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Aircraft air conditioning system health state estimation and prediction for predictive maintenance

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Chinese Journal of Aeronautics 2020年第3期33卷 947-955页

作者： Jianzhong SUN Fangyuan WANG Shungang NING Department of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The vast potential of system health monitoring and condition based maintenance on modern commercial aircraft is being realized through the innovative use of Airplane Condition Monitoring System(ACMS) *** there are few methods addressing the issues of failure prognostics and predictive maintenance for commercial aircraft Air Conditioning System(ACS).This study developed a Bayesian failure prognostics approach using ACMS data for predictive maintenance of ***, a health index characterizing the ACS health state is inferred from a multiple sensor signals using a data driven *** a dynamic linear model is proposed to describe the degradation process for failure *** inference formulas are carried out for degradation estimation and *** developed approach is applied on a passenger aircraft fleet with ACMS data recorded for one *** analysis of the case study shows that the developed method can produce satisfactory prognostics results, where all the ACS failure precursors are identified in advance, and the relative errors for the failure time prediction made when just entering the degradation warning stage are less than 8%.This would allow operators to proactively plan future maintenance.

关键词： Aircraft air conditioning system Bayesian method Failure prognostics Health index Predictive maintenance

Robust optimization of control command for aerospace vehicles with aerodynamic uncertainty

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Chinese Journal of Aeronautics 2022年第12期35卷 226-241页

作者： Rui CAO Yanbin LIU Yuping LU College of Automated Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

To reduce the design burden of Aerospace Vehicles(ASVs)control systems,this paper proposes a multi-constrained robust trajectory optimization method,which provides a good front-end input for the control *** from the conventional aircraft,some control performance of ASVs is not only related to the model parameters,but also affected by the flight ***,the robust optimization method combines this characteristic of ASVs,sets the control performance as one of the optimization objectives,and considers the influence of parameter *** this method,the polynomial chaos expansion algorithm is used to transform the trajectory optimization problem with uncertain parameters into the equivalent deterministic robust trajectory optimization ***,compared with traditional deterministic trajectory optimization methods to illustrate the effectiveness of proposed control optimization method.

关键词： Aerospace vehicle Multi-objective optimization Polynomial chaos Uncertain systems

A new concept and preliminary study of variable hypersonic inlet with fixed geometry based on shockwave control

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Science China(Technological Sciences) 2007年第5期50卷 644-657页

作者： TAN HuiJun CHEN Zhi LI GuangSheng College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The inlet plays a significant role in the hypersonic airbreathing propulsion. A fixed-geometry inlet is troubled by low air-capture ratio and large additional drag while operating below the design Mach number. Whereas a variable-geometry inlet can maximize performance, but adds weight and complexity to the propulsion system. Based on a fluidic shock shape control technique, this paper proposes a new concept of variable hypersonic inlet with fixed geometry, gives the realization scheme, and conducts a preliminary validation. The results show that the control of the external shock system and the effective throat area can be achieved by the self-provided high pressure fluid of the inlet. For an inlet with an operating Mach-number region of 4 to 6, the shock-on-lip condition can be maintained from Mach 5 to Mach 6 with the maximum expense of 1.8% secondary flow ratio, result- ing in 20% extra captured mass flow and 8% less forebody drag at low Mach num- bers compared with conventional fixed-geometry inlets. Thus, the performance enhancement by using the proposed variable inlet can substantially benefit the acceleration process of hypersonic vehicles at low Mach numbers.

关键词： hypersonic inlets, variable inlets, shock shape control technique

DETERMINATION OF INTERNAL STRAIN IN 3-D BRAIDED COMPOSITES USING OPTIC FIBER STRAIN SENSORS

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Acta Mechanica Solida Sinica 2004年第1期17卷 52-57页

作者： YuanShenfang HuangRui LiXianghua LiuXiaohui TheAeronauticKeyLaboratoryforSmartMaterialsandStructures NanjingUniversityofAeronauticsandAstronauticsNanjing210016China

A reliable understanding of the properties of 3-D braided composites is of primary importance for proper utilization of these materials. A new method is introduced to study the mechanical performance of braided composite materials using embedded optic fiber sensors. Experimental research is performed to devise a method of incorporating optic fibers into a 3-D braided composite structure. The efficacy of this new testing method is evaluated on two counts. First, the optical performance of optic fibers is studied before and after incorporated into 3-D braided composites, as well as after completion of the manufacturing process for 3-D braided composites, to validate the ability of the optic fiber to survive the manufacturing process. On the other hand, the influence of incorporated optic fiber on the original braided composite is also researched by tension and compression experiments. Second, two kinds of optic fiber sensors are co-embedded into 3-D braided composites to evaluate their respective ability to measure the internal strain. Experimental results show that multiple optic fiber sensors can be co-braided into 3-D braided composites to determine their internal strain which is difficult to be fulfilled by other current existing methods.

关键词： braided composites optic fiber sensor mechanical properties strain measurement

Abrasive-assisted Nickel Electroforming Process with Moving Cathode

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Chinese Journal of Mechanical Engineering 2017年第2期30卷 294-300页

作者： Jianhua REN Zengwei ZHU Chunqiu XIA Ningsong QU Di ZHU College of Mechanical and Electrical Engineering NanjingUniversity of Aeronautics and AstronauticsNanjing 210016China

In traditional electroforming process for revolving parts with complex profiles, the drawbacks on surface of deposits, such as pinholes and nodules, will lead to varying physical and mechanical properties on different parts of electroformed components. To solve the problem, compositely moving cathode is employed in abrasive-assisted electroforming of revolving parts with complicated profiles. The cathode translates and rotates simultaneously to achieve uniform friction effect on deposits without drawbacks. The influences of current density and transla- tion speed on the microstructure and properties of the electroformed nickel layers are investigated. It is found that abrasive-assisted electroforming with compound cathode motion can effectively remove the pinholes and nodules, positively affect the crystal nucleation, and refine the grains of layer. The increase of current density will lead to coarse microstructure and lower micro hardness, from 325 HV down to 189 HV. While, faster translational linear speed produces better surface quality and higher micro hardness, from 236 HV up to 283 HV. The weld-ability of the electroformed layers are also studied through the metallurgical analysis of welded joints between nickel layer and 304 stainless steel. The electrodeposited nickel layer shows fine performance in welding. The novel compound motion of cathode promotes the mechanical properties and refines the microstructure of deposited layer.

关键词： Nickel electroforming · Abrasive · Compound motion · Weldability

Dynamic modeling and nonlinear control strategy for an underactuated quad rotor rotorcraft

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 539-545页

作者： Ashfaq Ahmad MIAN College of Automation Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

In this paper, a nonlinear dynamic MIMO model of a 6-DOF underactuated quad rotor rotorcraft is derived based on Newton-Euler formalism. The derivation comprises determining equations of motion of the quad rotor in three dimensions and seeking to approximate the actuation forces through modeling of the aerodynamic coefficients and electric motor dynamics. The derived model is dynamically unstable, so a sequential nonlinear control strategy is implemented for the quad rotor. The control strategy includes exact feedback linearization technique, using the geometric methods of nonlinear control. The performance of the nonlinear control algorithm is evaluated using simulation and the results show the effectiveness of the proposed control strategy for the quad rotor rotorcraft near quasi-stationary flight.

关键词： Quad rotor rotorcraft MIMO model Underactuated systems

DIRECT MANIPULATION OF B-SPLINE SURFACES

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Chinese Journal of Mechanical Engineering 2005年第1期18卷 103-108页

作者： WangZhiguo ZhouLaishui WangXiaoping CollegeofMechanicalandElectricalEngineering CAD／CAMResearchCenterNanjingUniversityofAeronauticsandAstronauticsNanjng210016China

Engineering design and geometric modeling often require the ability to modifythe shape of parametric curves and surfaces so that their shape satisfy some given geometricconstraints, including point, normal vector, curve and surface. Two approaches are presented todirectly manipulate the shape of B-spline surface. The former is based on the least-square, whereasthe latter is based on minimizing the bending energy of surface. For each method, since unified andexplicit formulae are derived to compute new control points of modified surface, these methods aresimple, fast and applicable for CAD systems. Algebraic technique is used to simplify the computationof B-spline composition and multiplication. Comparisons and examples are also given.

关键词： NURBS Bending energy Fairness Kronecker product Stiffness matrix

Mechanism of Carbon Nanotubes Aligning along Applied Electric Field

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Chinese Physics Letters 2008年第1期25卷 270-273页

作者：马少杰郭万林 Institute of Nano Science Nanjing University of Aeronautics and Astronautics Nanjing 210016

The mechanism of single-walled carbon nanotubes （SWCNTs） aligning in the direction of external electric field is studied by quantum mechanics calculations. The rotational torque on the carbon nanotubes is proportional to the difference between the longitudinal and transverse polarizabilities and varies with the angle of SWCNTs to the external electric field. The longitudinal polarizability increases with second power of length, while the transverse polarizability increases linearly with length. A zigzag SWCNT has larger longitudinal and transverse polarizabilities than an armchair SWCNT with the same diameter and the discrepancy becomes larger for longer tubes.

关键词： STATIC POLARIZABILITY GROWTH

ROBUST DESIGN OF A TWO DEGREE FREEDOM *** TO THE PARAMETER UNCERTAINTY

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Chinese Journal of Mechanical Engineering 2008年第6期21卷 30-35页

作者： ZANG Chaoping College of Energy and Power Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

A method based on the robust design optimization is presented to handle the structural uncertainty problems. The variations caused in dynamic performance can be expressed by the mean response and the standard deviation of the performance. The robust optimization approach, based on a multi-objective and non-deterministic method, attempts to both optimize the mean performance and minimize the variance of the performance simultaneously. The best possible design optimization is chosen by a trade-off decision. An example of robust design of a two degree freedom system is used to effectively illustrate the application in dynamics. The mass and stiffness uncertainty in the main system as well as the uncertainty of the mass, stiffness and damping in the absorber are considered all together in order to minimize the displacement response of the main system within a wide band of excitation frequencies. The robust optimization results show a significant improvement in performance compared with the conventional solution recommended from vibration textbooks. It is indicated that robust design methods have great potential for application in structural dynamics to deal with uncertainty problems.

关键词： Robust design Optimization Dynamics