This paper focuses on the dynamic tracking control of ammunition manipulator system. A standard state space model for the ammunition manipulator electro-hydraulic system(AMEHS) with inherent nonlinearities and uncerta...This paper focuses on the dynamic tracking control of ammunition manipulator system. A standard state space model for the ammunition manipulator electro-hydraulic system(AMEHS) with inherent nonlinearities and uncertainties considered was established. To simultaneously suppress the violation of tracking error constraints and the complexity of differential explosion, a barrier Lyapunov functionsbased dynamic surface control(BLF-DSC) method was proposed for the position tracking control of the ammunition manipulator. Theoretical analysis prove the stability of the closed-loop overall system and the tracking error converges to a prescribed neighborhood asymptotically. The effectiveness and dynamic tracking performance of the proposed control strategy is validated via simulation and experimental results.展开更多
This paper presents a constructive design of new controllers that force underactuated ships under constant or slow time-varying sea loads to asymptotically track a parameterized reference path, that guarantees the dis...This paper presents a constructive design of new controllers that force underactuated ships under constant or slow time-varying sea loads to asymptotically track a parameterized reference path, that guarantees the distance from the ship to the reference path always be within a specified value. The control design is based on a global exponential disturbance observer, a transformation of the ship dynamics to an almost spherical form, an interpretation of the tracking errors in an earth-fixed frame, an introduction of dynamic variables to compensate for relaxation of the reference path generation, p-times differentiable step functions, and backstepping and Lyapunov＇s direct methods. The effectiveness of the proposed results is illustrated through simulations.展开更多
In this article,a fixed-time tracking control strategy is proposed for a quadrotor UAV(QUAV)with external disturbance and asymmetric output error constraints.Firstly,a dynamic model of the QUAV is transformed into a s...In this article,a fixed-time tracking control strategy is proposed for a quadrotor UAV(QUAV)with external disturbance and asymmetric output error constraints.Firstly,a dynamic model of the QUAV is transformed into a strict feedback system with external disturbance,and it is decoupled into attitude subsystem and position subsystem for simplifying controller design.Secondly,an asymmetric tangent barrier Lyapunov function(ATBLF)is applied to solve the tracking error constraints problem,and a fixed-time control law is designed.Meanwhile,a fixed-time disturbance observer(FTDO)is designed to cope with external disturbance.Then,it is proved that the designed controller guarantees the tracking error remains within the constraint ranges and converges to zero in fixed-time by Lyapunov stability theory.Finally,the effectiveness of the proposed control scheme is verified by numerical simulations.展开更多
This paper focuses on the trajectory tracking control problem of unmanned underwater vehicles(UUVs)with unknown dead-zone inputs.The primary objective is to design an adaptive trajectory tracking error constraint cont...This paper focuses on the trajectory tracking control problem of unmanned underwater vehicles(UUVs)with unknown dead-zone inputs.The primary objective is to design an adaptive trajectory tracking error constraint controller using the fully actuated systems(FAs)approach to enable UUVs to asymptotically track target signals.Firstly,a novel error constraint fully actuated systems(ECFAs)approach is proposed by incorporating the tracking error dependent normalized function and barrier function along with time-varying scaling.Secondly,in order to deal with the model uncertainties of the UUVs,adaptive radial basis function neural networks(RBFNNs)is combined with the ECFAs approach.Then,a positive time-varying integral function is introduced to completely eliminate the effect of the residual effect caused by unknown dead-zone inputs,and it is proved that the trajectory tracking error converges to zero asymptotically based on the Lyapunov functions.Finally,the simulation results demonstrate the effectiveness of the designed adaptive controller.展开更多
Temperature （T） and salinity （S） profiles from conductivity-temperature-depth data collected during the Northern South China Sea Open Cruise from August 16 to September 13, 2008 are assimilated using Ensemble Kalm...Temperature （T） and salinity （S） profiles from conductivity-temperature-depth data collected during the Northern South China Sea Open Cruise from August 16 to September 13, 2008 are assimilated using Ensemble Kalman Filter （EnKF）. An adaptive observational error strategy is used to prevent filter from diverging. In the meantime, aiming at the limited improvement in some sites caused by the T and S biases in the model, a T-S constraint scheme is adopted to improve the assimilation performance, where T and S are separately updated at these locations. Validation is performed by comparing assimilated outputs with independent in situ data （satellite remote sensing sea level anomaly （SLA）, the OSCAR velocity product and shipboard ADCP）. The results show that the new EnKF assimilation scheme can significantly reduce the root mean square error （RMSE） of oceanic T and S compared with the control run and traditional EnKF. The system can also improve the simulation of circulations and SLA.展开更多
实时动态差分(real time kinematic,RTK)定位技术因其成本低、实时性强等优点,已成为实时位移监测领域的重要技术手段.然而,随着跨海大桥、海上平台等远距离基础设施对高精度实时位移监测需求不断增长,常规RTK技术在长距离作业中,因测...实时动态差分(real time kinematic,RTK)定位技术因其成本低、实时性强等优点,已成为实时位移监测领域的重要技术手段.然而,随着跨海大桥、海上平台等远距离基础设施对高精度实时位移监测需求不断增长,常规RTK技术在长距离作业中,因测站间距离增加导致大气误差(对流层和电离层延迟)的空间相关性降低,差分后残余大气误差难以充分消除,严重影响模糊度的收敛从而影响定位精度.针对这一问题,提出一种大气误差附加约束的长距离RTK定位方法:1)将经先验模型改正并进行差分后残余的对流层和电离层延迟参数化并纳入估计模型,针对残余误差分别建立先验约束:对流层残差基于台站间高差和测站距离构建先验方差,更全面地刻画长距离条件下对流层残差的不确定性;电离层残差结合纬度相关性构建先验方差,实现对定位参数解算过程的稳健约束;2)考虑大气误差的时变特性,采用随机游走过程对对流层和电离层参数进行动态估计,电离层活动变化大,随机游走噪声建模考虑基线长度和卫星高度角变化,使动态估计更符合实际情况.基于国际GNSS服务组织(International GNSS Service,IGS)测站和海上平台实测数据开展试验,结果表明:相较于常规RTK方法,所提方法在不同的观测环境下均有效缩短了收敛时间和模糊度首次固定时间,显著提升了模糊度固定率,同时在水平和垂向定位精度上取得明显改善.展开更多
This article focuses on the high accuracy quasi-synchronous control issue of multiple electrohydraulic systems(MEHS).In order to overcome the negative effects of parameter uncertainty and external load interference of...This article focuses on the high accuracy quasi-synchronous control issue of multiple electrohydraulic systems(MEHS).In order to overcome the negative effects of parameter uncertainty and external load interference of MEHS,a kind of finite-time disturbance observer(FTDO)via terminal sliding mode method is constructed based on the MEHS model to achieve fast and accuracy estimation and compensation ability.To avoid the differential explosion in backstepping iteration,the dynamic surface control is used in this paper to guarantee the follower electrohydraulic nodes synchronize to the leader motion with a better performance.Furthermore,a timevarying barrier Lyapunov function(tvBLF)is adopted during the controller design process to constraint the output tracking error of MEHS in a prescribed performance with time-varying exponential function.As the initial state condition is relax by tvBLF,the input saturation law is also adopted during the controller design process in this paper to restrain the surges of input signals,which can avoid the circuit and mechanical structure damage caused by the volatile input signal.An MEHS experimental bench is constructed to verify the effectiveness of the theoretical conclusions proposed in this paper and the advantages of the proposed conclusions in this paper are illustrated by a series of contradistinctive experimental results.展开更多
Laser tracking system （LTS） is an advanced device for large size 3D coordinates measuring with the advantages of broad range, high speed and high accuracy. However, its measuring accuracy is highly dominated by the ...Laser tracking system （LTS） is an advanced device for large size 3D coordinates measuring with the advantages of broad range, high speed and high accuracy. However, its measuring accuracy is highly dominated by the geometric errors of the tracking mirror mechanism. Proper calibration of LTS is essential prior to the use of it for metrology. A kinematics model that describes not only the motion but also the geometric variations of LTS is developed. Through error analysis of the proposed model, it is claimed that gimbals axis misalignments and tracking mirror center off-set are the key contributors to measuring errors of LTS. A self-calibration method is presented of calibrating LTS with planar constraints. Various calibration strategies utilizing single-plane and multiple-plane constraints are proposed for different situations. For each calibration strategy, issues about the error parameter estimation of LTS are exploded to find out in which conditions these parameters can be uniquely estimated. Moreover, these conditions reveal the applicability of the planar constraints to LTS self-calibration. Intensive studies have been made to check validity of the theoretical results. The results show that the measuring accuracy of LTS has increased by 5 times since this technique for calibration is used.展开更多
离线强化学习旨在仅通过使用预先收集的离线数据集进行策略的有效学习,从而减少与环境直接交互所带来的高昂成本。然而,由于缺少环境对智能体行为的交互反馈,从离线数据集中学习到的策略可能会遇到数据分布偏移的问题,进而导致外推误差...离线强化学习旨在仅通过使用预先收集的离线数据集进行策略的有效学习,从而减少与环境直接交互所带来的高昂成本。然而,由于缺少环境对智能体行为的交互反馈,从离线数据集中学习到的策略可能会遇到数据分布偏移的问题,进而导致外推误差的不断加剧。当前方法多采用策略约束或模仿学习方法来缓解这一问题,但其学习到的策略通常较为保守。针对上述难题,提出一种基于自适应分位数的方法。具体而言,该方法在双Q估计的基础上进一步利用双Q的估计差值大小对分布外未知动作的价值高估情况进行评估,同时结合分位数思想自适应调整分位数来校正过估计偏差。此外,构建分位数优势函数作为策略约束项权重以平衡智能体对数据集的探索和模仿,从而缓解策略学习的保守性。最后在D4RL(datasets for deep data-driven reinforcement learning)数据集上验证算法的有效性,该算法在多个任务数据集上表现优异,同时展现出在不同场景应用下的广泛潜力。展开更多
基金the National Natural Science Foundation of China, ChinaGrant ID: 11472137。
文摘This paper focuses on the dynamic tracking control of ammunition manipulator system. A standard state space model for the ammunition manipulator electro-hydraulic system(AMEHS) with inherent nonlinearities and uncertainties considered was established. To simultaneously suppress the violation of tracking error constraints and the complexity of differential explosion, a barrier Lyapunov functionsbased dynamic surface control(BLF-DSC) method was proposed for the position tracking control of the ammunition manipulator. Theoretical analysis prove the stability of the closed-loop overall system and the tracking error converges to a prescribed neighborhood asymptotically. The effectiveness and dynamic tracking performance of the proposed control strategy is validated via simulation and experimental results.
基金Supported in Part by the Australian Research Council Under Grant No.DP0988424
文摘This paper presents a constructive design of new controllers that force underactuated ships under constant or slow time-varying sea loads to asymptotically track a parameterized reference path, that guarantees the distance from the ship to the reference path always be within a specified value. The control design is based on a global exponential disturbance observer, a transformation of the ship dynamics to an almost spherical form, an interpretation of the tracking errors in an earth-fixed frame, an introduction of dynamic variables to compensate for relaxation of the reference path generation, p-times differentiable step functions, and backstepping and Lyapunov＇s direct methods. The effectiveness of the proposed results is illustrated through simulations.
基金supported by Science and Technology Project of Hebei Education Department under Grant No.ZD2022012the Natural Science Foundation of Hebei Province under Grant Nos.F2020203105 and F2022203085+1 种基金the National Natural Science Foundation of China under Grant No.62073234Central Government Guided Local Science and Technology Development Fund Project under Grant No.236Z1601G。
文摘In this article,a fixed-time tracking control strategy is proposed for a quadrotor UAV(QUAV)with external disturbance and asymmetric output error constraints.Firstly,a dynamic model of the QUAV is transformed into a strict feedback system with external disturbance,and it is decoupled into attitude subsystem and position subsystem for simplifying controller design.Secondly,an asymmetric tangent barrier Lyapunov function(ATBLF)is applied to solve the tracking error constraints problem,and a fixed-time control law is designed.Meanwhile,a fixed-time disturbance observer(FTDO)is designed to cope with external disturbance.Then,it is proved that the designed controller guarantees the tracking error remains within the constraint ranges and converges to zero in fixed-time by Lyapunov stability theory.Finally,the effectiveness of the proposed control scheme is verified by numerical simulations.
基金supported in part by the National Natural Science Foundation of China under Grant Nos.62273297,62103353,61825304,and 6182500417in part by the Innovative Research Groups of the Natural Science Foundation of Hebei Province under Grant No.E2020203174+2 种基金in part by Hebei Innovation Capability Improvement Plan Project under Grant No.22567619Hin part by Youth Top Talent Project of Hebei Province under Grant No.HY2024050021in part by Post-graduate Innovation Fund Project of Hebei Province under Grant No.CXZZSS2023042。
文摘This paper focuses on the trajectory tracking control problem of unmanned underwater vehicles(UUVs)with unknown dead-zone inputs.The primary objective is to design an adaptive trajectory tracking error constraint controller using the fully actuated systems(FAs)approach to enable UUVs to asymptotically track target signals.Firstly,a novel error constraint fully actuated systems(ECFAs)approach is proposed by incorporating the tracking error dependent normalized function and barrier function along with time-varying scaling.Secondly,in order to deal with the model uncertainties of the UUVs,adaptive radial basis function neural networks(RBFNNs)is combined with the ECFAs approach.Then,a positive time-varying integral function is introduced to completely eliminate the effect of the residual effect caused by unknown dead-zone inputs,and it is proved that the trajectory tracking error converges to zero asymptotically based on the Lyapunov functions.Finally,the simulation results demonstrate the effectiveness of the designed adaptive controller.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA10010405the Promgram of Guangdong Province Department of Science and Technology No.2012A032100004+1 种基金the National Natural Science Foundation of China under contract Nos 41476012,41521005 and 41406131the Knowledge Innovation Program of the Chinese Academy of Sciences under contract Nos SQ201001 and SQ201205
文摘Temperature （T） and salinity （S） profiles from conductivity-temperature-depth data collected during the Northern South China Sea Open Cruise from August 16 to September 13, 2008 are assimilated using Ensemble Kalman Filter （EnKF）. An adaptive observational error strategy is used to prevent filter from diverging. In the meantime, aiming at the limited improvement in some sites caused by the T and S biases in the model, a T-S constraint scheme is adopted to improve the assimilation performance, where T and S are separately updated at these locations. Validation is performed by comparing assimilated outputs with independent in situ data （satellite remote sensing sea level anomaly （SLA）, the OSCAR velocity product and shipboard ADCP）. The results show that the new EnKF assimilation scheme can significantly reduce the root mean square error （RMSE） of oceanic T and S compared with the control run and traditional EnKF. The system can also improve the simulation of circulations and SLA.
文摘实时动态差分(real time kinematic,RTK)定位技术因其成本低、实时性强等优点,已成为实时位移监测领域的重要技术手段.然而,随着跨海大桥、海上平台等远距离基础设施对高精度实时位移监测需求不断增长,常规RTK技术在长距离作业中,因测站间距离增加导致大气误差(对流层和电离层延迟)的空间相关性降低,差分后残余大气误差难以充分消除,严重影响模糊度的收敛从而影响定位精度.针对这一问题,提出一种大气误差附加约束的长距离RTK定位方法:1)将经先验模型改正并进行差分后残余的对流层和电离层延迟参数化并纳入估计模型,针对残余误差分别建立先验约束:对流层残差基于台站间高差和测站距离构建先验方差,更全面地刻画长距离条件下对流层残差的不确定性;电离层残差结合纬度相关性构建先验方差,实现对定位参数解算过程的稳健约束;2)考虑大气误差的时变特性,采用随机游走过程对对流层和电离层参数进行动态估计,电离层活动变化大,随机游走噪声建模考虑基线长度和卫星高度角变化,使动态估计更符合实际情况.基于国际GNSS服务组织(International GNSS Service,IGS)测站和海上平台实测数据开展试验,结果表明:相较于常规RTK方法,所提方法在不同的观测环境下均有效缩短了收敛时间和模糊度首次固定时间,显著提升了模糊度固定率,同时在水平和垂向定位精度上取得明显改善.
基金This study was co-supported by the National Natural Science Foundation of China(Nos.52175046,51975024,and 12072068)Sichuan Science and Technology Program(Nos.2022JDRC0018 and 2022YFG0341).
文摘This article focuses on the high accuracy quasi-synchronous control issue of multiple electrohydraulic systems(MEHS).In order to overcome the negative effects of parameter uncertainty and external load interference of MEHS,a kind of finite-time disturbance observer(FTDO)via terminal sliding mode method is constructed based on the MEHS model to achieve fast and accuracy estimation and compensation ability.To avoid the differential explosion in backstepping iteration,the dynamic surface control is used in this paper to guarantee the follower electrohydraulic nodes synchronize to the leader motion with a better performance.Furthermore,a timevarying barrier Lyapunov function(tvBLF)is adopted during the controller design process to constraint the output tracking error of MEHS in a prescribed performance with time-varying exponential function.As the initial state condition is relax by tvBLF,the input saturation law is also adopted during the controller design process in this paper to restrain the surges of input signals,which can avoid the circuit and mechanical structure damage caused by the volatile input signal.An MEHS experimental bench is constructed to verify the effectiveness of the theoretical conclusions proposed in this paper and the advantages of the proposed conclusions in this paper are illustrated by a series of contradistinctive experimental results.
基金National Natural Science Foundation of China (No. 50475038).
文摘Laser tracking system （LTS） is an advanced device for large size 3D coordinates measuring with the advantages of broad range, high speed and high accuracy. However, its measuring accuracy is highly dominated by the geometric errors of the tracking mirror mechanism. Proper calibration of LTS is essential prior to the use of it for metrology. A kinematics model that describes not only the motion but also the geometric variations of LTS is developed. Through error analysis of the proposed model, it is claimed that gimbals axis misalignments and tracking mirror center off-set are the key contributors to measuring errors of LTS. A self-calibration method is presented of calibrating LTS with planar constraints. Various calibration strategies utilizing single-plane and multiple-plane constraints are proposed for different situations. For each calibration strategy, issues about the error parameter estimation of LTS are exploded to find out in which conditions these parameters can be uniquely estimated. Moreover, these conditions reveal the applicability of the planar constraints to LTS self-calibration. Intensive studies have been made to check validity of the theoretical results. The results show that the measuring accuracy of LTS has increased by 5 times since this technique for calibration is used.
文摘离线强化学习旨在仅通过使用预先收集的离线数据集进行策略的有效学习,从而减少与环境直接交互所带来的高昂成本。然而,由于缺少环境对智能体行为的交互反馈,从离线数据集中学习到的策略可能会遇到数据分布偏移的问题,进而导致外推误差的不断加剧。当前方法多采用策略约束或模仿学习方法来缓解这一问题,但其学习到的策略通常较为保守。针对上述难题,提出一种基于自适应分位数的方法。具体而言,该方法在双Q估计的基础上进一步利用双Q的估计差值大小对分布外未知动作的价值高估情况进行评估,同时结合分位数思想自适应调整分位数来校正过估计偏差。此外,构建分位数优势函数作为策略约束项权重以平衡智能体对数据集的探索和模仿,从而缓解策略学习的保守性。最后在D4RL(datasets for deep data-driven reinforcement learning)数据集上验证算法的有效性,该算法在多个任务数据集上表现优异,同时展现出在不同场景应用下的广泛潜力。
