A Novel High-Efficiency Wheel Loader Power Steering System With Fault-Tolerant Capability

The conventional hydraulic steering system of the wheel loader suffers large energy consumption and significant heating issues caused by the relief and throttling losses during operation. To solve the problems, a novel flow matching principle is proposed, where a fixed displacement hydraulic pump driven by a servo motor is used to supply oil for steering system independently, and the supplied oil is fully consistent with the demanded flow for steering operation. In the study, the rotational speed and angle of the servo motor are determined by the angular velocity and rotational angle of the steering wheel. Thus, both the steering speed and angle of the wheel loader can be controlled. To enhance the safety and reliability of the steering operation, the original steering system is still retained. When the oil supply unit of the new system is out of order, the original system is automatically switched on through a solenoid valve. Based on the simulation and experimental results, by using the proposed system, the energy consumption of the proposed steering system can be reduced by 16% as compared to the conventional steering system, owing to the reduction of throttling loss and elimination of relief loss. In addition, the pressure fluctuation can be reduced from 2 to 1 MPa as compared to the conventional system, indicating an improvement in the stability of the steering operation. Furthermore, the safety and reliability enhancement strategy is also verified experimentally.