| As one of the most used machines in construction projects, wheel loader has the problems of high fuel consumption and seriously emissions. On the one hand, the hydraulic steering system, when using a fixed displacement pump, will produce large energy losses. On the other hand, the action of steering is frequent during working process. Therefore, reducing the energy consumption of steering system is becoming one of the key research directions.Currently, small wheel loader generally uses the hydraulic steering system of value control loading sensing. Although the pressure of the system can match the load, the flow of the fixed displacement pump is proportional to the engine speed and can’t match the varied load that leads to energy losses. For this issue, a new steering control method of electro-hydraulic flow matching, adopting a servo motor to drive a fixed displacement pump independently, is proposed. By this method, the ratio between the cycle number of motor and the angle of steering wheel changes to a certain value. The speed of motor will level off if there is no steering movement, so that the system energy consumption is reduced. Meanwhile, this system is paralleled with primal system by adopting electromagnetic valve in case of motor fault so that the primal system will be switched to operate. In addition, an accumulator is also added to the new principle to reduce the installed power of servo motor. Finally, the power of pump is improved.The loader co-simulation model built by the multidisciplinary software SimulationX is used to simulate and calculate the characteristics of the steering system in several typical steering conditions. The model of steering gear, priority valve and tire have described specifically during modeling.Firstly,the load sensing steering system is calculated in SimulationX under several steering conditions. Meanwhile, testing system platform is built to prove the accuracy of simulation model. And the accuracy of simulation model is verified by comparing the results of simulation and experiment. At last, the simulation model is used on the new steering system. By comparing the energy efficiency between original steering system and the new electro-hydraulic flux matching system, the simulation results show that, using the new system, the energy consumption under no-load with low and high speed respectively can be reduced about 36% and 37%. And the energy consumption under positive and unbalance loading respectively with middle speed pivot steering condition can be reduced about 39% and 28%. In addition, the new system can reduce energy consumption by about 38% and 31% under positive and unbalanced loading respectively with middle speed walk steering condition. This is mainly due to the new steering system can avoid the situation that overflow losses when high pressure appears and the median loss of unloading. Moreover, the accumulator can provide a certain pressure to suction port of pump during steering process, which also can decline the output energy of pump finally.Electric-hydraulic flow matching principle can adjust the flow of pump with the need of steering hydraulic cylinders, thus can decline the loss of oil flow. Therefore, this principle can provide a reference to the design of other hydraulic systems in which the load frequent changes. |
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