Soo-Yeong Yi

Vehicle longitudinal brake control using variable parameter sliding control

Abstract A modified sliding control with variable control parameter was introduced to reduce the large change of pressure feedback in the hydraulic brake control process of automated highway vehicles. An average decay function was used to smooth both high and low frequency oscillations of the desired diaphragm force and output force in the vacuum booster to remedy the oscillations generated by using the pushrod force as the end-brake control. Simulation results indicate that the variable parameter sliding control significantly reduces the speed and space tracking errors in the large brake processes, and the errors experienced during these processes are dominated by the large brake pressure lag rather than the switching delay time between throttle and brake.

An Omnidirectional Stereo Vision System Using a Single Camera

We describe a new omnidirectional stereo imaging system that uses a concave lens and a convex mirror to produce a stereo pair of images on the sensor of a conventional camera. The light incident from a scene point is split and directed to the camera in two parts. One part reaches camera directly after reflection from the convex mirror and forms a single-viewpoint omnidirectional image. The second part is formed by passing a subbeam of the reflected light from the mirror through a concave lens and forms a displaced single viewpoint image where the disparity depends on the depth of the scene point. A closed-form expression for depth is derived. Since the optical components used are simple and commercially available, the resulting system is compact and inexpensive. This, and the simplicity of the required image processing algorithms, make the proposed system attractive for real-time applications, such as autonomous navigation and object manipulation. The experimental prototype we have built is described

Autonomous navigation of indoor mobile robots using a global ultrasonic system

Autonomous navigation of an indoor mobile robot, using the global ultrasonic system, is presented in this paper. Since the trajectory error of the dead-reckoning navigation increases significantly with time and distance, the autonomous navigation system of a mobile robot requires self-localization capability in order to compensate for trajectory error. The global ultrasonic system, consisting of four ultrasonic generators fixed at a priori known positions in the work space and two receivers mounted on the mobile robot, has a similar structure to the well-known satellite GPS(Global Positioning System), which is used for the localization of ground vehicles. The EKF (Extended Kalman Filter) algorithm is utilized for self-localization and autonomous navigation, based on the self-localization algorithm is verified by experiments performed in this study. Since the self-localization algorithm is efficient and fast, it is appropriate for an embedded controller of a mobile robot.

Global ultrasonic system with selective activation for autonomous navigation of an indoor mobile robot

This paper presents a global ultrasonic system with selective activation algorithm for autonomous navigation of an indoor mobile robot. The global ultrasonic system consists of several ultrasonic transmitters fixed at reference positions in global coordinates and two receivers at moving coordinates of a mobile robot. By activating the ultrasonic transmitters through an radiofrequency (RF) channel, the robot is able to obtain distance information to the reference positions and localize itself in the global coordinates. Due to limitations in signal strength and beam width, the ultrasonic signals from some transmitters may not be delivered to the robot and the ultrasonic data become invalid. In order to improve the effectiveness of the global ultrasonic system, a so-called selective activation algorithm is developed. Based on the current position of the robot, the selective activation calls a proper ultrasonic transmitter and generates valid ultrasonic data at every sampling instant, resulting in faster, more accurate response for self-localization than does simple sequential activation. Path-following control experiments are conducted to verify the effectiveness of the self-localization based on the proposed selective activation algorithm with the global ultrasonic system.

Reference adaptive impedance control and its application to obstacle avoidance trajectory planning

A new paradigm of event-based robotic control, called reference adaptive impedance control, is presented for partially constrained robots under uncertain or unknown environmental constraints. The reference adaptive impedance control determines the desired next state adaptively in such a way as to follow the optimal path from the current state, where the optimal path is generated with the environmental constraints updated through time. The embedded impedance control provides a mechanism for collecting more complete information on the environment. An application to obstacle avoidance trajectory planning is given with computer simulations.

Development of Embedded Lane Detection Image Processing Algorithm for Car Black Box

Abstract Car black box helps to investigate the cause of accident by recording time, position and videos as well as shock information. In addition, the car black box need a function to support safe driving for preventing accident. The representative driving support function is a lane departure warning. In order to implement the function, it is necessary to carry out the image processing to detect the lane first. The image processing algorithm requires computational burden to handle so much data and complicated structure of algorithm. This paper describes the efficient image processing algorithm with relatively low amount of computation for car black box embedded platform to detect lanes from the real-time lane image. Key Words : Car black box; Lane detection, Embedded algorithm; Hough transform * 교신저자 : 이수영(suylee@snut.ac.kr)접수일 10년 06월 24일 수정일 10년 07월 21일 게재확정일 10년 08월 10일 1. 서론 원래 블랙박스는 항공기의 비행 상태를 나타내는 각종 센서 데이터와 조종사의 음성과 같은 비행기록을 실시간으로 저장하여 항공기 사고의 원인을 규명하고 재발을 방지하기 위해 사용하는 것이다. 근래 기술의 발전으로 저가격화가 가능해지면서 버스나, 택시와 같은 차량에도 블랙박스를 장착하는 것이 가능해졌다. 그러나 근래 통상적으로 일컫는 차량용 블랙박스는 차량의 운행상태를 나타내는 다른 센서 데이터 보다는 주로 차량 전면에서의 영상만을 기록하므로 차량용 영상기록장치라는 표현이 보다 적당하다고 하겠다[1]. 향후에는 영상정보 뿐만 아니라 자동차내의 모든 운행 정보, 즉 엔진 회전수, GPS 정보 , 브레이크가속페달조향각도, ABS 작동여부 등의 신호를 실시간으로 기록하는 진정한 의미의 차량용 블랙박스가 개발될 것으로 예상된다.차량용 블랙박스는 사고순간의 영상을 기록하여 사고원인을 규명함으로써 운전자간의 시비를 가리는 중요한 증거로 사용되므로 운전자 스스로 안전운전을 유도하는 예방차원의 효과도 있다. 이에 따라 지식경제부 산하의 기술표준원에서는 최근에 차량용 블랙박스의 국가규격을 제정 , 고시하였으며 근래에는 상용차뿐만 아니라 개인승

Teleoperation of a quadruped walking robot using an aperiodic gait that converges to a periodic gait

Presents a gait control algorithm for teleoperation of a quadruped walking robot using gait convergence. A leg trajectory of the walking robot is generated in real-time according to the 3 DOF planar moving velocity command. Initially, the aperiodic gait is applied to follow the unpredictable command, since the periodic gait is known to be optimal and it requires an initial foot position. However, given an arbitrary initial foot position, the proposed algorithm leads the support pattern of the legs to converge from the aperiodic gait to a wave-crab gait or a wave-spinning gait. Further it avoids a deadlock after the directional change of the velocity command. The proposed algorithm has been applied to the walking robot, CENTAUR of KIST that has heavy legs and a large moving area of the gravity center. To compensate the moving gravity center, a sway motion is proposed to transfer the leg of which the kinematic margin is almost zero and the leg trajectory for the sway motion is overlapped with the operator command.

Development of Stable Ballbot with Omnidirectional Mobility

The ball-shaped mobile robot, so called ballbot has single point contact on ground and low energy consumption in motion because of the reduced friction. In this paper, a new ballbot is presented, which has omnidirectional mobile platform inside of it as a driving system. Thus the ballbat has omnidirectional mobility without nonholonomic constraints. Kinematics and inverse kinematics of the ballbat is derived also in this paper.The ball-shaped mobile robot, so called ballbot has single point contact on ground and low energy consumption in motion because of the reduced friction. In this paper, a new ballbot is presented, which has omnidirectional mobile platform inside of it as a driving system. Thus the ballbat has omnidirectional mobility without nonholonomic constraints. Kinematics and inverse kinematics of the ballbat is derived also in this paper.

Single Camera Omnidirectional Stereo Imaging System

A new method for the catadioptric omnidirectional stereo vision with single camera is presented in this paper. The proposed method uses a concave lens with a convex mirror. Since the optical part of the proposed method is simple and commercially available, the resultant omnidirectional stereo system becomes versatile and cost-effective. The closed-form solution for 3D distance computation is presented based on the simple optics including the reflection and the reflection of the convex mirror and the concave lens. The compactness of the system and the simplicity of the image processing make the omnidirectional stereo system appropriate for real-time applications such as autonomous navigation of a mobile robot or the object manipulation. In order to verify the feasibility of the proposed method, an experimental prototype is implemented.

Kinematic modeling of mobile robot with rocker-bogie link structure

A method for kinematic modeling of a mobile robot with rocker-bogie link mechanism was described. By using the well-known concept of the instantaneous coordinates, it derives the kinematic model for the full six degree of freedom motion including the x, y, and z motions and the pitch, roll, and yaw rotations. The kinematic model here implies both of the forward and the inverse kinematic equations. The forward kinematic equation with the wheel Jacobian matrices can be used to obtain the robot position and orientation from the measured wheel velocities and the rocker-bogie joint angles. On the contrary, the inverse kinematic equation implies a resulting robot motions consisting of body velocity and turning rate from the individual wheel velocities. Through the computer simulation, the kinematic model of the mobile robot was verified.