Application of rack type motor driven power steering control system for heavy vehicles

The Electric Power Steering (EPS) or Motor Driven Power Steering (MDPS) mechanism proves to be a bright prospect among passenger vehicles ensuring better vehicle safety and fuel economy. The car manufacturers are focusing on the production of Rack type EPS system (REPS). This paper describes the development of concurrent simulation technique using TruckSim and control strategy for analysing RMDPS control system with a dynamic vehicle system. A full Truck vehicle model interacting with RMDPS control algorithm was concurrently simulated on a sinusoidal steering input. The dynamic responses of vehicle chassis and steering system resulting were evaluated and compared with proving ground experimental data. The comparisons show reasonable agreement on steering wheel torque, lateral acceleration and yaw rate. This concurrent simulation research leads the possibility of RMDPS performance evaluation of Truck and Semi-bonnet cars.     

Modelling and controlling of car-following behavior in real traffic flow using ARMAX identification and Model Predictive Control

Nowadays, car following models, as the most popular microscopic traffic flow modeling, are increasingly being used by transportation experts to evaluate new Intelligent Transportation System (ITS) and Advanced Driver Assistance Systems (ADAS) applications. The control of car following is essential due to its safety and its operational efficiency. For this purpose, this paper builds a model of car following behavior based on ARMAX structure from a real traffic data set and presents a Model Predictive Control (MPC) controller. An important advantage of this type of control is its ability to cope with constraints on controls. Since safety and operational efficiency are constraints for car following, therefore we have recruited this type of controller in this study to deal with these constraints. Based on the relative distance and relative acceleration of each instant, the MPC predicts the future behavior of the leader vehicle (LV) and according to this behavior, the acceleration of the follower vehicle (FV) is controlled. The MPC tries to control this acceleration in a way to keep the relative distance at a safe region. To investigate the performance of the designed controller, the result of the system is compared with the behavior of human drivers with similar initial conditions. Also, some other test performances were accomplished to investigate other features such as robustness and the stability of the designed MPC. The simulation results show that the MPC controller has a behavior much safer than that of real drivers and it can provide a pleasant trip for passengers.     

Effect of tumble-home on roof strength of a vehicle

This study reports on the effect of vehicle tumble-home (side body inclination) on roof strength. The steep inclination of the side body of a vehicle increases its roof strength. Comprehensive analysis of the impact of high roof strength driven by the steep inclination on dynamic roof strength in rollover is described. Here, we have developed a numerical model using the ADAMS, which is capable of characterizing both of the static and the dynamic roof strength. According to the FMVSS 216 protocol, we achieve the strength to weight ratio (SWR; static roof strength) by applying loading plates to the roof of a vehicle. The Controlled Rollover Impact System (CRIS) allows us to quantitatively characterize the displacements of the top end of A-pillar and B-pillar, thus determining the dynamic roof strength by comparing the results. We demonstrated that the roof intrusion was one of the most critical causes which lead to injuries of occupants fastening seat belts. Our analysis revealed that the increase of the side body inclination of vehicles enhanced the static roof strength whereas it could not reduce the roof displacement (intrusion) in the dynamic rollover.     

Loosening analysis for fastening screw of automotive door trim parts

While a screw is a fastening element that can tighten the two parts at low cost, the loosening of the screw is generated due to external forces such as repetitive load, vibration, and thermal stress. This phenomenon decreases the initial clamping force, and this can be a serious problem to the safety of the product. However, while fastening parts are handled through experiment and experience, there is a lack of research on the screw loosening of plastic fastening parts. For example, vehicles have various fastening parts. Among the fastening elements, screws are typically used for tightening parts of the vehicle door trim. Vehicle interior materials are mainly composed of plastic parts. Especially, the temperature of the vehicle interior changes from a sub-zero temperature to 100 degrees (°C) due to solar radiation. Unlike metals, plastic materials are commonly susceptible to the environment. In this study, the fastening screw of automotive door trim parts is selected. First, a screw loosening mechanism is implemented through Computer Aided Engineering (CAE) analysis and the influences of degradation are then analyzed. Secondly, the selecting method of clamping force is suggested through the analysis result of reduction according to the tightening torque.     

Automotive steering system preferences evaluated using a driving simulator

The automotive steering system is the primary channel through which road and vehicle behavior feedback is transmitted to the driver. While the driver provides directional platform control through the steering wheel, perceptions of the vehicle’s handling responsiveness are simultaneously transmitted back to the driver allowing for correction of any instabilities the vehicle may encounter. Based on these factors, drivers often pay special attention to the steering system when deciding what vehicle to purchase. Therefore, a significant amount of effort and time is invested in attempting to determine the optimal design of steering system components and configurations. In this study, the determination of an optimal steering configuration was attempted based on responses obtained from questionnaires that subjects answered. The questions were designed to evaluate the degree of satisfaction regarding the “control”, “ease of operation”, and “fun” participants experienced after each driving run. During the study, human subjects drove a driving simulator for 15 combinations of 3 different roadway environments and 5 different steering configurations, filling out a questionnaire after each scenario. The subjects were also classified as a type of driver (“utility”, “enthusiast”, and/or “performance”). The study attempted to determine if the mean values of questionnaire responses for “control”, “ease”, and “fun” type of questions changed as the scenario and/or driver type changed. Analysis of Variance (ANOVA) was used to determine if the mean values of the three types of questions were statistically different. The overall results suggest that the average responses for vehicle “control”, “ease”, and the “fun” type of questions were dependent on the type of roadway environment; however, only the responses for “fun” type of questions were influenced by the given steering configurations. Indeed, the steering system can impact the driver’s perceptions of the vehicle’s operational experience.     

Comparative study between Korea and UK: relationship between driving style and real-world fuel consumption

It is known that differences in driving styles have a significant impact on fuel efficiency and driving styles are affected by various factors such as driver characteristics, street environment, traffic situation, vehicle performance, and weather conditions. However, existing knowledge about the relationship between driving style and fuel consumption is limited. Thus, the aim of this study was to analyze the relationship beteen driving style and fuel consumption. The analysis presented in this paper used data from three on-road experiments were conducted independently in two different countries, i.e. South Korea and the United Kingdom. In this study, 91 participants, consisting 44 UK drivers and 47 Korean drivers, were asked to drive approximately 28 km of UK road and 21 km of Korean road, respectively. Driving data, including real-time fuel consumption, vehicle speed, and acceleration pedal usage were collected. The results suggested that driving styles including average vehicle speed and average throttle position were highly correlated with the real-world fuel consumption, and the cultural factors, e.g. road environment, traffic design, and driver’s characteristics affected the driving styles and, consequently, fuel efficiency.     

Hydrodynamics study of a BCF mode bioinspired robotic-fish underwater vehicle using Lighthill’s slender body model

This paper investigates the hydrodynamic characteristics of the rectilinear motion of a robotic fish underwater vehicle. This 2-joint, 3-link multibody vehicle model is biologically inspired by a body caudal fin carangiform fish propulsion mechanism. Navier–Stokes equations are used to compute the unsteady flow fields generated due to the interaction between the vehicle and the surrounding incompressible and Newtonian fluid (water) environment. The NACA 0014 airfoil aerodynamic profile has been designed to boost the swimming efficiency by reducing drag as the vehicle undergoes an undulatory/oscillatory motion. Using the Lighthill slender body model, a traveling wave mathematical function is defined to undulate the robotic fish posterior (caudal) region while the motion tracking is carried out by dynamic meshing technique. The results obtained show that though the net lift force approaches to zero, the net thrust or negative drag coefficient maintains a finite value dependent on kinematic parameters like tail beat frequency (TBF) and amplitude span (AS) at a given propulsive wavelength and the forward velocity of the vehicle. The results reveal the effects of TBF and AS on the coefficient of drag friction and the thrust force. Drag coefficients obtained from the simulations are compared and validated with the experimental results. The hydrodynamic results are found to be similar to the kinematic study results and suggest that TBF and AS play the most effective roles in the bioinspired propulsion technique. Relation of these parameters with propelling thrust force and forward velocity is also in conjunction over a given range of TBF and AS values.     

Hydrodynamic performance of multiple-row slotted breakwaters

This study examines the hydrodynamic performance of multiple-row vertical slotted breakwaters. We developed a mathematical model based on an eigenfunction expansion method and a least squares technique for Stokes second-order waves. The numerical results obtained for limiting cases of double-row and triple-row walls are in good agreement with results of previous studies and experimental results. Comparisons with experimental measurements of the reflection, transmission, and dissipation coefficients (C _R , C _T , and C _E ) for double-row walls show that the proposed mathematical model adequately reproduces most of the important features. We found that for double-row walls, the C _R increases with increasing wave number, kd, and with a decreasing permeable wall part, dm. The C _T follows the opposite trend. The C _E slowly increases with an increasing kd for lower kd values, reaches a maximum, and then decreases again. In addition, an increasing porosity of dm would significantly decrease the C _R , while increasing the C _T . At lower values of kd, a decreasing porosity increases the C _E , but for high values of kd, a decreasing porosity reduces the C _E . The numerical results indicate that, for triple-row walls, the effect of the arrangement of the chamber widths on hydrodynamic characteristics is not significant, except when kd<0.5. Double-row slotted breakwaters may exhibit a good wave-absorbing performance at kd>0.5, where by the horizontal wave force may be smaller than that of a single wall. On the other hand, the difference between double-row and triple-row vertical slotted breakwaters is marginal.     

Panama Canal expansion: fuel economy and logistical risk

Since cargo capacity increases faster than fuel consumption, the significantly larger capacity fleets which will accompany expansion of the Panama Canal will introduce additional fuel economies and cost savings. Enabling larger, more fuel-efficient vessels to carry cargo the entire distance from Asia to US east-coast ports allows vessel operators to realize significant and meaningful savings compared with the alternatives of using smaller Panamax vessels for the whole distance, or sending the cargo over the US land bridge by train or truck. Fuel savings are quantified along with the monetary savings based on various assumptions for the price of fuel. These savings are dramatic and will increase directly with the price of crude petroleum. Finally, microeconomic theory is deployed to determine how cost savings will be distributed between shipping customers and vessel operators.     

Effect of pH on mechanical,physical and tribological properties of electroless Ni-P-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite deposits for marine applications

Successful co-deposition of fine particulate matter within an Electroless Nickel-Phosphorous (ENi-P) matrix is dependent on various factors like bath composition, particle compatibility with metallic matrix, bath reactivity (pH), particle size and their distribution. ENi-P deposits incorporating Al₂O₃/Alumina in a disperse phase have varied effects on properties and attributes like surface roughness (Ra), microhardness, wear resistance, corrosion resistance and surface morphology of the deposits obtained. This paper experimentally investigates the effect of alumina (1.55 g/L) on Ra, microhardness, surface morphology, deposition rate, wettability, wear resistance and corrosion resistance of ENi-P-Al₂O₃ composite deposits on mild steel substrates at bath pH 5, 7 and 9. Study reveals that optimum deposit parameters and deposition rates are achieved with bath pH. However, not much study has been undertaken concerning composite deposits obtained from higher bath pH or basic bath. This is attributable to the fact that at higher bath pH or alkaline baths, the bath gets unstable and eventually degrades or decomposes, thereby resulting in sub optimal or poor deposition. Hence, experimental investigations carried out by preparing suitable baths, operating under optimum conditions, and enabling successful composite deposition in acidic and alkaline baths have revealed that there is a significant improvement in the above mentioned properties of the as-deposited composite deposits, as the pH is increased from pH 5 to pH 9. This aspect can therefore be advantageously utilized for preparing various marine components like fasteners, nuts, bolts, washers, pipes, cables, components having relative motion etc.