Autonomous Lateral Control of Vehicles in an Automated Highway System

Lateral control of vehicles in IVHS requires the installation of on-board sensors as well as the installation of roadway hardware such as cables, magnets, etc. Existing control approaches in PATH require road curvature and vehicle lateral position (with respect to the center of the lane) information. Hence these approaches rely on roadway sensors to obtain relative lateral position. These methods will necessitate infrastructural changes to the highway.

This paper introduces the concept of autonomous lateral control or auto-tracking. The method allows us to use only line-of-sight sensor information to effect vehicle control. We present a detailed vehicle model. Controllers have been proposed to demonstrate the effectiveness of the proposed auto-tracking scheme. We also examine the possibilities of using this method for lane change purposes in an automated highway system.     

Baroclinic eddy formation in a Rhine plume model

A three-dimensional finite difference tidal model, including advective and diffusive transport of salinity, is used in the two-layer model for simulation of Rhine water outflow. Layer depths are adjusted in a way that no advective transports between upper and lower layer take place in case of sufficiently stable stratification.Model results show frontal eddy development related to (limited) growing internal waves in case of weak northeasterly to southeasterly winds. It is shown that baroclinically unstable conditions occur, related to vertical velocity shear, resulting in frontal meanders with wave lengths between 18 and 30 km. Satellite images of sea surface temperature show a comparable behaviour of the temperature front, which is strongly correlated with the salinity front of the Rhine plume.     

海洋浮体非线性水弹性力学分析--结构非线性的初步考虑

前文^[1-3]分别介绍了二阶非线性水弹性分析中流体非线性的理论与部分典型算例结果。本文则在流体线性假定的前提下，介绍结构非线性的考虑方法。以大变形浮动平板在多向规则波中的运动与变形响应为例，介绍了板垂向位移与流体相互耦合的频域分析方法。讨论了板内薄膜力对结构变形与受力的影响。数值算例表明，薄膜力对变形、弯矩和应力都有一定程度的非线性贡献，在某些情况下是不可忽略的。     

High speed driving stability of passenger car under crosswind effects

The driving stability of a passenger car at high-speed and under crosswind conditions is affected by aerodynamic characteristics as well as their dynamic characteristics, suspension, and weight distribution. In this study, the total measuring system was thought up to understand the transient vehicle dynamics and aerodynamics with driver’s control inputs all together. The test results were taken from a full-scale wind tunnel test, a crosswind generator test and an on-road test. We investigated major aerodynamic parameters that affect the driving stability of passenger cars under crosswind effects such as overtaking, passing each other, natural crosswind, etc. The reaction rate of high-speed stability will be improved when we minimize the total lift, side force and especially the yawing moment.     

Parallel model based fault detection algorithm for electronic parking brake system

This paper describes a parallel model-based fault detection algorithm for an electronic parking brake (EPB) system, which consists of an electronic control unit with built-in current sensor and braking force sensor. For the EPB system to supply sufficient parking force to a vehicle, the parking force sensor is of utmost importance. If a fault occurs in this sensor, sufficient parking force may not be supplied, thereby seriously threatening the safety of the vehicle. Thus, a fault detection method is required for the parking force sensor of the EPB system to improve the safety of vehicles. For this purpose, a highly reliable fault detection method is needed to detect abnormal fault signals, which cannot be detected by the existing on-line sensor monitoring fault detection methods. This paper proposes a novel parallel model-based fault detection algorithm for the EPB system, which compares the physical sensor data with the mathematical model, the fuzzy model, and the neural network model at the same time. In order to reduce false alarms, the magnitude of thresholds and the operation counts are changed adaptively. When the proposed parallel model-based fault detection algorithm detects severe failures of the force sensor, it warns the driver in advance to prevent accidents due to the failures. The proposed algorithm is verified by hardware-in-theloop simulations in various situations.     

Generalized magnetorheological (MR) damper model and its application in semi-active control of vehicle suspension system

In this paper, analytical characterization of the magneto-rheological (MR) damper is done using a new modified algebraic model. Algebraic model is also more preferable because of its low computational expenses compared to differential Bouc-Wen’s model which is highly computationally demanding. This model along with the obtained model parameters is used as a semi-active suspension device in a quarter car model and the stationary response of the vehicle traversing on a rough road is obtained. The control part consists of two nested controllers. One of them is the system controller which generates the desired damping force and the other is the damper controller which adjusts the voltage level to MR damper so as to track the desired damping force. For the system controller a model reference skyhook Sliding Mode Controller (SMC) is used and for the damper controller a continuous state algorithm is built to determine the input voltage so as to gain the desired damping force. The analytical model is subsequently used in the quarter car vehicle model and the vehicular responses are studied. A simulation study is performed to prove the effectiveness and robustness of the semi-active control approach. Results show that the semi-active controller can achieve compatible performance as that of active suspension controller except for a little deterioration.     

Innovative design optimization strategy for the automotive industry

In order to effectively solve modern automotive design problems including the results of nonlinear FEA and multi-body dynamics, a progressive meta-model based design optimization is presented. To reduce the number of initial sample points, two sampling methods are introduced. Then, for efficient and stable construction of meta-models, three metamodel methods are newly introduced which are numerically based on the singular value decomposition technique. To design a practical system considering manufacturing tolerances and optimizing multiple performances, a robust design optimization, 6-sigma constraints and multi-objective strategies are implemented when solving the approximate optimization problem constructed from the meta-models. Until the convergence criteria are satisfied, the initially developed meta-models are progressively improved by adding only one point that minimizes the approximate Lagrangian in the consecutive optimization iterations. Finally, one validation sample and four automotive applications are solved to show the effectiveness of the proposed approach.     

Co-operative control for regenerative braking and friction braking to increase energy recovery without wheel lock

This paper presents a regenerative braking co-operative control algorithm to increase energy recovery without wheel lock. Considering the magnitude of the braking force available between the tire and road surface, the control algorithm was designed for the regenerative braking force at the front wheel and friction braking force at the rear wheel to be increased following the friction coefficient line. The performance of the proposed regenerative braking co-operative control algorithm was evaluated by the hardware in the loop simulation (HILS) with an electronic wedge brake on its front wheels and an electronic mechanical brake on its rear wheels. The HILS results showed that a proper braking force on the front and rear wheels on a low μ road prevented the lock of the front wheels that was connected to the motor, and maintained the regenerative braking and increased energy recovery.     

Cooperative regenerative braking control for front-wheel-drive hybrid electric vehicle based on adaptive regenerative brake torque optimization using under-steer index

In this study, cooperative regenerative braking control of front-wheel-drive hybrid electric vehicle is proposed to recover optimal braking energy while guaranteeing the vehicle lateral stability. In front-wheel-drive hybrid electric vehicle, excessive regenerative braking for recuperation of the maximum braking energy can cause under-steer problem. This is due to the fact that the resultant lateral force on front tire saturates and starts to decrease. Therefore, cost function with constraints is newly defined to determine optimum distribution of brake torques including the regenerative brake torque for improving the braking energy recovery as well as the vehicle lateral stability. This cost function includes trade-off relation of two objectives. The physical meaning of first objective of cost function is to maximize the regenerative brake torque for improving the fuel economy and that of second objective is to increase the mechanical-friction brake torques at rear wheels rather than regenerative brake torque at front wheels for preventing front tire saturation. And weighting factor in cost function is also proposed as a function of under-steer index representing current state of the vehicle lateral motion in order to generalize the constrained optimization problem including both normal and severe cornering situation. For example, as the vehicle approaches its handling limits, adaptation of weighting factor is possible to prioritize front tire saturation over increasing the recuperation of braking energy for driver safety and vehicle lateral stability. Finally, computer simulation of closed loop driver-vehicle system based on Carsim? performed to verify the effectiveness of adaptation method in proposed controller and the vehicle performance of the proposed controller in comparison with the conventional controller for only considering the vehicle lateral stability. Simulation results indicate that the proposed controller improved the performance of braking energy recovery as well as guaranteed the vehicle lateral stability similar to the conventional controller.     

Automatic parking of vehicles: A review of literatures

Collision accidents often occur during parking or reversing cars. In allusion to this point, this paper conducts a review of literatures on automatic parking. To begin with, a brief introduction of automatic parking including its background and significance is given. Then its commercial application, research status and latest progress are summarized which include visual perception, ultrasonic sensors and radar technology, path planning, control algorithms based on fuzzy theory, neural network, image processing and recognition technology, and digital signal processing technology, etc. On further analysis, some reasonable conclusions are drawn and the future work is suggested.