Experimental investigation of TARMAX model for modeling of hydrodynamic forces on cylinder-like structures

A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous (ARMAX) input and its time-varying form, TARMAX. Model structure selection and parameter estimation were discussed while considering the validation stage. In this paper, the cylindrical structure was considered as a dynamic system with an incoming water wave and resulting forces as the input and outputs, respectively. The experimental data, used in this study, were collected from a full-scale rough vertical cylinder at the Delft Hydraulics Laboratory. The practicality of the proposed method and also its efficiency in structural modeling were demonstrated through applying two hydrodynamic force components. For this purpose, an ARMAX model is first used to capture the dynamics of the process, relating in-line forces provided by water waves;secondly, the TARMAX model was applied to modeling and analysis of the lift forces on the cylinder. The evaluation of the lift force by the TARMAX model shows the model is successful in modeling the force from the surface elevation.     

Experimental and numerical investigation of fuel mixing effects on soot structures in counterflow diffusion flames

Experimental and numerical analyses of laminar diffusion flames were performed to identify the effect of fuel mixing on soot formation in a counterflow burner. In this experiment, the volume fraction, number density, and particle size of soot were investigated using light extinction/scattering systems. The experimental results showed that the synergistic effect of an ethylene-propane flame is appreciable. Numerical simulations showed that the benzene (C₆H₆) concentration in mixture flames was higher than in ethylene-base flames because of the increase in the concentration of propargyl radicals. Methyl radicals were found to play an important role in the formation of propargyl, and the recombination of propargyl with benzene was found to lead to an increase in the number density for cases exhibiting synergistic effects. These results imply that methyl radicals play an important role in soot formation, particularly with regard to the number density.     

Lubrication characteristics of spiral groove liquid seals for use in the carrier of a vane-type external LPG fuel pump

We analyzed the lubrication characteristics of a design-selected spiral groove liquid seal for the critical component, the carrier, of a rotary vane-type fuel pump developed for external installation on fuel tanks for liquid phase LPG (liquefied petroleum gas) injection (LPLi) vehicles, with the aim of fundamentally improving lubrication performance and so protecting the carrier from early frictional wear damage at its suction face. The main reason for selecting a spiral groove pattern was because the viscosity of liquid LPG is very low, comparable to that of air, and current commercial dry gas seals adopting spiral grooves have been successfully employed in completely noncontacting applications. Utilizing the Galerkin finite element lubrication analysis method, a detailed lubrication characteristic analysis of the seal was performed, and lubrication performance optimization was performed by systematic parameter analyses of the design variables. Compared to the initial reference design, the final optimized spiral groove seal design had a groove depth increased by 66.7% and an equilibrium seal clearance increased by 65.3%. Our model also predicted that under a condition of equilibrium between the closing force of the pumping pressure and the seal opening force, the optimally designed carrier spiral groove liquid seal was capable of maintaining a stable lubricating film with sufficient axial stiffness and thereby demonstrated successful noncontact operation; in addition, leakage through the seal was minimal.     

Finite-element analysis of quasistatic fracture in CV joints under full-turn and full-throttle conditions

Quasistatic fractures at high joint angles constitute a chronic quality problem in CV joints. This type of fracture occurs when a driver unintentionally depresses the brake and accelerator simultaneously under a full-turn retreat condition. In general, the cage in a ball joint can be broken only at these high joint angles. Here we present a flexible quasistatic simulation model developed to simulate fracture in a CV joint. The cause and process of the quasistatic fracture were analyzed using simulations and physical tests. Static fracture simulations and tests at high joint angles showed that, initially, only one of the six cage posts was damaged. In a simulation of one revolution at constant torque, we found that an imbalance in ball loads generated an excessive cage load. Moreover, if this high cage load was applied when the cage protruded outward, the cage post was subjected to severe shear loading. The cage post was damaged in this specific rotational range. Quasistatic fracture simulations and tests at high joint angles showed that all six cage posts were damaged sequentially. Because entire cage posts were damaged, the quasistatic fracture torque was approximately half of the static torque. The plastic strain in each cage post displayed one step-like jump per revolution in the quasistatic simulations. The ball indentation created by a high ball load was interrupted by the cage-window edges as the ball joint rotated. This hindrance by ball indentation triggered the final breakage of the cage, although it was not the major cause of cage fractures.     

Dynamic correction of the steering-characteristic curve and application to an EPS control system

The steering torque of an electric-power steering (EPS) motor is interrelated with the performance of the EPS control system, therefore calculating an exact steering torque is critical in this application. This study presents a dynamic correction method that greatly decreases the calculated error in the steering torque; the PID controller demonstrated here is therefore suitable for the demands of this system. Based on an analysis of the detection process of the steering torque sensor, we first deduced that the variation of the system resistance torque equals the difference between the measured value of the steering torque and the ideal one in the previous cycle. Based on this result, we then proposed a dynamic correction method. Finally, a comparison of the simulated and experimental results for several vehicles evidenced the effectiveness of this dynamic correction method.     

Sensorless adaptive speed control of a permanent-magnet dc motor for anti-lock brake systems

An adaptive control algorithm was developed for the sensorless speed control of a permanent-magnet DC motor directly connected to the hydraulic pump of an antilock brake system. Due to the severe cost and reliability constraints of the application, the motor speed was controlled by a very simple on-off switching method, in which the only measurement required is the voltage across the control switch. The motor speed was calculated solely from the back-EMF voltage during the period of the control cycle when the switching controller is in the switch-off mode. The stability of the developed adaptiveswitching control algorithm was proven mathematically and confirmed experimentally in several vehicle tests over a wide range of target speeds and pump-load conditions. The accuracy and the response time of the controller can easily be tuned by adjusting a single tuning parameter. The switching frequency of the controller can also easily be tuned by adjusting the over-and undershoot thresholds independently from the accuracy of the speed-tracking control.     

Advanced hybrid energy storage system for mild hybrid electric vehicles

Hybrid electric vehicles (HEV) utilize electric power and a mechanical engine for propulsion; therefore, the performance of HEVs is directly influenced by the characteristics of the energy storage system (ESS). The ESS for an HEV generally requires high power performance, long cycle life, reliability and cost effectiveness; thus, a hybrid energy storage system (HESS) that combines different types of storage devices has been considered to fulfill both performance and cost requirements. To improve the operating efficiency and cycle life of a HESS, an advanced dynamic control regime in which pertinent storage devices in the HESS can be selectively operated based on their status is presented. Verification tests were performed to confirm the degree of improvement in energy efficiency. In this paper, an advanced HESS with a battery management system (BMS) that includes an optimal switching control function based on the estimated state of charge (SOC) is presented and verified.     

On-road assessment of in-vehicle driving workload for older drivers: Design guidelines for intelligent vehicles

There has been recent interest in intelligent vehicle technologies, such as advanced driver assistance systems (ADASs) or in-vehicle information systems (IVISs), that offer a significant enhancement of safety and convenience to drivers and passengers. However, the use of ADAS- and IVIS-based information devices may increase driver distraction and workload, which in turn can increase the chance of traffic accidents. The number of traffic accidents involving older drivers that are due to distraction, misjudgment, and delayed detection of danger, all of which are related to the drivers’ declining physical and cognitive capabilities, has increased. Because the death rate in traffic accidents is higher when older drivers are involved, finding ways to reduce the distraction and workload of older drivers is important. This paper generalizes driver information device operations and assesses the workload while driving by means of experiments involving 40 drivers in real cars under actual road conditions. Five driving tasks (manual only, manual primarily, visual only, visual primarily, and visual-manual) and three age groups (younger (20–29 years of age), middle-aged (40–49 years of age), and older (60–69 years of age)) were considered in investigating the effect of age-related workload difference. Data were collected from 40 drivers who drove in a real car under actual road conditions. The experimental results showed that age influences driver workload while performing in-vehicle tasks.     

Development of a fiber-reinforced plastic armrest frame for weight-reduced automobiles

This paper presents the design optimization process of a short fiber-reinforced plastic armrest frame to minimize its weight by replacing the steel frame with a plastic frame. The analysis was carried out with the equivalent mechanical model and design of experiment (DOE) method. Instead of considering the whole structure, it is divided into three simpler regions to reduce the complexity of the problem through examining its structural characteristics and load conditions. The maximum stress and deflection of the regions that carry the normal load are calculated by the analytical mathematical form derived from an equivalent model. The other regions loaded by contact stress are handled by FEM (finite element method), the DOE method, and the RSM (response surface model). To optimize the design variables in both cases, the object functions derived from these calculations are solved with a CAE (computer aided engineering) tool. This method clearly shows the mechanical and mathematical representation of structural optimization and reduces the computing costs. After design optimization, the weight of the optimum plastic-based armrest frame is reduced by about 18% compared to the initial design of a plastic frame and is decreased by 50% in comparison with the steel frame. Some prototypical armrest frames were also made by injection molding and tested. The research results fulfilled all of the design requirements.     

Automobile defrosting system analysis through a full-scale model

Adequate visibility through the automobile windshield is of paramount practical significance, most often at very low temperatures when ice tends to form on the windshield screen. But the numerical simulation of the defrost process is a challenging task because phase change is involved. In this study numerical solution was computed by a finite volume computational fluid dynamics (CFD) program and experimental investigations were performed to validate the numerical results. It was found that the airflow produced by the defrost nozzle is highly nonuniform in nature and does not cover the whole windshield area. The nonuniformity also severely affected the heating temperature pattern on the windshield. The windshield temperature reached a maximum in the vicinity of the defroster nozzle in the lower part of the windshield and ranged from 9∼31°C over a period of 30 min, which caused the frost to melt on the windshield. The melting time was under 10 minutes, which satisfied the NHTSA standard. The numerical predictions were in close agreement with the experimental results. Thus, CFD can be a very useful design tool for an automobile HVAC system.