Model-based control system design in a urea-SCR aftertreatment system based on NH3 sensor feedback

This paper presents preliminary control system simulation results in a urea-selective catalytic reduction (SCR) aftertreatment system based on NH₃ sensor feedback. A four-state control-oriented lumped parameter model is used to analyze the controllability and observability properties of the urea-SCR plant. A model-based estimator is designed via simulation and a control system is developed with design based on a sliding mode control framework. The control system based on NH₃ sensor feedback is analyzed via simulation by comparing it to a control system developed based on NO_x sensor feedback. Simulation results show that the NH₃ sensor-based strategy performs very similarly in comparison to a NO_x sensor-based strategy. The control system performance metrics for NO_x index, urea index, urea usage, and NH₃ slip suggest that the NO_x sensor can be a potential alternative to a NO_x sensor for urea-SCR control applications.     

A Study of the Response of a Double Bottom Vehicle to Steering and Braking

The paper describes the development, operation and some of the results obtained from a simulation of the steering behaviour of the double bottom articulated vehicle, in particular the effects that arise when certain axles are locked.     

Application of a modified thermostatic control strategy to parallel mild HEV for improving fuel economy in urban driving conditions

A modified thermostatic control strategy is applied to the powertrain control of a parallel mild hybrid electric vehicle (HEV) to improve fuel economy. This strategy can improve the fuel economy of a parallel mild HEV by operating internal combustion engine (ICE) in a high-efficiency region. Thus, in this study, experiments of a parallel mild HEV were conducted to analyze the characteristics of the hybrid electric powertrain and a numerical model is developed for the vehicle. Based on the results, the thermostatic control strategy was modified and applied to the vehicle model. Also, battery protection logic by using electrochemical battery model is applied because the active usage of battery by thermostatic control strategy can damage the battery. The simulation results of the vehicle under urban driving conditions show that the thermostatic control strategy can improve the vehicle’s fuel economy by 3.7 % compared with that of the conventional strategy. The results also suggest that the trade-off between the fuel economy improvement by efficient ICE operation and the battery life reduction by active battery usage should be carefully investigated when a thermostatic control strategy is applied to a parallel mild HEV.     

Optimal scheduling of the flexray static segment based on two-dimensional bin-packing algorithm

FlexRay is a reliable and hard real-time in-vehicle communication protocol that is strongly promoted by car manufacturers as the de facto standard in the automotive domain. The protocol offers both a time-triggered and an eventtriggered architecture. This paper focuses on the optimal scheduling of the time-triggered component of FlexRay known as the static (ST) segment using a two-dimensional bin-packing technique. To maximize the bandwidth utilization in the ST segment, a fast heuristic as well as an efficient integer linear programming approach are proposed. Our methods directly schedule signals into slots including frame packing, according to signal-based data scheduling and the slot/ cycle multiplexing mechanisms presented by the latest version of the FlexRay protocol. The benefits of our proposed methods are demonstrated by extensive experiments on synthetic and an automotive X-by-wire system case study. An additional test case is examined to emphasize the superior performance of the proposed approach relative to that of existing optimal scheduling approaches.     

Theoretical method for predicting the weight reduction rate of a box-type car body for rolling stock by material substitution design

In this paper, a theoretical approach is suggested for predicting the structural performances and weight reduction rate of a car body with a box-type section when its material is substituted with a lightweight material for weight saving. For the material substitution design of a car body for rolling stock, bending, axial, and twisting deformations should be considered at constant stiffness and strength conditions. To compare the weight reduction effects on different material applications, some new indices were derived from a structural performance point of view. The derived indices provide good measures to estimate weight reduction by material substitution design and can be effectively applied to the conceptual design of a car body.     

Vehicle detection system design based on stereo vision sensors

Vehicle detection is a crucial issue for driver assistance system as well as for autonomous vehicle guidance function and it has to be performed with high reliability to avoid any potential collision. The vision-based vehicle detection systems are regarded promising for this purpose because they require little infrastructure on a highway. However, the feasibility of these systems in passenger car requires accurate and robust sensing performance. In this paper, a vehicle detection system using stereo vision sensors is developed. This system utilizes feature extraction, epipoplar constraint and feature matching in order to robustly detect the initial corresponding pairs. The proposed system can detect a leading vehicle in front and can estimate its position parameters such as the distance and heading angle. After the initial detection, the system executes the tracking algorithm for the vehicles in the lane. The proposed vehicle detection system is implemented on a passenger car and its performances are verified experimentally.     

Crash protection of Hybrid Electrical Vehicles for amending the KMVSS No. 91

This paper explores issues related to the electrical safety of Hybrid Electrical Vehicles (HEVs) during and after various crash events. Japanese and American federal regulations regarding occupant protection against high voltages in Electric Vehicles (EVs) and HEVs were surveyed and analyzed in this study. Front, side and rear impact tests for two types of HEVs were conducted to investigate electrolyte spillage, the retention of the propulsion battery system and the electrical isolation of the occupant. The test results met the related criteria. The test procedures and the criteria for occupant protection established through this study were amended to Korean Motor Vehicle Safety Standard (KMVSS) No. 91 to add the crash protection of the EVs and the HEVs.     

Prediction of the dimensional deformation of the addendum and dedendum after the warm shrink fitting process using a correction coefficient

The warm shrink fitting process is generally used to assemble automobile transmission parts (shafts/gears). However, this process causes a deformation in the addendum and dedendum of the gear depending on the fitting interference and gear profile, and this deformation causes additional noise and vibration between the gears. To address these problems, the warm shrink fitting process is analyzed by considering the error in the dimensional deformation of the addendum and dedendum found when comparing the results of a theoretical analysis and finite element analysis (FEA). A correction coefficient that reduces this error is derived through an analysis of the difference in the cross-sectional area between the shapes used for the theoretical analysis and that of the actual gear, and a closed-form equation to predict the dimensional deformation of the addendum and dedendum is proposed. The FEA method is proposed to analyze the thermal-structural-thermal coupled field analysis of the warm shrink fitting process (heating-fitting-cooling process). To verify the closed-form equation using the correction coefficient, measurements are made of actual helical gears used in automobile transmissions. The results are in good agreement with those given by the closed-form equation.     

Modified lateral control of an autonomous vehicle by look-ahead and look-down sensing

This paper presents a modified lateral control method for an autonomous vehicle with both look-ahead and look-down sensing systems. To cope with sensor noise and modeling uncertainty in the lateral control of the vehicle, a modified LMI-based H lateral controller was proposed, which uses the look-ahead information of the lateral offset error measured at the front of vehicle and the look-down information of the vehicle yaw angle error between the reference lane and the centerline of the vehicle. To verify the safety and the performance of the lateral control, a scaled-down vehicle was developed, and the positioning of the vehicle was estimated with USAT. The proposed controller, which uses both look-ahead and look-down information, was tested for lane changing and reference lane tracking with both simulation and experiment. The simulation and experimental results show that the proposed controller has better tracking and handling performance compared with a controller that uses only the look-ahead information of the target heading angle error.