The piezoelectric actuator has been widely used in precision instruments and precision control. However, hysteresis, nonlinearity and creep exist in the actuator, which limit actuator applications and affect accuracy....The piezoelectric actuator has been widely used in precision instruments and precision control. However, hysteresis, nonlinearity and creep exist in the actuator, which limit actuator applications and affect accuracy. This thesis introduces fuzzy control as the algorithm of a closed-loop control system to control the piezoelectric actuator. Fuzzy control can make this closed-looped system not only have high linearity, repeatability, accuracy and few overshoot, but isalso easily used.展开更多
For the primary mirror of a large-scale telescope, an electro-hydraulic position control system(EHPCS) is used in the primary mirror support system. The EHPCS helps the telescope improve imaging quality and requires a...For the primary mirror of a large-scale telescope, an electro-hydraulic position control system(EHPCS) is used in the primary mirror support system. The EHPCS helps the telescope improve imaging quality and requires a micron-level position control capability with a high convergence rate, high tracking accuracy, and stability over a wide mirror cell rotation region. In addition, the EHPCS parameters vary across different working conditions, thus rendering the system nonlinear. In this paper, we propose a robust closed-loop design for the position control system in a primary hydraulic support system. The control system is synthesized based on quantitative feedback theory. The parameter bounds are defined by system modeling and identified using the frequency response method. The proposed controller design achieves robust stability and a reference tracking performance by loop shaping in the frequency domain. Experiment results are included from the test rig for the primary mirror support system, showing the effectiveness of the proposed control design.展开更多
文摘The piezoelectric actuator has been widely used in precision instruments and precision control. However, hysteresis, nonlinearity and creep exist in the actuator, which limit actuator applications and affect accuracy. This thesis introduces fuzzy control as the algorithm of a closed-loop control system to control the piezoelectric actuator. Fuzzy control can make this closed-looped system not only have high linearity, repeatability, accuracy and few overshoot, but isalso easily used.
基金supported by the National Basic Research Program(973)of China(No.2013CB035400)the National High-Tech R&D Program(863)of China(No.2012AA041803)the National Natural Science Foundation of China(No.51221004)
文摘For the primary mirror of a large-scale telescope, an electro-hydraulic position control system(EHPCS) is used in the primary mirror support system. The EHPCS helps the telescope improve imaging quality and requires a micron-level position control capability with a high convergence rate, high tracking accuracy, and stability over a wide mirror cell rotation region. In addition, the EHPCS parameters vary across different working conditions, thus rendering the system nonlinear. In this paper, we propose a robust closed-loop design for the position control system in a primary hydraulic support system. The control system is synthesized based on quantitative feedback theory. The parameter bounds are defined by system modeling and identified using the frequency response method. The proposed controller design achieves robust stability and a reference tracking performance by loop shaping in the frequency domain. Experiment results are included from the test rig for the primary mirror support system, showing the effectiveness of the proposed control design.
文摘目的:探讨急性肺损伤(ALI)早期应用控制性高浓度氧疗、持续气道内正压(CPAP)和双水平气道内正压(BiPAP)不同通气策略对气体交换和血管外肺水的影响。方法:24只杂种犬在制作油酸ALI模型成功后(PaO2/FiO2≤300 mmHg),保持自主呼吸,随机分为:(1)控制性高浓度氧疗组(n=8);(2)CPAP组(n=8);(3)Bi-PAP组(n=8)。连续记录并计算正常、ALI早期(阳性对照)和干预后1～4 h内各项气体交换和血流动力学指标。结果:在氧合指数(PaO2/FiO2)的改善上,干预后4 h BiPAP组效果最明显(375.83±81.55,P<0.01),其次是CPAP组(327.17±78.82,P<0.01),氧疗组改善不显著(255.00±49.85,P>0.05)。在肺泡死腔与潮气容积之比值[VD(alv)/VT]上,氧疗组进一步增大(P<0.01),CPAP组和BiPAP组显著降低(P<0.01)。3种通气策略均可提高氧输送量(DO2),BiPAP组效果最明显(P<0.01),其次是CPAP组和氧疗组。氧疗组的氧耗量(VO2)显著增高,氧摄取率(O2ER)明显高于CPAP组和BiPAP组(P<0.05,P<0.01)。干预后3组肺泡气-动脉血氧分压差[P(A-a)O2]较正常基础值和ALI早期均显著增高(P<0.01),3组间两两比较无显著差异(P>0.05)。在肺内分流比例(Qs/Qt)上,BiPAP组改善最明显(P<0.01),其次是CPAP组(P<0.01),氧疗组效果不显著。3组实验动物的肺动脉楔压(PAWP)和心排指数(CI)保持相对稳定。在平均肺动脉压(MPAP)和肺循环阻力指数(PVRI)上CPAP组和BiPAP组均进一步增高(P<0.05,P<0.01)。3组对血管外肺水指数(ELWI)的改善无显著作用(P>0.05)。结论:在ALI早期,BiPAP和CPAP对于改善气体交换和组织氧合具有积极作用,其中BiPAP效果更为显著。3种通气策略对血管外肺水的改善无显著作用。
