Optimization of Shuttle Shifting Process of Agricultural Tractor using simulation environment

Transmission tuning, is beneficial for optimizing performance, improving fuel efficiency, smoother shifting and enhancing drivability particularly when a vehicle's power output is increased or for specific driving conditions. Especially in the offroad and agricultural machines, transmission tuning is vital to significantly improve the vehicle performance during different operations. The process of transmission tuning is quite time consuming as multiple tuning iterations are required on the actual vehicle. A significant reduction in tuning time can be achieved using a simulation environment, which can mimic the actual vehicle dynamics and the real time vehicle behavior. In this paper, tuning during the forward and reverse motion of the tractor is described. A two-level PI control-based shift strategy is designed and implemented. In the two-level PI control, the first level calculates the transmission valve pressure setpoint based on the tractor acceleration error. In addition, the second level identifies the valve current based on the valve pressure error. The dynamics model of the tractor powertrain, which is called as plant model was developed and a closed loop environment is established with the Simulink model. The tuning of the PI gains and the testing are performed in the plant model environment. The optimum PI gains are identified after multiple test iterations in the mentioned environment. The software, then tested on the actual tractor with the optimum values and verified the shuttle shift performance. The results show that quick and comfortable shuttle shifts are achieved during the process of moving from the forward to reverse directions and vice versa.