The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gr...The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gramming （SQP）. Firstly, a steady-state hybrid aero-engine model is designed in the whole flight envelope with a dramatic enhancement of real-time capability. Secondly, the aero-engine performance seeking control including the maximum thrust mode and the minimum fuel-consumption mode is performed by SQP. Finally, digital simu- lations for cruise and accelerating flight are carried out. Results show that the proposed method improves real- time capability considerably with satisfactory effectiveness of optimization.展开更多
This paper focuses on the H_∞ model reference tracking control for a switched linear parameter-varying(LPV)model representing an aero-engine. The switched LPV aeroengine model is built based on a family of linearized...This paper focuses on the H_∞ model reference tracking control for a switched linear parameter-varying(LPV)model representing an aero-engine. The switched LPV aeroengine model is built based on a family of linearized models.Multiple parameter-dependent Lyapunov functions technique is used to design a tracking control law for the desirable H_∞ tracking performance. A control synthesis condition is formulated in terms of the solvability of a matrix optimization problem.Simulation result on the aero-engine model shows the feasibility and validity of the switching tracking control scheme.展开更多
Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent t...Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. In this paper, a turbine tip clearance control apparatus and a model of turbine tip clearance are proposed; an implicit active generalized predictive control （GPC）, with auto-regressive （AR） error modification and fuzzy adjustment on control horizon, is presented, as well as a quantitative analysis method of robust per- turbation radius of the system. The active clearance control （ACC） of aero-engine turbine tip clear- ance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis of the stability and robustness of the active tip clearance control system. The results show that the resultant active tip clearance control system with the improved GPC has favorable steadystate and dynamic performance and benefits of increased efficiency, reduced specific fuel consump- tion, and additional service life.展开更多
Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency,however,is difficult to be guaranteed in suc...Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency,however,is difficult to be guaranteed in such a process.To overcome this problem,a method of hybrid force-position control combined with PI/PD control is proposed to be applied in robotic abrasive belt grinding of complex geometries.Voltage signals are firstly obtained and transformed to force information with signal conditioning methods.Secondly,zero drift and gravity compensation algorithms are presented to calibrate the F/T transducer which is installed on the robot end-effector.Next,a force control strategy combining hybrid force-position control with PI/PD control is introduced to be employed in robotic abrasive belt grinding operations where the force control law is applied to the Z direction of the tool frame and the positon control law is used in the X direction of the tool frame.Then,the accuracy of the F/T transducer and the robotic force control system is analyzed to ensure the stability and reliability of force control in the robotic grinding process.Finally,two typical cases on robotic belt grinding of a test workpiece and an aero-engine blade are conducted to validate the practicality and effectiveness of the force control technology proposed.展开更多
The existing methods for blade polishing mainly focus on robot polishing and manual grinding.Due to the difficulty in high-precision control of the polishing force,the blade surface precision is very low in robot poli...The existing methods for blade polishing mainly focus on robot polishing and manual grinding.Due to the difficulty in high-precision control of the polishing force,the blade surface precision is very low in robot polishing,in particular,quality of the inlet and exhaust edges can not satisfy the processing requirements.Manual grinding has low efficiency,high labor intensity and unstable processing quality,moreover,the polished surface is vulnerable to burn,and the surface precision and integrity are difficult to ensure.In order to further improve the profile accuracy and surface quality,a pneumatic flexible polishing force-exerting mechanism is designed and a dual-mode switching composite adaptive control(DSCAC) strategy is proposed,which combines Bang-Bang control and model reference adaptive control based on fuzzy neural network(MRACFNN) together.By the mode decision-making mechanism,Bang-Bang control is used to track the control command signal quickly when the actual polishing force is far away from the target value,and MRACFNN is utilized in smaller error ranges to improve the system robustness and control precision.Based on the mathematical model of the force-exerting mechanism,simulation analysis is implemented on DSCAC.Simulation results show that the output polishing force can better track the given signal.Finally,the blade polishing experiments are carried out on the designed polishing equipment.Experimental results show that DSCAC can effectively mitigate the influence of gas compressibility,valve dead-time effect,valve nonlinear flow,cylinder friction,measurement noise and other interference on the control precision of polishing force,which has high control precision,strong robustness,strong anti-interference ability and other advantages compared with MRACFNN.The proposed research achieves high-precision control of the polishing force,effectively improves the blade machining precision and surface consistency,and significantly reduces the surface roughness.展开更多
PartⅠhas illustrated the procedures to apply the Linkage Learning Genetic Algorithm(LLGA)in Gas Turbine Engine(GTE)controller gains tuning and generated the optimization results for runway conditions from idle to tak...PartⅠhas illustrated the procedures to apply the Linkage Learning Genetic Algorithm(LLGA)in Gas Turbine Engine(GTE)controller gains tuning and generated the optimization results for runway conditions from idle to takeoff.However,the total pressure and temperature of the engine inlet vary as the changing of altitude and Mach number,which would lead to the variation in fuel flow supply regulation.As a result,the optimized gains in runway might not be suitable for other flight conditions.In order to maintain the optimal control performance,the GTE controller gains should be adjusted according to the flight conditions.This paper extends the application of the LLGA method to other flight conditions and then simulates a complete flight mission with different gains and weather condition configurations.For this purpose,the control parameters in the Simulink model of the GTE controller are first corrected by the weather condition in altitude.Then,a typical flight mission is defined and divided into different flight segments based on the altitude and Mach number configuration.One representative point is selected from each segment as the datum point for optimization process.After this step,the LLGA method is used to find the best gains combinations for different flight conditions and the differences in optimization effects for different flight conditions are analyzed subsequently.The simulation results show that the optimization effect of the control performance of each flight condition is dependent on the value of(θδ)~(1/2)and the optimal K_(pla)in some flight conditions is approximately equal to p hd times of the Kplavalue in sea level standard condition.Finally,the complete flight mission is simulated with different gains and weather condition configurations.The simulation results show that the engine performance has been greatly improved after optimization by LLGA in the transient state and the high altitude conditions.In other steady states,the optimization effect is not very obvious.展开更多
To perform transient state control of an aero-engine,a structure that combines linear controller and min–max selector is widely adopted,which is inherently conservative and therefore limits the fulfillment of the eng...To perform transient state control of an aero-engine,a structure that combines linear controller and min–max selector is widely adopted,which is inherently conservative and therefore limits the fulfillment of the engine potential.Model predictive control is a new control method that has vast application prospects in the field of aero-engine control.Therefore,this paper proposes a wide-range model predictive controller that can control the engine over a wide range within the flight envelope.This paper first introduces the engine parameters and the model prediction algorithm used by the controller.Then a wide-range model prediction controller with a three-layer nested structure is presented.These three layers of the structure are univariate controller,nominal point controller,and wide-range controller from inside to outside.Finally,by analyzing and verifying the effectiveness of the univariate controller for small-range variations and the wide-range model predictive controller for large-range parameter variations,it is demonstrated that the controller can schedule the controller’s output based on inlet altitude,Mach number,and lowpressure shaft corrected speed,and ensure that the limits are not exceeded.It is concluded that the designed wide-range model predictive controller has good dynamic effect and safety.展开更多
The onboard adaptive model can achieve the online real-time estimation of performance parameters that are difficult to measure in a real aero-engine,which is the key to realizing modelbased performance control.It must...The onboard adaptive model can achieve the online real-time estimation of performance parameters that are difficult to measure in a real aero-engine,which is the key to realizing modelbased performance control.It must possess satisfactory numerical stability and estimation accuracy.However,the positive definiteness of the state covariance matrix may be destroyed in filter estimation because of the existence of some uncertain factors,such as the accumulated measurement error,noise,and disturbance in the strongly nonlinear engine system,inevitably causing divergence of estimates of Cholesky decomposition-based Spherical Unscented Kalman Filter(SUKF).Therefore,this paper proposes an improved SUKF algorithm(iSUKF)and applies it to the performance degradation estimation of the engine.Compared to SUKF,the iSUKF mainly replaces the Cholesky decomposition with the Singular Value Decomposition(SVD),which is numerically stable without any strict requirement for the state covariance matrix.Meanwhile,a correction factor is designed to assess the measurement deviation between the real engine and the nonlinear onboard model to correct the state covariance matrix,thus maintaining better numerical stability of parameters estimated by the filter.Then,an offline correction strategy is also proposed to eliminate the influence of the degradation of unestimated health parameters or the filter’s inadequate estimation of the coupled health parameters.This action effectively promotes the onboard adaptive model’s estimation accuracy concerning the degradation of the engine’real health parameters and its performance parameters.Finally,the simulation results show that the iSUKF can maintain the numerical stability of the filter’s estimation of health parameters.Compared with the existing methods,the offline correction strategy improves the estimation accuracy of the iSUKF-based nonlinear onboard adaptive model for the performance parameters of the real engine by more than 50%.The proposed method will provide feasible technical support for model-based aero-engine performance control.展开更多
A fault tolerant control method is proposed in this paper for a turbofan engine gas path degradation through the full flight envelope. A Quantum-behaved Particle Swarm Optimization(QPSO) algorithm is applied to obtain...A fault tolerant control method is proposed in this paper for a turbofan engine gas path degradation through the full flight envelope. A Quantum-behaved Particle Swarm Optimization(QPSO) algorithm is applied to obtain engine inputs adjustments, which contribute to construct off-line performance accommodation interpolation schedules. With a double closed-loop control system structure, command control is corrected based on real-time fault diagnostic results. Simulations indicate that fault tolerant control could reduce thrust and stall margin loss effectively in gas path faults.展开更多
The original monitoring data from aero-engines possess characteristics such as high dimen-sionality,strong noise,and imbalance,which present substantial challenges to traditional anomalydetection methods.In response,t...The original monitoring data from aero-engines possess characteristics such as high dimen-sionality,strong noise,and imbalance,which present substantial challenges to traditional anomalydetection methods.In response,this paper proposes a method based on Fuzzy Fusion of variablesand Discriminant mapping of features for Clustering(FFD-Clustering)to detect anomalies in originalmonitoring data from Aircraft Communication Addressing and Reporting System(ACARS).Firstly,associated variables are fuzzily grouped to extract the underlying distribution characteristics and trendsfrom the data.Secondly,a multi-layer contrastive denoising-based feature Fusion Encoding Network(FEN)is designed for each variable group,which can construct representative features for each variablegroup through eliminating strong noise and complex interrelations between variables.Thirdly,a featureDiscriminative Mapping Network(DMN)based on reconstruction difference re-clustering is designed,which can distinguish dissimilar feature vectors when mapping representative features to a unified fea-ture space.Finally,the K-means clustering is used to detect the abnormal feature vectors in the unifiedfeature space.Additionally,the algorithm is capable of reconstructing identified abnormal vectors,thereby locating the abnormal variable groups.The performance of this algorithm was tested ontwo public datasets and real original monitoring data from four aero-engines'ACARS,demonstratingits superiority and application potential in aero-engine anomaly detection.展开更多
By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the ...By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the grain sizes of K4169 superalloy significantly increase,and the precipitation of the needle-likeδphase and the Laves phase is observed.Voids and microcracks form at location of Laves phase enrichment,creating conditions for crack propagation.By the a−N(a is the crack length,and N is the number of cycles)relationship curve,the change in the fatigue crack growth rate with the increasing number of cycles progresses through three separate stages.The fracture process of K4169 superalloy under low-stress cyclic loading(3 kN)exhibits the ductile fracture.Subsequently,the fracture process starts to change from the ductile fracture to the brittle fracture as the stress increases to 4.5 kN.In the microstructures of fractures in both stress states,intergranular propagation is the mechanism responsible for crack propagation.Moreover,the Laves phase exists near the fracture crack,which is in line with the post-service structural phenomenon.展开更多
Precise and quantitative measurement of soot particle emission plays an essential role in accurately assessing the combustion performance of aero-engine combustors and infrared signature levels in aircraft exhausts.Am...Precise and quantitative measurement of soot particle emission plays an essential role in accurately assessing the combustion performance of aero-engine combustors and infrared signature levels in aircraft exhausts.Among various intrusive or non-intrusive approaches for soot diagnostics,Laser-Induced Incandescence(LⅡ)technique has been increasingly applied for soot concentration measurement in various combustion environments such as laminar flames and internal combustion engines due to its high spatial resolution and sensitivity.As for LⅡmeasurement in aero-engine combustors,however,it normally suffers from very limited optical accesses and often faces mandatory requirements of oblique imaging from a small backward angle.In this work,we demonstrate a Two-Color(2C)LⅡsystem that simultaneously captures LⅡsignal images at two distinct wavelengths using a Scheimpflug imaging configuration.A projective transformation algorithm and image overlapping procedures were employed to spatially correct the raw Scheimpflug LⅡimages.Performance validation of the developed 2C-Scheimpflug LⅡsystem was first conducted under specified conditions in a laminar C_(2)H_(4)/air McKenna flame.The obtained Soot Volume Fraction(SVF)level and its spatial distribution are in consistent with previous studies under identical flame conditions reported by other research groups.Finally,as a demonstration of engineering benchmark application,we applied the developed 2C-Scheimpflug LⅡsystem to measure SVF distribution in the cross-section plane perpendicular to the direction of flame propagation at the exhaust of a single-sector dual-swirl aero-engine model combustor.Transient soot production events were observed and characteristics of the SVF distribution were investigated.These experimental results suggest the feasibility of the 2C-Scheimpflug LⅡtechnique developed in this work for precise and quantitative measurements of soot concentration in practical environments.展开更多
This paper analyzes the nonlinear dynamic characteristics and stability of Aero-Engine Dual-Rotor(AEDR)systems under high-frequency excitation,based on the Adaptive Harmonic Balance with the Asymptotic Harmonic Select...This paper analyzes the nonlinear dynamic characteristics and stability of Aero-Engine Dual-Rotor(AEDR)systems under high-frequency excitation,based on the Adaptive Harmonic Balance with the Asymptotic Harmonic Selection(AHB-AHS)method.A finite element dynamic equation for the AEDR system is introduced,considering complex nonlinearities of the intershaft bearing,unbalanced excitations,and high-frequency excitation.A solving strategy combining the AHB-AHS method and improved arclength continuation method is proposed to solve highdimensional dynamic equations containing complex nonlinearities and to track periodic solutions with parameter variations.The Floquet theory is used to analyze the types of bifurcation points in the system and the stability of periodic motions.The results indicate that high-frequency excitation can couple high-order and low-order modes,especially when the system undergoes superharmonic resonance.High-frequency excitation leads to more combination frequency harmonics,among which N_(f)ω_(1)-2ω_(2)dominates.Furthermore,changing the parameters(amplitude and frequency)of high-frequency excitation widens or shifts the unstable regions of the system.These findings contribute to understanding the mechanism of high-frequency excitation on aero-engines and demonstrate that the proposed AHB-AHS method is a powerful tool for analyzing highdimensional complex nonlinear dynamic systems under multi-frequency excitation.展开更多
Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero...Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control(LADRC)is proposed.Firstly,based on CFD numerical simulation,aerodynamic performance model of AVEN is established,and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed.Subsequently,the integrated model of AVEN/-turbofan engine is established by Simulink/AMESim co-simulation.Finally,the nozzle throat area control loop based on LADRC is designed.The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system.The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%,indicating a high degree of confidence.Compared with the conventional PID control,the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%,which effectively improves the control stability of the vector deflection.Meanwhile,the fuel flow ratechange during the vector deflection process is smaller and more economical,which provides an important reference for engineering applications.展开更多
Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, La...Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, Laser-Induced Incandescence (LII) has been increasingly applied for soot concentration quantification in various combustion environments such as laminar flame, vehicle exhaust, internal combustion chamber as well as aero-engine combustor. In this work, we experimentally measured the spatial and temporal distribution of SVF using two-color LII technique at the outlet of a single-sector dual-swirl aero-engine model combustor. The effect of inlet pressure and air preheat temperature on the SVF distribution was separately investigated within a pressure range of 241–425 kPa and a temperature range of 292–500 K. The results show that soot production increases with the inlet pressure but generally decreases with the air preheat temperature. Qualitative analysis was provided to explain the above results of parametric studies. The LII experiments were also conducted under 3 designed conditions to evaluate soot emission under practical operations. Particularly, weak soot emission was detected at the outlet under the idle condition. Our experimental results provide a valuable benchmark for evaluating soot emission in the exhaust plume of this aero-engine combustor during practical operations.展开更多
The spatiotemporal distribution of soot concentration in aero-engine combustor is important for assessing its combustion performance.Here,we report experimental measurements of soot concentration in terms of Soot Volu...The spatiotemporal distribution of soot concentration in aero-engine combustor is important for assessing its combustion performance.Here,we report experimental measurements of soot concentration in terms of Soot Volume Fraction(SVF)and its spatiotemporal distribution in a single-sector dual-swirl aero-engine combustor using Two-Color Laser-Induced Incandescence(2C-LII).It is shown that soot predominantly forms in the symmetrical vortices of the primary combustion zone,exhibiting a V-type distribution with higher concentration in the lower half of the zone than the upper half,with a small amount distributed in the secondary recirculation zone.Soot emissions at the combustor outlet are relatively low under three typical operating conditions by LII experiments,which is aligned with Smoke Number(SN)from gas analysis.The effect of inlet air temperature on SVF distribution and dynamics in the primary combustion zone is studied,which suggests that the SVF level in the primary combustion zone monotonically increases with the temperature.Meanwhile,the SVF distribution becomes more symmetrical as the inlet temperature increases,although the overall SVF level in the lower half of the zone is still higher.We also investigate the influence of the inlet air pressure on the SVF distribution at the combustor outlet.The soot concentration at the combustor outlet increases with inlet pressure,mainly distributed irregularly across both sides and the center.On both sides,the distribution is continuous,while the center exhibits dot-like and linear patterns.Numerical simulations correlated SVF distribution with the flow field in the primary combustion zone,qualitatively explaining the observed SVF distribution behavior.These results under various conditions can provide valuable insights for improving the performance of this specific combustor and designing high-temperature-rise combustors in the future.展开更多
The problem of analysis and synthesis of robust control is addressed in this work. The approach transferring the robust control design into Linear Matrix Inequality (LMI) is provided. The LMI standard structure of rob...The problem of analysis and synthesis of robust control is addressed in this work. The approach transferring the robust control design into Linear Matrix Inequality (LMI) is provided. The LMI standard structure of robust controller is also given and the controller is obtained through solving three LMIs. As an example, a robust control law is designed to the twin-spool turbojet engine system using the given approach. The result shows that LMI approach is feasible.展开更多
Aiming to solve the steering instability and hysteresis of agricultural robots in the process of movement,a fusion PID control method of particle swarm optimization(PSO)and genetic algorithm(GA)was proposed.The fusion...Aiming to solve the steering instability and hysteresis of agricultural robots in the process of movement,a fusion PID control method of particle swarm optimization(PSO)and genetic algorithm(GA)was proposed.The fusion algorithm took advantage of the fast optimization ability of PSO to optimize the population screening link of GA.The Simulink simulation results showed that the convergence of the fitness function of the fusion algorithm was accelerated,the system response adjustment time was reduced,and the overshoot was almost zero.Then the algorithm was applied to the steering test of agricultural robot in various scenes.After modeling the steering system of agricultural robot,the steering test results in the unloaded suspended state showed that the PID control based on fusion algorithm reduced the rise time,response adjustment time and overshoot of the system,and improved the response speed and stability of the system,compared with the artificial trial and error PID control and the PID control based on GA.The actual road steering test results showed that the PID control response rise time based on the fusion algorithm was the shortest,about 4.43 s.When the target pulse number was set to 100,the actual mean value in the steady-state regulation stage was about 102.9,which was the closest to the target value among the three control methods,and the overshoot was reduced at the same time.The steering test results under various scene states showed that the PID control based on the proposed fusion algorithm had good anti-interference ability,it can adapt to the changes of environment and load and improve the performance of the control system.It was effective in the steering control of agricultural robot.This method can provide a reference for the precise steering control of other robots.展开更多
In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to ...In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.展开更多
As an important resource in data link,time slots should be strategically allocated to enhance transmission efficiency and resist eavesdropping,especially considering the tremendous increase in the number of nodes and ...As an important resource in data link,time slots should be strategically allocated to enhance transmission efficiency and resist eavesdropping,especially considering the tremendous increase in the number of nodes and diverse communication needs.It is crucial to design control sequences with robust randomness and conflict-freeness to properly address differentiated access control in data link.In this paper,we propose a hierarchical access control scheme based on control sequences to achieve high utilization of time slots and differentiated access control.A theoretical bound of the hierarchical control sequence set is derived to characterize the constraints on the parameters of the sequence set.Moreover,two classes of optimal hierarchical control sequence sets satisfying the theoretical bound are constructed,both of which enable the scheme to achieve maximum utilization of time slots.Compared with the fixed time slot allocation scheme,our scheme reduces the symbol error rate by up to 9%,which indicates a significant improvement in anti-interference and eavesdropping capabilities.展开更多
基金Supported by the Aeronautical Science Foundation of China(2010ZB52011)the Funding of Jiangsu Innovation Program for Graduate Education(CXLX11-0213)the Nanjing University of Aeronautics and Astronautics Research Funding(NS2010055)~~
文摘The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gramming （SQP）. Firstly, a steady-state hybrid aero-engine model is designed in the whole flight envelope with a dramatic enhancement of real-time capability. Secondly, the aero-engine performance seeking control including the maximum thrust mode and the minimum fuel-consumption mode is performed by SQP. Finally, digital simu- lations for cruise and accelerating flight are carried out. Results show that the proposed method improves real- time capability considerably with satisfactory effectiveness of optimization.
基金supported by the National Natural Science Foundation of China(61304058,61233002)IAPI Fundamental Research Funds(2013ZCX03-01)
文摘This paper focuses on the H_∞ model reference tracking control for a switched linear parameter-varying(LPV)model representing an aero-engine. The switched LPV aeroengine model is built based on a family of linearized models.Multiple parameter-dependent Lyapunov functions technique is used to design a tracking control law for the desirable H_∞ tracking performance. A control synthesis condition is formulated in terms of the solvability of a matrix optimization problem.Simulation result on the aero-engine model shows the feasibility and validity of the switching tracking control scheme.
文摘Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. In this paper, a turbine tip clearance control apparatus and a model of turbine tip clearance are proposed; an implicit active generalized predictive control （GPC）, with auto-regressive （AR） error modification and fuzzy adjustment on control horizon, is presented, as well as a quantitative analysis method of robust per- turbation radius of the system. The active clearance control （ACC） of aero-engine turbine tip clear- ance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis of the stability and robustness of the active tip clearance control system. The results show that the resultant active tip clearance control system with the improved GPC has favorable steadystate and dynamic performance and benefits of increased efficiency, reduced specific fuel consump- tion, and additional service life.
基金National Nature Science Foundation of China(Nos.51675394and 51375196)National Key Research and Development Program of China(No.2017YFB1303404)+2 种基金State Key Laboratory of Digital Manufacturing Equipment and Technology of China(No.DMETKF2018018)Fundamental Research Funds for the Central Universities of China(No.2017II33GX)the Key R&D Program of Jiangsu Province(No.BE2015005)
文摘Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency,however,is difficult to be guaranteed in such a process.To overcome this problem,a method of hybrid force-position control combined with PI/PD control is proposed to be applied in robotic abrasive belt grinding of complex geometries.Voltage signals are firstly obtained and transformed to force information with signal conditioning methods.Secondly,zero drift and gravity compensation algorithms are presented to calibrate the F/T transducer which is installed on the robot end-effector.Next,a force control strategy combining hybrid force-position control with PI/PD control is introduced to be employed in robotic abrasive belt grinding operations where the force control law is applied to the Z direction of the tool frame and the positon control law is used in the X direction of the tool frame.Then,the accuracy of the F/T transducer and the robotic force control system is analyzed to ensure the stability and reliability of force control in the robotic grinding process.Finally,two typical cases on robotic belt grinding of a test workpiece and an aero-engine blade are conducted to validate the practicality and effectiveness of the force control technology proposed.
基金supported by National Natural Science Foundation of China(Grant No.51005184)National Science and Technology Major Project of Ministry of Science and Technology of China(Grant No.2009ZX04014-053)
文摘The existing methods for blade polishing mainly focus on robot polishing and manual grinding.Due to the difficulty in high-precision control of the polishing force,the blade surface precision is very low in robot polishing,in particular,quality of the inlet and exhaust edges can not satisfy the processing requirements.Manual grinding has low efficiency,high labor intensity and unstable processing quality,moreover,the polished surface is vulnerable to burn,and the surface precision and integrity are difficult to ensure.In order to further improve the profile accuracy and surface quality,a pneumatic flexible polishing force-exerting mechanism is designed and a dual-mode switching composite adaptive control(DSCAC) strategy is proposed,which combines Bang-Bang control and model reference adaptive control based on fuzzy neural network(MRACFNN) together.By the mode decision-making mechanism,Bang-Bang control is used to track the control command signal quickly when the actual polishing force is far away from the target value,and MRACFNN is utilized in smaller error ranges to improve the system robustness and control precision.Based on the mathematical model of the force-exerting mechanism,simulation analysis is implemented on DSCAC.Simulation results show that the output polishing force can better track the given signal.Finally,the blade polishing experiments are carried out on the designed polishing equipment.Experimental results show that DSCAC can effectively mitigate the influence of gas compressibility,valve dead-time effect,valve nonlinear flow,cylinder friction,measurement noise and other interference on the control precision of polishing force,which has high control precision,strong robustness,strong anti-interference ability and other advantages compared with MRACFNN.The proposed research achieves high-precision control of the polishing force,effectively improves the blade machining precision and surface consistency,and significantly reduces the surface roughness.
文摘PartⅠhas illustrated the procedures to apply the Linkage Learning Genetic Algorithm(LLGA)in Gas Turbine Engine(GTE)controller gains tuning and generated the optimization results for runway conditions from idle to takeoff.However,the total pressure and temperature of the engine inlet vary as the changing of altitude and Mach number,which would lead to the variation in fuel flow supply regulation.As a result,the optimized gains in runway might not be suitable for other flight conditions.In order to maintain the optimal control performance,the GTE controller gains should be adjusted according to the flight conditions.This paper extends the application of the LLGA method to other flight conditions and then simulates a complete flight mission with different gains and weather condition configurations.For this purpose,the control parameters in the Simulink model of the GTE controller are first corrected by the weather condition in altitude.Then,a typical flight mission is defined and divided into different flight segments based on the altitude and Mach number configuration.One representative point is selected from each segment as the datum point for optimization process.After this step,the LLGA method is used to find the best gains combinations for different flight conditions and the differences in optimization effects for different flight conditions are analyzed subsequently.The simulation results show that the optimization effect of the control performance of each flight condition is dependent on the value of(θδ)~(1/2)and the optimal K_(pla)in some flight conditions is approximately equal to p hd times of the Kplavalue in sea level standard condition.Finally,the complete flight mission is simulated with different gains and weather condition configurations.The simulation results show that the engine performance has been greatly improved after optimization by LLGA in the transient state and the high altitude conditions.In other steady states,the optimization effect is not very obvious.
基金supported by the National Science and Technology Major Project of China(No.J2019-I-0020-0019)。
文摘To perform transient state control of an aero-engine,a structure that combines linear controller and min–max selector is widely adopted,which is inherently conservative and therefore limits the fulfillment of the engine potential.Model predictive control is a new control method that has vast application prospects in the field of aero-engine control.Therefore,this paper proposes a wide-range model predictive controller that can control the engine over a wide range within the flight envelope.This paper first introduces the engine parameters and the model prediction algorithm used by the controller.Then a wide-range model prediction controller with a three-layer nested structure is presented.These three layers of the structure are univariate controller,nominal point controller,and wide-range controller from inside to outside.Finally,by analyzing and verifying the effectiveness of the univariate controller for small-range variations and the wide-range model predictive controller for large-range parameter variations,it is demonstrated that the controller can schedule the controller’s output based on inlet altitude,Mach number,and lowpressure shaft corrected speed,and ensure that the limits are not exceeded.It is concluded that the designed wide-range model predictive controller has good dynamic effect and safety.
基金the National Natural Science Foundation of China(Nos.51906103,52176009).
文摘The onboard adaptive model can achieve the online real-time estimation of performance parameters that are difficult to measure in a real aero-engine,which is the key to realizing modelbased performance control.It must possess satisfactory numerical stability and estimation accuracy.However,the positive definiteness of the state covariance matrix may be destroyed in filter estimation because of the existence of some uncertain factors,such as the accumulated measurement error,noise,and disturbance in the strongly nonlinear engine system,inevitably causing divergence of estimates of Cholesky decomposition-based Spherical Unscented Kalman Filter(SUKF).Therefore,this paper proposes an improved SUKF algorithm(iSUKF)and applies it to the performance degradation estimation of the engine.Compared to SUKF,the iSUKF mainly replaces the Cholesky decomposition with the Singular Value Decomposition(SVD),which is numerically stable without any strict requirement for the state covariance matrix.Meanwhile,a correction factor is designed to assess the measurement deviation between the real engine and the nonlinear onboard model to correct the state covariance matrix,thus maintaining better numerical stability of parameters estimated by the filter.Then,an offline correction strategy is also proposed to eliminate the influence of the degradation of unestimated health parameters or the filter’s inadequate estimation of the coupled health parameters.This action effectively promotes the onboard adaptive model’s estimation accuracy concerning the degradation of the engine’real health parameters and its performance parameters.Finally,the simulation results show that the iSUKF can maintain the numerical stability of the filter’s estimation of health parameters.Compared with the existing methods,the offline correction strategy improves the estimation accuracy of the iSUKF-based nonlinear onboard adaptive model for the performance parameters of the real engine by more than 50%.The proposed method will provide feasible technical support for model-based aero-engine performance control.
文摘A fault tolerant control method is proposed in this paper for a turbofan engine gas path degradation through the full flight envelope. A Quantum-behaved Particle Swarm Optimization(QPSO) algorithm is applied to obtain engine inputs adjustments, which contribute to construct off-line performance accommodation interpolation schedules. With a double closed-loop control system structure, command control is corrected based on real-time fault diagnostic results. Simulations indicate that fault tolerant control could reduce thrust and stall margin loss effectively in gas path faults.
基金co-supported by the National Science and Technology Major Project,China(No.J2019-I-0001-0001)the National Natural Science Foundation of China(No.52105545)。
文摘The original monitoring data from aero-engines possess characteristics such as high dimen-sionality,strong noise,and imbalance,which present substantial challenges to traditional anomalydetection methods.In response,this paper proposes a method based on Fuzzy Fusion of variablesand Discriminant mapping of features for Clustering(FFD-Clustering)to detect anomalies in originalmonitoring data from Aircraft Communication Addressing and Reporting System(ACARS).Firstly,associated variables are fuzzily grouped to extract the underlying distribution characteristics and trendsfrom the data.Secondly,a multi-layer contrastive denoising-based feature Fusion Encoding Network(FEN)is designed for each variable group,which can construct representative features for each variablegroup through eliminating strong noise and complex interrelations between variables.Thirdly,a featureDiscriminative Mapping Network(DMN)based on reconstruction difference re-clustering is designed,which can distinguish dissimilar feature vectors when mapping representative features to a unified fea-ture space.Finally,the K-means clustering is used to detect the abnormal feature vectors in the unifiedfeature space.Additionally,the algorithm is capable of reconstructing identified abnormal vectors,thereby locating the abnormal variable groups.The performance of this algorithm was tested ontwo public datasets and real original monitoring data from four aero-engines'ACARS,demonstratingits superiority and application potential in aero-engine anomaly detection.
基金National Natural Science Foundation of China (No. 51975200)Hunan Provincial Innovation Foundation for Postgraduate,China (No. QL20220201)。
文摘By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the grain sizes of K4169 superalloy significantly increase,and the precipitation of the needle-likeδphase and the Laves phase is observed.Voids and microcracks form at location of Laves phase enrichment,creating conditions for crack propagation.By the a−N(a is the crack length,and N is the number of cycles)relationship curve,the change in the fatigue crack growth rate with the increasing number of cycles progresses through three separate stages.The fracture process of K4169 superalloy under low-stress cyclic loading(3 kN)exhibits the ductile fracture.Subsequently,the fracture process starts to change from the ductile fracture to the brittle fracture as the stress increases to 4.5 kN.In the microstructures of fractures in both stress states,intergranular propagation is the mechanism responsible for crack propagation.Moreover,the Laves phase exists near the fracture crack,which is in line with the post-service structural phenomenon.
基金supported by the Equipment Test and Evaluation Technology Research Project,China(No.2100070017)the Natural Science Foundation of Gansu Province,China(No.24JRRA415)。
文摘Precise and quantitative measurement of soot particle emission plays an essential role in accurately assessing the combustion performance of aero-engine combustors and infrared signature levels in aircraft exhausts.Among various intrusive or non-intrusive approaches for soot diagnostics,Laser-Induced Incandescence(LⅡ)technique has been increasingly applied for soot concentration measurement in various combustion environments such as laminar flames and internal combustion engines due to its high spatial resolution and sensitivity.As for LⅡmeasurement in aero-engine combustors,however,it normally suffers from very limited optical accesses and often faces mandatory requirements of oblique imaging from a small backward angle.In this work,we demonstrate a Two-Color(2C)LⅡsystem that simultaneously captures LⅡsignal images at two distinct wavelengths using a Scheimpflug imaging configuration.A projective transformation algorithm and image overlapping procedures were employed to spatially correct the raw Scheimpflug LⅡimages.Performance validation of the developed 2C-Scheimpflug LⅡsystem was first conducted under specified conditions in a laminar C_(2)H_(4)/air McKenna flame.The obtained Soot Volume Fraction(SVF)level and its spatial distribution are in consistent with previous studies under identical flame conditions reported by other research groups.Finally,as a demonstration of engineering benchmark application,we applied the developed 2C-Scheimpflug LⅡsystem to measure SVF distribution in the cross-section plane perpendicular to the direction of flame propagation at the exhaust of a single-sector dual-swirl aero-engine model combustor.Transient soot production events were observed and characteristics of the SVF distribution were investigated.These experimental results suggest the feasibility of the 2C-Scheimpflug LⅡtechnique developed in this work for precise and quantitative measurements of soot concentration in practical environments.
基金the financial support from the National Key R&D Program of China(No.2023YFE0125900)National Natural Science Foundation of China(Nos.12372008 and 12102234)+1 种基金Natural Science Foundation of Heilongjiang Province,China(No.YQ2022A008)Taif University,Saudi Arabia,for supporting this work through Project number(TU-DSPP-2024-73).
文摘This paper analyzes the nonlinear dynamic characteristics and stability of Aero-Engine Dual-Rotor(AEDR)systems under high-frequency excitation,based on the Adaptive Harmonic Balance with the Asymptotic Harmonic Selection(AHB-AHS)method.A finite element dynamic equation for the AEDR system is introduced,considering complex nonlinearities of the intershaft bearing,unbalanced excitations,and high-frequency excitation.A solving strategy combining the AHB-AHS method and improved arclength continuation method is proposed to solve highdimensional dynamic equations containing complex nonlinearities and to track periodic solutions with parameter variations.The Floquet theory is used to analyze the types of bifurcation points in the system and the stability of periodic motions.The results indicate that high-frequency excitation can couple high-order and low-order modes,especially when the system undergoes superharmonic resonance.High-frequency excitation leads to more combination frequency harmonics,among which N_(f)ω_(1)-2ω_(2)dominates.Furthermore,changing the parameters(amplitude and frequency)of high-frequency excitation widens or shifts the unstable regions of the system.These findings contribute to understanding the mechanism of high-frequency excitation on aero-engines and demonstrate that the proposed AHB-AHS method is a powerful tool for analyzing highdimensional complex nonlinear dynamic systems under multi-frequency excitation.
基金supported in part by the National Science and Technology Major Project,China(No.2017-V-0004-0054)in part by the Research on the Basic Problem of Intelligent Aeroengine,China(No.2017-JCJQ-ZD-047-21)+1 种基金in part by the Fundamental Research Funds for the Central Universities,China(No.NZ2020002)in part by the National Natural Science Foundation of China(No.51906102)。
文摘Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control(LADRC)is proposed.Firstly,based on CFD numerical simulation,aerodynamic performance model of AVEN is established,and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed.Subsequently,the integrated model of AVEN/-turbofan engine is established by Simulink/AMESim co-simulation.Finally,the nozzle throat area control loop based on LADRC is designed.The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system.The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%,indicating a high degree of confidence.Compared with the conventional PID control,the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%,which effectively improves the control stability of the vector deflection.Meanwhile,the fuel flow ratechange during the vector deflection process is smaller and more economical,which provides an important reference for engineering applications.
基金supported by the National Key Research and Development Program of China(No.2020YFA0405700).
文摘Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, Laser-Induced Incandescence (LII) has been increasingly applied for soot concentration quantification in various combustion environments such as laminar flame, vehicle exhaust, internal combustion chamber as well as aero-engine combustor. In this work, we experimentally measured the spatial and temporal distribution of SVF using two-color LII technique at the outlet of a single-sector dual-swirl aero-engine model combustor. The effect of inlet pressure and air preheat temperature on the SVF distribution was separately investigated within a pressure range of 241–425 kPa and a temperature range of 292–500 K. The results show that soot production increases with the inlet pressure but generally decreases with the air preheat temperature. Qualitative analysis was provided to explain the above results of parametric studies. The LII experiments were also conducted under 3 designed conditions to evaluate soot emission under practical operations. Particularly, weak soot emission was detected at the outlet under the idle condition. Our experimental results provide a valuable benchmark for evaluating soot emission in the exhaust plume of this aero-engine combustor during practical operations.
基金support of the National Science and Technology Major Project of China(No.J2019-V-0005-0096)the National Key Research and Development Program of China(No.2020YFA0405700).
文摘The spatiotemporal distribution of soot concentration in aero-engine combustor is important for assessing its combustion performance.Here,we report experimental measurements of soot concentration in terms of Soot Volume Fraction(SVF)and its spatiotemporal distribution in a single-sector dual-swirl aero-engine combustor using Two-Color Laser-Induced Incandescence(2C-LII).It is shown that soot predominantly forms in the symmetrical vortices of the primary combustion zone,exhibiting a V-type distribution with higher concentration in the lower half of the zone than the upper half,with a small amount distributed in the secondary recirculation zone.Soot emissions at the combustor outlet are relatively low under three typical operating conditions by LII experiments,which is aligned with Smoke Number(SN)from gas analysis.The effect of inlet air temperature on SVF distribution and dynamics in the primary combustion zone is studied,which suggests that the SVF level in the primary combustion zone monotonically increases with the temperature.Meanwhile,the SVF distribution becomes more symmetrical as the inlet temperature increases,although the overall SVF level in the lower half of the zone is still higher.We also investigate the influence of the inlet air pressure on the SVF distribution at the combustor outlet.The soot concentration at the combustor outlet increases with inlet pressure,mainly distributed irregularly across both sides and the center.On both sides,the distribution is continuous,while the center exhibits dot-like and linear patterns.Numerical simulations correlated SVF distribution with the flow field in the primary combustion zone,qualitatively explaining the observed SVF distribution behavior.These results under various conditions can provide valuable insights for improving the performance of this specific combustor and designing high-temperature-rise combustors in the future.
基金National Natural Science Foundation of China! ( 6 98740 3 2 )The Youth Teacher Foundation of NPU
文摘The problem of analysis and synthesis of robust control is addressed in this work. The approach transferring the robust control design into Linear Matrix Inequality (LMI) is provided. The LMI standard structure of robust controller is also given and the controller is obtained through solving three LMIs. As an example, a robust control law is designed to the twin-spool turbojet engine system using the given approach. The result shows that LMI approach is feasible.
文摘Aiming to solve the steering instability and hysteresis of agricultural robots in the process of movement,a fusion PID control method of particle swarm optimization(PSO)and genetic algorithm(GA)was proposed.The fusion algorithm took advantage of the fast optimization ability of PSO to optimize the population screening link of GA.The Simulink simulation results showed that the convergence of the fitness function of the fusion algorithm was accelerated,the system response adjustment time was reduced,and the overshoot was almost zero.Then the algorithm was applied to the steering test of agricultural robot in various scenes.After modeling the steering system of agricultural robot,the steering test results in the unloaded suspended state showed that the PID control based on fusion algorithm reduced the rise time,response adjustment time and overshoot of the system,and improved the response speed and stability of the system,compared with the artificial trial and error PID control and the PID control based on GA.The actual road steering test results showed that the PID control response rise time based on the fusion algorithm was the shortest,about 4.43 s.When the target pulse number was set to 100,the actual mean value in the steady-state regulation stage was about 102.9,which was the closest to the target value among the three control methods,and the overshoot was reduced at the same time.The steering test results under various scene states showed that the PID control based on the proposed fusion algorithm had good anti-interference ability,it can adapt to the changes of environment and load and improve the performance of the control system.It was effective in the steering control of agricultural robot.This method can provide a reference for the precise steering control of other robots.
基金Supported in part by Natural Science Foundation of Guangxi(2023GXNSFAA026246)in part by the Central Government's Guide to Local Science and Technology Development Fund(GuikeZY23055044)in part by the National Natural Science Foundation of China(62363003)。
文摘In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.
基金supported by the National Science Foundation of China(No.62171387)the Science and Technology Program of Sichuan Province(No.2024NSFSC0468)the China Postdoctoral Science Foundation(No.2019M663475).
文摘As an important resource in data link,time slots should be strategically allocated to enhance transmission efficiency and resist eavesdropping,especially considering the tremendous increase in the number of nodes and diverse communication needs.It is crucial to design control sequences with robust randomness and conflict-freeness to properly address differentiated access control in data link.In this paper,we propose a hierarchical access control scheme based on control sequences to achieve high utilization of time slots and differentiated access control.A theoretical bound of the hierarchical control sequence set is derived to characterize the constraints on the parameters of the sequence set.Moreover,two classes of optimal hierarchical control sequence sets satisfying the theoretical bound are constructed,both of which enable the scheme to achieve maximum utilization of time slots.Compared with the fixed time slot allocation scheme,our scheme reduces the symbol error rate by up to 9%,which indicates a significant improvement in anti-interference and eavesdropping capabilities.
