This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionl...This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionless form. Further, a decoupled PD controller is proposed, and the local stability of the controller is analyzed by linearization technique. Parametric studies of the dynamics and de-spin control of a massive target are conducted to characterize the dynamic process of de-spin with the proposed control law. It is shown that the massive target can be de-span by a single and small space tug with limited thrust within finite time. The thrust tangent with the tether de-spins the target while the thrust normal to the tether prevents the tether from winding up the target. The tether length has a positive contribution to the de-spin of a target. The longer tether leads to a faster de-spin process.展开更多
This paper proposes a fuel-optimal deorbit scheme for space debris deorbit using tethered space tug.The scheme contains three stages named respectively as dragging,maintenance and swinging.In the first stage,the tug,p...This paper proposes a fuel-optimal deorbit scheme for space debris deorbit using tethered space tug.The scheme contains three stages named respectively as dragging,maintenance and swinging.In the first stage,the tug,propelled by continuous thrust,tows deorbit to a transfer orbit with a tether.Then in the second stage,the combination of the tug and the debris flies unpowered and uncontrolled to a swing point on the transfer orbit.Finally,in the third stage,the tug is propelled at the swing point and the rotation speed of the tethered system increases such that the debris obtains enough velocity increment.The trajectory optimization of the first stage is established considering the total fuel consumption of the three stages,whereas the dynamic model is simplified for computation efficiency.The solution to the optimal problem is obtained using a direct method based on Gauss pesudospectral discretization.Then a model predictive controller is designed to track the open-loop optimal reference trajectories,reducing the states’deviations caused by model simplification and ignorance of perturbations.Furthermore,it is proved that the fuel-optimal swing point is the apogee of the transfer orbit.The paper analyzes the fuel consumption of a typical scenario and demonstrates effectiveness of the proposed deorbit scheme numerically.展开更多
Objective: This study aimed to identify correlations of laboratory test results and knee joint function between pre- and post-operation of knee joint replacement surgery. Methods: The study covered 60 - 75 aged 50 pat...Objective: This study aimed to identify correlations of laboratory test results and knee joint function between pre- and post-operation of knee joint replacement surgery. Methods: The study covered 60 - 75 aged 50 patients who had operated with knee replacement surgery. 25 patients were male and another 25 patients were female. We compared laboratory test results of pre- and 3rd, 7th and 14th day of post-operation. Moreover, pre-operation knee joint function was compared with 3rd, 7th, 14th and 30th day of post-operation. Furthermore, we investigated the relationship among WBC, hemoglobin and function tests. Pre- and post-operative knee joint function tests were conducted by WOMAC (The Western On-tario and McMaster Universities Osteoarthritis), VAS (Visual Analogue Scale), TUG (Time up and Go) score, and MMT (Muscle Manual Test). Results: In pre-operation, patients’ average WBC was 6.447 ± 2.115 cells/μL, monocyte was 6.554 ± 3.101 cells/μL, lymphocyte was 31.177 ± 9.512 cells/μL and C-reactive protein was 0.6205 ± 0.922 mg/dL. In 3rd day of post-operation, WBC was 8.901 ± 2.869 cells/μL, monocyte was 4.881 ± 2.332 cells/μL, lymphocyte was 17.048 ± 9.702 cells/μL and C-reactive protein was 4.2762 ± 2.293 mg/dL. There was a statistically significant difference reported on pre- and post-operation pain, stiffness and daily activity (P rd day of post-operation were raised up and they were statistically significant (P rd, 7th, 14th day of TUG score was significantly correlated (P Conclusion: Results of WBC, hemoglobin, hematocrit, total protein, total bilirubin, and creatinine had increased in 3rd and 7th day of post-operation and had stabilized from 14th day of post-operation. Stiffness and TUG performance were controversially correlated in 3rd, 7th, 14th, 30th day of post-operation. However, in 7th and 14th of post-operation, patients’ muscle strength and knee joint amplitude had become stabilized and improved from 30th day of post-operation. Moreover, after the operation, the number of WBC controv展开更多
The log float technology from timber depot at the reservoir to log feeding rolls was studied by model tests. The model test was taken with the rule of gravitation similitude and ratio of 1∶10. Main parameters, like t...The log float technology from timber depot at the reservoir to log feeding rolls was studied by model tests. The model test was taken with the rule of gravitation similitude and ratio of 1∶10. Main parameters, like the amount of tug boats, hydro-accelerators and the structure of feeding rolls, were determined. The more suitable float process is put forward and the reliable basis for the design is supplied.展开更多
基于缅甸马德岛港三十万吨级原油接卸码头的自然情况,分析船舶引航相关要素信息。以码头设计船型"XIN HAN YANG"轮为例,详细分析该类型船舶满载时靠泊此处码头的安全操纵方法和注意事项,为实现"一带一路"在缅先导...基于缅甸马德岛港三十万吨级原油接卸码头的自然情况,分析船舶引航相关要素信息。以码头设计船型"XIN HAN YANG"轮为例,详细分析该类型船舶满载时靠泊此处码头的安全操纵方法和注意事项,为实现"一带一路"在缅先导示范项目--中缅原油输送管道的连续畅通奠定基础。展开更多
基金supported by the Discovery Grant(No.RGPIN-2018-05991)of the Natural Sciences and Engineering Research Council of Canada
文摘This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionless form. Further, a decoupled PD controller is proposed, and the local stability of the controller is analyzed by linearization technique. Parametric studies of the dynamics and de-spin control of a massive target are conducted to characterize the dynamic process of de-spin with the proposed control law. It is shown that the massive target can be de-span by a single and small space tug with limited thrust within finite time. The thrust tangent with the tether de-spins the target while the thrust normal to the tether prevents the tether from winding up the target. The tether length has a positive contribution to the de-spin of a target. The longer tether leads to a faster de-spin process.
基金supported by the National Natural Science Foundation of China(No.11772023)。
文摘This paper proposes a fuel-optimal deorbit scheme for space debris deorbit using tethered space tug.The scheme contains three stages named respectively as dragging,maintenance and swinging.In the first stage,the tug,propelled by continuous thrust,tows deorbit to a transfer orbit with a tether.Then in the second stage,the combination of the tug and the debris flies unpowered and uncontrolled to a swing point on the transfer orbit.Finally,in the third stage,the tug is propelled at the swing point and the rotation speed of the tethered system increases such that the debris obtains enough velocity increment.The trajectory optimization of the first stage is established considering the total fuel consumption of the three stages,whereas the dynamic model is simplified for computation efficiency.The solution to the optimal problem is obtained using a direct method based on Gauss pesudospectral discretization.Then a model predictive controller is designed to track the open-loop optimal reference trajectories,reducing the states’deviations caused by model simplification and ignorance of perturbations.Furthermore,it is proved that the fuel-optimal swing point is the apogee of the transfer orbit.The paper analyzes the fuel consumption of a typical scenario and demonstrates effectiveness of the proposed deorbit scheme numerically.
文摘Objective: This study aimed to identify correlations of laboratory test results and knee joint function between pre- and post-operation of knee joint replacement surgery. Methods: The study covered 60 - 75 aged 50 patients who had operated with knee replacement surgery. 25 patients were male and another 25 patients were female. We compared laboratory test results of pre- and 3rd, 7th and 14th day of post-operation. Moreover, pre-operation knee joint function was compared with 3rd, 7th, 14th and 30th day of post-operation. Furthermore, we investigated the relationship among WBC, hemoglobin and function tests. Pre- and post-operative knee joint function tests were conducted by WOMAC (The Western On-tario and McMaster Universities Osteoarthritis), VAS (Visual Analogue Scale), TUG (Time up and Go) score, and MMT (Muscle Manual Test). Results: In pre-operation, patients’ average WBC was 6.447 ± 2.115 cells/μL, monocyte was 6.554 ± 3.101 cells/μL, lymphocyte was 31.177 ± 9.512 cells/μL and C-reactive protein was 0.6205 ± 0.922 mg/dL. In 3rd day of post-operation, WBC was 8.901 ± 2.869 cells/μL, monocyte was 4.881 ± 2.332 cells/μL, lymphocyte was 17.048 ± 9.702 cells/μL and C-reactive protein was 4.2762 ± 2.293 mg/dL. There was a statistically significant difference reported on pre- and post-operation pain, stiffness and daily activity (P rd day of post-operation were raised up and they were statistically significant (P rd, 7th, 14th day of TUG score was significantly correlated (P Conclusion: Results of WBC, hemoglobin, hematocrit, total protein, total bilirubin, and creatinine had increased in 3rd and 7th day of post-operation and had stabilized from 14th day of post-operation. Stiffness and TUG performance were controversially correlated in 3rd, 7th, 14th, 30th day of post-operation. However, in 7th and 14th of post-operation, patients’ muscle strength and knee joint amplitude had become stabilized and improved from 30th day of post-operation. Moreover, after the operation, the number of WBC controv
文摘The log float technology from timber depot at the reservoir to log feeding rolls was studied by model tests. The model test was taken with the rule of gravitation similitude and ratio of 1∶10. Main parameters, like the amount of tug boats, hydro-accelerators and the structure of feeding rolls, were determined. The more suitable float process is put forward and the reliable basis for the design is supplied.
