Hill-start Control Strategy Of Heavy Off-road Vehicles Equipped With AMT Based On Multi-signal Integration

Automatic mechanical transmission (AMT) is based on the dry clutch and mechanicaltransmission.Hill-start process is the difficulty of AMT control because it involved incoordinated control of the engagement of the clutch,the engine speed and the parkingbrake,etc.Especially for heavy-duty off-road vehicles,it must have the ability to start at60%slope to ensure its off-road performance.First,a more comprehensive understanding of requirements for hill-start is achievedafter analyzing security,sliding friction work,convenience of driver’s operation and someother requirements during the process of hill-start.The powertrain model of the hill-startprocess is established based on the related assumptions and conditions.Some key points ofhill-start are got after analysis of torque transmitted and vehicle status during the process ofhill-start. Hill-start Aid System (HAS) is designed based on the working principle of thevehicle parking brake systems and domestic and foreign research status and condition ofhill-start.Working principle of the modificated parking brake system is analyzed and someparameters of the Hill-start Aid System are achieved,which provides some basis for thedevelopment of subsequent control strategies. Hill-start control strategy of heavy off-roadvehicles equipped with AMT based on multi-signal integration is proposed according to theprevious conclusions,which provides a good foundation for the follow-up research work.In order to estimate the clutch transmitting torque more accurately,the structure andworking principle of diaphragm spring clutch and characteristics of system works anddynamics for clutch are carefully analyzed.Advantages and disadvantages of different kindsof methods to estimate the clutch transmitting torque values are studied and compared，what’s more, some necessary verification tests are implemented.The clutch control strategy is designed based on the existing experimental vehicleplatform and the vehicle can start on different slopes successfully. To solve the problem thatclutch is badly worn during the hill-start process of big slopes,the analysis of reducing thefriction work based on the clutch control strategy and hill-start data before.The new clutchcontrol strategy for hill-start is designed and satisfactory results are achieved when vehicletests are carried out on different big slopes.