Modified Sequential Kriging Optimization for Multidisciplinary Complex Product Simulation

Directing to the high cost of computer simulation optimization problem, Kriging surrogate model is widely used to decrease the computation time. Since the sequential Kriging optimization is time consuming, this article extends the expected improvement and put forwards a modified sequential Kriging optimization (MSKO). This method changes the twice optimization problem into once by adding more than one point at the same time. Before re-fitting the Kriging model, the new sample points are verified to ensure that they do not overlap the previous one and the distance between two sample points is not too small. This article presents the double stopping criterion to keep the root mean square error (RMSE) of the final surrogate model at an acceptable level. The example shows that MSKO can approach the global optimization quickly and accurately. MSKO can ensure global optimization no matter where the initial point is. Application of active suspension indicates that the proposed method is effective. © 2010 Chinese Journal of Aeronautics

Applying Technology to Improve Student Learning Outcomes in Dynamics Course

Motivating and stimulating students to learn material in required core engineering courses is difficult and yet essential in assuring student success. Traditional methods of teaching and learning need to be reconsidered and modified to meet student expectations and their continuously evolving ways of interaction with technology and social networks. Numerous faculty have been experimenting with various approaches which are taking advantages of both technology and student interaction with technology, with various degrees of success. In this paper authors present another comprehensive method applied in teaching/learning of core engineering mechanics course. It has been observed over a long period of time that Dynamics is one of the more difficult courses in the Mechanical Engineering and Technology programs where students are experiencing certain difficulty in mastering the material. Authors integrated technology into learning experiences in order to stimulate and motivate students to master the material, which proved to be very successful. It has been observed that new approach improved the final scores in the course as well as student satisfaction with this approach of presenting material as well as testing their understanding of the required material. The paper presents results from two years of teaching the course with the current approach, along with lessons learned from this experience

An Asynchronous Course/Laboratory Development for Automation Controls

The development of asynchronous courses is to help students who are restricted by work requirements, family responsibilities, geographical distance, disabilities, and combination of these factors. It also provides flexibilities to on-campus students. In this paper, the framework structure of an asynchronous course and laboratory development for an automation control is presented. The challenge in this development is to implement the hands-on laboratory experience to those distance learning students who may not be able to access the real equipment. Results of the implementation including opinion feedbacks and grade distributions show that students welcome the format of this development

Bayesian Model Averaging Based Storage Lifetime Assessment Method for Rubber Sealing Rings

Rubber sealing ring is one of the most widely used seals. It is always stored for a period of time before put into use, especially in aeronautic and aerospace applications. It is necessary to evaluate the storage lifetime of rubber sealing rings. However, due to the long storage lifetime of rubber sealing rings, two issues need to be handled, including model uncertainty and lack of storage lifetime data. A Bayesian model averaging based storage lifetime assessment method for rubber sealing rings is proposed in this article. The Gamma distribution model and Weibull distribution model are selected as the candidate models and combined based on Bayesian model averaging method. The Bayesian model averaging method is applied to handle the model uncertainty. Considering the lack of storage lifetime data, the degradation data are utilized to give the priors of model probability and distribution parameters based on the similarity principle. The results indicate that the proposed method has smaller minus log-likelihood value and is better than the other discussed method, considering both goodness of fit and complexity

Influence of Defects on In-Plane Dynamic Properties of Hexagonal Ligament Chiral Structures

Although the six-ligament chiral structure has many unique properties, due to its special structure, the stress concentration is prone to defects. In addition, additive manufacturing is also prone to defects. This paper studies the effect of defects, which is helpful for the better application of the six-ligament chiral structure. Several new six-ligament chiral structures with random and concentrated defects were designed to explore the effects of the defects on the in-plane dynamic properties. The structures were studied with the finite element ANSYS/LSDYNA numerical simulation and experimental methods. According to the defect-free six-ligament chiral structures exhibiting different deformation modes at different impact velocities, the effects of the defect rate and type (concentrated and random defects) on the six-ligament chiral structure, the in-plane impact deformation mode and energy absorption characteristics are discussed. The research results show that the defect rate and type reduce the energy absorption characteristics of the chiral structure to varying degrees, and the impact deformation mode also changes under medium- and low-speed impact. With the increase in speed, the influence of the defects on the deformation mode weakens. Moreover, the effects of the concentrated and random defects on the platform stress are different. When the defect rate is low, the effect of the random defects is more significant, and as the defect rate increases, the effect of the concentrated defects is more obvious. The study can provide guidance for structural design, predict the failure form of structures containing defects when they are impacted, and realize material recycling

Erosion Degradation Characteristics of a Linear Electro-Hydrostatic Actuator Under a High-Frequency Turbulent Flow Field

The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator (LEHA). Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics (CFD) method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization method is applied to update the concentration of contaminated particles within the LEHA, in order to gain insight into the erosion degradation process at various stages of degradation. The main contribution of the proposed model is the application of the dynamic concentration of contamination particles in erosion analysis of Electro-Hydraulic Servo Valves (EHSVs), throttle valves, spool valves, and needle valves. The effects of system parameters and working conditions on component wear are analyzed by simulations. The results of the proposed model match the expected degradation process. (C) 2017 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics

Integrative Experiences Through Modeling and Simulation of Mechatronic Systems

Learning is integrative lifelong process which requires continuous refreshing of old material and learning new material. This principle holds also for student experiences during their undergraduate studies. Students learn new material throughout their studies, and they may or may not have opportunity to use the material in different context and at different levels. As a result some of the acquired knowledge may be forgotten by the time student graduates or it may not be placed in the context of the overall program outcomes, thus material presented may not seem to have relevance to student\u27s career. An effective method to address this issue is a required capstone course that combines a number of different disciplines into a single comprehensive experience. In addition to required capstone experience, authors have collaborated in development of an elective course on modeling and simulation of mechatronic systems. The course introduces modern computer tools and techniques which integrates number of different areas including statics, strength of materials, dynamics, electrical systems, fluid systems, hydraulic systems, pneumatic systems, thermal systems, and control systems. The course provides several benefits including review of material covered at different stages of the undergraduate program, connecting different fields by analyzing mechatronic systems, and introduction to the tools that enable students to solve real world problems that cannot be solved analytically. Although some courses introduce the basics of modern computer tools, most do not have sufficient time to devote to modern computer tools. Hence, the introduction of a modeling and simulation course of mechatronic systems in the engineering technology program provides an opportunity to further improve the quality of the program and satisfy a number of ABET related learning outcomes

Mechanical Wear Debris Feature, Detection, and Diagnosis: A Review

Mechanical debris is an important product of friction wear, which is also a crucial approach to know the running status of a machine. Many studies have been conducted on mechanical debris in related fields such as tribology, instrument, and diagnosis. This paper presents a comprehensive review of these studies, which summarizes wear mechanisms (e.g., abrasive wear, fatigue wear, and adhesive wear) and debris features (e.g., concentration (number), size, morphology, and composition), analyzes detection methods principles (e.g., offline: spectrograph and ferrograph, and online: optical method, inductive method, resistive-capacitive method, and acoustic method), reviews developments of online inductive methods, and investigates the progress of debris-based diagnosis. Finally, several notable problems are discussed for further studies. (C) 2017 Chinese Society of Aeronautics and Astronautics

Fault Mode Probability Factor Based Fault-Tolerant Control for Dissimilar Redundant Actuation System

This paper presents a Fault Mode Probability Factor (FMPF) based Fault-Tolerant Control (FTC) strategy for multiple faults of Dissimilar Redundant Actuation System (DRAS) composed of Hydraulic Actuator (HA) and Electro-Hydrostatic Actuator (EHA). The long-term service and severe working conditions can result in multiple gradual faults which can ultimately degrade the system performance, resulting in the system model drift into the fault state characterized with parameter uncertainty. The paper proposes to address this problem by using the historical statistics of the multiple gradual faults and the proposed FMPF to amend the system model with parameter uncertainty. To balance the system model precision and computation time, a Moving Window (MW) method is used to determine the applied historical statistics. The FMPF based FTC strategy is developed for the amended system model where the system estimation and Linear Quadratic Regulator (LQR) are updated at the end of system sampling period. The simulations of DRAS system subjected to multiple faults have been performed and the results indicate the effectiveness of the proposed approach

Modeling of Reliability and Performance Assessment of a Dissimilar Redundancy Actuation System With Failure Monitoring

Actuation system is a vital system in an aircraft, providing the force necessary to move flight control surfaces. The system has a significant influence on the overall aircraft performance and its safety. In order to further increase already high reliability and safety, Airbus has implemented a dissimilar redundancy actuation system (DRAS) in its aircraft. The DRAS consists of a hydraulic actuation system (HAS) and an electro-hydrostatic actuation system (EHAS), in which the HAS utilizes a hydraulic source (HS) to move the control surface and the EHAS utilizes an electrical supply (ES) to provide the motion force. This paper focuses on the performance degradation processes and fault monitoring strategies of the DRAS, establishes its reliability model based on the generalized stochastic Petri nets (GSPN), and carries out a reliability assessment considering the fault monitoring coverage rate and the false alarm rate. The results indicate that the proposed reliability model of the DRAS, considering the fault monitoring, can express its fault logical relation and redundancy degradation process and identify potential safety hazards