Takehiko Fujioka

Measuring rail/wheel contact points of running railway vehicles

Abstract It has been difficult to detect lateral contact point of rail and wheel, though technology of instrumented wheelset has advanced in the last 20 years. Therefore, it is interesting and worth while to study on method of measuring rail/wheel contact point and contact force of running railway vehicles, since many things in real rail/wheel contact phenomenon are still unknown. Recently, we have tried to develop a method of measuring rail/wheel contact point by improving conventional method of measuring wheel load and lateral force in which strain of the disk surface is used for measuring these forces. Firstly surface strain on disk type wheel is analyzed by an FEM program, NASTRAN, under the condition that vertical, lateral, or longitudinal force separately acts on various points along the wheel profile. By the calculated result, it shows possibility of detecting the rail/wheel contact point by means of measuring lateral distribution of compress strain which changes according to the load position, i.e. rail/wheel contact point. Secondly the idea above is verified by static load experiments using an actual disk type wheelset. The location of an area where lateral force affects little on surface strain is investigated, since the lateral distribution of strain should be measured in such an area to avoid the interference of bending by lateral force. And the theory for the measurement is modified for on-track testing and the best position and direction for strain gauges is proposed in accordance with the calculated and experimental results. Finally, two wheelsets for the measurement are made and field running test using this method is performed to collect data in various kind of running conditions.

VEHICLE FOLLOWING CONTROL IN LATERAL DIRECTION FOR PLATOONING

Abstract Simulation and experimental study on lateral control for autonomous driving is presented in this paper. The objective of the lateral control system is to make the controlled vehicle follow the preceding vehicle. Simulation study is conducted for investigating the relationship between information for lateral control and the tracking accuracy obtained based on the information. Simulation results of vehicle-following control based on five kinds of control algorithms, each of which is designed using some information for lateral control, are compared and discussed. Experimental study is carried out by use of two vehicles to validate results of the simulation study. By both studies, it is clarified that side slip angle is the essential information for implementing an accurate vehicle-following control.

The Application of RTK-GPS and Steer-By-Wire Technology to the Automatic Driving of Vehicles and an Evaluation of Driver Behavior

Automatic vehicle driving has long been the subject of research efforts designed to improve the safety and efficiency of automobile transportation. In recent years, increasingly sophisticated sensors and automobiles have brought automatic driving systems closer to reality. In this paper we describe an attempt to apply real-time kinematic GPS (RTK-GPS), a highly precise positioning system, and steer-by-wire body technology, which has advanced greatly in recent years, to automatic driving. In addition, we also describe the results of research into human factors related to automatic driving, which will become more and more important as automatic driving is put to practical use.(A)

DGPS-based position measurement and steering control for automatic driving

Simulation and experimental studies are carried out for investigating the possibility of automatic vehicle control system based on absolute position information. Implementation of such control system requires a methodology of measuring the absolute position, and a control algorithm. In this paper, an accurate and real-time estimation of the absolute position by use of DGPS (Differential Global Positioning System) and sensors on a controlled vehicle is proposed. A steering control algorithm for tracking the desired course stored as absolute position data is also proposed. Simulation and experimental results validates the proposed estimation and control system, and provides the perspective of enhancing the automatic driving control system by use of the absolute position information.

Driver's behavior under steering assist control system

It is proposed that a dual-port element (of electric circuit theory) be applied to describe steering assist control systems. Such a method describes not only conventional steering assist control systems but also steering-by-wire systems in the systematic method. This method is used for standardization and classification of the steering assist control systems. A steering assist control system (a quasi automatic driving system) is then proposed and scrutinized. The proposed system is a weighting method which mixes the real drivers input and a virtual drivers input. Experimental results by use of a driving simulator are discussed. It is difficult for steering assist control system experiments to be carried out on real roads, because no ITS environment has been constructed yet, so a driving simulator is utilized to realize the ITS environment and investigate a closed loop system including the driver in the environment. The problem of interference between the real driver and the controller is discussed.

GPS-BASED AUTOMATIC DRIVING CONTROL IN LOCAL AREA WITH COURSE OF LARGE CURVATURE AND PARKING SPACE

Vehicle motion control algorithms for fully automatic driving in a local area are proposed and investigated in this paper. Current automotive technologies for automatic driving have encountered the problems of system reliability, human factors and responsibility of accident. A fully automatic driving system, however, can be realized relatively easily as long as it is operated in a local area such as a campus or a site of an institute. This study is aiming at investigating human factors, system reliability and methodology of system management by operating a fully automatic driving system in the campus. In this paper, experimental studies are carried out for developing such a fully automatic driving system using a precise GPS. Two control algorithms for automatic driving in a local area is proposed. One is control algorithm for tracking a trajectory with small radius of curvature, and the other is that for automatic parking. Experimental results clarified that a controlled vehicle can track a trajectory with curvature of more than 0.2, and can accurately park in a parking space with reverse movement by the proposed control algorithms.

Comparison of Sliding and PID Control for Longitudinal Automated Platooning

This paper investigates longitudinal vehicle control for platooning. Two- car platooning is realized by controlling the throttle of the following car. A vehicle model which is used for simulation and as a control model for experiment is constructed. Comparison of sliding control and PID control is done under various conditions. It is shown that especially under large initial deviation from the target state sliding control has better stability and more rapid convergence than PID control.

Sensitivity analysis of side-slip angle observer based on a tire model

We investigated the sensitivity of an observer based on a tire model using simulation in linear and nonlinear regions. In the linear region, we investigated the influence of vehicle speed by doing the same simulation at three speed levels. In the nonlinear region, the simulation condition was set such that the vehicle became unstable. In the linear region, steering input and cornering stiffness have a relatively large effect on the estimation error because these quantities determine tire side force. In the nonlinear region, the road surface’s friction coefficient becomes a crucial factor. In both the regions, the observer is sensitive to yaw rate and longitudinal speed.

Drivers' behavior in ITS environment investigated by a driving simulator

Autonomous driving systems have been researched from various viewpoints. It is not realistic to install a complete autonomous driving system in a current situation. Therefore a switching between an autonomous driving system and a conventional driving system is required. The man-machine interface is important in this kind of hybrid system. In this study a simulator research is done under the environment of intelligent transport systems (ITS), with special emphasis on the switching system between autonomous driving and conventional driving. However, it is difficult to do this kind of study in a real traffic situation. Therefore a fixed based driving simulator is used for giving drivers the environment of ITS in near future.

Discrete Brush Tire Model for Calculating Tire Forces with Large Camber Angle

SUMMARY In this paper one-dimensional discrete brush model is described. A new model contains twisting concept along a trajectory of tread base and explains the mechanism of moment around the vertical axis at large camber angles. Calculations are focused on tires for motor-cycles, since motor-cycles often use tires under the condition of large camber angles. The calculated results are compared with the experimental results and it is shown that the proposed model can be applied to the calculation of the moment around the vertical axis at large camber angles.