A fault tolerant control （FTC） design technique against actuator stuck faults is investigated using integral-type sliding mode control （ISMC） with application to spacecraft attitude maneuvering control system. The...A fault tolerant control （FTC） design technique against actuator stuck faults is investigated using integral-type sliding mode control （ISMC） with application to spacecraft attitude maneuvering control system. The principle of the proposed FTC scheme is to design an integral-type sliding mode attitude controller using on-line parameter adaptive updating law to compensate for the effects of stuck actuators. This adaptive law also provides both the estimates of the system parameters and external disturbances such that a prior knowledge of the spacecraft inertia or boundedness of disturbances is not required. Moreover, by including the integral feedback term, the designed controller can not only tolerate actuator stuck faults, but also compensate the disturbances with constant components. For the synthesis of controller, the fault time, patterns and values are unknown in advance, as motivated from a practical spacecraft control application. Complete stability and performance analysis are presented and illustrative simulation results of application to a spacecraft show that high precise attitude control with zero steady-error is successfully achieved using various scenarios of stuck failures in actuators.展开更多
In an effort to develop methods of solving the issue of cuttings bed in horizontal wells, a 3-D transient model is establi- shed to simulate the distribution features and the transport mechanism of cuttings bed. The C...In an effort to develop methods of solving the issue of cuttings bed in horizontal wells, a 3-D transient model is establi- shed to simulate the distribution features and the transport mechanism of cuttings bed. The CFD calculation results show that the cut- tings at the cross-sectional area of the mutation location such as the drilling pipe connector would easily settle down to build up a cuttings bed and the transport performance of the cuttings in a horizontal well can only be improved to some extent by adjusting the working parameters without using any destruction tools for the cuttings bed, thus the issue of a cuttings bed can not be solved in general. Accordingly, a new approach to effectively prevent and actively destroy the cuttings bed by using the Cuttings Bed Impeller （CBI） is proposed, the sensitivity analysis of which is conducted to determine the optimal structural parameters and the best matched working parameters from a perspective of the wellbore cleaning. Results show that the use of the CBI produces a number of benefits, including the reduced drill string torque to avoid the stuck pipe incidents with corresponding improvement in hole quality, a shorter trip time, and less wear on the drill string, the top drive and the casing. This research offers theoretical guidelines for the design of destruction tools for the cuttings bed and for the wellbore cleaning control in the horizontal drilling.展开更多
Objective To discuss the role of stuck needle therapy on cervical spondylotic radiculopathy. Method Fifty patients with cervical spondylot-ic radiculopathy were selected to accepted stuck needle therapy. Comprehensive...Objective To discuss the role of stuck needle therapy on cervical spondylotic radiculopathy. Method Fifty patients with cervical spondylot-ic radiculopathy were selected to accepted stuck needle therapy. Comprehensive curative effects were determined by Northwick Park Questionnaire （NPO） according to Criteria of Diagnosis and Therapeutic Effect of Diseases and Syndromes in Traditional Chinese Medicine. Results Eighteen cases with NPQ effect size ≥90% account for 36%; 27 cases with 90%〉NPO. effect size≥60% account for 54%; 3 cases with 60%〉NPQ effect size≥30% account for 6%; 2 cases with no improvement in symptom and body activity account for 4%. The total effective rate was up to 96%. Conclusion Stuck needle therapy on cervical spondylotic radiculopathy has significant curative effects.展开更多
The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanis...The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanism of cuttings transport needs to be carefully investigated. In this research, a transient cuttings transport with multiple flow patterns model is developed to predict the evolution of cuttings transported in the annulus while backreaming. The established model can provide predictions of the distribution of cuttings bed along the wellbore considering the bulldozer effect caused by large-size drilling tools(LSDTs). The sensitivity analyses of the size of LSDTs, and backreaming operating parameters are conducted in Section 4. And a new theory is proposed to explain the mechanism of cuttings transport in the backreaming operation, in which both the bit and LSDTs have the “cleaning effect” and “plugging effect”.The results demonstrate that the cuttings bed in annuli is in a state of dynamic equilibrium, but the overall trend and the distribution pattern are obvious. First, larger diameters and longer drilling tools could lead to a higher risk of the stuck pipe. Second, we find that it is not the case that the higher flow rate is always better for hole cleaning, so three flow-rate intervals are discussed separately under the given conditions. When the “dangerous flow rate”(<33 L/s in Case 4) is employed, the cuttings bed completely blocks the borehole near the step surface and causes a stuck pipe directly. If the flow rate increases to the “low flow rate” interval(33-35 L/s in Case 4), a smaller flow rate instead facilitates borehole cleaning. If the flow rate is large enough to be in the “high flow rate” interval(>35 L/s in Case 4),the higher the flow rate, the better the cleaning effect of cuttings beds. Third, an interval of tripping velocity called “dangerous velocity” is proposed, in which the cuttings bed accumulation near the LSDTs is more serious than those of other tripping展开更多
基金National Natural Science Foundation of China(61004072)Fundamental Research Funds for the Central Universities(HIT.NSRIF.2009003)+1 种基金Research Fund for the Doctoral Program of Higher Education of China (20070213061, 20102302110031)Scientific Research Foundation for the Returned Overseas Chinese Scholars of Harbin (2010RFLXG001)
文摘A fault tolerant control （FTC） design technique against actuator stuck faults is investigated using integral-type sliding mode control （ISMC） with application to spacecraft attitude maneuvering control system. The principle of the proposed FTC scheme is to design an integral-type sliding mode attitude controller using on-line parameter adaptive updating law to compensate for the effects of stuck actuators. This adaptive law also provides both the estimates of the system parameters and external disturbances such that a prior knowledge of the spacecraft inertia or boundedness of disturbances is not required. Moreover, by including the integral feedback term, the designed controller can not only tolerate actuator stuck faults, but also compensate the disturbances with constant components. For the synthesis of controller, the fault time, patterns and values are unknown in advance, as motivated from a practical spacecraft control application. Complete stability and performance analysis are presented and illustrative simulation results of application to a spacecraft show that high precise attitude control with zero steady-error is successfully achieved using various scenarios of stuck failures in actuators.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51222406, 51004082)the New Century Excellent Talents in University of China (Grant No.NCET-12-1061)the Scientific Research Innovation Team Project of Sichuan colleges and universities (Grant No.12TD007)
文摘In an effort to develop methods of solving the issue of cuttings bed in horizontal wells, a 3-D transient model is establi- shed to simulate the distribution features and the transport mechanism of cuttings bed. The CFD calculation results show that the cut- tings at the cross-sectional area of the mutation location such as the drilling pipe connector would easily settle down to build up a cuttings bed and the transport performance of the cuttings in a horizontal well can only be improved to some extent by adjusting the working parameters without using any destruction tools for the cuttings bed, thus the issue of a cuttings bed can not be solved in general. Accordingly, a new approach to effectively prevent and actively destroy the cuttings bed by using the Cuttings Bed Impeller （CBI） is proposed, the sensitivity analysis of which is conducted to determine the optimal structural parameters and the best matched working parameters from a perspective of the wellbore cleaning. Results show that the use of the CBI produces a number of benefits, including the reduced drill string torque to avoid the stuck pipe incidents with corresponding improvement in hole quality, a shorter trip time, and less wear on the drill string, the top drive and the casing. This research offers theoretical guidelines for the design of destruction tools for the cuttings bed and for the wellbore cleaning control in the horizontal drilling.
文摘Objective To discuss the role of stuck needle therapy on cervical spondylotic radiculopathy. Method Fifty patients with cervical spondylot-ic radiculopathy were selected to accepted stuck needle therapy. Comprehensive curative effects were determined by Northwick Park Questionnaire （NPO） according to Criteria of Diagnosis and Therapeutic Effect of Diseases and Syndromes in Traditional Chinese Medicine. Results Eighteen cases with NPQ effect size ≥90% account for 36%; 27 cases with 90%〉NPO. effect size≥60% account for 54%; 3 cases with 60%〉NPQ effect size≥30% account for 6%; 2 cases with no improvement in symptom and body activity account for 4%. The total effective rate was up to 96%. Conclusion Stuck needle therapy on cervical spondylotic radiculopathy has significant curative effects.
基金the National Natural Science Foundation of China,China(Grant No.52227804,52174010)Strategic Cooperation Technology Projects of CNPC and CUPB,China(Grant No.ZLZX2020-01)+1 种基金Sinopec key laboratory of drilling completion and fracturing of shale oil and gas,China(Grant No.35800000-22-ZC0699-0004)the Key Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region,China(Grant No.XJEDU20211028)。
文摘The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanism of cuttings transport needs to be carefully investigated. In this research, a transient cuttings transport with multiple flow patterns model is developed to predict the evolution of cuttings transported in the annulus while backreaming. The established model can provide predictions of the distribution of cuttings bed along the wellbore considering the bulldozer effect caused by large-size drilling tools(LSDTs). The sensitivity analyses of the size of LSDTs, and backreaming operating parameters are conducted in Section 4. And a new theory is proposed to explain the mechanism of cuttings transport in the backreaming operation, in which both the bit and LSDTs have the “cleaning effect” and “plugging effect”.The results demonstrate that the cuttings bed in annuli is in a state of dynamic equilibrium, but the overall trend and the distribution pattern are obvious. First, larger diameters and longer drilling tools could lead to a higher risk of the stuck pipe. Second, we find that it is not the case that the higher flow rate is always better for hole cleaning, so three flow-rate intervals are discussed separately under the given conditions. When the “dangerous flow rate”(<33 L/s in Case 4) is employed, the cuttings bed completely blocks the borehole near the step surface and causes a stuck pipe directly. If the flow rate increases to the “low flow rate” interval(33-35 L/s in Case 4), a smaller flow rate instead facilitates borehole cleaning. If the flow rate is large enough to be in the “high flow rate” interval(>35 L/s in Case 4),the higher the flow rate, the better the cleaning effect of cuttings beds. Third, an interval of tripping velocity called “dangerous velocity” is proposed, in which the cuttings bed accumulation near the LSDTs is more serious than those of other tripping
