The positioning control of the hydraulic support pushing system in the fully mechanized mining face is the key technical support to realize intelligent mining. The opening and closing of the existing support switch reversing valve will cause a sudden change in the system pressure and flow under the conditions of high pressure and large flow, which will affect the life of the components, the precision, and stability of the actuator movement. To solve the problem, the structure of a two-speed buffer valve for the hydraulic support pushing circuit is designed. Firstly, the pushing system is analyzed theoretically, and the characteristics of the flow field in the valve and the applicable working conditions are simulated. Then, an experimental platform was built to test the improvement effect of the two-speed buffer valve on the characteristics of the pushing system. Finally, the pressure, flow, and positioning characteristics of the two-valve series pushing system under different flow rates are studied by the test results. The research results show that when the two-speed buffer valve is used, the pressure and velocity change thresholds of the system are reduced, which reduces the pressure fluctuation in front of the valve and its effect on the system pressure. At the same time, under a different system flow, the downstream pressure characteristics of the valve are improved, and the steady-state pressure anti-interference is enhanced. The positioning error of the system is reduced under different flow rates. The effectiveness of the scheme is verified by the test, which provides a basis for the optimization of the downhole valve control cylinder scheme and the subsequent valve.
Aim to solve the numerical forward solutions of 3RPUPc-UPS parallel mechanism, the particle-artificial bee colony algorithm is proposed. By analyzing the topological characteristics of the mechanism, the position and orientation characteristics sets, degrees of freedom and coupling degrees are obtained. According to the geometric characteristics of the mechanism, the inverse kinematics equations and the forward kinematics solutions model are established. Through a forward solution software of the mechanism, which is developed based on the particle swarm optimization, the artificial bee colony and the particle-artificial bee colony algorithm, the numerical solutions of the mechanism are obtained. The results show that the running time of the particle-artificial bee colony algorithm is shortened 47.46
针对全焊接球阀密封性欠佳的问题,以NPS16 Class600 型球阀为例,对其密封结构的密封性能进行了理论推导、仿真分析和试验验证,并基于响应面法对密封结构参数进行了多目标优化设计.首先,利用试验设计法(DOE)及响应面法(RSM)建立了密封结构的优化模型,对密封结构进行了静力学分析;然后,搭建了试验平台,进行了密封结构的开口度测试,并根据测试结果对仿真分析结果进行了验证;利用ANSYS软件对浮动球球阀密封结构进行了静力学分析,并研究了球体的直径(d1)、阀座的厚度(D7)、中径(D10)、倒角(DA)对其密封性能的影响;最后,根据响应面优化(RSO)模块对密封结构参数进行了多目标优化设计,进一步验证了其优化效果及密封性能.研究结果表明:D10对最小间隙值(Cmin)的影响显著性最高,d1 对最大等效应力(S1max)的影响显著性最高;在密封结构两参数耦合作用下,DA与D7 对最小间隙值(Cmin)的影响显著,DA与d1 对最大等效应力(S1max)的影响显著;优化设计后的密封结构最大变形量降低了57.2%,密封面的接触平均压力提高了7.8%,实现了对浮动球球阀密封结构进行高精密设计的目的.
变刚度柔性夹持装置既保留了软体驱动器的柔顺特性,又有效提高了夹持装置的夹持力.根据结构及驱动方式的不同,变刚度柔性夹持装置主要可分为包含内骨骼或外骨骼结构、基于干扰(阻塞)效应、内嵌低熔点合金或聚合物等3 个种类.包含内骨骼或外骨骼结构的夹持装置无法实现刚度的灵活调节;基于干扰效应的夹持装置的两种典型结构中,层干扰比颗粒干扰的刚度调节范围更大,但其结构更复杂,导致制造困难;而内嵌低熔点合金或聚合物的夹持装置,其最大缺陷为响应时间过长,且对设备和驱动器的绝缘以及耐热性能的要求较高.通过分析和总结目前变刚度夹持装置的研究现状,指出目前在该研究领域被忽视的关键问题主要包含3 个方面:1)缺少变刚度机理方面的深层次研究;2)缺少变刚度柔性夹持装置可靠性和寿命的研究;3)缺少变刚度柔性夹持装置的应用研究.
风力发电机主轴强度有限元分析存在复杂且耗时的问题.为了提高风力发电机中传递载荷的关键部件—主轴的设计效率,以单SRB和双TRB两类机型的主轴结构为例,分析了无网格法在主轴装配体上的计算可靠性,及其在建模过程与计算时间上的优势,进而提出了一种利用无网格法提高迭代效率的主轴结构设计方法.首先,以含双列调心滚子轴承(SRB)或单列圆锥滚子轴承(TRB)的两类主轴装配结构为对象,建立了采用杆单元简化轴承建模的有限元模型;然后,基于外部有限元逼近法,建立了适用于三维原型的边界条件与接触关系,开展了无网格法建模研究;最后,在4 种典型极限载荷工况下,计算了两类主轴无网格模型的变形与集中应力结果,并将其与业内公认的有限元强度分析方法的结果进行了对比,对主轴无网格法的适用性和有效性进行了验证.研究结果表明:与有限元强度分析方法相比,无网格法计算两类结构的最大位移相对误差在-6.06%～2.28%之间,主轴上的集中应力相对误差分别在-2.36%～2.94%及-6.71%～4.76%之间,两者结果较为吻合;由此可见,在保证刚度、应力准确的同时,无网格法的建模过程更加简便,且计算时间显著降低,可有效提高主轴的设计效率.
