Research On Control Technology Of AMT With Torque Assist Mechanism For Commercial Vehicle Based On Torque Assist Characteristics

The working environment of commercial vehicle is terrible and the load of commercialvehicle is very heavy, which requires better operating skill and driving experience of thedriver. During the vehicle movement, the driver need frequent starting, shift and brake, withabnormal heavy workload. It is probable to produce fatigue driving, which threatens thesafety of the vehicle. In addition, the commercial vehicle owns a high level of fuelconsumption due to large load. The fuel economy will be seriously affected, if the optimalgear under different working conditions is not selected., Therefore, the installation ofautomatic transmission has become a trend in the commercial vehicle. The automatictransmission can significantly simplify the driving process, reduce the driver’s workload andimprove the safety of the automobile. At the same time, the automatic transmission canensure that the car is always in the best working condition, which reduces the abrasion ofthe components of the transmission system, improves fuel economy, and reduces emissionstargets.Based on the traditional mechanical transmission, AMT（Automated MechanicalTransmission）installs electronic equipments on a common actuator, which preciselycontrols engine, gearbox and clutch, to realize automatic operation of starting and shiftingprocess of automobiles by the electronic control unit TCU. Compared with other automatictransmissions, AMT not only has a high transmission efficiency, simple mechanism,compact structure and low cost, but also the production of succession, according to theordinary MT production line with a little modification on the line, low manufacturedifficulty. In commercial vehicle field, especially the heavy commercial vehicle, AMT isequipmented more frequently. But the traditional AMT has an inherent defect, with torquedefects when shifting.On the basis of AMT, the AMT with torque assist mechanism installs a torque assistmechanism between the intermediate shaft and output shaft, which transmits torque duringthe shift process. The system has two clutches. One is a starting clutch, located between theengine and the gearbox, which works only in the starting process. The other is the auxiliaryclutch, transmiting torque in the shift process.Based on the above background, in this paper the torque assisted AMT is applied to a commercial vehicle. The control technology of AMT with torque assist mechanism forcommercial based on torque assist characteristic vehicle are deeply studied, the maincontents are as follows:(1) Vehicle system model is built, using MATLAB/Simulink as the software platform.According to modular modeling method, the whole system model is divided into three parts:the vehicle transmission system hardware model, the driver model and the controller model.A commercial vehicle installing AMT with torque assist mechanism is analyzed and itssimulation model is built. By comparing the simulation results and experimental data, thevalidity of the simulation model of vehicle system is verified from two aspects of power andeconomy, which lays the foundation for the development of the control strategy of AMTwith torque assist mechanism for commercial vehicle.(2)The structure parameters of assist clutch are designed according to the performancerequirement of assist clutch. AMT with torque assist mechanism is studied on dynamics andkinematics when the assist clutch and transmission are in different states. According to thedynamic and kinematic results, the torque assist characteristic of AMT with torque assistmechanism is analysed when the engine is in different states.(3)Combined with the evaluation index of the shifting process, the shifting dynamicsof AMT with torque assist mechanism is analyzed, which determines the dynamic modelduring the shift process and establishes the control strateg based on torque assisitcharacteristic. establishes the transmission ratio of torque assist mechanism, formulates theshift quality control strategies. Torque interruption is avoided by controlling the engine,gearbox and assist clutch in phase. The vehicle system model is constructed inMATLAB/Simulink and the simulation analysis of the shifting process is carried on.According to the simulation results, the shift control strategies of AMT with torque assistmechanism is formulated in this paper, which can avoid the power interruption in the shiftprocess, improving shift quality.(4)On the basis of analyzing the transfer characteristic of auxiliary clutch torque, theauxiliary clutch torque model is built. Based on orthogonal neural network control, theauxiliary clutch pressure control system is built, the simulation of pressure control of theauxiliary clutch is analyzed. According to the simulation results, the clutch pressure controlsystem of assist clutch can achieve the fast tracking assisted of target pressure.(5)The electric control scheme of vehicle system with auxiliary clutch is designed. The XC2785micro-controller is used to develop the hardware system, which builds the softwarearchitecture of control system and develops the software and hardware of the control system.The test data acquisition system is introduced. The vehicle test is carried out to verify theeffectiveness of control strategy.The theory analysis and vehicle test are combined in this paper to deeply study controltechnology of AMT with torque assist mechanism for commercial vehicle based on torqueassist characteristic. According to the simulation results and the experimental data, AMTwith torque assist mechanism is able to transmit torque in the shifting process, avoid powerinterruption and improve shift quality, which is significant for the development of automaticmechanical transmission for commercial vehicle.