Requirement-based testing of an automotive ECU considering the behavior of the vehicle

HILS (Hardware In the Loop Simulation) and RBT (Requirement-Based Testing) are widely used to evaluate the performance and reliability of automotive ECUs (Electronic Control Units). The HILS method is used to predict the behavior of ECU-installed vehicles and to evaluate the performance of ECU controllers. RBT evaluates whether the embedded system satisfies the pre-defined requirements. In this study, the behavior of a vehicle is regarded as a system requirement, and an embedded system test procedure that evaluates the system requirement is proposed. In particular, a new method is introduced, which integrates HILS with RBT. Using the proposed method, the behavior of an articulated vehicle equipped with an AWS (All Wheel Steering) ECU is evaluated with RBT software.     

Drive control system design for stability and maneuverability of a 6WD/6WS vehicle

This paper describes a drive controller designed to improve the lateral vehicle stability and maneuverability of a 6-wheel drive / 6-wheel steering (6WD/6WS) vehicle. The drive controller consists of upper and lower level controllers. The upper level controller is based on sliding control theory and determines both front and middle steering angle, additional net yaw moment, and longitudinal net force according to the reference velocity and steering angle of a manual drive, remotely controlled, autonomous controller. The lower level controller takes the desired longitudinal net force, yaw moment, and tire force information as inputs and determines the additional front steering angle and distributed longitudinal tire force on each wheel. This controller is based on optimal distribution control and takes into consideration the friction circle related to the vertical tire force and friction coefficient acting on the road and tire. Distributed longitudinal/lateral tire forces are determined as proportion to the size of the friction circle according to changes in driving conditions. The response of the 6WD/6WS vehicle implemented with this drive controller has been evaluated via computer simulations conducted using the Matlab/Simulink dynamic model. Computer simulations of an open loop under turning conditions and a closed-loop driver model subjected to double lane change have been conducted to demonstrate the improved performance of the proposed drive controller over that of a conventional DYC.     

Torque control of engine clutch to improve the driving quality of hybrid electric vehicles

As a powertrain for hybrid electric vehicles (HEVs), the automatic transmission (AT) is not only convenient for the driver but also reduces hybridization costs because the existing production line is used to produce the AT. However, it has low fuel economy due to the torque converter. To overcome this disadvantage, this paper studies HEVs equipped an AT without a torque converter. In this case, additional torque control is needed to prevent the driving quality from deteriorating. This paper suggests three different torque control methods and develops a simulator for an HEV that can simulate the dynamic behaviors of the HEV when the engine clutch is engaged. The HEV drive train is modeled with AMESim, and a controller model is developed with MATLAB/Simulink. A co-simulation environment is established. By using the developed HEV simulator, simulations are conducted to analyze the dynamic behaviors of the HEV according to the control methods.     

Influential factors for HLA pump up in a roller finger follower engine

In an HLA (hydraulic lash adjuster) piston engine, “pump up” can occur when a valve is opened by the HLA when it should be closed. HLA pump up is more frequently encountered with exhaust valves than with intake valves. When HLA pump up in occurs in the exhaust valve, exhaust gas from the exhaust manifold enters the cylinder on the intake stroke, and fresh air-fuel mixture exits through the exhaust manifold on the compression stroke and is burned in the catalyst, causing partial burning, misfire, catalyst melting and power drop. HLA pump up occurs when the force on the valve from the HLA is higher than the force on the HLA from the valve. HLA pump up is related to design parameters, such as oil pressure, rocker ratio, spring load, spring surge, and both intake and exhaust valve timing. In this study, valve lift and load on a roller finger follower were measured at varying engine firing conditions to evaluate HLA pump up. The results indicated that effective measures to reduce HLA pump up include a higher rocker ratio, a lower oil supply pressure to the HLA, a higher spring installation load and a lower spring surge.     

Numerical and experimental investigation of lubricating oil flow in a gerotor pump

Gerotor pumps are widely used in the automotive industry for engine oil lubrication, due to their high volumetric efficiency and smooth pumping action. In many cases, the lubricating oil from the sump is mixed with contaminants, such as dust and tiny solid particles, or becomes thickened, due to aging. These problems will lead to critical situations, such as increased noise, enhanced wear and erosion, and poor lubrication of the engine. These critical situations were studied by conducting a detailed CFD integrated investigation on a gerotor pump’s performance at different operating conditions in three phases, and the results are presented in this paper. In first phase, a CFD model of a gerotor pump was developed with a dynamic mesh for the rotary movement of both the inner and outer rotors. The effects on pump flow rate of important parameters, such as rotor speed, fluid viscosity and number of ports, were simulated using non-contaminated oil at room temperature and an elevated temperature of 140oC. The relationship between flow rate and pressure at different rotor speeds was predicted and validated with test data for further parametric study. The pressure ripples at different time steps were measured at different angular positions of the rotors to examine the model accuracy. It was found that the flow rate increased and pressure pulsation, as well as flow recirculation, was reduced when ports were added to the cover plate. A suction pipe with a strainer was added for the second phase to capture the undesired changes in flow behavior, such as cavitation, which is caused by negative suction at the inlet region of pump. A suitable size for the inlet suction pipe for this pump was chosen after performing tests to characterize the flow behavior with single and double ports. Next, the relationship between pressure drop and strainer porosity was determined using different porosity values for the strainers. In the final phase, oil with different concentrations of solids was simulated to measure the effect of solid particles on flow rates and pressure losses. It was observed that the intensity of the recirculation was reduced at the suction end at the higher concentration of 0.04%, due to particle inertial effects. It was also found that particle size distribution affected the overall efficiency and pressure head of the pump.     

Breakup modeling of a liquid jet in cross flow

We propose a novel breakup model to simulate the catastrophic breakup regime in a supersonic cross flow. A developed model has been extended from an existing Kelvin-Helmholtz/Rayleigh-Taylor (K-H/R-T) hybrid model. A new mass reduction rate equation, which has critical effects on overall spray structure, is successfully adopted, and the breakup length, which is an important parameter in existing model, is replaced by the breakup initiation time. Measured data from the supersonic wind tunnel with a dimension of 762×152×127 mm was employed to validate the newly developed breakup model. A nonaerated injector with an orifice diameter of 0.5 mm is used to inject water into a supersonic flow prescribed by the momentum flux ratio of the liquid jet to free stream air, q ₀ . The conservation-element and solution-element (CE/SE) method, a novel numerical framework for the general conservation law, is applied to simulate the supersonic compressible flow. The spray penetration height and average droplet size along with a spray penetration axis are quantitatively compared with data. The shock train flow structures induced by the presence of a liquid jet are further discussed.     

Sharing piping CAD models of ocean plants based on international standards

In the shipbuilding industry, different computer-aided design (CAD) systems are used for different design domains, structure, and outfitting. We need to exchange data among different CAD systems such as Tribon, AutoCAD, Intergraph or PDMS to complete the whole design and production process. There are two approaches to data exchange. One is direct translation; the other is indirect translation, which is based on a neutral format. If we use a neutral format, the data specification is open to the public and the design model can be used by other CAD systems, including next-generation CAD systems. In this paper, we propose an indirect method that uses ISO 10303 (STandard for the Exchange of Product model data) AP227 and ISO 15926 to define neutral formats. A separate ShapeDB is constructed to manage the geometry information, referenced to the catalogue data defined by ISO 15926. An experimental implementation for data exchange between Tribon and PDMS is described.     

U.S. import/export container flow modeling and disruption analysis

International containerized freight movement is a vital part of the supply chain for many companies, and a critical element of moving consumer goods to points of retail sale within the U.S. Containerized imports also present a clear security concern (e.g., terrorists attempting to ship “dirty bombs,” chemical, biological or even nuclear weapons, into the U.S. in a shipping container). The goal of the research presented here is to create a modeling tool for analyzing flows of U.S. imports and exports of containerized freight, and the potential changes in those flows under a variety of conditions (e.g., port disruptions, extensive security-related delays, etc.). Our focus is on movements through maritime container ports, and not overland movements between the U.S. and Canada or Mexico.The network model, referred to as the System for Import/Export Routing and Recovery Analysis (SIERRA), represents container movements between the U.S. and 46 other countries that account for the vast majority of U.S. imports and exports. The SIERRA model is a network equilibrium model that predicts flows between foreign countries and North American ports, the total volumes handled (import and export) by each port, the modal volumes (truck and rail) moving domestically into and out of each port, and volumes between each port and a set of transportation analysis zones within the U.S.     

Bus arrival time prediction at bus stop with multiple routes

Provision of accurate bus arrival information is vital to passengers for reducing their anxieties and waiting times at bus stop. This paper proposes models to predict bus arrival times at the same bus stop but with different routes. In the proposed models, bus running times of multiple routes are used for predicting the bus arrival time of each of these bus routes. Several methods, which include support vector machine (SVM), artificial neural network (ANN), k nearest neighbours algorithm (k-NN) and linear regression (LR), are adopted for the bus arrival time prediction. Observation surveys are conducted to collect bus running and arrival time data for validation of the proposed models. The results show that the proposed models are more accurate than the models based on the bus running times of single route. Moreover, it is found that the SVM model performs the best among the four proposed models for predicting the bus arrival times at bus stop with multiple routes.     

The implications of the re-establishment of direct links across the Taiwan Strait on the aviation industries in Greater China

This paper investigates the economic implications of the liberalization of air transportation across the Taiwan Strait to the region's aviation industries. Our analysis suggests that (1) liberalization has brought substantial benefits to airports and airlines in Mainland China and Taiwan. Negative impacts to Hong Kong are largely compensated by traffic increase in routes linking Mainland China. (2) In general, Taiwanese airports and airlines have benefited more from liberalization compared to airports and airlines on the mainland and Hong Kong. Such asymmetric effect is due to the larger size of the Mainland Chinese aviation market, which allows Taiwanese airlines to exploit network-related benefits. (3) Our investigation suggests that foreign hub carriers and medium sized Chinese airports will benefit most from China's future liberalizations.