| Hydraulic drill is widely used in the area of construction, earth exploration and gas drainage due to the advantage of compact structures, stable motion, easy operation and feasibility to change the velocity. However, the domestic hydraulic systems mainly use the traditional pump-valve control system, resulting in the oil temperature rising and severe energy loss. Therefore, the traditional way of valve adjustment is going to be replaced by an ideal energy saving hydraulic system. The most popular energy saving control system nowadays is load sensing hydraulic system. Therefore, it is necessary to study such system and analyze the factors that may affect the dynamic performance of the system, providing some foundation to the future design.Taking the ZDY6000L crawler drill as an example, focusing on the dynamic performance of the load sensing hydraulic system, this paper mainly deals with the theoretical modeling and digital simulation. The main work is summarized below.Firstly the paper deals with theoretical analysis and mathematical modeling of the crawler drill's hydraulic system. The hydraulic system is mainly composed of five full circuits. Combined with drills' different condition, the paper analyzes the operation structure, work condition and load characteristics. Based upon the load sensing work principle analysis, with the power bond method, the model of the rotation part of the hydraulic system is built and the system's power bond model under constant current and constant voltage is depicted. Mathematical model of the load sensing hydraulic system is obtained.Secondly the paper builds the model for key hydraulic component of load sensing and pressure control valve and set up the simple model of load sensing rotation circuit. After we understand the working principle of the hydraulic components, commercial software package AMESim is used to build the model of these two components. Simulation results agree well with the real situation. The paper employs the AMESim to build the drill's load sensing hydraulic rotation circuits model and do the simulation to obtain the system's working performance (the pressure difference of load sensing valve is 2MPa). The simulation results shows that: 1) the output of the system of waiting-for-work condition is low pressure and small amount of flow rate; 2) the output of the normal working condition is constant amount of flow rate and pressure changing with the load pressure, always higher than the load pressure by certain amount; 3) the output of the overload condition is also high pressure and small amount of flow rate. The simulation confirms the stability and energy saving characteristics of the drill's rotation circuits after the application of the load sensing hydraulic system.Thirdly the paper involves with the effect of load feedback pipe on dynamic performance of hydraulic system. Simulation is made on the model of rotation system in AMESim environment. The results indicate that while the pipe length is in the range of 0.5m to 10m, the longer the feedback pipe, the slower the response, the better the stability of the system; while the pipe length is longer than 10m, the system lost load sensing attributes, the response trend to slow and the stability is getting worse.Fourthly the paper shows the experiments study on ZDY6000L crawler drill. We mainly test the drill's rotation circuits' performance and energy utilization rate when we apply the load sensing hydraulic control system. The experiments show that the drill's performance, including stability and high rotation efficiency, is much better. Furthermore, the system's working efficiency is higher at high pressure work place than that of low pressure, especially at the high torque and low velocity working condition, even up to 50%.In conclusion, this paper mainly focuses on the crawler drill's load sensing hydraulic system, simulates the dynamic performance, and provides the fundamental information of designing the load sensing system and numerical simulation of dynamic performance of the load sensing hydraulic system.
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