The graded density impactor(GDI)dynamic loading technique is crucial for acquiring the dynamic physical property parameters of materials used in weapons.The accuracy and timeliness of GDI structural design are key to ...The graded density impactor(GDI)dynamic loading technique is crucial for acquiring the dynamic physical property parameters of materials used in weapons.The accuracy and timeliness of GDI structural design are key to achieving controllable stress-strain rate loading.In this study,we have,for the first time,combined one-dimensional fluid computational software with machine learning methods.We first elucidated the mechanisms by which GDI structures control stress and strain rates.Subsequently,we constructed a machine learning model to create a structure-property response surface.The results show that altering the loading velocity and interlayer thickness has a pronounced regulatory effect on stress and strain rates.In contrast,the impedance distribution index and target thickness have less significant effects on stress regulation,although there is a matching relationship between target thickness and interlayer thickness.Compared with traditional design methods,the machine learning approach offers a10^(4)—10^(5)times increase in efficiency and the potential to achieve a global optimum,holding promise for guiding the design of GDI.展开更多
Considering the challenges posed by external disturbances on carrier-based aircraft land-ing control,higher demands are required for the precision and convergence of the carrier landingcontrol system.First,this paper ...Considering the challenges posed by external disturbances on carrier-based aircraft land-ing control,higher demands are required for the precision and convergence of the carrier landingcontrol system.First,this paper proposes an Adaptive Terminal Sliding Combined Super TwistingControl(ATS-STC)method to address the issues of low precision,slow convergence,and poor dis-turbance rejection capability resulting from external disturbances,such as carrier air-wake and deckmotion.By introducing a nonlinear term into the sliding surface and employing an integralapproach,the proposed ATS-STC method can ensure finite-time convergence and mitigate the chat-tering problem.An adaptive law is also utilized to estimate the external disturbances,therebyenhancing the anti-disturbance performance.Then,the stability and convergence time analysis ofthe designed controller are conducted.Based on the proposed method,an Automatic Carrier Land-ing System(ACLS)is developed to perform the carrier landing control task.Furthermore,a multi-dimensional validation is carried out.For the numerical simulation test,the Terminal Sliding ModeControl(TSMC)method and Proportion Integration Differentiation(PID)method are introducedas comparison,the quantitative assessment results show that the tracking error of TSMC and PIDcan reach 1.5 times and 2 times that of the proposed method.Finally,the Hardware-in-the-Loop(HIL)test and real flight test are conducted.All the experimental results demonstrate that the pro-posed control method is more effective and precise.展开更多
Addressing the issue of excessive cavitation pressure fluctuation on the propeller behind a catamaran,numerical simulation is conducted to assess the quality of the wake flow and to numerically predict the pressure fl...Addressing the issue of excessive cavitation pressure fluctuation on the propeller behind a catamaran,numerical simulation is conducted to assess the quality of the wake flow and to numerically predict the pressure fluctuation induced by the propeller cavitation.Additionally,the interaction between the wake vortex field and the propeller is investigated,revealing the presence of propeller-hull vortex.To improve the propeller's inflow quality,the impact of vortex generators on the wake flow and pressure fluctuation is numerically simulated.Then,numerical simulations are conducted to compare the cavitation pressure fluctuation of optimized propeller design,evaluating the effects of vortex generators at different spatial locations and angles of attack,to determine the optimal vortex generator scheme.A more comprehensive integrated control plan for the wake flow and the cavitation pressure fluctuation of the propeller behind the catamaran is finally formed.展开更多
Accurate skin temperature is one of the critical factors in successfully assimilating satellite radiance data over land.However,model-simulated skin temperature may not be accurate enough.To address this issue,an exte...Accurate skin temperature is one of the critical factors in successfully assimilating satellite radiance data over land.However,model-simulated skin temperature may not be accurate enough.To address this issue,an extended skin temperature control variable(TSCV) approach is proposed in a variational assimilation framework,which also considers the background error correlation between skin temperature and atmospheric variables.A series of single observation tests and a 10-day cycling assimilation experiment were conducted to evaluate the impact of the TSCV approach on the assimilation of AMSU-A and ATMS(Advanced Technology Microwave Sounder) microwave temperature-sounding channels over land.The results of the single observation tests show that by applying the TSCV approach,not only the direct analysis of skin temperature is realized,but also the interaction between skin temperature and atmospheric variables can be achieved during the assimilation process.The results of the cycling experiment demonstrate that the TSCV approach improves the skin temperature analysis,which in turn reduces the RMSE of the surface variables and low-level air temperature forecasts.The TSCV approach also reduces the difference between the observed and simulated brightness temperatures of both microwave and infrared window channels over land,suggesting that the approach can facilitate the radiance simulation of these channels,thus contributing to the assimilation of window channels.展开更多
The core of computer numerical control(CNC) machine tool is the electrical system which controls and coordinates every part of CNC machine tool to complete processing tasks, so it is of great significance to strengthe...The core of computer numerical control(CNC) machine tool is the electrical system which controls and coordinates every part of CNC machine tool to complete processing tasks, so it is of great significance to strengthen the reliability of the electrical system. However, the electrical system is very complex due to many uncertain factors and dynamic stochastic characteristics when failure occurs. Therefore, the traditional fault tree analysis(FTA) method is not applicable. Bayesian network(BN) not only has a unique advantage to analyze nodes with multiply states in reliability analysis for complex systems, but also can solve the state explosion problem properly caused by Markov model when dealing with dynamic fault tree(DFT). In addition, the forward causal reasoning of BN can get the conditional probability distribution of the system under considering the uncertainty;the backward diagnosis reasoning of BN can recognize the weak links in system, so it is valuable for improving the system reliability.展开更多
In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign met...In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.展开更多
A component-based model integration framework for computer numerical control system design and development is presented.The model integrates modeling,simulation,verification and implementation in a uniform environment...A component-based model integration framework for computer numerical control system design and development is presented.The model integrates modeling,simulation,verification and implementation in a uniform environment.The computer numerical control(CNC) modeling language with well defined syntax and unambiguous semantics is developed.Using the proposed CNC model integration method,a three axis milling system model is developed in the case study.The approach is an attempt to create an infrastructure to support the CNC system design in an efficient way,while at the same time guarantees the function and performance requirements with advanced capability of the system such as modularity,flexibility,reusability,etc.展开更多
A 5-axis controller with curve interpolation function is developed to satisfy high-speed and high-precision computer numerical control (CNC) machining of machine parts with complex shapes in the authors-devised open C...A 5-axis controller with curve interpolation function is developed to satisfy high-speed and high-precision computer numerical control (CNC) machining of machine parts with complex shapes in the authors-devised open CNC system. The instruction for- mat of this interpolation method and the generation procedure of the numerical control (NC) files are introduced. The interpola- tion curves of both position vectors and orientation vectors constructed by the controller are C2 continuous and independent of machin...展开更多
In this paper,an intelligent control method applying on numerical virtual flight is proposed.The proposed algorithm is verified and evaluated by combining with the case of the basic finner projectile model and shows a...In this paper,an intelligent control method applying on numerical virtual flight is proposed.The proposed algorithm is verified and evaluated by combining with the case of the basic finner projectile model and shows a good application prospect.Firstly,a numerical virtual flight simulation model based on overlapping dynamic mesh technology is constructed.In order to verify the accuracy of the dynamic grid technology and the calculation of unsteady flow,a numerical simulation of the basic finner projectile without control is carried out.The simulation results are in good agreement with the experiment data which shows that the algorithm used in this paper can also be used in the design and evaluation of the intelligent controller in the numerical virtual flight simulation.Secondly,combined with the real-time control requirements of aerodynamic,attitude and displacement parameters of the projectile during the flight process,the numerical simulations of the basic finner projectile’s pitch channel are carried out under the traditional PID(Proportional-Integral-Derivative)control strategy and the intelligent PID control strategy respectively.The intelligent PID controller based on BP(Back Propagation)neural network can realize online learning and self-optimization of control parameters according to the acquired real-time flight parameters.Compared with the traditional PID controller,the concerned control variable overshoot,rise time,transition time and steady state error and other performance indicators have been greatly improved,and the higher the learning efficiency or the inertia coefficient,the faster the system,the larger the overshoot,and the smaller the stability error.The intelligent control method applying on numerical virtual flight is capable of solving the complicated unsteady motion and flow with the intelligent PID control strategy and has a strong promotion to engineering application.展开更多
Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the eff...Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.展开更多
A wind turbine system equipped with a tuned liquid column damper （TLCD） is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting ...A wind turbine system equipped with a tuned liquid column damper （TLCD） is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting response- equivalent accelerations on the shaking table. The test results show that the control effect of the TLCD system is significant in reducing the responses under both wind-wave equivalent loads and ground motions, but obviously varies for different inputs, Further, a blade-hub-tower integrated numerical model for the wind turbine system is established. The model is capable of considering the rotational effect of blades by combining Kane＇s equation with the finite element method. The responses of the wind tower equipped with TLCD devices are numerically obtained and compared to the test results, showing that under both controlled and uncontrolled conditions with and without blades＇ rotation, the corresponding responses exhibit good agreement. This demonstrates that the proposed numerical model performs well in capturing the wind-wave coupled response of the offshore wind turbine systems under control. Both numerical and experimental results show that the TLCD system can significantly reduce the structural response and thus improve the safety and serviceability of the offshore wind turbine tower systems. Additional issues that require further study are discussed.展开更多
In this paper,unsteady numerical simulation of jet Circulation Control(CC)is carried out with the NACA0012-CC airfoil as the research object.The dynamic process from the opening of jet slot and adjustment of jet inten...In this paper,unsteady numerical simulation of jet Circulation Control(CC)is carried out with the NACA0012-CC airfoil as the research object.The dynamic process from the opening of jet slot and adjustment of jet intensity to the stable state of jet control effect is explored.The time-delay effect and flow mechanism of jet are analyzed.The mechanism of jet momentum coefficient and moment coefficient fluctuating with time is revealed.The fluctuation of jet momentum coefficient is caused by the change of the pressure coefficient distribution on the Coanda surface or the structure of the wave system inside the jet,and the oscillation frequency of the wave system structure of the under-expansion supersonic jet reaches 1481 Hz at the opening moment.Based on the aerodynamic model and Proportional-Integral-Derivative(PID)control theory,the closed-loop control system of CC airfoil is designed.The parameters of PID control system are adjusted by the Genetic Algorithm(GA),which significantly improves the response ability of the control system to step,ramp and sine signals,and improves the dynamic performance of the system.Aimed at the special time-delay effect of jet control,Long Short-Term Memory(LSTM)neural network module is added to the control system to predict the target input signal,which strengthens the prediction ability of GA-PID control system to the target signal at the next time moment.By using LSTM neural network correction,the control hysteresis caused by jet time-delay effect is alleviated,and the response ability of the control system is effectively improved.Finally,the designed LSTM-GA-PID control system is applied to the NACA0012-CC airfoil for the pitch control simulation test.The test results show that the control system designed in this paper has good dynamic performance and can respond quickly and accurately to complex input signals,which confirms the effectiveness of the control system.展开更多
Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess free...Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess freeform(i.e.,non-rotational symmetric)surfaces.The toolpath,composed of high density of short linear and circular segments,is generally used in computer numerical control(CNC)systems to machine those products.However,the discontinuity between toolpath segments leads to high-frequency fluctuation of feedrate and acceleration,which will decrease the machining efficiency and product surface finish.Driven by the ever-increasing need for high-speed high-precision machining of those products,many novel toolpath interpolation and smoothing approaches have been proposed in both academia and industry,aiming to alleviate the issues caused by the conventional toolpath representation and interpolation methods.This paper provides a comprehensive review of the state-of-the-art toolpath interpolation and smoothing approaches with systematic classifications.The advantages and disadvantages of these approaches are discussed.Possible future research directions are also offered.展开更多
In order to ensure the safety,quality and efficiency of computer numerical control(CNC)machine tool processing,a real-time monitoring and visible solution for CNC machine tools based on hyper text markup language(HTML...In order to ensure the safety,quality and efficiency of computer numerical control(CNC)machine tool processing,a real-time monitoring and visible solution for CNC machine tools based on hyper text markup language(HTML)5 is proposed.The characteristics of the real-time monitoring technology of CNC machine tools under the traditional Client/Server(C/S)structure are compared and analyzed,and the technical drawbacks are proposed.Web real-time communication technology and browser drawing technology are deeply studied.A real-time monitoring and visible system for CNC machine tool data is developed based on Metro platform,combining WebSocket real-time communication technology and Canvas drawing technology.The system architecture is given,and the functions and implementation methods of the system are described in detail.The practical application results show that the WebSocket real-time communication technology can effectively reduce the bandwidth and network delay and save server resources.The numerical control machine data monitoring system can intuitively reflect the machine data,and the visible effect is good.It realizes timely monitoring of equipment alarms and prompts maintenance and management personnel.展开更多
This paper puts forward a new scheme of Embedded Numerical Control System based on ARM and DSP,which is at the base of research on traditional numerical control system and embedded technology.And the paper also descri...This paper puts forward a new scheme of Embedded Numerical Control System based on ARM and DSP,which is at the base of research on traditional numerical control system and embedded technology.And the paper also describes the develop- ment of hardware and software platform.All the development and realization are based on the idea of module design.The embed- ded numerical control system,using ARM and DSP to construct the main control platform,realizes the real-time operation of sys- tem and improves the stability and reliability with the modular designing ideas of hardware and software and with the support of embedded real-time operating system(uc/os-Ⅱ).And the system could realize the multi-network supporting,which is also accord with the development of modularization,flexibility and latticing of numerical control system.展开更多
The dimensional accuracy of machined parts is strongly influenced by the thermal behavior of machine tools (MT). Minimizing this influence represents a key objective for any modern manufacturing industry. Thermally in...The dimensional accuracy of machined parts is strongly influenced by the thermal behavior of machine tools (MT). Minimizing this influence represents a key objective for any modern manufacturing industry. Thermally induced positioning error compensation remains the most effective and practical method in this context. However, the efficiency of the compensation process depends on the quality of the model used to predict the thermal errors. The model should consistently reflect the relationships between temperature distribution in the MT structure and thermally induced positioning errors. A judicious choice of the number and location of temperature sensitive points to represent heat distribution is a key factor for robust thermal error modeling. Therefore, in this paper, the temperature sensitive points are selected following a structured thermomechanical analysis carried out to evaluate the effects of various temperature gradients on MT structure deformation intensity. The MT thermal behavior is first modeled using finite element method and validated by various experimentally measured temperature fields using temperature sensors and thermal imaging. MT Thermal behavior validation shows a maximum error of less than 10% when comparing the numerical estimations with the experimental results even under changing operation conditions. The numerical model is used through several series of simulations carried out using varied working condition to explore possible relationships between temperature distribution and thermal deformation characteristics to select the most appropriate temperature sensitive points that will be considered for building an empirical prediction model for thermal errors as function of MT thermal state. Validation tests achieved using an artificial neural network based simplified model confirmed the efficiency of the proposed temperature sensitive points allowing the prediction of the thermally induced errors with an accuracy greater than 90%.展开更多
A novel distributed numerical control (DNC) integrated system based on plug-in software technology is proposed. It connects new or old numerical control (NC) machine tools which have inhomogeneous numerical control sy...A novel distributed numerical control (DNC) integrated system based on plug-in software technology is proposed. It connects new or old numerical control (NC) machine tools which have inhomogeneous numerical control systems with CAD/CAM system by CANbus network. A DNC computer is able to control 15 sets of NC machine tools reliably at the same time. The novel DNC system increases the efficiency of machine tools and improve the production management level by realizing non-paper production, agile manufacturing, networked manufacturing and so on in the near future. Key technologies to construct the novel DNC integrated system include the integration of inhomogeneous numerical control systems, NC program restart, and algorithm for communication competition. Such system has demonstrated successful applications in some corporations that have acquired good economic benefits and social effects.展开更多
To monitor, control and manage the work process of computer numerical control machine tools in a flexible manufacturing system (FMS) effectively, the distributed numerical coutrol (distributed-NC) software should be i...To monitor, control and manage the work process of computer numerical control machine tools in a flexible manufacturing system (FMS) effectively, the distributed numerical coutrol (distributed-NC) software should be innovated with the characteristics of modularization and reconfiguration. In this paper, firstly, distributed-NC functions in the FMS environment are described. Then, we present a design and development method of the real time distributed-NC that is on the basis of the re-coufigurable software and hardware platform and with an object-oriented model concept. Finally, to verify the proposed method, the distributed-NC software has been implemented in VC++ 6.0 and has been tested in connection with the different physical flexible manufacturing shops.展开更多
This paper proposes a system representation for unifying control design and numerical calculation in nonlinear optimal control problems with inequality constraints in terms of the symplectic structure. The symplectic ...This paper proposes a system representation for unifying control design and numerical calculation in nonlinear optimal control problems with inequality constraints in terms of the symplectic structure. The symplectic structure is derived from Hamiltonian systems that are equivalent to Hamilton-Jacobi equations. In the representation, the constraints can be described as an input-state transformation of the system. Therefore, it can be seamlessly applied to the stable manifold method that is a precise numerical solver of the Hamilton-Jacobi equations. In conventional methods, e.g., the penalty method or the barrier method, it is difficult to systematically assign the weights of penalty functions that are used for realizing the constraints. In the proposed method, we can separate the adjustment of weights with respect to objective functions from that of penalty functions. Furthermore, the proposed method can extend the region of computable solutions in a state space. The validity of the method is shown by a numerical example of the optimal control of a vehicle model with steering limitations.展开更多
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2021B0301030001)the National Key Research and Development Program of China(Grant No.2021YFB3802300)the Foundation of National Key Laboratory of Shock Wave and Detonation Physics(Grant No.JCKYS2022212004)。
文摘The graded density impactor(GDI)dynamic loading technique is crucial for acquiring the dynamic physical property parameters of materials used in weapons.The accuracy and timeliness of GDI structural design are key to achieving controllable stress-strain rate loading.In this study,we have,for the first time,combined one-dimensional fluid computational software with machine learning methods.We first elucidated the mechanisms by which GDI structures control stress and strain rates.Subsequently,we constructed a machine learning model to create a structure-property response surface.The results show that altering the loading velocity and interlayer thickness has a pronounced regulatory effect on stress and strain rates.In contrast,the impedance distribution index and target thickness have less significant effects on stress regulation,although there is a matching relationship between target thickness and interlayer thickness.Compared with traditional design methods,the machine learning approach offers a10^(4)—10^(5)times increase in efficiency and the potential to achieve a global optimum,holding promise for guiding the design of GDI.
基金supported by the National Natural Science Foundation of China(No.T2288101)the National Key Research and Development Project,China(No.2020YFC1512500)the Academic Excellence Foundation of Beijing University of Aeronautics and Astronautics(BUAA)。
文摘Considering the challenges posed by external disturbances on carrier-based aircraft land-ing control,higher demands are required for the precision and convergence of the carrier landingcontrol system.First,this paper proposes an Adaptive Terminal Sliding Combined Super TwistingControl(ATS-STC)method to address the issues of low precision,slow convergence,and poor dis-turbance rejection capability resulting from external disturbances,such as carrier air-wake and deckmotion.By introducing a nonlinear term into the sliding surface and employing an integralapproach,the proposed ATS-STC method can ensure finite-time convergence and mitigate the chat-tering problem.An adaptive law is also utilized to estimate the external disturbances,therebyenhancing the anti-disturbance performance.Then,the stability and convergence time analysis ofthe designed controller are conducted.Based on the proposed method,an Automatic Carrier Land-ing System(ACLS)is developed to perform the carrier landing control task.Furthermore,a multi-dimensional validation is carried out.For the numerical simulation test,the Terminal Sliding ModeControl(TSMC)method and Proportion Integration Differentiation(PID)method are introducedas comparison,the quantitative assessment results show that the tracking error of TSMC and PIDcan reach 1.5 times and 2 times that of the proposed method.Finally,the Hardware-in-the-Loop(HIL)test and real flight test are conducted.All the experimental results demonstrate that the pro-posed control method is more effective and precise.
文摘Addressing the issue of excessive cavitation pressure fluctuation on the propeller behind a catamaran,numerical simulation is conducted to assess the quality of the wake flow and to numerically predict the pressure fluctuation induced by the propeller cavitation.Additionally,the interaction between the wake vortex field and the propeller is investigated,revealing the presence of propeller-hull vortex.To improve the propeller's inflow quality,the impact of vortex generators on the wake flow and pressure fluctuation is numerically simulated.Then,numerical simulations are conducted to compare the cavitation pressure fluctuation of optimized propeller design,evaluating the effects of vortex generators at different spatial locations and angles of attack,to determine the optimal vortex generator scheme.A more comprehensive integrated control plan for the wake flow and the cavitation pressure fluctuation of the propeller behind the catamaran is finally formed.
基金sponsored by the National Natural Science Foundation of China(Grant No.42075148)the High-Performance Computing Center of Nanjing University of Information Science & Technology for supporting this work。
文摘Accurate skin temperature is one of the critical factors in successfully assimilating satellite radiance data over land.However,model-simulated skin temperature may not be accurate enough.To address this issue,an extended skin temperature control variable(TSCV) approach is proposed in a variational assimilation framework,which also considers the background error correlation between skin temperature and atmospheric variables.A series of single observation tests and a 10-day cycling assimilation experiment were conducted to evaluate the impact of the TSCV approach on the assimilation of AMSU-A and ATMS(Advanced Technology Microwave Sounder) microwave temperature-sounding channels over land.The results of the single observation tests show that by applying the TSCV approach,not only the direct analysis of skin temperature is realized,but also the interaction between skin temperature and atmospheric variables can be achieved during the assimilation process.The results of the cycling experiment demonstrate that the TSCV approach improves the skin temperature analysis,which in turn reduces the RMSE of the surface variables and low-level air temperature forecasts.The TSCV approach also reduces the difference between the observed and simulated brightness temperatures of both microwave and infrared window channels over land,suggesting that the approach can facilitate the radiance simulation of these channels,thus contributing to the assimilation of window channels.
基金the National Science and Technology Major Project of China(No.2014ZX04014-011)
文摘The core of computer numerical control(CNC) machine tool is the electrical system which controls and coordinates every part of CNC machine tool to complete processing tasks, so it is of great significance to strengthen the reliability of the electrical system. However, the electrical system is very complex due to many uncertain factors and dynamic stochastic characteristics when failure occurs. Therefore, the traditional fault tree analysis(FTA) method is not applicable. Bayesian network(BN) not only has a unique advantage to analyze nodes with multiply states in reliability analysis for complex systems, but also can solve the state explosion problem properly caused by Markov model when dealing with dynamic fault tree(DFT). In addition, the forward causal reasoning of BN can get the conditional probability distribution of the system under considering the uncertainty;the backward diagnosis reasoning of BN can recognize the weak links in system, so it is valuable for improving the system reliability.
基金Projects(50875090,50905063) supported by the National Natural Science Foundation of ChinaProject(2009AA04Z111) supported by the National High Technology Research and Development Program of China+2 种基金Project(20090460769) supported by China Postdoctoral Science FoundationProject(2011ZM0070) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(S2011010001155) supported by the Natural Science Foundation of Guangdong Province,China
文摘In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.
基金the National Natural Science Foundation of China (Nos. 50575075 and 50875090)
文摘A component-based model integration framework for computer numerical control system design and development is presented.The model integrates modeling,simulation,verification and implementation in a uniform environment.The computer numerical control(CNC) modeling language with well defined syntax and unambiguous semantics is developed.Using the proposed CNC model integration method,a three axis milling system model is developed in the case study.The approach is an attempt to create an infrastructure to support the CNC system design in an efficient way,while at the same time guarantees the function and performance requirements with advanced capability of the system such as modularity,flexibility,reusability,etc.
基金Key Development Program of Science and Technology of Heilongjiang Province, China (GB05A501)
文摘A 5-axis controller with curve interpolation function is developed to satisfy high-speed and high-precision computer numerical control (CNC) machining of machine parts with complex shapes in the authors-devised open CNC system. The instruction for- mat of this interpolation method and the generation procedure of the numerical control (NC) files are introduced. The interpola- tion curves of both position vectors and orientation vectors constructed by the controller are C2 continuous and independent of machin...
文摘In this paper,an intelligent control method applying on numerical virtual flight is proposed.The proposed algorithm is verified and evaluated by combining with the case of the basic finner projectile model and shows a good application prospect.Firstly,a numerical virtual flight simulation model based on overlapping dynamic mesh technology is constructed.In order to verify the accuracy of the dynamic grid technology and the calculation of unsteady flow,a numerical simulation of the basic finner projectile without control is carried out.The simulation results are in good agreement with the experiment data which shows that the algorithm used in this paper can also be used in the design and evaluation of the intelligent controller in the numerical virtual flight simulation.Secondly,combined with the real-time control requirements of aerodynamic,attitude and displacement parameters of the projectile during the flight process,the numerical simulations of the basic finner projectile’s pitch channel are carried out under the traditional PID(Proportional-Integral-Derivative)control strategy and the intelligent PID control strategy respectively.The intelligent PID controller based on BP(Back Propagation)neural network can realize online learning and self-optimization of control parameters according to the acquired real-time flight parameters.Compared with the traditional PID controller,the concerned control variable overshoot,rise time,transition time and steady state error and other performance indicators have been greatly improved,and the higher the learning efficiency or the inertia coefficient,the faster the system,the larger the overshoot,and the smaller the stability error.The intelligent control method applying on numerical virtual flight is capable of solving the complicated unsteady motion and flow with the intelligent PID control strategy and has a strong promotion to engineering application.
基金supported by the project of the China Geological Survey(No.DD20221746)the National Natural Science Foundation of China(Grant Nos.41101086)。
文摘Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.
基金National Natural Science Foundation of China Under Grant No.11172210National Hi-Tech Development Plan(863 Plan)Under Grant No.2008AA05Z413+2 种基金the Fundamental Fund for Central Universitiesthe Shuguang Program of Shanghai Citythe State Key Laboratory of Disaster Reduction in Civil Engineering Under Grant Nos.SLDRCE14-A-06 and SLDRCE14-B-17
文摘A wind turbine system equipped with a tuned liquid column damper （TLCD） is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting response- equivalent accelerations on the shaking table. The test results show that the control effect of the TLCD system is significant in reducing the responses under both wind-wave equivalent loads and ground motions, but obviously varies for different inputs, Further, a blade-hub-tower integrated numerical model for the wind turbine system is established. The model is capable of considering the rotational effect of blades by combining Kane＇s equation with the finite element method. The responses of the wind tower equipped with TLCD devices are numerically obtained and compared to the test results, showing that under both controlled and uncontrolled conditions with and without blades＇ rotation, the corresponding responses exhibit good agreement. This demonstrates that the proposed numerical model performs well in capturing the wind-wave coupled response of the offshore wind turbine systems under control. Both numerical and experimental results show that the TLCD system can significantly reduce the structural response and thus improve the safety and serviceability of the offshore wind turbine tower systems. Additional issues that require further study are discussed.
基金Supported by the National Natural Science Foundation of China(No.11972306)the Foundation of National Key Laboratory,China,and the 111 Project of China(No.B17037).
文摘In this paper,unsteady numerical simulation of jet Circulation Control(CC)is carried out with the NACA0012-CC airfoil as the research object.The dynamic process from the opening of jet slot and adjustment of jet intensity to the stable state of jet control effect is explored.The time-delay effect and flow mechanism of jet are analyzed.The mechanism of jet momentum coefficient and moment coefficient fluctuating with time is revealed.The fluctuation of jet momentum coefficient is caused by the change of the pressure coefficient distribution on the Coanda surface or the structure of the wave system inside the jet,and the oscillation frequency of the wave system structure of the under-expansion supersonic jet reaches 1481 Hz at the opening moment.Based on the aerodynamic model and Proportional-Integral-Derivative(PID)control theory,the closed-loop control system of CC airfoil is designed.The parameters of PID control system are adjusted by the Genetic Algorithm(GA),which significantly improves the response ability of the control system to step,ramp and sine signals,and improves the dynamic performance of the system.Aimed at the special time-delay effect of jet control,Long Short-Term Memory(LSTM)neural network module is added to the control system to predict the target input signal,which strengthens the prediction ability of GA-PID control system to the target signal at the next time moment.By using LSTM neural network correction,the control hysteresis caused by jet time-delay effect is alleviated,and the response ability of the control system is effectively improved.Finally,the designed LSTM-GA-PID control system is applied to the NACA0012-CC airfoil for the pitch control simulation test.The test results show that the control system designed in this paper has good dynamic performance and can respond quickly and accurately to complex input signals,which confirms the effectiveness of the control system.
基金the support from the UK Engineering and Physical Sciences Research Council (EPSRC) under the program (No. EP/K018345/1)the International Cooperation Program of China (No. 2015DFA70630)
文摘Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess freeform(i.e.,non-rotational symmetric)surfaces.The toolpath,composed of high density of short linear and circular segments,is generally used in computer numerical control(CNC)systems to machine those products.However,the discontinuity between toolpath segments leads to high-frequency fluctuation of feedrate and acceleration,which will decrease the machining efficiency and product surface finish.Driven by the ever-increasing need for high-speed high-precision machining of those products,many novel toolpath interpolation and smoothing approaches have been proposed in both academia and industry,aiming to alleviate the issues caused by the conventional toolpath representation and interpolation methods.This paper provides a comprehensive review of the state-of-the-art toolpath interpolation and smoothing approaches with systematic classifications.The advantages and disadvantages of these approaches are discussed.Possible future research directions are also offered.
文摘In order to ensure the safety,quality and efficiency of computer numerical control(CNC)machine tool processing,a real-time monitoring and visible solution for CNC machine tools based on hyper text markup language(HTML)5 is proposed.The characteristics of the real-time monitoring technology of CNC machine tools under the traditional Client/Server(C/S)structure are compared and analyzed,and the technical drawbacks are proposed.Web real-time communication technology and browser drawing technology are deeply studied.A real-time monitoring and visible system for CNC machine tool data is developed based on Metro platform,combining WebSocket real-time communication technology and Canvas drawing technology.The system architecture is given,and the functions and implementation methods of the system are described in detail.The practical application results show that the WebSocket real-time communication technology can effectively reduce the bandwidth and network delay and save server resources.The numerical control machine data monitoring system can intuitively reflect the machine data,and the visible effect is good.It realizes timely monitoring of equipment alarms and prompts maintenance and management personnel.
文摘This paper puts forward a new scheme of Embedded Numerical Control System based on ARM and DSP,which is at the base of research on traditional numerical control system and embedded technology.And the paper also describes the develop- ment of hardware and software platform.All the development and realization are based on the idea of module design.The embed- ded numerical control system,using ARM and DSP to construct the main control platform,realizes the real-time operation of sys- tem and improves the stability and reliability with the modular designing ideas of hardware and software and with the support of embedded real-time operating system(uc/os-Ⅱ).And the system could realize the multi-network supporting,which is also accord with the development of modularization,flexibility and latticing of numerical control system.
文摘The dimensional accuracy of machined parts is strongly influenced by the thermal behavior of machine tools (MT). Minimizing this influence represents a key objective for any modern manufacturing industry. Thermally induced positioning error compensation remains the most effective and practical method in this context. However, the efficiency of the compensation process depends on the quality of the model used to predict the thermal errors. The model should consistently reflect the relationships between temperature distribution in the MT structure and thermally induced positioning errors. A judicious choice of the number and location of temperature sensitive points to represent heat distribution is a key factor for robust thermal error modeling. Therefore, in this paper, the temperature sensitive points are selected following a structured thermomechanical analysis carried out to evaluate the effects of various temperature gradients on MT structure deformation intensity. The MT thermal behavior is first modeled using finite element method and validated by various experimentally measured temperature fields using temperature sensors and thermal imaging. MT Thermal behavior validation shows a maximum error of less than 10% when comparing the numerical estimations with the experimental results even under changing operation conditions. The numerical model is used through several series of simulations carried out using varied working condition to explore possible relationships between temperature distribution and thermal deformation characteristics to select the most appropriate temperature sensitive points that will be considered for building an empirical prediction model for thermal errors as function of MT thermal state. Validation tests achieved using an artificial neural network based simplified model confirmed the efficiency of the proposed temperature sensitive points allowing the prediction of the thermally induced errors with an accuracy greater than 90%.
文摘A novel distributed numerical control (DNC) integrated system based on plug-in software technology is proposed. It connects new or old numerical control (NC) machine tools which have inhomogeneous numerical control systems with CAD/CAM system by CANbus network. A DNC computer is able to control 15 sets of NC machine tools reliably at the same time. The novel DNC system increases the efficiency of machine tools and improve the production management level by realizing non-paper production, agile manufacturing, networked manufacturing and so on in the near future. Key technologies to construct the novel DNC integrated system include the integration of inhomogeneous numerical control systems, NC program restart, and algorithm for communication competition. Such system has demonstrated successful applications in some corporations that have acquired good economic benefits and social effects.
基金Project supported by the National High-Tech. R&D Program for CIMS, China (Grant No. 2003AA414120) Shanghai Science & Technology development Project, China (Grant No. 02FK04)
文摘To monitor, control and manage the work process of computer numerical control machine tools in a flexible manufacturing system (FMS) effectively, the distributed numerical coutrol (distributed-NC) software should be innovated with the characteristics of modularization and reconfiguration. In this paper, firstly, distributed-NC functions in the FMS environment are described. Then, we present a design and development method of the real time distributed-NC that is on the basis of the re-coufigurable software and hardware platform and with an object-oriented model concept. Finally, to verify the proposed method, the distributed-NC software has been implemented in VC++ 6.0 and has been tested in connection with the different physical flexible manufacturing shops.
文摘This paper proposes a system representation for unifying control design and numerical calculation in nonlinear optimal control problems with inequality constraints in terms of the symplectic structure. The symplectic structure is derived from Hamiltonian systems that are equivalent to Hamilton-Jacobi equations. In the representation, the constraints can be described as an input-state transformation of the system. Therefore, it can be seamlessly applied to the stable manifold method that is a precise numerical solver of the Hamilton-Jacobi equations. In conventional methods, e.g., the penalty method or the barrier method, it is difficult to systematically assign the weights of penalty functions that are used for realizing the constraints. In the proposed method, we can separate the adjustment of weights with respect to objective functions from that of penalty functions. Furthermore, the proposed method can extend the region of computable solutions in a state space. The validity of the method is shown by a numerical example of the optimal control of a vehicle model with steering limitations.
