Woon-Sung Lee

A driving simulator as a virtual reality tool

This paper describes a driving simulator developed for design and evaluation of full-scale driving simulators and for driver-vehicle interaction study. The simulator consists of a real-time vehicle simulation system, visual and audio system, motion system, control force loading system, and experiment console. The real-time vehicle simulation system supervises the overall operation of the simulator and also simulates the dynamic motion of realistic vehicle models in real-time. The visual system generates high fidelity driving scenes that are displayed on a screen by a projector. The motion system generates realistic motion cue using a six degree-of-freedom Stewart platform driven hydraulically. The control force loading system acts as an interface between a driver and the simulator. The experiment console monitors the status of the simulator in operation and also collects and manages experimental data.

Hardware-in-the-loop Simulation for Electro-mechanical Brake

The X-by-wire technology, replacing mechanical components with electrical components, is essential to realizing an intelligent vehicle. The technology has many advantages including component reduction, design freedom increase and safety improvement. Brake-by-wire replaces hydraulic brake systems with electrical components. As a part of the X-by-wire technology, the brake-by-wire technology has been actively researched. The technology has a great advantage of solving manufacturing, maintenance and environmental problems associated with hydraulic systems. However, due to absence of mechanical or hydraulic back-up, the brake-by-wire system must be highly reliable and fault-tolerant. This requires environment in which the system can be developed and tested safely, before applying to an actual vehicle. The environment must be flexible in developing and testing various algorithms, and be faithful in reproducing the actual system. This study thus develops a brake-by-wire hardware-in-the-loop simulation system that can serve as the environment mentioned above. The electro-mechanical brake type has been adopted in this study for developing the system. A procedure to develop the system was defined and followed to design a brake actuator, select a motor, build hardware components, set up the whole system, and test for performance evaluation. A preliminary test of the developed system shows its effectiveness. However, the test also shows that the response speed of the system should improve. A follow-up study will be conducted to improve system response, develop a full-scale system, and integrate with a steer-by-wire system

A design and characteristic analysis of the motion base for vehicle driving simulator

The main procedures of development of the motion system for a vehicle driving simulator are classified in 3 parts: 1) development of the motion base system which can be generated by the motion cues; 2) the construction of a real-time vehicle software which can afford the vehicle dynamics; and 3) the integration of vehicle driving simulator, which can be interconnected between visual systems with motion base. This paper describes the motion system developed for a driving simulator, consisting of a six degree of freedom Stewart platform driven hydraulically. The hardware has been developed based on a careful consideration of the target performance, motion envelope, driving scenarios, etc. The drive logic, consisting of a washout algorithm, inverse kinematic analysis, and control algorithm, has been developed and applied for creating high fidelity motion cues.

Reliability Improvement of Global Chassis Control

Global chassis control maximizes chassis control performance by integrating and controlling individual chassis control systems in an integrated and compensatory manner. A global chassis control system thus requires high reliability, even in case of failure or fault. The system should be capable of detecting failure under various conditions, and responding to failure appropriately to guarantee uninterrupted performance. In this paper, we propose a fail-safe strategy to improve reliability of the global chassis control system. We have implemented the global chassis control system in a way that a higher-level controller monitors driver intention and vehicle status, and then commands lower-level, chassis controllers to maximize vehicle performance. Depending on failure detection types of sensors and actuators in the control system, we developed different fail-safe methods: we combined actual hardware sensors and virtual algorithm sensors appropriately depending on whether other sensor signals can be used to determine failure of the sensor or not. Simulation results demonstrate effectiveness of the fail-safe strategy and improvement of system reliability

A Symbolic computation method for automatic generation of a full vehicle model simulation code for a driving simulator

This paper deals with modeling and computer simulation of a full multibody vehicle model for a driving simulator The multibody vehicle model is based on the recursive formulation and a conespondmg simulation code is generated automatically from AUTOCODE, which is a symbolic computation package developed by the authors using MAPLE The paper describes a proceduie for automatically generating a highly efficient simulation code for the full vehicle model, while incorporating realistically modeled components The following issues have been accounted for in the procedure, including software design for representing a mechanical system in symbolic form as a set of computer data objects, a multibody formulation for systems with various types of connections between bodies, automatic manipulation of symbolic expressions in the multibody formulation, interface design for allowing users to describe unconventional forceand torque-producing components, and a method for accommodating external computer subroutines that may have already been developed The effectiveness and efficiency of the proposed method have been demonstrated by the simulation code developed and implemented for driving simulation

Development of driver-state estimation algorithm based on Hybrid Bayesian Network

In this study, we develop and evaluate an estimation algorithm of abnormal driving states (drowsiness, distraction, and workload) based on a Hybrid Bayesian Network (HBN) using multimodal information. The HBN algorithm is expected to increase transportation safety by combining merits of both the Bayesian Network and clustering algorithm. In addition, multimodal data efficacy analysis through human-in-the-loop experiments is used to enhance the performance of the driver-state estimation algorithm. Performance results obtained the lowest false alarm rate and fastest calculation speed. The false alarm rate decreased from 18.2 to 15.5%, whereas the calculation speed decreased by 4.35%.

Preliminary analysis of full-scale driving simulator data for unmasked sleepiness detection

A driver can mask his sleepiness. This study aims to determine effective and reliable indications of a drivers unmasked sleepiness using driver-vehicle data. A Bayesian approach and the signal detection theory were applied to investigate the effectiveness of selected driver-vehicle parameters for this purpose. Twenty subjects participated in three consecutive driving sessions on the simulated 4-lane highway from Seoul to Cheonan, Korea, during which their PERCLOS (percentage of eye closure) data, assumed to be a true indicator of a drivers unmasked sleepiness, i.e., drowsiness, were monitored. Correlations between PERCLOS and the selected vehicle parameters, such as velocity RMSE (root-mean-square error), were analyzed while participants performed skill-based and rule-based driving tasks. The preliminary experimental results demonstrated that unmasked sleepiness, as indicated by PERCLOS, was not correlated with the selected vehicle parameters for skill-based tasks. Some rule-based tasks, such as VPVT (Visual Psychomotor Vigilance Task), showed significant correlations with masked and unmasked sleepiness, which shows that driver-vehicle data can potentially be used as a dynamic unmasked sleepiness indicator. More in-depth analysis is being conducted and is expected to be included in the final version of the manuscript.