No abstract

The working performance of the spindle system is the most important factor to embody the overall performance of the machine tool. To ensure the advanced capabilities, besides the high-precision manufacturing technologies, it is mainly depending on the bearing module and the forces on the spindle. In this paper, a new strategy of the vertical spindle supporting system is presented to meet the high stiffness requirement for the aerostatic bearing. Based on the computational fluid dynamics and finite volume method, a fluid dynamic model and structure model of the large diameter incorporate radial-thrust aerostatic bearing is developed and simulated to find out the pressure distribution laws of the spindle supporting system. The grid subdivision in the direction of film thickness is paid more attentions when establishing the grid of the whole gas film. Simulation results show that this special structure of bearing module can supply enough load capacity and stiffness for the machine tool. The results also indicate that the static characteristics of the bearing are improved as the supply pressure increases and as the supply orifice diameter decreases.

This paper presents a systematic structure and a control strategy for the electric vehicle charging station. The system uses a three-phase three-level neutral point clamped (NPC) rectifier to drive multiple three-phase three-level NPC converters to provide electric energy for electric vehicles. This topology can realize the single-phase AC mode, three-phase AC mode, and DC mode by adding some switches to meet different charging requirements. In the case of multiple electric vehicles charging simultaneously, a system optimization control algorithm is adopted to minimize DC-bus current fluctuation by analyzing and reconstructing the DC-bus current in various charging modes. This algorithm uses the genetic algorithm (ga) as the core of computing and reduces the number of change parameter variables within a limited range. The DC-bus current fluctuation is still minimal. The charging station system structure and the proposed system-level optimization control algorithm can improve the DC-side current stability through model calculation and simulation verification.

This paper provides the transfer matrix method to analysis the natural frequency of the vertical spindle using on ultra-precision fly cutting machine tool. Several transfer matrix equations of the typical units of the spindle had been established when considering the effects of the gyroscopic torque as the rotor has a large inertial tensor. And then the natural frequencies and each modal shape of the spindle rotor system were calculated using the transfer matrix model. Also, the modal experimental test had been taken out. The theoretical results from the transfer matrix model are very close to the test results, and the accuracy and the effective of the model was proved.

The components of spindle system are key components in ultra precision machine tool. According to the characteristics of the machining process of vertical hydrostatic spindle system for ultra-precision fly cutting machine, the mass- stiffness model of the spindle system is established. This paper describes a system for the analysis of the spindle system under the action of external shocks. The use of the state space method is discussed and an example is given. The influence law of vibration frequency is obtained for the various mass and stiffness value of the spindle system components.

Ultra-precision flying cutting machining with a vertical milling style is an important means of ultra-precision machining. It has a close relationship between the machining accuracy and the dynamic characteristics of the aerostatic spindle. The film force acting on the spindle rotor is related to the manufacture, installation and static unbalance or dynamic imbalance or other factors. Therefore, it is necessary to analyze the dynamic pressure force caused by these factors in order to study on the rotor posture and quantitative movement of the spindle. This article derived the solution formula for the dynamic pressure reaction force of the ultra-precision machine tool spindle with vertical static film based on the basic theory of the rigid body dynamics. The gyroscopic torque of the spindle has been analyzed under different conditions with the spindle dynamic balancing tests, which provide a reference to the further analysis of the spindle dynamic characteristics.

With silicon particles reinforced aluminum matrix composites with high volume fraction becoming a new hotspot on research and application in the aerospace materials and electronic packaging materials, the machinability of this material needs to be explored. This paper reports research results obtained from the surface grinding experiment of silicon particles reinforced aluminum matrix composites using black silicon carbide wheel, green silicon carbide wheel, white fused alumina wheel and chromium alumina wheel. The issues discussed are grinding force, surface roughness, the comparison of different grinding wheels, the micro-morphology of the work piece. The results showed that the grinding force was related with the grinding depth and the grinding wheel material, the grinding force was increasing as the grinding depth growing. The surface roughness was between 0.29μm and 0.48μm using the silicon carbide wheel. The surface of the work piece had concaves caused by silicon particles shedding and grooves caused by the grains observed by the SEM and CLSM.

Gas pressure regulator is an essential component using for the pressurized system in the aircraft. In our paper, we aim to analyze the impact of structural parameters on output pressure for the I-stage structure of a dual-stage gas pressure reducing regulator. Initially, a numerical simulation of the regulator was established and verified by a comparison of dynamic response from the deflation start of the vessel to the deflation complete. Moreover, parametric analysis of the I-stage structure for the regulator was examined to determine the primary and secondary variables and interdependencies with the Box-Behnken design method applied. Furthermore, a multi-objective optimization based on regression analysis was adopted by using the MOGA-II algorithm method, and a Pareto frontier was obtained. Results indicate that the spool mass, the leakage area of spool seal, and their interaction are the significant factors on overshoot. The overshoot presents a trend of decrease first and then increase with the mass and leakage area increase. The spool mass, the mainspring stiffness, the leakage area of spool seal, and their interactions are influential factors on stability. The stability improves with the spool mass decrease, and other factors increase. Besides, the feedback hole area has a small effect on stability. Moreover, the Pareto of the optimization indicates that the performance of the I-stage structure would be optimal when the spool mass is 23.94 g, the feedback hole area is 89.94 mm 2 , the mainspring stiffness is 166.76N/mm, and the leakage area of spool seal is 0.06 mm 2 .