Hierarchical modeling of semi-active control of a full motorcycle suspension with six degrees of freedoms

Hierarchical control is a new control framework in the vehicle vibration control field. In this paper, a hierarchical modeling method is presented to form a different motorcycle model, compared to the traditional model with six degrees of freedoms (DOF), so as to construct hierarchical modeling control. The whole control framework is composed of a central control, two local controls and two uncontrollable parts. The front and rear wheel systems of a motorcycle are all dealt with by using two independent local 2-DOF systems. The driver and engine act as uncontrollable passive parts. The central control is composed of an algorithm made up of some dynamic equations that harmonize local relations. The vertical and pitch accelerations of the suspension center are treated as central control objects. With the help of Linear Quadratic Gaussian (LQG) algorithms adopted by two local controls, respectively, and Matlab software, some results of the simulation show that hierarchical modeling control requires less CPU time, reduces respond time and improves ride quality.     

Effect of the number of fuel injector holes on characteristics of combustion and emissions in a diesel engine

The diesel combustion process is highly dependent on fuel injection parameters, and understanding fuel spray development is essential for proper control of the process. One of the critical factors for controlling the rate of mixing of fuel and air is the number of injector holes in a diesel engine. This study was intended to explore the behavior of the formation of spray mixtures, combustion, and emissions as a function of the number of injector hole changes; from this work, we propose an optimal number of holes for superior emissions and engine performance in diesel engine applications. The results show that increasing the number of holes significantly influences evaporation, atomization, and combustion. However, when the number of holes exceeds a certain threshold, there is an adverse effect on combustion and emissions due to a lack of the air entrainment required for the achievement of a stoichiometric mixture.     

Optimum distribution of yaw moment for unified chassis control with limitations on the active front steering angle

This paper describes an optimum distribution method for yaw moment for use with unified chassis control (UCC) with limitations on the active front steering (AFS) angle. Although the UCC has been assumed to have no AFS angle limitation in the literature, a physical limitation exists in real applications. To improve upon the previous method, a new optimum distribution method for yaw moment is proposed that takes this limitation into account. This method derives an optimum longitudinal/lateral force using the Karush-Kuhn-Tucker (KKT) optimality condition, and a simulation is performed to validate the proposed method. The simulation results indicate that the limitation on the AFS angle increases longitudinal braking force and, therefore, reduces the vehicle speed and the side-slip angle.     

Active coolant control strategies in automotive engines

The coolant flow rate in conventional cooling systems in automotive engines is subject to the mechanical water pump speed, and high efficiency in terms of fuel economy and exhaust emission is not possible given this limitation. A new technology must be developed for engine cooling systems. The electronic water pump is used as a substitute for the mechanical water pump in new engine cooling systems. The new cooling system provides more flexible control of the coolant flow rate and engine temperature, which previously relied strongly on engine driving conditions such as load and speed. In this study, the feasibility of two new cooling strategies was investigated using a simulation model that was validated with temperatures measured in a diesel engine. Results revealed that active coolant control using an electronic water pump and valves substantially contributed to a reduction of coolant warm-up time during cold engine starts. Harmful emissions and fuel consumption are expected to decrease as a result of a reduction in warm-up time.     

Robust control for 4WS vehicles considering a varying tire-road friction coefficient

A µ-synthesis for four-wheel steering (4WS) problems is proposed. Applying this method, model uncertainties can be taken into consideration, and a µ-synthesis robust controller is designed with optimized weighting functions to attenuate the external disturbances. In addition, an optimal controller is designed using the well-known optimal control theory. Two different versions of control laws are considered here. In evaluations of vehicle performance with the robust controller, the proposed controller performs adequately with different maneuvers (i.e., J-turn and Fishhook) and on different road conditions (i.e., icy, wet, and dry). The numerical simulation shows that the designed µ-synthesis robust controller can improve the performance of a closed-loop 4WS vehicle, and this controller has good maneuverability, sufficiently robust stability, and good performance robustness against serious disturbances.     

Traffic-balancing algorithm for can systems with dual communication channels to enhance the network capacity

The controller area network (CAN) is the dominant protocol for in-vehicle network (IVN) systems because it provides bounded transmission delay among electronic control units (ECUs) at data rates between 100 Kbps and 1 Mbps. Many automotive companies have chosen the CAN protocol for their chassis network system of intelligent vehicles. However, the increasing number of ECUs in intelligent vehicles and the need for more intelligent functions require a network system with more network capacity and real-time capability. As one approach to enhance the network capacity of a CAN system, this paper introduces a CAN system with dual communication channels. This paper also presents a traffic-balancing algorithm that predicts the traffic of each channel and allocates frames to the most appropriate channel. An experimental testbed using commercial off-the-shelf microcontrollers with two CAN controllers was used to demonstrate the feasibility of the traffic-balancing algorithm.     

Development of the Sungkyunkwan University Driving Simulator (SKUD) for Human-Machine Interface studies of Car Navigation Systems

Driving simulators are useful tools that can be used not only to test the components of future cars, but also to evaluate the telematics service and HMI (Human-Machine Interface). However, driving simulators that are currently available cannot be implemented to test and evaluate a real commercial telematics service system because the GPS (Global Positioning System), which contains basic functional support for the telematics module, does not work in the VR (virtual reality) environment. A driving simulator, together with the GPS simulator, can be used to study the HMI to evaluate commercial CNS (Car Navigation Systems). In this paper, Sungkyunkwan University Driving Simulator (SKUD) is developed with a GPS simulator that is able to emulate GPS satellite signals and includes the NMEA-0183 protocol and RS232C communication standards. Furthermore, using the SKUD, the HMI of the real commercial CNS could be investigated with driver workload assessment methods.     

License plate location method unaffected by variation in size and aspect ratio

License plate location is a challenging task that is necessary for automatic vehicle identification. This paper presents a new method for locating a license plate when its size and aspect ratio are highly variable. The proposed method begins with an assumption that a license plate exists in a region where dense edges are located. We define an edge region as an area containing rich edges. The edge regions are created by dilating vertical edges, and they are classified into one of four types: left fragment type, right fragment type, whole type, and undefined type. The candidates for a license plate region are constructed by merging edge regions. Knowing what type of edge region is being examined is useful in the merging process. Finally, we verify whether each candidate contains a license plate or not by using the character arrangement information. The arrangement pattern is determined by the size of connected components and by the vertical overlap or horizontal distance between two neighboring components. Experimental results show that the proposed method gives robust results regardless of any variation in the size and aspect ratio of license plates.     

基于双群进化策略的多项式近似因式分解

针对传统算法在解决多项式的因式分解过程中,存在着只适用于精确分解而不适合系数为浮点数的多项式的因式分解问题,文中提出一种应用双种群双突变进化策略来对浮点数多项式近似分解的算法,克服了传统算法不能解决浮点数多项式的因式分解的弊端.数值计算结果表明该算法收敛速度快、精度高、稳定性强.     

Type synthesis of function-generating mechanisms for seat suspensions

Mechanisms with “negative” stiffness are a unique tool used to significantly improve vibration isolation for a vehicle driver via upgrade of the seat suspension. However, connection of such mechanisms to the suspension results in errors in the function generation process, and in most cases, makes motion impossible. An approach to type synthesis is presented in order to make this process more predictable, easy and thus more practical for the upgrade process. Structural classification of the suspensions is presented, and -an atlas of function-generating mechanisms for suspensions that reveals the effect of “negative” stiffness is completed. All of the function-generating mechanisms appear in the atlas as result of enumeration. Structural properties of novel and existing mechanisms are compared. Finally, some advantages in practical use of novel suspensions with “negative” stiffness are illustrated.