基于DSP的PMSM伺服控制系统设计

基于永磁同步电机(PMSM)的矢量控制原理,设计了一种以TMS320F812信号处理器为核心的PMSM伺服仿真控制方案,来实现PMSM的最佳控制。自行设计加工了PCB控制板,并将控制核心F2812DSP芯片、PS21767功率模块等元件集成焊接到控制板上,不仅系统的集成度增高,而且易于实现数字化控制。同时在CCS3.3的环境下采用SVPWM技术进行软件设计,实现永磁同步电机的控制,最后用Matlab验证了该伺服系统的正确性。结果表明:该系统在电机的位置、转速、转矩等控制方面有明显的优势,性能良好。     

基于数字控制ZVS移相全桥可调宽输出电力试验电源设计

现代电力试验电源越来越朝小型化、高频化、模块化方向发展,DC/DC模块作为电力试验电源的核心部分,其设计合理与否影响电源的整体性能.本文采用ZVS移相全桥为主电路拓扑,分析了一种数字控制的设计方案,有良好的应用前景.设计并调试了一台2.2kW,输出电压25～220V可调的实验样机.样机输出稳定、效率高,验证了设计方案的可行性.     

A Simple Way to Prepare C/SiC Spring

A new method to form helical C/SiC spring is proposed. Using paraffin mold as a sacrificial core, unidirectional carbon fiber bundles (infiltrated with resin) are wrapped around the mold to form helical spring, and after resin curing, the mold is removed, leaving a preform of C/SiC spring. Following densification is finished with precursor infiltration and pyrolysis (PIP) process. The spring constant of C/SiC spring reaches 7.88 N/mm and could be regulated by varying composite density and carbon fiber content. The spring properties could be improved by twisting the carbon fibers at 35–50 twist/m. The restoration ratio reaches 100%, but energy dissipation happens during unloading process. After oxidation in air at 1200°C for 10 min, the spring has an 82.4% spring constant remaining ratio.     

Floating pinch method for utility targeting in heat exchanger network (HEN)

Most of the established methods for utility targeting in a heat exchanger network (HEN) are mainly focusing on fixed stream conditions, where the flow rate, heat capacity, supply and target temperatures are fixed. However, in the process industries, the stream conditions (flow rates and temperatures) are not fixed. Therefore, the established HEN targeting methods cannot be directly applied to locate the hot and cold utility targets for HEN problem with varying flow rates and temperatures. To address this issue, a revised floating pinch method which uses binary variables to parameterise the stream locations on the composite curves, is presented in this work to identify the minimum utilities targets. The revised method simplify the earlier version of floating pinch method presented by Duran and Grossmann (1986) by avoiding the non-differentiability in the mathematical program. Two cases, one with fixed parameters while another with temperature-dependent properties and varying operating parameters are solved to illustrate the revised model.     

生物医用多孔钛的表面仿生处理研究进展

介绍了钛作为生物医用材料的研究现状.针对多孔钛的结构特点,综述了当前生物医用材料的各种表面活化方法,如溶胶-凝胶法、预钙化处理法、碱热处理法、酸碱两步法等,总结了当前多孔钛表面改性和骨诱导机理的研究现状.     

长城润滑油实施品牌战略的探讨

随着新经济时代的来临,中国润滑油市场的竞争日趋激烈。中国石化润滑油分公司结合自身的资源优势,打造强势品牌,进一步赢得高端市场,使企业在市场竞争中立于不败之地,成功实施品牌战略。本文在对品牌战略相关基本概念解析的基础上分析了企业实施品牌战略的重要性,并针对中国企业在实施品牌战略中存在的问题提出了相应的对策。     

A High‐Performance Self‐Regenerating Solar Evaporator for Continuous Water Desalination

Emerging solar desalination by interfacial evaporation shows great potential in response to global water scarcity because of its high solar‐to‐vapor efficiency, low environmental impact, and off‐grid capability. However, solute accumulation at the heating interface has severely impacted the performance and long‐term stability of current solar evaporation systems. Here, a self‐regenerating solar evaporator featuring excellent antifouling properties using a rationally designed artificial channel‐array in a natural wood substrate is reported. Upon solar evaporation, salt concentration gradients are formed between the millimeter‐sized drilled channels (with a low salt concentration) and the microsized natural wood channels (with a high salt concentration) due to their different hydraulic conductivities. The concentration gradients allow spontaneous interchannel salt exchange through the 1–2 µm pits, leading to the dilution of salt in the microsized wood channels. The drilled channels with high hydraulic conductivities thus function as salt‐rejection pathways, which can rapidly exchange the salt with the bulk solution, enabling the real‐time self‐regeneration of the evaporator. Compared to other salt‐rejection designs, the solar evaporator exhibits the highest efficiency (≈75%) in a highly concentrated salt solution (20 wt% NaCl) under 1 sun irradiation, as well as long‐term stability (over 100 h of continuous operation).