On oscillation reduction in feedback control for processes with an uncertain dead time and internal–external disturbances

This paper aims to find a practical solution to reduce oscillation on the Smith Predictor (SP) based design with the dead time (DT) uncertainty, making it less sensitive to DT change and more effective in disturbance rejection. First, a conditional feedback mechanism is introduced in SP to reduce the amount of oscillation caused by the model inaccuracies in the DT parameter. Then, to address the oscillation caused by the phase lag in traditional PI controller and uncertain dynamics, this conditional SP is combined with active disturbance rejection control (ADRC), assisted by the knowledge of process dynamics. A practical tuning method is provided for the practicing engineers. The proposed approach is validated in extensive simulation studies with different types of plants and in frequency domain analysis. The simulation results show significant improvements in performance robustness and transient response.     

独头工作面通风降温新方法及效果分析

在贯穿风流温度较低的矿井，可用通风的方法解决独头作业面的降温问题，并在分析常规局部通风存在诸多缺点的基础上，提出了用小型高压鼓风机与刚性轻质小断面PVC风筒配合的沐浴局部通风降温新方法，并对该方案的效果进行了分析和计算。结果表明，该 方案在理论上是可行的，并具有许多显著的优点。     

关于桩基承载力确定的反思与选型的简化计算

本文着重论述单桩承载力确定的正确途径。提出几种有代表性桩型的单桩承载力的建议值。并在上述认识的基础上提供一种桩型比较经济的简化计算方法。     

预应力混凝土空心板梁静载试验方案研究

通过对哈尔滨市二环路快速干道工程中立交桥及高架桥的板梁检测 ,比较了预应力混凝土空心板梁的三种不同的静载试验方案 ,并分别从理论和实际上对结果进行分析 ,讨论了实际工程中板梁检测的可行方案。     

Environmental Effects Of The Dead Sea-Red Sea Canal

A project to link the Dead Sea to the Red Sea via a canal is undergoing extensive study. This project will transform the physical and chemical characteristics of the Sea and therefore has significant environmental impacts. The predicted behaviour of the Dead Sea with a canal project was examined in this study, and the environmental impacts were then identified and classified into positive and negative. The main positive impact of the canal is the restoration of the Dead Sea into its 1930s level, and the improvement in life quality in the area. Negative impacts include the risk of groundwater contamination, the re-establishment of stratification condition, seasonal precipitation of chemicals, and the growth of micro-organisms in the Sea.     

Yield and Quality Characteristics of Rendered Chicken Oil for Biodiesel Production

Whole dead poultry birds obtained from commercial layer farms were assessed for fat in the whole carcass and then dry rendered in three different rendering regimens T₁, T₂ and T₃ (temperature = 120, 130 and 140 °C and shell pressure = 1, 2 and 3 kg/cm² respectively) and the effect on the yield and quality of the rendered chicken oil were studied. The overall fat percentage of the whole dead poultry carcass was 14.55 ± 0.17 % and the fat content of ‘greaves’ was 14.49 ± 0.38 %. In the dry batch rendering trials, the mean overall fat recovery was 24.46 ± 1.19, 26.78 ± 3.14 and 22.42 ± 2.32 % and the overall fat yield was 3.52 ± 1.72, 3.84 ± 0.44 and 3.22 ± 0.33 % of the carcass weight in T₁, T₂ and T₃ respectively. Solvent extraction of fat could recover 96.10 ± 0.14 % of fat from ‘greaves’ which was significantly higher than the mechanical centrifugation method. Among the quality characteristics of the rendered chicken oil (RCO), moisture content ranged from 0.61 % (T₂) to 1.09 % (T₁) and the mean specific gravity was 0.91 at 30 °C. The FFA values of RCO obtained from the T₃ rendering regimen were significantly (p < 0.05) higher than the FFA values of T₂ and T₁. The mean acid value, iodine number, peroxide value, saponification value and unsaponifiable matter present in RCO showed no significant difference. The fatty acid profile and calorific values were studied. The RCO was converted to biodiesel by transesterification and the physico-chemical properties of the biodiesel were studied and compared with the Indian biodiesel specification.     

Recursive parameter estimation of exhaust gas oxygen sensors with input-dependent time delay and linear parameters

Exhaust gas oxygen sensors are widely used for emission control in internal combustion engine systems. Due to their working principle and their positioning, these sensors are subject to input-dependent time delays and input-dependent linear parameters. Consequently, the corresponding time delays and linear parameters can vary fast, i.e. at the same rate as the respective input signals. This paper presents an extension of an existing gradient-based least-squares algorithm and its application to recursively estimate the input-dependent time delays and linear parameters of wide-range oxygen sensors in diesel engines. The extended algorithm is applied in a detailed simulation and experimental study involving real wide-range oxygen sensors that are affected by drift, aging, clogging and manipulation. The input-dependent time delay and linear parameter estimates obtained with the proposed recursive algorithm accurately reproduce the estimates obtained with a numerical offline optimization procedure.     

基于粒子滤波的WiFi行人航位推算融合室内定位

为提高室内定位的精度和稳定性,提出使用粒子滤波融合WiFi指纹定位和行人航位推算的室内定位算法。为减少复杂室内环境对WiFi指纹定位的影响,提出将支持向量机分类与回归相结合的两级WiFi指纹定位算法。在基于智能手持设备惯性传感器的行人航位推算中,为减少惯性传感器的误差以及人随意行走带来的影响,采用状态转换的方法识别行走周期并进行步数统计,提出根据实时加速度数据动态设置状态转换的参数,利用步长和垂直加速度之间的关系以及相邻步长之间的关系,应用卡尔曼滤波进行步长计算。仿真实验中,基于支持向量机的WiFi指纹定位的平均误差比最近邻居(NN)算法降低34.4%,比K最近邻居(KNN)算法降低27.7%。改进的行人航位推算的性能优于常用代表性计步软件和步长计算算法,而经过粒子滤波融合后估计的行走轨迹更加接近真实轨迹:直线行走平均误差为1.21 m,优于WiFi的3.18 m和航位推算的2.76 m;曲线行走平均误差为2.75 m,优于WiFi的3.77 m和航位推算的2.87 m。     

A new design method for PI–PD control of unstable processes with dead time

PID controllers are still widely practiced in the industrial systems. In the literature, many publications can be found considering PID controller design for unstable processes. However, owing to the structural limitations of PID controllers, generally, good closed loop performance cannot be achieved with a PID for controlling unstable processes and usually a step response with a high overshoot and oscillation is obtained. On the other hand, PI–PD controllers are proved to give very satisfactory closed loop performances for unstable processes. The paper presents a simple design method to tune parameters of a PI–PD controller for the control of the unstable processes with time delay. The proposed method is based on plotting the stability boundary locus, which is a locus dependent on the parameters of the controller and frequency, in the parameter plane. The method uses a new concept named centroid of the convex stability region. Simulation examples and an experimental application are given to illustrate the superiority of the proposed method over some existing ones.