  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.
