Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness t...Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems. The tracking performance of the static loading is studied in this paper. Firstly, the nonlinear mathematical models of the hydraulic load simulator are derived, and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance. Considering the effect of the friction, a LuGre model based friction compensation is synthesized, in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded. The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter. Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy. The tracking performance is summarized by a derived theorem. Experimental results are also obtained to verify the high performance nature of the proposed control strategy.展开更多
Thin-walled components possess high strength and lightweight characteristics;thus,they are widely used in aerospace,automotive,and other industrial felds.However,their low stifness makes them susceptible to deformatio...Thin-walled components possess high strength and lightweight characteristics;thus,they are widely used in aerospace,automotive,and other industrial felds.However,their low stifness makes them susceptible to deformation induced by cutting forces during machining,which leads to poor form accuracy.To address this issue,this paper proposes an in-process deformation estimation and compensation method.Because direct,accurate measurement of the deformation at the cutting point is challenging,the deformation is estimated based on the deformations measured at points in the uncut area along the same axial line as the cutting point.To establish the deformation relationship along the axial line for estimation,fnite element method simulations are conducted to generate axial deformation profles corresponding to diferent cutting force locations.Additionally,a calibration coefcient obtained through experiments is applied to enhance the accuracy of the deformation estimation.Then,the estimated deformation is fed into the control loop of the fast tool servo system to compensate for machining-induced deformation efectively.To validate the efectiveness of the proposed method,machining experiments on sinusoidal pit arrays and sinusoidal grid microstructures are performed.The experimental results demonstrate that the proposed method substantially improves machining accuracy.展开更多
The effects of movement errors on imaging results of synthetic aperture sonar and the necessity of movement compensation are discussed. Based on analyzing so-called displaced phase center algorithm, an improved algori...The effects of movement errors on imaging results of synthetic aperture sonar and the necessity of movement compensation are discussed. Based on analyzing so-called displaced phase center algorithm, an improved algorithm is proposed. In this method, the time delay is estimated firstly, then the phase is estimated for the residual error, so that the range of movement error suited to the algorithm is extended to some extent. Some simulation results on computer and experimental results in the test tank using the proposed algorithm are given as well.展开更多
This paper deals with the problem of accelerometer error estimation and compensation for a three-axis gyro-stabilized camera mount. In a dynamic environment, the aircraft motion acceleration affects the accelerome ：e...This paper deals with the problem of accelerometer error estimation and compensation for a three-axis gyro-stabilized camera mount. In a dynamic environment, the aircraft motion acceleration affects the accelerome ：er output and causes a degradation of attitude steady accuracy. In order to improve control accuracy, this paper proposes a proportional multiple-integral observer- based control strategy to estimate and compensate the accelerometer error. The basic idea of this paper is to approximate the error property by using a q-order polynomial function and extend the error and its derivatives as augmented states. Then a proportional multiple-integral observer is developed to estimate the error, with which the relationship between the error and the imbalance torque is formulated. The estimated value is compared to an angle threshold, the result of which is used to compen- sate the accelerometer output. Through static and vehicle-mounted experiments, it is demonstrated that compared with the tra- ditional method, the proposed method can improve the attitude steady accuracy effectively.展开更多
Motion blur restoration is essential for the imaging of moving objects,especially for single-pixel imaging(SPI),which requires multiple measurements.To reconstruct the image of a moving object with multiple motion mod...Motion blur restoration is essential for the imaging of moving objects,especially for single-pixel imaging(SPI),which requires multiple measurements.To reconstruct the image of a moving object with multiple motion modes,we propose a novel motion blur restoration method of SPI using geometric moment patterns.We design a novel localization method that uses normalized differential first-order moments and central moment patterns to determine the object's translational position and rotation angle information.Then,we perform motion compensation by using shifting Hadamard patterns.Our method effectively improves the detection accuracy of multiple motion modes and enhances the quality of the reconstructed image.We perform simulations and experiments,and the results validate the effectiveness of the proposed method.展开更多
This paper proposes a novel distributed control method for surrounding a noncooperative target that has maneuverability by spacecraft formation.A relative orbit error dynamic model between the target and the formation...This paper proposes a novel distributed control method for surrounding a noncooperative target that has maneuverability by spacecraft formation.A relative orbit error dynamic model between the target and the formation is established dependent on a reference spacecraft under the 2-body assumption.To estimate and compensate for the target’s control input rapidly,a novel finite-time extended state observer is developed.It is stable in the sense of fast finite-time uniformly ultimately bounded stability.A fast terminal sliding mode controller is proposed for finite-time convergence of the system.Simulation examples are implemented to show the effectiveness of proposed algorithm.展开更多
Underwater docking greatly facilitates and extends operation of an autonomous underwater vehicle(AUV) without the support of a surface vessel. Robust and accurate control is critically important for docking an AUV int...Underwater docking greatly facilitates and extends operation of an autonomous underwater vehicle(AUV) without the support of a surface vessel. Robust and accurate control is critically important for docking an AUV into a small underwater funneltype dock station. In this paper, a docking system with an under-actuated AUV is presented, with special attention paid to control algorithm design and implementation. For an under-actuated AUV, the cross-track error can be controlled only via vehicle heading modulation, so both the cross-track error and heading error have to be constrained to achieve successful docking operations, while the control problem can be even more complicated in practical scenarios with the presence of unknown ocean currents. To cope with the above issues, a control scheme of a three-hierarchy structure of control loops is developed, which has been embedded with online current estimator/compensator and effective control parameter tuning. The current estimator can evaluate both horizontal and vertical current velocity components, based only on the measurement of AUV's velocity relative to the ground; in contrast, most existing methods use the measurements of both AUV's velocities respectively relative to the ground and the water column. In addition to numerical simulation, the proposed docking scheme is fully implemented in a prototype AUV using MOOS-IvP architecture. Simulation results show that the current estimator/compensator works well even in the presence of lateral current disturbance. Finally, a series of sea trials are conducted to validate the current estimator/compensator and the whole docking system. The sea trial results show that our control methods can drive the AUV into the dock station effectively and robustly.展开更多
Wind power has been proven to have the ability to participate in the frequency modulation(FM)market.Using batteries to improve wind power stability can better aid wind farms participating in the FM market.Battery ener...Wind power has been proven to have the ability to participate in the frequency modulation(FM)market.Using batteries to improve wind power stability can better aid wind farms participating in the FM market.Battery energy storage system(BESS)has a promising future in applying regulation and load management in the power grid.For regulation services,normally,the regulation power prediction is estimated based on the required maximum regulation capacity;the power needed for the specific regulation service is unknown to the BESS owner.However,this information is needed in the regulation model when formulating the linearised BESS model with a constraint on the state of charge(SoC).This compromises the accuracy of the model greatly when it is applied for regulation service.Moreover,different control strategies can be employed by BESS.However,the current depth of discharge(DoD)based models have difficulties in being used in a linearization problem.Due to the consideration of the control strategy,the model becomes highly nonlinear and cannot be solved.In this paper,a charging rate(C-rate)based model is introduced,which can consider different control strategies of a BESS for cooperation with wind farms to participate in wind farm estimation error compensation,load management,energy bid,and regulation bid.First,the limitation of conventional BESS models are listed,and a new C-rate-based model is introduced.Then the C-rate-based BESS model is adopted in a wind farm and BESS cooperation scheme.Finally,experimental studies are carried out,and the DoD model and C-rate model optimization results are compared to prove the rationality of the C-rate model.展开更多
With the goal of achieving high stability and reliability to support underwater point-to-point communications and code division multiple access(CDMA) based underwater networks, a direct sequence spread spectrum based ...With the goal of achieving high stability and reliability to support underwater point-to-point communications and code division multiple access(CDMA) based underwater networks, a direct sequence spread spectrum based underwater acoustic communication system using dual spread spectrum code is proposed. To solve the contradictions between the information data rate and the accuracy of Doppler estimation, channel estimation, and frame synchronization, a data frame structure based on dual spread spectrum code is designed. A long spread spectrum code is used as the training sequence, which can be used for data frame detection and synchronization, Doppler estimation, and channel estimation. A short spread spectrum code is used to modulate the effective information data. A delay cross-correlation algorithm is used for Doppler estimation, and a correlation algorithm is used for channel estimation. For underwater networking, each user is assigned a different pair of spread spectrum codes. Simulation results show that the system has a good anti-multipath, anti-interference, and anti-Doppler performance, the bit error rate can be smaller than 10^(-6) when the signal-to-noise ratio is larger than-10 dB, the data rate can be as high as 355 bits/s, and the system can be used in the downlink of CDMA based networks.展开更多
基金National Science Fund for Distinguished Young Scholars (50825502)
文摘Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems. The tracking performance of the static loading is studied in this paper. Firstly, the nonlinear mathematical models of the hydraulic load simulator are derived, and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance. Considering the effect of the friction, a LuGre model based friction compensation is synthesized, in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded. The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter. Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy. The tracking performance is summarized by a derived theorem. Experimental results are also obtained to verify the high performance nature of the proposed control strategy.
基金supported in part by National Natural Science Foundation of China under Grant 52425505 and U22A20207in part by National Key R&D Program of China under Grant 2022YFB3403302in part by Zhejiang Provincial Key R&D Program of China under Grant 2023C01056.
文摘Thin-walled components possess high strength and lightweight characteristics;thus,they are widely used in aerospace,automotive,and other industrial felds.However,their low stifness makes them susceptible to deformation induced by cutting forces during machining,which leads to poor form accuracy.To address this issue,this paper proposes an in-process deformation estimation and compensation method.Because direct,accurate measurement of the deformation at the cutting point is challenging,the deformation is estimated based on the deformations measured at points in the uncut area along the same axial line as the cutting point.To establish the deformation relationship along the axial line for estimation,fnite element method simulations are conducted to generate axial deformation profles corresponding to diferent cutting force locations.Additionally,a calibration coefcient obtained through experiments is applied to enhance the accuracy of the deformation estimation.Then,the estimated deformation is fed into the control loop of the fast tool servo system to compensate for machining-induced deformation efectively.To validate the efectiveness of the proposed method,machining experiments on sinusoidal pit arrays and sinusoidal grid microstructures are performed.The experimental results demonstrate that the proposed method substantially improves machining accuracy.
文摘The effects of movement errors on imaging results of synthetic aperture sonar and the necessity of movement compensation are discussed. Based on analyzing so-called displaced phase center algorithm, an improved algorithm is proposed. In this method, the time delay is estimated firstly, then the phase is estimated for the residual error, so that the range of movement error suited to the algorithm is extended to some extent. Some simulation results on computer and experimental results in the test tank using the proposed algorithm are given as well.
基金supported by the National Natural Science Foundation of China(Grant Nos.61174121,61333005 and 61121003)the Ph.D Programs Foundations of the Ministry of Education China
文摘This paper deals with the problem of accelerometer error estimation and compensation for a three-axis gyro-stabilized camera mount. In a dynamic environment, the aircraft motion acceleration affects the accelerome ：er output and causes a degradation of attitude steady accuracy. In order to improve control accuracy, this paper proposes a proportional multiple-integral observer- based control strategy to estimate and compensate the accelerometer error. The basic idea of this paper is to approximate the error property by using a q-order polynomial function and extend the error and its derivatives as augmented states. Then a proportional multiple-integral observer is developed to estimate the error, with which the relationship between the error and the imbalance torque is formulated. The estimated value is compared to an angle threshold, the result of which is used to compen- sate the accelerometer output. Through static and vehicle-mounted experiments, it is demonstrated that compared with the tra- ditional method, the proposed method can improve the attitude steady accuracy effectively.
文摘Motion blur restoration is essential for the imaging of moving objects,especially for single-pixel imaging(SPI),which requires multiple measurements.To reconstruct the image of a moving object with multiple motion modes,we propose a novel motion blur restoration method of SPI using geometric moment patterns.We design a novel localization method that uses normalized differential first-order moments and central moment patterns to determine the object's translational position and rotation angle information.Then,we perform motion compensation by using shifting Hadamard patterns.Our method effectively improves the detection accuracy of multiple motion modes and enhances the quality of the reconstructed image.We perform simulations and experiments,and the results validate the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China(nos.62273118,12150008,61973100,and 61876050).
文摘This paper proposes a novel distributed control method for surrounding a noncooperative target that has maneuverability by spacecraft formation.A relative orbit error dynamic model between the target and the formation is established dependent on a reference spacecraft under the 2-body assumption.To estimate and compensate for the target’s control input rapidly,a novel finite-time extended state observer is developed.It is stable in the sense of fast finite-time uniformly ultimately bounded stability.A fast terminal sliding mode controller is proposed for finite-time convergence of the system.Simulation examples are implemented to show the effectiveness of proposed algorithm.
基金Project supported by the Zhejiang Provincial Natural Science Foundation(No.LY16F010007)the National High-Tech R&D Program of China(No.2013AA09A414)the Fundamental Research Funds for the Central Universities,China(No.2017QNA5009)
文摘Underwater docking greatly facilitates and extends operation of an autonomous underwater vehicle(AUV) without the support of a surface vessel. Robust and accurate control is critically important for docking an AUV into a small underwater funneltype dock station. In this paper, a docking system with an under-actuated AUV is presented, with special attention paid to control algorithm design and implementation. For an under-actuated AUV, the cross-track error can be controlled only via vehicle heading modulation, so both the cross-track error and heading error have to be constrained to achieve successful docking operations, while the control problem can be even more complicated in practical scenarios with the presence of unknown ocean currents. To cope with the above issues, a control scheme of a three-hierarchy structure of control loops is developed, which has been embedded with online current estimator/compensator and effective control parameter tuning. The current estimator can evaluate both horizontal and vertical current velocity components, based only on the measurement of AUV's velocity relative to the ground; in contrast, most existing methods use the measurements of both AUV's velocities respectively relative to the ground and the water column. In addition to numerical simulation, the proposed docking scheme is fully implemented in a prototype AUV using MOOS-IvP architecture. Simulation results show that the current estimator/compensator works well even in the presence of lateral current disturbance. Finally, a series of sea trials are conducted to validate the current estimator/compensator and the whole docking system. The sea trial results show that our control methods can drive the AUV into the dock station effectively and robustly.
文摘Wind power has been proven to have the ability to participate in the frequency modulation(FM)market.Using batteries to improve wind power stability can better aid wind farms participating in the FM market.Battery energy storage system(BESS)has a promising future in applying regulation and load management in the power grid.For regulation services,normally,the regulation power prediction is estimated based on the required maximum regulation capacity;the power needed for the specific regulation service is unknown to the BESS owner.However,this information is needed in the regulation model when formulating the linearised BESS model with a constraint on the state of charge(SoC).This compromises the accuracy of the model greatly when it is applied for regulation service.Moreover,different control strategies can be employed by BESS.However,the current depth of discharge(DoD)based models have difficulties in being used in a linearization problem.Due to the consideration of the control strategy,the model becomes highly nonlinear and cannot be solved.In this paper,a charging rate(C-rate)based model is introduced,which can consider different control strategies of a BESS for cooperation with wind farms to participate in wind farm estimation error compensation,load management,energy bid,and regulation bid.First,the limitation of conventional BESS models are listed,and a new C-rate-based model is introduced.Then the C-rate-based BESS model is adopted in a wind farm and BESS cooperation scheme.Finally,experimental studies are carried out,and the DoD model and C-rate model optimization results are compared to prove the rationality of the C-rate model.
基金Project supported by the National Natural Science Foundation of China(Nos.61431005,51409235,and 61401111)the Fundamental Research Funds for the Central Universities,China(No.201213004)
文摘With the goal of achieving high stability and reliability to support underwater point-to-point communications and code division multiple access(CDMA) based underwater networks, a direct sequence spread spectrum based underwater acoustic communication system using dual spread spectrum code is proposed. To solve the contradictions between the information data rate and the accuracy of Doppler estimation, channel estimation, and frame synchronization, a data frame structure based on dual spread spectrum code is designed. A long spread spectrum code is used as the training sequence, which can be used for data frame detection and synchronization, Doppler estimation, and channel estimation. A short spread spectrum code is used to modulate the effective information data. A delay cross-correlation algorithm is used for Doppler estimation, and a correlation algorithm is used for channel estimation. For underwater networking, each user is assigned a different pair of spread spectrum codes. Simulation results show that the system has a good anti-multipath, anti-interference, and anti-Doppler performance, the bit error rate can be smaller than 10^(-6) when the signal-to-noise ratio is larger than-10 dB, the data rate can be as high as 355 bits/s, and the system can be used in the downlink of CDMA based networks.
