张力控制与负荷分配控制在纸机施胶部的应用

介绍了ABB公司所特有的直接转矩控制(DTC)变频技术、张力控制与负荷分配控制技术在纸机施胶部控制传动点上的实际运用情况.     

涂布白纸板机网部负荷分配智能化设计及实现

介绍了负荷分配原理,针对3400mm白纸板机的网部负荷分配作了智能化的设计,并给出了实现方法.     

无水胶印输墨系统油墨温度控制方法

油墨温度控制系统是无水胶印设备的重要控制组件之一,对保持油墨黏度稳定和印刷质量的一致性有重要影响。通过建立温控墨辊表面墨层热载荷时变函数模型,计算墨辊表面油墨平均温度发生变化时的热载荷变化量,根据对温控墨辊螺旋管道的传热性能参数进行等效,在采用涡流管作为温度双向控制伺服装置的前提下,确定了温控气体在设定出入温度差的条件下的输入流量,将温控气体的输入参数,包括流量值、入口温度值作为涡流管伺服控制器的输入参数,建立油墨温度PID整定控制模型,并基于Lab VIEW设计了控制系统。仿真结果表明控制模型合理,无水胶印油墨温控系统控制精度达到±1℃。     

Use of novel sensors combining local positioning and acceleration to measure feeding behavior differences associated with lameness in dairy cattle

Time constraints for dairy farmers are an important factor contributing to the under-detection of lameness, resulting in delayed or missed treatment of lame cows within many commercial dairy herds. Hence, a need exists for flexible and affordable cow-based sensor systems capable of monitoring behaviors such as time spent feeding, which may be affected by the onset of lameness. In this study a novel neck-mounted mobile sensor system that combines local positioning and activity (acceleration) was tested and validated on a commercial UK dairy farm. Position and activity data were collected over 5 consecutive days for 19 high-yield dairy cows (10 lame, 9 nonlame) that formed a subset of a larger (120 cow) management group housed in a freestall barn. A decision tree algorithm that included sensor-recorded position and accelerometer data was developed to classify a cow as doing 1 of 3 categories of behavior: (1) feeding, (2) not feeding, and (3) out of pen for milking. For each classified behavior the mean number of bouts, the mean bout duration, and the mean total duration across all bouts was determined on a daily basis, and also separately for the time periods in between milking (morning = 0630–1300 h; afternoon = 1430–2100 h; night = 2230–0500 h). A comparative analysis of the classified cow behaviors was undertaken using a Welch t-test with Benjamini-Hochberg post-hoc correction under the null hypothesis of no differences in the number or duration of behavioral bouts between the 2 test groups of lame and nonlame cows. Analysis showed that mean total daily feeding duration was significantly lower for lame cows compared with non-lame cows. Behavior was also affected by time of day with significantly lower mean total duration of feeding and higher total duration of nonfeeding in the afternoons for lame cows compared with nonlame cows. The results demonstrate how sensors that measure both position and acceleration are capable of detecting differences in feeding behavior that may be associated with lameness. Such behavioral differences could be used in the development of predictive algorithms for the prompt detection of lameness as part of a commercially viable automated behavioral monitoring system.     

糖厂自备电厂频率保护策略研究与实践

以糖厂发配电系统的实际配置为基础,对现有采样算法进行对比分析,选取适用的电压、电流、频率等参数的采样算法;对比研究了国内外相关孤岛检测技术,基于单机-无穷大运行模型,研究了自备热电厂发电机组的负荷极限;确定了外部主网故障防自备电厂孤岛效应的解列条件以及继电保护逻辑;对自备电厂用电负荷进行分级,据此确定低频减载判据,最后...     

Dimensionless stiffness per unit width of a rectangular slider bearing

The general shape of the curve S versus ? is discussed for a non-tilting rectangular slider bearing of arbitrary shape, where S is the bearing's dimensionless stiffness per unit width and ? the ratio of inlet height to outlet height. The maximum in the S-? curve is to the left of the maximum in the W-? curve, where W is the dimensionless load per unit width. Also, S(r) = 2W(r) where r is the value of ? at which W is a maximum. S-? curves have been plotted for a plane slider bearing of length l and width b. The range of ? is 1.25 to 4.00 and the values of b/l are 0.20(0.20)1.00, 1.25, 1.67, 2.50, 5.00 and ∞.     

广义Brownian Sheet的鞅刻画

在文献［１］的基础上给出了广义ＢｒｏｗｎｉａｎＳｈｅｅｔ鞅刻画：两参数连续适应过程（Ｂ２）ｚ∈Ｒ２＋为广义ＢｒｏｗｎｉａｎＳｈｅｅｔ的充要条件是（Ｂ２）ｚ∈Ｒ２＋为Ｆｏｕｑｕｅ意义下的两参数局部鞅，且存在Ｒ２＋上的Ｌ—Ｓ测度ｄ，（ｄ《λ，λ为Ｒ２＋上的Ｌｅｂｅｓｇｕｅ测度）使得（Ｂ２ｚ－ｄ（Ｚ）ｚ∈Ｒ２＋为Ｆｏｕｑｕｅ意义下的两参数局部鞅，其中以ｄ（ｚ）＝ｄ（（０，ｚ］）。     

箱式变电站箱内温升及变压器的负载率

箱式组合变电站箱内温的特点跟负载特性及箱壳的散热结构有关，而变电站内的电力变压器的负载率又跟箱内温升及箱壳的散热等级有关，本文给出了变压器负载率的计算公式和参考值。     

保护用电流互感器10%误差的校核方法

对于已经投入运行的电流互感器,测量其10%误差曲线较为困难,现场通常进行其伏安特性及二次负载试验并以此来进行电流互感器10%误差校核。并根据现场收集的典型电流互感器参数等数据进行实例计算,阐明电流互感器特性是否满足要求。并提出了在不满足10%误差要求时,应如何采取措施。     

基于AB变频器的造纸机电气控制系统的设计

文章就应用AB PowerFlex40变频器的造纸机电气传动控制系统中的负荷分配、速度链、系统网络组态及通讯等内容进行了较为详细的描述.这种基于S7-300PLC的三级控制的全数字控制系统适用高速纸机的高速度、高可靠性控制性能的需要.