To improve the pass ability of heavy-duty tractors

a hydraulic hybrid heavy-duty tractor is equipped with a hydraulic hub motor auxiliary drive system on front axle based on the traditional structure. On this basis

an engineering control strategy is developed to achieve time-sharing all-wheel-drive control. The strategy ensures the smooth switching of the system mode by identifying the working states of the two sets of power systems and the driving intention

and the controlling of hydraulic system to intervene and exit at the right time. In each mode

the pump displacement is controlled rationally

and a good wheel speed tracking in the assist mode is achieved. The actual vehicle test results of the control strategy show that the driver's operation intention is accurately identified

the mode switching and shift smoothness are good. The two systems work in harmony and do not interfere with each other

and the driving safety is guaranteed. The variable pump displacement response reasonably in each mode

and the wheel speed tracking method is effective. The actual vehicle test verifies the feasibility of the hub hydraulic hybrid system and the rationality of the strategy proposed.