改进型Smith-专家PID算法在烘缸温度串级系统上的应用

针对少烘缸或单烘缸纸机的干燥过程具有滞后大、惯性大且非线性的缺点,提出专家PID结合Smith预估器的算法,设计了少烘缸纸机或单烘缸纸机的烘缸温度和蒸汽流量串级控制系统。主控制器是改进的专家PID控制器,利用基于专家经验的知识库在线调整PID参数;对主回路采用改进型Smith预估器,以克服纯滞后对系统稳定性的影响,也解决了Smith预估器对数学模型精确要求的问题。利用MATLAB进行仿真,结果表明:改进型Smith-专家PID算法具有良好的控制品质,具有超调小及响应速度快等动态特性。     

Robust weighted fusion Kalman predictors with uncertain noise variances

In this paper, the problem of designing weighted fusion robust time-varying Kalman predictors is considered for multisensor time-varying systems with uncertainties of noise variances. Using the minimax robust estimation principle and the unbiased linear minimum variance (ULMV) rule, based on the worst-case conservative system with the conservative upper bounds of noise variances, the local and five weighted fused robust time-varying Kalman predictors are designed, which include a robust weighted measurement fuser, three robust weighted state fusers, and a robust covariance intersection (CI) fuser. Their actual prediction error variances are guaranteed to have the corresponding minimal upper bounds for all admissible uncertainties of noise variances. Their robustness is proved based on the proposed Lyapunov equation approach. The concept of the robust accuracy is presented, and the robust accuracy relations are proved. The corresponding steady-state robust local and fused Kalman predictors are also presented, and the convergence in a realization between the time-varying and steady-state robust Kalman predictors is proved by the dynamic error system analysis (DESA) method and the dynamic variance error system analysis (DVESA) method. Simulation results show the effectiveness and correctness of the proposed results.     

牵引变流器直流母线电压脉动下的无拍频电流控制方法

交流供电方式下,单相整流器的工作特性导致牵引变流器的输入功率呈现脉动形式。为吸收该脉动分量,业界主流方法是在直流母线上并联LC无源滤波器,该方案大大降低了装置的功率密度。取代该滤波器的有效途径是通过实时计算对牵引逆变器的PWM脉冲宽度进行精确补偿,使得逆变器即便工作于剧烈脉动的母线电压下,也不会输出有害的拍频电压/电流。然而对于大功率低开关频率应用场合,传统的前馈补偿方案效果不佳。本文提出了一种母线电压重复预测器,使前馈补偿性能得到极大改善。该预测器利用母线电压脉动的重复性,精确预测下一个开关周期内母线电压的平均值,再应用面积等效算法计算下一拍所需的脉冲宽度。稳态实验结果表明,相比传统的前馈补偿方法,本方法将逆变器输出侧的拍频电流降低了6～7倍。负载突变时,只需通过控制手段确保整流器输出的母线电压跌落小于10%,则动态过程中的拍频电流亦不大。     

Smith预估器在主汽温控制中的应用

超临界及超超临界机组是被控特性复杂多变的对象,随着机组负荷的变化,机组的动态特性参数亦随之大幅度变化,主蒸汽温度的控制更是控制上的难点,采用Smith预估器对主汽温控制策略进行了优化,取得了理想的效果,对同类机组具有一定的参考意义,优化结果表明,根据机组的自身特性制定合适的汽温控制策略更有利于主汽温度的控制。     

Within- and across-breed genomic predictions and genomic relationships for Western Pyrenees dairy sheep breeds Latxa,Manech, and Basco-Béarnaise

Genotypes, phenotypes and pedigrees of 6 breeds of dairy sheep (including subdivisions of Latxa, Manech, and Basco-Béarnaise) from the Spain and France Western Pyrenees were used to estimate genetic relationships across breeds (together with genotypes from the Lacaune dairy sheep) and to verify by forward cross-validation single-breed or multiple-breed genetic evaluations. The number of rams genotyped fluctuated between 100 and 1,300 but generally represented the 10 last cohorts of progeny-tested rams within each breed. Genetic relationships were assessed by principal components analysis of the genomic relationship matrices and also by the conservation of linkage disequilibrium patterns at given physical distances in the genome. Genomic and pedigree-based evaluations used daughter yield performances of all rams, although some of them were not genotyped. A pseudo-single step method was used in this case for genomic predictions. Results showed a clear structure in blond and black breeds for Manech and Latxa, reflecting historical exchanges, and isolation of Basco-Béarnaise and Lacaune. Relatedness between any 2 breeds was, however, lower than expected. Single-breed genomic predictions had accuracies comparable with other breeds of dairy sheep or small breeds of dairy cattle. They were more accurate than pedigree predictions for 5 out of 6 breeds, with absolute increases in accuracy ranging from 0.05 to 0.30 points. They were significantly better, as assessed by bootstrapping of candidates, for 2 of the breeds. Predictions using multiple populations only marginally increased the accuracy for a couple of breeds. Pooling populations does not increase the accuracy of genomic evaluations in dairy sheep; however, single-breed genomic predictions are more accurate, even for small breeds, and make the consideration of genomic schemes in dairy sheep interesting.     

准确把握电力市场方向切实做好电力负荷预测

根据多年从事电力负荷预测的经历和感受,重点介绍在负荷预测中常用的几种预测方法,并对负荷特性分析预测方法作简单的阐述,同时就如何作好电力负荷预测工作提出建议.     

新型Smith预估控制器在大延迟系统中的应用

针对控制系统中出现的大延迟问题,推导出了调节器在积分形式下的控制率,从而提出积分调节器Smith预估控制方法.根据推导出的新型Smith预估控制算法可知:只要系统的放大倍数取足够大,控制器在很快时间内就消除误差,可有效地解决系统中的大延迟问题.采用Matlab中的Simulink对新型Smith预估控制系统进行了调节器...     

Piecewise DC prediction in HEVC

In this paper, we propose an improved DC prediction method for high-efficiency video coding (HEVC) intra coding. The technique involves the application of pixel-wise predictors rather than block-based predictor in the DC mode. In HEVC, the pixels of neighboring reconstructed blocks are used to support multiple directional spatial prediction modes and reduce spatial redundancy. For lossless coding, pixel-by-pixel differential pulse code modulation (DPCM) is applied to directional predictions. Consequently, residuals are reduced and coding efficiency is improved. Since DC prediction still employs block-based coding, pixel-wise DC prediction is needed for better coding efficiency. When compared to HEVC lossless intra coding, the proposed algorithm reduces the bit rate by 5.95%. Furthermore, with pixel-by-pixel DPCM, the average bit rate reduction is 10.64% when compared to HEVC lossless intra coding.     

Sequential monitoring of manufacturing processes: an application of grey forecasting models

This study used statistical control charts as an efficient tool for improving and monitoring the quality of manufacturing processes. Under the normality assumption, when a process variable is within control limits, the process is treated as being in-control. Sometimes, the process acts as an in-control process for short periods; however, once the data show that the production process is out-of-control, a lot of defective products will have already been produced, especially when the process exhibits an apparent normal trend behavior or if the change is only slight. In this paper, we explore the application of grey forecasting models for predicting and monitoring production processes. The performance of control charts based on grey predictors for detecting process changes is investigated. The average run length (ARL) is used to measure the effectiveness when a mean shift exists. When a mean shift occurs, the grey predictors are found to be superior to the sample mean, especially if the number of subgroups used to compute the grey predictors is small. The grey predictor is also found to be very sensitive to the number of subgroups. This revised version was published online in May 2005 with a correction to the author’s affiliation.     

The Linear Prediction Method of Fading Channel Estimation for the Rake Receiver with Impulsive Interference

Parameter estimation of the multipath and fading channel is investigated for the Rake combiner used in a CDMA system with coherent demodulation. A linear predictor is proposed to obtain a better estimation. Since the industrial interference environment is generally impulsive, a parallel LMS adaptive algorithm is proposed to reduce the impact of impulsive noise on predictor weights adjustment. Performance analysis and computer simulations are presented.