Bifeng Song

Application of Prognostic and Health Management technology on aircraft fuel system

Prognostic and Health Management (PHM), which could provide the ability of fault detection (FD), fault isolation (FI) and estimation of remaining useful life (RUL), has been applied to detect and diagnose device faults and assess its health status, with aiming to enhance device reliability, safety, and reduce its maintenance costs. In this paper, taking an aircraft fuel System as an example, with virtual instrument technology and computer simulation technology, an integrated approach of signal processing method and model-based method is introduced to build the virtual simulation software of aircraft fuel PHM system for overcoming the difficulty in obtaining the failures information from the real fuel system. During the process of constructing the aircraft fuel PHM system, the first step is to analyze the fuel system failure modes and status parameters that can identify the failure modes. The main failure modes are determined as joints looseness, pipe broken, nozzle clogging, and fuel tank leakage. The status parameters are fuel pressure and fuel flow. Then, the status parameter model is constructed to imitate the behavior of sensor which detecting fuel system status. On this basis, utilizing the signal processing module provided by Labview software, the outputs from the virtual sensors, which collect the failure data, are processed to realize the simulation of failure detection and failure diagnosis. All the result shows that the virtual simulation software well accomplishes the task of the aircraft fuel system failure detection and diagnosis.

Exploring optimum power unit of propulsion system for high altitude airship

Different schemes of a propulsion system have a distinguished influence on the overall performance of high altitude airship. There is an optimum power, called optimum power unit, to achieve the lowest propulsion system and energy system weight for a high altitude airship. The paper represents an optimization model of the optimum power unit for a high altitude airship. Firstly, the optimal Latin hypercube design method is applied to obtain the sample points of the distributed low power propulsion system. Secondly, the surrogate model, which is used to establish the optimization model, is obtained by responding surface method based on these sample points. The computational model of the energy system is obtained by the airship’s location and the working time. Finally, the multi-island genetic algorithm is used to find the optimum power unit for a typical high altitude airship. Furthermore, the optimization work under different typical power levels and diameters is carried out to verify the effectiveness of the optimum power unit design method. It has been found that the identical result validates the effectiveness of the optimum power unit design method.

Modeling and dynamic simulation study of big inertia propulsion system of high altitude airship

Propulsion system is one of the most important parts of high altitude airship. Its really a need to build a simulation model of propulsion system and make some analysis about high altitude airship. An integrative model is established according to the matching of the torque between Rare earth permanent magnet Brushless DC motor[1∼2] and propeller in the use of Matlab/Simulink. Vast work is spent on making a plenty test of this integrative model. Also a series of analysis of the pull, torque and real absorb power generated by big inertia propulsion system in different working conditions is made in this passage. At last, the property envelop of this propulsion system is got. System efficient trend with the change of propeller diameter is got through simulating.

Damage location and identification of the wing structure with Probabilistic Neural Networks

The subject of Structural Health Monitoring (SHM) is emerging as an area of interest for aerospace, mechanical and automotive industry. It is defined as a system with the ability to continuously and automatically monitor the physical states of a structure and outer environment by means of embedded or attached sensors. Then, the SHM system can interpret adverse changes caused by the structure damage with the intention of improving the structures reliability and reducing the maintenance cost. Therefore, the key of implementation of SHM is that SHM system knows what changes in the structure to look for and how to identify them. Usually, the process of the damage identification is to detect the damage, extract the features which can accurately represent the characteristic of the damage, and identify the damage. Although, there has been an amount of work performed in the area of SHM, most efforts are focusing on civil structures and the technology level has reached some modest degree of maturing. For the particular structures like the aircraft structure, due to its special characteristics, there will be a lot of problems needed for analysis. In this paper, taking the aircraft wing structure as an example, its finite element model has been constructed to simulate the fifteen damage patterns according to the actual mechanical properties of the wing structure. Combined with the dissymmetry of the geometry characteristic of the wing structure, the change of the natural frequency is extracted as the feature parameter. Then, the damage feature vector based on the feature parameters is constructed as the input vector of the Probabilistic Neural Network (PNN). Finally, taking σ =0.1, 0.05, 0.01 and 0.001 respectively, the PNN is trained with the damage training samples, and the ability of damage identification of the PNN is vivificated by the verification samples. The results of the PNN training and verification show that the damages of the upper and lower skin at the front spar are hard to distinguish correctly. In order to recognize them correctly, the PNN must increase other feature parameters which are more sensitive to the damages at the two locations. Anyway, the method of PNN has great identification effect for the wing structure, and it can be applied to the aircraft structure health monitoring.

Mechanism reliability simulation analysis for multi-support axis seizure considered assembly tolerance

The deflection of some supports, which is caused by the external force or the tolerances in the manufacture and assembly procedure, will induce seizure of the mechanism with multi-support axis. However, only a few researchers investigated the seizure reliability of mechanism, and they were focused on the simplified models of some simple mechanisms. In recent years, the reliability simulation analysis based on computer simulation technique is widely adopted to improve the reliability of the complex mechanism in practice, and the reliability analysis is fulfilled by introducing the random parameters to the mechanism model in the simulation. In this paper, the reliability analysis for the multi-support axis seizure of a door mechanism, which is caused by the assembly tolerance, is investigated. The rigid-flexible coupling model of the door mechanism is built in the commercial software LMS Virtual.Lab. The parameterized expression of the assembly tolerance is introduced to the simulation by the advanced mesh transformation so called mesh morphing technique. The results data corresponding to the failure mode are obtained based on plenty of simulations using the parametric model. Then, the approximate model for the limit state function is generated using the support vector regression machine based on the results data. Finally, the reliability analysis and evaluation for the multi-support axis seizure of the door mechanism are achieved using the approximate mode. In our research, an integrated platform for mechanism reliability simulation analysis is also developed using the commercial software LMS Virtual.Lab, and the simulation results show that the developed platform might be efficient for the reliability analysis of complex mechanism.

Reliability analysis of the flap mechanism with multi-pivots

The flap is an over constrained mechanism with multiple pivots, which assembled along a common axis on the wing. Practically, due to various errors and structure deformation caused by aerodynamic load, its hard to make sure that the pivots are coaxial. Some pivots which deviate from the axis will have undesirable impacts on the dynamic performance of the mechanism when the flap runs up and down. Severely, the mechanism will be seizure and the entire system will be failure. As one of the most important mechanisms in aircraft, the reliability of the flat is crucial for the safety and reliability of the aircraft, and it is of great significance to improve its reliability. In this paper, a highly parametric analytical model is developed using dynamic simulation software. Based on the model, the reliability of the mechanism is calculated by combining the means of Response-surface and Monte-Carlo simulation. Finally, the sensitivity analysis for driving torque provides some useful information for the flap reliability optimization.

Kinetic reliability analysis of space four-links mechanism considering wear

In this paper, the characteristics of the kinetic reliability of space four-links mechanism are analyzed and the relationship between the kinetic accuracy and wear clearances in joints is explored, using Advanced First Order and Second Moment (AFOSM) method and Monte-Carlo Simulation (MCS). The Archard wear model is applied to analyze the increasing wear clearances in joints; and the function between the joint clearance and the equivalent length of links is built; then the kinetic accuracy of the space four-links mechanism with the increase of wear clearances is analyzed. Finally a demonstrative application is given, illustrating the reliability degradation of kinetic accuracy with the increase of wear clearances, and AFOSM has much higher computational efficiency compared with MCS. Besides, the influence of the contact forces in joints to the kinetic accuracy of space four-links mechanism is analyzed, with instructive results for the design of space four-links mechanism in engineering applications.

The Reliability and Sensibility Analysis for an Aircraft Lock Mechanism Based on the Surrogate Models

In order to analyze the reliability of the new lock mechanism which is an important part of aircraft cabin door system, this paper studies the reliability and sensitivity for the lock mechanism based on surrogate models and variance methods respectively. Function hazard analysis (FHA) and failure mode effects analysis (FMEA) of lock mechanism is studied firstly. Then, based on dynamics simulation model, performance function and various random variables, the widely used surrogate models of lock mechanism is established and verified. Based on the most accurate metamodel which has been established, the unlocking reliability which is the most hazardous function is calculated. Finally, the variance-based sensitivity method is used for sensitivity analysis of influence factors, the result shows that the tension of lock-hook from lock-ring is the largest influence factor on the unlocking reliability, which could contribute to the analysis and further improvement of lock mechanism.Copyright

Exploring design of universal propeller simulator for airship propulsion system’s driving motor

Rare earth permanent magnet brushless direct current motor is the energy conversion device between power system and propeller of high-altitude airship. Its performance has a profound effect on the overall performance of the high-altitude airship. Limited by the output torque of the permanent magnet brushless direct current motor, propeller on the ground cannot reach the rated angular speed when propeller works at high altitude, so it is difficult to carry on rotation test on the ground. In addition, performances of the permanent magnet brushless direct current motor system such as control accuracy, reliability and efficiency cannot be tested. The functional level of the motor load simulator is proposed considering the dynamic properties of the propeller and the basic functions of the propulsion system. Different loading actuators are evaluated and the conceptual design of the load simulator is accomplished. Inertia is realized by relatively small flywheel and inertia electrical emulation method. Torque is simulated by servo motor that can work at braking state and thrust is exerted on the motor by hydraulic servo valve control system. Finally, depending on the proposed scheme and design parameters, co-simulation model of the load simulator is established utilizing software MATLAB/Simulink and AMESim. After comparing co-simulation results with real propeller properties, the feasibility of the conceptual design of permanent magnet brushless direct current motor load simulator is proved, and what is more, the effectiveness of control strategies and the rationality of parameters settings for co-simulation are testified.

An analysis of mechanism kinematics accuracy based on linear elastic

The simulation-based prediction of the mechanism kinematics accuracy is of great importance in engineering application. For widely used and low-cost open-loop mechanism having no feedback signals, it is important to take a balance between economic consideration and high accuracy requirement, thus containing high research value. Based on current widely used methods, this paper proposes a more precise method to revise the kinematics accuracy of movement mechanism. Considering the manufacture error and joint clearance in mechanism, we reckon in elastic deformation displacement caused by gravity load and inertia force, that the analytic expression of displacement correction is presented, and that it is independent of the Business Software. Theoretical analysis and case studies show that this amendment for the precision request is necessary.