The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlle...The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlled vehicle.In this context,a novel form of the prescribed performance guiding vector field is introduced,accompanied by a prescribed-time sliding mode con-trol approach.Furthermore,the interdependence among the pre-scribed parameters is discussed.To validate the effectiveness of the proposed method,numerical simulations are presented to demonstrate the efficacy of the approach.展开更多
This article investigates a multi-circular path-following formation control with reinforced transient profiles for nonholonomic vehicles connected by a digraph.A multi-circular formation controller endowed with the fe...This article investigates a multi-circular path-following formation control with reinforced transient profiles for nonholonomic vehicles connected by a digraph.A multi-circular formation controller endowed with the feature of spatial-temporal decoupling is devised for a group of vehicles guided by a virtual leader evolving along an implicit path,which allows for a circumnavigation on multiple circles with an anticipant angular spacing.In addition,notice that it typically imposes a stringent time constraint on time-sensitive enclosing scenarios,hence an improved prescribed performance control(IPPC)using novel tighter behavior boundaries is presented to enhance transient capabilities with an ensured appointed-time convergence free from any overshoots.The significant merits are that coordinated circumnavigation along different circles can be realized via executing geometric and dynamic assignments independently with modified transient profiles.Furthermore,all variables existing in the entire system are analyzed to be convergent.Simulation and experimental results are provided to validate the utility of suggested solution.展开更多
This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance ...This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance method are proposed to counteract sideslip drift caused by cross-track velocity.The proposed differentiator can accurately observe the cross-track error and sideslip angle for snake robots to avoid errors caused by calculating sideslip angle approximately.In our method,the designed piecewise auxiliary function guarantees the finite-time stability of position errors.Secondly,for the case of external disturbances and state constraints,a Barrier Lyapunov functionbased backstepping adaptive path following controller is presented to improve the robot’s robustness.The uniform ultimate boundedness of the closed-loop system is proved by analyzing stability.Additionally,a gait frequency adjustment-based virtual velocity control input is derived to achieve the exponential convergence of the tangential velocity.At last,the availability and superiority of this work are shown through simulation and experiment results.展开更多
This paper studies the moving path following(MPF)problem for fixed-wing unmanned aerial vehicle(UAV)under output constraints and wind disturbances.The vehicle is required to converge to a reference path moving with re...This paper studies the moving path following(MPF)problem for fixed-wing unmanned aerial vehicle(UAV)under output constraints and wind disturbances.The vehicle is required to converge to a reference path moving with respect to the inertial frame,while the path following error is not expected to violate the predefined boundaries.Differently from existing moving path following guidance laws,the proposed method removes complex geometric transformation by formulating the moving path following problem into a second-order time-varying control problem.A nominal moving path following guidance law is designed with disturbances and their derivatives estimated by high-order disturbance observers.To guarantee that the path following error will not exceed the prescribed bounds,a robust control barrier function is developed and incorporated into controller design with quadratic program based framework.The proposed method does not require the initial position of the UAV to be within predefined boundaries.And the safety margin concept makes error-constraint be respected even if in a noisy environment.The proposed guidance law is validated through numerical simulations of shipboard landing and hardware-in-theloop(HIL)experiments.展开更多
To solve the path following control problem for unmanned surface vehicles(USVs),a control method based on deep reinforcement learning(DRL)with long short-term memory(LSTM)networks is proposed.A distributed proximal po...To solve the path following control problem for unmanned surface vehicles(USVs),a control method based on deep reinforcement learning(DRL)with long short-term memory(LSTM)networks is proposed.A distributed proximal policy opti-mization(DPPO)algorithm,which is a modified actor-critic-based type of reinforcement learning algorithm,is adapted to improve the controller performance in repeated trials.The LSTM network structure is introduced to solve the strong temporal cor-relation USV control problem.In addition,a specially designed path dataset,including straight and curved paths,is established to simulate various sailing scenarios so that the reinforcement learning controller can obtain as much handling experience as possible.Extensive numerical simulation results demonstrate that the proposed method has better control performance under missions involving complex maneuvers than trained with limited scenarios and can potentially be applied in practice.展开更多
Objective:To access the level of knowledge,perceptions,and practice towards adverse events following immunization(AEFI)surveillance among vaccination workers in Zhejiang province,China.Methods:This was a cross-section...Objective:To access the level of knowledge,perceptions,and practice towards adverse events following immunization(AEFI)surveillance among vaccination workers in Zhejiang province,China.Methods:This was a cross-sectional survey involving 768 vaccination workers.Data were collected using self-administered questionnaires and analyzed by using SAS 9.3 software.Knowledge,perceptions,and practice on AEFI surveillance were summarized using frequency tables.The mean±SD value was used as the cut-off for defining good(values≥mean)and poor(values<mean)knowledge,perceptions or practice.Binary logistic regression analysis was used to determine sociodemographic variables associated with knowledge,perceptions,and practice towards AEFI.Results:The proportions of good knowledge,perceptions and practice on AEFI surveillance were 78.13%,57.81%and 66.15%,respectively.Having a higher education background,longer years of experience,previous training on AEFI and≥30 years of age were factors associated with good knowledge,perceptions and practice on AEFI surveillance among vaccination workers.Conclusions:Over half of the respondents had good knowledge,perceptions and practice on AEFI surveillance work.Interventions on improving the vaccination workers’knowledge,perceptions and practice on AEFI surveillance should be considered in order to develop a more effective surveillance system.展开更多
We present an integrated mathematical model of vehicle-following control for the establishment, maintenance, and re-establishment of the previous or new safe and efficient steady-following state. The hyperbolic functi...We present an integrated mathematical model of vehicle-following control for the establishment, maintenance, and re-establishment of the previous or new safe and efficient steady-following state. The hyperbolic functions are introduced to establish the corresponding mathematical models, which can describe the behavioral adjustment of the following vehicle steered by a well-experienced driver under complex vehicle following situations. According to the proposed mathematical models, the control laws of the following vehicle adjusting its own behavior can be calculated for its moving in safety,efficiency, and smoothness(comfort). Simulation results show that the safe and efficient steady-following state can be well established, maintained, and re-established by its own smooth(comfortable) behavioral adjustment with the synchronous control of the following vehicle’s velocity, acceleration, and the actual following distance.展开更多
A time-optimal aircraft-following model is introduced to address air traffic flow interference by velocity reduction. The objective function is set up as minimizing the recovery time during which the separation minima...A time-optimal aircraft-following model is introduced to address air traffic flow interference by velocity reduction. The objective function is set up as minimizing the recovery time during which the separation minima are not infringed and the separation of the air traffic flow returns to the initial separation at the terminal time. Pontryagin's minimum principle is used to solve the optimum aircraft-following velocity control law. An analytical minimum safe following separation is also provided under the time-optimal control law. The simulation results show that the precision first-order tracking accuracy is achieved without losing the separation.展开更多
Automatic navigation of an articulated drum roller, which is an articulated steering type vehicle widely used in the construction industry, is highly expected for operation cost reduction and improvement of work effi-...Automatic navigation of an articulated drum roller, which is an articulated steering type vehicle widely used in the construction industry, is highly expected for operation cost reduction and improvement of work effi- ciency. In order to achieve the path following control, considering that its steering system is articulated steering and two frames are articulated by an active revolute joint, a kinematic model and an error dynamic state-space equation of an articulated drum roller are proposed. Besides, a state- feedback control law based on Lyapunov stability theory is also designed, which can be proved to achieve the purpose of control by the analysis of stability. What's more, to evaluate the performance of the proposed method, simu- lation under the MATLAB/Simulink and experiments using positioning algorithm and errors correction at the uneven construction site are performed, with initial dis- placement error (-1.5 m), heading error (-0.11 tad) and steering angle (-0.19 rad). Finally, simulation and exper- imental results show that the errors and steering angle can decrease gradually, and converge to zero with time. Meanwhile, the control input is not saturated. An articu- lated drum roller can lock into a desired path with the proposed method in uneven fields.展开更多
The path-following control of the asymmetry underactuated unmanned surface vehicle(USV) under external disturbances such as unknown constant and irrational ocean currents is discussed, and an adaptive sliding-mode pat...The path-following control of the asymmetry underactuated unmanned surface vehicle(USV) under external disturbances such as unknown constant and irrational ocean currents is discussed, and an adaptive sliding-mode path-following control system is proposed, which comprises a path-variable updated law,a modified integral line-of-sight(ILOS) guidance law based on a time-varying lookahead distance and adaptive feedback linearizing controllers combined with sliding-mode technique. A more accurate USV model without the assumption of having diagonal inertia and damping matrices is first presented, aiming at improving the performance of the path-following control. Next, the coordinate transformation is adopted to decouple the sway dynamic from the rudder angle, and the path-following errors dynamics without non-singular problem are presented in the moving Frenet-Serret frame. Then, based on the cascaded theorem and the adaptive sliding-mode method, the adaptive control law of position errors and course error are designed, among which the lookahead distance and integral gain are all computed as different functions of cross-track error to estimate and compensate the sideslip angle caused by external disturbances adaptively. Finally, according to the Lyapunov and cascaded theorem, the control system proposed is proved to be uniform globally asymptotic stability(UGAS) and uniform semiglobal exponential stability(USGES) when the control objectives are all achieved. Simulation results illustrate the precision and high-quality performance of this new controller.展开更多
In this paper, a robust path following control law is proposed for a deep-sea manned submersible maneuvering along a predeterminated path. Developed in China, the submersible is underactuated in the horizontal plane i...In this paper, a robust path following control law is proposed for a deep-sea manned submersible maneuvering along a predeterminated path. Developed in China, the submersible is underactuated in the horizontal plane in that it is actuated by two perpendicular thrusts in this plane. The advanced non-singular terminal sliding mode (NTSM) is implemented for the design of the path following controller, which can ensure the convergence of the motion system in finite time and improve its robustness against parametric uncertainties and environmental disturbances. In the process of controller design, the close-loop stability is considered and proved by Lyapunov' s stability theory. With the experimental data, numerical simulations are provided to verify the control law for path following of the deep-sea manned submersible.展开更多
Lung cancer is the most common cancer worldwide. In the United States, it causes more cancer-related deaths than the next four causes (breast cancer, prostate cancer, colon cancer, and pancreatic cancer) of cancer-r...Lung cancer is the most common cancer worldwide. In the United States, it causes more cancer-related deaths than the next four causes (breast cancer, prostate cancer, colon cancer, and pancreatic cancer) of cancer-related mortality combined (1). About 30% of people have already progressed to stage III lung cancer and 40% to stage IV at the time they are diagnosed (2). Although chest X-ray and sputum cytology, when applied in health check-ups, can identify some relatively small tumors, they are not able to lower the overall mortality (3). More recently,展开更多
A controller which is locally optimal near the origin and globally inverse optimal for the nonlinear system is proposed for path following of over actuated marine crafts with actuator dynamics. The motivation is the e...A controller which is locally optimal near the origin and globally inverse optimal for the nonlinear system is proposed for path following of over actuated marine crafts with actuator dynamics. The motivation is the existence of undesired signals sent to the actuators, which can result in bad behavior in path following. To attenuate the oscillation of the control signal and obtain smooth thrust outputs, the actuator dynamics are added into the ship maneuvering model. Instead of modifying the Line-of-Sight (LOS) guidance law, this proposed controller can easily adjust the vessel speed to minimize the large cross-track error caused by the high vessel speed when it is turning. Numerical simulations demonstrate the validity of this proposed controller.展开更多
A path following controller is developed for underactuated ships with only surge force and yaw moment available to follow a predefined path.The proposed controller is based on nonswitch analytic model predictive contr...A path following controller is developed for underactuated ships with only surge force and yaw moment available to follow a predefined path.The proposed controller is based on nonswitch analytic model predictive control.It is shown that the optimal control law for a nonlinear path following system with ill-defined relative degree is continuous and nonsingular.The problem of ill-defined relative degree is solved.The path-following ability of the nonlinear system is guaranteed.Numerical simulations are provided to demonstrate the effectiveness of the proposed control law.展开更多
Spinal cord injury (SCI) elicits a robust inflammatory response that is a hallmark of the secondary injury mechanisms. Neuroinflammation is orchestrated initially by the response of resident astrocytes and microglia...Spinal cord injury (SCI) elicits a robust inflammatory response that is a hallmark of the secondary injury mechanisms. Neuroinflammation is orchestrated initially by the response of resident astrocytes and microglia to injury, which subsequently facilitates the recruitment of peripheral immune cells into the SCI lesion (Orr and Gensel, 2018). This inflammatory response contributes to cell death and tissue degeneration through the production of pro-inflammatory cytokines and chemokines, free radicals and proteolytic enzymes. However, neuroinflammatory cells also play beneficial regulatory role in repair mechanisms after SCI by adopting a reparative and wound healing phenotype (Orr and Gensel, 2018; Tran et al., 2018). Hence, understanding the underlying mechanisms by which immune cells are reg- ulated within the microenvironment of injury would aid in harnessing the reparative potential of inflammation following SCI.展开更多
To improve humor circulation the latest V4c Visian implantable collamer lens (ICL) was designed with a0.36-ram Aquapon. This design also eliminates the need to perform peripheral iridectomy before ICL implantation. ...To improve humor circulation the latest V4c Visian implantable collamer lens (ICL) was designed with a0.36-ram Aquapon. This design also eliminates the need to perform peripheral iridectomy before ICL implantation. Several authors reported rates of secondary surgical intervention related to insufficient vault in the presence or absence of cataract formation and excessive vault in the presence or absence of elevated intraocular pressure (IOP) after ICL insertion. Here, we report a case of rapid progression of a cataract to a hypermature state after implantation of an ICL with an Aquaport.展开更多
This paper proposes a modified lattice gas model to simulate pedestrian counter flow by considering the effect of following strength which can lead to appropriate responses to some complicated situations. Periodic and...This paper proposes a modified lattice gas model to simulate pedestrian counter flow by considering the effect of following strength which can lead to appropriate responses to some complicated situations. Periodic and open boundary conditions are adopted respectively. The simulation results show that the presented model can reproduce some essential features of pedestrian counter flows, e.g., the lane formation and segregation effect. The fundamental diagrams show that the complete jamming density is independent of the system size only when the width W and the length L are larger than some critical values respectively, and the larger asymmetrical conditions can better avoid the occurrence of deadlock phenomena. For the mixed pedestrian flow, it can be found that the jamming cluster is mainly caused by those walkers breaking the traffic rules, and the underlying mechanism is analysed. Furthermore, the comparison of simulation results and the experimental data is performed, it is shown that this modified model is reasonable and more realistic to simulate and analyse pedestrian counter flow.展开更多
To compare the early effects of hypertonic and isotonic saline resuscitation on heme oxygenase-1 (HO-1) expression in organs of rats with hemorrhagic shock. Rats were randomly divided into hypertonic saline resuscit...To compare the early effects of hypertonic and isotonic saline resuscitation on heme oxygenase-1 (HO-1) expression in organs of rats with hemorrhagic shock. Rats were randomly divided into hypertonic saline resuscitation (HTS), normal saline resuscitation (NS) and sham groups. HO-1 mRNA, protein expression and apoptosis were evaluated in organs. In the HTS group, significant difference was noted in HO-1 protein in small intestinal mucosa and liver compared with the NS and sham groups, and in HO-1 mRNA in liver and kidney compared with the sham group. The apoptosis of small intestinal mucosa, liver, heart, and lung was significantly lower in the HTS group than that in the NS group. In this study, small volume resuscitation with HTS can efficiently up-regulate the expression level of HO-1 in small intestinal mucosa and liver, which may be one of the mechanisms alleviating organ damage.展开更多
Central nervous system injuries,such as spinal cord injury(SCI),are a leading cause of disability in young adults.SCIs generally have severe clinical consequences and often lead to loss of motor or sensory input bel...Central nervous system injuries,such as spinal cord injury(SCI),are a leading cause of disability in young adults.SCIs generally have severe clinical consequences and often lead to loss of motor or sensory input below the segment of injury.展开更多
基金supported by the National Natural Science Foundation of China(62073019)。
文摘The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlled vehicle.In this context,a novel form of the prescribed performance guiding vector field is introduced,accompanied by a prescribed-time sliding mode con-trol approach.Furthermore,the interdependence among the pre-scribed parameters is discussed.To validate the effectiveness of the proposed method,numerical simulations are presented to demonstrate the efficacy of the approach.
基金supported in part by the National Natural Science Foundation of China under Grant Nos.62173312 and 61803348in part by the National Major Scientific Instruments Development Project under Grant No.61927807+3 种基金in part by the Program for the Innovative Talents of Higher Education Institutions of ShanxiShanxi Province Science Foundation for Excellent Youthsin part by the Shanxi"1331 Project"Key Subjects Construction(1331KSC)in part by Graduate Innovation Project of Shanxi Province under Grant No.2021Y617。
文摘This article investigates a multi-circular path-following formation control with reinforced transient profiles for nonholonomic vehicles connected by a digraph.A multi-circular formation controller endowed with the feature of spatial-temporal decoupling is devised for a group of vehicles guided by a virtual leader evolving along an implicit path,which allows for a circumnavigation on multiple circles with an anticipant angular spacing.In addition,notice that it typically imposes a stringent time constraint on time-sensitive enclosing scenarios,hence an improved prescribed performance control(IPPC)using novel tighter behavior boundaries is presented to enhance transient capabilities with an ensured appointed-time convergence free from any overshoots.The significant merits are that coordinated circumnavigation along different circles can be realized via executing geometric and dynamic assignments independently with modified transient profiles.Furthermore,all variables existing in the entire system are analyzed to be convergent.Simulation and experimental results are provided to validate the utility of suggested solution.
基金supported in part by the National Natural Science Foundation of China(61825305,62171274,U1933125,U2241228,62273019)the Shanghai Science and Technology Major Project(2021SHZDZX)+2 种基金the National Natural Science Foundation of China through the Main Research Projecton Machine Behavior and Human-Machine Collaborated Decision Making Methodology(72192820)the Third Research Projecton Human Behavior in HumanMachine Collaboration(72192822)the China Postdoctoral Science Foundation(2022M710093)。
文摘This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance method are proposed to counteract sideslip drift caused by cross-track velocity.The proposed differentiator can accurately observe the cross-track error and sideslip angle for snake robots to avoid errors caused by calculating sideslip angle approximately.In our method,the designed piecewise auxiliary function guarantees the finite-time stability of position errors.Secondly,for the case of external disturbances and state constraints,a Barrier Lyapunov functionbased backstepping adaptive path following controller is presented to improve the robot’s robustness.The uniform ultimate boundedness of the closed-loop system is proved by analyzing stability.Additionally,a gait frequency adjustment-based virtual velocity control input is derived to achieve the exponential convergence of the tangential velocity.At last,the availability and superiority of this work are shown through simulation and experiment results.
基金supported in part by the National Natural Science Foundations of China(62173016,62073019)the Fundamental Research Funds for the Central Universities(YWF-23-JC-04,YWF-23-JC-02)。
文摘This paper studies the moving path following(MPF)problem for fixed-wing unmanned aerial vehicle(UAV)under output constraints and wind disturbances.The vehicle is required to converge to a reference path moving with respect to the inertial frame,while the path following error is not expected to violate the predefined boundaries.Differently from existing moving path following guidance laws,the proposed method removes complex geometric transformation by formulating the moving path following problem into a second-order time-varying control problem.A nominal moving path following guidance law is designed with disturbances and their derivatives estimated by high-order disturbance observers.To guarantee that the path following error will not exceed the prescribed bounds,a robust control barrier function is developed and incorporated into controller design with quadratic program based framework.The proposed method does not require the initial position of the UAV to be within predefined boundaries.And the safety margin concept makes error-constraint be respected even if in a noisy environment.The proposed guidance law is validated through numerical simulations of shipboard landing and hardware-in-theloop(HIL)experiments.
基金supported by the National Natural Science Foundation(61601491)the Natural Science Foundation of Hubei Province(2018CFC865)the China Postdoctoral Science Foundation Funded Project(2016T45686).
文摘To solve the path following control problem for unmanned surface vehicles(USVs),a control method based on deep reinforcement learning(DRL)with long short-term memory(LSTM)networks is proposed.A distributed proximal policy opti-mization(DPPO)algorithm,which is a modified actor-critic-based type of reinforcement learning algorithm,is adapted to improve the controller performance in repeated trials.The LSTM network structure is introduced to solve the strong temporal cor-relation USV control problem.In addition,a specially designed path dataset,including straight and curved paths,is established to simulate various sailing scenarios so that the reinforcement learning controller can obtain as much handling experience as possible.Extensive numerical simulation results demonstrate that the proposed method has better control performance under missions involving complex maneuvers than trained with limited scenarios and can potentially be applied in practice.
基金funded by medical and health science and technology project of Zhejiang province (Grant number:2023KY633)
文摘Objective:To access the level of knowledge,perceptions,and practice towards adverse events following immunization(AEFI)surveillance among vaccination workers in Zhejiang province,China.Methods:This was a cross-sectional survey involving 768 vaccination workers.Data were collected using self-administered questionnaires and analyzed by using SAS 9.3 software.Knowledge,perceptions,and practice on AEFI surveillance were summarized using frequency tables.The mean±SD value was used as the cut-off for defining good(values≥mean)and poor(values<mean)knowledge,perceptions or practice.Binary logistic regression analysis was used to determine sociodemographic variables associated with knowledge,perceptions,and practice towards AEFI.Results:The proportions of good knowledge,perceptions and practice on AEFI surveillance were 78.13%,57.81%and 66.15%,respectively.Having a higher education background,longer years of experience,previous training on AEFI and≥30 years of age were factors associated with good knowledge,perceptions and practice on AEFI surveillance among vaccination workers.Conclusions:Over half of the respondents had good knowledge,perceptions and practice on AEFI surveillance work.Interventions on improving the vaccination workers’knowledge,perceptions and practice on AEFI surveillance should be considered in order to develop a more effective surveillance system.
基金supported by the National Natural Science Foundation of China(Grant No.61174183)
文摘We present an integrated mathematical model of vehicle-following control for the establishment, maintenance, and re-establishment of the previous or new safe and efficient steady-following state. The hyperbolic functions are introduced to establish the corresponding mathematical models, which can describe the behavioral adjustment of the following vehicle steered by a well-experienced driver under complex vehicle following situations. According to the proposed mathematical models, the control laws of the following vehicle adjusting its own behavior can be calculated for its moving in safety,efficiency, and smoothness(comfort). Simulation results show that the safe and efficient steady-following state can be well established, maintained, and re-established by its own smooth(comfortable) behavioral adjustment with the synchronous control of the following vehicle’s velocity, acceleration, and the actual following distance.
基金supported by the National Natural Science Foundations of China (Nos. 60972006 and61179042)the National Science and Technology Support Program (No. 2011BAH24B10)
文摘A time-optimal aircraft-following model is introduced to address air traffic flow interference by velocity reduction. The objective function is set up as minimizing the recovery time during which the separation minima are not infringed and the separation of the air traffic flow returns to the initial separation at the terminal time. Pontryagin's minimum principle is used to solve the optimum aircraft-following velocity control law. An analytical minimum safe following separation is also provided under the time-optimal control law. The simulation results show that the precision first-order tracking accuracy is achieved without losing the separation.
基金Supported by National Key Technology Support Program of China(Grant No.2015BAF07B05)Fundamental Research Funds for the Central Universities of China
文摘Automatic navigation of an articulated drum roller, which is an articulated steering type vehicle widely used in the construction industry, is highly expected for operation cost reduction and improvement of work effi- ciency. In order to achieve the path following control, considering that its steering system is articulated steering and two frames are articulated by an active revolute joint, a kinematic model and an error dynamic state-space equation of an articulated drum roller are proposed. Besides, a state- feedback control law based on Lyapunov stability theory is also designed, which can be proved to achieve the purpose of control by the analysis of stability. What's more, to evaluate the performance of the proposed method, simu- lation under the MATLAB/Simulink and experiments using positioning algorithm and errors correction at the uneven construction site are performed, with initial dis- placement error (-1.5 m), heading error (-0.11 tad) and steering angle (-0.19 rad). Finally, simulation and exper- imental results show that the errors and steering angle can decrease gradually, and converge to zero with time. Meanwhile, the control input is not saturated. An articu- lated drum roller can lock into a desired path with the proposed method in uneven fields.
基金supported by the National Social Science Foundation of China(15GJ003-278)the National Natural Science Foundation of China(71501182)
文摘The path-following control of the asymmetry underactuated unmanned surface vehicle(USV) under external disturbances such as unknown constant and irrational ocean currents is discussed, and an adaptive sliding-mode path-following control system is proposed, which comprises a path-variable updated law,a modified integral line-of-sight(ILOS) guidance law based on a time-varying lookahead distance and adaptive feedback linearizing controllers combined with sliding-mode technique. A more accurate USV model without the assumption of having diagonal inertia and damping matrices is first presented, aiming at improving the performance of the path-following control. Next, the coordinate transformation is adopted to decouple the sway dynamic from the rudder angle, and the path-following errors dynamics without non-singular problem are presented in the moving Frenet-Serret frame. Then, based on the cascaded theorem and the adaptive sliding-mode method, the adaptive control law of position errors and course error are designed, among which the lookahead distance and integral gain are all computed as different functions of cross-track error to estimate and compensate the sideslip angle caused by external disturbances adaptively. Finally, according to the Lyapunov and cascaded theorem, the control system proposed is proved to be uniform globally asymptotic stability(UGAS) and uniform semiglobal exponential stability(USGES) when the control objectives are all achieved. Simulation results illustrate the precision and high-quality performance of this new controller.
基金The paper was financially supported by the National High Technology Research and Development Programof China(863 Program) (Grant No.2002AA401002)
文摘In this paper, a robust path following control law is proposed for a deep-sea manned submersible maneuvering along a predeterminated path. Developed in China, the submersible is underactuated in the horizontal plane in that it is actuated by two perpendicular thrusts in this plane. The advanced non-singular terminal sliding mode (NTSM) is implemented for the design of the path following controller, which can ensure the convergence of the motion system in finite time and improve its robustness against parametric uncertainties and environmental disturbances. In the process of controller design, the close-loop stability is considered and proved by Lyapunov' s stability theory. With the experimental data, numerical simulations are provided to verify the control law for path following of the deep-sea manned submersible.
文摘Lung cancer is the most common cancer worldwide. In the United States, it causes more cancer-related deaths than the next four causes (breast cancer, prostate cancer, colon cancer, and pancreatic cancer) of cancer-related mortality combined (1). About 30% of people have already progressed to stage III lung cancer and 40% to stage IV at the time they are diagnosed (2). Although chest X-ray and sputum cytology, when applied in health check-ups, can identify some relatively small tumors, they are not able to lower the overall mortality (3). More recently,
基金Supported by the National Natural Science Foundation of China under Grant Nos. 61301279, 51479158 and the Fundamental Research Funds for the Central Universities under Grant No. WUT: 163102006
文摘A controller which is locally optimal near the origin and globally inverse optimal for the nonlinear system is proposed for path following of over actuated marine crafts with actuator dynamics. The motivation is the existence of undesired signals sent to the actuators, which can result in bad behavior in path following. To attenuate the oscillation of the control signal and obtain smooth thrust outputs, the actuator dynamics are added into the ship maneuvering model. Instead of modifying the Line-of-Sight (LOS) guidance law, this proposed controller can easily adjust the vessel speed to minimize the large cross-track error caused by the high vessel speed when it is turning. Numerical simulations demonstrate the validity of this proposed controller.
基金supported by the National Natural Science Foundation of China(No.50779033)the National High Technology Research and Development Program(863 Program)of China(No.2007AA11Z250)
文摘A path following controller is developed for underactuated ships with only surge force and yaw moment available to follow a predefined path.The proposed controller is based on nonswitch analytic model predictive control.It is shown that the optimal control law for a nonlinear path following system with ill-defined relative degree is continuous and nonsingular.The problem of ill-defined relative degree is solved.The path-following ability of the nonlinear system is guaranteed.Numerical simulations are provided to demonstrate the effectiveness of the proposed control law.
基金supported by the Craig H.Neilsen Foundation awarded to SKAsupported by a joint studentship from Will-to-Win/Manitoba Paraplegic Foundationthe Children’s Hospital Research Institute of Manitoba
文摘Spinal cord injury (SCI) elicits a robust inflammatory response that is a hallmark of the secondary injury mechanisms. Neuroinflammation is orchestrated initially by the response of resident astrocytes and microglia to injury, which subsequently facilitates the recruitment of peripheral immune cells into the SCI lesion (Orr and Gensel, 2018). This inflammatory response contributes to cell death and tissue degeneration through the production of pro-inflammatory cytokines and chemokines, free radicals and proteolytic enzymes. However, neuroinflammatory cells also play beneficial regulatory role in repair mechanisms after SCI by adopting a reparative and wound healing phenotype (Orr and Gensel, 2018; Tran et al., 2018). Hence, understanding the underlying mechanisms by which immune cells are reg- ulated within the microenvironment of injury would aid in harnessing the reparative potential of inflammation following SCI.
基金Supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(No.2017R1A2B4012327)
文摘To improve humor circulation the latest V4c Visian implantable collamer lens (ICL) was designed with a0.36-ram Aquapon. This design also eliminates the need to perform peripheral iridectomy before ICL implantation. Several authors reported rates of secondary surgical intervention related to insufficient vault in the presence or absence of cataract formation and excessive vault in the presence or absence of elevated intraocular pressure (IOP) after ICL insertion. Here, we report a case of rapid progression of a cataract to a hypermature state after implantation of an ICL with an Aquaport.
基金supported by the National Basic Research Program of China (Grant No. 2006CB705500)the National Natural Science Foundation of China (Grant Nos. 10962002,10902076 and 10532060)
文摘This paper proposes a modified lattice gas model to simulate pedestrian counter flow by considering the effect of following strength which can lead to appropriate responses to some complicated situations. Periodic and open boundary conditions are adopted respectively. The simulation results show that the presented model can reproduce some essential features of pedestrian counter flows, e.g., the lane formation and segregation effect. The fundamental diagrams show that the complete jamming density is independent of the system size only when the width W and the length L are larger than some critical values respectively, and the larger asymmetrical conditions can better avoid the occurrence of deadlock phenomena. For the mixed pedestrian flow, it can be found that the jamming cluster is mainly caused by those walkers breaking the traffic rules, and the underlying mechanism is analysed. Furthermore, the comparison of simulation results and the experimental data is performed, it is shown that this modified model is reasonable and more realistic to simulate and analyse pedestrian counter flow.
基金supported by the Zhejiang Provincial Natural Science Foundation of China (No.Y2100430)the Zhejiang Provincial Education and Research Foundation of China (No. Y201019154)
文摘To compare the early effects of hypertonic and isotonic saline resuscitation on heme oxygenase-1 (HO-1) expression in organs of rats with hemorrhagic shock. Rats were randomly divided into hypertonic saline resuscitation (HTS), normal saline resuscitation (NS) and sham groups. HO-1 mRNA, protein expression and apoptosis were evaluated in organs. In the HTS group, significant difference was noted in HO-1 protein in small intestinal mucosa and liver compared with the NS and sham groups, and in HO-1 mRNA in liver and kidney compared with the sham group. The apoptosis of small intestinal mucosa, liver, heart, and lung was significantly lower in the HTS group than that in the NS group. In this study, small volume resuscitation with HTS can efficiently up-regulate the expression level of HO-1 in small intestinal mucosa and liver, which may be one of the mechanisms alleviating organ damage.
基金supported by grants from the Deutsche Forschungsgemeinschaft (DFG, SFB870)the Munich Center for System Neurology (Sy Nergy, EXC1010)
文摘Central nervous system injuries,such as spinal cord injury(SCI),are a leading cause of disability in young adults.SCIs generally have severe clinical consequences and often lead to loss of motor or sensory input below the segment of injury.