A four-level atomic system with a closed interaction loop connected by two coherent driving fields and a microwave field is investigated. The results show that inversionless gain can be achieved on a higher frequency ...A four-level atomic system with a closed interaction loop connected by two coherent driving fields and a microwave field is investigated. The results show that inversionless gain can be achieved on a higher frequency transition outside the closed interaction loop, and the gain behaviour can be modulated by the phase of the closed loop as well as the amplitude of the microwave field. The phase sensitivity property in such a scheme is similar to that in an analogous configuration with spontaneously generated coherence, but it is beyond the rigorous condition of near-degenerate levels with non-orthogonal dipole moments. Therefore this scheme is much more convenient in experimental realization.展开更多
In the areas without terrestrial communication infrastructures,unmanned aerial vehicles(UAVs)can be utilized to serve field robots for mission-critical tasks.For this purpose,UAVs can be equipped with sensing,communic...In the areas without terrestrial communication infrastructures,unmanned aerial vehicles(UAVs)can be utilized to serve field robots for mission-critical tasks.For this purpose,UAVs can be equipped with sensing,communication,and computing modules to support various requirements of robots.In the task process,different modules assist the robots to perform tasks in a closed-loop way,which is referred to as a sensing-communication-computing-control(SC3)loop.In this work,we investigate a UAV-aided system containing multiple SC^(3)loops,which leverages non-orthogonal multiple access(NOMA)for efficient resource sharing.We describe and compare three different modelling levels for the SC^(3)loop.Based on the entropy SC^(3)loop model,a sum linear quadratic regulator(LQR)control cost minimization problem is formulated by optimizing the communication power.Further for the assure-to-be-stable case,we show that the original problem can be approximated by a modified user fairness problem,and accordingly gain more insights into the optimal solutions.Simulation results demonstrate the performance gain of using NOMA in such task-oriented systems,as well as the superiority of our proposed closed-loop-oriented design.展开更多
In recent years, the coal safety has been become the urgent problem in China,and severe and fatal coal mine accidents occurred frequently.Must pay attention to coal safety management immediately, because the coal mine...In recent years, the coal safety has been become the urgent problem in China,and severe and fatal coal mine accidents occurred frequently.Must pay attention to coal safety management immediately, because the coal mine accidents not only caused serious economic losses to the country and people but also had negative impact on the society and politics.A closed loop management system was put forward to build to improve the coal safety management.The closed loop management system was formed four parts,identifying the hazard sources, classifying the hidden troubles hazard sources, the risk prealarm and risk control, and the evaluation system.展开更多
Hydraulic systems provide a clean and stable supply of hydraulic fluid for subsea valves and actuators installed on the subsea bed in subsea production systems.Subsea control systems are used for contemporary subsea f...Hydraulic systems provide a clean and stable supply of hydraulic fluid for subsea valves and actuators installed on the subsea bed in subsea production systems.Subsea control systems are used for contemporary subsea fields instead of installing the control system on topside.Although all-electric subsea systems are state-of-the-art with benefits such as health,safety,and environment improvement,as well as efficiency and lower cost,hydraulic systems are still used for the development of many subsea fields.One of the main questions in the selection of a subsea hydraulic field is whether to choose an open or closed loop hydraulic system.The main characteristic of an open loop hydraulic system is that the hydraulic fluid is discharged into the marine environment during the actuation of the subsea valves.Conversely,the hydraulic fluid is returned to the topside facilities through an umbilical system in a closed loop system.Given that closed loop systems are more eco-friendly,the main question in this research is to examine the effect of the actuator connection of the closed loop system on actuator design.Two cases of actuated valves connected to a closed loop system are analyzed in this paper.The first is a 71/16-in.subsea slab gate valve in the pressure class of 517 bar with a linear spring return fail-safe close(FSC)actuator located on a manifold branch.The data indicates that the piston rod and cylinder diameter of the FSC linear actuator should be increased by some millimeters due to the accumulation of hydraulic oil at the bottom of the actuator.The hydraulic oil in the closed loop system helps in closing the actuator and spring force,so the spring constant and torque should be reduced as a result.The second case involves a 16-in.subsea ball valve in the pressure class of 517 bar with a double-acting fail-as-is rack and pinion actuator.The conclusion in this case is to avoid making any change in the design of double-acting actuator in connection to the closed loop system.展开更多
Objective： This study aimed to develop and apply a closed-loop medication administration system in a hospital in order to reduce medication administration errors （MAEs）.Methods： The study was imple...Objective： This study aimed to develop and apply a closed-loop medication administration system in a hospital in order to reduce medication administration errors （MAEs）.Methods： The study was implemented in four pilot general wards. We used a before-and-after design to collect oral medication administration times before and after the implementation of the closed-loop medication administration system, evaluated MAE alert logs after the intervention, and conducted a survey of the nurses1 satisfaction with the system in the pilot wards.Results： （a） Nursing time of oral medication administration： before the adoption of the closed-loop medication administration system, the average nursing time was 31.56 ± 10.88 minutes （n = 78）; after the adoption of the system, the time was 18.74 ± 5.60 minutes （n = 54）. Independent sample Mests showed a significant difference between two groups（t= 8.85, P 〈0.00）. （b） Degree of nurses’ satisfaction with the closed-loop medication administration system： 60.00% （n = 42） of nurses considered the system to be helpful for their work and nearly half of the nurses （47.14%, n = 33） believed that the system could facilitate clinical work and reduce workload; 51.43% {n = 36） believed that the system could reduce checking time and enhance work efficiency; 82.86% （n = 58） believed that the system was helpful in improving checking accuracy to reduce MAEs and ensure patient safety. More than 60% of the nurses considered the system to be a method that could help to track MAEs to improve nursing quality, （c） The MAE alert logs during observation period： it revealed only 27 alerts from the repeated scans of 3,428 instances of medication administration.Conclusions： The nurses were satisfied with the closed-loop medication administration system because it improved their work efficiency and reduced their workload. The current investigation was limited by time; therefore, further research is needed to more closely examine the relationship between the system and MAEs.展开更多
The classical washout algorithm had fixed gains and manually constructed filters, so that it led to poor adaptability. Furthermore, it lost the sustained acceleration cues of high-and mid-frequency in cross-over(tilt-...The classical washout algorithm had fixed gains and manually constructed filters, so that it led to poor adaptability. Furthermore, it lost the sustained acceleration cues of high-and mid-frequency in cross-over(tilt-coordination) channel, and the acceleration of cross-over frequency was also limited by angular velocity limiter, so the false cues in flight simulation process were clearly perceived by pilots. The paper studied the characteristics of the classical washout algorithm and flight simulator motion platform, tried to redesign the source of cross-over acceleration channel and translation acceleration channel, and transferred the part of cross-over acceleration that was unsimulated sustained acceleration to translation acceleration channel. Comparisons were mainly made between classical washout algorithm and revised algorithm in a longitudinal/pitch direction. The evaluation was based on the implementation of human vestibular perception system. The results demonstrated that the revised algorithm could significantly reduce the phase lag, and improved the spikes tracking performance. Furthermore, sensory angular velocity and the error of sensory acceleration were strictly controlled within the threshold of human perception system, and the displacement was a little broader than the classical washout algorithm. Therefore, it was proved that the new algorithm could diminish the filters parameters and heighten the self-adaptability for the washout algorithm. In addition, the magnitude of false cues was remarkably reduced during flight simulator, and the workspace utilization of the motion platform was developed by "closed-loop" control system.展开更多
Fuel cells and electrolysis are promising candidates for future energy production from renewable energy sources. Usually, polymer electrolyte fuel cell systems run on hydrogen and air, while the most of electrolysis s...Fuel cells and electrolysis are promising candidates for future energy production from renewable energy sources. Usually, polymer electrolyte fuel cell systems run on hydrogen and air, while the most of electrolysis systems vent out oxygen as unused by-product. Replacing air with pure oxygen, fuel cell electrochemical performance, durability and system efficiency can be significantly increased with a further overall system simplification and increased reliability. This work, which represents the initial step for pure H;/O;polymer electrolyte fuel cell operation in closed-loop systems, focuses on performance validation of a single cell operating with pure H;/O;under different relative humidity（RH） levels, reactants stoichiometry conditions and temperature. As a result of this study, the most convenient and appropriate operative conditions for a polymer electrolyte fuel cell stack integrated in a closed loop system were selected.展开更多
Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback co...Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.展开更多
Objective： To evaluate the efficiency of an implanted chip system for the control of heart rate （HR）. Methods： The HR was recorded in six conscious Sprague-Dawley （SD） rats. An implanted chip system was designed...Objective： To evaluate the efficiency of an implanted chip system for the control of heart rate （HR）. Methods： The HR was recorded in six conscious Sprague-Dawley （SD） rats. An implanted chip system was designed to regulate the HR by stimulating the right cervical vagus nerve according to the feedback of real time HR. Each rat was subjected to 30-min regulation and 30-min recovery. The change of HR during the regulation period was compared with the control. The ECG was recorded during the experiment for 24 h. Results： The ECG signals were successfully recorded during the experiment. The HR was significantly decreased during the period of regulation compared with control （-79.3 ± 34.5, P 〈 0.01, n = 6） and then recovered to normal after regulation. Conclusion： The described implanted chip system can regulate the HR to a designated set point.展开更多
The existing theories for closed loop identification with the linear feedback controller are very mature.To apply the existed theories directly in the control field,we propose a new idea about replacing the original u...The existing theories for closed loop identification with the linear feedback controller are very mature.To apply the existed theories directly in the control field,we propose a new idea about replacing the original unknown and nonlinear feedback controller with one approximated linear controller,while guaranteeing the equivalent property for the obtained closed loop system.Based on some statistical correlation functions,one condition is derived to show the equivalent property between the approximated linear controller and the original nonlinear controller.The detailed explicit form,corresponding to the approximated linear controller,is also constructed.Furthermore,to give a complete analysis for closed loop identification,the cost function is rewritten as one extended expression,being convenient to understand.Then spectral estimation is introduced to identify the unknown plant in the closed loop system.Finally,the proposed theories are verified by one simulation example.展开更多
In order to study the factors that influence the air fuel ratio(A/F), the amplitude and frequency of A/F fluctuation, to reform the control strategy, and to improve the efficiency of three way catalyst(TWC), a model...In order to study the factors that influence the air fuel ratio(A/F), the amplitude and frequency of A/F fluctuation, to reform the control strategy, and to improve the efficiency of three way catalyst(TWC), a model of closed loop control system including the engine, air fuel mixing and transportation, oxygen sensor and controller, etc., is developed. Various factors that influence the A/F control are studied by simulation. The simulation results show that the reference voltage of oxygen sensor will influence the mean value of A/F ratio, the controller parameters will influence the amplitude of A/F fluctuation, and the operating conditions of the engine determine the frequency of A/F fluctuations, the amplitude of A/F fluctuation can be reduced to within demanded values by logical selection of the signal acquisition method and controller parameters. Higher A/F fluctuation frequency under high speed and load can be reduced through software delay in the controller. The A/F closed loop control system based on the simulation results, accompanied with a rare earth element TWC, gives a better efficiency of conversion against harmful emissions.展开更多
We study the entanglement of dressed atom and its spontaneous emission in a three-level A-type closed-loop atomic system in a multi-photon resonance condition and beyond it. It is shown that the von Neumann entropy in...We study the entanglement of dressed atom and its spontaneous emission in a three-level A-type closed-loop atomic system in a multi-photon resonance condition and beyond it. It is shown that the von Neumann entropy in such a system is phase-dependent, and it can be controlled by either the intensity or relative phase of applied fields. It is demonstrated that for the special case of the Rabi frequency of applied fields, the system is disentangled. In addition, we take into account the effect of Doppler broadening on the entanglement and it is found that a suitable choice of laser propagation direction allows us to obtain the steady state degree of entanglement （DEM） even in the presence of the Doppler effect.展开更多
A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more infor...A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more information about the plant structure. Using general least squares method （GLS） the plant over-sampled model should be recognized. Then the original plant model should be obtained by its relationship with the over-sampled model. Compared with conventional approaches the advantage of the new method is that even if the ordinary identifiability conditions are not satisfied, a close-loop system can be identified by using the oversampled output without utilizing any external test signal. Accuracy analysis shows the relationship between the estimation error and the over-sampling rate. Numerical simulation illnstrates its effectiveness.展开更多
The response simulation is studied and the steering safety is evaluated by using finer integration method for driver vehicle closed loop system with stationary random road input.This algorithm not only is precise, b...The response simulation is studied and the steering safety is evaluated by using finer integration method for driver vehicle closed loop system with stationary random road input.This algorithm not only is precise, but also can shorten the evaluation period of steering safety and reduce the tremendous cost for real vehicle testing.The response simulation and the vehicle steering safety evaluation are also studied for the closed loop system with evolutionary random road input.The study can more truly evaluate vehicle driving for including the slowly varying of vehicle velocity with time.展开更多
By use of the recursive formulation of flexible multibody system with closed loops,this paper studies the dynamic simulation of complicated multibody system.The conception of static correction modes in structural dyna...By use of the recursive formulation of flexible multibody system with closed loops,this paper studies the dynamic simulation of complicated multibody system.The conception of static correction modes in structural dynamics is introduced to present the local deformation effects due to reaction forces at kinematic joints.A space four bar mechanism is utilized here as an example to describe the method of selecting static correction modes.Compared with vibration normal modes, static correction modes are demonstrated to be effective in numerical simulation.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
This paper presents a novel four degrees of freedom(DOF) parallel mechanism with the closed-loop limbs, which includes two translational(2 T) DOF and two rotational(2 R) DOF. By connecting the proposed parallel mechan...This paper presents a novel four degrees of freedom(DOF) parallel mechanism with the closed-loop limbs, which includes two translational(2 T) DOF and two rotational(2 R) DOF. By connecting the proposed parallel mechanism with the guide rail in series,the 5-DOF hybrid robot system is obtained, which can be applied for the composite material tape laying in aerospace industry. The analysis in this paper mainly focuses on the parallel module of the hybrid robot system. First, the freedom of the proposed parallel mechanism is calculated based on the screw theory. Then, according to the closed-loop vector equation, the inverse kinematics and Jacobian matrix of the parallel mechanism are carried out. Next, the workspace stiffness and dexterity analysis of the parallel mechanism are investigated based on the constraint equations, static stiffness matrix and Jacobian condition number. Finally, the correctness of the inverse kinematics and the high stiffness of the parallel mechanism are verified by the kinematics and stiffness simulation analysis, which lays a foundation for the automatic composite material tape laying.展开更多
The existing kinematic parameter calibration method cannot further improve the absolute positioning accuracy of the robot due to the uncertainty of positioning error caused by robot joint backlash.In view of this prob...The existing kinematic parameter calibration method cannot further improve the absolute positioning accuracy of the robot due to the uncertainty of positioning error caused by robot joint backlash.In view of this problem,a closed‑loop feedback accuracy compensation method for robot joints was proposed.Firstly,a Chebyshev polynomial error estimation model was established which took geometric error and non‑geometric error into account.In addition,the absolute linear grating scale was installed at each joint of the robot and the positioning error of the robot end was mapped to the joint angle.And the joint angle corrected value was obtained.Furthermore,the closed‑loop feedback of robot joints was established to realize the online correction of the positioning error.Finally,an experiment on the KUKA KR210 industrial robot was conducted to demonstrate the effectiveness of the method.The result shows that the maximum absolute positioning error of the robot is reduced by 75%from 0.76 mm to 0.19 mm.This method can compensate the robot joint backlash effectively and further improve the absolute positioning accuracy of the robot.展开更多
This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section （2 × 2 mm^2, 165 mm long） machined directly on an aluminum...This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section （2 × 2 mm^2, 165 mm long） machined directly on an aluminum plate（180×120×3 nm^2）, which was covered by a transparent plate. The working fluid employed was ethanol. As the results, the influence parameters of thermal performance were investigated, such as filling ratio, heat load and operational orientations etc. Filling ratio was found to be a critical parameter, and its effect was rather complicated. According to its values the PHP plate could have four distinct working zones with different operational characteristics and heat transfer performance. The effect of heat load on thermal performance was found to be positive, and in general, iucrcasing the heat load would improve heat transfer performance. In order to analyze the effect of gravity on thermal performance, three different heat modes and total seven tilt angles were tested and compared. Successful operation at all orientations with respect to gravity was also achieved.展开更多
基金Project supported by the Natural Science Foundation of Guangdong Province （Grant No 05301018）, the Research and Development Fund of Shenzhen University, China （Grant No 200549）, and the National Natural Science Foundation of China （Grant Nos 10334010 and 10404009）.
文摘A four-level atomic system with a closed interaction loop connected by two coherent driving fields and a microwave field is investigated. The results show that inversionless gain can be achieved on a higher frequency transition outside the closed interaction loop, and the gain behaviour can be modulated by the phase of the closed loop as well as the amplitude of the microwave field. The phase sensitivity property in such a scheme is similar to that in an analogous configuration with spontaneously generated coherence, but it is beyond the rigorous condition of near-degenerate levels with non-orthogonal dipole moments. Therefore this scheme is much more convenient in experimental realization.
基金supported in part by the National Key Research and Development Program of China under Grant 2020YFA0711301in part by the National Natural Science Foundation of China under Grant 62341110, Grant U22A2002, and Grant 62025110in part by the Suzhou Science and Technology Project
文摘In the areas without terrestrial communication infrastructures,unmanned aerial vehicles(UAVs)can be utilized to serve field robots for mission-critical tasks.For this purpose,UAVs can be equipped with sensing,communication,and computing modules to support various requirements of robots.In the task process,different modules assist the robots to perform tasks in a closed-loop way,which is referred to as a sensing-communication-computing-control(SC3)loop.In this work,we investigate a UAV-aided system containing multiple SC^(3)loops,which leverages non-orthogonal multiple access(NOMA)for efficient resource sharing.We describe and compare three different modelling levels for the SC^(3)loop.Based on the entropy SC^(3)loop model,a sum linear quadratic regulator(LQR)control cost minimization problem is formulated by optimizing the communication power.Further for the assure-to-be-stable case,we show that the original problem can be approximated by a modified user fairness problem,and accordingly gain more insights into the optimal solutions.Simulation results demonstrate the performance gain of using NOMA in such task-oriented systems,as well as the superiority of our proposed closed-loop-oriented design.
基金Supported by the Research Fund for the Doctoral Program of Higher Education of China(20090095110001)the Ministry of Education Humanities and Social Science(08JA630083)
文摘In recent years, the coal safety has been become the urgent problem in China,and severe and fatal coal mine accidents occurred frequently.Must pay attention to coal safety management immediately, because the coal mine accidents not only caused serious economic losses to the country and people but also had negative impact on the society and politics.A closed loop management system was put forward to build to improve the coal safety management.The closed loop management system was formed four parts,identifying the hazard sources, classifying the hidden troubles hazard sources, the risk prealarm and risk control, and the evaluation system.
文摘Hydraulic systems provide a clean and stable supply of hydraulic fluid for subsea valves and actuators installed on the subsea bed in subsea production systems.Subsea control systems are used for contemporary subsea fields instead of installing the control system on topside.Although all-electric subsea systems are state-of-the-art with benefits such as health,safety,and environment improvement,as well as efficiency and lower cost,hydraulic systems are still used for the development of many subsea fields.One of the main questions in the selection of a subsea hydraulic field is whether to choose an open or closed loop hydraulic system.The main characteristic of an open loop hydraulic system is that the hydraulic fluid is discharged into the marine environment during the actuation of the subsea valves.Conversely,the hydraulic fluid is returned to the topside facilities through an umbilical system in a closed loop system.Given that closed loop systems are more eco-friendly,the main question in this research is to examine the effect of the actuator connection of the closed loop system on actuator design.Two cases of actuated valves connected to a closed loop system are analyzed in this paper.The first is a 71/16-in.subsea slab gate valve in the pressure class of 517 bar with a linear spring return fail-safe close(FSC)actuator located on a manifold branch.The data indicates that the piston rod and cylinder diameter of the FSC linear actuator should be increased by some millimeters due to the accumulation of hydraulic oil at the bottom of the actuator.The hydraulic oil in the closed loop system helps in closing the actuator and spring force,so the spring constant and torque should be reduced as a result.The second case involves a 16-in.subsea ball valve in the pressure class of 517 bar with a double-acting fail-as-is rack and pinion actuator.The conclusion in this case is to avoid making any change in the design of double-acting actuator in connection to the closed loop system.
基金supported by Health and Family Planning Commission of Shenzhen Municipality,Scientific Research Foundation(2015),No.31(No.201504004)
文摘Objective： This study aimed to develop and apply a closed-loop medication administration system in a hospital in order to reduce medication administration errors （MAEs）.Methods： The study was implemented in four pilot general wards. We used a before-and-after design to collect oral medication administration times before and after the implementation of the closed-loop medication administration system, evaluated MAE alert logs after the intervention, and conducted a survey of the nurses1 satisfaction with the system in the pilot wards.Results： （a） Nursing time of oral medication administration： before the adoption of the closed-loop medication administration system, the average nursing time was 31.56 ± 10.88 minutes （n = 78）; after the adoption of the system, the time was 18.74 ± 5.60 minutes （n = 54）. Independent sample Mests showed a significant difference between two groups（t= 8.85, P 〈0.00）. （b） Degree of nurses’ satisfaction with the closed-loop medication administration system： 60.00% （n = 42） of nurses considered the system to be helpful for their work and nearly half of the nurses （47.14%, n = 33） believed that the system could facilitate clinical work and reduce workload; 51.43% {n = 36） believed that the system could reduce checking time and enhance work efficiency; 82.86% （n = 58） believed that the system was helpful in improving checking accuracy to reduce MAEs and ensure patient safety. More than 60% of the nurses considered the system to be a method that could help to track MAEs to improve nursing quality, （c） The MAE alert logs during observation period： it revealed only 27 alerts from the repeated scans of 3,428 instances of medication administration.Conclusions： The nurses were satisfied with the closed-loop medication administration system because it improved their work efficiency and reduced their workload. The current investigation was limited by time; therefore, further research is needed to more closely examine the relationship between the system and MAEs.
基金Supported by Wuhan Technical College of Communications Fund(Q2018001)China Institute of Communications Education Fund(1602-248)Wuhan Technical College of Communications Innovation Team(CX2018A07)
文摘The classical washout algorithm had fixed gains and manually constructed filters, so that it led to poor adaptability. Furthermore, it lost the sustained acceleration cues of high-and mid-frequency in cross-over(tilt-coordination) channel, and the acceleration of cross-over frequency was also limited by angular velocity limiter, so the false cues in flight simulation process were clearly perceived by pilots. The paper studied the characteristics of the classical washout algorithm and flight simulator motion platform, tried to redesign the source of cross-over acceleration channel and translation acceleration channel, and transferred the part of cross-over acceleration that was unsimulated sustained acceleration to translation acceleration channel. Comparisons were mainly made between classical washout algorithm and revised algorithm in a longitudinal/pitch direction. The evaluation was based on the implementation of human vestibular perception system. The results demonstrated that the revised algorithm could significantly reduce the phase lag, and improved the spikes tracking performance. Furthermore, sensory angular velocity and the error of sensory acceleration were strictly controlled within the threshold of human perception system, and the displacement was a little broader than the classical washout algorithm. Therefore, it was proved that the new algorithm could diminish the filters parameters and heighten the self-adaptability for the washout algorithm. In addition, the magnitude of false cues was remarkably reduced during flight simulator, and the workspace utilization of the motion platform was developed by "closed-loop" control system.
文摘Fuel cells and electrolysis are promising candidates for future energy production from renewable energy sources. Usually, polymer electrolyte fuel cell systems run on hydrogen and air, while the most of electrolysis systems vent out oxygen as unused by-product. Replacing air with pure oxygen, fuel cell electrochemical performance, durability and system efficiency can be significantly increased with a further overall system simplification and increased reliability. This work, which represents the initial step for pure H;/O;polymer electrolyte fuel cell operation in closed-loop systems, focuses on performance validation of a single cell operating with pure H;/O;under different relative humidity（RH） levels, reactants stoichiometry conditions and temperature. As a result of this study, the most convenient and appropriate operative conditions for a polymer electrolyte fuel cell stack integrated in a closed loop system were selected.
基金supported by the National Natural Science Foundation of China(Grant No.U2230207)。
文摘Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.
基金supported by grant from National Nature Science Found (30670767)
文摘Objective： To evaluate the efficiency of an implanted chip system for the control of heart rate （HR）. Methods： The HR was recorded in six conscious Sprague-Dawley （SD） rats. An implanted chip system was designed to regulate the HR by stimulating the right cervical vagus nerve according to the feedback of real time HR. Each rat was subjected to 30-min regulation and 30-min recovery. The change of HR during the regulation period was compared with the control. The ECG was recorded during the experiment for 24 h. Results： The ECG signals were successfully recorded during the experiment. The HR was significantly decreased during the period of regulation compared with control （-79.3 ± 34.5, P 〈 0.01, n = 6） and then recovered to normal after regulation. Conclusion： The described implanted chip system can regulate the HR to a designated set point.
文摘The existing theories for closed loop identification with the linear feedback controller are very mature.To apply the existed theories directly in the control field,we propose a new idea about replacing the original unknown and nonlinear feedback controller with one approximated linear controller,while guaranteeing the equivalent property for the obtained closed loop system.Based on some statistical correlation functions,one condition is derived to show the equivalent property between the approximated linear controller and the original nonlinear controller.The detailed explicit form,corresponding to the approximated linear controller,is also constructed.Furthermore,to give a complete analysis for closed loop identification,the cost function is rewritten as one extended expression,being convenient to understand.Then spectral estimation is introduced to identify the unknown plant in the closed loop system.Finally,the proposed theories are verified by one simulation example.
文摘In order to study the factors that influence the air fuel ratio(A/F), the amplitude and frequency of A/F fluctuation, to reform the control strategy, and to improve the efficiency of three way catalyst(TWC), a model of closed loop control system including the engine, air fuel mixing and transportation, oxygen sensor and controller, etc., is developed. Various factors that influence the A/F control are studied by simulation. The simulation results show that the reference voltage of oxygen sensor will influence the mean value of A/F ratio, the controller parameters will influence the amplitude of A/F fluctuation, and the operating conditions of the engine determine the frequency of A/F fluctuations, the amplitude of A/F fluctuation can be reduced to within demanded values by logical selection of the signal acquisition method and controller parameters. Higher A/F fluctuation frequency under high speed and load can be reduced through software delay in the controller. The A/F closed loop control system based on the simulation results, accompanied with a rare earth element TWC, gives a better efficiency of conversion against harmful emissions.
文摘We study the entanglement of dressed atom and its spontaneous emission in a three-level A-type closed-loop atomic system in a multi-photon resonance condition and beyond it. It is shown that the von Neumann entropy in such a system is phase-dependent, and it can be controlled by either the intensity or relative phase of applied fields. It is demonstrated that for the special case of the Rabi frequency of applied fields, the system is disentangled. In addition, we take into account the effect of Doppler broadening on the entanglement and it is found that a suitable choice of laser propagation direction allows us to obtain the steady state degree of entanglement （DEM） even in the presence of the Doppler effect.
基金Project supported by National Natural Science Foundation ofChina (Grant No .60174030)
文摘A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more information about the plant structure. Using general least squares method （GLS） the plant over-sampled model should be recognized. Then the original plant model should be obtained by its relationship with the over-sampled model. Compared with conventional approaches the advantage of the new method is that even if the ordinary identifiability conditions are not satisfied, a close-loop system can be identified by using the oversampled output without utilizing any external test signal. Accuracy analysis shows the relationship between the estimation error and the over-sampling rate. Numerical simulation illnstrates its effectiveness.
文摘The response simulation is studied and the steering safety is evaluated by using finer integration method for driver vehicle closed loop system with stationary random road input.This algorithm not only is precise, but also can shorten the evaluation period of steering safety and reduce the tremendous cost for real vehicle testing.The response simulation and the vehicle steering safety evaluation are also studied for the closed loop system with evolutionary random road input.The study can more truly evaluate vehicle driving for including the slowly varying of vehicle velocity with time.
文摘By use of the recursive formulation of flexible multibody system with closed loops,this paper studies the dynamic simulation of complicated multibody system.The conception of static correction modes in structural dynamics is introduced to present the local deformation effects due to reaction forces at kinematic joints.A space four bar mechanism is utilized here as an example to describe the method of selecting static correction modes.Compared with vibration normal modes, static correction modes are demonstrated to be effective in numerical simulation.
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by Fundamental Research Funds for the Central Universities(No.2018JBZ007).
文摘This paper presents a novel four degrees of freedom(DOF) parallel mechanism with the closed-loop limbs, which includes two translational(2 T) DOF and two rotational(2 R) DOF. By connecting the proposed parallel mechanism with the guide rail in series,the 5-DOF hybrid robot system is obtained, which can be applied for the composite material tape laying in aerospace industry. The analysis in this paper mainly focuses on the parallel module of the hybrid robot system. First, the freedom of the proposed parallel mechanism is calculated based on the screw theory. Then, according to the closed-loop vector equation, the inverse kinematics and Jacobian matrix of the parallel mechanism are carried out. Next, the workspace stiffness and dexterity analysis of the parallel mechanism are investigated based on the constraint equations, static stiffness matrix and Jacobian condition number. Finally, the correctness of the inverse kinematics and the high stiffness of the parallel mechanism are verified by the kinematics and stiffness simulation analysis, which lays a foundation for the automatic composite material tape laying.
基金supported by the National Natural Science Foundation of China(Nos.51875287, 52075250)the Special Fund for Transformation of Scientific,and Technological Achievements of Jiangsu Province(No.BA2018053)
文摘The existing kinematic parameter calibration method cannot further improve the absolute positioning accuracy of the robot due to the uncertainty of positioning error caused by robot joint backlash.In view of this problem,a closed‑loop feedback accuracy compensation method for robot joints was proposed.Firstly,a Chebyshev polynomial error estimation model was established which took geometric error and non‑geometric error into account.In addition,the absolute linear grating scale was installed at each joint of the robot and the positioning error of the robot end was mapped to the joint angle.And the joint angle corrected value was obtained.Furthermore,the closed‑loop feedback of robot joints was established to realize the online correction of the positioning error.Finally,an experiment on the KUKA KR210 industrial robot was conducted to demonstrate the effectiveness of the method.The result shows that the maximum absolute positioning error of the robot is reduced by 75%from 0.76 mm to 0.19 mm.This method can compensate the robot joint backlash effectively and further improve the absolute positioning accuracy of the robot.
基金Supported by the Ger man National Science Foundation (DFG)(No. GR412/33)
文摘This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section （2 × 2 mm^2, 165 mm long） machined directly on an aluminum plate（180×120×3 nm^2）, which was covered by a transparent plate. The working fluid employed was ethanol. As the results, the influence parameters of thermal performance were investigated, such as filling ratio, heat load and operational orientations etc. Filling ratio was found to be a critical parameter, and its effect was rather complicated. According to its values the PHP plate could have four distinct working zones with different operational characteristics and heat transfer performance. The effect of heat load on thermal performance was found to be positive, and in general, iucrcasing the heat load would improve heat transfer performance. In order to analyze the effect of gravity on thermal performance, three different heat modes and total seven tilt angles were tested and compared. Successful operation at all orientations with respect to gravity was also achieved.
