More and more linear servo systems have been used in servo applications. Direct drive technology can greatly increase the bandwidth and the tracking accuracy. A position servo-system based on linear voice-coil motor w...More and more linear servo systems have been used in servo applications. Direct drive technology can greatly increase the bandwidth and the tracking accuracy. A position servo-system based on linear voice-coil motor was designed for one linear oscillation movement application. Besides the conventional position, speed and current control loops, the speed and acceleration feed-forward control of command position signal were also used. The experimental test proved the correctness of the design, and the system can track the given periodic sinusoid position command signal of 15Hz with high accuracy. The linear voice-coil motor is very suitable for short stroke position tracking application with high dynamic response.展开更多
This paper propees the consistent extended Kalman flter(CEKF)for the maneuvering target tracking(MTT)with nonlinear uncertain dynamics,and applies it on hand poition tracking.The general modlel of the MTT system i pre...This paper propees the consistent extended Kalman flter(CEKF)for the maneuvering target tracking(MTT)with nonlinear uncertain dynamics,and applies it on hand poition tracking.The general modlel of the MTT system i presented with unmodleled dynamics in terms of nonlinear unknown function of states.The CEKF is propoeed to ensure that the bounds of the estimation error's covariance matrix are av ailable through the flter algorithm.As a result,the creponding accuracy of the flter approach can be achieved online.Furthermore,a CEKF-baaed MTT algorithm is constructed via the tumning aw of the critical parameter matrix QE Finally,the efectiveness of CEKF i verified by MTT numerical simulations and hand tacking expeiments under dilferent maneuvens.Specifcally,two indices are employed to compare the CEKF with extended Kalman filter(EKF):the mean square errors(MSEa)and the bounded percentage,ie the percentage of the rang w bere the estimation error is encboed by the bound calculated by algorithms.All MSEs of CEKF are smaller than thoee of EKF,where the worst MSEa of CEKF and EKF are0.14 and 418 in the simulation,a8 well 80.11 and 059 in the expeiments,respectively;all bounded percentages of CEKF are larger than thoee of EKF,where the wonst average bounded percentages of CEKF and EKF ame 87.86%and 14.58%,8 well as 97.41%and 41.79%in the experiments,reapectively.展开更多
The performance of the state-of-the-art Deep Reinforcement algorithms such as Proximal Policy Optimization, Twin Delayed Deep Deterministic Policy Gradient, and Soft Actor-Critic for generating a quadruped walking gai...The performance of the state-of-the-art Deep Reinforcement algorithms such as Proximal Policy Optimization, Twin Delayed Deep Deterministic Policy Gradient, and Soft Actor-Critic for generating a quadruped walking gait in a virtual environment was presented in previous research work titled “A Comparison of PPO, TD3, and SAC Reinforcement Algorithms for Quadruped Walking Gait Generation”. We demonstrated that the Soft Actor-Critic Reinforcement algorithm had the best performance generating the walking gait for a quadruped in certain instances of sensor configurations in the virtual environment. In this work, we present the performance analysis of the state-of-the-art Deep Reinforcement algorithms above for quadruped walking gait generation in a physical environment. The performance is determined in the physical environment by transfer learning augmented by real-time reinforcement learning for gait generation on a physical quadruped. The performance is analyzed on a quadruped equipped with a range of sensors such as position tracking using a stereo camera, contact sensing of each of the robot legs through force resistive sensors, and proprioceptive information of the robot body and legs using nine inertial measurement units. The performance comparison is presented using the metrics associated with the walking gait: average forward velocity (m/s), average forward velocity variance, average lateral velocity (m/s), average lateral velocity variance, and quaternion root mean square deviation. The strengths and weaknesses of each algorithm for the given task on the physical quadruped are discussed.展开更多
Adaptive control of servo actuator with nonlinear friction compensation is addressed. LuGre dynamic friction model is adopted to characterize the nonlinear friction and a new kind of slid ing mode observer is designe...Adaptive control of servo actuator with nonlinear friction compensation is addressed. LuGre dynamic friction model is adopted to characterize the nonlinear friction and a new kind of slid ing mode observer is designed to estimate the internal immeasurable state of LuGre model. Based on the estimated friction state, adaptive laws are designed to identify the unknown model parameters and the external disturbances, and the system stability and asymptotic trajectory tracking perform ance are guaranteed by Lyapunov function. The position tracking performance is verified by the ex perimental results.展开更多
In this paper we discuss a kind of multitarget tracking and association method based on the data fusion of heterogeneous multiple feature data gained by a sensor such as space state, signal amplitude, Doppler frequenc...In this paper we discuss a kind of multitarget tracking and association method based on the data fusion of heterogeneous multiple feature data gained by a sensor such as space state, signal amplitude, Doppler frequency and so on. In order to introduce quantitatively those heterogeneous multiple feature data which are possibly gained by a sensor into the discussion of tracking and association problem, we define a correlation measure which we explain as the generalization of conventional association decision. In conventional Nearest Neighbor method, the decision function can take only two values, 1 or 0, to represent the decision of association or not association. In our method, correlation measure can be take any real value from 0 to 1 to represent the extent of correlation. Considering the practical circumstances that some feature data might not be easily gained continuously, we introduce an effective factor to deal with these cases. In the paper we also discuss the comparative computer simulation tests and give the results.展开更多
The existing third-order tracker known as α-β-γ-δ filter has been used for target tracking and predicting for years. The filter can track the target's position and velocity, but not the acceleration. To extend it...The existing third-order tracker known as α-β-γ-δ filter has been used for target tracking and predicting for years. The filter can track the target's position and velocity, but not the acceleration. To extend its capability, a new fourth-order target tracker called α-β-γ-δ filter is proposed. The main objective of this study was to find the optimal set of filter parameters that leads to minimum position tracking errors. The tracking errors between using the α-β-γ-δ filter and the α-β-γ-δ filter are compared. As a result, the new filter exhibits significant improvement in position tracking accuracy over the existing third-order filter, but at the expense of computational time in search of the optimal filter. To reduce the computational time, a simulation-based optimization technique via Taguchi method is introduced.展开更多
Wireless sensor networks(WSNs)are created and affect our daily lives.You can find applications in various fields such as health,accident,life,manufacturing,production management,network management and many other field...Wireless sensor networks(WSNs)are created and affect our daily lives.You can find applications in various fields such as health,accident,life,manufacturing,production management,network management and many other fields.WSN now connects to the Internet of Things,connects the sensor to the Internet,and then uses it for collaboration and collaboration.However,when WSN is part of the internet we need to be able to study and analyze related terms.In this article,we’re going to look at different ways to getWSN online and identify the challenges that address in future as well.展开更多
Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Con...Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Considering the complete description of flight dynamics,aerodynamics and airflow interference,the dynamical model of CRA is established.The dynamical model is simplified according to the actual flight,then the simplified dynamical model is divided into two subsystems:a fully-actuated subsystem and an under-actuated subsystem.The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller,while the controller of the under-actuated subsystem is composed of a SMC controller.The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem.Lyapunov stability theory is used to verify the stability of the sliding mode controller,which ensures that all state trajectories of the system can reach and stay on the sliding mode surface,the uncertainty and external interference of the model are compensated.Simulation and experiment compared with the conventional PIDC are carried out,the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.展开更多
The attitude tracking control problem for a satellite with parameter uncertainties and external disturbances is considered in this paper. For this class of multi-input multi-output uncertain nonlinear systems, a desig...The attitude tracking control problem for a satellite with parameter uncertainties and external disturbances is considered in this paper. For this class of multi-input multi-output uncertain nonlinear systems, a design method of robust output tracking controllers is proposed based on the upper-bounds of the uncertainties. Using the input/output feedback linearization approach and Lyapunov method, a control law is designed, which guarantees that the system output exponentially tracks the given desired output. The proposed controller is easy to compute and complement. Simulation results show that, in the closed-loop system, precise attitude control is accomplished in spite of the uncertainties in the system.展开更多
Track monitoring is a fast method of determining incorrect return-to-track and track-to-track assignments. An analytical method to evaluate the effectiveness of track monitoring was presented by reference [1]. In orde...Track monitoring is a fast method of determining incorrect return-to-track and track-to-track assignments. An analytical method to evaluate the effectiveness of track monitoring was presented by reference [1]. In order to reduce the probability of initiating or accepting the ghost track, two sequential track monitoring algorithms, which use the inclination angles to form test statistics, are proposed in this paper. Two decision rules are given and the corresponding thresholds are derived. The paper also gives the estimation methods of the noncentral parameter of noncentral chi-square distribution when the true value of it is unknown, the algorithms can adaptively estimate the decision thresholds and can make sequential track monitoring decision on line. Simulation is also made and the results show that the proposed algorithms are effective and feasible.展开更多
To improve the robustness of visual tracking in complex environments such as: cluttered backgrounds, partial occlusions, similar distraction and pose variations, a novel tracking method based on adaptive fusion and pa...To improve the robustness of visual tracking in complex environments such as: cluttered backgrounds, partial occlusions, similar distraction and pose variations, a novel tracking method based on adaptive fusion and particle filter is proposed in this paper. In this method, the image color and shape cues are adaptively fused to represent the target observation; fuzzy logic is applied to dynamically adjust each cue weight according to its associated reliability in the past frame; particle filter is adopted to deal with non-linear and non-Gaussian problems in visual tracking. The method is demonstrated to be robust to illumination changes, pose variations, partial occlusions, cluttered backgrounds and camera motion for a test image sequence.展开更多
The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances incl...The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances including parametric uncertainties,flexible vibration,and unknown nonlinear dynamics degrade the control performance significantly.In order to enhance the system anti-disturbance ability,this paper proposes a composite anti-disturbance control law for the spacecraft position and attitude tracking.Firstly,the relative position and attitude dynamic models with multiple disturbances are established,where the refined descriptions of multiple disturbances are accomplished based on their characteristics.Then,by combining a dual Disturbance ObserverBased Control(DOBC)and a sliding mode control,a composite controller with hierarchical architecture is proposed,where the dual DOBC in the feedforward channel is used to reject the flexible vibration,environment disturbance,and complicated nonlinear dynamics,while the parametric uncertainties are attenuated by the sliding mode control in the feedback channel.Stability analysis is carried out for the closed-loop system by unifying the sliding mode dynamics and observer dynamics.Finally,the effectiveness of the proposed controller is verified via numerical simulation and hardware-in-the-loop test.展开更多
In this paper, an improved tracking and local-ization algorithm of an omni-directional mobile industrialrobot is proposed to meet the high positional accuracyrequirement, improve the robot's repeatability positioning...In this paper, an improved tracking and local-ization algorithm of an omni-directional mobile industrialrobot is proposed to meet the high positional accuracyrequirement, improve the robot's repeatability positioningprecision in the traditional trilateral algorithm, and solvethe problem of pose lost in the moving process. Lasersensors are used to identify the reflectors, and by associ-ating the reflectors identified at a particular time with thereflectors at a previous time, an optimal triangular posi-tioning method is applied to realize the positioning andtracking of the robot. The experimental results show thatpositioning accuracy can be satisfied, and the repeatabilityand anti-jamming ability of the omni-directional mobileindustrial robot will be greatly improved via this algorithm.展开更多
Sliding mode control (SMC) has been widely investigated in recent years. In this paper, a class of second- order SMC is proposed and used to achieve good tracking performance in servo systems. SMC has good robustnes...Sliding mode control (SMC) has been widely investigated in recent years. In this paper, a class of second- order SMC is proposed and used to achieve good tracking performance in servo systems. SMC has good robustness to the disturbances, but conventional SMC uses a sign function to drive the error on the sliding surface, which could generate chattering effect. In order to avoid this problem, our improved SMC uses the integral of the sign function. Coupled with an exponential reaching law, the new SMC can better suppress torque disturbances and chatter, This paper first gives the derivation of the new SMC. Simulation and experimental results are then carried out to demonstrate its tracking performance and robustness against torque disturbance and chatter.展开更多
Pilot two-stage proportional valves are widely used in high-power hydraulic systems. For the purpose of improving the dynamic performance, reliability, and digitization of the traditional proportional valve, a novel t...Pilot two-stage proportional valves are widely used in high-power hydraulic systems. For the purpose of improving the dynamic performance, reliability, and digitization of the traditional proportional valve, a novel two-stage proportional valve with a pilot digital flow distribution is proposed from the viewpoint of the dual nozzle-flapper valve’s working principle. In particular, the dual nozzle-flapper is decoupled by two high-speed on/off valves (HSVs). First, the working principle and mathematical model of the proposed valve are determined. Then, the influences of the control parameters (duty cycle and switching frequency) and structural parameters (fixed orifice’s diameter and main valve’s spring) on the main valve’s motion are analyzed on the basis of theory, simulation, and experiment. In addition, in optimizing the value of the fixed orifice’s diameter, a new design criterion that considers the maximum pressure sensitivity, flow controllability, and flow linearization is proposed to improve the balance between the effective displacement and the displacement fluctuation of the main valve. The new scheme is verified by simulations and experiments. Experimental results of the closed-loop displacement tracking have demonstrated that the delay time of the main valve is always within 3.5 ms under different working conditions, and the tracking error can be significantly reduced using the higher switching frequency. The amplitude–frequency experiments indicate that a −3 dB-frequency of the proposed valve can reach 9.5 Hz in the case of ±50% full scale and 15 Hz in the case of 0%–50% full scale. The values can be further improved by increasing the flow rate of the pilot HSV.展开更多
Purpose–The purpose of this paper is to present a control strategy which uses two independent PID controllers to realize the hovering control for unmanned aerial systems(UASs).In addition,the aim of using two PID con...Purpose–The purpose of this paper is to present a control strategy which uses two independent PID controllers to realize the hovering control for unmanned aerial systems(UASs).In addition,the aim of using two PID controller is to achieve the position control and velocity control simultaneously.Design/methodology/approach–The dynamic of the UASs is mathematically modeled.One PID controller is used for position tracking control,while the other is selected for the vertical component of velocity tracking control.Meanwhile,fuzzy logic algorithm is presented to use the actual horizontal component of velocity to compute the desired position.Findings–Based on this fuzzy logic algorithm,the control error of the horizontal component of velocity tracking control is narrowed gradually to be zero.The results show that the fuzzy logic algorithm can make the UASs hover still in the air and vertical to the ground.Social implications–The acquired results are based on simulation not experiment.Originality/value–This is the first study to use two independent PID controllers to realize stable hovering control for UAS.It is also the first to use the velocity of the UAS to calculate the desired position.展开更多
A new cross-tracking method is proposed to improve the convergent speed of the control algorithm in real-time polarization mode dispersion(PMD)compensation systems.The cross-tracking algorithm is compared with the p...A new cross-tracking method is proposed to improve the convergent speed of the control algorithm in real-time polarization mode dispersion(PMD)compensation systems.The cross-tracking algorithm is compared with the previously used dithering particle swarm optimization(DPSO)and gradient particle swarm optimization(GPSO)algorithms,and it is proven to offer the best performance among the three algorithms.The transmission of a 43-Gb/s differential quadrature phase-shift keying(DQPSK)signal over a 1 200-km fiber span using a compensator based on digital signal processing(DSP)is demonstrated via the cross-tracking algorithm.展开更多
The increasing demana for advanced modelling methods, which can reflect complex travel activities of individuals, requires enhanced travel data collection methods. The introduction of GPS-assisted data collection meth...The increasing demana for advanced modelling methods, which can reflect complex travel activities of individuals, requires enhanced travel data collection methods. The introduction of GPS-assisted data collection methods has provided an alternative to the conventional methods of travel data collection. GPS-assisted data collection methods improve the accu- racy of data collection and enable capturing more details of individuals' travel behaviour. Recent technological advancements in smartphone-based positioning technologies and communication facilities have opened up new opportunities to apply smartphones as the media of GPS-assisted data collection. Although, different GPS-assisted methods have been employed recently, their performance has not been widely evaluated in real-world experi- ments compared to traditional data collection methods. Accordingly, this paper evaluates the performance of three GPS-assisted methods, namely handheld GPS tracking, smart- phone-based GPS tracking and smartphone-based prompted-recall data collection methods, in conjunction with the web-based data collection to shed light on different aspects of GPS- assisted data collection methods. These methods are compared in terms of the quality and accuracy of the collected data, the demographic attributes of participants and the specifi- cations of labelled trips. The results show that an appropriate employment of smartphones enhances the accuracy of data collection. It is also found that putting an extra burden on participants during a travel data collection survey results in lower trip-rates and poor data quality. Finally, it is found that the application of smartphone-assisted data collection methods help reporting non-motorised trips more accurately.展开更多
文摘More and more linear servo systems have been used in servo applications. Direct drive technology can greatly increase the bandwidth and the tracking accuracy. A position servo-system based on linear voice-coil motor was designed for one linear oscillation movement application. Besides the conventional position, speed and current control loops, the speed and acceleration feed-forward control of command position signal were also used. The experimental test proved the correctness of the design, and the system can track the given periodic sinusoid position command signal of 15Hz with high accuracy. The linear voice-coil motor is very suitable for short stroke position tracking application with high dynamic response.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.62025307,U1913209,61973299,61873013)the Beijing Natural Science Foundation(Grant No.JQ19020)supported in part by the Key Laboratory of Systems and Control,Chinese Academy of Sciences.
文摘This paper propees the consistent extended Kalman flter(CEKF)for the maneuvering target tracking(MTT)with nonlinear uncertain dynamics,and applies it on hand poition tracking.The general modlel of the MTT system i presented with unmodleled dynamics in terms of nonlinear unknown function of states.The CEKF is propoeed to ensure that the bounds of the estimation error's covariance matrix are av ailable through the flter algorithm.As a result,the creponding accuracy of the flter approach can be achieved online.Furthermore,a CEKF-baaed MTT algorithm is constructed via the tumning aw of the critical parameter matrix QE Finally,the efectiveness of CEKF i verified by MTT numerical simulations and hand tacking expeiments under dilferent maneuvens.Specifcally,two indices are employed to compare the CEKF with extended Kalman filter(EKF):the mean square errors(MSEa)and the bounded percentage,ie the percentage of the rang w bere the estimation error is encboed by the bound calculated by algorithms.All MSEs of CEKF are smaller than thoee of EKF,where the worst MSEa of CEKF and EKF are0.14 and 418 in the simulation,a8 well 80.11 and 059 in the expeiments,respectively;all bounded percentages of CEKF are larger than thoee of EKF,where the wonst average bounded percentages of CEKF and EKF ame 87.86%and 14.58%,8 well as 97.41%and 41.79%in the experiments,reapectively.
文摘The performance of the state-of-the-art Deep Reinforcement algorithms such as Proximal Policy Optimization, Twin Delayed Deep Deterministic Policy Gradient, and Soft Actor-Critic for generating a quadruped walking gait in a virtual environment was presented in previous research work titled “A Comparison of PPO, TD3, and SAC Reinforcement Algorithms for Quadruped Walking Gait Generation”. We demonstrated that the Soft Actor-Critic Reinforcement algorithm had the best performance generating the walking gait for a quadruped in certain instances of sensor configurations in the virtual environment. In this work, we present the performance analysis of the state-of-the-art Deep Reinforcement algorithms above for quadruped walking gait generation in a physical environment. The performance is determined in the physical environment by transfer learning augmented by real-time reinforcement learning for gait generation on a physical quadruped. The performance is analyzed on a quadruped equipped with a range of sensors such as position tracking using a stereo camera, contact sensing of each of the robot legs through force resistive sensors, and proprioceptive information of the robot body and legs using nine inertial measurement units. The performance comparison is presented using the metrics associated with the walking gait: average forward velocity (m/s), average forward velocity variance, average lateral velocity (m/s), average lateral velocity variance, and quaternion root mean square deviation. The strengths and weaknesses of each algorithm for the given task on the physical quadruped are discussed.
基金Supported by State Key Laboratory of Explosion Science and Technology(QNKT11-08)
文摘Adaptive control of servo actuator with nonlinear friction compensation is addressed. LuGre dynamic friction model is adopted to characterize the nonlinear friction and a new kind of slid ing mode observer is designed to estimate the internal immeasurable state of LuGre model. Based on the estimated friction state, adaptive laws are designed to identify the unknown model parameters and the external disturbances, and the system stability and asymptotic trajectory tracking perform ance are guaranteed by Lyapunov function. The position tracking performance is verified by the ex perimental results.
基金supported by the International S&T Cooperation Projects of China(2015DFR10510)the National Natural Science Foundation of China(61440048+1 种基金61562018)the Scientific Research Program of the Higher Education Institutions of Hainan Province(HNKY2014-04)
文摘In this paper we discuss a kind of multitarget tracking and association method based on the data fusion of heterogeneous multiple feature data gained by a sensor such as space state, signal amplitude, Doppler frequency and so on. In order to introduce quantitatively those heterogeneous multiple feature data which are possibly gained by a sensor into the discussion of tracking and association problem, we define a correlation measure which we explain as the generalization of conventional association decision. In conventional Nearest Neighbor method, the decision function can take only two values, 1 or 0, to represent the decision of association or not association. In our method, correlation measure can be take any real value from 0 to 1 to represent the extent of correlation. Considering the practical circumstances that some feature data might not be easily gained continuously, we introduce an effective factor to deal with these cases. In the paper we also discuss the comparative computer simulation tests and give the results.
文摘The existing third-order tracker known as α-β-γ-δ filter has been used for target tracking and predicting for years. The filter can track the target's position and velocity, but not the acceleration. To extend its capability, a new fourth-order target tracker called α-β-γ-δ filter is proposed. The main objective of this study was to find the optimal set of filter parameters that leads to minimum position tracking errors. The tracking errors between using the α-β-γ-δ filter and the α-β-γ-δ filter are compared. As a result, the new filter exhibits significant improvement in position tracking accuracy over the existing third-order filter, but at the expense of computational time in search of the optimal filter. To reduce the computational time, a simulation-based optimization technique via Taguchi method is introduced.
文摘Wireless sensor networks(WSNs)are created and affect our daily lives.You can find applications in various fields such as health,accident,life,manufacturing,production management,network management and many other fields.WSN now connects to the Internet of Things,connects the sensor to the Internet,and then uses it for collaboration and collaboration.However,when WSN is part of the internet we need to be able to study and analyze related terms.In this article,we’re going to look at different ways to getWSN online and identify the challenges that address in future as well.
基金supported by National Natural Science Founda-tion of china(Grant No.51774042).
文摘Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Considering the complete description of flight dynamics,aerodynamics and airflow interference,the dynamical model of CRA is established.The dynamical model is simplified according to the actual flight,then the simplified dynamical model is divided into two subsystems:a fully-actuated subsystem and an under-actuated subsystem.The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller,while the controller of the under-actuated subsystem is composed of a SMC controller.The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem.Lyapunov stability theory is used to verify the stability of the sliding mode controller,which ensures that all state trajectories of the system can reach and stay on the sliding mode surface,the uncertainty and external interference of the model are compensated.Simulation and experiment compared with the conventional PIDC are carried out,the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.
文摘The attitude tracking control problem for a satellite with parameter uncertainties and external disturbances is considered in this paper. For this class of multi-input multi-output uncertain nonlinear systems, a design method of robust output tracking controllers is proposed based on the upper-bounds of the uncertainties. Using the input/output feedback linearization approach and Lyapunov method, a control law is designed, which guarantees that the system output exponentially tracks the given desired output. The proposed controller is easy to compute and complement. Simulation results show that, in the closed-loop system, precise attitude control is accomplished in spite of the uncertainties in the system.
文摘Track monitoring is a fast method of determining incorrect return-to-track and track-to-track assignments. An analytical method to evaluate the effectiveness of track monitoring was presented by reference [1]. In order to reduce the probability of initiating or accepting the ghost track, two sequential track monitoring algorithms, which use the inclination angles to form test statistics, are proposed in this paper. Two decision rules are given and the corresponding thresholds are derived. The paper also gives the estimation methods of the noncentral parameter of noncentral chi-square distribution when the true value of it is unknown, the algorithms can adaptively estimate the decision thresholds and can make sequential track monitoring decision on line. Simulation is also made and the results show that the proposed algorithms are effective and feasible.
基金This work was jointly supported by the National Natural Science Foundation of China (No. 60375008)China PH.D Discipline Special Foundation (No. 20020248029)China Aviation Science Foundation (No. 02D57003)Aerospace Supporting Technology Foundation (No.2003-1.3 02), EXPO Technologies Special Project of National Key Technologies R&D Programme (No. 004BA908B07)Shanghai Key Technologies Preresearch Project (No. 035115009).
文摘To improve the robustness of visual tracking in complex environments such as: cluttered backgrounds, partial occlusions, similar distraction and pose variations, a novel tracking method based on adaptive fusion and particle filter is proposed in this paper. In this method, the image color and shape cues are adaptively fused to represent the target observation; fuzzy logic is applied to dynamically adjust each cue weight according to its associated reliability in the past frame; particle filter is adopted to deal with non-linear and non-Gaussian problems in visual tracking. The method is demonstrated to be robust to illumination changes, pose variations, partial occlusions, cluttered backgrounds and camera motion for a test image sequence.
基金supported by the China National Postdoctoral Program for Innovative Talents(No.BX20200031)the National Natural Science Foundation of China(Nos.62103013,61633003,61973012)the Program for Changjiang Scholars and Innovative Research Team,China(No.IRT 16R03).
文摘The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances including parametric uncertainties,flexible vibration,and unknown nonlinear dynamics degrade the control performance significantly.In order to enhance the system anti-disturbance ability,this paper proposes a composite anti-disturbance control law for the spacecraft position and attitude tracking.Firstly,the relative position and attitude dynamic models with multiple disturbances are established,where the refined descriptions of multiple disturbances are accomplished based on their characteristics.Then,by combining a dual Disturbance ObserverBased Control(DOBC)and a sliding mode control,a composite controller with hierarchical architecture is proposed,where the dual DOBC in the feedforward channel is used to reject the flexible vibration,environment disturbance,and complicated nonlinear dynamics,while the parametric uncertainties are attenuated by the sliding mode control in the feedback channel.Stability analysis is carried out for the closed-loop system by unifying the sliding mode dynamics and observer dynamics.Finally,the effectiveness of the proposed controller is verified via numerical simulation and hardware-in-the-loop test.
文摘In this paper, an improved tracking and local-ization algorithm of an omni-directional mobile industrialrobot is proposed to meet the high positional accuracyrequirement, improve the robot's repeatability positioningprecision in the traditional trilateral algorithm, and solvethe problem of pose lost in the moving process. Lasersensors are used to identify the reflectors, and by associ-ating the reflectors identified at a particular time with thereflectors at a previous time, an optimal triangular posi-tioning method is applied to realize the positioning andtracking of the robot. The experimental results show thatpositioning accuracy can be satisfied, and the repeatabilityand anti-jamming ability of the omni-directional mobileindustrial robot will be greatly improved via this algorithm.
基金supported by the Hong Kong Innovation and Technology Fund (No. ITS/005/01)the National Natural Science Foundation of China (No. 51005086)the Fundamental Research Funds for the Central Universities (No. 2010MS085)
文摘Sliding mode control (SMC) has been widely investigated in recent years. In this paper, a class of second- order SMC is proposed and used to achieve good tracking performance in servo systems. SMC has good robustness to the disturbances, but conventional SMC uses a sign function to drive the error on the sliding surface, which could generate chattering effect. In order to avoid this problem, our improved SMC uses the integral of the sign function. Coupled with an exponential reaching law, the new SMC can better suppress torque disturbances and chatter, This paper first gives the derivation of the new SMC. Simulation and experimental results are then carried out to demonstrate its tracking performance and robustness against torque disturbance and chatter.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51975275)the National Key Laboratory of Science and Technology on Helicopter Transmission(Nanjing University of Aeronautics and Astronautics),China(Grant No.HTL-A-20G02)the Postgraduate Research and Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX200178).
文摘Pilot two-stage proportional valves are widely used in high-power hydraulic systems. For the purpose of improving the dynamic performance, reliability, and digitization of the traditional proportional valve, a novel two-stage proportional valve with a pilot digital flow distribution is proposed from the viewpoint of the dual nozzle-flapper valve’s working principle. In particular, the dual nozzle-flapper is decoupled by two high-speed on/off valves (HSVs). First, the working principle and mathematical model of the proposed valve are determined. Then, the influences of the control parameters (duty cycle and switching frequency) and structural parameters (fixed orifice’s diameter and main valve’s spring) on the main valve’s motion are analyzed on the basis of theory, simulation, and experiment. In addition, in optimizing the value of the fixed orifice’s diameter, a new design criterion that considers the maximum pressure sensitivity, flow controllability, and flow linearization is proposed to improve the balance between the effective displacement and the displacement fluctuation of the main valve. The new scheme is verified by simulations and experiments. Experimental results of the closed-loop displacement tracking have demonstrated that the delay time of the main valve is always within 3.5 ms under different working conditions, and the tracking error can be significantly reduced using the higher switching frequency. The amplitude–frequency experiments indicate that a −3 dB-frequency of the proposed valve can reach 9.5 Hz in the case of ±50% full scale and 15 Hz in the case of 0%–50% full scale. The values can be further improved by increasing the flow rate of the pilot HSV.
文摘Purpose–The purpose of this paper is to present a control strategy which uses two independent PID controllers to realize the hovering control for unmanned aerial systems(UASs).In addition,the aim of using two PID controller is to achieve the position control and velocity control simultaneously.Design/methodology/approach–The dynamic of the UASs is mathematically modeled.One PID controller is used for position tracking control,while the other is selected for the vertical component of velocity tracking control.Meanwhile,fuzzy logic algorithm is presented to use the actual horizontal component of velocity to compute the desired position.Findings–Based on this fuzzy logic algorithm,the control error of the horizontal component of velocity tracking control is narrowed gradually to be zero.The results show that the fuzzy logic algorithm can make the UASs hover still in the air and vertical to the ground.Social implications–The acquired results are based on simulation not experiment.Originality/value–This is the first study to use two independent PID controllers to realize stable hovering control for UAS.It is also the first to use the velocity of the UAS to calculate the desired position.
基金supported by the National "863" Program of China(No.2009AA01Z224)the Fundamental Research Funds for the Central Universities(Nos.2009RC0401 and 2009RC0405)the China Postdoctoral Science Foundation(No.20100470259)
文摘A new cross-tracking method is proposed to improve the convergent speed of the control algorithm in real-time polarization mode dispersion(PMD)compensation systems.The cross-tracking algorithm is compared with the previously used dithering particle swarm optimization(DPSO)and gradient particle swarm optimization(GPSO)algorithms,and it is proven to offer the best performance among the three algorithms.The transmission of a 43-Gb/s differential quadrature phase-shift keying(DQPSK)signal over a 1 200-km fiber span using a compensator based on digital signal processing(DSP)is demonstrated via the cross-tracking algorithm.
基金partially supported by grant DE130100205 from the Australian Research Council
文摘The increasing demana for advanced modelling methods, which can reflect complex travel activities of individuals, requires enhanced travel data collection methods. The introduction of GPS-assisted data collection methods has provided an alternative to the conventional methods of travel data collection. GPS-assisted data collection methods improve the accu- racy of data collection and enable capturing more details of individuals' travel behaviour. Recent technological advancements in smartphone-based positioning technologies and communication facilities have opened up new opportunities to apply smartphones as the media of GPS-assisted data collection. Although, different GPS-assisted methods have been employed recently, their performance has not been widely evaluated in real-world experi- ments compared to traditional data collection methods. Accordingly, this paper evaluates the performance of three GPS-assisted methods, namely handheld GPS tracking, smart- phone-based GPS tracking and smartphone-based prompted-recall data collection methods, in conjunction with the web-based data collection to shed light on different aspects of GPS- assisted data collection methods. These methods are compared in terms of the quality and accuracy of the collected data, the demographic attributes of participants and the specifi- cations of labelled trips. The results show that an appropriate employment of smartphones enhances the accuracy of data collection. It is also found that putting an extra burden on participants during a travel data collection survey results in lower trip-rates and poor data quality. Finally, it is found that the application of smartphone-assisted data collection methods help reporting non-motorised trips more accurately.