The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angl...The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angle errors of BLGFU,in this paper,the contact stress and deformation mechanics between the ball and rail is analyzed. Based on Hertz theory of contact and theory of the multi-body system,a model of the contact stiffness considering the changes in contact angle is established. With the increasing of the external load,the varying trend of the contact deformation can be obtained. Therefore, the motion accuracy degradation of the BLGFU can be analyzed. By using a special experimental device and test system of the rolling linear guide worktable,the horizontal contact stiffness and the vertical linear stiffness are obtained,respectively. By comparing the contact stiffness of the experiment dates and the simulation results,the variation tendency of two curves is consisted and the difference between the measured values and the theoretical values is less than 18%. It is obvious that the model of the contact stiffness considering changes of contact angle has accuracy and feasibility. Thus,while external force point locating at different positions; the contact stiffness and the accuracy analysis of the BLGFU are proved validity by simulations.展开更多
目的:对重症监护室(ICU)病人肠内营养喂养不耐受预测模型进行范围综述,为临床研究提供参考。方法:根据Arksey等提出的范围综述报告框架,检索PubMed、Web of Science核心合集、Embase、中国知网、万方数据库、维普中文科技期刊数据库中IC...目的:对重症监护室(ICU)病人肠内营养喂养不耐受预测模型进行范围综述,为临床研究提供参考。方法:根据Arksey等提出的范围综述报告框架,检索PubMed、Web of Science核心合集、Embase、中国知网、万方数据库、维普中文科技期刊数据库中ICU病人肠内营养喂养不耐受预测模型的相关研究,检索时限为建库至2024年2月1日。由2名研究者独立筛选文献、提取资料,采用临床预测模型偏倚风险和适用性评估工具对纳入的模型进行质量评价。结果:最终纳入11篇文献,包括11种风险预测模型,模型的受试者工作特征曲线下面积(AUC)为0.700~0.906,偏倚评价结果显示纳入模型偏倚风险较高。结论:需要开发更具我国本土化特征的风险预测模型,尽量开展多中心、大样本的研究,应用多种验证法对模型进行验证,促进科学、有效、便捷的评估工具应用于临床。展开更多
【目的】针对超临界机组燃水比(firing rate to feed water ratio,FR/FW)控制过程中存在强耦合性、负荷量大和抗扰动能力弱等问题,根据自耦PID控制理论提出了自耦PI(auto-coupling PI,ACPI)新型控制方法。【方法】将多变量FR/FW系统等...【目的】针对超临界机组燃水比(firing rate to feed water ratio,FR/FW)控制过程中存在强耦合性、负荷量大和抗扰动能力弱等问题,根据自耦PID控制理论提出了自耦PI(auto-coupling PI,ACPI)新型控制方法。【方法】将多变量FR/FW系统等效为多个单变量闭合回路系统,并将FR/FW系统的耦合性、已知或未知内部动态、外界扰动等一切复杂因素定义为总扰动,进而将FR/FW控制系统等价映射为线性扰动系统,构建了在总扰动激励下的受控误差系统。在此基础上,对每个单变量系统设计了基于速度因子的自耦PI控制器,并在复频域理论分析了控制系统的鲁棒稳定性和抗扰动鲁棒性。【结果】与PI、自抗扰控制方法相比,ACPI控制方法具有响应速度快、无超调的动态品质与抗扰动能力强的稳态性能。【结论】研究成果对提升超临界机组FR/FW系统的控制精度与鲁棒性具有重要意义。展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51505012 and 51575014)the Natural Science Foundation of Beijing(Grant No.KZ201410005010)+2 种基金the Important National Science&Technology Specific Projects of China(Grant No.2012ZX04010021-001-004)the China Postdoctoral Science Foundation Funded Project(Grant No.2016M591033)the Beijing Postdoctoral Research Foundation(Grant No.2015ZZ-13)
文摘The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angle errors of BLGFU,in this paper,the contact stress and deformation mechanics between the ball and rail is analyzed. Based on Hertz theory of contact and theory of the multi-body system,a model of the contact stiffness considering the changes in contact angle is established. With the increasing of the external load,the varying trend of the contact deformation can be obtained. Therefore, the motion accuracy degradation of the BLGFU can be analyzed. By using a special experimental device and test system of the rolling linear guide worktable,the horizontal contact stiffness and the vertical linear stiffness are obtained,respectively. By comparing the contact stiffness of the experiment dates and the simulation results,the variation tendency of two curves is consisted and the difference between the measured values and the theoretical values is less than 18%. It is obvious that the model of the contact stiffness considering changes of contact angle has accuracy and feasibility. Thus,while external force point locating at different positions; the contact stiffness and the accuracy analysis of the BLGFU are proved validity by simulations.
文摘目的:对重症监护室(ICU)病人肠内营养喂养不耐受预测模型进行范围综述,为临床研究提供参考。方法:根据Arksey等提出的范围综述报告框架,检索PubMed、Web of Science核心合集、Embase、中国知网、万方数据库、维普中文科技期刊数据库中ICU病人肠内营养喂养不耐受预测模型的相关研究,检索时限为建库至2024年2月1日。由2名研究者独立筛选文献、提取资料,采用临床预测模型偏倚风险和适用性评估工具对纳入的模型进行质量评价。结果:最终纳入11篇文献,包括11种风险预测模型,模型的受试者工作特征曲线下面积(AUC)为0.700~0.906,偏倚评价结果显示纳入模型偏倚风险较高。结论:需要开发更具我国本土化特征的风险预测模型,尽量开展多中心、大样本的研究,应用多种验证法对模型进行验证,促进科学、有效、便捷的评估工具应用于临床。
文摘【目的】针对超临界机组燃水比(firing rate to feed water ratio,FR/FW)控制过程中存在强耦合性、负荷量大和抗扰动能力弱等问题,根据自耦PID控制理论提出了自耦PI(auto-coupling PI,ACPI)新型控制方法。【方法】将多变量FR/FW系统等效为多个单变量闭合回路系统,并将FR/FW系统的耦合性、已知或未知内部动态、外界扰动等一切复杂因素定义为总扰动,进而将FR/FW控制系统等价映射为线性扰动系统,构建了在总扰动激励下的受控误差系统。在此基础上,对每个单变量系统设计了基于速度因子的自耦PI控制器,并在复频域理论分析了控制系统的鲁棒稳定性和抗扰动鲁棒性。【结果】与PI、自抗扰控制方法相比,ACPI控制方法具有响应速度快、无超调的动态品质与抗扰动能力强的稳态性能。【结论】研究成果对提升超临界机组FR/FW系统的控制精度与鲁棒性具有重要意义。
