Hierarchical control strategy for a hydrostatic transmission system in tracked articulated all-terrain vehicles

The four-pump/four-motor distributed hydrostatic transmission (HST) system of a heavy tracked articulated all-terrain vehicle (TA-ATV) exhibits strong nonlinear and time-varying coupling among engine output, hydraulic power, and track loads. Such coupling limits conventional segmented control, resulting in pressure oscillations, inefficient power utilization, and sluggish acceleration. This study proposes a VCU–ECU–PCU–MCU hierarchical control strategy that integrates vehicle-demand scheduling, engine–hydraulic power coordination, four-track coordination, and local pump/motor displacement regulation. Map-based feedforward, efficiency compensation, and PID/PI feedback are employed to adapt the displacement commands to variations in engine state and external load. In the acceleration simulations, the proposed strategy reduced peak system pressure and peak hydraulic loss by 21.4% and 16.2%, respectively, relative to MPC. Under the ±15° grade transition, it reduced peak pressure and maximum slip by 49.7% and 68.7%, respectively, although the uphill speed response remained conservative. Full-scale tests further showed that the 0–30 km/h acceleration time decreased from 32 to 25 s and the pressure-fluctuation variance from 4.46 to 3.49. These results demonstrate improved power coordination, dynamic response, and hydraulic stability over varying operating conditions.