Research On Key Technology Of Control Strategy For AMT System Of Commercial Vehicle

Automated Mechanical Transmission(AMT) is one of the most widely used automatedtransmissions, because it is characterized by simple construction ǐ high transmissionefficiencyǐhigh cost performance and low cost. Besides, the industrialization foundation ofcommercial vehicle AMT is very favorable, and the prospect of commercial vehicle AMT inbroad market is also expansive.By unremitting efforts of industrial circles for many years, fundamental function ofdomestic AMT technology is very mature, but the product of AMT still have large gap withoverseas product. Because the product of AMT must have intelligent feature, which canrecognize and adapt to vehicle conditionǐroad information and the driver’s intentionautomatically, and which is highly steadyǐreliable and self-adaption. The control ofshiftingǐstarting and shift-decided are the key control elements of AMT system. During theprocess of product realization of AMT, there are different technical difficulties in thesecontrol elements, which need further optimize and improve.In this thesis, combining with technical difficulties which were met in developmentprocess of commercial vehicle AMT of the technical center of FAW, in-depth research ismade on control strategy of shiftingǐcontrol strategy of startingǐcontrol strategy of and shiftdecision-making system of commercial vehicle AMT, and the research results are verified inthe vehicle.In this paper, the main contents are as follows:1Combining with technical difficulties which were met in development process ofvehicle, according to the inherent characteristic of the system, aiming for Low Impact andless wear and tear in shifting process, based on integrated control of engineǐclutch andtransmission, referencing abroad advanced control concepts, the control strategy of shifting process is corrected and perfected. Aiming to three stage of shifting process, the controlstrategy of shifting process which is fitted vehicle requirement is proposed Innovatively,which is including control strategy of disengaging clutchǐcontrol strategy of shifting andcontrol strategy of engaging clutch. And the control strategy of shifting with synchronizerproposes that shifting force can be controlled by controlling the angular acceleration of theinput-shaft, the control strategy of shifting without synchronizer proposes that the shiftingaction is executed under the target speed, which improves shifting success rate, the controlstrategy of engaging clutch proposes that revolving speed difference of clutch is eliminatedby controlling engine speed, the clutch is engaged directly and open-loop, which can reduceutilization of exhaust valves, and prolong the working life of exhaust valves, and cut downthe control difficulty of engaging clutch in shifting process.2According to the inherent overshoot characteristic of the clutch actuator, the controlstrategy of Intake compensation which is applied to precise position control of clutchactuator is proposed, which improve the accuracy of position control of clutch actuator.Combining with the shortage of the current control strategy of starting, some key controlfactor of starting control is determined, such as control principles of engineǐspeed of engineǐengagement position of clutchǐengagement speed of clutch and so on. In order to minimizethe slipping frictional power, the control principles of engine constant speed in startingprocess is derived theoretically by using the first integral mean value theorem. Consideringthe starting requirement of driverǐcharacteristic of engine and the slipping frictional power,the engine speed point of the engine constant speed control principles is determined.According to dynamics characteristic of starting process and torque transmissioncharacteristics of clutch, engagement position of clutch is determined. With the constraintcondition of jerk, engagement speed of clutch is determined. Finally, based on integratedcontrol of engine and clutch, considering starting requirement of driver and constraintrequirement of jerk, an optimal control strategy of starting is proposed, which can satisfystarting requirement of driver and starting quality, and can finish the starting process quicklywith minimal slipping frictional power. 3The shortage of the current shift decision-making control strategy is caught sight bysome technical difficulties which is met in development process of vehicle, such as shiftcycle in uphill working conditionǐcontinuous downshift until stop in steep climb or largeangle steering working condition, the necessity of vehicle mass estimation and runningresistance estimation for the commercial vehicle is analysed. Then two methods of vehiclemass estimation is proposed without or with increasing little vehicle cost, which islongitudinal dynamics estimation method and longitudinal acceleration sensor method, andaccording to these, the shift decision-making control strategy based on driving force andrunning resistance, which can eliminate the shortage of current shift decision-making controlstrategy and optimize shift decision-making control strategy, and made efforts for realizingintelligent shift finally.4The key control strategy is verified by bench test and vehicle test. The bench test isconsisted of the precise position control strategy of Intake compensation for clutch actuatorand the control strategy of up-shift and down-shift of AMT system without synchronizer.The vehicle test includes three parts which are vehicle starting test with different enginepedalǐvehicle shifting test of AMT with synchronizerǐvehicle shifting test of AMT withoutsynchronizerǐjumping upshift test of no-load vehicleǐ jumping downshift test of fullyloaded vehicle and vehicle mass estimation. The test results show that the control strategy ofthe AMT system of commercial vehicle is satisfactory.