE CONTROL OF ENGINE CLUTCH TO IMPROVE THE DRIVING QUALITY 767torque control from the feedback on the drive shaft torqueduring engagement. Before engagement of the engineclutch, the results on the engine speed, motor speed anddrive shaft torque are similar to those without control, butafter engagement of the engine clutch, they show anincrease in the reduction in the torque fluctuation becauseof the motor torque control.3.4. Combination of Engine Speed and Motor TorqueControls Figure 13 shows the simulation results obtained from theapplication of the combined engine speed and motor torquecontrols. The results are similar to those obtained from theapplication of engine speed control before the engagement,and they are similar to those from the motor torque controlafter the engagement. The remaining vibration of the driveshaft torque disappears after the engagement of the engineclutch.4. ANALYSIS OF SIMULATION RESULTSThe simulation results of the various control methods aboveare compared in terms of vehicle speed and acceleration ofthe HEV.Figure 14 shows the oil pressure profile of the engineclutch from the start of the engine to the completeengagement of the engine clutch. All the same pressureprofiles are provided as simulation inputs with the variouscontrol methods.Figure 15 and Figure 16 show the vehicle speed andacceleration according to the various control methods. Thetrend in the variation of the acceleration results is similar tothat of the drive shaft torque. From the vehicle speed graph,Figure 12. Simulation results with motor torque control.Figure 13. Simulation results with a combination of enginespeed and motor torque controls.Figure 14. Oil pressure profile acting on the engine clutch.Figure 15. Comparison of vehicle speeds.Figure 16. Comparison of vehicle acceleration.768H. S. HWANG et al.the acceleration performances of the vehicles with controlare worse than those without control. This performancedecrease is caused by the reduction of the engine torqueaccording to the control algorithm after the start of theengine. In the case of torque control, the vehicle speedincreases slowly due to driving torque reduction aftercomplete engagement of the engine clutch.Table 3 shows the fluctuation in vehicle acceleration,which indicates differences in peak to peak values whilethe engine clutch is being engaged and the speed when theengagement of engine clutch is completed at a relative timeof 1. The values are listed alongside the control methods,and they are expressed as a percentage of the resultswithout control.As a result, although the engine and motor control maydecrease the accelerating performance of a vehicle a little,they can improve driving quality by reducing the torquefluctuation of the drive shaft. Therefore, automotiveengineers can design the controller using an appropriatecontrol method based on their judgment of the tradeoffbetween acceleration performance and driving quality.5. CONCLUSIONIn this paper, an HEV equipped with AT without a torqueconverter is modeled, and the dynamic characteristics ofthe HEV are investigated based on the control method ofthe engine and motor. An HEV simulator was developed inwhich AMESim was used to model the HEV drive trainand MATLAB/Simulink was used to develop the controllermodel; a co-simulation environment was established. To reduce the torque fluctuation, which is responsiblefor low driving quality at the engagement of the engineclutch, three different torque control methods weresuggested. The drive shaft torque and vehicle speed werecompared and analyzed according to the control method.From the simulation results, although the engine andmotor controls may reduce the acceleration performance ofa vehicle a little, they contribute to the improvement ofdriving quality by reducing the torque fluctuation of thedrive shaft. In the future, automotive engineers will be ableto design the controller considering design factors such asacceleration performance and driving quality by using theHEV simulator.ACKNOWLEDGEMENTThis research was financially supportedby the Ministry o
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