Research On The Hydrostatic Auxiliary Drive Of Front Axle For Mining Trucks

As a main transportation facility for mine, mining truck works on the extremely bad mine road, therefore it is frequent to encounter the low adhesion coefficient road, such as ice road, snow road and mud road, which can cause the driving performance decrease because of the wheel slip. In order to improve the driving capability of the mining truck, a hydrostatic auxiliary driving system is added to the original 6×4 mining truck in this paper.In overall consideration of operational states of mining trucks, two hydraulic wheel hub motors with the free wheel function are served as terminal components for driving front wheels, of which revolving speed is controlled via the displacement adjustment of a variable pump. Thereby the structure arrangement plan for the hydrostatic auxiliary driving system of front axle is designed, and the parameters of the major components in the hydrostatic system are matched. Afterwards the hydraulic circuit with four operating mode(free wheel mode, auxiliary drive mode, auxiliary brake mode and lift mode) is designed in AMESim software, subsequently the functionalities of the hydrostatic system are simulated, and the simulation result meets the functional requirements for the mining truck.On the basis of revolving speed control model of auxiliary driving wheel hub motor, PID series compensation is adopted to control that the revolving speed of main driving wheels is tracked by that of the hydraulic motor, to ensure that the main driving wheels and the auxiliary driving wheels revolve coordinately after the hydrostatic auxiliary driving system is added to the mining truck. Then neural network supervisory control is performed together with PID feedback control, so as to enhance the stability and adaptive capability of the control system, which shapes the control method of feedback + feedforward. Later, the control method is simulated in the form of MATLAB script, and the result shows that the revolving speed of the hydraulic motor can be controlled precisely by the input reference voltage in the revolving speed control model of auxiliary driving wheel.In order to ensure that the hydrostatic auxiliary driving system can switch on and switch off reasonably, automatically and promptly when the mining truck encounters different road surfaces, the control strategy is proposed that the auxiliary system switch is decided by the average slip ratio of main driving wheels and the current gear stage. For the sake of calculating the slip ratio accurately, the Unscented Kalman Filter is employed to accurately estimate the truck speed and implement the filtering function meanwhile.Finally, the whole vehicle dynamic model, the Pacejka89 tire model, the vehicle speed estimation model, hydrostatic auxiliary driving system switch model as well as wheel speed tracking model are established in MATLAB/Simulink. Then the related simulation is performed, and the result indicates that Unscented Kalman Filter can accurately estimate the truck speed and implement the filtering function simultaneously, that the hydrostatic auxiliary driving system can switch on and switch off promptly under the setting circumstance, and that the driving force of the mining truck can be increased when the hydrostatic auxiliary driving system is switched on.