Applied Mechanics and Materials Vols. 130-134

Abstract: The feed drive system model of NC precision sphere grinding machine (MD6040) is constructed. Although a large number of researchers pay more attention on advanced controllers, most high performance machine tools still adopt PID (Proportion Integration Differentiation) controller today. In this paper, PDF (Pseudo-Derivative Feedback) controller and PDFF (Pseudo-Derivative Control with feedforward Gain) controller which evolved from PID controller are studied. The performance of PID controller, PDF controller and PDFF controller is investigated by simulation and experiment. Both simulation results and experiment results showed that PID controller has severe overshoot and less rise time, PDF controller has strong robustness and long rise time and PDFF controller possesses the advantages of the other two controllers. PDFF controller is more suitable for NC precision sphere grinding machine feed drive system.

Abstract: In order to meet the needs of changing positions and orientations in large-scale product testing and large workpiece operating, such as machining, welding and spraying, this paper presents a planar decoupled parallel manipulator driven by three sliders. This simple but practical mechanism is capable of realizing a large workspace. The direct and inverse kinematical solutions are derived. The working spaces of the end operator are carried out when it is in given positions and given orientations. The simulation demonstrates that all kinds of straight lines and circles can be realized by the end operator of the mechanism, which the corresponding motion disciplines and characteristics of the three sliders are also obtained. Last, the virtual prototype of the manipulator is given. The paper lays the foundation for the manufacture, the real-time control and industrial application of the 3-DOF parallel manipulator.

Abstract: A new type of squeeze film damper (SFD) is designed to reduce spool’s impact and vibration which happen in the two-stage larger flow rate high-speed on/off valve with the 450 L/min flow rate and 8ms turn-off time, the valve’s sealing performance、reliability and service life improve largely, and the valve’s response speed doesn’t drop. The simulated and experimental results show: The damper has optimum buffering performance when oil film thickness is 0.1mm, and the spool closing process approach ideal state. The valve will has a great potential application in the powerful occasions because of it's perfect performance: larger flow rate、fast response and novel damper.

Abstract: This article dissertated the status of classification to desulfurization agent CaCO₃, designed a kind of new-type whirlpool grader, dissertated the principle and excellence of its impeller, at last we established its math model.

Abstract: The simulation models of the hydraulic motor-vane pump and three-phase asynchronous motor are established based on Maxwell 2D of ANSOFT, with which the basic performance and transient characteristic are analyzed and the influence law of the hydraulic oil on the transient starting performance of special motor is obtained. The simulation results can be used to design the special motor.

Abstract: In order to understand the vibration characteristics of gears based on trapped-oil in external spur-gear pump, from the calculations of trapped-oil pressure and hydraulic load and contact stiffness and trapped-oil stiffness, etc., a dynamic model coupled with trapped-oil pressure was derived for the gears, then an iterative operation based on Runge-Kutta method was used for analyzing the model, therefore the data related to trapped-oil pressure and the vibration displacement and the vibration velocity were obtained in a periodic of trapped oil, and the impact of different backlash value and different distance between two unloading grooves on trapped oil pressure and dynamic characteristics of gears was briefly analyzed. All results of simulation showed that trapped-oil pressure and trapped-oil stiffness had greater impact on vibration characteristics of gears in external spur-gear pump, trapped-oil stiffness could reduce the vibration of the gears; in simulation of trapped-oil pressure, dynamic trapped-oil model related to dynamic characteristics of gears more accurate than the static trapped-oil model irrelated to dynamic characteristics of gears; the trapped-oil pressures in two trapped-oil cavity were different, the vibration characteristics of gears was better that in larger backlash value, etc.. Finally, by the trapped-oil stiffness of the external gear pump is unique, the important conclusions are educed that the vibration of gears in external spur-gear pump is indeed different from conventional gears and so on.

Abstract: In order to improve the machining accuracy of spiral bevel gear, difference surface was adopted to characterize its global form deviations quantifiably and correct its deviations. The quantitative mathematical relationship between the actual tooth surface deviations of spiral bevel gear and the corrected values of the machine-setting parameters had been referred, and the theoretical correction formula of the global form deviations had been gotten by the least square method. Finally, the pinion of spiral bevel gear in the automobile rear axle has been set for an example to account for the effectiveness of the deviation correction by use of the difference surface method.

Abstract: The working principle and driven approach of a piezoelectric linear motor which uses axial stretching vibration of cascading piezoelectric elements is introduced. The prototype of that motor is designed and fabricated. It’s performance is also tested. The motor’s vibrator is a stick and moving object is a cylindrical ring which contacts with vibrating stick in the shape of cylindrical surface. The forward and backward movements of moving object are achieved by utilizing the axial stretching vibration of vibrating stick. The moving direction is altered by changed the frequency of driving signal. The structure of the motor is simple and the power supply is single sine phase. So that it is easy to be smaller. In addition, the thrust force is increased by cylindrical surface contact between moving object and vibrating stick so that it is easy to be practical also. This kind of piezoelectric linear motor is very suitable for precise positioning of objects, fine material handling, and vibration cutting tools.

Abstract: This paper designs a dual topological structure of grid-connected inverter for high-power wind turbine, and introduces PWM converter's operational state. It establishes mathematical model of grid-side converter for wind turbine, then it puts forward the dual closed-loop vector control strategy of grid-side converter based on dq coordinate. The combination of the dual topological structure and decoupling control realize the functioning of high-power factor and two-way transmission of energy. Grid-side converter can stabilize DC side voltage during rapidly changed wind velocity which led to changes of output power in generator. Active or reactive output current can be adjusted independently. The hardware experiments and simulation results verify the feasibility of the proposed control scheme in both the high stability accuracy and excellent property of grid-connected.

Abstract: As the global energy and environmental situation is serious, the wind energy as a clean, renewable energy，is got more and more world attention. Wind power technology is becoming the research focus of many countries. Hydraulic system with its high reliability and fast response characters is widely used in the rotor brake system, yaw brake system, pitch system.