Opportunistic preventive maintenance optimization for multi-unit series systems with combing multi-preventive maintenance techniques

This paper proposes a dynamic opportunistic preventive maintenance (PM) optimization policy for multi-unit series systems by integrating multi PM techniques. Two PM techniques, periodic PM and sequential PM, are considered. Whenever one of the units reaches its reliability threshold, a PM action has to be performed on that unit. At that time the whole system has to be stopped and PM opportunities arise for the other units of the system. An optimal PM practice is determined by maximizing the short-term cumulative opportunistic maintenance (OM) cost savings for the whole system. Numerical examples are given to show how this approach works. Finally, a comparison between the proposed PM policy and the other policies is given.     

On the algorithms of adaptive neural network-based speed control of switched reluctance machines

AbstractA switched reluctance machine(SRM)drive is a time-varying,strongly nonlinear system.High performance control can no longer be achieved by using linear techniques.This paper describes the back-propagation (BP)neural network-based proportional-integral-derivative(PID)speed control of the SRM.It’s the interest of this paper to explore the utilization of the prior empirical knowledge as guidance in the initializing and training of the neural networks.The purpose is to make the networks less sensitive on the initial weights.Two modified algorithms are presented and simulation experiments show some interesting findings about their control effects and their corresponding sensitivity on the initial weights of the networks.     

3D Numerical simulation of non-isothermal resin transfer molding filling process using unstructured tetrahedron mesh

We present a numerical formulation for resin flow based on the concept of quasi-steady state situation at the flow front. To be fit for complicated product shapes, we use the four-node unstructured tetrahedron mesh based on which the numerical formulation of temperature and degree of cure is developed. The validity of our method is established in the case where flexible meshes are used. The results show that the numerical procedure, tested on known data, provides numerically valid and reasonably accurate predictions.     

Stochastic analysis of the variation in injury numbers of automobile frontal crash tests

Although automobile crash test data have a comparatively large variation because of the complexity of the tests, only a limited number of crash tests are usually conducted due to monetary and time limitations. Thus, it is necessary to control input variables that cause the variation in test data to obtain consistent crash test results and to correctly assess the safety performance of an automobile under development. In this study, a MADYMO model was validated deterministically to yield the head, chest, pelvis deceleration pulses of anthropomorphic test devices and the belt load pulses similar to those from actual tests, and it was also validated stochastically to yield means and standard deviations of the head and chest injury numbers, i.e., HIC ₁₅ and 3 msec clip similar to those from actual tests. A stochastic analysis was conducted using the validated MADYMO model to calculate the sensitivity of the standard deviations of the injury numbers to the standard deviations of influential input variables to determine the most influential input variable that makes the largest contribution to the variation in the injury numbers. Moreover, the Taguchi approach was used to determine the optimal values of the influential input variables to improve safety performance.     

Age and cross-cultural comparison of drivers’ cognitive workload and performance in simulated urban driving

Driving demands significant psychomotor attention and requires even more when drivers are engaged in secondary tasks that increase cognitive workload and divert attention. It is well established that age influences driving risk. Less is known about how culture impacts changes in attention. We conducted parallel driving simulations in the US and Korea to measure the extent to which age and culture influence dual-task performance. There were 135 participants divided into two groups: a younger group aged 20∼29, and an older group aged 60∼69. Whereas some differences by culture appeared in absolute control measures, the younger participants showed similar mean velocity and compensatory patterns associated with increased cognitive load in the urban setting; however, the results from the older samples were less similar.     

Analytical study to estimate the performance of the Power Shift Drive (PSD) Axle for a forklift

In this study, a new concept for a power delivery system is developed. Power Shift Drive (PSD) Axle vehicle modeling and dynamic movement analysis are performed via simulation. The dynamic vehicle model is constructed from data obtained from the derived equation, considering the specific characteristics of each part. The model is composed of a torque converter, a gear box, a differential, hub reduction and an engine, which is the power source of the 1st forward and reverse PSD-Axle. By unifying the mathematical equations for each component, a mathematical model of the 1st forward gear is derived. The system dynamic model is created using MATLAB/Simulink based on the mathematical model. Simulation is carried out using Simulink to estimate the dynamic behavior of the PSD-Axle. In addition, the dynamo test result is used to verify the model. Finally, a successful model is created. This study will be used to establish the basic conceptual design for the PSD-Axle multi-gear system.     

Injury analysis of pedestrians in collisions using the pedestrian deformable model

Vehicle safety has become the most important issue in automobile design. However, all efforts to improve safety devices focus on enhancing safety features for occupants. Notably, pedestrians are the second largest category of motor vehicle deaths, after occupants, and account for about 13 percent of motor vehicle deaths. It is essential to design pedestrian-friendly vehicles and pedestrian protection systems to reduce pedestrian fatalities and injuries. To effectively assess pedestrian injuries resulting from vehicle impact, a deformable pedestrian model must be developed for vehicle-pedestrian collision analysis. This study constructs a pedestrian-collision numerical model based on LS-DYNA finite element code. To verify the accuracy of the proposed deformable pedestrian model, experimental data are used in the pedestrian model test. This study applies the proposed model to analyze the dynamic responses and injuries of pedestrians involved in collisions. The modeled results can help assess vehicle pedestrian friendliness and assist in the future development of pedestrian-friendly vehicle technologies.     

Development of the Sungkyunkwan University Driving Simulator (SKUD) for Human-Machine Interface studies of Car Navigation Systems

Driving simulators are useful tools that can be used not only to test the components of future cars, but also to evaluate the telematics service and HMI (Human-Machine Interface). However, driving simulators that are currently available cannot be implemented to test and evaluate a real commercial telematics service system because the GPS (Global Positioning System), which contains basic functional support for the telematics module, does not work in the VR (virtual reality) environment. A driving simulator, together with the GPS simulator, can be used to study the HMI to evaluate commercial CNS (Car Navigation Systems). In this paper, Sungkyunkwan University Driving Simulator (SKUD) is developed with a GPS simulator that is able to emulate GPS satellite signals and includes the NMEA-0183 protocol and RS232C communication standards. Furthermore, using the SKUD, the HMI of the real commercial CNS could be investigated with driver workload assessment methods.     

六边形钢丝网状加筋拉拔特性试验研究

以六边形钢丝网作为加筋材料,在室内模拟拉拔试验箱中进行了大型拉拔试验。得出了在不同的法向应力条件下六边形钢丝网的拉拔强度、破坏模式以及不同部位位移变化规律。     

Effects of mixture stratification on HCCI combustion of DME in a rapid compression and expansion machine

Compression ignition of homogeneous charges in internal combustion (IC) engines is expected to offer high efficiency of DI diesel engines without high levels of NOx and particulate emissions. This study is intended to find ways of extending the rich limit of HCCI operation, one of the problems yet to be overcome. Exhaust emissions characteristics are also explored through analyses of the combustion products. DME fuel, either mixed with air before induction or directly injected into the combustion chamber of a rapid compression and expansion machine, is compressed to ignite under various conditions of compression ratio, equivalence ratio, and injection timing. The characteristics of the resulting combustion and exhaust emissions are discussed in terms of the rate of heat release computed from the measured pressure, and the concentrations of THC, CO, and NOx are measured by FT-IR and CLD. The experimental data to date show that operation without knock is possible with mixtures of higher equivalence ratio when DME is directly injected rather than when it is inducted in the form of a perfectly homogeneous fuel-air mixture. Although fuel injected early in the compression stroke promotes homogeneity of the DME-air mixture in the cylinder, it causes the mixture to ignite too early to secure good thermal efficiency and knock-free operation at high loads. Low temperature reactions occur at about 660K regardless of the fueling methods, fuel injection timing and equivalence ratio. The main components of hydrocarbon emissions turned out to be unburned fuel (DME), formaldehyde and methane.