A novel Algorithm for Hydrostatic-mechanical Mobile Machines with a Dual-Clutch Transmission

Mobile machines using a hydrostatic transmission is highly efficient under lower working-speed condition but less capable at higher transport velocities. To enhance overall efficiency, we have improved the powertrain design by combining a hydrostatic transmission with a dual-clutch transmission (DCT). Compared with other mechanical gearboxes, the DCT avoids the interruption of torque transmission in the process of shifting without sacrificing more transmission efficiency. However, there are some problems of unstable torque transmission during the shifting process, and an excessive torque drop occurring at the end of the gear shift, which result in a poor drive comfort. To enhance the performance of the novel structural possibility of powertrain design, we designed a novel control strategy for the motor torque and the clutch torques during the shifting process. The controller's task is tracking the target drive torque and completing the gear shift as quickly as possible with acceptable smoothness requirements. In the process of the controller design, a specific control algorithm is firstly designed for a 10 ton wheel loader. The model-based simulation has validated the control effect. As a result, the control strategy employing clutch and motor torque control to achieve a smooth shifting process is feasible since drive torque is well tracked, and highly dynamical actuators are not required. Furthermore, only two calibration parameters are designed to adjust the control performance systematically. The novel control strategy is generalized for other mobile machines with different sizes.