Modelling And Gear Shifting Control Of Automatic Transimission For Off-road Vehicle

Automatic transmissions (AT) are extensively implemented in the vehicle powertrain systems in order to enhance the propulsion and economic performances. While the automatic gear shifting strategy and the gear shifting quality has a significant effect on the dynamic performance of the AT and vehicle. The hydro-mechanical transmission of heavy commercial vehicles is analyzed and modelled. The AT control strategies of the gear shifting is then designed and optimized considering the large variation of the vehicle load as well as the road slope.The dynamic model of a five speed planetary AT gear box is formulated in conjunction with the models of diesel engine, hydraulic torque converter and vehicle longitudinal dynamics. The models are derived utilizing the Lagrange method and visual work principle. The gear shifting process is then simulated while coupling with the actuator clutch friction model. The oil pressures of the hydraulic clutches are modulated in order to investigate the effects on shifting quality. The simulation results suggested that the characterized parameters of shifting quality were strongly influenced by the clutch oil pressure control. Furthermore, the optimal clutch control is obtained based on the state-space model of the gear shifting process and the quadratic performance index. A smooth gear shifting is then achieved implementing the optimal control strategy.The powerful gear shifting strategy for heavy vehicles is synthesized considering the traditional three parameters, namely, the velocity, throttle angle and acceleration of the vehicle. To improve the vehicle propulsion performance, a novel gear shifting strategy is proposed considering more parameters in terms of the loading, working area and the rate of throttle angle. The powertrain of a30tonnes mining truck is modelled in the MapleSim platform. A typical maneuver is simulated with the traditional as well as the novel gear shifting strategy. The results suggested enhanced propulsion performance with the novel strategy.To improve the economical efficiency of vehicle, a predictive control optimization algorithm is proposed for the heavy vehicle subjected to a fixed routine. The economic gear shifting strategy has been obtained by minimizing the fuel consumption with a prescribed maneuver. Dynamic programming method is utilized to optimize the gear shifting strategy. The Pareto front is further plotted to figure out the nonlinear relationship between the vehicle operation duration and the fuel consumption.The optimal economic gear shifting strategy and multi-parameter strategy are further compared utilizing the established model in MapleSim platform. The results suggested that the predictive control yields better fuel economy while possessing the same productivity.Moreover, a hardware-in-the-loop platform is established in order to evaluate the real time performance of the shifting quality control and gear shifting strategy. The shifting quality control was shown to work well with different conditions. The coupling of the shifting quality control and gear shifting strategy can smoothly follow the shifting gear schedule in real time. Thus the rationality and feasibility of the proposed control strategies are demonstrated.In this thesis, the control strategies of the heavy hydro-mechanical automatic transmission are investigated. The results can provide the theoretical guidance and technical basis for the shifting quality control and gear shifting strategy.