The paper approaches the problem of the command functions of galvanometer-based scanners （GS） that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to p...The paper approaches the problem of the command functions of galvanometer-based scanners （GS） that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to produce the highest possible duty cycle （i.e., time efficiency） of the device. We have completed this theoretical aspect （which contradicted what has been stated previously in the literature, where it has been considered that the linear plus sinusoidal scanning function was the best） with the experimental study of the most used scanning functions of the GSs （sawtooth, sinusoidal and triangular）, with applications in biomedical imaging, in particular in optical coherence tomography, demonstrating that the triangular function is always the best one to be applied, from both an optical and a mechanical point of view. In the present study the input voltage/command function which should be applied to the GS to produce the desired triangular scanning function （with controlled non-linearity for the fastest possible stop-and-turn portions） was determined analytically, in relationship with the active torque that drives the device. This command function is analyzed with regard to the specific, respectively required parameters of the GS： natural frequency and damping factor, respectively scan speed and amplitude. The modeling in an open loop control structure of the GS is finally discussed as a trade-off between using the highest possible duty cycle and minimizing the maximum peaks of the input voltage.展开更多
In this paper,an integrated estimation guidance and control(IEGC)system is designed based on the command filtered backstepping approach for circular field-of-view(FOV)strapdown missiles.The threedimensional integrated...In this paper,an integrated estimation guidance and control(IEGC)system is designed based on the command filtered backstepping approach for circular field-of-view(FOV)strapdown missiles.The threedimensional integrated estimation guidance and control nonlinear model with limited actuator deflection angle is established considering the seeker's FOV constraint.The boundary time-varying integral barrier Lyapunov function(IBLF)is employed in backstepping design to constrain the body line-of-sight(BLOS)in IEGC system to fit a circular FOV.Then,the nonlinear adaptive controller is designed to estimate the changing aerodynamic parameters.The generalized extended state observer(GESO)is designed to estimate the acceleration of the maneuvering targets and the unmatched time-varying disturbances for improving tracking accuracy.Furthermore,the command filters are used to solve the"differential expansion"problem during the backstepping design.The Lyapunov theory is used to prove the stability of the overall closed-loop IEGC system.Finally,the simulation results validate the integrated system's effectiveness,achieving high accuracy strikes against maneuvering targets.展开更多
Learning from demonstration is widely regarded as a promising paradigm for robots to acquire diverse skills.Other than the artificial learning from observation-action pairs for machines,humans can learn to imitate in ...Learning from demonstration is widely regarded as a promising paradigm for robots to acquire diverse skills.Other than the artificial learning from observation-action pairs for machines,humans can learn to imitate in a more versatile and effective manner:acquiring skills through mere“observation”.Video to Command task is widely perceived as a promising approach for task-based learning,which yet faces two key challenges:(1)High redundancy and low frame rate of fine-grained action sequences make it difficult to manipulate objects robustly and accurately.(2)Video to Command models often prioritize accuracy and richness of output commands over physical capabilities,leading to impractical or unsafe instructions for robots.This article presents a novel Video to Command framework that employs multiple data associations and physical constraints.First,we introduce an object-level appearancecontrasting multiple data association strategy to effectively associate manipulated objects in visually complex environments,capturing dynamic changes in video content.Then,we propose a multi-task Video to Command model that utilizes object-level video content changes to compile expert demonstrations into manipulation commands.Finally,a multi-task hybrid loss function is proposed to train a Video to Command model that adheres to the constraints of the physical world and manipulation tasks.Our method achieved over 10%on BLEU_N,METEOR,ROUGE_L,and CIDEr compared to the up-to-date methods.The dual-arm robot prototype was established to demonstrate the whole process of learning from an expert demonstration of multiple skills and then executing the tasks by a robot.展开更多
This paper explores the model reference adaptive control problem for a class of switched linear systems under arbitrary switching with no need for the measurability of the system state.Based on the state of reference ...This paper explores the model reference adaptive control problem for a class of switched linear systems under arbitrary switching with no need for the measurability of the system state.Based on the state of reference model and the measurable output error, adaptive laws and controllers are designed for switched systems.Each subsystem may have its individual reference model and controller, which increases the design flexibility.The introduction of the closed-loop reference model is to get a better transient performance of the whole switched systems.A numerical example is provided to verify the effectiveness of the main results.展开更多
The spectral analysis of simulated N-team of interacting decision makers with bounded rationality constraints of Oladejo, which assumes triangular probability density function of command inputs is hereby restructured ...The spectral analysis of simulated N-team of interacting decision makers with bounded rationality constraints of Oladejo, which assumes triangular probability density function of command inputs is hereby restructured and analysed, to have hierarchical command inputs that are predicated on order statistics distributions. The results give optimal distributions.展开更多
To solve the flight safety problem caused by nonlinear instabilities（category II pilot induced oscillations, PIOs） of the closed-loop pilot-vehicle system with rate-limiting actuator, the antiwindup（AW） compensati...To solve the flight safety problem caused by nonlinear instabilities（category II pilot induced oscillations, PIOs） of the closed-loop pilot-vehicle system with rate-limiting actuator, the antiwindup（AW） compensation method to avoid category II PIOs is investigated. Firstly, the AW compensation method originally used for controlling input magnitude limited system is introduced, then this method is extended for controlling input rate-limiting system through a circle criterion theorem. Secondly, the establishment of the AW compensator is transformed into the solving of linear matrix inequalities. Finally, an AW compensator establishment algorithm for the closed-loop pilot-vehicle system with the rate-limiting actuator is obtained. The effectiveness of the AW compensation method to avoid category II PIOs is validated by time-domain simulations,and compared with rate-limited feedback（RLF） command rate compensation method. The results show that the AW compensation method can effectively suppress category II PIOs and maintain the nominal performance when the closed-loop pilot-vehicle system is normal. Unlike the command rate compensator which works upon system uninterruptedly, the AW compensation method affects the closed-loop pilot-vehicle system only when the rate-limiting of actuator is activated, so it is a novel PIO avoidance method.展开更多
Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics analysis.Multiple closed-loop transfer functions can be cons...Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics analysis.Multiple closed-loop transfer functions can be constructed when different components of the converter controller are taken into account.However,the effect of different components of the converter controller on inter-harmonic stability analysis is not clear.In this paper,the complete transfer function,considering different loops,is first given.Based on the complete closed-loop transfer function,the DC-link,PLL and voltage forward-feed are removed step by step to derive different closed-loop transfer functions.The inter-harmonic related poles of different closed-loop transfer functions are further calculated to analyze the effect of closedloop transfer functions on inter-harmonic characteristics analysis.Finally,by performing time domain simulation,the correctness of the theoretical analysis results is verified.The results show that under the conditions of a weak AC system,each loop of the converter control system will reduce the stability of the interharmonic in the sub-synchronous frequency range and influence the inter-harmonic oscillation frequency.The transfer function needs to consider the influence of each loop to accurately calculate the inter-harmonic stability of the system.展开更多
基金the support of the US Department of State through Fulbright Scholar Grant 474/2009
文摘The paper approaches the problem of the command functions of galvanometer-based scanners （GS） that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to produce the highest possible duty cycle （i.e., time efficiency） of the device. We have completed this theoretical aspect （which contradicted what has been stated previously in the literature, where it has been considered that the linear plus sinusoidal scanning function was the best） with the experimental study of the most used scanning functions of the GSs （sawtooth, sinusoidal and triangular）, with applications in biomedical imaging, in particular in optical coherence tomography, demonstrating that the triangular function is always the best one to be applied, from both an optical and a mechanical point of view. In the present study the input voltage/command function which should be applied to the GS to produce the desired triangular scanning function （with controlled non-linearity for the fastest possible stop-and-turn portions） was determined analytically, in relationship with the active torque that drives the device. This command function is analyzed with regard to the specific, respectively required parameters of the GS： natural frequency and damping factor, respectively scan speed and amplitude. The modeling in an open loop control structure of the GS is finally discussed as a trade-off between using the highest possible duty cycle and minimizing the maximum peaks of the input voltage.
文摘In this paper,an integrated estimation guidance and control(IEGC)system is designed based on the command filtered backstepping approach for circular field-of-view(FOV)strapdown missiles.The threedimensional integrated estimation guidance and control nonlinear model with limited actuator deflection angle is established considering the seeker's FOV constraint.The boundary time-varying integral barrier Lyapunov function(IBLF)is employed in backstepping design to constrain the body line-of-sight(BLOS)in IEGC system to fit a circular FOV.Then,the nonlinear adaptive controller is designed to estimate the changing aerodynamic parameters.The generalized extended state observer(GESO)is designed to estimate the acceleration of the maneuvering targets and the unmatched time-varying disturbances for improving tracking accuracy.Furthermore,the command filters are used to solve the"differential expansion"problem during the backstepping design.The Lyapunov theory is used to prove the stability of the overall closed-loop IEGC system.Finally,the simulation results validate the integrated system's effectiveness,achieving high accuracy strikes against maneuvering targets.
基金Supported by Zhejiang Provincial Key Research and Development Program(Grant No.2021C04015)。
文摘Learning from demonstration is widely regarded as a promising paradigm for robots to acquire diverse skills.Other than the artificial learning from observation-action pairs for machines,humans can learn to imitate in a more versatile and effective manner:acquiring skills through mere“observation”.Video to Command task is widely perceived as a promising approach for task-based learning,which yet faces two key challenges:(1)High redundancy and low frame rate of fine-grained action sequences make it difficult to manipulate objects robustly and accurately.(2)Video to Command models often prioritize accuracy and richness of output commands over physical capabilities,leading to impractical or unsafe instructions for robots.This article presents a novel Video to Command framework that employs multiple data associations and physical constraints.First,we introduce an object-level appearancecontrasting multiple data association strategy to effectively associate manipulated objects in visually complex environments,capturing dynamic changes in video content.Then,we propose a multi-task Video to Command model that utilizes object-level video content changes to compile expert demonstrations into manipulation commands.Finally,a multi-task hybrid loss function is proposed to train a Video to Command model that adheres to the constraints of the physical world and manipulation tasks.Our method achieved over 10%on BLEU_N,METEOR,ROUGE_L,and CIDEr compared to the up-to-date methods.The dual-arm robot prototype was established to demonstrate the whole process of learning from an expert demonstration of multiple skills and then executing the tasks by a robot.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61233002)the 111 Project(Grant No.B16009)the IAPI Fundamental Research Funds(Grant No.2013ZCX03-01)
文摘This paper explores the model reference adaptive control problem for a class of switched linear systems under arbitrary switching with no need for the measurability of the system state.Based on the state of reference model and the measurable output error, adaptive laws and controllers are designed for switched systems.Each subsystem may have its individual reference model and controller, which increases the design flexibility.The introduction of the closed-loop reference model is to get a better transient performance of the whole switched systems.A numerical example is provided to verify the effectiveness of the main results.
文摘The spectral analysis of simulated N-team of interacting decision makers with bounded rationality constraints of Oladejo, which assumes triangular probability density function of command inputs is hereby restructured and analysed, to have hierarchical command inputs that are predicated on order statistics distributions. The results give optimal distributions.
基金supported by the National Basic Research Program(973Program)(2015CB755805)the National Natural Science Foundation of China(61374145)
文摘To solve the flight safety problem caused by nonlinear instabilities（category II pilot induced oscillations, PIOs） of the closed-loop pilot-vehicle system with rate-limiting actuator, the antiwindup（AW） compensation method to avoid category II PIOs is investigated. Firstly, the AW compensation method originally used for controlling input magnitude limited system is introduced, then this method is extended for controlling input rate-limiting system through a circle criterion theorem. Secondly, the establishment of the AW compensator is transformed into the solving of linear matrix inequalities. Finally, an AW compensator establishment algorithm for the closed-loop pilot-vehicle system with the rate-limiting actuator is obtained. The effectiveness of the AW compensation method to avoid category II PIOs is validated by time-domain simulations,and compared with rate-limited feedback（RLF） command rate compensation method. The results show that the AW compensation method can effectively suppress category II PIOs and maintain the nominal performance when the closed-loop pilot-vehicle system is normal. Unlike the command rate compensator which works upon system uninterruptedly, the AW compensation method affects the closed-loop pilot-vehicle system only when the rate-limiting of actuator is activated, so it is a novel PIO avoidance method.
基金supported by Research Project Huadong Engineering Corporation Limited,and National Natural Science Foundation of China(U22B20100,52321004).
文摘Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics analysis.Multiple closed-loop transfer functions can be constructed when different components of the converter controller are taken into account.However,the effect of different components of the converter controller on inter-harmonic stability analysis is not clear.In this paper,the complete transfer function,considering different loops,is first given.Based on the complete closed-loop transfer function,the DC-link,PLL and voltage forward-feed are removed step by step to derive different closed-loop transfer functions.The inter-harmonic related poles of different closed-loop transfer functions are further calculated to analyze the effect of closedloop transfer functions on inter-harmonic characteristics analysis.Finally,by performing time domain simulation,the correctness of the theoretical analysis results is verified.The results show that under the conditions of a weak AC system,each loop of the converter control system will reduce the stability of the interharmonic in the sub-synchronous frequency range and influence the inter-harmonic oscillation frequency.The transfer function needs to consider the influence of each loop to accurately calculate the inter-harmonic stability of the system.
