| The research and development of underground transportation vehicle has always been the hot spot of the mine machinery field. With people's continuous attention to environment protection, electric power driven mine vehicles have been favored by the enterprises. At the same time in order to adapt to complex road environments, reduce space requirements for turning the channel, the articulated structure is widely used in mine vehicles. The truck studied in this paper is electric driven and the front and rear frame are connected by hinge joint. As one of the most important sub-system of vehicle, steering performance is closely related to the driving safety and stability. The research related to steering system is of great implications in raising the vehicles' overall performance and parts service life to ensure safety in production of mining enterprises.This paper first introduced the vehicle's structure and principles of the steering system. The priority valve and hydraulic redirector are two key components for hydraulic system. The working principles of them are analyzed and the mathematical models under static conditions are established to build AMESim hydraulic models.Secondly, the movement of articulated steering mechanism is analyzed and the mathematic expressions of steering cylinder stroke and arm difference, cylinder output torque are obtained. The cylinder stroke difference and output torque are selected to build objective function and coordinates of hinge point between cylinder and frame are selected as independent variables. The MATLAB genetic algorithm function and iSIGHT multi-objective optimization tools are used to optimize the articulated steering structure. Results curves show that the oil cylinder output torque increases significantly and oil cylinder stroke depresses significantly after the optimization. The design of experiments show the influence degree of different independent variables to the objective function.Finally, the dynamics model is established according to simplified structure of the vehicle. When using hydraulic cylinders to steer, the effectiveness of the optimization work is verified by analyzing simulation results. The comparison of simulation data proves that the force condition of articulated points is getting better and the hydraulic cylinder pressure is reduced after the optimization. The study of using electric-wheel differential steering gets the relationship between the time needed for a minimum turning radius and the differential steering drive torque within a certain range. It shows that the electric-wheel differential steering can reduce the articulated point stress significantly by the comparison of hydraulic cylinders steering and electric-wheel differential steering.In this paper, electric-wheel differential steering is studied and the feasibility of the scheme is made clear. Within a certain range, a conclusion can be made that the greater the differential steering drive torque is, the smaller the time needed for minimum turning radius And the use of electric-wheel differential steering can effectively reduce the force of hinge points. The iSIGHT multi-objective optimization tool is applied during the optimization process of articulated steering mechanism and the influence degrees of four independent variables on the steering properties are identified by design of experiments. Related methods and conclusions have a certain reference value to the design of articulated vehicle steering system and electrical-wheel differential steering. |
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