Sung-Kee Park

FPGA Design and Implementation of a Real-Time Stereo Vision System

Stereo vision is a well-known ranging method because it resembles the basic mechanism of the human eye. However, the computational complexity and large amount of data access make real-time processing of stereo vision challenging because of the inherent instruction cycle delay within conventional computers. In order to solve this problem, the past 20 years of research have focused on the use of dedicated hardware architecture for stereo vision. This paper proposes a fully pipelined stereo vision system providing a dense disparity image with additional sub-pixel accuracy in real-time. The entire stereo vision process, such as rectification, stereo matching, and post-processing, is realized using a single field programmable gate array (FPGA) without the necessity of any external devices. The hardware implementation is more than 230 times faster when compared to a software program operating on a conventional computer, and shows stronger performance over previous hardware-related studies.

Mobile robot navigation based on direct depth and color-based environment modeling

This paper describes a new method for indoor environment mapping and localization with stereo camera. For environmental modeling, we directly use the depth and color information in image pixels as visual features. Furthermore, only the depth and color information at horizontal centerline in image is used, where optical axis passes through. The usefulness of this method is that we can easily build a measure between modeling and sensing data only on the horizontal centerline. That is because vertical working volume between model and sensing data can be changed according to robot motion. Therefore, we can build a map about indoor environment as compact and efficient representation. Also, based on such nodes and sensing data, we suggest a method for estimating mobile robot positioning with random sampling stochastic algorithm. With basic real experiments, we show that the proposed method can be an effective visual navigation algorithm.

Human augmented mapping for indoor environments using a stereo camera

In this paper, we suggest a new method of human augmented mapping for indoor environments using only a stereo camera. Through users help, a robot with a stereo camera can investigate the environment without failure and even more efficiently. Moreover, the user can share the information about the environment with the robot and add semantic information to the environmental map. We employ PCA features for visual landmarks and a hybrid map for map representation. Particularly, we define two types of nodes, U/R-nodes and divide the map building into three processes, Users Guidance, Robots Map Revision, and Robots Map Completion. We implemented a human augmented mapping system with a stereo camera and demonstrated it in rectangular-shaped corridors. From the comparison with a manually-built map, we showed the feasibility of the environmental map generated by our proposed method.

Experimental research of navigation behavior selection using generalized stochastic Petri nets (GSPN) for a tour-guide robot

This paper proposes a formal selection framework of multiple navigation behaviors for a service robot. In our approach, modeling, analysis, and performance evaluation are carried out based on the generalized stochastic Petri nets (GSPN). By adopting probabilistic approach, our framework helps the robot to select the most desirable navigation behavior in run time according to environmental conditions. Moreover, after a mission, the robot evaluates prior navigation performance from accumulated data, and uses the results for the improvement of future operations. Also, GSPN has several advantages over classic automata or direct use of Markov process. The basic ideas of the framework were introduced in our previous work (Gunhee Kim et al., 2005). Thus, this paper focuses on experimental verification by implementing the framework into the guide robot Jinny. We conduct the experiments about real guidance tasks with visitors in the National Science Museum of Korea. The results show that the proposed strategy is useful to select an appropriate navigation behavior in a dynamic space.