This paper addresses a three-dimensional(3D)trajectory tracking problem of underactuated autonomous underwater vehicles(AUVs)subjected to input saturation and external disturbances.The proposed controller can achieve ...This paper addresses a three-dimensional(3D)trajectory tracking problem of underactuated autonomous underwater vehicles(AUVs)subjected to input saturation and external disturbances.The proposed controller can achieve practical convergence of tracking errors for general reference trajectories,including persistently exciting(PE)time varying trajectories and fixed points.At first,a modified error state formulation is introduced to tackle the situation that desired velocities do not satisfy PE condition.Then,on the basis of the backstepping technique and a Nussbaum-type even function,a saturated controller is designed so that the tracking errors can converge to a bounded neighborhood of the origin.The stability analysis based on Lyapunov theory shows that the tracking errors are globally ultimately uniformly bounded.Finally,some simulation results illustrate the effectiveness and robustness of the proposed control strategy.展开更多
This paper studies the tracking control problem for stratospheric airships with userspecified performance.Dealing with the infinite gain phenomenon in the prescribed-time stability,a new stability criterion with bound...This paper studies the tracking control problem for stratospheric airships with userspecified performance.Dealing with the infinite gain phenomenon in the prescribed-time stability,a new stability criterion with bounded gain is proposed by using a new time-varying scaling function.Moreover,a same-side performance function and a novel barrier Lyapunov function are incorporated into the control algorithm,which can compress the feasible domain of tracking error to minimize the overshoot and solve the difficult in tracking error not converging to zero simultaneously.The proposed scheme guarantees the airship capable of operating autonomously with satisfactory transient performance and tracking accuracy,where the performance parameters can be designed artificially and link to the physical process directly.Finally,the effectiveness of the proposed control scheme is verified by theoretical analysis and numerical simulation.展开更多
The problem of trajectory tracking for a class of differentially driven wheeled mobile robots(WMRs)under partial loss of the effectiveness of the actuated wheels is investigated in this paper.Such actuator faults may ...The problem of trajectory tracking for a class of differentially driven wheeled mobile robots(WMRs)under partial loss of the effectiveness of the actuated wheels is investigated in this paper.Such actuator faults may cause the loss of strong controllability of the WMR,such that the conventional fault-tolerant control strategies unworkable.In this paper,a new mixed-gain adaption scheme is devised,which is adopted to adapt the gain of a decoupling prescribed performance controller to adaptively compensate for the loss of the effectiveness of the actuators.Different from the existing gain adaption technique which depends on both the barrier functions and their partial derivatives,ours involves only the barrier functions.This yields a lower magnitude of the resulting control signals.Our controller accomplishes trajectory tracking of the WMR with the prescribed rate and accuracy even in the faulty case,and the control design relies on neither the information of the WMR dynamics and the actuator faults nor the tools for function approximation,parameter identification,and fault detection or estimation.The comparative simulation results justify the theoretical findings.展开更多
Automated valet parking systems based on parking automated guided vehicles(P-AGVs)are effective for improving parking convenience and increasing parking density.The ability of P-AGVs to move towards any position and a...Automated valet parking systems based on parking automated guided vehicles(P-AGVs)are effective for improving parking convenience and increasing parking density.The ability of P-AGVs to move towards any position and attain any orientation simultaneously due to their mecanum wheels makes it convenient to transport vehicles in a parking lot.In this study,a nonlinear disturbance observer-based sliding mode controller for the trajectory tracking problem of a P-AGV is proposed.The kinematic and dynamic models for a P-AGV tracking trajectory are first analyzed in sequence and the influences of disturbing forces considered.Subsequently,a nonlinear disturbance observer(NDO)is designed to estimate the disturbing forces and torques generated by the caster wheels.Based on the designed NDO,a robust nonsingular terminal sliding-mode(NTSM)controller is used to track reference trajectories.The stabilities of the NDO and NDO-NTSM control systems are theoretically verified using their Lyapunov functions.Finally,simulations and experiments are performed to verify the effectiveness of the proposed control scheme.The experimental results show that the proposed NDO-NTSM controller can improve the trajectory tracking stability by 42-68%compared to a traditional NTSM controller.The NDO-based sliding mode controller for trajectory tracking proposed in this study can effectively reduce the impact of disturbances on trajectory tracking accuracy.展开更多
The diffusion trajectory of a Brownian particle passing over the saddle point of a two-dimensional quadratic potential energy surface is tracked in detail according to the deep learning strategies.Generative adversari...The diffusion trajectory of a Brownian particle passing over the saddle point of a two-dimensional quadratic potential energy surface is tracked in detail according to the deep learning strategies.Generative adversarial networks(GANs)emanating in the category of machine learning(ML)frameworks are used to generate and assess the rationality of the data.While their optimization is based on the long short-term memory(LSTM)strategies.In addition to drawing a heat map,the optimal path of two-dimensional(2D)diffusion is simultaneously demonstrated in a stereoscopic space.The results of our simulation are completely consistent with the previous theoretical predictions.展开更多
To achieve high-precision trajectory following during helicopter maneuver tasks and reduce the disruptive influences of unknown variabilities,this study introduces a cascaded-loop helicopter trajectory tracking contro...To achieve high-precision trajectory following during helicopter maneuver tasks and reduce the disruptive influences of unknown variabilities,this study introduces a cascaded-loop helicopter trajectory tracking controller,whose parameters are set using an Ant Colony OptimizationSlime Mould Algorithm(ACO-SMA).Initially,a nonlinear flight dynamics model of the helicopter is constructed.Observer gain functions and nonlinear feedback from a vibrational suppression function to improve the tracking performance of the controller,addressing issues in disturbance estimation and compensation of the Active Disturbance Rejection Control(ADRC).Simultaneously,a cascaded loop system,comprising an internal attitude loop and an external position loop,is created,and the ant colony-slime mold hybrid algorithm optimizes the system parameters of the trajectory tracking controller.Finally,helicopter trajectory tracking simulation experiments are conducted,including spiral ascending and“8”shape climbing maneuvers.The findings indicate that the ADRC employed for helicopter trajectory tracking exhibits outstanding performance in rejecting disturbances caused by gusts and accurately tracking trajectories.The trajectory tracking controller,whose parameters are optimized by the ACO-SMA,shows higher tracking precision compared to the conventional PID and ADRC,thereby substantially improving the precision of maneuver tasks.展开更多
This paper proposes a separated trajectory tracking controller for fishing ships at sea state level 6 to solve the trajectory tracking problem of a fishing ship in a 6-level sea state,and to adapt to different working...This paper proposes a separated trajectory tracking controller for fishing ships at sea state level 6 to solve the trajectory tracking problem of a fishing ship in a 6-level sea state,and to adapt to different working environments and safety requirements.The nonlinear feedback method is used to improve the closed-loop gain shaping algorithm.By introducing the sine function,the problem of excessive control energy of the system can be effectively solved.Moreover,an integral separation design is used to solve the influence of the integral term in conventional PID controllers on the transient performance of the system.In this paper,a common 32.98 m large fiberglass reinforced plastic(FRP)trawler is adopted for simulation research at the winds scale of Beaufort No.7.The results show that the track error is smaller than 3.5 m.The method is safe,feasible,concise and effective and has popularization value in the direction of fishing ship trajectory tracking control.This method can be used to improve the level of informatization and intelligence of fishing ships.展开更多
Four-Wheel Independent Steering(4WIS)Vehicles can independently control the angle of each wheel,demonstrating superior trajectory tracking performance under normal conditions.However,on intermittent icy and snowy road...Four-Wheel Independent Steering(4WIS)Vehicles can independently control the angle of each wheel,demonstrating superior trajectory tracking performance under normal conditions.However,on intermittent icy and snowy roads,the presence of time-varying adhesion coefficients,time-varying cornering stiffness,and the irregularities due to ice and snow accumulation introduce multiple uncertainties into the steering system,significantly degrading the trajectory tracking performance of 4WIS vehicles.In response,this paper proposes a robust Tube Model Predictive Control(Tube-MPC)trajectory tracking control method for 4WIS.In this method,a Bi-directional Long Short-Term Memory neural network is established for online estimation of tire cornering stiffness under different road adhesion coefficients,providing accurate estimation of time-varying cornering stiffness for each wheel to mitigate the uncertainties of time-varying adhesion coefficients and cornering stiffness.Additionally,considering the road irregularities caused by snow accumulation on intermittent icy and snowy roads,a trajectory tracking controller that integrates Tube-MPC and robust Sliding Mode Control is proposed.The nominal MPC model,developed from the estimated tire cornering stiffness,utilizes the sliding surface and the optimal auxiliary control unit law for the tube is derived from the reaching law in Tube-MPC,aiming to minimize the trajectory tracking error while enhancing the controller’s robustness against road uncertainties.The experiments show that the proposed method outperforms the Tube-MPC algorithm in terms of trajectory accuracy and robustness.This method demonstrates excellent trajectory tracking accuracy under intermittent icy and snowy road conditions,and it lays a theoretical foundation for future studies on vehicle stability and trajectory tracking under such road conditions.展开更多
A hybrid control strategy integrating proportional derivative(PD)and the H-infinity control methodology is proposed for a serial two-link robotic manipulator with the goal of improving the tracking performance of the ...A hybrid control strategy integrating proportional derivative(PD)and the H-infinity control methodology is proposed for a serial two-link robotic manipulator with the goal of improving the tracking performance of the robot arm.The H-infinity controller has the ability to achieve a high performance and robustness in the presence of disturbances and uncertainties,while the PD controller is effective in stabilizing the manipulator.Simulation results using Matlab and Simulink show that the proposed hybrid controller,which integrates the advantages of both PD and H-infinity controllers,has the lowest rise time for the second link,the lowest settling time for the two links,the lowest peak time for both links,and the fastest decay of the error response.In addition,the hybrid control scheme also has the lowest mean square error value,with a 53.3%improvement over the H-infinity controller and a 91.8%improvement over the PD controller,indicating an improved trajectory tracking performance when compared with pure PD and pure H-infinity controllers,respectively.It was also found that the hybrid controller has the lowest integral absolute error,integral square error,integral time absolute error,and integral time square error for the second link,while the error values for the first link are satisfactory,showing a superior performance of the hybrid controller above the PD and H-infinity controllers,respectively.展开更多
Objective To evaluate left atrial function in essential hypertension patients with different patterns of left ventricular geometric models by real-time three-dimensional echocardiography （RT-3DE） and left atrial tra...Objective To evaluate left atrial function in essential hypertension patients with different patterns of left ventricular geometric models by real-time three-dimensional echocardiography （RT-3DE） and left atrial tracking （EAT）.展开更多
The Kuroshio Extension(KE)is one of the most eddy-energetic regions in the global ocean.However,most mesoscale eddy studies in the region are focused on surface eddies and the structure and characteristics of three-di...The Kuroshio Extension(KE)is one of the most eddy-energetic regions in the global ocean.However,most mesoscale eddy studies in the region are focused on surface eddies and the structure and characteristics of three-dimensional(3-D)eddies require additional research.In this study,we proposed a 3-D eddy identification and tracking algorithm based on pressure anomalies,similar to sea level anomalies(SLAs)for surface eddy identification.We applied this scheme to a 5-year(2008-2012)high-resolution numerical product to develop a 3-D eddy dataset in the KE.The reliability of the numerical product was verified by the 5-year temperature/salinity hydrological characteristics and surface eddy distribution.According to the 3-D eddy tracking dataset,the number of eddies decreased dramatically as the eddy existence-time increased and more anticyclonic eddies(AEs)had an existence-time longer than 1 week than cyclonic eddies(CEs).We presented daily variations in the 3-D structure of two 3-D eddy-tracking trajectories that exhibit a certain jump in depth and a shift toward the west and equator.In addition to the bowl,lens,and cone eddies that have been discovered by previous researchers,we found that there is a cylindrical eddy,and its eddy radii are almost consistent across all layers.CEs cause significant negative temperature anomalies,“negative-positive”salinity anomalies,and sinking current fields in the KE region,while AEs cause positive temperature anomalies,“positive-negative”salinity anomalies,and upward current fields.The four types of eddies have different effects on the temperature/salinity anomalies and current field distribution which are related to their structure.展开更多
This paper addresses the problem of three-dimensional trajectory tracking control for underactuated autonomous underwater vehicles in the presence of parametric uncertainties,environmental disturbances and input satur...This paper addresses the problem of three-dimensional trajectory tracking control for underactuated autonomous underwater vehicles in the presence of parametric uncertainties,environmental disturbances and input saturation.First,a virtual guidance control strategy is established on the basis of tracking error kinematics,which resolves the overall control system into two cascade subsystems.Then,a first-order sliding mode differentiator is introduced in the derivation to avoid tedious analytic calculation,and a Gaussian error function-based continuous differentiable symmetric saturation model is explored to tackle the issue of input saturation.Combined with backstepping design techniques,the neural network control method and an adaptive control approach are used to estimate composite items of the unknown uncertainty and approximation errors.Meanwhile,Lyapunov-based stability analysis guarantees that control error signals of the closed-loop system are uniformly ultimately bounded.Finally,simulation studies are conducted for the trajectory tracking of a moving target and a spiral line to validate the effectiveness of the proposed controller.展开更多
Three-dimensional speckle tracking echocardiography was employed to evaluate the changes of left ventricular systolic strain in 23 heart transplant recipients at 1 st, 3rd, 6th and 12th month after heart transplantati...Three-dimensional speckle tracking echocardiography was employed to evaluate the changes of left ventricular systolic strain in 23 heart transplant recipients at 1 st, 3rd, 6th and 12th month after heart transplantation, and 23 healthy subjects served as controls. The three-dimensional full-volume echocardiographic images of left ventricle were recorded and then were analyzed using EchoPAC software. The strain curves and peak systolic strain values for each segment and overall left ventricular wall were obtained. Left ventricular global peak longitudinal strain （GPSL）, global peak radial strain （GPSR）, global peak circumferential strain （GPSC） and global peak area strain （GPSA） were measured and then statistically analyzed. There were no significant differences in left ventricular ejection fraction （LVEF） and cardiac output （CO） between heart transplant recipients and controls. The GPSL in heart transplant recipients at 1st month after surgery was significantly lower than that in controls, but close to the normal value at 3rd month after surgery and later. The GPSC, GPSA and GPSR were significantly lower in heart transplant recipients at 1 st, 3rd, 6th and 12th month after surgery than those in controls. It is suggested that three-dimensional speckle tracking echocardiography can be used for monitoring changes of left ventricular systolic strains and evaluating left ventricular systolic function in cardiac allograft.展开更多
BACKGROUND Diabetic cardiomyopathy is considered as a chronic complication of diabetes mellitus(DM).Therefore,early detection of left ventricular systolic function(LVSF)damage in DM is essential.AIM To explore the use...BACKGROUND Diabetic cardiomyopathy is considered as a chronic complication of diabetes mellitus(DM).Therefore,early detection of left ventricular systolic function(LVSF)damage in DM is essential.AIM To explore the use of the three-dimensional speckle tracking technique(3D-STI)for measuring LVSF in DM patients via meta-analysis.METHODS The electronic databases were retrieved from the initial accessible time to 29 April 2023.The current study involved 9 studies,including 970 subjects.We carried out this meta-analysis to estimate myocardial function in DM compared with controls according to myocardial strain attained by 3D-STI.RESULTS Night articles including 970 subjects were included.No significant difference was detected in the left ventricular ejection fraction between the control and the diabetic group(P>0.05),while differences in global longitudinal strain,global circumferential strain,global radial strain,and global area strain were markedly different between the controls and DM patients(all P<0.05).CONCLUSION The 3D-STI could be applied to accurately measure early LVSF damage in patients with DM.展开更多
Background Two-dimensional speckle tracking imaging （2D-STI） and real-time three-dimensional echocardiography （RT-3DE） have more advantages in evaluating left ventricular （LV） systolic dyssynchrony than traditio...Background Two-dimensional speckle tracking imaging （2D-STI） and real-time three-dimensional echocardiography （RT-3DE） have more advantages in evaluating left ventricular （LV） systolic dyssynchrony than traditional echocardiographic techniques. The study aimed to evaluate LV dyssynchrony parameters by both 2D-STI and RT-3DE, and the correlation between these two techniques. Methods A total of 43 chronic heart failure （CHF） patients and 27 healthy volunteers were enrolled. There were 23 dyssynchrony parameters selected to evaluate left ventricular systolic synchronization, involving 15 from 2D-STI and 8 from RT-3DE. Results Few of the dyssynchrony parametersshowednegative correlations with LV ejection fraction （LVEF） in the CHF group. The difference between time to peak-systolic radial strain of the anteroseptal and posterior segments at the level of papillary muscles [AS-P（RS）] from 2D-STI showed positive correlations with parts of the parameters from RT-3DE （P 〈 0.05）. Conclusions LV systolic dysfunction does not correlate with dyssynchrony. Moreover, there is a weak association between 2D-STI and RT-3DE in assessment of left ventricular dyssynchrony.展开更多
Objective:To investigate the value of two-dimensional ultrasound speckle tracking(2D-STI)and three-dimensional ultrasound speckle tracking(3D-STI)in evaluating myocardial function in children with Kawasaki disease.Met...Objective:To investigate the value of two-dimensional ultrasound speckle tracking(2D-STI)and three-dimensional ultrasound speckle tracking(3D-STI)in evaluating myocardial function in children with Kawasaki disease.Methods 92 children with Kawasaki disease admitted to our hospital from February 2017 to February 2019 were retrospectively analyzed.50 children who underwent 3D-STI examination were taken as observation group and 42 children who underwent 2D-STI examination were taken as control group.The left ventricular systolic function index,storage time and analysis time of the image,the diameter of coronary artery,the strain difference of left ventricular basal segment,middle segment,apical segment and whole segment were observed.Results The levels of left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),left ventricular myocardial mass(LVMI)in the observation group were higher than those in the control group(P<0.05),but there was no statistical difference in left ventricular ejection fraction(LVEF)between the two groups(P>0.05).The storage time and analysis time of the image in the observation group were significantly lower than those in the control group(P<0.05).The left coronary artery(LCA)and right coronary artery(RCA)in the observation group were higher than those in the control group(P<0.05).There was no statistical difference between left anterior descending(LAD)in the two groups(P>0.05).The longitudinal peak systolic strain(LS),circumferential peak systolic strain(CS)and radial peak systolic strain(RS)in the observation group were higher than those in the control group(P<0.05).The global longitudinal peak strain(GLS),global circumferential peak strain(GCS)and global radial peak strain(GRS)in the observation group were higher than those in the control group(P<0.05).LS and CS in the middle segment of the observation group were higher than those in the control group(P<0.05).Conclusions Compared with 2D-STI,3D-STI can objectively and accurately reflect the myocardial function of children with Kawasaki disease.展开更多
Objective: To study the correlation between three-dimensional speckle tracking imaging (3D-STI) parameter global area strain (GAS) and the cardiotoxicity of chemotherapeutics in patients with lung cancer chemotherapy....Objective: To study the correlation between three-dimensional speckle tracking imaging (3D-STI) parameter global area strain (GAS) and the cardiotoxicity of chemotherapeutics in patients with lung cancer chemotherapy. Methods: Patients with lung cancer who underwent chemotherapy in the Second Affiliated Hospital of Xi'an Medical University between February 2016 and May 2017 were selected as the chemotherapy group, the healthy subjects who received physical examination during the same period were selected as the control group, the 3D-STI examination was performed and GAS was calculated;the serum was collected to determine the contents of cardiotoxicity markers as well as apoptosis and oxidative stress indexes, and the peripheral blood was collected to determine the expression of apoptosis and oxidative stress molecules. Results: GAS level, serum ALDH2 and CAT contents as well as peripheral blood Keap1 and Bcl-2 expression intensity of chemotherapy group were lower than those of control group whereas serum Copeptin, CK-MB, cTnI, cMyBP-c, sTWEAK, sFas, MDA and 8-isoPGF2α contents as well as peripheral blood Nrf-2, gp91phox, p22 phox and Caspase-3 expression intensity were significantly higher than those of control group;the GAS level in chemotherapy group was negatively correlated with serum Copeptin, CK-MB, cTnI, cMyBP-c, sTWEAK, sFas, MDA and 8-isoPGF2α contents as well as peripheral blood Nrf-2, gp91phox, p22 phox and Caspase-3 expression intensity, and positively correlated with serum ALDH2 and CAT contents as well as peripheral blood Keap1 and Bcl-2 expression intensity. Conclusion: The changes of 3D-STI parameter GAS in patients with lung cancer chemotherapy can reflect the degree of cardiotoxicity induced by oxidative stress and apoptosis.展开更多
Objective:To study the correlation between three-dimensional speckle tracking parameters and serum index changes during left ventricular remodeling in patients with coronary heart disease. Methods: Patients who were d...Objective:To study the correlation between three-dimensional speckle tracking parameters and serum index changes during left ventricular remodeling in patients with coronary heart disease. Methods: Patients who were diagnosed with coronary heart disease and angina pectoris in our hospital between March 2015 and May 2017 were selected as the CHD group of the study, and the healthy subjects who received medical examination in our hospital during the same period were taken as the control group;the three-dimensional speckle tracking parameters, peripheral blood signal molecule expression as well as serum cytokine and collagen metabolism index levels of the two groups were measured.Results: GLS and AGS levels in CHD group were significantly lower than those in control group whereas GCS and GRS levels were not significantly different from those in control group, and peripheral blood Notch1, Hes1, NF-κB and PKC expression intensity as well as serum sTWEAK, FGF23, TGF-β1, GDF15, sSema4D, CaN, MMP14, PINP and ICTP contents were significantly higher than those of control group;GLS and AGS levels in CHD group were negatively correlated with peripheral blood Notch1, Hes1, NF-κB and PKC expression intensity as well as serum sTWEAK, FGF23, TGF-β1, GDF15, sSema4D, CaN, MMP14, PINP and ICTP contents.Conclusions:The changes of three-dimensional speckle tracking parameters GLS and AGS in patients with coronary heart disease are closely related to the changes in signal pathway function, cytokine secretion and collagen metabolism during left ventricular remodeling.展开更多
Spherical robot has good static and dynamic stability, which provides it with strong viability in hostile environment, but the lack of effective control methods has hindered its application and development. This artic...Spherical robot has good static and dynamic stability, which provides it with strong viability in hostile environment, but the lack of effective control methods has hindered its application and development. This article deals with the dynamic trajectory tracking problem of the spherical robot BHQ-2 designed for unmanned environment exploration. The dynamic model of the spherical robot is established with a simplified Boltzmann-Hamel equation, based on which a trajectory tracking controller is designed by using the back-stepping method. The convergence of the controller is proved with the Lyapunov stability theory. Numerical simulations show that with the controller the robot can globally and asymptotically track desired trajectories, both linear and circular.展开更多
In order to design a suitable controller which can achieve accurate trajectory tracking and a good control performance, and guarantee the stability and robustness of a robot system due to external disturbances error a...In order to design a suitable controller which can achieve accurate trajectory tracking and a good control performance, and guarantee the stability and robustness of a robot system due to external disturbances error and internal parameter variations, an adaptive switching control strategy is proposed. The proposed scheme is designed under the condition of bounded distances and consists of an adaptive switching law and a PD controller. Based on the Lyapunov stability theory, it is proved that the proposed scheme can guarantee the tracking performance of the robotic manipulator and is adapted to varying unknown loads. Simulations are carded out on a two-link robotic manipulator, which illustrate the feasibility and validity of the proposed control scheme and the robustness for variational payloads.展开更多
基金the National Natural Science Founda-tion of China(No.51309133)。
文摘This paper addresses a three-dimensional(3D)trajectory tracking problem of underactuated autonomous underwater vehicles(AUVs)subjected to input saturation and external disturbances.The proposed controller can achieve practical convergence of tracking errors for general reference trajectories,including persistently exciting(PE)time varying trajectories and fixed points.At first,a modified error state formulation is introduced to tackle the situation that desired velocities do not satisfy PE condition.Then,on the basis of the backstepping technique and a Nussbaum-type even function,a saturated controller is designed so that the tracking errors can converge to a bounded neighborhood of the origin.The stability analysis based on Lyapunov theory shows that the tracking errors are globally ultimately uniformly bounded.Finally,some simulation results illustrate the effectiveness and robustness of the proposed control strategy.
基金supported by the National Natural Science Foundation of China(Nos.51775021,52302511)the Fundamental Research Funds for the Central Universities,China(Nos.501JCGG2024129003,501JCGG2024129005,501JCGG2024129006),the Fundamental Research Funds for the Central Universities,China(No.YWF-24-JC-09)the National Key Research and Development Program of China(No.2018YFC1506401)。
文摘This paper studies the tracking control problem for stratospheric airships with userspecified performance.Dealing with the infinite gain phenomenon in the prescribed-time stability,a new stability criterion with bounded gain is proposed by using a new time-varying scaling function.Moreover,a same-side performance function and a novel barrier Lyapunov function are incorporated into the control algorithm,which can compress the feasible domain of tracking error to minimize the overshoot and solve the difficult in tracking error not converging to zero simultaneously.The proposed scheme guarantees the airship capable of operating autonomously with satisfactory transient performance and tracking accuracy,where the performance parameters can be designed artificially and link to the physical process directly.Finally,the effectiveness of the proposed control scheme is verified by theoretical analysis and numerical simulation.
基金supported in part by the National Natural Science Foundation of China under Grants 61991404,62103093 and 62473089the Research Program of the Liaoning Liaohe Laboratory,China under Grant LLL23ZZ-05-01+5 种基金the Key Research and Development Program of Liaoning Province of China under Grant 2023JH26/10200011the 111 Project 2.0 of China under Grant B08015,the National Key Research and Development Program of China under Grant 2022YFB3305905the Xingliao Talent Program of Liaoning Province of China under Grant XLYC2203130the Natural Science Foundation of Liaoning Province of China under Grants 2024JH3/10200012 and 2023-MS-087the Open Research Project of the State Key Laboratory of Industrial Control Technology of China under Grant ICT2024B12the Fundamental Research Funds for the Central Universities of China under Grants N2108003 and N2424004.
文摘The problem of trajectory tracking for a class of differentially driven wheeled mobile robots(WMRs)under partial loss of the effectiveness of the actuated wheels is investigated in this paper.Such actuator faults may cause the loss of strong controllability of the WMR,such that the conventional fault-tolerant control strategies unworkable.In this paper,a new mixed-gain adaption scheme is devised,which is adopted to adapt the gain of a decoupling prescribed performance controller to adaptively compensate for the loss of the effectiveness of the actuators.Different from the existing gain adaption technique which depends on both the barrier functions and their partial derivatives,ours involves only the barrier functions.This yields a lower magnitude of the resulting control signals.Our controller accomplishes trajectory tracking of the WMR with the prescribed rate and accuracy even in the faulty case,and the control design relies on neither the information of the WMR dynamics and the actuator faults nor the tools for function approximation,parameter identification,and fault detection or estimation.The comparative simulation results justify the theoretical findings.
基金Supported by National Key R&D Program of China(Grant No.2018YFB0105102)Anhui Provincial Natural Science Foundation(Grant No.2208085QE153).
文摘Automated valet parking systems based on parking automated guided vehicles(P-AGVs)are effective for improving parking convenience and increasing parking density.The ability of P-AGVs to move towards any position and attain any orientation simultaneously due to their mecanum wheels makes it convenient to transport vehicles in a parking lot.In this study,a nonlinear disturbance observer-based sliding mode controller for the trajectory tracking problem of a P-AGV is proposed.The kinematic and dynamic models for a P-AGV tracking trajectory are first analyzed in sequence and the influences of disturbing forces considered.Subsequently,a nonlinear disturbance observer(NDO)is designed to estimate the disturbing forces and torques generated by the caster wheels.Based on the designed NDO,a robust nonsingular terminal sliding-mode(NTSM)controller is used to track reference trajectories.The stabilities of the NDO and NDO-NTSM control systems are theoretically verified using their Lyapunov functions.Finally,simulations and experiments are performed to verify the effectiveness of the proposed control scheme.The experimental results show that the proposed NDO-NTSM controller can improve the trajectory tracking stability by 42-68%compared to a traditional NTSM controller.The NDO-based sliding mode controller for trajectory tracking proposed in this study can effectively reduce the impact of disturbances on trajectory tracking accuracy.
基金supported by the Natural Science Foundation of Shandong Province(Grant No.ZR2020MA092)the Innovation Project for Graduate Students of Ludong University(Grant No.IPGS2024-048).
文摘The diffusion trajectory of a Brownian particle passing over the saddle point of a two-dimensional quadratic potential energy surface is tracked in detail according to the deep learning strategies.Generative adversarial networks(GANs)emanating in the category of machine learning(ML)frameworks are used to generate and assess the rationality of the data.While their optimization is based on the long short-term memory(LSTM)strategies.In addition to drawing a heat map,the optimal path of two-dimensional(2D)diffusion is simultaneously demonstrated in a stereoscopic space.The results of our simulation are completely consistent with the previous theoretical predictions.
基金support of the National Natural Science Foundation of China(No.12032012)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘To achieve high-precision trajectory following during helicopter maneuver tasks and reduce the disruptive influences of unknown variabilities,this study introduces a cascaded-loop helicopter trajectory tracking controller,whose parameters are set using an Ant Colony OptimizationSlime Mould Algorithm(ACO-SMA).Initially,a nonlinear flight dynamics model of the helicopter is constructed.Observer gain functions and nonlinear feedback from a vibrational suppression function to improve the tracking performance of the controller,addressing issues in disturbance estimation and compensation of the Active Disturbance Rejection Control(ADRC).Simultaneously,a cascaded loop system,comprising an internal attitude loop and an external position loop,is created,and the ant colony-slime mold hybrid algorithm optimizes the system parameters of the trajectory tracking controller.Finally,helicopter trajectory tracking simulation experiments are conducted,including spiral ascending and“8”shape climbing maneuvers.The findings indicate that the ADRC employed for helicopter trajectory tracking exhibits outstanding performance in rejecting disturbances caused by gusts and accurately tracking trajectories.The trajectory tracking controller,whose parameters are optimized by the ACO-SMA,shows higher tracking precision compared to the conventional PID and ADRC,thereby substantially improving the precision of maneuver tasks.
基金supported by Liaoning Provincial Department of Education 2023 Basic Research Projects for Universities and Colleges(Grant No.JYTQN2023131)Liaoning Provincial Science and Technology Program:Cooperative Control and Recognition of Unmanned Vessels for Fishing Vessel Operation Scenarios(Grant No.600024003)Liaoning Provincial Department of Education Scientific Research Funding Project(Grant No.LJKZ0726).
文摘This paper proposes a separated trajectory tracking controller for fishing ships at sea state level 6 to solve the trajectory tracking problem of a fishing ship in a 6-level sea state,and to adapt to different working environments and safety requirements.The nonlinear feedback method is used to improve the closed-loop gain shaping algorithm.By introducing the sine function,the problem of excessive control energy of the system can be effectively solved.Moreover,an integral separation design is used to solve the influence of the integral term in conventional PID controllers on the transient performance of the system.In this paper,a common 32.98 m large fiberglass reinforced plastic(FRP)trawler is adopted for simulation research at the winds scale of Beaufort No.7.The results show that the track error is smaller than 3.5 m.The method is safe,feasible,concise and effective and has popularization value in the direction of fishing ship trajectory tracking control.This method can be used to improve the level of informatization and intelligence of fishing ships.
基金Supported by National Natural Science Foundation of China(Grant Nos.52405112,U24A20199)the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20240973).
文摘Four-Wheel Independent Steering(4WIS)Vehicles can independently control the angle of each wheel,demonstrating superior trajectory tracking performance under normal conditions.However,on intermittent icy and snowy roads,the presence of time-varying adhesion coefficients,time-varying cornering stiffness,and the irregularities due to ice and snow accumulation introduce multiple uncertainties into the steering system,significantly degrading the trajectory tracking performance of 4WIS vehicles.In response,this paper proposes a robust Tube Model Predictive Control(Tube-MPC)trajectory tracking control method for 4WIS.In this method,a Bi-directional Long Short-Term Memory neural network is established for online estimation of tire cornering stiffness under different road adhesion coefficients,providing accurate estimation of time-varying cornering stiffness for each wheel to mitigate the uncertainties of time-varying adhesion coefficients and cornering stiffness.Additionally,considering the road irregularities caused by snow accumulation on intermittent icy and snowy roads,a trajectory tracking controller that integrates Tube-MPC and robust Sliding Mode Control is proposed.The nominal MPC model,developed from the estimated tire cornering stiffness,utilizes the sliding surface and the optimal auxiliary control unit law for the tube is derived from the reaching law in Tube-MPC,aiming to minimize the trajectory tracking error while enhancing the controller’s robustness against road uncertainties.The experiments show that the proposed method outperforms the Tube-MPC algorithm in terms of trajectory accuracy and robustness.This method demonstrates excellent trajectory tracking accuracy under intermittent icy and snowy road conditions,and it lays a theoretical foundation for future studies on vehicle stability and trajectory tracking under such road conditions.
文摘A hybrid control strategy integrating proportional derivative(PD)and the H-infinity control methodology is proposed for a serial two-link robotic manipulator with the goal of improving the tracking performance of the robot arm.The H-infinity controller has the ability to achieve a high performance and robustness in the presence of disturbances and uncertainties,while the PD controller is effective in stabilizing the manipulator.Simulation results using Matlab and Simulink show that the proposed hybrid controller,which integrates the advantages of both PD and H-infinity controllers,has the lowest rise time for the second link,the lowest settling time for the two links,the lowest peak time for both links,and the fastest decay of the error response.In addition,the hybrid control scheme also has the lowest mean square error value,with a 53.3%improvement over the H-infinity controller and a 91.8%improvement over the PD controller,indicating an improved trajectory tracking performance when compared with pure PD and pure H-infinity controllers,respectively.It was also found that the hybrid controller has the lowest integral absolute error,integral square error,integral time absolute error,and integral time square error for the second link,while the error values for the first link are satisfactory,showing a superior performance of the hybrid controller above the PD and H-infinity controllers,respectively.
基金Supported by the Natural Science Foundation of Liaoning ProvinceChina(2013023010)
文摘Objective To evaluate left atrial function in essential hypertension patients with different patterns of left ventricular geometric models by real-time three-dimensional echocardiography （RT-3DE） and left atrial tracking （EAT）.
文摘The Kuroshio Extension(KE)is one of the most eddy-energetic regions in the global ocean.However,most mesoscale eddy studies in the region are focused on surface eddies and the structure and characteristics of three-dimensional(3-D)eddies require additional research.In this study,we proposed a 3-D eddy identification and tracking algorithm based on pressure anomalies,similar to sea level anomalies(SLAs)for surface eddy identification.We applied this scheme to a 5-year(2008-2012)high-resolution numerical product to develop a 3-D eddy dataset in the KE.The reliability of the numerical product was verified by the 5-year temperature/salinity hydrological characteristics and surface eddy distribution.According to the 3-D eddy tracking dataset,the number of eddies decreased dramatically as the eddy existence-time increased and more anticyclonic eddies(AEs)had an existence-time longer than 1 week than cyclonic eddies(CEs).We presented daily variations in the 3-D structure of two 3-D eddy-tracking trajectories that exhibit a certain jump in depth and a shift toward the west and equator.In addition to the bowl,lens,and cone eddies that have been discovered by previous researchers,we found that there is a cylindrical eddy,and its eddy radii are almost consistent across all layers.CEs cause significant negative temperature anomalies,“negative-positive”salinity anomalies,and sinking current fields in the KE region,while AEs cause positive temperature anomalies,“positive-negative”salinity anomalies,and upward current fields.The four types of eddies have different effects on the temperature/salinity anomalies and current field distribution which are related to their structure.
基金Project(51979116)supported by the National Natural Science Foundation of ChinaProject(2018KFYYXJJ012,2018JYCXJJ045)supported by the Fundamental Research Funds for the Central Universities,China+1 种基金Project(YT19201702)supported by the Innovation Foundation of Maritime Defense Technologies Innovation Center,ChinaProject supported by the HUST Interdisciplinary Innovation Team Project,China。
文摘This paper addresses the problem of three-dimensional trajectory tracking control for underactuated autonomous underwater vehicles in the presence of parametric uncertainties,environmental disturbances and input saturation.First,a virtual guidance control strategy is established on the basis of tracking error kinematics,which resolves the overall control system into two cascade subsystems.Then,a first-order sliding mode differentiator is introduced in the derivation to avoid tedious analytic calculation,and a Gaussian error function-based continuous differentiable symmetric saturation model is explored to tackle the issue of input saturation.Combined with backstepping design techniques,the neural network control method and an adaptive control approach are used to estimate composite items of the unknown uncertainty and approximation errors.Meanwhile,Lyapunov-based stability analysis guarantees that control error signals of the closed-loop system are uniformly ultimately bounded.Finally,simulation studies are conducted for the trajectory tracking of a moving target and a spiral line to validate the effectiveness of the proposed controller.
基金supported by Innovation Research Fund of Huazhong University of Science and Technology,China(No.2012QN183)
文摘Three-dimensional speckle tracking echocardiography was employed to evaluate the changes of left ventricular systolic strain in 23 heart transplant recipients at 1 st, 3rd, 6th and 12th month after heart transplantation, and 23 healthy subjects served as controls. The three-dimensional full-volume echocardiographic images of left ventricle were recorded and then were analyzed using EchoPAC software. The strain curves and peak systolic strain values for each segment and overall left ventricular wall were obtained. Left ventricular global peak longitudinal strain （GPSL）, global peak radial strain （GPSR）, global peak circumferential strain （GPSC） and global peak area strain （GPSA） were measured and then statistically analyzed. There were no significant differences in left ventricular ejection fraction （LVEF） and cardiac output （CO） between heart transplant recipients and controls. The GPSL in heart transplant recipients at 1st month after surgery was significantly lower than that in controls, but close to the normal value at 3rd month after surgery and later. The GPSC, GPSA and GPSR were significantly lower in heart transplant recipients at 1 st, 3rd, 6th and 12th month after surgery than those in controls. It is suggested that three-dimensional speckle tracking echocardiography can be used for monitoring changes of left ventricular systolic strains and evaluating left ventricular systolic function in cardiac allograft.
文摘BACKGROUND Diabetic cardiomyopathy is considered as a chronic complication of diabetes mellitus(DM).Therefore,early detection of left ventricular systolic function(LVSF)damage in DM is essential.AIM To explore the use of the three-dimensional speckle tracking technique(3D-STI)for measuring LVSF in DM patients via meta-analysis.METHODS The electronic databases were retrieved from the initial accessible time to 29 April 2023.The current study involved 9 studies,including 970 subjects.We carried out this meta-analysis to estimate myocardial function in DM compared with controls according to myocardial strain attained by 3D-STI.RESULTS Night articles including 970 subjects were included.No significant difference was detected in the left ventricular ejection fraction between the control and the diabetic group(P>0.05),while differences in global longitudinal strain,global circumferential strain,global radial strain,and global area strain were markedly different between the controls and DM patients(all P<0.05).CONCLUSION The 3D-STI could be applied to accurately measure early LVSF damage in patients with DM.
文摘Background Two-dimensional speckle tracking imaging （2D-STI） and real-time three-dimensional echocardiography （RT-3DE） have more advantages in evaluating left ventricular （LV） systolic dyssynchrony than traditional echocardiographic techniques. The study aimed to evaluate LV dyssynchrony parameters by both 2D-STI and RT-3DE, and the correlation between these two techniques. Methods A total of 43 chronic heart failure （CHF） patients and 27 healthy volunteers were enrolled. There were 23 dyssynchrony parameters selected to evaluate left ventricular systolic synchronization, involving 15 from 2D-STI and 8 from RT-3DE. Results Few of the dyssynchrony parametersshowednegative correlations with LV ejection fraction （LVEF） in the CHF group. The difference between time to peak-systolic radial strain of the anteroseptal and posterior segments at the level of papillary muscles [AS-P（RS）] from 2D-STI showed positive correlations with parts of the parameters from RT-3DE （P 〈 0.05）. Conclusions LV systolic dysfunction does not correlate with dyssynchrony. Moreover, there is a weak association between 2D-STI and RT-3DE in assessment of left ventricular dyssynchrony.
基金Shaanxi key research and development plan(No.2019SF-211).
文摘Objective:To investigate the value of two-dimensional ultrasound speckle tracking(2D-STI)and three-dimensional ultrasound speckle tracking(3D-STI)in evaluating myocardial function in children with Kawasaki disease.Methods 92 children with Kawasaki disease admitted to our hospital from February 2017 to February 2019 were retrospectively analyzed.50 children who underwent 3D-STI examination were taken as observation group and 42 children who underwent 2D-STI examination were taken as control group.The left ventricular systolic function index,storage time and analysis time of the image,the diameter of coronary artery,the strain difference of left ventricular basal segment,middle segment,apical segment and whole segment were observed.Results The levels of left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),left ventricular myocardial mass(LVMI)in the observation group were higher than those in the control group(P<0.05),but there was no statistical difference in left ventricular ejection fraction(LVEF)between the two groups(P>0.05).The storage time and analysis time of the image in the observation group were significantly lower than those in the control group(P<0.05).The left coronary artery(LCA)and right coronary artery(RCA)in the observation group were higher than those in the control group(P<0.05).There was no statistical difference between left anterior descending(LAD)in the two groups(P>0.05).The longitudinal peak systolic strain(LS),circumferential peak systolic strain(CS)and radial peak systolic strain(RS)in the observation group were higher than those in the control group(P<0.05).The global longitudinal peak strain(GLS),global circumferential peak strain(GCS)and global radial peak strain(GRS)in the observation group were higher than those in the control group(P<0.05).LS and CS in the middle segment of the observation group were higher than those in the control group(P<0.05).Conclusions Compared with 2D-STI,3D-STI can objectively and accurately reflect the myocardial function of children with Kawasaki disease.
文摘Objective: To study the correlation between three-dimensional speckle tracking imaging (3D-STI) parameter global area strain (GAS) and the cardiotoxicity of chemotherapeutics in patients with lung cancer chemotherapy. Methods: Patients with lung cancer who underwent chemotherapy in the Second Affiliated Hospital of Xi'an Medical University between February 2016 and May 2017 were selected as the chemotherapy group, the healthy subjects who received physical examination during the same period were selected as the control group, the 3D-STI examination was performed and GAS was calculated;the serum was collected to determine the contents of cardiotoxicity markers as well as apoptosis and oxidative stress indexes, and the peripheral blood was collected to determine the expression of apoptosis and oxidative stress molecules. Results: GAS level, serum ALDH2 and CAT contents as well as peripheral blood Keap1 and Bcl-2 expression intensity of chemotherapy group were lower than those of control group whereas serum Copeptin, CK-MB, cTnI, cMyBP-c, sTWEAK, sFas, MDA and 8-isoPGF2α contents as well as peripheral blood Nrf-2, gp91phox, p22 phox and Caspase-3 expression intensity were significantly higher than those of control group;the GAS level in chemotherapy group was negatively correlated with serum Copeptin, CK-MB, cTnI, cMyBP-c, sTWEAK, sFas, MDA and 8-isoPGF2α contents as well as peripheral blood Nrf-2, gp91phox, p22 phox and Caspase-3 expression intensity, and positively correlated with serum ALDH2 and CAT contents as well as peripheral blood Keap1 and Bcl-2 expression intensity. Conclusion: The changes of 3D-STI parameter GAS in patients with lung cancer chemotherapy can reflect the degree of cardiotoxicity induced by oxidative stress and apoptosis.
文摘Objective:To study the correlation between three-dimensional speckle tracking parameters and serum index changes during left ventricular remodeling in patients with coronary heart disease. Methods: Patients who were diagnosed with coronary heart disease and angina pectoris in our hospital between March 2015 and May 2017 were selected as the CHD group of the study, and the healthy subjects who received medical examination in our hospital during the same period were taken as the control group;the three-dimensional speckle tracking parameters, peripheral blood signal molecule expression as well as serum cytokine and collagen metabolism index levels of the two groups were measured.Results: GLS and AGS levels in CHD group were significantly lower than those in control group whereas GCS and GRS levels were not significantly different from those in control group, and peripheral blood Notch1, Hes1, NF-κB and PKC expression intensity as well as serum sTWEAK, FGF23, TGF-β1, GDF15, sSema4D, CaN, MMP14, PINP and ICTP contents were significantly higher than those of control group;GLS and AGS levels in CHD group were negatively correlated with peripheral blood Notch1, Hes1, NF-κB and PKC expression intensity as well as serum sTWEAK, FGF23, TGF-β1, GDF15, sSema4D, CaN, MMP14, PINP and ICTP contents.Conclusions:The changes of three-dimensional speckle tracking parameters GLS and AGS in patients with coronary heart disease are closely related to the changes in signal pathway function, cytokine secretion and collagen metabolism during left ventricular remodeling.
基金National Natural Science Foundation of China (50705003)National High Technology Research and Development Program of China (2007AA04Z252).
文摘Spherical robot has good static and dynamic stability, which provides it with strong viability in hostile environment, but the lack of effective control methods has hindered its application and development. This article deals with the dynamic trajectory tracking problem of the spherical robot BHQ-2 designed for unmanned environment exploration. The dynamic model of the spherical robot is established with a simplified Boltzmann-Hamel equation, based on which a trajectory tracking controller is designed by using the back-stepping method. The convergence of the controller is proved with the Lyapunov stability theory. Numerical simulations show that with the controller the robot can globally and asymptotically track desired trajectories, both linear and circular.
基金The National Natural Science Foundation of China(No.61273119,61374038,61473079)
文摘In order to design a suitable controller which can achieve accurate trajectory tracking and a good control performance, and guarantee the stability and robustness of a robot system due to external disturbances error and internal parameter variations, an adaptive switching control strategy is proposed. The proposed scheme is designed under the condition of bounded distances and consists of an adaptive switching law and a PD controller. Based on the Lyapunov stability theory, it is proved that the proposed scheme can guarantee the tracking performance of the robotic manipulator and is adapted to varying unknown loads. Simulations are carded out on a two-link robotic manipulator, which illustrate the feasibility and validity of the proposed control scheme and the robustness for variational payloads.
