The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone t...The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone to uncertainties such as model parameter variations and disturbances. Robust optimal tracking controller design for this kind of precision stages with mass and damping ratio uncertainties was researched. The mass and damping ratio uncertainties were modeled as the structured parametric uncertainty model. An identification method for obtaining the parametric uncertainties was developed by using unbiased least square technique. The instantaneous frequency bandwidth of the external disturbance signals was analyzed by using short time Fourier transform technique. A two loop tracking control strategy that combines the p-synthesis and the disturbance observer （DOB） techniques was proposed. The p-synthesis technique was used to design robust optimal controllers based on structured uncertainty models. By complementing the/z controller, the DOB was applied to further improving the disturbance rejection performance. To evaluate the positioning performance of the proposed control strategy, the comparative experiments were conducted on a prototype micro milling machine among four control schemes： the proposed two-loop tracking control, the single loop μ control, the PID control and the PID with DOB control. The disturbance rejection performances, the root mean square （RMS） tracking errors and the performance robustness of different control schemes were studied. The results reveal that the proposed control scheme has the best positioning performance. It reduces the maximal errors caused by disturbance forces such as friction force by 60% and the RMS errors by 63.4% compared with the PID control. Compared to PID with DOB control, it reduces the RMS errors by 29.6%.展开更多
文摘目的分析2014—2018年杭州市肺结核患者对一线抗结核药品的耐药特征及其影响因素,为杭州市防治耐药结核病提供科学依据。方法收集2014—2018年浙江省中西医结合医院结核病诊疗中心就诊的杭州市全部常住人口中的活动性肺结核患者,共12 851例,纳入结核分枝杆菌培养阳性且对一线抗结核药品药物敏感性试验(简称"药敏试验")信息全面的3807例患者。通过国家结核病信息管理系统和结核病实验室信息系统(laboratory information system,LIS)收集所有患者的性别、年龄、户籍、职业、治疗分类(初治和复治)、肺部有无空洞、患者来源及现居住地、结核分枝杆菌培养及药敏试验结果。运用单因素和多因素非条件logistic回归分析的方法研究杭州市耐药肺结核患者耐药特征及其影响因素。结果 3807株菌株中,907株(23.82%)对4种一线抗结核药品耐药,耐药顺位依次为异烟肼(18.57%,707例)、链霉素(18.41%,701例)、利福平(12.03%,458例)、乙胺丁醇(6.41%,244例);所有患者的耐多药率和多耐药率分别为11.11%(423/3807)和4.44%(169/3807)。2014—2018年不同年份肺结核患者耐药率分别为22.87%(185/809)、25.55%(198/775)、25.60%(181/707)、23.04%(188/816)、22.14%(155/700),差异无统计学意义(χ_(趋势)^(2)=4.275,P=0.370);耐多药率分别为11.12%(90/809)、13.16%(102/775)、11.88%(84/707)、11.40%(93/816)、7.71%(54/700),差异有统计学意义(χ_(趋势)^(2)=11.276,P=0.024)。多因素条件logistic回归分析显示,相对于男性和初治患者,女性和复治肺结核患者是发生耐药的危险因素[OR(95%CI)=1.308(1.111~1.540);OR(95%CI)=4.281(3.498~5.238)];相对于下沙区,居住在其他6个区的结核病患者发生耐药的可能性较大,萧山区和富阳区的风险更高[OR(95%CI)=4.400(2.559~7.565);OR(95%CI)=3.803(2.037~7.098)]。相对于男性、<40岁、初治患者,女性、≥40岁、复治的肺结核患者是产生耐多药的危险因素[OR(95%CI)=1.724(1.364~2.178);40~岁组:OR(95%CI)=3.418(1.599~7.305);60~岁组:OR(95%CI)=3.885(1.832~8.239);复治:OR(95%CI)=7.645(5.984~9.766)]。结论杭州市应该加强年龄≥40岁、复治、女性、居住在萧山地区、富阳区耐药结核病患者的管理和治疗,是降低杭州市耐药及耐多药结核病产生和传播的关键。
基金Project(50875257) supported by the National Natural Science Foundation of China
文摘The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone to uncertainties such as model parameter variations and disturbances. Robust optimal tracking controller design for this kind of precision stages with mass and damping ratio uncertainties was researched. The mass and damping ratio uncertainties were modeled as the structured parametric uncertainty model. An identification method for obtaining the parametric uncertainties was developed by using unbiased least square technique. The instantaneous frequency bandwidth of the external disturbance signals was analyzed by using short time Fourier transform technique. A two loop tracking control strategy that combines the p-synthesis and the disturbance observer （DOB） techniques was proposed. The p-synthesis technique was used to design robust optimal controllers based on structured uncertainty models. By complementing the/z controller, the DOB was applied to further improving the disturbance rejection performance. To evaluate the positioning performance of the proposed control strategy, the comparative experiments were conducted on a prototype micro milling machine among four control schemes： the proposed two-loop tracking control, the single loop μ control, the PID control and the PID with DOB control. The disturbance rejection performances, the root mean square （RMS） tracking errors and the performance robustness of different control schemes were studied. The results reveal that the proposed control scheme has the best positioning performance. It reduces the maximal errors caused by disturbance forces such as friction force by 60% and the RMS errors by 63.4% compared with the PID control. Compared to PID with DOB control, it reduces the RMS errors by 29.6%.
