This paper proposed a new libration decoupling analytical speed function(LD-ASF)in lieu of the classic analytical speed function to control the climber's speed along a partial space elevator to improve libration s...This paper proposed a new libration decoupling analytical speed function(LD-ASF)in lieu of the classic analytical speed function to control the climber's speed along a partial space elevator to improve libration stability in cargo transportation.The LD-ASF is further optimized for payload transportation efficiency by a novel coordinate game theory to balance competing control objectives among payload transport speed,stable end body's libration,and overall control input via model predictive control.The transfer period is divided into several sections to reduce computational burden.The validity and efficacy of the proposed LD-ASF and coordinate game-based model predictive control are demonstrated by computer simulation.Numerical results reveal that the optimized LD-ASF results in higher transportation speed,stable end body's libration,lower thrust fuel consumption,and more flexible optimization space than the classic analytical speed function.展开更多
This paper studies the libration and stabilization of a parallel partial space elevator system in circular orbits. The system is made up of two paralleled partial space elevators, each of which consists of one main sa...This paper studies the libration and stabilization of a parallel partial space elevator system in circular orbits. The system is made up of two paralleled partial space elevators, each of which consists of one main satellite, one end body and a climber moving along the tether between them.The libration characteristics of the elevator are studied through numerical analysis by a new dynamic model, and a novel control strategy is proposed to stabilize the swing of the end body by projecting the climber speeds only. Optimal control method is used to implement the new control strategy in the case where the climbers move in opposite direction. The simulation results validate the effectiveness of the proposed control strategy whose application will neither sacrifice the transport efficiency nor exacerbate libration significantly.展开更多
The deployment of a long tether to operate as a partial space elevator,starting from a nucleus in geostationary orbit,is studied.Uncontrolled deployment is an inherently unstable process because the center of orbit gr...The deployment of a long tether to operate as a partial space elevator,starting from a nucleus in geostationary orbit,is studied.Uncontrolled deployment is an inherently unstable process because the center of orbit gradually decreases from the geostationary altitude when deployment progresses.It is also observed that the elasticity of the tether has an important effect on deployment stability.It is shown that the application of a transverse force on the main spacecraft,determined by using linear state feedback and appropriate gains,can stabilize the deployment.An LQR controller is developed.Simulations of the dynamics of the system are carried out using this controller for various parametric values of tether elasticity,deployment rates,etc.,to evaluate the efficacy of the controller.展开更多
A floating partial space elevator(PSE)is a PSE with a floating main satellite.This work aims to keep the orbital radius of the main satellite of a floating PSE in cargo transposition without the use of thrusts.A six-d...A floating partial space elevator(PSE)is a PSE with a floating main satellite.This work aims to keep the orbital radius of the main satellite of a floating PSE in cargo transposition without the use of thrusts.A six-degree-of-freedom two-piece dumbbell model was built to analyze the dynamics of a floating PSE.By adjusting the climber’s moving speed and rolling of the end body,the main satellite’s orbital radius can be kept.A novel control strategy using a proportional shrinking horizon model predictive control law containing a self-stability modified law is proposed to stabilize both the orbital and libration states to regulate the speed of only the climber.Simulation results validated the proposed control strategy.The system provides a successful approach to the desired equilibrium by the end of the transposition.展开更多
Elevators,as an enclosed and often crowded space,pose a high risk of airborne infections due to ineffective ventilation.To mitigate this issue,this study introduces a reinforced exhaust at low velocity(RELV)system,spe...Elevators,as an enclosed and often crowded space,pose a high risk of airborne infections due to ineffective ventilation.To mitigate this issue,this study introduces a reinforced exhaust at low velocity(RELV)system,specifically designed to enhance aerosol removal efficiency in elevators.The performance of the RELV system was assessed through computational fluid dynamics(CFD)simulations,employing the Renormalization Group(RNG)k–εturbulence model to simulate airflow and the Lagrangian method to track particle motion.The RELV system was benchmarked against three conventional ventilation strategies:mixed ventilation(MV),displacement ventilation(DV),and local exhaust(Exhaust).Results demonstrated that the RELV system,optimized at a momentum ratio of 0.2,achieved a remarkable 72.9% aerosol removal efficiency within 120 s,significantly outperforming the 16.1%removal efficiency of the MV system under Scenario I,where the patient was located at the elevator’s center.Furthermore,the viral aerosol concentration in the breathing zone was reduced from 2.03×10^(-2) mg/cm^(3) in the MV system to 1.02×10^(-3) mg/cm^(3) in the RELV system.The RELV system features simple design and compatibility with existing ventilation systems,offering an effective solution to improve air quality in elevators and other enclosed environments.Additionally,this study provides a velocity decay curve for low-velocity jets in the RELV system.This curve offers valuable insights for designing ventilation systems in similar settings.展开更多
基金funded by the National Natural Science Foundation of China(12102487)Basic and Applied Basic Research Foundation of Guangdong Province,China(2023A1515012339)+1 种基金Shenzhen Science and Technology Program(ZDSYS20210623091808026)the Discovery Grant(RGPIN-2024-06290)of the Natural Sciences and Engineering Research Council of Canada。
文摘This paper proposed a new libration decoupling analytical speed function(LD-ASF)in lieu of the classic analytical speed function to control the climber's speed along a partial space elevator to improve libration stability in cargo transportation.The LD-ASF is further optimized for payload transportation efficiency by a novel coordinate game theory to balance competing control objectives among payload transport speed,stable end body's libration,and overall control input via model predictive control.The transfer period is divided into several sections to reduce computational burden.The validity and efficacy of the proposed LD-ASF and coordinate game-based model predictive control are demonstrated by computer simulation.Numerical results reveal that the optimized LD-ASF results in higher transportation speed,stable end body's libration,lower thrust fuel consumption,and more flexible optimization space than the classic analytical speed function.
基金supported by the Discovery Grant (No. RGPIN2018-05991)Discovery Accelerate Supplement Grant (No. RGPAS-2018-522709) of Natural Sciences and Engineering Research Council of CanadaGuangdong Basic and Applied Basic Research Foundation (No. 2019A1515111056)。
文摘This paper studies the libration and stabilization of a parallel partial space elevator system in circular orbits. The system is made up of two paralleled partial space elevators, each of which consists of one main satellite, one end body and a climber moving along the tether between them.The libration characteristics of the elevator are studied through numerical analysis by a new dynamic model, and a novel control strategy is proposed to stabilize the swing of the end body by projecting the climber speeds only. Optimal control method is used to implement the new control strategy in the case where the climbers move in opposite direction. The simulation results validate the effectiveness of the proposed control strategy whose application will neither sacrifice the transport efficiency nor exacerbate libration significantly.
文摘The deployment of a long tether to operate as a partial space elevator,starting from a nucleus in geostationary orbit,is studied.Uncontrolled deployment is an inherently unstable process because the center of orbit gradually decreases from the geostationary altitude when deployment progresses.It is also observed that the elasticity of the tether has an important effect on deployment stability.It is shown that the application of a transverse force on the main spacecraft,determined by using linear state feedback and appropriate gains,can stabilize the deployment.An LQR controller is developed.Simulations of the dynamics of the system are carried out using this controller for various parametric values of tether elasticity,deployment rates,etc.,to evaluate the efficacy of the controller.
基金This work was funded by the National Natural Science Foundation of China(12102487)Guangdong Basic and Applied Basic Research Foundation(2019A1515111056)Discovery Grant(RGPIN-2018-05991)of the Natural Sciences and Engineering Research Council of Canada.
文摘A floating partial space elevator(PSE)is a PSE with a floating main satellite.This work aims to keep the orbital radius of the main satellite of a floating PSE in cargo transposition without the use of thrusts.A six-degree-of-freedom two-piece dumbbell model was built to analyze the dynamics of a floating PSE.By adjusting the climber’s moving speed and rolling of the end body,the main satellite’s orbital radius can be kept.A novel control strategy using a proportional shrinking horizon model predictive control law containing a self-stability modified law is proposed to stabilize both the orbital and libration states to regulate the speed of only the climber.Simulation results validated the proposed control strategy.The system provides a successful approach to the desired equilibrium by the end of the transposition.
基金supported by the National Key R&D Program of the Ministry of Science and Technology,China,on“National Quality Infrastructure(NQI)”(Grant No.2023YFF0613101)the National Natural Science Foundation of China(NSFC)through Grant No.52108084.
文摘Elevators,as an enclosed and often crowded space,pose a high risk of airborne infections due to ineffective ventilation.To mitigate this issue,this study introduces a reinforced exhaust at low velocity(RELV)system,specifically designed to enhance aerosol removal efficiency in elevators.The performance of the RELV system was assessed through computational fluid dynamics(CFD)simulations,employing the Renormalization Group(RNG)k–εturbulence model to simulate airflow and the Lagrangian method to track particle motion.The RELV system was benchmarked against three conventional ventilation strategies:mixed ventilation(MV),displacement ventilation(DV),and local exhaust(Exhaust).Results demonstrated that the RELV system,optimized at a momentum ratio of 0.2,achieved a remarkable 72.9% aerosol removal efficiency within 120 s,significantly outperforming the 16.1%removal efficiency of the MV system under Scenario I,where the patient was located at the elevator’s center.Furthermore,the viral aerosol concentration in the breathing zone was reduced from 2.03×10^(-2) mg/cm^(3) in the MV system to 1.02×10^(-3) mg/cm^(3) in the RELV system.The RELV system features simple design and compatibility with existing ventilation systems,offering an effective solution to improve air quality in elevators and other enclosed environments.Additionally,this study provides a velocity decay curve for low-velocity jets in the RELV system.This curve offers valuable insights for designing ventilation systems in similar settings.
